CN111943153A

CN111943153A - Method and system for treating nitric acid containing high-boiling-point organic matter, and method and apparatus for producing substituted nitrobenzoic acid

Info

Publication number: CN111943153A
Application number: CN202010791594.8A
Authority: CN
Inventors: 张本松; 王勤波; 肖淑焕; 唐立星; 任苗苗; 熊振华; 焦玉坤; 孙美玲; 邹珊珊; 张海波
Original assignee: Shandong Youdao Chemical Co ltd
Current assignee: Shandong Youdao Chemical Co ltd
Priority date: 2020-08-07
Filing date: 2020-08-07
Publication date: 2020-11-17

Abstract

The invention provides a method and a system for treating nitric acid containing high-boiling point organic matters, and a method and equipment for preparing substituted nitrobenzoic acid. The processing method comprises the following steps: step S1, performing solid-liquid separation on the nitric acid containing high-boiling-point organic matters to obtain a first high-boiling-point organic matter product, waste dilute nitric acid and first smoke exhaust; step S2, pre-concentrating the waste dilute nitric acid to obtain recovered waste water, recovered dilute nitric acid and second nitric acid smoke tail gas, wherein the concentration of nitric acid in the recovered waste water is lower than that in the recovered dilute nitric acid; step S3, concentrating the recovered dilute nitric acid by a sulfuric acid method to obtain a recovered concentrated nitric acid and sulfuric acid aqueous solution; step S4, concentrating the sulfuric acid water solution to obtain waste water and crude concentrated sulfuric acid; and step S5, refining the crude concentrated sulfuric acid to obtain recovered concentrated sulfuric acid and solid waste, and returning the recovered concentrated sulfuric acid to step S3 to be used as sulfuric acid for concentrating and recovering dilute nitric acid by a sulfuric acid method. The nitric acid waste liquid can be effectively recycled.

Description

Method and system for treating nitric acid containing high-boiling-point organic matter, and method and apparatus for producing substituted nitrobenzoic acid

Technical Field

The invention relates to the technical field of nitric acid recovery, in particular to a method and a system for treating nitric acid containing high-boiling-point organic matters, and a method and equipment for preparing substituted nitrobenzoic acid.

Background

Nitration is an important unit reaction widely used in the production of chemical products such as dyes, medicines, pesticides, explosives and the like, wherein nitrate nitration is a common nitration method. In the process of nitric acid nitration reaction, a large amount of waste nitric acid saturated by organic matters is generated, if the waste nitric acid is used as three wastes for neutralization treatment, the treatment capacity of the three wastes is large, the treatment cost is high, the quality of the recovered nitrate is poor due to the existence of high-boiling-point organic matters, the nitrate cannot be effectively utilized, the resource waste is caused, the waste is increased, and the environment is secondarily polluted.

In order to improve the utilization rate of nitric acid or recovered waste nitric acid in the nitric acid nitration process and reduce the discharge of three wastes, the industry concentrates the dilute nitric acid containing high-boiling-point organic matters generated by the nitric acid nitration in a distillation mode and removes part of the organic matters so as to realize the reutilization of the nitric acid. However, when conventional distillation treatment is carried out, organic matters dissolved in nitric acid volatilize due to gas-liquid phase balance or are carried into the recovered nitric acid by steam, so that the content of the organic matters in the recovered nitric acid is high, and if the recovered nitric acid is further concentrated, potential safety hazards exist due to the fact that high-boiling-point organic matters are contained in the system; if this recovered nitric acid is used for other purposes, new organic impurities are introduced into the nitric acid for other purposes. This limits the range of application of the nitric acid recovered by conventional distillation operations, and has potential safety hazards and affects product quality. Therefore, the conventional process for distilling and concentrating the waste dilute nitric acid is difficult to realize the effective utilization of the nitric acid, thereby easily causing secondary pollution and increasing the production cost.

Chinese patent application with application publication No. CN108128826A discloses a device and a method for treating wastewater containing nitric acid, wherein m-toluic acid nitration is used as a specific example to describe the technical scheme, 98 percent nitric acid and m-toluic acid are mixed and subjected to nitration reaction, the produced nitration product is subjected to pressure filtration to obtain nitration mother liquor and nitration product with the mass concentration of the nitric acid of about 94 percent, then the nitration product is subjected to gradient washing by fresh water, washing filtrate is mixed with the nitration mother liquor to obtain 70 percent nitric acid waste liquor, then the 70 percent nitric acid waste liquor is subjected to distillation and concentration treatment, distillate is cooled by a condenser to obtain 68 percent recovered nitric acid, the concentration of the distillate is too different from the concentration of the nitric acid required by the nitration reaction of the m-toluic acid, and the distillate cannot be directly used in the nitration reaction of the m-toluic acid, this is because the recovered nitric acid still contains a large amount of organic substances, and if the content of organic substances in the recovered nitric acid is 3000ppm or more as a result of calculation by, for example, specialized chemical process simulation software (AspenPlus), it is common knowledge of those skilled in the art that the quality of the nitrated product is seriously affected if the recovered nitric acid containing such a high concentration of organic substances is directly applied to other nitration reactions as industrial nitric acid. These results in that the practical industrial application range of the recovered nitric acid recovered from the waste nitric acid containing high boiling point organic matters as described in the prior art schemes represented by the techniques disclosed in the above patent applications will be severely limited.

Nitric acid water is an azeotropic mixture, only recovered nitric acid with the azeotropic concentration not higher than that of nitric acid water can be obtained by a conventional rectification method, in order to obtain nitric acid with higher concentration and realize the recovery and the reuse of the nitric acid, a special nitric acid concentration method is required, and the current industrialized special nitric acid concentration method is a magnesium nitrate method and a sulfuric acid method, namely magnesium nitrate or sulfuric acid is used as a dehydrating agent to concentrate dilute nitric acid. When magnesium nitrate is used as a dehydrating agent to concentrate dilute nitric acid, an outlet of organic matters is difficult to set in the concentration process, so that the organic matters are continuously accumulated in the concentration process of the nitric acid, and an explosive substituted nitrobenzoic acid-magnesium nitrate system is finally generated, and huge potential safety hazards exist. Therefore, the method of concentrating nitric acid using magnesium nitrate as a dehydrating agent is only suitable for concentrating pure or dilute nitric acid containing no organic matter, and the method of concentrating dilute nitric acid containing organic impurities, i.e., sulfuric acid method, is preferably used.

The process for concentrating the nitric acid by the sulfuric acid method mainly comprises two processes of concentrating the nitric acid and concentrating the sulfuric acid, and the core process is the application of the sulfuric acid as a dehydrating agent. The traditional sulfuric acid process is Pauling process, which uses sulfuric acid of about 92% as dehydrating agent to concentrate dilute nitric acid to about 98%. Such as: chinese patent application publication No. CN1209282A discloses an improved sulfuric acid process nitric acid concentration process, wherein nitric acid with a concentration of about 45-70% is contacted with a liquid extraction medium (such as concentrated sulfuric acid) and then rectified to obtain 75-99.9% nitric acid; the application publication No. CN102530893A discloses a nitric acid extraction and concentration method, which is to concentrate dilute nitric acid with the concentration of 40-60% to 75-99%. However, these disclosed techniques are not suitable for the treatment of nitric acid containing high boiling point organic substances, because if the nitric acid to be treated contains high boiling point organic substances, the organic substances in the nitric acid are brought into the sulfuric acid in the process of concentrating the nitric acid by using the sulfuric acid as a dehydrating agent, and are accumulated continuously in the process of recycling the sulfuric acid, so that the high boiling point organic substances are easily enriched after long-term operation. When sulfuric acid dissolved with high-boiling-point organic matters is concentrated at high temperature, carbonization and coking are easy to occur to the organic matters, so that the sulfuric acid is blackened, the quality of the sulfuric acid is poor, and the sulfuric acid can not be used indiscriminately by a dehydrating agent, and the phenomenon of coking and carbonization and the like easily occur to a reboiler due to the excessively high concentration of the organic matters, so that the efficiency of the reboiler is reduced, and more seriously, potential safety hazards are brought.

Disclosure of Invention

The invention mainly aims to provide a method and a system for treating nitric acid containing high-boiling-point organic matters, and a method and equipment for preparing substituted nitrobenzoic acid, so as to solve the problem that nitric acid waste liquid containing high-boiling-point organic matters is difficult to effectively recycle in the prior art.

In order to achieve the above object, according to one aspect of the present invention, there is provided a method for treating nitric acid containing high boiling point organic matter, which is any one or more of compounds having the following general formula I,

wherein, the substituent R is methyl, carboxyl, nitryl, halogen and sulfonic group, n is 1 or 2, and m is 0 or 1;

the processing method comprises the following steps: step S1, performing solid-liquid separation on the nitric acid containing high-boiling-point organic matters to obtain a first high-boiling-point organic matter product, waste dilute nitric acid and first smoke exhaust; step S2, pre-concentrating the waste dilute nitric acid to obtain recovered waste water, recovered dilute nitric acid and second nitric acid smoke tail gas, wherein the concentration of nitric acid in the recovered waste water is lower than that in the recovered dilute nitric acid; step S3, concentrating the recovered dilute nitric acid by a sulfuric acid method to obtain recovered concentrated nitric acid, a sulfuric acid aqueous solution and a third nitric acid smoke tail gas; step S4, concentrating the sulfuric acid water solution to obtain waste water and crude concentrated sulfuric acid; and step S5, refining the crude concentrated sulfuric acid to obtain recovered concentrated sulfuric acid and solid waste, and returning the recovered concentrated sulfuric acid to step S3 to be used as sulfuric acid for concentrating and recovering dilute nitric acid by a sulfuric acid method.

Further, the step S1 includes: diluting nitric acid containing high-boiling-point organic matters to separate out the high-boiling-point organic matters to obtain a diluted nitric acid system to be treated; and (3) carrying out solid-liquid separation on the diluted nitric acid system to be treated to obtain a first high-boiling-point organic matter product, waste dilute nitric acid and a first nitric acid smoke tail gas, preferably, the concentration of nitric acid in the diluted nitric acid system to be treated is 20-55%, and preferably, the recovered waste water of the step S2 is used as at least part of diluent to dilute the nitric acid containing the high-boiling-point organic matter.

Further, the step S1 includes: carrying out first solid-liquid separation on nitric acid containing high-boiling-point organic matters to obtain a part of first high-boiling-point organic matter products, a separation mother liquor and a part of first smoke tail gas; diluting the separated mother liquor to separate out high boiling point organic matters in the separated mother liquor to obtain diluted mother liquor; and (4) carrying out solid-liquid separation on the diluted mother liquor to obtain waste dilute nitric acid, the remaining first high-boiling-point organic product and the remaining first smoke tail gas, preferably, the concentration of the nitric acid in the diluted mother liquor is 20-55%, and preferably, the separated mother liquor is diluted by adopting the recovered waste water of the step S2 as at least part of diluent.

Further, the step S2 includes: rectifying the waste dilute nitric acid by using a rectifying tower, obtaining recovered waste water at the tower top, obtaining concentrated solution at the tower bottom, obtaining recovered dilute nitric acid and second nitric acid smoke tail gas at the side line of the rectifying tower, preferably, the concentration of nitric acid in the recovered waste water is less than or equal to 5%, preferably, the concentration of nitric acid in the recovered dilute nitric acid is not higher than the azeotropic concentration of nitric acid water, and the mass content of organic matters is not higher than 0.1%, and preferably, the concentration of nitric acid in the concentrated solution is not lower than the concentration of nitric acid in the waste dilute nitric acid and is not higher than the azeotropic concentration of; and (3) diluting the concentrated solution, and then carrying out solid-liquid separation to obtain a separated solution and a second high-boiling-point organic product, preferably, the concentration of the nitric acid after the concentrated solution is diluted is not lower than 20%, preferably, the separated solution is returned to the rectification treatment step to be rectified together with the waste dilute nitric acid, preferably, the recovered waste water is used as at least part of diluent to dilute the concentrated solution, or the concentrated solution is returned to the step S1 to carry out solid-liquid separation.

Further, the step S2 includes: distilling the waste dilute nitric acid to obtain recovered waste water at the tower top and dilute nitric acid at the tower bottom, wherein the concentration of nitric acid in the recovered waste water is preferably less than or equal to 5 percent, and the concentration of nitric acid in the dilute nitric acid is not lower than that of nitric acid in the waste dilute nitric acid and not higher than the azeotropic concentration of nitric acid water; rectifying the dilute nitric acid to obtain recovered dilute nitric acid and second nitric acid smoke tail gas at the tower top, and obtaining a concentrated solution at the tower bottom, wherein the concentration of nitric acid in the recovered dilute nitric acid is preferably not higher than the azeotropic concentration of nitric acid water, and the mass content of organic matters is preferably not higher than 0.1%, and the concentration of nitric acid in the concentrated solution is preferably not lower than the concentration of nitric acid in the waste dilute nitric acid and not higher than the azeotropic concentration of the nitric acid water; and (3) diluting the concentrated solution, and performing solid-liquid separation to obtain a separated solution and a second high-boiling-point organic product, wherein the concentration of the nitric acid after the concentrated solution is diluted is preferably not lower than 20%, the separated solution is preferably returned to the distillation treatment step to be subjected to distillation treatment together with the waste dilute nitric acid, the recovered wastewater is preferably used as at least part of diluent to perform dilution treatment on the concentrated solution, or the concentrated solution is returned to the step S1 to perform solid-liquid separation.

Further, the step S2 includes: distilling the waste dilute nitric acid by using a distillation tower, obtaining recovered waste water at the tower top, obtaining concentrated solution at the tower bottom, obtaining heavy components at the side line of the distillation tower, preferably, the concentration of nitric acid in the recovered waste water is less than or equal to 5%, and the concentration of nitric acid in the concentrated solution is not lower than that of the waste dilute nitric acid and is not higher than the azeotropic concentration of the nitric acid; rectifying the heavy components by using a rectifying tower, obtaining recovered dilute nitric acid and second nitric acid smoke tail gas at the tower top, obtaining dilute nitric acid at the tower bottom, preferably, the concentration of nitric acid in the recovered dilute nitric acid is not higher than the azeotropic concentration of nitric acid water, the mass content of organic matters is not higher than 0.1%, preferably, the concentration of nitric acid in the dilute nitric acid is not lower than the concentration of nitric acid in a concentrated solution and is not higher than the azeotropic concentration of the nitric acid water, and preferably, returning the dilute nitric acid to the distillation treatment to carry out distillation treatment together with the waste dilute nitric acid; and (3) diluting the concentrated solution, and performing solid-liquid separation to obtain a separated solution and a second high-boiling-point organic product, wherein the concentration of the nitric acid after the concentrated solution is diluted is preferably not lower than 20%, the separated solution is preferably returned to the distillation treatment step to be subjected to distillation treatment together with the waste dilute nitric acid, the recovered wastewater is preferably used as at least part of diluent to perform dilution treatment on the concentrated solution, or the concentrated solution is returned to the step S1 to perform solid-liquid separation.

Further, in the step S3, the fresh concentrated sulfuric acid and the recovered concentrated sulfuric acid are used together as an extraction medium to concentrate the recovered dilute nitric acid to obtain the recovered concentrated nitric acid, a sulfuric acid aqueous solution and a third flue gas, preferably, the concentration of the fresh concentrated sulfuric acid is 80-98%, preferably, the mass ratio of the extraction medium to the recovered dilute nitric acid is 1.5-4: 1, preferably, the concentration of the recovered concentrated nitric acid is not lower than 80%, and preferably, the concentration of the sulfuric acid aqueous solution is 70-80%.

Further, the treatment method further comprises the step of bleaching the recovered concentrated nitric acid to obtain bleached concentrated nitric acid and fourth smoke tail gas.

Further, the treatment method further comprises a step of performing absorption treatment on the first nitrate smoke tail gas, the second nitrate smoke tail gas, the third nitrate smoke tail gas and the fourth nitrate smoke tail gas to obtain a nitrate smoke absorption liquid and waste gas, preferably, at least part of the wastewater of the step S4 is used as at least part of the absorbent to perform absorption treatment, and preferably, the concentration of nitric acid in the nitrate smoke absorption liquid is 10-40%.

Further, the mass percentage concentration of the sulfuric acid in the wastewater is not higher than 2%, the mass percentage concentration of the sulfuric acid in the crude concentrated sulfuric acid is 80-96%, and preferably, the step S5 includes: condensing the crude concentrated sulfuric acid to 60-90 ℃, and crystallizing to separate out an organic solid to obtain a condensation system; and carrying out solid-liquid separation on the condensation system to obtain recovered concentrated sulfuric acid and solid waste.

According to another aspect of the present invention, there is provided a process for preparing a substituted nitrobenzoic acid, which comprises: mixing substituted benzoic acid and concentrated nitric acid, and carrying out nitration reaction to obtain nitration reaction liquid and smoke tail gas, wherein the nitration reaction liquid has high boiling point organic matters shown in a general formula I, the nitric acid concentration of the concentrated nitric acid is not lower than 80%, and the substituted benzoic acid has a structure shown in a general formula II:

wherein, the substituent R is methyl, carboxyl, nitryl, halogen and sulfonic group, m is 0 or 1,

the nitration reaction liquid is treated by any one of the above-mentioned treatment methods.

Further, the concentrated nitric acid for nitration reaction is from the recovered concentrated nitric acid and/or fresh concentrated nitric acid obtained in the treatment method, or the treatment method further comprises bleaching the recovered concentrated nitric acid to obtain bleached concentrated nitric acid and fourth nitric acid smoke tail gas, and the concentrated nitric acid for nitration reaction is from the bleached concentrated nitric acid and/or fresh concentrated nitric acid obtained in the treatment method.

Further, the feeding mass ratio of the concentrated nitric acid to the substituted benzoic acid is 2-5: 1, and the reaction temperature is-30-60 ℃.

