CN114262110A - Integrated synergic recovery method for sodium sulfate and methanol in wastewater from pirimiphos-methyl production - Google Patents
Integrated synergic recovery method for sodium sulfate and methanol in wastewater from pirimiphos-methyl production Download PDFInfo
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Abstract
The invention discloses an integrated synergic recovery method of sodium sulfate and methanol in waste water of pirimiphos-methyl production, which comprises the following steps: cooling the sodium sulfate wastewater to-5-10 ℃ for crystallization, performing solid-liquid separation at the temperature of less than or equal to 20 ℃, heating the obtained sodium sulfate decahydrate, distilling and concentrating, performing centrifugal treatment, leaching the obtained anhydrous sodium sulfate crude product with a sodium sulfate solution, performing centrifugal treatment, and drying to obtain a sodium sulfate solid, and further purifying hydrous methanol by using the sodium sulfate solid to obtain anhydrous methanol. According to the integrated synergic recovery method for sodium sulfate and methanol in the wastewater from the production of pirimiphos-methyl, provided by the invention, through combined treatment of cooling crystallization, low-temperature filtration, distillation concentration and leaching filtration, zero discharge of wastewater can be realized, the environment is improved, energy is saved, consumption is reduced, byproducts (sodium sulfate, methanol, xylene and water) can be synergistically recovered, and the economic benefit of enterprises is favorably improved.
Description
Technical Field
The invention belongs to the technical field of resource utilization of industrial byproducts and zero discharge of wastewater, and relates to an integrated cooperative recovery method of sodium sulfate and methanol in wastewater generated in pirimiphos-methyl production.
Background
Pirimiphos-methyl (alias Andeli, PP511) is a pyrimidine pesticide, and is a safe pesticide variety which is mainly recommended by the World Health Organization (WHO) and the Food and Agriculture Organization (FAO) of the United nations for grain storage and household sanitary pest control. Compared with high-toxicity aluminum phosphide, the pirimiphos-methyl has a wide insecticidal spectrum and a rapid effect, the pesticide effect can reach 45-70 weeks, and the pirimiphos-methyl gradually becomes an excellent substitute variety of high-toxicity organophosphorus pesticides. The pyrimidineol is a key intermediate synthesized in the production process of the pirimiphos-methyl, has high economic value, and the synthetic route is as follows:
the synthesis of the pyrimidineol takes dimethylbenzene and methanol as solvents to generate byproducts such as methanol, sodium sulfate, water and the like, and the methanol and the water are distilled and separated from a high-temperature reaction system in the reaction process to obtain hydrous methanol; meanwhile, after the reaction is finished, cooling the reaction solution to be below 100 ℃, adding dilute acid and water, fully stirring, and washing off by-product sodium sulfate, wherein the concentration of sodium sulfate in the washing water reaches 15-25%, so that the high-concentration sodium sulfate wastewater is called sodium sulfate wastewater.
At present, methanol is recovered by a rectification method, and wastewater (high-concentration sodium sulfate wastewater) generated by washing sodium sulfate enters a sewage treatment system, is mixed with other wastewater, is diluted in sodium sulfate concentration, and is subjected to comprehensive treatment. However, the rectification for recovering the methanol has high energy consumption and generates waste water; a large amount of sodium sulfate enters the waste water, which has great influence on the environment, wastes water resources and recoverable sulfate by-products. Therefore, an improved process is needed, which can realize zero discharge of wastewater, improve environment, save energy and reduce consumption, can synergistically recover byproducts (sodium sulfate, methanol, xylene and water), and is beneficial to improving the economic benefit of enterprises.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide an integrated synergistic recovery method of sodium sulfate and methanol in the wastewater from the production of pirimiphos-methyl, which can realize zero discharge of wastewater, improve the environment, save energy and reduce consumption, can synergistically recover byproducts (sodium sulfate, methanol, xylene and water) and is beneficial to improving the economic benefit of enterprises.
