CN102649545A - Nitric acid pre-concentration method for waste acid concentration technology in production of dinitrotoluene - Google Patents
Nitric acid pre-concentration method for waste acid concentration technology in production of dinitrotoluene Download PDFInfo
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- CN102649545A CN102649545A CN2011103301609A CN201110330160A CN102649545A CN 102649545 A CN102649545 A CN 102649545A CN 2011103301609 A CN2011103301609 A CN 2011103301609A CN 201110330160 A CN201110330160 A CN 201110330160A CN 102649545 A CN102649545 A CN 102649545A
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Abstract
The invention discloses a nitric acid pre-concentration method for waste acid concentration technology in production of dinitrotoluene, which comprises the steps of: leading waste acid coming from the washing process and/ or acid steam coming from the waste acid steam stripping process in a nitration system to enter a rectifying tower for vacuum rectification, then using a reboiler for vaporization, and obtaining products after concentration; sending the products obtained after concentration back into the nitration system; controlling the tower top temperature of the rectifying tower to be within the range of 73-78 DEG C and the tower bottom temperature of the rectifying tower to be within the range of 95-103 DEG C; leading gas phase arranged on the top of the rectifying tower to enter a first-stage condenser for condensation, sending first-stage condensate back into the top of the rectifying tower, and taking the first-stage condensate as reflux liquid, wherein the reflux ratio is 0.18-0.2; taking the rest stage condensate as waste water to be discharged; leading the tail gas of the first-stage condenser to enter a second-stage condenser for condensation, and sending all second-stage condensate back into the rectifying tower; and controlling the second-stage condensate to enter the rectifying tower at a rectifying section with the temperature of 80-82 DEG C. According to the nitric acid pre-concentration method, the content of nitric acid in the waste water can be reduced to less than 1%, so that the cost is greatly reduced, and the environmental pollution is reduced.
Description
Technical field
The present invention relates to the working method of DNT, be specifically related to the nitric acid pre-concentration method of spent acid concentration technology in the DNT production.
Background technology
At present, in the working method of DNT, from the spent acid of the washing procedure of nitrification; Wherein the weight content of nitric acid is 18～20%, and the vitriolic weight content is 5～8%, contains the DNT of The dissolved simultaneously; Oxynitride etc. get into rectifying tower and carry out rectifying.In rectifying tower; Operation under vacuum condition, the sulfuric acid that contains in the spent acid change the azeotropic point of nitric acid as extraction agent; The DNT of nitric acid, sulfuric acid and The dissolved after the outlet of the reboiler at the bottom of the rectifying Tata obtains concentrating is again by being pumped back to nitrification.
It is water, a small amount of nitric acid, DNT, nitrogen peroxide and nitrogen protoxide etc. that rectifying tower cat head gas phase is mainly formed.In first-stage condenser, with the water condensation in the cat head gas phase, this phlegma finally effluxes processing as nitric acid preconcentration technique waste water, the nitric acid in the further condensation gas phase of secondary condenser, and this phlegma returns the phegma of rectifying tower as cat head.The gas phase of secondary condenser gets into vacuum pump, finally gets into the tail gas absorption technology unit.
There is a defective in above-mentioned method: the nitric acid content in the phlegma of first-stage condenser fails to reach wastewater discharge standard at 1.5～3wt%, has therefore increased the expense of wastewater treatment.In addition, because raw material nitric acid runs off in waste water greater than value, this has also caused the increase of product cost.Actual nitric acid content in the B-grade condensation liquid is at 7～12wt% simultaneously, and far above Design Theory value 3%, this doubt is present in the nitric acid pre-concentration method all the time all the time.
Summary of the invention
The nitric acid content that technical problem to be solved by this invention has been to overcome in the phlegma that spent acid concentration technology in the existing DNT production can cause first-stage condenser is high; Thereby increased the expense of wastewater treatment and the defective of production cost, the nitric acid pre-concentration method of spent acid concentration technology in a kind of DNT production is provided.This method can make that the content of nitric acid reaches wastewater discharge standard in the waste water, has significantly reduced the production cost of DNT.
The invention provides the nitric acid pre-concentration method of spent acid concentration technology in a kind of DNT production, it comprises the steps:
Sour vapour from the spent acid of the washing procedure of nitrification and/or spent acid stripping process is got in the rectifying tower under the vacuum tightness of 60～64kPa, carry out rectification under vacuum; Reboiler at the bottom of being arranged at said rectifying Tata vaporize concentrated after product, said concentrated after product is sent back to nitrification; The tower top temperature of said rectifying tower is 73～78 ℃, and column bottom temperature is 95～103 ℃;
Wherein, the gas phase that is arranged in the cat head of said rectifying tower gets into first-stage condenser and carries out condensation, the one-level phlegma, send said one-level phlegma the cat head of said rectifying tower back to, as first phegma of said rectifying tower, reflux ratio is 0.18～0.2; Remaining one-level phlegma effluxes processing as the waste water of nitric acid preconcentration technique; The remaining one-level phlegma and the first phegma sum are said one-level phlegma;
The tail gas of said first-stage condenser gets into secondary condenser again; Carry out condensation and get B-grade condensation liquid; All send said B-grade condensation liquid back to said rectifying tower as second phegma, said B-grade condensation liquid locates to get into rectifying tower 80～82 ℃ of the rectifying section of said rectifying tower.