According to still another aspect of the present invention, there is provided a nitric acid treatment system for high boiling point organic matter, which is any one or more of compounds having the following general formula I,

the processing system comprises: the solid-liquid separation unit is used for carrying out solid-liquid separation on the nitric acid containing the high-boiling-point organic matters to obtain a first high-boiling-point organic matter product, waste dilute nitric acid and first nitric acid smoke tail gas, and is provided with a nitric acid inlet to be treated, a waste dilute nitric acid outlet and a first nitric acid smoke tail gas outlet; the nitric acid pre-concentration unit is used for pre-concentrating the waste dilute nitric acid and is provided with a waste dilute nitric acid inlet, a recycled dilute nitric acid outlet, a recycled wastewater outlet and a second nitric acid smoke tail gas outlet, and the waste dilute nitric acid inlet is connected with the waste dilute nitric acid outlet; the sulfuric acid method nitric acid concentration unit is used for concentrating the recovered dilute nitric acid by adopting a sulfuric acid method, and is provided with a concentrated sulfuric acid inlet, a recovered dilute nitric acid inlet, a recovered concentrated nitric acid outlet, a sulfuric acid aqueous solution outlet and a third nitric acid smoke tail gas outlet, wherein the recovered dilute nitric acid inlet is connected with the recovered dilute nitric acid outlet; the sulfuric acid concentration unit is used for concentrating a sulfuric acid aqueous solution and is provided with a sulfuric acid aqueous solution inlet, a waste water outlet and a crude concentrated sulfuric acid outlet, and the sulfuric acid aqueous solution inlet is connected with the sulfuric acid method nitric acid concentration unit connected with the sulfuric acid aqueous solution outlet; and a sulfuric acid refining unit for refining the crude concentrated sulfuric acid, wherein the sulfuric acid refining unit is provided with a crude concentrated sulfuric acid inlet, a recovered concentrated sulfuric acid outlet and a solid waste outlet, the crude concentrated sulfuric acid inlet is connected with the crude concentrated sulfuric acid outlet, and the recovered concentrated sulfuric acid outlet is connected with the concentrated sulfuric acid inlet so as to convey the recovered concentrated sulfuric acid to the sulfuric acid method nitric acid concentration unit.

Further, the solid-liquid separation unit includes: a first dilution unit having a first diluent inlet and a post-dilution system outlet; the first solid-liquid separation device is provided with a to-be-separated system inlet, a waste dilute nitric acid outlet and a first nitric acid smoke tail gas outlet, the diluted system outlet is connected with the to-be-separated system inlet, and the preferable recycled wastewater outlet is connected with the first diluent inlet.

Further, the solid-liquid separation unit includes: the second solid-liquid separation device is provided with a separation mother liquid outlet and a first smoke tail gas outlet A; the second diluting device is provided with a second diluent inlet, a separated mother liquid inlet and a diluted mother liquid outlet, and the separated mother liquid inlet is connected with the separated mother liquid outlet; and the third solid-liquid separation device is provided with a mother liquor inlet to be separated, a waste dilute nitric acid outlet and a first nitric acid smoke tail gas outlet B, the diluted mother liquor outlet is connected with the mother liquor inlet to be separated, and the preferable recycled wastewater outlet is connected with the second diluent inlet.

Further, the nitric acid preconcentration unit includes: the first rectifying tower is provided with a waste dilute nitric acid inlet, a recovered dilute nitric acid outlet and a second nitric acid smoke tail gas outlet, the tower top is provided with a recovered waste water outlet, and the tower bottom is provided with a concentrated solution outlet; the concentrated solution outlet is connected with the nitric acid inlet to be treated, or the nitric acid pre-concentration unit further comprises: the third diluting device is provided with a concentrated solution inlet, a third diluent inlet and a diluted concentrated solution outlet, and the concentrated solution inlet is connected with the concentrated solution outlet; and the fourth solid-liquid separation device is provided with a concentrated solution inlet to be separated and a separated solution outlet, the concentrated solution inlet to be separated is connected with the concentrated solution outlet after dilution, the preferred separated solution outlet is connected with the waste dilute nitric acid inlet, and the preferred recycled wastewater outlet is connected with the third diluent inlet.

Further, the nitric acid preconcentration unit includes: the first distillation tower is provided with a waste dilute nitric acid inlet, the top of the tower is provided with a recycled wastewater outlet, and the bottom of the tower is provided with a dilute nitric acid outlet; the top of the second rectifying tower is provided with a dilute nitric acid recovery outlet and a second nitric acid smoke tail gas outlet, and the bottom of the second rectifying tower is provided with a concentrated solution outlet; the concentrated solution outlet is connected with the nitric acid inlet to be treated, or the nitric acid pre-concentration unit further comprises: the third diluting device is provided with a concentrated solution inlet, a third diluent inlet and a diluted concentrated solution outlet, and the concentrated solution inlet is connected with the concentrated solution outlet; and the fourth solid-liquid separation device is provided with a concentrated solution inlet to be separated and a separated solution outlet, the concentrated solution inlet to be separated is connected with the concentrated solution outlet after dilution, the preferred separated solution outlet is connected with the waste dilute nitric acid inlet, and the preferred recycled wastewater outlet is connected with the third diluent inlet.

Further, the nitric acid preconcentration unit includes: the second distillation tower is provided with a waste dilute nitric acid inlet and a heavy component outlet, the tower top is provided with a recycled waste water outlet, and the tower bottom is provided with a concentrated solution outlet; the top of the third rectifying tower is provided with a recovered dilute nitric acid outlet and a second nitric acid smoke tail gas outlet, the bottom of the third rectifying tower is provided with a dilute nitric acid outlet, and the preferred dilute nitric acid outlet is connected with a waste dilute nitric acid inlet; the concentrated solution outlet is connected with the nitric acid inlet to be treated, or the nitric acid pre-concentration unit further comprises: the third diluting device is provided with a concentrated solution inlet, a third diluent inlet and a diluted concentrated solution outlet, and the concentrated solution inlet is connected with the concentrated solution outlet; and the fourth solid-liquid separation device is provided with a concentrated solution inlet to be separated and a separated solution outlet, the concentrated solution inlet to be separated is connected with the concentrated solution outlet after dilution, the preferred separated solution outlet is connected with the waste dilute nitric acid inlet, and the preferred recycled wastewater outlet is connected with the third diluent inlet.

Further, the sulfuric acid process nitric acid concentration unit comprises: the concentration device is provided with a concentrated sulfuric acid inlet, a dilute nitric acid recovery inlet, a concentrated nitric acid recovery outlet, a sulfuric acid aqueous solution outlet and a third nitric acid smoke tail gas outlet; the fresh concentrated sulfuric acid supply device is connected with the concentrated sulfuric acid inlet.

Further, the treatment system further comprises a bleaching unit, wherein the bleaching unit is connected with the recovered concentrated nitric acid outlet and is used for bleaching the recovered concentrated nitric acid obtained by the sulfuric acid method nitric acid concentration unit to obtain bleached concentrated nitric acid and fourth nitric acid smoke tail gas.

Further, the bleaching unit is provided with a fourth nitrate tail gas outlet, the treatment system further comprises a nitrate tail gas absorption unit, the nitrate tail gas absorption unit is provided with an absorbent inlet and a nitrate tail gas inlet, the first nitrate tail gas outlet, the second nitrate tail gas outlet, the third nitrate tail gas outlet and the fourth nitrate tail gas outlet are all connected with the nitrate tail gas inlet, and the preferable wastewater outlet is connected with the absorbent inlet.

Further, the sulfuric acid refining unit includes: the condensing device is provided with a crude concentrated sulfuric acid inlet and a condensing system outlet; and the fifth solid-liquid separation device is provided with a condensation system inlet and a concentrated sulfuric acid recovery outlet, and the condensation system inlet is connected with the condensation system outlet.

According to still another aspect of the present invention, there is provided an apparatus for preparing a substituted nitrobenzoic acid, the apparatus comprising: the nitration reaction system is used for carrying out nitration reaction after the substituted benzoic acid and the concentrated nitric acid are mixed to obtain nitration reaction liquid and smoke tail gas, and is provided with a nitration reaction liquid outlet, the nitration reaction liquid has high boiling point organic matters shown in a general formula I, the nitric acid concentration of the concentrated nitric acid is not lower than 80%, and the substituted benzoic acid has a structure shown in a general formula II:

the nitration reaction liquid treatment system is any one of the treatment systems, and the nitration reaction liquid outlet is connected with a nitric acid inlet to be treated of the treatment system.

Further, the nitration reaction system comprises a reaction unit and a concentrated nitric acid supply unit, wherein the reaction unit is provided with a concentrated nitric acid inlet and a nitration reaction liquid outlet, the concentrated nitric acid supply unit is provided with a concentrated nitric acid outlet, a fresh concentrated nitric acid inlet and a second concentrated nitric acid inlet, the concentrated nitric acid inlet is connected with the concentrated nitric acid outlet, the second concentrated nitric acid inlet is connected with a recovered concentrated nitric acid outlet of the nitration reaction liquid treatment system, or the treatment system further comprises a bleaching unit, the bleaching unit is connected with the recovered concentrated nitric acid outlet and used for bleaching the recovered concentrated nitric acid obtained by the sulfuric acid method nitric acid concentration unit to obtain bleached concentrated nitric acid and fourth nitric acid smoke tail gas, the bleaching unit is provided with a bleached concentrated nitric acid outlet, and the bleached concentrated nitric acid outlet is connected with the second concentrated nitric acid inlet.

By applying the technical scheme, the treatment method provided by the invention has the advantages that the organic matter separation and pre-concentration are carried out on the nitric acid containing high-boiling-point organic matter, the recovered dilute nitric acid which can be concentrated by adopting a sulfuric acid extraction method is obtained, the recovered concentrated nitric acid with the nitric acid concentration higher than the azeotropic concentration of nitric acid water can be obtained in the nitric acid concentration stage, the zero emission of the waste nitric acid is realized, and the problems of safety, environmental protection and cost caused by the treatment of the waste nitric acid are avoided. Furthermore, the higher the content of organic, in particular nitro compounds in nitric acid or sulfuric acid during the distillation or rectification operation, the more dangerous the operation is, according to the general knowledge of the person skilled in the art. According to the method, firstly, the waste dilute nitric acid containing high-boiling-point organic matters is diluted to a lower concentration, most of the organic matters are separated in a solid-liquid separation mode, more organic matters are prevented from entering a concentration stage, and the safety of the concentration stage is preliminarily ensured; then, a pre-concentration process is set before sulfuric acid participates in nitric acid concentration, so that the content of organic matters in waste dilute nitric acid is greatly reduced while nitric acid pre-concentration is realized, the energy-saving effect is achieved, and meanwhile, the safety of a concentration stage is further ensured; the sulfuric acid refining process is set in the process of mechanically applying sulfuric acid, so that organic solid impurities separated out in the sulfuric acid concentration process are removed, the enrichment of the organic solid impurities and the carbonization and coking of organic matters in the sulfuric acid concentration process are avoided, the quality and the utilization rate of the sulfuric acid are ensured, and the safety of the concentration stage is further ensured. Through the synergistic effect of the processes, the recovered concentrated nitric acid and the recovered concentrated sulfuric acid obtained by the treatment method meet the recycling requirement.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic flow diagram illustrating a method for treating nitric acid containing high boiling point organic compounds according to one embodiment of the present invention;

FIG. 2 is a schematic flow diagram illustrating a nitric acid preconcentration process for nitric acid treatment of high boiling point organics, according to one embodiment of the present invention;

FIG. 3 is a schematic flow diagram illustrating a nitric acid preconcentration process for nitric acid treatment of high boiling point organics, according to another embodiment of the present invention;

FIG. 4 shows a schematic flow diagram of the nitric acid preconcentration process for nitric acid containing high boiling point organics, according to yet another embodiment of the present invention;

FIG. 5 shows a schematic flow diagram of a process for preparing substituted nitrobenzoic acids according to one embodiment of the present invention;

FIG. 6 is a block diagram illustrating a nitric acid treatment system for high boiling point organic compounds according to an embodiment of the present invention;

FIG. 7 shows a block diagram of a nitric acid preconcentration unit of a nitric acid treatment system for high-boiling organic compounds according to an embodiment of the present invention;

fig. 8 is a block diagram showing a configuration of a nitric acid preconcentration unit of a nitric acid treatment system for high-boiling-point organic substances according to another embodiment of the present invention;

fig. 9 is a block diagram showing a configuration of a nitric acid preconcentration unit of a nitric acid treatment system for high-boiling-point organic substances according to still another embodiment of the present invention; and

fig. 10 is a block diagram illustrating an apparatus for preparing substituted nitrobenzoic acids according to an embodiment of the present invention.

Wherein the figures include the following reference numerals:

10. a solid-liquid separation unit; 20. a nitric acid preconcentration unit; 30. a sulfuric acid method nitric acid concentration unit; 40. a sulfuric acid concentration unit; 50. a sulfuric acid refining unit; 21. a first rectification column; 22. a third dilution device; 23. a fourth solid-liquid separation device; 24. a first distillation column; 25. a second rectification column; 26. a second distillation column; 27. a third rectifying column; 01. a nitration reaction system.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

In the present invention, it should be noted that, unless explicitly stated or limited, the connection mode between the units should be understood in a broad sense, for example, it may be a direct pipe connection, a pipe connection connected with a pipe valve, an indirect connection through an intermediate medium, a fixed connection, or a detachable connection. The specific meaning of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

The concentration of the nitric acid in the invention refers to mass concentration, and the concentration of the nitric acid refers to the mass percentage of the nitric acid in the total mass of the nitric acid and the water. The azeotropic concentration of nitric acid in the present invention means a mass percentage of nitric acid to the total mass of nitric acid and water when nitric acid and water are azeotropic under normal pressure, reduced pressure or increased pressure, for example, the azeotropic concentration of nitric acid and water under normal pressure is 68.4%. The boiling point of the high-boiling point organic matter is more than or equal to 240 ℃. The various components of the production unit of the present invention, such as distillation columns, rectification columns, solid-liquid separation devices, and the like, are commercially available, but the processing system is not commercially available, nor is it known to those skilled in the art.

As analyzed by the background art of the present application, the process of the prior art is adopted, the waste nitric acid liquid containing high-boiling point organic matters is difficult to be effectively recycled, and in order to solve the problem, the present application provides a method and a system for treating nitric acid containing high-boiling point organic matters, and a method and a device for preparing substituted nitrobenzoic acid.

In one exemplary embodiment of the present application, a method for treating nitric acid containing high boiling point organic matter, which is any one or more of compounds having the following general formula I,

wherein, the substituent R is methyl, carboxyl, nitryl, halogen and sulfonic group, n is 1 or 2, and m is 0 or 1; as shown in fig. 1, the processing method includes: step S1, performing solid-liquid separation on the nitric acid containing high-boiling-point organic matters to obtain a first high-boiling-point organic matter product, waste dilute nitric acid and first smoke exhaust; step S2, pre-concentrating the waste dilute nitric acid to obtain recovered waste water, recovered dilute nitric acid and second nitric acid smoke tail gas, wherein the concentration of nitric acid in the recovered waste water is lower than that in the recovered dilute nitric acid; step S3, concentrating the recovered dilute nitric acid by a sulfuric acid method to obtain recovered concentrated nitric acid, a sulfuric acid aqueous solution and a third nitric acid smoke tail gas; step S4, concentrating the sulfuric acid water solution to obtain waste water and crude concentrated sulfuric acid; and step S5, refining the crude concentrated sulfuric acid to obtain recovered concentrated sulfuric acid and solid waste, and returning the recovered concentrated sulfuric acid to step S3 to be used as sulfuric acid for concentrating and recovering dilute nitric acid by a sulfuric acid method.

According to the treatment method, organic matter separation and preconcentration are carried out on the nitric acid containing high-boiling point organic matter, the recovered dilute nitric acid capable of being concentrated by adopting a sulfuric acid extraction method is obtained, the recovered concentrated nitric acid with the nitric acid concentration higher than the azeotropic concentration of nitric acid water can be obtained in the nitric acid concentration stage, zero emission of the waste nitric acid is realized, and the problems of safety, environmental protection and cost caused by treatment of the waste nitric acid are solved. Furthermore, the higher the content of organic, in particular nitro compounds in nitric acid or sulfuric acid during the distillation or rectification operation, the more dangerous the operation is, according to the general knowledge of the person skilled in the art. According to the method, firstly, the waste dilute nitric acid containing high-boiling-point organic matters is diluted to a lower concentration, most of the organic matters are separated in a solid-liquid separation mode, more organic matters are prevented from entering a concentration stage, and the safety of the concentration stage is preliminarily ensured; then, a pre-concentration process is set before sulfuric acid participates in nitric acid concentration, so that the content of organic matters in waste dilute nitric acid is greatly reduced while nitric acid pre-concentration is realized, the energy-saving effect is achieved, and meanwhile, the safety of a concentration stage is further ensured; the sulfuric acid refining process is set in the process of mechanically applying sulfuric acid, so that organic solid impurities separated out in the sulfuric acid concentration process are removed, the enrichment of the organic solid impurities and the carbonization and coking of organic matters in the sulfuric acid concentration process are avoided, the quality and the utilization rate of the sulfuric acid are ensured, and the safety of the concentration stage is further ensured. Through the synergistic effect of the processes, the recovered concentrated nitric acid and the recovered concentrated sulfuric acid obtained by the treatment method meet the recycling requirement.

The solid-liquid separation process of step S1 can be implemented in various ways, and in one embodiment, step S1 includes: diluting nitric acid containing high-boiling-point organic matters to separate out the high-boiling-point organic matters to obtain a diluted nitric acid system to be treated; and carrying out solid-liquid separation on the diluted nitric acid system to be treated to obtain a first high-boiling-point organic product, waste dilute nitric acid and first nitric acid smoke tail gas.

In another embodiment, the step S1 includes: carrying out first solid-liquid separation on nitric acid containing high-boiling-point organic matters to obtain a part of first high-boiling-point organic matter products, a separation mother liquor and a part of first smoke tail gas; diluting the separated mother liquor to separate out high boiling point organic matters in the separated mother liquor to obtain diluted mother liquor; and carrying out solid-liquid separation on the diluted mother liquor to obtain waste dilute nitric acid, the remaining first high-boiling-point organic product and the remaining first smoke tail gas. It should be clear to those skilled in the art that the compositions of the first high boiling point organic products obtained by the two solid-liquid separations may be the same or different, and specifically, the two parts of the first high boiling point organic products may vary according to the types of organic matters in the nitric acid to be treated, for example, when the organic matters in the nitric acid to be treated are one kind of organic matters, the two parts of the first high boiling point organic products are the same; when the organic matters in the nitric acid to be treated are various organic matters with different solubilities in the nitric acid, the first high-boiling-point organic products of the two parts are different.