In order to solve the technical problems, the invention adopts the technical scheme that:
an integrated synergic recovery method of sodium sulfate and methanol in wastewater generated in pirimiphos-methyl production comprises the following steps:
(1) cooling the sodium sulfate wastewater to-5-10 ℃, and crystallizing;
(2) carrying out solid-liquid separation on the product obtained after crystallization in the step (1) at the temperature of less than or equal to 20 ℃ to obtain sodium sulfate decahydrate and filtrate I;
(3) heating the sodium sulfate decahydrate obtained in the step (2), distilling and concentrating, and centrifuging the obtained concentrate to obtain an anhydrous sodium sulfate crude product and a mother solution;
(4) leaching the anhydrous sodium sulfate crude product obtained in the step (3) by using a sodium sulfate solution, and centrifuging after leaching to obtain leaching solution and an anhydrous sodium sulfate solid;
(5) drying the anhydrous sodium sulfate solid obtained in the step (4) to obtain anhydrous sodium sulfate;
further comprising the following processes: mixing the anhydrous sodium sulfate obtained in the step (5) with hydrous methanol, and standing to obtain anhydrous methanol and sodium sulfate containing crystal water; and (4) returning the sodium sulfate containing crystal water to the step (3) for distillation and concentration.
In the above integrated synergic recovery method of sodium sulfate and methanol in wastewater from pirimiphos-methyl production, a further improvement is that in step (2), the subsequent treatment of the filtrate i further comprises: extracting the filtrate I by using an extracting agent to obtain a water phase and an extraction phase; the water phase is used as a raw material and returned to a synthesis section of the methyl pyrimidyl alcohol; distilling the extract phase to recover the extractant.
According to the integrated synergic recovery method of sodium sulfate and methanol in the wastewater from the production of pirimiphos-methyl, the extraction agent is xylene; the dosage of the extracting agent is 5-10% of the mass of the filtrate I.
The integrated synergic recovery method of sodium sulfate and methanol in the wastewater from the production of pirimiphos-methyl is further improved, and in the step (1), the crystallization time is 30-120 min.
In the integrated synergic recovery method of sodium sulfate and methanol in the wastewater from the production of pirimiphos-methyl, the further improvement is that in the step (3), the condensed water generated in the distillation concentration process is used as a raw material and returned to the synthesis section of pirimiphos-methyl; and (3) carrying out centrifugal treatment when the temperature of the concentrate is reduced to 35-40 ℃.
In the integrated synergic recovery method of sodium sulfate and methanol in the wastewater from the production of pirimiphos-methyl, the improvement is that in the step (4), the sodium sulfate solution is prepared from anhydrous sodium sulfate and water; the using amount of the sodium sulfate solution is 0.2-0.6 time of the mass of the crude anhydrous sodium sulfate to be leached; the mass concentration of the sodium sulfate solution is 5-25%; and (4) combining the leacheate with the mother liquor in the step (3) to form a filtrate II, returning to the step (1), mixing with the sodium sulfate wastewater, and continuing to crystallize.
The integrated synergic recovery method for sodium sulfate and methanol in the wastewater from the production of pirimiphos-methyl is further improved, wherein the filtrate II is recycled for crystallization, and is mixed with the filtrate I in the step (2) for subsequent treatment until the mass percentage of the pyrimidinol in the filtrate II exceeds 0.5%.
In the above integrated synergic recovery method of sodium sulfate and methanol in wastewater from pirimiphos-methyl production, a further improvement is that in step (5), the subsequent treatment of the anhydrous sodium sulfate comprises: as a commodity for direct sale, or as a raw material for the preparation of sodium sulfate solution, or as a desiccant for the dehydration of aqueous methanol.
The integrated synergic recovery method of sodium sulfate and methanol in the pirimiphos-methyl production wastewater is further improved, wherein the addition amount of the anhydrous sodium sulfate is 1.5-4 times of the mass of water contained in the water-containing methanol; the water content of the hydrous methanol is below 5%; the standing time is more than 30 min.
The integrated synergic recovery method of sodium sulfate and methanol in the pirimiphos-methyl production wastewater is further improved, wherein the addition amount of the anhydrous sodium sulfate is 1.5-3.5 times of the mass of water contained in the water-containing methanol; the water content of the hydrous methanol is 1-3%; the standing time is 30-60 min.
Compared with the prior art, the invention has the advantages that:
(1) according to the invention, anhydrous sodium sulfate with high purity (> 98%) can be obtained, the finally obtained sodium sulfate has high purity, and can be sold for external use, so that the salt benefit is remarkably improved.
(2) Compared with the mode of simply adopting evaporation concentration, the method of combining cooling crystallization and evaporation concentration can reduce the evaporation amount by 40-50 percent, thereby reducing the evaporation cost by more than 50 percent.