The high boiling point organic matters have certain solubility in the nitric acid aqueous solution, and in most cases, the higher the nitric acid concentration is, the higher the solubility of the high boiling point organic products in the nitric acid waste liquid is. In order to reduce the concentration of organic matters in the nitric acid in the subsequent rectification process and reduce the safety risk in the subsequent operation process, it is necessary to reduce the content of the organic matters in the nitric acid as much as possible. This requires that the nitric acid containing high-boiling organic substances to be treated be diluted directly or after first being subjected to solid-liquid separation, in order to reduce the solubility of the organic products in the nitric acid, so that the high-boiling organic products are precipitated as solid as possible. If the dilution degree is too high, if the mass concentration of the nitric acid in the diluted nitric acid is lower than 20%, the content of organic products in the nitric acid containing high-boiling-point organic matters is greatly reduced, more organic products can be directly separated, and the yield of the high-boiling-point organic matters is improved. If the dilution degree is too low, if the mass concentration of the diluted nitric acid waste liquid is higher than 55%, more organic matters are still dissolved in the nitric acid, the height and reflux ratio of a rectifying tower in the subsequent nitric acid concentration process can be greatly increased, the energy consumption is further increased, the cost is increased, and higher potential safety hazards exist when the nitric acid containing more organic matters, particularly nitro compounds, is rectified. On the basis of a large number of experiments, the concentration of nitric acid in a diluted nitric acid system to be treated is preferably 20-55%, or the concentration of nitric acid in a diluted mother solution is preferably 20-55%, so that high-boiling-point organic matters can be fully separated at low energy consumption and low cost.

In order to reduce the wastewater discharge, it is preferable to dilute nitric acid containing high-boiling point organic substances using the recovered wastewater of step S2 as at least a part of the diluent. Or preferably, the separated mother liquor is subjected to a dilution treatment using the recovered waste water of step S2 as at least a part of the diluent. When the above-mentioned recovered waste water is insufficient, it is supplemented with fresh water.

The first high-boiling-point organic product separated in step S1 may be a mixture product containing organic substances of various structures, or may be an organic product of a single structure, and may be further refined conventionally to obtain a high-purity organic product, and the separated liquid, i.e., the waste dilute nitric acid, is then fed into the nitric acid preconcentration stage.

The nitric acid preconcentration has the function of preconcentrating the waste dilute nitric acid, greatly reduces the content of organic matters in the waste dilute nitric acid, and further reduces the safety risk in the subsequent operation process. In order to obtain the recovered nitric acid with the concentration higher than the azeotropic concentration of the nitric acid water and avoid the waste of the nitric acid, the waste dilute nitric acid needs to be concentrated. The concentration of useless thin nitric acid is on the low side and contains more organic matter, when directly adding sulphuric acid as the dehydrating agent and concentrating, the high water content in the tower cauldron sulphuric acid aqueous solution after can making the concentration on the one hand, increases subsequent sulphuric acid water's separation energy consumption by a wide margin, and the existence of more organic matter makes concentrated process have great safety risk in the useless thin nitric acid of on the other hand, and consequently this useless thin nitric acid can not directly be concentrated through sulphuric acid extraction. A large number of experimental researches of the inventor show that the effect of reducing energy consumption and improving safety can be achieved by additionally arranging a preconcentration link before concentrating the waste dilute nitric acid.

There are various ways to implement the step S2 of pre-concentrating the waste dilute nitric acid, and in an embodiment, as shown in fig. 2, the step S2 includes: rectifying the waste dilute nitric acid by using a rectifying tower, obtaining recovered waste water at the tower top, obtaining concentrated solution at the tower bottom, obtaining recovered dilute nitric acid and second nitric acid smoke tail gas at the side line of the rectifying tower, preferably, the concentration of nitric acid in the recovered waste water is less than or equal to 5%, preferably, the concentration of nitric acid in the recovered dilute nitric acid is not higher than the azeotropic concentration of nitric acid water, and the mass content of organic matters is not higher than 0.1%, and preferably, the concentration of nitric acid in the concentrated solution is not lower than the concentration of nitric acid in the waste dilute nitric acid and is not higher than the azeotropic concentration of; and (3) diluting the concentrated solution, and then carrying out solid-liquid separation to obtain a separated solution and a second high-boiling-point organic product, preferably, the concentration of the nitric acid after the concentrated solution is diluted is not lower than 20%, preferably, the separated solution is returned to the rectification treatment step to be rectified together with the waste dilute nitric acid, preferably, the recovered waste water is used as at least part of diluent to dilute the concentrated solution, or the concentrated solution is returned to the step S1 to carry out solid-liquid separation. The recovered waste water may be partially used for subsequent dilution of the concentrated solution, and the rest of the recovered waste water may be recycled to step S1 to be used as a diluent.

In another embodiment, as shown in fig. 3, the step S2 includes: distilling the waste dilute nitric acid to obtain recovered waste water at the tower top and dilute nitric acid at the tower bottom, wherein the concentration of nitric acid in the recovered waste water is preferably less than or equal to 5 percent, and the concentration of nitric acid in the dilute nitric acid is not lower than that of nitric acid in the waste dilute nitric acid and not higher than the azeotropic concentration of nitric acid water; rectifying the dilute nitric acid to obtain recovered dilute nitric acid and second nitric acid smoke tail gas at the tower top, and obtaining a concentrated solution at the tower bottom, wherein the concentration of nitric acid in the recovered dilute nitric acid is preferably not higher than the azeotropic concentration of nitric acid water, and the mass content of organic matters is preferably not higher than 0.1%, and the concentration of nitric acid in the concentrated solution is preferably not lower than the concentration of nitric acid in the waste dilute nitric acid and not higher than the azeotropic concentration of the nitric acid water; and (3) diluting the concentrated solution, and performing solid-liquid separation to obtain a separated solution and a second high-boiling-point organic product, wherein the concentration of the nitric acid after the concentrated solution is diluted is preferably not lower than 20%, the separated solution is preferably returned to the distillation treatment step to be subjected to distillation treatment together with the waste dilute nitric acid, the recovered wastewater is preferably used as at least part of diluent to perform dilution treatment on the concentrated solution, or the concentrated solution is returned to the step S1 to perform solid-liquid separation.

In other embodiments, as shown in fig. 4, the step S2 includes: distilling the waste dilute nitric acid by using a distillation tower, obtaining recovered waste water at the tower top, obtaining concentrated solution at the tower bottom, obtaining heavy components at the side line of the distillation tower, preferably, the concentration of nitric acid in the recovered waste water is less than or equal to 5%, and the concentration of nitric acid in the concentrated solution is not lower than that of the waste dilute nitric acid and is not higher than the azeotropic concentration of the nitric acid; rectifying the heavy components by using a rectifying tower, obtaining recovered dilute nitric acid and second nitric acid smoke tail gas at the tower top, obtaining dilute nitric acid at the tower bottom, preferably, the concentration of nitric acid in the recovered dilute nitric acid is not higher than the azeotropic concentration of nitric acid water, the mass content of organic matters is not higher than 0.1%, preferably, the concentration of nitric acid in the dilute nitric acid is not lower than the concentration of nitric acid in a concentrated solution and is not higher than the azeotropic concentration of the nitric acid water, and preferably, returning the dilute nitric acid to the distillation treatment to carry out distillation treatment together with the waste dilute nitric acid; and (3) diluting the concentrated solution, and performing solid-liquid separation to obtain a separated solution and a second high-boiling-point organic product, wherein the concentration of the nitric acid after the concentrated solution is diluted is preferably not lower than 20%, the separated solution is preferably returned to the distillation treatment step to be subjected to distillation treatment together with the waste dilute nitric acid, the recovered wastewater is preferably used as at least part of diluent to perform dilution treatment on the concentrated solution, or the concentrated solution is returned to the step S1 to perform solid-liquid separation.

Through the pre-concentration treatment of the waste dilute nitric acid, the recovered wastewater with the nitric acid content not higher than 5% is preferably obtained, part of the recovered wastewater can be used for the dilution and filtration operation of the tower bottom liquid, and the rest of the recovered wastewater is recycled to the solid-liquid separation step of the step S1 for recycling, or is fully recycled to the solid-liquid separation step for recycling. If the content of the nitric acid in the recovered wastewater is higher than 5%, the energy consumption is correspondingly reduced, but the treatment load of the pre-concentration system is increased, and if the content of the nitric acid in the recovered wastewater is not higher than 5%, although the energy consumption is improved, the treatment load of the pre-concentration system is not increased, so that through research, the concentration of the nitric acid in the recovered wastewater obtained in the pre-concentration stage of the waste dilute nitric acid is not higher than 5%.

Through the pre-concentration treatment of the waste dilute nitric acid, the concentration of the nitric acid in the obtained concentrated solution or dilute nitric acid is improved compared with that of the nitric acid in the waste dilute nitric acid, but is not higher than the azeotropic composition of the nitric acid. If the concentration of the nitric acid in the concentrated solution is improved by a smaller extent than that of the nitric acid in the waste dilute nitric acid, the implementation of the method is not influenced, but the concentration of the finally obtained recovered dilute nitric acid is lower, so that the energy consumption of a subsequent nitric acid concentration and sulfuric acid concentration system is increased. Preferably, from the viewpoint of energy saving, it is preferable that the concentration of nitric acid in the concentrated solution is suggested to be higher (preferably by at least 10%) than the concentration of nitric acid in the waste dilute nitric acid and not higher than the azeotropic concentration of nitric acid water, or that the concentration of nitric acid in the dilute nitric acid is suggested to be higher (preferably by at least 10%) than the concentration of nitric acid in the concentrated solution and not higher than the azeotropic concentration of nitric acid water.

And (3) after the waste dilute nitric acid is rectified, obtaining a concentrated solution, diluting the concentrated solution by using recovered waste water and/or fresh water until the mass concentration of the nitric acid is not lower than 20%, carrying out solid-liquid separation to obtain a separation solution and a second high-boiling-point organic product, and mixing the separation solution with the waste dilute nitric acid and then feeding the mixture into a rectifying tower for rectification. If the dilution degree is too high, the mass concentration of the nitric acid is less than 20%, and although the organic matter in the separated liquid is greatly reduced, the treatment amount of the pre-concentration treatment step is increased, and the energy consumption is increased, so that the solid-liquid separation is preferably performed after the concentrated liquid is diluted to the mass concentration of the nitric acid of not less than 20%.

After the waste dilute nitric acid is subjected to pre-concentration treatment, organic matters dissolved in the recovered dilute nitric acid can be greatly reduced. Through a large number of experiments, the following results are found: the mass content of the organic matters in the recovered dilute nitric acid is higher than 0.1%, and the organic matters substituted nitrobenzoic acid can be accumulated to a higher concentration in the subsequent concentration process, so that the safety of the subsequent concentration process can be influenced. In order to avoid this hidden danger, it is preferable that, in the above embodiments, no matter the pre-concentration treatment method of single-tower rectification or double-tower distillation plus rectification is adopted to pre-concentrate the waste dilute nitric acid, the operation conditions of each tower are controlled so that the mass content of the organic matters in the recovered dilute nitric acid is not higher than 0.1%. After the treatment mode is determined, the ordinary operation parameters such as the height of the tower, the reflux ratio, the position of a feed plate and the like can be optimized by a method known by the person skilled in the art, and the control target that the mass content of organic matters in the recovered dilute nitric acid is not higher than 0.1% is realized, but the data is not known by the person skilled in the art.

In one embodiment, it is preferred that the concentration of the recovered concentrated nitric acid is not less than 80%. Preferably, in the step S3, the fresh concentrated sulfuric acid and the recovered concentrated sulfuric acid are used as extraction media together to concentrate the recovered dilute nitric acid, the concentration of the fresh concentrated sulfuric acid is preferably 80-98%, and the mass ratio of the extraction media to the recovered dilute nitric acid is preferably 1.5-4: 1. Preferably, the concentration of the sulfuric acid aqueous solution is 70-80%.

In the treatment method, the recovered dilute nitric acid obtained after pre-concentration is further concentrated by adopting a sulfuric acid method, so that the recovered concentrated nitric acid with the nitric acid concentration higher than the azeotropic concentration of nitric acid water is obtained, and the problems of waste of nitric acid and environmental safety and cost caused by waste acid treatment are solved. Many reports have been made on the concentration of nitric acid by the sulfuric acid method, and the method is well known to those skilled in the art. Those skilled in the art are particularly aware of: the high boiling point organic matter of this application replaces nitrobenzoic acid and is high energy compound, has high explosion risk, and when sulfuric acid process concentrated the nitric acid waste liquid, should pay special attention to the safety problem, and only when getting into the organic matter mass content that retrieves in the dilute nitric acid and not being higher than 0.1% within the scope, this concentration process is intrinsically safe. Under the premise, the recovered dilute nitric acid can be concentrated by adopting the prior published technology to obtain the recovered concentrated nitric acid with the mass percentage content of not less than 80 percent. The recovered concentrated nitric acid with the concentration lower than 80% is not in the preferable range of the present invention, because when the concentration of the recovered concentrated nitric acid is lower than 80%, the production efficiency of the nitration of the substituted benzoic acid is greatly reduced if the recovered concentrated nitric acid is directly applied to the nitration reaction of the substituted benzoic acid, and thus, in order to ensure the concentration of the concentrated nitric acid in the concentrated nitric acid supply unit, the concentration and the addition amount of the fresh concentrated nitric acid are required to be increased, and the excessive nitric acid is caused.

The recovered concentrated nitric acid obtained by concentrating nitric acid by a sulfuric acid method is reddish brown due to the dissolution of nitrogen oxides such as nitrogen dioxide and the like, can be directly applied to nitric acid utilization processes such as nitration reaction of substituted benzoic acid and the like in practical application, can also be applied after bleaching, and is preferably applied after bleaching. Therefore, in a preferred embodiment, the above treatment method further comprises bleaching the recovered concentrated nitric acid to obtain bleached concentrated nitric acid and fourth smoke tail gas, and preferably, the bleaching agent used in the bleaching is an oxygen-containing gas with an oxygen content of not less than 15% by mass. According to the application, the bleaching process can be adjusted, so that the appearance of the recovered concentrated nitric acid meets the appearance requirement specified in 5.1 in GB/T337.1-2014, namely, the recovered concentrated nitric acid is yellowish or yellow transparent liquid. After the treatment mode is determined, the skilled person can optimize the conventional operation parameters such as the type, the amount, the pressure, the height of the bleaching tower and the like of the bleaching agent by a known method to obtain the chromaticity control target of the recovered concentrated nitric acid. Oxygen-containing gases are often used for bleaching nitric acid because of their strong oxidizing properties, low cost, and availability. In order to reduce the subsequent tail gas treatment capacity, the oxygen-containing gas with the oxygen content of not less than 15 percent by mass is preferred. The bleaching operation can be referred to in the prior art, and is not described in detail herein.

The concentration of sulfuric acid is reduced after the sulfuric acid method is adopted to concentrate nitric acid to obtain a sulfuric acid aqueous solution, and the sulfuric acid aqueous solution is applied to nitric acid concentration after being concentrated, so that the use amount of sulfuric acid can be greatly reduced, and the problems of environmental safety and cost caused by sulfuric acid waste and sulfuric acid aqueous solution treatment are avoided. The concentration of the aqueous sulfuric acid solution can be carried out by those skilled in the art with reference to the concentration techniques of sulfuric acid water known in the art. And controlling the mass percentage concentration of the sulfuric acid in the obtained wastewater to be not higher than 2%, and controlling the mass percentage concentration of the sulfuric acid in the obtained crude concentrated sulfuric acid to be 80-96%. Those skilled in the art are particularly aware of: high boiling point organic matter in this application replaces nitrobenzoic acid and is high energy compound, has high explosion risk, when adopting prior art to concentrate sulphuric acid water, should pay special attention to the safety problem. Although the prior art for concentrating sulfuric acid water can realize the concentration of dilute sulfuric acid, the cyclic application of sulfuric acid in the concentration process of nitric acid cannot be realized, because the aqueous solution of sulfuric acid contains an organic solvent instead of nitrobenzoic acid due to the introduction of the prior art. In the existing sulfuric acid water concentration process, no organic matter is separated and discharged, so that the organic matter is enriched in sulfuric acid water, and is finally conducted to the concentration of the organic matter in the concentrated nitric acid obtained by concentrating nitric acid by a sulfuric acid method, the quality of the concentrated nitric acid obtained by recycling is influenced, and coking, carbonization and even explosion occur in the concentrated sulfuric acid enriched with a large amount of substituted nitrobenzoic acid. In order to solve the problem, the inventor carries out a great deal of experimental research, and finally finds that white or light yellow organic solid impurities are separated out after sulfuric acid is concentrated and cooled, the separated organic solid impurities are gradually increased along with the increase of the number of times of cyclic application of the sulfuric acid, the color of the crude concentrated sulfuric acid obtained after concentration is gradually blackened along with the increase of the organic solid impurities, black blocky solid impurities are separated out after cooling, and the phenomenon of wall sticking is caused, so that the organic matters dissolved in the sulfuric acid are proved to be carbonized and coked in the high-temperature concentration stage of the sulfuric acid. The purpose of this application sulphuric acid is refined is to detach the organic solid impurity that the cooling in-process was separated out after the sulphuric acid concentration, avoids sulphuric acid to apply mechanically to form the endless loop, causes the enrichment of organic solid impurity, if the organic matter takes place the carbonization coking in sulphuric acid concentration process, the adhesion is in the reboiler, light then influences the efficiency of reboiler, heavy then arouses the explosion. Researches show that the organic solid impurities have higher solubility in sulfuric acid at higher temperature and can be separated out only after temperature reduction, so that the temperature has larger influence on the solubility of the organic impurities in the sulfuric acid. The lower the concentration of the sulfuric acid is, the lower the solubility of the organic matter in the sulfuric acid is, and in a nitric acid concentration system in which the sulfuric acid participates, the mass percentage of the sulfuric acid in a sulfuric acid aqueous solution obtained by concentrating the nitric acid in a tower kettle by the sulfuric acid is the lowest, but because the temperature is higher at this moment, no solid organic impurities are separated out, and the next step of sulfuric acid concentration also needs higher temperature, if the sulfuric acid aqueous solution is directly cooled and refined at this stage, the energy consumption is greatly increased, and the analysis shows that the organic matter dissolved in the sulfuric acid at the sulfuric acid concentration stage reacts with the sulfuric acid to generate other organic impurities, so that the sulfuric acid refining before the sulfuric acid concentration is not the optimal scheme. Because the temperature of the concentrated sulfuric acid is required to be reduced to 60-90 ℃ in advance before the concentrated sulfuric acid enters a nitric acid concentration tower, a sulfuric acid refining link is added after the concentration of the sulfuric acid, so that the energy-saving effect can be achieved, and the aim of removing organic solid impurities can be fulfilled.

In the prior art relating to the recovery of waste sulfuric acid, there are various refining methods, for example, chinese patent CN102951617B discloses a purification treatment system and method for waste sulfuric acid, which blows out all volatile organic impurities, most soluble organic impurities and part of oligomers in the waste sulfuric acid by hot air. The method is explained to blow out volatile substances dissolved in sulfuric acid, heavy component impurities or organic impurities formed after chemical reaction with sulfuric acid cannot be solved, and most of organic matters in the acid related to the invention are heavy component organic impurities with high boiling point; chinese patent application CN 109721035A discloses a purification and concentration process of waste dilute sulfuric acid, which removes organic matters in the waste dilute sulfuric acid by multiple operations such as oxidation, membrane filtration, and stripping system treatment, and has a complex process and complicated operation; chinese patent application CN 109694043A discloses a method for comprehensive treatment and recycling of waste sulfuric acid, which is not suitable for the present invention, by subjecting waste sulfuric acid and water to hydrolysis reaction, some organic matters in waste sulfuric acid which are difficult to be treated later are hydrolyzed into small molecular organic matters, then volatile organic matters and soluble organic impurities in waste sulfuric acid are sufficiently removed by subsequent first-stage reduced pressure stripping and second-stage reduced pressure concentration, and then the remaining organic impurities are removed by subsequent oxidation and decoloration. The inventor carries out a large number of experimental researches, and finally finds that aiming at a specific organic matter system of the application, the principle that the solubility of organic matters in sulfuric acid is different at different temperatures can be utilized, the concentrated sulfuric acid can be cooled, high-energy and high-boiling-point organic matters dissolved in the sulfuric acid can be separated out at the moment, and then organic solid impurities separated out from the concentrated sulfuric acid can be removed by adopting a conventional solid-liquid separation method, so that an organic matter outlet is found for a whole circulating system for using and recycling the sulfuric acid, and the effects of ensuring the recycling of the sulfuric acid, ensuring the quality of the sulfuric acid and improving the safety are achieved.

Based on the above study, it is preferable that the step S5 includes: condensing the crude concentrated sulfuric acid to 60-90 ℃, and crystallizing to separate out an organic solid to obtain a condensation system; and carrying out solid-liquid separation on the condensation system to obtain recovered concentrated sulfuric acid and solid waste.

In the steps S1, S2, S3, and the nitric acid bleaching process, there is a smoke exhaust generated, and the smoke exhaust is directly discharged to seriously pollute the environment, and in order to avoid the pollution, the treatment method preferably further includes a step of performing absorption treatment on the first smoke exhaust, the second smoke exhaust, the third smoke exhaust, and the fourth smoke exhaust to obtain a smoke absorption liquid and a waste gas, preferably performing absorption treatment by using at least part of the wastewater of the step S4 as at least part of the absorbent, and preferably, the nitric acid concentration in the smoke absorption liquid is 10-40%. When the waste water of the step S4 is adopted to absorb the nitric acid smoke tail gas, the comprehensive utilization of water resources is further realized, and the waste water discharge is reduced.

The nitric acid containing high-boiling point organic matters is any one of the following nitric acids:

(1) the nitration reaction liquid obtained after the following chemical reactions,

(2) separating mother liquor obtained by solid-liquid separation of nitration reaction liquid obtained after the above-mentioned chemical reaction,

(3) a mixture obtained by mixing the nitration liquid shown in (1) with nitric acid of another source,

(4) a mixture obtained by mixing the separation mother liquor shown in (2) with nitric acid of another source.

In another exemplary embodiment of the present application, there is provided a method of preparing a substituted nitrobenzoic acid, as shown in fig. 5, comprising: mixing substituted benzoic acid and concentrated nitric acid, and carrying out nitration reaction to obtain nitration reaction liquid and smoke tail gas, wherein the nitration reaction liquid has high boiling point organic matters shown in a general formula I, the nitric acid concentration of the concentrated nitric acid is not lower than 80%, and the substituted benzoic acid has a structure shown in a general formula II:

According to the method, the concentrated nitric acid is obtained by treating and recycling the nitration reaction liquid generated by nitration of the substituted benzoic acid through preconcentration and further concentration by a sulfuric acid method, and can be directly applied to the nitration reaction of the substituted benzoic acid or applied to other purposes, so that the recovery and the recycling of the waste nitric acid are really realized, the utilization rate of the nitric acid used for the nitration reaction is improved, the zero emission of the waste nitric acid is achieved, and the problems of safety, environmental protection and cost caused by the treatment of the waste nitric acid are avoided. The higher the content of organic substances, in particular nitro compounds, in the nitric acid or sulfuric acid during the distillation or rectification operation, the more dangerous the operation. In the method, firstly, the nitration reaction liquid generated by nitration of the substituted benzoic acid is diluted to a lower concentration, and most organic matters are separated in a solid-liquid separation mode, so that more organic matters are prevented from entering a concentration stage, and the safety of the concentration stage is preliminarily ensured; then, a pre-concentration process is set before sulfuric acid participates in nitric acid concentration, so that the content of organic matters in the waste nitric acid is greatly reduced while nitric acid pre-concentration is realized, the energy-saving effect is achieved, and meanwhile, the safety of a concentration stage is further ensured; the sulfuric acid refining process is arranged in the process of mechanically applying sulfuric acid to remove organic solid impurities separated out in the sulfuric acid concentration process, so that the enrichment of the organic solid impurities and the carbonization and coking of organic matters in the sulfuric acid concentration process are avoided, the quality and the utilization rate of the sulfuric acid are ensured, and the safety of the concentration stage is further ensured. The safety problem of the nitric acid applying process can be thoroughly solved through the synergistic effect of the processes.

The concentrated nitric acid used for the nitration reaction is recovered concentrated nitric acid and/or fresh concentrated nitric acid obtained in the treatment method, or the treatment method further comprises bleaching the recovered concentrated nitric acid to obtain bleached concentrated nitric acid and fourth nitric acid smoke tail gas, and the concentrated nitric acid used for the nitration reaction is the bleached concentrated nitric acid and/or fresh concentrated nitric acid obtained in the treatment method. In order to further save the consumption of nitric acid for preparing the substituted nitrobenzoic acid, concentrated nitric acid used for nitration is preferably recovered or bleached, and fresh concentrated nitric acid is supplemented when the consumption is not enough.

In order to improve the conversion rate, the feeding mass ratio of the concentrated nitric acid to the substituted benzoic acid is preferably 2-5: 1, and the reaction temperature is-30-60 ℃.

In yet another exemplary embodiment of the present application, a nitric acid treatment system is provided that includes a high boiling point organic compound, which is any one or more of compounds having the following general formula I,

as shown in fig. 6, the treatment system includes a solid-liquid separation unit 10, a nitric acid preconcentration unit 20 for preconcentrating the waste dilute nitric acid, a sulfuric acid method nitric acid concentration unit 30 for concentrating the recovered dilute nitric acid by using a sulfuric acid method, a sulfuric acid concentration unit 40 for concentrating a sulfuric acid aqueous solution, and a sulfuric acid refining unit 50 for refining the crude concentrated sulfuric acid, wherein the solid-liquid separation unit 10 is used for performing solid-liquid separation on the nitric acid containing high-boiling point organic matters to obtain a first high-boiling point organic matter product, waste dilute nitric acid, and a first nitric acid smoke tail gas, and the solid-liquid separation unit 10 has a to-be-treated nitric acid inlet, a waste dilute nitric acid outlet, and a first nitric acid smoke tail gas outlet; the nitric acid preconcentration unit 20 is provided with a waste dilute nitric acid inlet, a recovered dilute nitric acid outlet, a recovered waste water outlet and a second nitric acid smoke tail gas outlet, and the waste dilute nitric acid inlet is connected with the waste dilute nitric acid outlet; the sulfuric acid method nitric acid concentration unit 30 is provided with a concentrated sulfuric acid inlet, a recovered dilute nitric acid inlet, a recovered concentrated nitric acid outlet, a sulfuric acid aqueous solution outlet and a third nitric acid tail gas outlet, wherein the recovered dilute nitric acid inlet is connected with the recovered dilute nitric acid outlet; the sulfuric acid concentration unit 40 is provided with a sulfuric acid aqueous solution inlet, a waste water outlet and a crude concentrated sulfuric acid outlet, and the sulfuric acid aqueous solution inlet is connected with the sulfuric acid method nitric acid concentration unit 30 connected with the sulfuric acid aqueous solution outlet; and the sulfuric acid refining unit 50 has a crude concentrated sulfuric acid inlet, a recovered concentrated sulfuric acid outlet, and a solid waste outlet, the crude concentrated sulfuric acid inlet is connected to the crude concentrated sulfuric acid outlet, and the recovered concentrated sulfuric acid outlet is connected to the concentrated sulfuric acid inlet to convey the recovered concentrated sulfuric acid to the sulfuric acid process nitric acid concentration unit 30.

The processing system is utilized to realize the following steps: step S1, performing solid-liquid separation on the nitric acid containing high-boiling-point organic matters to obtain a first high-boiling-point organic matter product, waste dilute nitric acid and first smoke exhaust; step S2, pre-concentrating the waste dilute nitric acid to obtain recovered waste water, recovered dilute nitric acid and second nitric acid smoke tail gas, wherein the concentration of nitric acid in the recovered waste water is lower than that in the recovered dilute nitric acid; step S3, concentrating the recovered dilute nitric acid by a sulfuric acid method to obtain recovered concentrated nitric acid, a sulfuric acid aqueous solution and a third nitric acid smoke tail gas; step S4, concentrating the sulfuric acid aqueous solution to obtain waste water and crude concentrated sulfuric acid, wherein the mass percentage concentration of sulfuric acid in the waste water is not higher than 2%, and the mass percentage concentration of sulfuric acid in the crude concentrated sulfuric acid is 80-96%; and step S5, refining the crude concentrated sulfuric acid to obtain recovered concentrated sulfuric acid and solid waste, and returning the recovered concentrated sulfuric acid to step S3 to be used as sulfuric acid for concentrating and recovering dilute nitric acid by a sulfuric acid method.

The treatment system of the application carries out organic matter separation and preconcentration to the nitric acid containing high boiling point organic matter by adopting the solid-liquid separation unit 10 and the nitric acid preconcentration unit 20, obtains the recovered dilute nitric acid which can be concentrated by adopting a sulfuric acid extraction method, and can realize zero emission of the waste nitric acid by utilizing the sulfuric acid method nitric acid concentration unit 30 to obtain the recovered concentrated nitric acid of which the nitric acid concentration is higher than the azeotropic concentration of nitric acid water in the nitric acid concentration stage, thereby avoiding the problems of safety, environmental protection and cost caused by the treatment of the waste nitric acid. Furthermore, the higher the content of organic, in particular nitro compounds in nitric acid or sulfuric acid during the distillation or rectification operation, the more dangerous the operation is, according to the general knowledge of the person skilled in the art. According to the method, firstly, the waste dilute nitric acid containing high-boiling-point organic matters is diluted to a lower concentration, most of the organic matters are separated in a solid-liquid separation mode, more organic matters are prevented from entering a concentration stage, and the safety of the concentration stage is preliminarily ensured; then, a pre-concentration process is set before sulfuric acid participates in nitric acid concentration, so that the content of organic matters in waste dilute nitric acid is greatly reduced while nitric acid pre-concentration is realized, the energy-saving effect is achieved, and meanwhile, the safety of a concentration stage is further ensured; the sulfuric acid refining process is set in the process of mechanically applying sulfuric acid, so that organic solid impurities separated out in the sulfuric acid concentration process are removed, the enrichment of the organic solid impurities and the carbonization and coking of organic matters in the sulfuric acid concentration process are avoided, the quality and the utilization rate of the sulfuric acid are ensured, and the safety of the concentration stage is further ensured. Therefore, the recovered concentrated nitric acid and the recovered concentrated sulfuric acid obtained by the treatment method meet the recycling requirement.

There are various means for achieving the solid-liquid separation of the solid-liquid separation unit 10, and in one embodiment, the solid-liquid separation unit 10 includes a first dilution means having a first diluent inlet and a post-dilution system outlet; the first solid-liquid separation device is provided with an inlet of a system to be separated, an outlet of waste dilute nitric acid and an outlet of first nitric acid smoke tail gas, the outlet of the diluted system is connected with the inlet of the system to be separated, and preferably, the outlet of recovered waste water is connected with the inlet of a first diluent. Diluting nitric acid containing high-boiling-point organic matters by using the first diluting device so as to separate out the high-boiling-point organic matters in the nitric acid to obtain a diluted nitric acid system to be treated; and then carrying out solid-liquid separation on the diluted nitric acid system to be treated by using a first solid-liquid separation device to obtain a first high-boiling-point organic product, waste dilute nitric acid and first nitric acid smoke tail gas.

In another embodiment, the solid-liquid separation unit 10 comprises a second solid-liquid separation device, a second dilution device and a third solid-liquid separation device, wherein the second solid-liquid separation device is provided with a separation mother liquor outlet and a first nitrate smoke tail gas outlet a; the second diluting device is provided with a second diluent inlet, a separated mother liquid inlet and a diluted mother liquid outlet, and the separated mother liquid inlet is connected with the separated mother liquid outlet; the third solid-liquid separation device is provided with a mother liquor inlet to be separated, a waste dilute nitric acid outlet and a first nitric acid tail gas outlet B, the diluted mother liquor outlet is connected with the mother liquor inlet to be separated, and the preferable recycled wastewater outlet is connected with the second diluent inlet. Performing first solid-liquid separation on the nitric acid containing the high-boiling-point organic matters by using the second solid-liquid separation device to obtain part of first high-boiling-point organic matter products, separation mother liquor and part of first smoke tail gas; diluting the separated mother liquor by using a second diluting device so as to separate out high-boiling-point organic matters in the separated mother liquor, thereby obtaining diluted mother liquor; and carrying out solid-liquid separation on the diluted mother liquor by using a third solid-liquid separation device to obtain waste dilute nitric acid, the remaining first high-boiling-point organic product and the remaining first smoke tail gas.

In the above embodiment, in order to reduce the wastewater discharge, it is preferable to dilute nitric acid containing high-boiling point organic substances with the recovered wastewater as at least a part of the diluent. Or diluting the separated mother liquor by using the recovered waste water as at least part of the diluent. When the above-mentioned recovered waste water is insufficient, it is supplemented with fresh water.

The nitric acid preconcentration has the function of preconcentrating the waste dilute nitric acid, and simultaneously, the content of organic matters in the waste dilute nitric acid is greatly reduced, so that the safety risk in the subsequent operation process is further reduced. Various combinations of devices are possible to implement the nitric acid preconcentration unit 20 described above. In one embodiment, as shown in fig. 7, the nitric acid preconcentration unit 20 comprises a first rectification column 21, wherein the first rectification column 21 has a waste dilute nitric acid inlet, a recovered dilute nitric acid outlet and a second nitric acid tail gas outlet, the top of the column has a recovered waste water outlet, and the bottom of the column has a concentrated solution outlet; the concentrated solution outlet is connected with the nitric acid inlet to be treated, or the nitric acid preconcentration unit 20 comprises a first rectifying tower 21, a third diluting device 22 and a fourth solid-liquid separation device 23, wherein the first rectifying tower 21 is provided with a waste dilute nitric acid inlet, a recovered dilute nitric acid outlet and a second nitric acid smoke tail gas outlet, the tower top is provided with a recovered waste water outlet, and the tower bottom is provided with a concentrated solution outlet; the third diluting device 22 is provided with a concentrated solution inlet, a third diluent inlet and a diluted concentrated solution outlet, and the concentrated solution inlet is connected with the concentrated solution outlet; the fourth solid-liquid separation device 23 has a to-be-separated concentrated liquid inlet and a separated liquid outlet, the to-be-separated concentrated liquid inlet is connected with the diluted concentrated liquid outlet, the preferred separated liquid outlet is connected with the waste dilute nitric acid inlet, and the preferred recovered wastewater outlet is connected with the third diluent inlet. Rectifying the waste dilute nitric acid by using a first rectifying tower 21 to obtain recovered waste water at the tower top, obtain concentrated solution at the tower bottom, and obtain recovered dilute nitric acid and second nitric acid smoke tail gas at the lateral line of the rectifying tower; and diluting the concentrated solution by using a third diluting device 22 and a fourth solid-liquid separating device 23, and then carrying out solid-liquid separation to obtain a separated solution and a second high-boiling-point organic product. Through the connection mode, the separated liquid can be returned to the rectification treatment step to be rectified together with the waste dilute nitric acid, the recovered waste water can be used as at least part of diluent to dilute the concentrated liquid, or the concentrated liquid is returned to the solid-liquid separation unit 10 to be subjected to solid-liquid separation. Part of the recovered wastewater can be used for subsequent dilution of the concentrated solution, and the rest of the recovered wastewater is recycled to the solid-liquid separation unit 10 to be used as a diluent.

In another embodiment, as shown in fig. 8, the nitric acid preconcentration unit 20 comprises a first distillation column 24 and a second distillation column 25, wherein the first distillation column 24 is provided with a waste dilute nitric acid inlet, the top of the column is provided with a recycled wastewater outlet, and the bottom of the column is provided with a dilute nitric acid outlet; the top of the second rectifying tower 25 is provided with a dilute nitric acid recovery outlet and a second nitric acid smoke tail gas outlet, and the bottom of the tower is provided with a concentrated solution outlet; the concentrated solution outlet is connected with the nitric acid inlet to be treated. Or the nitric acid preconcentration unit 20 comprises a first distillation tower 24, a second distillation tower 25, a third dilution device 22 and a fourth solid-liquid separation device 23, wherein the first distillation tower 24 is provided with a waste dilute nitric acid inlet, the tower top is provided with a recycled wastewater outlet, and the tower bottom is provided with a dilute nitric acid outlet; the top of the second rectifying tower 25 is provided with a dilute nitric acid recovery outlet and a second nitric acid smoke tail gas outlet, and the bottom of the tower is provided with a concentrated solution outlet; the third diluting device 22 is provided with a concentrated solution inlet, a third diluent inlet and a diluted concentrated solution outlet, and the concentrated solution inlet is connected with the concentrated solution outlet; the fourth solid-liquid separation device 23 has a to-be-separated concentrated liquid inlet and a separated liquid outlet, the to-be-separated concentrated liquid inlet is connected with the diluted concentrated liquid outlet, the preferred separated liquid outlet is connected with the waste dilute nitric acid inlet, and the preferred recovered wastewater outlet is connected with the third diluent inlet. The waste dilute nitric acid is distilled by a first distillation tower 24, the top of the tower obtains recycled waste water, and the bottom of the tower obtains dilute nitric acid; rectifying the dilute nitric acid by using a second rectifying tower 25 to obtain recovered dilute nitric acid and second nitric acid smoke tail gas at the tower top and obtain concentrated solution at the tower bottom; and diluting the concentrated solution by using a third diluting device 22 and a fourth solid-liquid separating device 23, and then carrying out solid-liquid separation to obtain a separated solution and a second high-boiling-point organic product.