(3) In the invention, the recycled anhydrous sodium sulfate is directly used as the dehydrating agent for recycling the methanol, so that the production cost is reduced.
(4) The invention meets the resource recycling of industrial byproducts, can improve the environment and increase the economic benefit of enterprises.
(5) In the invention, the xylene used for impurity removal can be continuously used after regeneration treatment.
(6) In the invention, the wastewater after sodium sulfate recovery is subjected to impurity removal and is reused in the production process, so that zero discharge of the wastewater is realized.
Therefore, in the invention, through four steps of cooling crystallization, low-temperature filtration, distillation concentration and leaching filtration, the byproduct sodium sulfate of the pirimiphos-methyl can be recovered, the purity of the anhydrous sodium sulfate reaches above the industrial grade, meanwhile, the recovered anhydrous sodium sulfate is used as a dehydrating agent, the solvent and the byproduct methanol are recovered in one step, in addition, the light brine obtained after the recovery of the sodium sulfate is subjected to extraction treatment and the purified water generated by distillation is recycled for production, the whole process realizes the cooperative recovery of the sodium sulfate and the methanol and the recycling of wastewater, realizes the recycling of resources to the maximum extent, and reduces the treatment cost. The integrated synergic recovery method of sodium sulfate and methanol in the wastewater from the production of pirimiphos-methyl can realize zero discharge of wastewater, improve the environment, save energy and reduce consumption, can synergistically recover byproducts (sodium sulfate, methanol, xylene and water), and is beneficial to improving the economic benefit of enterprises.
Drawings
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.
FIG. 1 is a schematic diagram of an integrated synergistic recovery process of sodium sulfate and methanol in wastewater from pirimiphos-methyl production in example 1 of the present invention.
Detailed Description
The invention is further described below with reference to the drawings and specific preferred embodiments of the description, without thereby limiting the scope of protection of the invention.
The raw materials and instruments used in the following examples are all commercially available; the equipment and the preparation process are conventional equipment and conventional process unless otherwise specified.
Examples
An integrated synergic recovery method of sodium sulfate and methanol in wastewater generated in pirimiphos-methyl production comprises the following steps:
(1) cooling the sodium sulfate wastewater to-5-10 ℃, and crystallizing for 30-120 min; in the step, a large amount of water is frozen when the crystallization temperature is lower than-5 ℃, and the solubility of the sodium sulfate in the water is high when the crystallization temperature is higher than 10 ℃, so that the recovery rate of the sodium sulfate is low.
(2) Carrying out solid-liquid separation on the product obtained after crystallization in the step (1) at the temperature of less than or equal to 20 ℃ to obtain sodium sulfate decahydrate and filtrate I; the subsequent treatment of the filtrate I obtained also comprises: extracting the filtrate I by using an extracting agent (such as xylene, but not limited to xylene) according to the dosage of the extracting agent being 5-10% of the mass of the filtrate I to obtain a water phase and an extraction phase, returning the water phase as a raw material to a synthesis section of the methylpyrimidinol, distilling the extraction phase, recovering the extracting agent, and burning residual liquid after distillation. In this step, when the temperature of the solid-liquid separation is higher than 20 ℃, the hydrated sodium sulfate obtained by crystallization is melted, and the yield of sodium sulfate is reduced.
(3) Heating the sodium sulfate decahydrate obtained in the step (2), distilling and concentrating, and reducing the obtained concentrate (sodium sulfate concentrated solution) to 35-40 ℃ for centrifugal treatment to obtain an anhydrous sodium sulfate crude product and a mother solution; in this step, condensed water produced in the distillation concentration process is returned to the synthesis section of methylpyrimidinol as a raw material.
(4) And (3) leaching the anhydrous sodium sulfate crude product obtained in the step (3) by using a sodium sulfate solution with the mass concentration of 5% -25% according to the condition that the use amount of the sodium sulfate solution is 0.2-0.6 times of the mass of the anhydrous sodium sulfate crude product to be leached, and performing centrifugal treatment after leaching to obtain leaching solution and an anhydrous sodium sulfate solid. Combining the leacheate with the mother liquor in the step (3) to form a filtrate II, returning to the step (1), mixing with the sodium sulfate wastewater, continuing to crystallize, and mixing the filtrate II with the filtrate I in the step (2) for subsequent treatment when the mass percentage of the pyrimidinol in the leacheate exceeds 0.5% in the process of circulating crystallization by using the filtrate II.