In still another embodiment, as shown in fig. 9, the nitric acid preconcentration unit 20 includes a second distillation column 26 and a third distillation column 27, the second distillation column 26 has an inlet for the waste dilute nitric acid and an outlet for the heavy components, the top of the column has an outlet for the recovered waste water, and the bottom of the column has an outlet for the concentrated solution; the top of the rectifying tower 25 is provided with a recovered dilute nitric acid outlet and a second nitric acid smoke tail gas outlet, the bottom of the rectifying tower is provided with a dilute nitric acid outlet, and the preferred dilute nitric acid outlet is connected with a waste dilute nitric acid inlet; the concentrated solution outlet is connected with the nitric acid inlet to be treated. Or the nitric acid preconcentration unit 20 includes: the second distillation tower 26 is provided with a waste dilute nitric acid inlet and a heavy component outlet, the tower top is provided with a recycled wastewater outlet, and the tower bottom is provided with a concentrated solution outlet; the top of the third rectifying tower 27 is provided with a recovered dilute nitric acid outlet and a second nitric acid smoke tail gas outlet, the bottom of the tower is provided with a dilute nitric acid outlet, and preferably, the dilute nitric acid outlet is connected with a waste dilute nitric acid inlet; the third diluting device 22 is provided with a concentrated solution inlet, a third diluent inlet and a diluted concentrated solution outlet, and the concentrated solution inlet is connected with the concentrated solution outlet; the fourth solid-liquid separation device 23 has a to-be-separated concentrated liquid inlet and a separated liquid outlet, the to-be-separated concentrated liquid inlet is connected with the diluted concentrated liquid outlet, the preferred separated liquid outlet is connected with the waste dilute nitric acid inlet, and the preferred recovered wastewater outlet is connected with the third diluent inlet. Distilling the waste dilute nitric acid by using a second distillation tower 26 to obtain recycled wastewater at the tower top, obtain concentrated solution at the tower bottom and obtain heavy components at the lateral line of a rectifying tower; rectifying the heavy components by using a third rectifying tower 27 to obtain recovered dilute nitric acid and second nitric acid smoke tail gas at the tower top and dilute nitric acid at the tower bottom; and diluting the concentrated solution by using a third diluting device 22 and a fourth solid-liquid separating device 23, and then carrying out solid-liquid separation to obtain a separated solution and a second high-boiling-point organic product.

In the treatment method, the recovered dilute nitric acid obtained after pre-concentration is further concentrated by adopting a sulfuric acid method, so that the recovered concentrated nitric acid with the nitric acid concentration higher than the azeotropic concentration of nitric acid water is obtained, and the problems of waste of nitric acid and environmental safety and cost caused by waste acid treatment are solved. In order to flexibly adjust the concentration of the concentrated sulfuric acid, it is preferable that the sulfuric acid method nitric acid concentration unit 30 includes a concentration device and a fresh concentrated sulfuric acid supply device, and the concentration device has a concentrated sulfuric acid inlet, a recovered dilute nitric acid inlet, a recovered concentrated nitric acid outlet, a sulfuric acid aqueous solution outlet, and a third nitric acid smoke tail gas outlet; the fresh concentrated sulfuric acid supply device is connected with the concentrated sulfuric acid inlet.

The recovered concentrated nitric acid obtained by concentrating nitric acid by a sulfuric acid method is reddish brown due to the dissolution of nitrogen oxides such as nitrogen dioxide and the like, can be directly applied to nitric acid utilization processes such as nitration reaction of substituted benzoic acid and the like in practical application, can also be applied after bleaching, and is preferably applied after bleaching. Therefore, in a preferred embodiment, the treatment system further comprises a bleaching unit connected to the recovered concentrated nitric acid outlet for bleaching the recovered concentrated nitric acid obtained from the sulfuric acid method nitric acid concentration unit 30 to obtain bleached concentrated nitric acid and a fourth flue gas.

In order to reduce exhaust emission, the bleaching unit is provided with a fourth nitrate tail gas outlet, the treatment system further comprises a nitrate tail gas absorption unit, the nitrate tail gas absorption unit is provided with an absorbent inlet and a nitrate tail gas inlet, the first nitrate tail gas outlet, the second nitrate tail gas outlet, the third nitrate tail gas outlet and the fourth nitrate tail gas outlet are all connected with the nitrate tail gas inlet, and the preferable wastewater outlet is connected with the absorbent inlet.

Based on the foregoing principle of sulfuric acid refining, it is preferable that the sulfuric acid refining unit 50 includes a condensing device having a crude concentrated sulfuric acid inlet and a condensing system outlet, and a fifth solid-liquid separation device; the fifth solid-liquid separation device is provided with a condensation system inlet and a concentrated sulfuric acid recovery outlet, and the condensation system inlet is connected with the condensation system outlet. Condensing the crude concentrated sulfuric acid to 60-90 ℃ by using a condensing device, and crystallizing to separate out an organic solid to obtain a condensing system; and carrying out solid-liquid separation on the condensation system by using a fifth solid-liquid separation device to obtain recovered concentrated sulfuric acid and solid waste.

In another exemplary embodiment of the present application, an apparatus for preparing substituted nitrobenzoic acid is provided, the apparatus includes a nitration reaction system 01 and a nitration reaction liquid treatment system, the nitration reaction system 01 is configured to mix substituted benzoic acid with concentrated nitric acid and then perform nitration reaction to obtain nitration reaction liquid and smoke exhaust gas, and has a nitration reaction liquid outlet, the nitration reaction liquid has high boiling point organic matter shown in general formula I, the nitric acid concentration of the concentrated nitric acid is not lower than 80%, and the substituted benzoic acid has a structure shown in general formula II:

the nitration liquid treatment system is any one of the treatment systems, and the nitration liquid outlet is connected with the to-be-treated nitric acid inlet of the treatment system.

According to the treatment system of the equipment, the nitration reaction liquid generated by nitration of the substituted benzoic acid is treated and recovered to obtain the concentrated nitric acid through preconcentration and further concentration by a sulfuric acid method, and the concentrated nitric acid can be directly applied to the nitration reaction of the substituted benzoic acid, so that recovery and cyclic application of the waste nitric acid are really realized, the utilization rate of the nitric acid used for the nitration reaction is improved, zero emission of the waste nitric acid is achieved, and the problems of safety, environmental protection and cost caused by treatment of the waste nitric acid are avoided. The higher the content of organic substances, in particular nitro compounds, in the nitric acid or sulfuric acid during the distillation or rectification operation, the more dangerous the operation. According to the equipment, firstly, nitration reaction liquid generated by nitration of substituted benzoic acid is diluted to a lower concentration, most organic matters are separated in a solid-liquid separation mode, more organic matters are prevented from entering a concentration stage, and the safety of the concentration stage is preliminarily ensured; then, a pre-concentration process is set before sulfuric acid participates in nitric acid concentration, so that the content of organic matters in the waste nitric acid is greatly reduced while nitric acid pre-concentration is realized, the energy-saving effect is achieved, and meanwhile, the safety of a concentration stage is further ensured; the sulfuric acid refining process is arranged in the process of mechanically applying sulfuric acid to remove organic solid impurities separated out in the sulfuric acid concentration process, so that the enrichment of the organic solid impurities and the carbonization and coking of organic matters in the sulfuric acid concentration process are avoided, the quality and the utilization rate of the sulfuric acid are ensured, and the safety of the concentration stage is further ensured. The safety problem of the nitric acid applying process can be thoroughly solved through the synergistic effect of the devices.

In order to further save the consumption of nitric acid for preparing substituted nitrobenzoic acid, the nitration system 01 comprises a reaction unit and a concentrated nitric acid supply unit, wherein the reaction unit is provided with a concentrated nitric acid inlet and a nitration liquid outlet, the concentrated nitric acid supply unit is provided with a concentrated nitric acid outlet, a fresh concentrated nitric acid inlet and a second concentrated nitric acid inlet, the concentrated nitric acid inlet is connected with the concentrated nitric acid outlet, the second concentrated nitric acid inlet is connected with a recovered concentrated nitric acid outlet of the nitration liquid treatment system, or the nitration liquid treatment system further comprises a bleaching unit, the bleaching unit is connected with the recovered concentrated nitric acid outlet and is used for bleaching the recovered concentrated nitric acid obtained by the sulfuric acid process nitric acid concentration unit 30 to obtain bleached concentrated nitric acid and fourth nitric acid tail gas, the bleaching unit is provided with a bleached concentrated nitric acid outlet, and the bleached nitric acid outlet is connected with the second concentrated nitric acid. In the event that the recovered concentrated nitric acid is insufficient to provide sufficient concentrated nitric acid, fresh concentrated nitric acid may be replenished via a concentrated nitric acid storage tank (not shown in the figure), and the fresh concentrated nitric acid and the recovered concentrated nitric acid jointly enter the concentrated nitric acid supply unit to provide concentrated nitric acid to the reaction unit.

The method for treating nitric acid containing high-boiling organic substances according to the present application is exemplified below:

step S1, organic matter separation: adding nitric acid containing high-boiling-point organic matters into a dilution kettle, adding recovered wastewater or supplementing fresh water again, stirring and diluting, gradually separating out a nitration product (a first high-boiling-point organic matter product) from the nitric acid containing the high-boiling-point organic matters in the stirring and diluting process, diluting the nitric acid to 20-55%, then separating by using conventional solid-liquid separation equipment, separating to obtain the nitration product (the first high-boiling-point organic matter product) and waste dilute nitric acid, and generating first smoke tail gas;

or adding nitric acid containing high-boiling point organic matters into conventional solid-liquid separation equipment, separating out part of a nitration product (a first high-boiling point organic matter product), adding the generated separation mother liquor into a dilution kettle, adding recovered wastewater or supplementing fresh water into the dilution kettle, stirring and diluting, gradually separating out a nitration product (a first high-boiling point organic matter product) from the separation mother liquor in the stirring and diluting process, diluting the concentration of the nitric acid to 20-55%, adding the separation mother liquor into the conventional solid-liquid separation equipment, separating to obtain the nitration product (the first high-boiling point organic matter product) and waste dilute nitric acid, and generating a smoke tail gas in the two-step solid-liquid separation process;

and the first high-boiling-point organic product can be subjected to pulping washing or rinsing or recrystallization by using part or all of the recovered wastewater, then is subjected to solid-liquid separation again, the obtained clear liquid is subjected to pre-concentration treatment, and the obtained solid is an organic product after primary refining.

Step S2, nitric acid preconcentration: the waste dilute nitric acid from the organic matter separation stage enters a nitric acid preconcentration system for preconcentration treatment to obtain recovered wastewater, a nitration product (a second high-boiling-point organic matter product) and a nitric acid preconcentration solution, and a second nitrate smoke tail gas is generated, and the specific implementation mode is as follows:

waste dilute nitric acid enters a rectifying tower for rectification, light components on the top of the tower are condensed by a condenser to form nitric acid water solution with the nitric acid content of not more than 5 percent, namely recovered wastewater, part of the nitric acid water solution can be used for subsequent dilution and filtration operation, the rest of the nitric acid water solution is circulated and reused in an organic matter separation step, or all the nitric acid water solution is circulated and reused in the organic matter separation step, side line heavy components obtain recovered dilute nitric acid and non-condensable nitrol, the mass concentration of the recovered dilute nitric acid and the mass content of the organic matter are not more than 0.1 percent, concentrated solution with the nitric acid concentration of not less than the nitric acid concentration in the waste dilute nitric acid and the azeotropic concentration of not more than the nitric acid water is obtained at the bottom of the rectifying tower, the recovered waste water and/or fresh water can be diluted until the mass concentration of the nitric acid is not less than 20 percent, then the concentrated solution is filtered, and a separated solution and a nitration, or returning to the organic matter separation step;

preferably, the waste dilute nitric acid firstly enters a distillation tower for distillation, the obtained light component at the tower top is a nitric acid water solution with the nitric acid content of not higher than 5 percent, namely recovered wastewater, part of the nitric acid water solution can be used for subsequent dilution and filtration operation, the rest part of the nitric acid water solution is recycled to be used for recycling, or the rest part of the nitric acid water solution is recycled to be used for recycling, the tower bottom liquid of the distillation tower is dilute nitric acid with the nitric acid concentration of not lower than the nitric acid concentration in the waste dilute nitric acid and not higher than the azeotropic concentration of the nitric acid water, the dilute nitric acid and the non-condensable nitric acid fume enter a rectification tower for rectification, the light component at the tower top of the rectification tower is condensed by a condenser to obtain the recovered dilute nitric acid with the mass concentration of not higher than the nitric acid water azeotropic concentration and the organic matter mass content of not higher than 0.1 percent, the concentrated solution with the nitric acid concentration of not lower than the nitric acid concentration in the tower bottom liquid and not higher than the azeotropic, separating liquid and nitration products (first high boiling point organic products) are obtained, the separating liquid and the waste dilute nitric acid are mixed and then enter a distillation tower for distillation, and the organic products can also be returned to the organic matter separation step;

preferably, the waste dilute nitric acid enters a distillation tower for distillation, the obtained light components at the top of the distillation tower are nitric acid water solution with nitric acid content not higher than 5%, namely recovered wastewater, part of the nitric acid water solution enters subsequent dilution filtering operation, the rest part of the nitric acid water solution is recycled to the organic matter separation step for recycling, or the rest part of the nitric acid water solution is recycled to the organic matter separation step for recycling, the heavy components at the lateral line of the distillation tower enter a rectification tower for rectification, the light components at the top of the rectification tower are condensed by a condenser to obtain the recovered dilute nitric acid with mass concentration not higher than the azeotropic concentration of the nitric acid water and organic matter mass content not higher than 0.1%, the tower bottom liquid obtained at the bottom of the rectification tower is dilute nitric acid with nitric acid concentration not lower than the nitric acid concentration in the concentrated liquid at the bottom of the distillation tower and not higher than the azeotropic concentration of the nitric acid water, preferably directly returns to the distillation tower, the concentrated liquid obtained at the bottom of the distillation tower is dilute nitric acid with nitric acid concentration, the method can be used for diluting the recovered waste water and/or fresh water to the mass concentration of the nitric acid not less than 20 percent and then filtering the mixture to obtain separation liquid and nitration products, the separation liquid and the waste dilute nitric acid are mixed and then enter a distillation tower for distillation, and the method can also return to the step of separating organic matters;

the rectification operation of the three nitric acid preconcentration schemes can be operated under the conditions of normal pressure, reduced pressure and pressurization, and preferably under the normal pressure, so that the operation is convenient, and the energy-saving effect can be achieved.

Step S3, nitric acid concentration: the method comprises the steps of enabling recovered dilute nitric acid from a nitric acid preconcentration stage to enter a concentration tower in a nitric acid concentration system together with recovered concentrated sulfuric acid, supplementing and adjusting the mass of supplemented fresh concentrated sulfuric acid with the mass percentage concentration of 80-98%, enabling the mass ratio of a sulfuric acid solution entering the nitric acid concentration tower to a nitric acid solution to be 1.5-4: 1, concentrating the nitric acid preconcentration solution under the action of sulfuric acid, enabling recovered concentrated nitric acid with the mass percentage concentration of 80-98% to be obtained through a condenser at the top of a tower to preferably enter a nitric acid bleaching tower, enabling generated nitric acid smoke tail gas to preferably enter a nitric acid smoke tail gas absorption tower, and enabling a sulfuric acid water solution with the mass percentage concentration of 70-80% to be obtained at the bottom of the tower to enter.

Step S4, sulfuric acid concentration: the sulfuric acid aqueous solution from the nitric acid concentration stage enters a sulfuric acid concentration system, is subjected to primary flash evaporation preconcentration, then enters an evaporator for reduced pressure concentration to obtain crude concentrated sulfuric acid with the mass percentage concentration of 80-96%, acid gas generated in the sulfuric acid concentration process enters an acid gas washing tower, and wastewater with the mass percentage concentration of the sulfuric acid not higher than 2% is obtained in a tower top condenser.

Step S5, sulfuric acid purification: and (2) refining the crude concentrated sulfuric acid in the sulfuric acid concentration stage in a sulfuric acid refining system, condensing the crude concentrated sulfuric acid to 60-90 ℃ by using a condenser, crystallizing and separating out an organic solid, performing conventional solid-liquid separation, such as centrifugation, filter pressing, suction filtration and other conventional operations, separating to obtain recovered concentrated sulfuric acid and solid waste, and recycling the recovered concentrated sulfuric acid to the nitric acid concentration stage.

In the method for treating waste dilute nitric acid containing high-boiling point organic matters, the bleaching of nitric acid and the absorption of nitric acid smoke are preferably increased, and the specific implementation mode is as follows:

bleaching with nitric acid: the recovered concentrated nitric acid from the nitric acid concentration stage enters a nitric acid bleaching tower for bleaching, a bleaching agent, namely oxygen-containing gas with the oxygen mass content not lower than 15%, is introduced into the bottom of the nitric acid bleaching tower, nitrogen oxides contained in the recovered concentrated nitric acid are removed by blowing, fourth smoke tail gas is generated, the refined recovered concentrated nitric acid is obtained, and the appearance meets the appearance requirement of 5.1 specified light yellow or yellow transparent liquid in GB/T337.1-2014.

Absorption of the smoke: mixing the first nitric smoke tail gas from the organic matter separation stage, the second nitric smoke tail gas from the nitric acid preconcentration stage, the third nitric smoke tail gas from the nitric acid concentration stage and the fourth nitric smoke tail gas from the nitric acid bleaching stage, and then feeding the mixture into a nitric smoke absorption tower, and absorbing nitrogen oxides in the nitric smoke tail gas by taking fresh water or waste water generated in the sulfuric acid concentration stage) as an absorbent, preferably taking the waste water generated in the sulfuric acid concentration stage as the absorbent, so as to obtain the nitric smoke absorption liquid with the mass concentration of 10-40% of nitric acid and waste gas.

The conventional solid-liquid separation mentioned in the invention can adopt solid-liquid separation modes such as centrifugation, filtration, filter pressing, suction filtration and the like.