(5) Drying the anhydrous sodium sulfate solid obtained in the step (4) to obtain anhydrous sodium sulfate; the subsequent treatment of anhydrous sodium sulfate comprises: as a commodity for direct sale, or as a raw material for the preparation of sodium sulfate solution, or as a desiccant for the dehydration of aqueous methanol.
Further comprising the following processes: mixing the anhydrous sodium sulfate obtained in the step (5) with hydrous methanol having a water content of 5% or less (e.g., a water content of 1% to 3%) in an amount of 1.5 to 4 times the mass of water contained in the hydrous methanol, standing for 30min or more (e.g., 30min to 60min) to obtain anhydrous methanol and sodium sulfate containing crystal water, and returning the sodium sulfate containing crystal water to the step (3) for distillation and concentration.
Example 1
An integrated synergic recovery method of sodium sulfate and methanol in wastewater from pirimiphos-methyl production is shown in figure 1 and comprises the following steps:
taking high-concentration sodium sulfate wastewater generated in a 2L pyrimidinol production workshop, and analyzing to obtain wastewater with 25% of sodium sulfate content; 1kg of aqueous methanol collected during the production of pyrimidinol was analyzed to have a water content of 2%. The process for recycling the sodium sulfate from the wastewater and realizing the wastewater reuse and methanol dehydration comprises the following steps:
(1) the high-concentration sodium sulfate wastewater is cooled to 2 ℃ under the stirring condition, crystallized for 60min and filtered under the condition of the temperature of 20 ℃ to obtain 1593g of wet solid (sodium sulfate decahydrate) and 829g of filtrate (filtrate I).
(2) Extracting the filtrate (filtrate I) obtained in the step (1) by 42g (5% of the filtrate mass) of xylene, recycling a raffinate water phase for synthesizing the pyrimidinol, and washing a by-product sodium sulfate in a synthetic reaction solution; meanwhile, after the extraction phase obtained after extraction is distilled, xylene (extractant) can be recovered, and the distilled residual liquid is burnt.
(3) Heating the wet solid (sodium sulfate decahydrate) obtained in the step (1) to 100 ℃, distilling and concentrating, stopping heating when 726g of water is distilled out, naturally cooling the obtained concentrate to 35 ℃ at room temperature, preserving heat, and filtering (centrifuging) to obtain a crude anhydrous sodium sulfate product and 269g of mother liquor. In this step, condensed water produced in the distillation concentration process is returned to the synthesis section of methylpyrimidinol as a raw material.
(4) Leaching and filtering (centrifuging) the anhydrous sodium sulfate crude product obtained in the step (3) by using 180g of sodium sulfate solution with the mass concentration of 5% to obtain 558g of anhydrous sodium sulfate solid (the water content is 4.8%) and leacheate, and combining and collecting the leacheate and the filtrate obtained in the step (3) to obtain 457g of filtrate II; the anhydrous sodium sulfate solid was dried at 100 ℃ to constant weight to give 531g of anhydrous sodium sulfate. In the step, 457g of the obtained filtrate II is kept at about 40 ℃ and placed to prevent crystallization hardening, or directly returned to the step (1) and mixed with sodium sulfate wastewater to continue crystallization. Meanwhile, after the filtrate II is circularly crystallized for a certain number of times, when the mass percentage content of the pyrimidineol in the filtrate (eluent) is detected to be over 0.5 percent, the filtrate II is mixed with the filtrate I in the step (2) for subsequent treatment (namely extraction and recovery of an extracting agent). In addition, in this step, the subsequent treatment of the anhydrous sodium sulfate obtained comprises: as a commodity for direct sale, or as a raw material for the preparation of sodium sulfate solution, or as a desiccant for the dehydration of aqueous methanol.
(5) 60g of the anhydrous sodium sulfate obtained in step (4) was added to 1kg of aqueous methanol having a water content of 2% to dehydrate, and the mixture was allowed to stand for 30min and filtered to obtain 81g of hygroscopic sodium sulfate (sodium sulfate containing crystal water) and methanol. In this step, the hygroscopic sodium sulfate (sodium sulfate containing crystal water) was returned to step (3), and distillation and concentration were continued with the hygroscopic solid (sodium sulfate decahydrate). Meanwhile, the methanol obtained in the step is returned to the stage of synthesizing the methylpyrimidinol as a raw material.