When the nitric acid containing the high-boiling organic matter comes from the nitration of substituted benzoic acids, the nitration comprises:

mixing a raw material substituted benzoic acid and concentrated nitric acid (the mass fraction is not less than 80%) from a concentrated nitric acid supply unit in a mass ratio of 1: 2-5 in an intermittent nitration reactor, and then carrying out nitration reaction, wherein the reaction temperature is-30-60 ℃, the reaction is carried out until the conversion rate of the substituted benzoic acid is not less than 98%, and a nitration reaction liquid (namely nitric acid containing the high-boiling point organic matter) is obtained, and enters a solid-liquid separation step to generate a smoke tail gas;

or mixing the raw material substituted benzoic acid and concentrated nitric acid (the mass fraction is not less than 80%) from a concentrated nitric acid supply unit in a continuous nitration reactor according to the mass ratio of 1: 2-5, and then carrying out nitration reaction, wherein the reaction temperature is-30-60 ℃, the reaction is carried out until the conversion rate of the substituted benzoic acid is not less than 98%, so as to obtain a nitration reaction liquid (namely nitric acid containing the high-boiling point organic matter), and generate a nitrate smoke tail gas, the obtained nitration reaction liquid can be thickened by a thickener, then a dilute phase liquid accounting for 20-70% of the mass fraction of the nitration reaction liquid is mechanically applied to the nitration reaction, and the obtained dense phase slurry enters a solid-liquid separation step.

In order to further illustrate the present invention, the following examples are provided to describe the continuous nitration reaction system and continuous nitration process of methyl benzoic acid, but should not be construed as limiting the scope of the present invention.

Example 1

The substituted benzoic acid adopted in the embodiment is p-toluic acid, fresh concentrated nitric acid with the mass fraction of 80% in a concentrated nitric acid storage tank enters a concentrated nitric acid supply unit and is mixed with the recovered concentrated nitric acid in a nitric acid supply unit to obtain concentrated nitric acid, the p-toluic acid and the concentrated nitric acid are added into a batch reactor according to the mass ratio of 1:5 to be mixed and carry out nitration reaction, the reaction temperature is controlled at 20 ℃, after the feeding is finished, the material is continuously kept at the temperature for 60min in the reactor, the conversion rate of the p-toluic acid is detected by sampling to be 99%, the reaction is stopped, a nitration reaction liquid (namely nitric acid containing high-boiling point organic matters) is obtained, and the tail gas of the nitric acid smoke is generated.

The nitration reaction liquid is diluted by the recovered waste water to 45 mass percent of nitric acid, and then is separated by a centrifuge to obtain a nitration product, namely 3-nitro-4-methyl benzoic acid, and nitration waste liquid (namely the waste diluted nitric acid) generates first smoke tail gas.

The nitrified waste liquid enters a rectifying tower for rectification, recovered waste water with the mass fraction of nitric acid of 2% is obtained at the tower top, dilute nitric acid (namely concentrated solution) with the mass fraction of nitric acid of 66.2% is obtained at the tower bottom, the dilute nitric acid is diluted by fresh water until the mass concentration of the nitric acid is 45%, the dilute nitric acid is filtered in a filter, filtrate (namely separation solution) and a nitrified product, namely 3-nitro-4-methylbenzoic acid are obtained, and the filtrate and the nitrified waste liquid are mixed and then enter the rectifying tower for rectification; and the heavy components in the side line obtain recovered dilute nitric acid and second nitric acid smoke tail gas with the mass concentration of 65.4% and the mass content of organic matters of 360 ppm.

And (3) feeding the recovered dilute nitric acid and the recovered concentrated sulfuric acid with the mass concentration of 80% into a nitric acid concentration tower, supplementing fresh concentrated sulfuric acid with the mass percentage concentration of 98%, and then concentrating the nitric acid to ensure that the mass ratio of the sulfuric acid solution fed into a nitric acid concentration system to the nitric acid solution is 3.3:1, so as to obtain the recovered concentrated nitric acid with the mass percentage content of 80% and a 70% sulfuric acid aqueous solution, and generate a third nitric acid smoke tail gas.

And (3) the sulfuric acid aqueous solution enters a sulfuric acid concentration system for concentration to obtain wastewater with the sulfuric acid mass percentage concentration of 0.4% and crude concentrated sulfuric acid.

And (3) refining the crude concentrated sulfuric acid in a sulfuric acid refining system, condensing the crude concentrated sulfuric acid to 90 ℃ by a condenser, crystallizing to separate out an organic solid, performing suction filtration to obtain recovered concentrated sulfuric acid with the mass percentage concentration of 80% and solid waste, and recycling the recovered concentrated sulfuric acid to a nitric acid concentration stage.

The obtained recovered concentrated nitric acid enters a concentrated nitric acid supply unit.

Mixing the nitric acid smoke tail gas from the nitration reaction stage, the first nitric acid smoke tail gas from the solid-liquid separation stage, the second nitric acid smoke tail gas from the nitric acid preconcentration stage and the third nitric acid smoke tail gas from the nitric acid concentration stage, then feeding the mixture into a nitric acid smoke absorption tower, absorbing nitrogen oxides in the nitric acid smoke tail gas by using waste water with the sulfuric acid mass percentage concentration of 0.4% to obtain nitric acid smoke absorption liquid and waste gas with the nitric acid mass concentration of 10%, and feeding the nitric acid smoke absorption liquid and the nitration waste liquid into a nitric acid preconcentration system.

Example 2

The substituted benzoic acid adopted in the embodiment is benzoic acid, fresh concentrated nitric acid with the mass fraction of 85% in a concentrated nitric acid storage tank is added into a nitric acid supply unit and mixed with bleaching concentrated nitric acid in the nitric acid supply unit to obtain concentrated nitric acid, the benzoic acid and the concentrated nitric acid are added into a continuous nitration reactor according to the mass ratio of 1:2 to be mixed and carry out nitration reaction, the reaction temperature is controlled at 10 ℃, the retention time of materials in the continuous nitration reactor is 20min, nitration reaction liquid (namely nitric acid containing high-boiling point organic matters) is obtained, nitrate smoke tail gas is generated, dilute phase liquid with the mass fraction of 20% of the nitration reaction liquid is mechanically applied to the nitration reaction after the obtained nitration reaction liquid is thickened by a thickener, and the conversion rate of the p-toluic acid is 99.2% by sampling and detecting the obtained thick phase slurry.

Diluting the nitration reaction liquid to 32% of nitric acid mass fraction, and separating with a centrifuge to obtain a nitration product, namely 3-nitrobenzoic acid, a nitration waste liquid (namely waste dilute nitric acid), and generating a first nitrate smoke tail gas.

Firstly, distilling the nitrified waste liquid in a distillation tower to obtain light components of recovered waste water with the nitric acid content of 1%, completely washing a nitrified product to obtain washing liquid for diluting a nitration reaction liquid, feeding distillation tower bottom liquid of dilute nitric acid with the nitric acid concentration of 67.3% into a rectifying tower for rectifying, obtaining recovered dilute nitric acid and non-condensable nitrosmoke (second nitrosmoke tail gas) with the mass concentration of 67.1% and the organic matter mass content of 160ppm at the top of the rectifying tower, diluting the rectifying tower bottom liquid with the concentration of 67.9% with fresh water to the mass concentration of the nitric acid of 32%, filtering in a filter to obtain filtrate (separation liquid) and the nitrified product, namely 3-nitrobenzoic acid, and mixing the filtrate and the nitrified waste liquid and then feeding the filtrate into the distillation tower for distillation;

and (3) feeding the recovered dilute nitric acid and the recovered concentrated sulfuric acid with the mass concentration of 96% into a nitric acid concentration tower, supplementing fresh concentrated sulfuric acid with the mass percentage concentration of 98%, and then concentrating the nitric acid to ensure that the mass ratio of the sulfuric acid solution fed into a nitric acid concentration system to the nitric acid solution is 1.5:1, so as to obtain the recovered concentrated nitric acid with the mass percentage content of 85% and the sulfuric acid aqueous solution with the mass percentage content of 71.5%, and generate third nitric acid smoke tail gas.

And (3) the sulfuric acid aqueous solution enters a sulfuric acid concentration system for concentration to obtain waste water with the sulfuric acid mass percentage concentration of 2% and crude concentrated sulfuric acid.

And (3) refining the crude concentrated sulfuric acid in a sulfuric acid refining system, condensing the crude concentrated sulfuric acid to 60 ℃ by a condenser, crystallizing to separate out an organic solid, performing suction filtration to obtain recovered concentrated sulfuric acid with the mass percentage concentration of 96% and solid waste, and recycling the recovered concentrated sulfuric acid to a nitric acid concentration stage.

And the obtained recovered concentrated nitric acid enters a nitric acid bleaching tower to be bleached by air to generate fourth nitric acid smoke tail gas, and the obtained bleached concentrated nitric acid with light yellow and transparent appearance enters a concentrated nitric acid supply unit.

Mixing the nitric acid smoke tail gas from the nitration reaction stage, the first nitric acid smoke tail gas from the product separation stage, the second nitric acid smoke tail gas from the nitric acid preconcentration stage, the third nitric acid smoke tail gas from the nitric acid concentration stage and the fourth nitric acid smoke tail gas from the nitric acid bleaching stage, then feeding the mixture into a nitric acid smoke absorption tower, absorbing nitric oxides in the nitric acid smoke tail gas by using fresh water to obtain nitric acid smoke absorption liquid with the mass concentration of 40% and waste gas, and feeding the nitric acid smoke absorption liquid and the recovered dilute nitric acid into a nitric acid concentration system.

Example 3

The substituted benzoic acid adopted in the embodiment is m-toluic acid, the mass fraction of nitric acid in fresh concentrated nitric acid provided by a concentrated nitric acid storage tank is 98%, the substituted benzoic acid and the nitric acid are added into a continuous nitration reactor according to the mass ratio of 1:5 to be mixed and subjected to nitration reaction, the reaction temperature is controlled at-30 ℃, the retention time of materials in the continuous nitration reactor is 20min, nitration reaction liquid is obtained, nitrate smoke tail gas is generated, dilute phase liquid accounting for 70% of the mass fraction of the nitration reaction liquid is mechanically applied to the nitration reaction after the obtained nitration reaction liquid is thickened by a thickener, and the conversion rate of the m-toluic acid is 99.5% by sampling and detecting the obtained thick phase slurry.

Adding the nitration reaction liquid into a centrifuge, separating out partial nitration products, namely 2-nitro-3-methylbenzoic acid, adding the generated separation mother liquor into a dilution kettle, adding the recovered wastewater into the dilution kettle, adding fresh water, stirring and diluting to dilute the concentration of nitric acid to 40%, adding the diluted separation mother liquor into the centrifuge, separating to obtain nitration products, namely a mixture of 3-methyl-4-nitrobenzoic acid and 2-nitro-5-methylbenzoic acid and nitration waste liquor, wherein the first nitro smoke tail gas is generated in the two-step solid-liquid separation process;

the nitrified waste liquid enters a distillation tower for distillation, the obtained light components at the top of the tower are nitric acid water solution with the nitric acid content of 4%, namely recovered waste water, the heavy components at the side line enter a rectifying tower for rectification, recovered dilute nitric acid with the mass concentration of 67% and the organic matter mass content of 90ppm and second nitric acid smoke tail gas are obtained at the top of the rectifying tower, the tower bottom liquid of the distillation tower with the nitric acid concentration of 67.7% is diluted to the nitric acid concentration of 50% by using the recovered waste water and then filtered in a filter, filtrate and nitrified products, namely 2-nitro-5-methylbenzoic acid are obtained, the filtrate and the nitrified waste liquid are mixed and then enter the distillation tower for distillation, and the tower bottom liquid with the nitric acid concentration of 68% obtained by the rectifying tower is directly circulated back to the;

and (3) feeding the recovered dilute nitric acid and the recovered concentrated sulfuric acid with the mass concentration of 95% into a nitric acid concentration tower, supplementing fresh concentrated sulfuric acid with the mass percentage concentration of 80%, and then concentrating the nitric acid to ensure that the mass ratio of the sulfuric acid solution fed into a nitric acid concentration system to the nitric acid solution is 4:1, so as to obtain the recovered concentrated nitric acid with the mass percentage content of 98% and the sulfuric acid aqueous solution with the mass percentage concentration of 80%, and generate third nitric acid smoke tail gas.

And (3) the sulfuric acid aqueous solution enters a sulfuric acid concentration system for concentration to obtain wastewater with the sulfuric acid mass percentage concentration of 1.6% and crude concentrated sulfuric acid.

And (3) refining the crude concentrated sulfuric acid in a sulfuric acid refining system, condensing the crude concentrated sulfuric acid to 67 ℃ by a condenser, crystallizing to separate out an organic solid, performing suction filtration to obtain recovered concentrated sulfuric acid with the mass percentage concentration of 95% and solid waste, and recycling the recovered concentrated sulfuric acid to a nitric acid concentration stage.

And the obtained recovered concentrated nitric acid enters a nitric acid bleaching tower to be bleached by air to generate fourth nitric acid smoke tail gas, and the obtained bleached concentrated nitric acid with yellow and transparent appearance enters a concentrated nitric acid storage tank.

Mixing the nitric acid smoke tail gas from the nitration reaction stage, the first nitric acid smoke tail gas from the product separation stage, the second nitric acid smoke tail gas from the nitric acid preconcentration stage, the third nitric acid smoke tail gas from the nitric acid concentration stage and the fourth nitric acid smoke tail gas from the nitric acid bleaching stage, then feeding the mixture into a nitric acid smoke absorption tower, absorbing nitric oxides in the nitric acid smoke tail gas by using fresh water to obtain nitric acid smoke absorption liquid and waste gas with the mass concentration of 20%, and feeding the nitric acid smoke absorption liquid and the nitration waste liquid into a nitric acid preconcentration system.

Example 4

The substituted benzoic acid adopted in the embodiment is o-methylbenzoic acid, the mass fraction of nitric acid in the bleached concentrated nitric acid provided by a concentrated nitric acid storage tank is 95%, the substituted benzoic acid and the nitric acid are added into a continuous nitration reactor according to the mass ratio of 1:4 to be mixed and subjected to nitration reaction, the reaction temperature is controlled at-15 ℃, the retention time of materials in the continuous nitration reactor is 15min, nitration reaction liquid is obtained, nitrate smoke tail gas is generated, dilute phase liquid accounting for 40% of the mass fraction of the nitration reaction liquid is mechanically applied to the nitration reaction after the obtained nitration reaction liquid is thickened by a thickener, and the conversion rate of p-methylbenzoic acid is 98.8% by sampling and detecting the obtained thick phase slurry.

Adding the nitration reaction liquid into a centrifuge, separating out a part of nitration products, namely a mixture of 2-methyl-3-nitrobenzoic acid and 2-methyl-5-nitrobenzoic acid, adding the generated separation mother liquor into a dilution kettle, adding the recovered wastewater into the dilution kettle, adding fresh water again, stirring and diluting to dilute the concentration of nitric acid to 40%, adding the diluted separation mother liquor into the centrifuge, separating to obtain nitration products, namely a mixture of 2-methyl-3-nitrobenzoic acid and 2-methyl-5-nitrobenzoic acid and nitration waste liquor, wherein the first smoke tail gas is generated in the two-step solid-liquid separation process;

the nitrified waste liquid enters a rectifying tower for rectification, recovered waste water with the mass fraction of nitric acid of 4% is obtained at the tower top, dilute nitric acid with the mass fraction of nitric acid of 68% obtained at the tower bottom is diluted by the recovered waste water until the mass concentration of the nitric acid is 42% and then is filtered in a filter, so that a mixture of filtrate and a nitrified product, namely 2-methyl-3-nitrobenzoic acid and 2-methyl-5-nitrobenzoic acid is obtained, and the filtrate and the nitrified waste liquid are mixed and then enter the rectifying tower for rectification; and the heavy components in the side line obtain recovered dilute nitric acid with mass concentration of 67.7% and organic matter mass content of 1000 ppm.

And (3) feeding the recovered dilute nitric acid and the recovered concentrated sulfuric acid with the mass concentration of 88% into a nitric acid concentration tower, supplementing fresh concentrated sulfuric acid with the mass percentage concentration of 95%, and then concentrating the nitric acid to ensure that the mass ratio of the sulfuric acid solution fed into a nitric acid concentration system to the nitric acid solution is 3.5:1, so as to obtain the recovered concentrated nitric acid with the mass percentage content of 95% and a 75% sulfuric acid aqueous solution, and generate a third nitric acid smoke tail gas.

And the sulfuric acid aqueous solution enters a sulfuric acid concentration system for concentration to obtain wastewater with the sulfuric acid mass percentage concentration of 0.9% and crude concentrated sulfuric acid.

And (3) refining the crude concentrated sulfuric acid in a sulfuric acid refining system, condensing the crude concentrated sulfuric acid to 86 ℃ by a condenser, crystallizing to separate out an organic solid, performing suction filtration to obtain recovered concentrated sulfuric acid with the mass percentage concentration of 88% and solid waste, and recycling the recovered concentrated sulfuric acid to a nitric acid concentration stage.

Mixing the nitric acid smoke tail gas from the nitration reaction stage, the first nitric acid smoke tail gas from the product separation stage, the second nitric acid smoke tail gas from the nitric acid preconcentration stage, the third nitric acid smoke tail gas from the nitric acid concentration stage and the fourth nitric acid smoke tail gas from the nitric acid bleaching stage, then feeding the mixture into a nitric acid smoke absorption tower, absorbing nitric oxides in the nitric acid smoke tail gas by using waste water with the sulfuric acid mass percentage concentration of 0.9% to obtain nitric acid smoke absorption liquid and waste gas with the nitric acid mass concentration of 28%, and feeding the nitric acid smoke absorption liquid and the nitration waste liquid into a nitric acid preconcentration system.

Example 5

The substituted benzoic acid adopted in the embodiment is 3, 5-dimethylbenzoic acid, the mass fraction of nitric acid in fresh concentrated nitric acid provided by a concentrated nitric acid storage tank is 88%, the substituted benzoic acid and the nitric acid are added into a continuous nitration reactor according to the mass ratio of 1:4 to be mixed and have nitration reaction, the reaction temperature is controlled at 0 ℃, the retention time of materials in the continuous nitration reactor is 25min, nitration reaction liquid is obtained, nitrate smoke tail gas is generated, and the conversion rate of the obtained nitration reaction liquid to the methylbenzoic acid is 99.3% by sampling detection.

Adding the nitration reaction liquid into a centrifuge, separating out a part of nitration products, namely a mixture of 3, 5-dimethyl-4-nitrobenzoic acid and 3, 5-dicarboxylic acid-2-nitrobenzoic acid, adding the generated separation mother liquor into a dilution kettle, adding the recovered wastewater into the dilution kettle, adding fresh water again, stirring and diluting to dilute the concentration of nitric acid to 20%, adding the diluted separation mother liquor into the centrifuge, separating to obtain nitration products, namely a mixture of 3, 5-dimethyl-4-nitrobenzoic acid and 3, 5-dicarboxylic acid-2-nitrobenzoic acid and nitration waste liquor, wherein the first nitro smoke tail gas is generated in the solid-liquid two-step separation process;

the nitrified waste liquid is firstly distilled in a distillation tower, the obtained light components at the top of the tower are recovered waste water with the nitric acid content of 4%, tower bottom liquid of dilute nitric acid with the nitric acid concentration of 61.8% enters a rectifying tower for rectification, recovered dilute nitric acid with the mass concentration of 60% and the organic matter content of 160ppm and second nitro-fume tail gas are obtained at the top of the rectifying tower, the tower bottom liquid with the concentration of 64.2% is diluted by fresh water to the nitric acid mass concentration of 20% and then filtered in a filter, so that a mixture of filtrate and nitrified products, namely 3, 5-dimethyl-4-nitrobenzoic acid and 3, 5-dicarboxylic acid-2-nitrobenzoic acid is obtained, and the filtrate and the nitrified waste liquid are mixed and then enter the distillation tower for distillation;

and (3) feeding the recovered dilute nitric acid and the recovered concentrated sulfuric acid with the mass concentration of 85% into a nitric acid concentration tower, supplementing fresh concentrated sulfuric acid with the mass percentage concentration of 90%, and then concentrating the nitric acid to ensure that the mass ratio of the sulfuric acid solution fed into a nitric acid concentration system to the nitric acid solution is 2.7:1, so as to obtain the recovered concentrated nitric acid with the mass percentage content of 88% and a 71% sulfuric acid aqueous solution, and generate a third nitric acid smoke tail gas.

And the sulfuric acid aqueous solution enters a sulfuric acid concentration system for concentration to obtain wastewater with the sulfuric acid mass percentage concentration of 0.6% and crude concentrated sulfuric acid.

And (3) refining the crude concentrated sulfuric acid in a sulfuric acid refining system, condensing the crude concentrated sulfuric acid to 63 ℃ by a condenser, crystallizing to separate out an organic solid, performing suction filtration to obtain recovered concentrated sulfuric acid with the mass percentage concentration of 85% and solid waste, and recycling the recovered concentrated sulfuric acid to a nitric acid concentration stage.

Mixing the nitric acid smoke tail gas from the nitration reaction stage, the first nitric acid smoke tail gas from the product separation stage, the second nitric acid smoke tail gas from the nitric acid preconcentration stage, the third nitric acid smoke tail gas from the nitric acid concentration stage and the fourth nitric acid smoke tail gas from the nitric acid bleaching stage, then feeding the mixture into a nitric acid smoke absorption tower, absorbing nitric oxides in the nitric acid smoke tail gas by using waste water with the sulfuric acid mass percentage concentration of 0.6% to obtain nitric acid smoke absorption liquid and waste gas with the nitric acid mass concentration of 32%, and feeding the nitric acid smoke absorption liquid and the nitration waste liquid into a nitric acid preconcentration system.

Example 6

Diluting a separation mother liquor obtained by carrying out solid-liquid separation on a nitration reaction liquid of p-chlorobenzoic acid to 45 mass percent of nitric acid, and then separating by using a centrifugal machine to obtain a nitration product, namely 3-nitro-4-chlorobenzoic acid, nitrating the waste liquid, and generating a first smoke tail gas.

Firstly, distilling the nitrified waste liquid in a distillation tower to obtain recovered waste water with the top light component of 3.4% of nitric acid, diluting the nitrified reaction liquid by using washing liquid obtained after washing the nitrified product, rectifying tower bottom liquid of dilute nitric acid with the nitric acid concentration of 64.3% in a rectifying tower, obtaining recovered dilute nitric acid and second nitric acid smoke tail gas with the mass concentration of 63.2% and the organic matter mass content of 85ppm at the top of the rectifying tower, diluting tower bottom liquid with the concentration of 66.5% by using fresh water until the nitric acid mass concentration is 45%, filtering in a filter to obtain filtrate and the nitrified product, namely 3-nitro-4-chlorobenzoic acid, and mixing the filtrate and the nitrified waste liquid and then feeding the filtrate into the distillation tower for distillation;

and (3) feeding the recovered dilute nitric acid and the recovered concentrated sulfuric acid with the mass concentration of 87% into a nitric acid concentration tower, supplementing fresh concentrated sulfuric acid with the mass percentage concentration of 85%, and then concentrating the nitric acid to ensure that the mass ratio of the sulfuric acid solution fed into a nitric acid concentration system to the nitric acid solution is 3.6:1, so as to obtain the recovered concentrated nitric acid with the mass percentage content of 92% of nitric acid and a sulfuric acid aqueous solution with the mass percentage content of 74%, and generate third nitric acid smoke tail gas.

And the sulfuric acid aqueous solution enters a sulfuric acid concentration system for concentration to obtain wastewater with the sulfuric acid mass percentage concentration of 0.7% and crude concentrated sulfuric acid.

And (3) refining the crude concentrated sulfuric acid in a sulfuric acid refining system, condensing the crude concentrated sulfuric acid to 65 ℃ by a condenser, crystallizing to separate out an organic solid, performing suction filtration to obtain recovered concentrated sulfuric acid with the mass percentage concentration of 87% and solid waste, and recycling the recovered concentrated sulfuric acid to a nitric acid concentration stage.

Mixing the nitric acid smoke tail gas from the nitration reaction stage, the first nitric acid smoke tail gas from the product separation stage, the second nitric acid smoke tail gas from the nitric acid preconcentration stage, the third nitric acid smoke tail gas from the nitric acid concentration stage and the fourth nitric acid smoke tail gas from the nitric acid bleaching stage, then feeding the mixture into a nitric acid smoke absorption tower, absorbing nitric oxides in the nitric acid smoke tail gas by using waste water with the sulfuric acid mass percentage concentration of 0.7% to obtain nitric acid smoke absorption liquid and waste gas with the nitric acid mass concentration of 25%, and feeding the nitric acid smoke absorption liquid and the nitration waste liquid into a nitric acid preconcentration system.

Example 7

Waste nitric acid generated by oxidizing m-toluic acid by using nitric acid as an oxidant is mixed in a nitration reaction liquid of m-phthalic acid, the waste nitric acid is diluted to 35% by mass of the nitric acid and then is separated by a centrifuge to obtain a nitration product, namely 5-nitroisophthalic acid, and the waste liquid is nitrified to generate first smoke tail gas.

The nitrified waste liquid enters a distillation tower for distillation, the obtained light components at the top of the distillation tower are nitric acid water solution with the nitric acid content of 2.8%, namely recovered waste water, all washing liquid obtained after washing the nitrified product is used for diluting the nitrified reaction liquid, the heavy components at the side line enter a rectification tower for rectification, the recovered dilute nitric acid with the mass concentration of 64.8% and the organic matter mass content of 67ppm and the second nitro-fume tail gas are obtained at the top of the rectification tower, the tower bottom liquid of the distillation tower with the nitric acid concentration of 65.4% is diluted to the nitric acid concentration of 35% by using the recovered waste water and then filtered in a filter, so that filtrate and the nitrified product, namely 5-nitroisophthalic acid are obtained, the filtrate and the nitrified reaction liquid are diluted together, and the tower bottom liquid with the nitric acid concentration of 66.8% obtained by the rectification tower is directly circulated into the;

and (3) feeding the recovered dilute nitric acid and the recovered concentrated sulfuric acid with the mass concentration of 92% into a nitric acid concentration tower, supplementing fresh concentrated sulfuric acid with the mass percentage concentration of 92%, and then concentrating the nitric acid to ensure that the mass ratio of the sulfuric acid solution fed into a nitric acid concentration system to the nitric acid solution is 3:1, so as to obtain the recovered concentrated nitric acid with the mass percentage content of 94% and a 72% sulfuric acid aqueous solution, and generate a third nitric acid smoke tail gas.

And (3) the sulfuric acid aqueous solution enters a sulfuric acid concentration system for concentration to obtain wastewater with the sulfuric acid mass percentage concentration of 1.3% and crude concentrated sulfuric acid.

And (3) refining the crude concentrated sulfuric acid in a sulfuric acid refining system, condensing the crude concentrated sulfuric acid to 65 ℃ by a condenser, crystallizing to separate out an organic solid, performing suction filtration to obtain recovered concentrated sulfuric acid with the mass percentage concentration of 92% and solid waste, and recycling the recovered concentrated sulfuric acid to a nitric acid concentration stage.

Mixing the nitric acid smoke tail gas from the nitration reaction stage, the first nitric acid smoke tail gas from the product separation stage, the second nitric acid smoke tail gas from the nitric acid preconcentration stage, the third nitric acid smoke tail gas from the nitric acid concentration stage and the fourth nitric acid smoke tail gas from the nitric acid bleaching stage, then feeding the mixture into a nitric acid smoke absorption tower, absorbing nitric oxides in the nitric acid smoke tail gas by using fresh water to obtain nitric acid smoke absorption liquid and waste gas with the mass concentration of 37%, and feeding the nitric acid smoke absorption liquid and the recovered dilute nitric acid into a nitric acid concentration system.

Example 8

After being mixed with waste nitric acid generated by oxidizing o-methylbenzoic acid by using nitric acid as an oxidant, separated mother liquor obtained by solid-liquid separation of phthalic acid nitration reaction liquid is diluted to the mass fraction of the nitric acid of 31%, and then separated by a centrifugal machine to obtain a nitration product, namely 3-nitrophthalic acid, which is used for nitrating waste liquid and generating first smoke tail gas.

The nitrified waste liquid enters a distillation tower for distillation, the obtained light components at the top of the distillation tower are nitric acid water solution with the nitric acid content of 1.9%, namely recovered waste water, all washing liquid obtained after washing the nitrified product is used for diluting the nitrified reaction liquid, the heavy components at the side line enter a rectification tower for rectification, the recovered dilute nitric acid with the mass concentration of 62.5% and the organic matter mass content of 59ppm and the second nitro-fume tail gas are obtained at the top of the rectification tower, the tower bottom liquid of the distillation tower with the nitric acid concentration of 64.1% is diluted to the nitric acid concentration of 31% by using the recovered waste water and then filtered in a filter to obtain filtrate and the nitrified product, namely 3-nitrophthalic acid, the filtrate and the nitrified reaction liquid are diluted together, and the tower bottom liquid with the nitric acid concentration of 66.3% obtained by the rectification tower is directly circulated into the distillation;

and (3) feeding the recovered dilute nitric acid and the recovered concentrated sulfuric acid with the mass concentration of 89% into a nitric acid concentration tower, supplementing fresh concentrated sulfuric acid with the mass percentage concentration of 98%, and then concentrating the nitric acid to ensure that the mass ratio of the sulfuric acid solution fed into a nitric acid concentration system to the nitric acid solution is 2.4:1, so as to obtain the recovered concentrated nitric acid with the mass percentage content of 96% and a 77% sulfuric acid aqueous solution, and generate a third nitric acid smoke tail gas.

And (3) the sulfuric acid aqueous solution enters a sulfuric acid concentration system for concentration to obtain wastewater with the sulfuric acid mass percentage concentration of 0.8% and crude concentrated sulfuric acid.

And (3) refining the crude concentrated sulfuric acid in a sulfuric acid refining system, condensing the crude concentrated sulfuric acid to 70 ℃ by a condenser, crystallizing to separate out an organic solid, performing suction filtration to obtain recovered concentrated sulfuric acid with the mass percentage concentration of 89% and solid waste, and recycling the recovered concentrated sulfuric acid to a nitric acid concentration stage.

Mixing the nitric acid smoke tail gas from the nitration reaction stage, the first nitric acid smoke tail gas from the product separation stage, the second nitric acid smoke tail gas from the nitric acid preconcentration stage, the third nitric acid smoke tail gas from the nitric acid concentration stage and the fourth nitric acid smoke tail gas from the nitric acid bleaching stage, then feeding the mixture into a nitric acid smoke absorption tower, absorbing nitric oxides in the nitric acid smoke tail gas by using fresh water to obtain nitric acid smoke absorption liquid and waste gas with the mass concentration of nitric acid of 15%, and feeding the nitric acid smoke absorption liquid and the nitration waste liquid into a nitric acid preconcentration system.

Example 9

The substituted benzoic acid adopted in the embodiment is m-nitrobenzoic acid, the mass fraction of nitric acid in the concentrated nitric acid provided by a concentrated nitric acid storage tank is 95%, the two are added into a batch reaction kettle according to the mass ratio of 1:5 to be mixed and have nitration reaction, the reaction temperature is controlled at 60 ℃, after the feeding is finished, the materials are continuously kept at the temperature for 120min in the reaction kettle, the conversion rate of p-methylbenzoic acid is detected by sampling to be 98%, the reaction is stopped, nitration reaction liquid is obtained, and the tail gas of the smoke is generated.

Diluting the nitration reaction liquid to 55 mass percent of nitric acid, and separating by using a centrifugal machine to obtain a nitration product, namely 3, 5-dinitrobenzoic acid, and nitrating the waste liquid and generating first smoke tail gas.

And (3) the nitrified waste liquid enters a rectifying tower for rectification, the recovered waste water with the mass fraction of 5% of nitric acid is obtained at the tower top, all washing liquid obtained after washing the nitrified product is used for diluting the nitrified reaction liquid, the recovered dilute nitric acid with the mass concentration of 68% and the mass content of organic matters of 780ppm is obtained as the heavy component at the lateral line, and the dilute nitric acid with the mass fraction of 68% obtained at the tower bottom participates in the dilution of the nitrified reaction liquid.

And (3) feeding the recovered dilute nitric acid and the recovered concentrated sulfuric acid with the mass concentration of 90% into a nitric acid concentration tower, supplementing fresh concentrated sulfuric acid with the mass percentage concentration of 90%, and then concentrating the nitric acid to ensure that the mass ratio of the sulfuric acid solution fed into a nitric acid concentration system to the nitric acid solution is 3.2:1, so as to obtain the recovered concentrated nitric acid with the mass percentage content of 95% and a sulfuric acid aqueous solution with the mass percentage content of 73%, and generate third nitric acid smoke tail gas.

And (3) the sulfuric acid aqueous solution enters a sulfuric acid concentration system for concentration to obtain wastewater with the sulfuric acid mass percentage concentration of 1% and crude concentrated sulfuric acid.

And (3) refining the crude concentrated sulfuric acid in a sulfuric acid refining system, condensing the crude concentrated sulfuric acid to 75 ℃ by a condenser, crystallizing to separate out an organic solid, performing suction filtration to obtain recovered concentrated sulfuric acid with the mass percentage concentration of 90% and solid waste, and recycling the recovered concentrated sulfuric acid to a nitric acid concentration stage.

Mixing the nitric acid smoke tail gas from the nitration reaction stage, the first nitric acid smoke tail gas from the product separation stage, the second nitric acid smoke tail gas from the nitric acid preconcentration stage, the third nitric acid smoke tail gas from the nitric acid concentration stage and the fourth nitric acid smoke tail gas from the nitric acid bleaching stage, then feeding the mixture into a nitric acid smoke absorption tower, absorbing nitric oxides in the nitric acid smoke tail gas by using fresh water to obtain nitric acid smoke absorption liquid with the mass concentration of 18% and waste gas, and feeding the nitric acid smoke absorption liquid and the nitration waste liquid into a nitric acid preconcentration system.

From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:

according to the treatment method, organic matter separation and preconcentration are carried out on the nitric acid containing high-boiling point organic matter, the recovered dilute nitric acid capable of being concentrated by adopting a sulfuric acid extraction method is obtained, the recovered concentrated nitric acid with the nitric acid concentration higher than the azeotropic concentration of nitric acid water can be obtained in the nitric acid concentration stage, zero emission of the waste nitric acid is realized, and the problems of safety, environmental protection and cost caused by treatment of the waste nitric acid are solved. Furthermore, the higher the content of organic, in particular nitro compounds in nitric acid or sulfuric acid during the distillation or rectification operation, the more dangerous the operation is, according to the general knowledge of the person skilled in the art. According to the method, firstly, the waste dilute nitric acid containing high-boiling-point organic matters is diluted to a lower concentration, most of the organic matters are separated in a solid-liquid separation mode, more organic matters are prevented from entering a concentration stage, and the safety of the concentration stage is preliminarily ensured; then, a pre-concentration process is set before sulfuric acid participates in nitric acid concentration, so that the content of organic matters in waste dilute nitric acid is greatly reduced while nitric acid pre-concentration is realized, the energy-saving effect is achieved, and meanwhile, the safety of a concentration stage is further ensured; the sulfuric acid refining process is set in the process of mechanically applying sulfuric acid, so that organic solid impurities separated out in the sulfuric acid concentration process are removed, the enrichment of the organic solid impurities and the carbonization and coking of organic matters in the sulfuric acid concentration process are avoided, the quality and the utilization rate of the sulfuric acid are ensured, and the safety of the concentration stage is further ensured. The safety problem of the nitric acid applying process can be thoroughly solved through the synergistic effect of the processes. Therefore, the recovered concentrated nitric acid and the recovered concentrated sulfuric acid obtained by the treatment method meet the recycling requirement.

The technical scheme disclosed by the invention has the advantages that the waste dilute nitric acid is concentrated to obtain the recovered concentrated nitric acid for substituted benzoic acid nitration and other conventional purposes, the zero emission of the waste nitric acid is realized, the recovered waste water jacket generated in the pre-concentration stage of the waste dilute nitric acid is used for dilution and filtration in the pre-concentration stage and dilution and filtration in the organic matter separation stage, and the waste water generated in the sulfuric acid concentration stage can be used as an absorbent for absorbing the nitric acid smoke, so that the discharge of the waste water is greatly reduced; in the organic matter separation stage, the nitric acid to be treated is directly diluted to a lower concentration and then an organic product is separated, or the nitric acid is firstly subjected to solid-liquid separation and then diluted to a lower concentration and then the organic product is separated to the maximum extent, and a nitration product is further separated in the waste dilute nitric acid preconcentration stage, so that the waste of the organic product is greatly reduced, and the discharge of waste solids is reduced; the nitric acid smoke absorption liquid obtained by absorbing and treating the nitric acid smoke tail gas generated in the operation processes of organic matter separation, nitric acid preconcentration, nitric acid concentration, nitric acid bleaching and the like is concentrated and then participates in nitric acid application, and the emission of waste gas is greatly reduced.