After analysis, the obtained anhydrous sodium sulfate accounts for 531g, and the content is 98%; the amount of purified methanol was 975g in total, and the water content was 0.1%.
Example 2
An integrated synergic recovery method of sodium sulfate and methanol in wastewater from pirimiphos-methyl production is shown in figure 1 and comprises the following steps:
taking high-concentration sodium sulfate wastewater generated in a 2L pyrimidinol production workshop, analyzing the sodium sulfate content in the wastewater to be 15%, and mixing the sodium sulfate wastewater with 457g of filtrate II obtained in the step (4) of the example 1; 1kg of aqueous methanol collected during the production of pyrimidinol was analyzed to have a water content of 1.8%.
(1) The high-concentration sodium sulfate wastewater (containing 457g of the filtrate II obtained in the step (4) of example 1) was stirred, cooled to-5 ℃, crystallized for 30min, and filtered at 15 ℃ to obtain 1275g of a wet solid (sodium sulfate decahydrate) and 1275g of a filtrate (filtrate I).
(2) Extracting the filtrate (filtrate I) obtained in the step (1) by using 102g (8% of the mass of the filtrate) of xylene, recycling a raffinate water phase for synthesizing the pyrimidinol, and washing a by-product sodium sulfate in a synthetic reaction solution; meanwhile, after the extraction phase obtained after extraction is distilled, xylene (extractant) can be recovered, and the distilled residual liquid is burnt.
(3) Heating the wet solid (sodium sulfate decahydrate) obtained in the step (1) to 100 ℃, distilling and concentrating, stopping heating when 748g of water is evaporated, naturally cooling the obtained concentrate to 40 ℃ at room temperature, preserving heat, and filtering (centrifuging) to obtain a crude anhydrous sodium sulfate product and 207g of mother liquor. In this step, condensed water produced in the distillation concentration process is returned to the synthesis section of methylpyrimidinol as a raw material.
(4) Preparing 200g of a sodium sulfate solution with the mass concentration of 10% by using the anhydrous sodium sulfate recovered in the example 1, leaching the crude anhydrous sodium sulfate obtained in the step (3) by using the sodium sulfate solution, filtering (centrifuging) the obtained mixture at 35 ℃ to obtain 320g of anhydrous sodium sulfate solid (with the water content of 4.7%) and leacheate, and combining and collecting the leacheate and the mother liquor obtained in the step (3) to obtain 407g of filtrate II; placing the anhydrous sodium sulfate solid at 100 ℃ and drying to constant weight to obtain 305g of anhydrous sodium sulfate; in the step, 407g of the obtained filtrate II is kept at about 40 ℃ for standing to prevent crystallization hardening, and the filtrate II is returned to the step (1) to be mixed with sodium sulfate wastewater for continuous crystallization. Meanwhile, after circularly crystallizing the filtrate II for a certain number of times, when detecting that the mass percentage content of the pyrimidinol in the filtrate (leacheate) exceeds 0.5 percent, mixing the filtrate II with the filtrate I in the step (2) for subsequent treatment. In addition, in this step, the subsequent treatment of the anhydrous sodium sulfate obtained comprises: as a commodity for direct sale, or as a raw material for the preparation of sodium sulfate solution, or as a desiccant for the dehydration of aqueous methanol.
(5) 60g of the anhydrous sodium sulfate obtained in step (4) was added to 1kg of aqueous methanol having a water content of 1.8% to dehydrate, and the mixture was allowed to stand for 30min and filtered to obtain 79.5g of hygroscopic sodium sulfate (sodium sulfate containing crystal water) and methanol. In this step, the sodium sulfate (sodium sulfate containing crystal water) having absorbed moisture was returned to step (3), and the mixture was further concentrated under reduced pressure with a moisture-containing solid (sodium sulfate decahydrate). Meanwhile, the methanol obtained in the step is returned to the stage of synthesizing the methylpyrimidinol as a raw material.
The analysis shows that the obtained anhydrous sodium sulfate accounts for 305g, and the content is 98.5%; 975g of methanol was obtained by purification, and the water content was 0.09%.
Example 3
An integrated synergic recovery method of sodium sulfate and methanol in wastewater from pirimiphos-methyl production is shown in figure 1 and comprises the following steps:
taking high-concentration sodium sulfate wastewater generated in a 2L pyrimidinol production workshop, and analyzing the wastewater to ensure that the content of sodium sulfate is 24 percent; 1kg of aqueous methanol collected during the production of pyrimidinol was analyzed for a water content of 2.1%.