According to the technical scheme disclosed by the invention, the recovered concentrated nitric acid which can be used for substituted benzoic acid nitration and other conventional purposes is obtained after the waste dilute nitric acid is subjected to concentration treatment, the zero emission of the waste nitric acid is achieved, and the resource saving is realized at the same time, for example, in the substituted benzoic acid nitration reaction, the mass of the nitric acid is excessive by 1-4 times, in the production process, the residual waste nitric acid generated in the substituted benzoic acid nitration process is recovered and reused after the concentration treatment to be directly used as waste acid for treatment, and when the substituted benzoic acid consumes 1000 tons, at least 1000 tons of nitric acid are saved.

The method for treating the nitric acid containing the high-boiling-point organic matters, provided by the invention, has the advantages of simple process, convenience in operation, safety and environmental friendliness.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for processing nitric acid containing high-boiling point organic matters is characterized in that the high-boiling point organic matters are any one or more compounds shown in a general formula I,

the processing method comprises the following steps:

step S1, performing solid-liquid separation on the nitric acid containing the high-boiling-point organic matters to obtain a first high-boiling-point organic matter product, waste dilute nitric acid and first nitric acid smoke tail gas;

step S2, pre-concentrating the waste dilute nitric acid to obtain recovered waste water, recovered dilute nitric acid and second nitric acid smoke tail gas, wherein the concentration of nitric acid in the recovered waste water is lower than that in the recovered dilute nitric acid;

step S3, concentrating the recovered dilute nitric acid by a sulfuric acid method to obtain recovered concentrated nitric acid, a sulfuric acid aqueous solution and a third nitric acid smoke tail gas;

step S4, concentrating the sulfuric acid aqueous solution to obtain waste water and crude concentrated sulfuric acid; and

and S5, refining the crude concentrated sulfuric acid to obtain recovered concentrated sulfuric acid and solid waste, wherein the recovered concentrated sulfuric acid is returned to the step S3 to be used as sulfuric acid for concentrating the recovered dilute nitric acid by a sulfuric acid method.

2. The processing method according to claim 1, wherein the step S1 includes:

diluting the nitric acid containing the high-boiling-point organic matters to separate out the high-boiling-point organic matters to obtain a diluted nitric acid system to be treated;

performing solid-liquid separation on the diluted nitric acid system to be treated to obtain the first high boiling point organic product, the waste dilute nitric acid and the first nitric acid smoke tail gas,

preferably, the concentration of nitric acid in the diluted nitric acid system to be treated is 20-55%, and the recovered wastewater of the step S2 is preferably used as at least part of diluent to dilute the nitric acid containing the high-boiling point organic matters.

3. The processing method according to claim 1, wherein the step S1 includes:

carrying out first solid-liquid separation on the nitric acid containing the high-boiling-point organic matters to obtain a part of first high-boiling-point organic matter products, a separation mother liquor and a part of first smoke tail gas;

diluting the separated mother liquor to separate out the high-boiling-point organic matters in the separated mother liquor to obtain diluted mother liquor;

carrying out solid-liquid separation on the diluted mother liquor to obtain the waste dilute nitric acid, the residual first high-boiling-point organic product and the residual first nitric acid smoke tail gas,

preferably, the concentration of nitric acid in the diluted mother liquor is 20-55%, and the recovered wastewater of the step S2 is preferably used as at least part of diluent to dilute the separated mother liquor.

4. The processing method according to claim 1, wherein the step S2 includes:

rectifying the waste dilute nitric acid by using a rectifying tower, obtaining the recovered waste water at the tower top, obtaining a concentrated solution at the tower bottom, obtaining the recovered dilute nitric acid and the second nitric acid smoke tail gas at the side line of the rectifying tower, preferably, the concentration of the nitric acid in the recovered dilute nitric acid is less than or equal to 5%, preferably, the concentration of the nitric acid in the recovered dilute nitric acid is not higher than the azeotropic concentration of nitric acid water, and the mass content of organic matters is not higher than 0.1%, and preferably, the concentration of the nitric acid in the concentrated solution is not lower than the concentration of the nitric acid in the waste dilute nitric acid and is not higher than the azeotropic concentration of;

and (3) diluting the concentrated solution, and performing solid-liquid separation to obtain a separated solution and a second high-boiling-point organic product, preferably, the concentration of the nitric acid after the concentrated solution is diluted is not lower than 20%, preferably, the separated solution is returned to the rectification treatment step to be subjected to rectification treatment together with the waste dilute nitric acid, preferably, the recovered wastewater is used as at least part of diluent to dilute the concentrated solution, or the concentrated solution is returned to the step S1 to perform solid-liquid separation.

5. The processing method according to claim 1, wherein the step S2 includes:

distilling the waste dilute nitric acid to obtain the recovered waste water at the tower top and dilute nitric acid at the tower bottom, preferably, the concentration of the nitric acid in the recovered waste water is less than or equal to 5 percent, and the concentration of the nitric acid in the dilute nitric acid is not lower than that of the nitric acid in the waste dilute nitric acid and is not higher than the azeotropic concentration of the nitric acid water;

rectifying the dilute nitric acid to obtain the recovered dilute nitric acid and the second nitric acid smoke tail gas at the tower top, and obtaining a concentrated solution at the tower bottom, wherein preferably, the concentration of the nitric acid in the recovered dilute nitric acid is not higher than the azeotropic concentration of nitric acid water, and the mass content of organic matters is not higher than 0.1%, and preferably, the concentration of the nitric acid in the concentrated solution is not lower than the concentration of the nitric acid in the waste dilute nitric acid and is not higher than the azeotropic concentration of the nitric acid water;

and (3) diluting the concentrated solution, and performing solid-liquid separation to obtain a separated solution and a second high-boiling-point organic product, preferably, the concentration of the nitric acid after the concentrated solution is diluted is not lower than 20%, preferably, the separated solution is returned to the distillation treatment step to perform the distillation treatment together with the waste dilute nitric acid, preferably, the recovered wastewater is used as at least part of diluent to perform the dilution treatment on the concentrated solution, or the concentrated solution is returned to the step S1 to perform solid-liquid separation.

6. The processing method according to claim 1, wherein the step S2 includes:

distilling the waste dilute nitric acid by using a distillation tower, obtaining the recovered waste water at the tower top, obtaining a concentrated solution at the tower bottom, obtaining heavy components at the side line of the distillation tower, preferably, the concentration of the nitric acid in the recovered waste water is less than or equal to 5%, and the concentration of the nitric acid in the concentrated solution is not lower than that of the nitric acid in the waste dilute nitric acid and not higher than the azeotropic concentration of the nitric acid;

rectifying the heavy component by using a rectifying tower, obtaining the recovered dilute nitric acid and the second nitric acid smoke tail gas at the tower top, obtaining dilute nitric acid at the tower bottom, preferably selecting the concentration of nitric acid in the recovered dilute nitric acid to be not higher than the azeotropic concentration of nitric acid water and the mass content of organic matters to be not higher than 0.1%, preferably selecting the concentration of nitric acid in the dilute nitric acid to be not lower than the concentration of nitric acid in the concentrated solution and to be not higher than the azeotropic concentration of nitric acid water, and preferably returning the dilute nitric acid to the distillation treatment to carry out distillation treatment together with the waste dilute nitric acid;

7. The treatment method according to claim 1, wherein in the step S3, fresh concentrated sulfuric acid and the recovered concentrated sulfuric acid are used together as an extraction medium to concentrate the recovered dilute nitric acid to obtain recovered concentrated nitric acid, a sulfuric acid aqueous solution and a third nitric acid smoke tail gas, preferably, the concentration of the fresh concentrated sulfuric acid is 80-98%, preferably, the mass ratio of the extraction medium to the recovered dilute nitric acid is 1.5-4: 1, preferably, the concentration of the recovered concentrated nitric acid is not lower than 80%, and preferably, the concentration of the sulfuric acid aqueous solution is 70-80%.

8. The treatment method of claim 1, further comprising bleaching the recovered concentrated nitric acid to obtain bleached concentrated nitric acid and a fourth flue gas.

9. The treatment method according to claim 8, further comprising a step of performing absorption treatment on the first, second, third and fourth nitrate tail gases to obtain a nitrate smoke absorption liquid and a waste gas, preferably performing the absorption treatment by using at least part of the wastewater of step S4 as at least part of an absorbent, and preferably setting the concentration of nitric acid in the nitrate smoke absorption liquid to be 10-40%.

10. The treatment method according to claim 1, wherein the mass percentage concentration of the sulfuric acid in the wastewater is not higher than 2%, and the mass percentage concentration of the sulfuric acid in the crude concentrated sulfuric acid is 80-96%, preferably the step S5 comprises:

condensing the crude concentrated sulfuric acid to 60-90 ℃, and crystallizing to separate out an organic solid to obtain a condensation system;

and carrying out solid-liquid separation on the condensation system to obtain the recovered concentrated sulfuric acid and the solid waste.

11. A process for preparing a substituted nitrobenzoic acid, comprising:

mixing substituted benzoic acid with concentrated nitric acid, and carrying out nitration reaction to obtain nitration reaction liquid and smoke tail gas, wherein the nitration reaction liquid has high boiling point organic matters shown in a general formula I, the nitric acid concentration of the concentrated nitric acid is not lower than 80%, and the substituted benzoic acid has a structure shown in a general formula II:

treating the nitration reaction liquid by the treatment method according to any one of claims 1 to 10.

12. The process according to claim 11, characterized in that the concentrated nitric acid used for the nitration comes from recovered concentrated nitric acid and/or fresh concentrated nitric acid obtained in the treatment process, or

The treatment method further comprises the step of bleaching the recovered concentrated nitric acid to obtain bleached concentrated nitric acid and fourth nitric acid tail gas, wherein the concentrated nitric acid used for the nitration reaction is obtained from the bleached concentrated nitric acid and/or fresh concentrated nitric acid obtained in the treatment method.

13. The method according to claim 11, wherein the feeding mass ratio of the concentrated nitric acid to the substituted benzoic acid is 2-5: 1, and the reaction temperature is-30-60 ℃.

14. A nitric acid treatment system containing high-boiling point organic matters is characterized in that the high-boiling point organic matters are any one or more compounds shown in a general formula I,

the processing system comprises:

the solid-liquid separation unit (10) is used for carrying out solid-liquid separation on the nitric acid containing the high-boiling-point organic matters to obtain a first high-boiling-point organic matter product, waste dilute nitric acid and first nitric acid smoke tail gas, and the solid-liquid separation unit (10) is provided with a nitric acid inlet to be treated, a waste dilute nitric acid outlet and a first nitric acid smoke tail gas outlet;

the nitric acid pre-concentration unit (20) is used for pre-concentrating the waste dilute nitric acid, the nitric acid pre-concentration unit (20) is provided with a waste dilute nitric acid inlet, a recycled dilute nitric acid outlet, a recycled wastewater outlet and a second nitric acid smoke tail gas outlet, and the waste dilute nitric acid inlet is connected with the waste dilute nitric acid outlet;

the sulfuric acid method nitric acid concentration unit (30) is used for concentrating the recovered dilute nitric acid by adopting a sulfuric acid method, the sulfuric acid method nitric acid concentration unit (30) is provided with a concentrated sulfuric acid inlet, a recovered dilute nitric acid inlet, a recovered concentrated nitric acid outlet, a sulfuric acid water solution outlet and a third nitric acid smoke tail gas outlet, and the recovered dilute nitric acid inlet is connected with the recovered dilute nitric acid outlet;

the sulfuric acid concentration unit (40) is used for concentrating the sulfuric acid aqueous solution, the sulfuric acid concentration unit (40) is provided with a sulfuric acid aqueous solution inlet, a waste water outlet and a crude concentrated sulfuric acid outlet, and the sulfuric acid aqueous solution inlet is connected with the sulfuric acid aqueous solution outlet and is connected with the sulfuric acid method nitric acid concentration unit (30); and

a sulfuric acid refining unit (50) for refining the crude concentrated sulfuric acid, wherein the sulfuric acid refining unit (50) is provided with a crude concentrated sulfuric acid inlet, a recovered concentrated sulfuric acid outlet and a solid waste outlet, the crude concentrated sulfuric acid inlet is connected with the crude concentrated sulfuric acid outlet, and the recovered concentrated sulfuric acid outlet is connected with the concentrated sulfuric acid inlet so as to convey the recovered concentrated sulfuric acid to the sulfuric acid method nitric acid concentration unit (30).

15. The treatment system according to claim 14, wherein the solid-liquid separation unit (10) comprises:

a first dilution unit having a first diluent inlet and a post-dilution system outlet;

the first solid-liquid separation device is provided with a to-be-separated system inlet, a waste dilute nitric acid outlet and a first nitric acid smoke tail gas outlet, the diluted system outlet is connected with the to-be-separated system inlet, and preferably, the recycled wastewater outlet is connected with the first diluent inlet.

16. The treatment system according to claim 14, wherein the solid-liquid separation unit (10) comprises:

the second solid-liquid separation device is provided with a separation mother liquid outlet and a first smoke tail gas outlet A;

the second diluting device is provided with a second diluent inlet, a separated mother liquor inlet and a diluted mother liquor outlet, and the separated mother liquor inlet is connected with the separated mother liquor outlet;

and the third solid-liquid separation device is provided with a mother liquor inlet to be separated, a waste dilute nitric acid outlet and a first nitric acid smoke tail gas outlet B, the diluted mother liquor outlet is connected with the mother liquor inlet to be separated, and preferably, the recovered waste water outlet is connected with the second diluent inlet.

17. The treatment system according to claim 14, wherein the nitric acid pre-concentration unit (20) comprises:

a first rectifying tower (21) provided with the waste dilute nitric acid inlet, the recovered dilute nitric acid outlet and the second nitric acid smoke tail gas outlet, the tower top is provided with the recovered waste water outlet, and the tower bottom is provided with a concentrated solution outlet;

the concentrated solution outlet is connected with the nitric acid inlet to be treated,

or the nitric acid preconcentration unit (20) further comprises:

a third dilution unit (22) having a concentrate inlet, a third diluent inlet, and a diluted concentrate outlet, the concentrate inlet being connected to the concentrate outlet;

and the fourth solid-liquid separation device (23) is provided with a concentrated solution inlet to be separated and a separated solution outlet, the concentrated solution inlet to be separated is connected with the concentrated solution outlet after dilution, preferably, the separated solution outlet is connected with the waste dilute nitric acid inlet, and preferably, the recycled wastewater outlet is connected with the third diluent inlet.

18. The treatment system according to claim 14, wherein the nitric acid pre-concentration unit (20) comprises:

a first distillation column (24) having an inlet for said spent dilute nitric acid, an outlet for said recovered wastewater at the top of the column, and an outlet for dilute nitric acid at the bottom of the column;

a second rectifying tower (25) with an outlet for the recovered dilute nitric acid and an outlet for the second nitric acid smoke tail gas at the top and an outlet for the concentrated solution at the bottom;

or the nitric acid preconcentration unit (20) further comprises:

19. The treatment system according to claim 14, wherein the nitric acid pre-concentration unit (20) comprises:

a second distillation column (26) having an inlet for said spent dilute nitric acid and an outlet for heavies, an outlet for said recovered waste water at the top of the column and an outlet for concentrate at the bottom of the column;

a third rectifying tower (27), wherein the top of the tower is provided with the outlet for recovering the dilute nitric acid and the outlet for the tail gas of the second nitric acid smoke, and the bottom of the tower is provided with a dilute nitric acid outlet, and preferably, the dilute nitric acid outlet is connected with the inlet for the waste dilute nitric acid;

or the nitric acid preconcentration unit (20) further comprises:

20. The treatment system of claim 14, wherein the sulfuric acid process nitric acid concentration unit (30) comprises:

the concentration device is provided with the concentrated sulfuric acid inlet, the recovered dilute nitric acid inlet, the recovered concentrated nitric acid outlet, the sulfuric acid aqueous solution outlet and the third nitric acid smoke tail gas outlet;

the fresh concentrated sulfuric acid supply device is connected with the concentrated sulfuric acid inlet.

21. The treatment system according to claim 14, further comprising a bleaching unit connected to the recovered concentrated nitric acid outlet for bleaching the recovered concentrated nitric acid from the sulfuric acid process nitric acid concentration unit (30) to obtain bleached concentrated nitric acid and a fourth flue gas.

22. The treatment system according to claim 21, wherein the bleaching unit has a fourth nitrate tail gas outlet, the treatment system further comprising a nitrate tail gas absorption unit having an absorbent inlet and a nitrate tail gas inlet, the first, second, third and fourth nitrate tail gas outlets each being connected to the nitrate tail gas inlet, preferably the wastewater outlet being connected to the absorbent inlet.

23. The treatment system according to claim 14, wherein the sulfuric acid refining unit (50) comprises:

the condensing device is provided with a crude concentrated sulfuric acid inlet and a condensing system outlet;

and the fifth solid-liquid separation device is provided with a condensation system inlet and a concentrated sulfuric acid recovery outlet, and the condensation system inlet is connected with the condensation system outlet.

24. An apparatus for preparing a substituted nitrobenzoic acid, comprising:

the nitration reaction system (01) is used for carrying out nitration reaction after the substituted benzoic acid and the concentrated nitric acid are mixed to obtain nitration reaction liquid and nitric acid smoke tail gas, and is provided with a nitration reaction liquid outlet, wherein the nitration reaction liquid has high boiling point organic matters shown in a general formula I, the nitric acid concentration of the concentrated nitric acid is not lower than 80%, and the substituted benzoic acid has a structure shown in a general formula II:

a nitration reaction liquid treatment system according to any one of claims 14 to 23, wherein the nitration reaction liquid outlet is connected with a nitric acid inlet to be treated of the treatment system.

25. The apparatus according to claim 24, wherein the nitration reaction system (01) comprises a reaction unit having a concentrated nitric acid inlet and the nitration reaction liquid outlet, and a concentrated nitric acid supply unit having a concentrated nitric acid outlet, a fresh concentrated nitric acid inlet, and a second concentrated nitric acid inlet, the concentrated nitric acid inlet being connected to the concentrated nitric acid outlet, the second concentrated nitric acid inlet being connected to the recovered concentrated nitric acid outlet of the nitration reaction liquid treatment system, or

The nitration liquid treatment system further comprises a bleaching unit, wherein the bleaching unit is connected with the recovered concentrated nitric acid outlet and is used for bleaching the recovered concentrated nitric acid obtained by the sulfuric acid method nitric acid concentration unit (30) to obtain bleached concentrated nitric acid and fourth nitric acid tail gas, the bleaching unit is provided with a bleached concentrated nitric acid outlet, and the bleached concentrated nitric acid outlet is connected with the second concentrated nitric acid inlet.