(1) The high-concentration sodium sulfate wastewater is stirred, cooled to 10 ℃, crystallized for 120min and filtered at the temperature of 10 ℃ to obtain 1588g of wet solid (sodium sulfate decahydrate) and 878g of filtrate (filtrate I).
(2) Heating the wet solid (sodium sulfate decahydrate) obtained in the step (1) to 100 ℃, distilling and concentrating, stopping heating when 715g of water is evaporated, naturally cooling the obtained concentrate to 36 ℃ at room temperature, preserving heat, and filtering (centrifuging) to obtain a crude anhydrous sodium sulfate product and 293g of mother liquor. In this step, condensed water produced in the distillation concentration process is returned to the synthesis section of methylpyrimidinol as a raw material.
(3) Preparing 300g of a sodium sulfate solution with the mass concentration of 20% by using the anhydrous sodium sulfate recovered in the example 1, leaching the crude anhydrous sodium sulfate obtained in the step (2) by using the sodium sulfate solution, and filtering (centrifuging) to obtain 580g of anhydrous sodium sulfate solid (with the water content of 4.9%) and 309g of leacheate; placing the anhydrous sodium sulfate solid at 100 ℃ and drying to constant weight to obtain 552g of anhydrous sodium sulfate; in this step, the subsequent treatment of the anhydrous sodium sulfate obtained comprises: as a commodity for direct sale, or as a raw material for the preparation of a saturated sodium sulfate solution, or as a desiccant for the dehydration of aqueous methanol.
(4) And (3) combining the mother liquor obtained in the step (2) and the leacheate obtained in the step (3) to obtain 602g of filtrate II, and detecting that the mass percentage of the pyrimidinol in the filtrate II reaches 0.53%. Mixing the filtrate II with the filtrate I obtained in the step (1), extracting with 150g (10% of the total mass of the filtrate I and the filtrate II) of dimethylbenzene, recycling a raffinate water phase for synthesizing pyrimidineol, and washing a byproduct sodium sulfate in a synthetic reaction solution; meanwhile, after the extraction phase obtained after extraction is distilled, xylene (extractant) can be recovered, and the distilled residual liquid is burnt.
(5) 70g of the anhydrous sodium sulfate obtained in step (4) was added to 1kg of aqueous methanol having a water content of 2.1% to dehydrate the mixture, and the mixture was allowed to stand for 30min and filtered to obtain 92g of sodium sulfate after moisture absorption.
After analysis, the obtained anhydrous sodium sulfate is 552g in total, and the content is 98.8%; 975g of methanol was obtained by purification, and the water content was 0.09%.
Comparative example 1
A method for recovering sodium sulfate and methanol in wastewater from pirimiphos-methyl production omits the treatment of cooling crystallization and low-temperature filtration, and comprises the following steps:
(1) heating the 2-step-up concentration sodium sulfate wastewater to 100 ℃, carrying out distillation concentration, stopping heating when 1633g of water is distilled out, naturally cooling the obtained concentrate to 35 ℃ at room temperature, preserving heat, and filtering (centrifuging) to obtain a crude anhydrous sodium sulfate product and 288g of mother liquor.
(2) Leaching and filtering (centrifuging) the anhydrous sodium sulfate crude product obtained in the step (21) by using 180g of sodium sulfate solution with the mass concentration of 5% to obtain 559g of anhydrous sodium sulfate solid (the water content is 5%); the anhydrous sodium sulfate solid was dried at 100 ℃ to constant weight to give 528g of anhydrous sodium sulfate.
As a result: the obtained anhydrous sodium sulfate amounted to 528g and had a content of 95%.
Adverse effects: compared with the example 1, 907g of water is distilled out, and the energy consumption is higher; the impurities such as pyrimidinol, guanidine salt and the like in the wastewater are partially taken away by mother liquor and leacheate, and the other part of impurities is separated out simultaneously with anhydrous sodium sulfate after being distilled and concentrated, so that the content of the anhydrous sodium sulfate is reduced, the impurities are increased, and the quality of the anhydrous sodium sulfate cannot meet the quality standard of national industrial anhydrous sodium sulfate products.
Comparative example 2
A method for recovering sodium sulfate and methanol in wastewater from pirimiphos-methyl production, omitting distillation and concentration treatment, comprises the following steps:
(1) the high-concentration sodium sulfate wastewater is cooled to 2 ℃ under the stirring condition, crystallized for 60min and filtered at 20 ℃ to obtain 1593g of wet solid (sodium sulfate decahydrate) and 829g of filtrate (filtrate I).
(2) Extracting the filtrate (filtrate I) obtained in the step (1) by 42g (5% of the filtrate mass) of xylene, recycling a raffinate water phase for synthesizing the pyrimidinol, and washing a by-product sodium sulfate in a synthetic reaction solution; meanwhile, after the extraction phase obtained after extraction is distilled, xylene (extractant) can be recovered, and the distilled residual liquid is burnt.
(3) 1593g of the wet solid (sodium sulfate decahydrate) was dried at low temperature under reduced pressure to constant weight to give 568g of anhydrous sodium sulfate.
As a result: 568g of anhydrous sodium sulfate is obtained, and the content is 97%;
adverse effects: compared with the example 1, the sodium sulfate decahydrate obtained by cooling crystallization can be dehydrated only by air drying at low temperature or drying at reduced pressure and low temperature without distillation concentration process, because the wet sodium sulfate decahydrate can be quickly dissolved at a slightly high temperature (more than or equal to 40 ℃); and (3) taking away a part of impurities such as pyrimidyl alcohol, guanidinium and the like in the wastewater through cooling crystallization filtrate, remaining a part of impurities in the crystallization water containing wet sodium sulfate decahydrate and the wet water, drying the water, and separating out the impurities together with sodium sulfate, so that the content of anhydrous sodium sulfate is reduced, the impurities are increased, and the quality of the anhydrous sodium sulfate cannot meet the quality standard of national industrial anhydrous sodium sulfate products.
According to the embodiment, the methyl pyrimidine phosphorus by-product sodium sulfate can be recovered through four steps of cooling crystallization, low-temperature filtration, distillation concentration and leaching filtration, the purity of the anhydrous sodium sulfate reaches above the industrial grade, the recovered anhydrous sodium sulfate is used as a dehydrating agent, a solvent and a by-product methanol are recovered in one step, in addition, the light brine obtained after the recovery of the sodium sulfate is subjected to extraction treatment and purified water generated by distillation is recycled for production, the whole process realizes the cooperative recovery of the sodium sulfate and the methanol and the recycling of wastewater, the recycling of resources is realized to the greatest extent, and the treatment cost is reduced. The integrated synergic recovery method of sodium sulfate and methanol in the wastewater from the production of pirimiphos-methyl can realize zero discharge of wastewater, improve the environment, save energy and reduce consumption, can synergistically recover byproducts (sodium sulfate, methanol, xylene and water), and is beneficial to improving the economic benefit of enterprises.
The above examples are merely preferred embodiments of the present invention, and the scope of the present invention is not limited to the above examples. All technical schemes belonging to the idea of the invention belong to the protection scope of the invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention, and such modifications and embellishments should also be considered as within the scope of the invention.
Claims (10)
1. An integrated synergic recovery method of sodium sulfate and methanol in wastewater generated in pirimiphos-methyl production is characterized by comprising the following steps:
(1) cooling the sodium sulfate wastewater to-5-10 ℃, and crystallizing;
(2) carrying out solid-liquid separation on the product obtained after crystallization in the step (1) at the temperature of less than or equal to 20 ℃ to obtain sodium sulfate decahydrate and filtrate I;
(3) heating the sodium sulfate decahydrate obtained in the step (2), distilling and concentrating, and centrifuging the obtained concentrate to obtain an anhydrous sodium sulfate crude product and a mother solution;
(4) leaching the anhydrous sodium sulfate crude product obtained in the step (3) by using a sodium sulfate solution, and centrifuging after leaching to obtain leaching solution and an anhydrous sodium sulfate solid;
(5) drying the anhydrous sodium sulfate solid obtained in the step (4) to obtain anhydrous sodium sulfate;
further comprising the following processes: mixing the anhydrous sodium sulfate obtained in the step (5) with hydrous methanol, and standing to obtain anhydrous methanol and sodium sulfate containing crystal water; and (4) returning the sodium sulfate containing crystal water to the step (3) for distillation and concentration.
2. The integrated synergic recycling method of sodium sulfate and methanol in wastewater from pirimiphos-methyl production as claimed in claim 1, characterized in that, in the step (2), the subsequent treatment of the filtrate I further comprises: extracting the filtrate I by using an extracting agent to obtain a water phase and an extraction phase; the water phase is used as a raw material and returned to a synthesis section of the methyl pyrimidyl alcohol; distilling the extract phase to recover the extractant.
3. The integrated synergic recovery method of sodium sulfate and methanol in wastewater from the production of pirimiphos-methyl according to claim 2, characterized in that the extractant is xylene; the dosage of the extracting agent is 5-10% of the mass of the filtrate I.
4. The integrated synergic recovery method of sodium sulfate and methanol in pirimiphos-methyl production wastewater according to any one of claims 1 to 3, characterized in that, in the step (1), the time for crystallization is 30min to 120 min.
5. The integrated synergic recovery method of sodium sulfate and methanol in wastewater from the production of pirimiphos-methyl according to any of claims 1 to 3, characterized in that, in step (3), the condensed water generated in the distillation concentration process is returned to the synthesis section of pirimidyl alcohol as a raw material; and (3) carrying out centrifugal treatment when the temperature of the concentrate is reduced to 35-40 ℃.
6. The integrated synergic recovery method of sodium sulfate and methanol in industrial wastewater of pirimiphos-methyl according to any one of claims 1 to 3, characterized in that, in the step (4), the sodium sulfate solution is prepared from anhydrous sodium sulfate and water; the dosage of the sodium sulfate solution is 0.2-0.65 time of the mass of the crude anhydrous sodium sulfate to be leached; the mass concentration of the sodium sulfate solution is 5-25%; and (4) combining the leacheate with the mother liquor in the step (3) to form a filtrate II, returning to the step (1), mixing with the sodium sulfate wastewater, and continuing to crystallize.
7. The integrated synergic recovery method of sodium sulfate and methanol in wastewater from the production of pirimiphos-methyl as claimed in claim 6, characterized in that the filtrate II is recycled for crystallization, and is mixed with the filtrate I in step (2) for subsequent treatment until the mass percentage of pyrimidinol in the filtrate II exceeds 0.5%.
8. The integrated synergic recovery method of sodium sulfate and methanol in industrial wastewater of pirimiphos-methyl according to any one of claims 1 to 3, characterized in that, in the step (5), the subsequent treatment of the anhydrous sodium sulfate comprises: as a commodity for direct sale, or as a raw material for the preparation of sodium sulfate solution, or as a desiccant for the dehydration of aqueous methanol.
9. The integrated synergic recovery method of sodium sulfate and methanol in industrial wastewater of pirimiphos-methyl according to any one of claims 1 to 3, characterized in that the addition amount of the anhydrous sodium sulfate is 1.5 to 4 times of the mass of water contained in the aqueous methanol; the water content of the hydrous methanol is below 5%; the standing time is more than 30 min.
10. The integrated synergic recovery method of sodium sulfate and methanol in industrial wastewater of pirimiphos-methyl according to claim 9, characterized in that the addition amount of the anhydrous sodium sulfate is 1.5-3.5 times of the mass of water contained in the aqueous methanol; the water content of the hydrous methanol is 1-3%; the standing time is 30-60 min.
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| CN102060756A (en) * | 2010-11-23 | 2011-05-18 | 山东省医药工业研究所 | Method for preparing sodium picosulfate monohydrate |
| CN204079685U (en) * | 2014-07-25 | 2015-01-07 | 太仓塑料助剂厂有限公司 | A kind for the treatment of unit of high salinity high-COD waste water |
| CN112661703A (en) * | 2020-12-03 | 2021-04-16 | 湖南海利高新技术产业集团有限公司 | Method for extracting and recovering methyl pyrimidineol by using nitrogen heterocyclic functionalized ionic liquid |
| CN112850751A (en) * | 2021-01-09 | 2021-05-28 | 西北大学 | Method for recovering sodium sulfate in nicotine purification process |
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| CN102060756A (en) * | 2010-11-23 | 2011-05-18 | 山东省医药工业研究所 | Method for preparing sodium picosulfate monohydrate |
| CN204079685U (en) * | 2014-07-25 | 2015-01-07 | 太仓塑料助剂厂有限公司 | A kind for the treatment of unit of high salinity high-COD waste water |
| CN112661703A (en) * | 2020-12-03 | 2021-04-16 | 湖南海利高新技术产业集团有限公司 | Method for extracting and recovering methyl pyrimidineol by using nitrogen heterocyclic functionalized ionic liquid |
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