Wherein, described rectifying tower preferably is a packing tower.The theoretical plate number of said packing tower preferably is 8～12, more preferably is 10.
Wherein, nitric acid and vitriolic content are the conventional content of this area in the spent acid of said washing procedure from nitrification, and nitric acid content is generally 18～20wt%, and sulfuric acid content is generally 5～8wt%.
Wherein, nitric acid and vitriolic content are the conventional content of this area in the sour vapour of said spent acid stripping process, and nitric acid content is generally 10～12wt%, and sulfuric acid content is generally 0.2～0.5wt%.
Wherein, nitric acid content generally is controlled at 45～50wt% in the said concentrated after product, and sulfuric acid content generally is controlled at 5～10wt%.
Wherein, the condensation in the said first-stage condenser can adopt the routine operation condition of this area to carry out, and preferably under 72～74 ℃, carries out.
Wherein, the condensation in the said secondary condenser can adopt the routine operation condition of this area to carry out, and preferably under 58～62 ℃, carries out.
On the basis that meets this area general knowledge, but above-mentioned each optimum condition arbitrary combination promptly gets each preferred embodiments of the present invention.
All commercially available the getting of reagent, raw material and equipment that the present invention uses.
Positive progressive effect of the present invention is:
1, adopt nitric acid pre-concentration method of the present invention that nitric acid content is reduced to below 1% from original about 2%; Reduced the pollution of environment and the loss of nitric acid; For the production equipment of producing 190000 tons of DNTs per year, 550 tons in annual recyclable nitric acid.
2, from the energy point of view analysis; Because nitric acid content is much smaller than original design in the rectifying tower trim the top of column liquid, so quantity of reflux reduces greatly, the energy of reboiler will reduce to some extent; Make the heat and the cold of nitric acid preconcentration technique all reduce to some extent, meet the requirement of energy-saving and emission-reduction.
Description of drawings
Fig. 1 is the schema of the inventive method.
Fig. 2 is the schema of existing nitric acid concentrating means.
Embodiment
Further specify the present invention with embodiment below, but the present invention is not limited, the raw material among the embodiment is conventional commercially available prod.
Referring to Fig. 1, will get into rectifying tower 1 from the sour vapour of the spent acid of the washing procedure of nitrification and/or spent acid stripping process and carry out rectifying, the product that the reboiler outlet at the bottom of the rectifying Tata obtains after concentrating sends back to nitrification again;
The gas phase of rectifying tower 1 cat head gets into first-stage condenser 2, then the one-level phlegma is sent back to the cat head of rectifying tower 1, and as first phegma of rectifying tower 1, remaining phlegma effluxes processing as nitric acid preconcentration technique waste water;
The tail gas of first-stage condenser 2 gets into secondary condenser 3 again, then with B-grade condensation liquid as second phegma, all send rectifying tower 1 back to, this B-grade condensation liquid locates to get into rectifying tower 1 80～82 ℃ of the rectifying section of rectifying tower 1.
Embodiment 1
Adopt the flow process of Fig. 1.
Rectifying tower adopts packing tower, and theoretical plate number is 10.
From the spent acid of the washing procedure of nitrification, flow is 4100 kilograms/hour, and wherein the content of nitric acid is 20wt%, and vitriolic content is 8wt%.From the sour vapour of spent acid stripping process, flow is 7020 kilograms/hour, and wherein nitric acid content is at 12wt%, and sulfuric acid content is at 0.2wt%.
Above-mentioned spent acid and sour vapour are sent into rectifying tower 1, under 60kPa vacuum tightness, carry out rectifying, tower top temperature is 76 ℃; 99 ℃ of column bottom temperatures; Reboiler at the bottom of the rectifying Tata exports the product after the concentrating of obtaining, and wherein nitric acid content is at 50wt%, and sulfuric acid content is at 10wt%; Send back to nitrification again, flow is 3480 kilograms/hour;
The gas phase of rectifying tower 1 cat head gets into first-stage condenser 2, under 73 ℃, carries out condensation and gets the one-level phlegma, then the one-level phlegma is sent back to the cat head of rectifying tower 1, and as first phegma of rectifying tower 1, reflux ratio is 0.19; Remaining one-level phlegma is effluxed processing as nitric acid preconcentration technique waste water, and flow is 7530 kilograms/hour, and wherein, the content of nitric acid is 1wt%;
The tail gas of this first-stage condenser 2 gets into secondary condenser 3 again; Under 60 ℃, carry out condensation and get B-grade condensation liquid; All send B-grade condensation liquid back to rectifying tower 1 as second phegma then, this B-grade condensation liquid locates to get into rectifying tower 1 81 ℃ of the rectifying section of rectifying tower 1.
Adopt the flow process of Fig. 1.
Rectifying tower adopts packing tower, and theoretical plate number is 10.
From the spent acid of the washing procedure of nitrification, flow is 4100 kilograms/hour, and wherein the weight content of nitric acid is 18wt%, and the vitriolic weight content is 5wt%.From the sour vapour of spent acid stripping process, flow is 7020 kilograms/hour, and wherein nitric acid content is 12wt%, and sulfuric acid content is 0.5wt%.
Above-mentioned spent acid and sour vapour are sent into rectifying tower 1, under 64kPa vacuum tightness, carry out rectifying, tower top temperature is 73 ℃; Column bottom temperature is 96 ℃; Reboiler at the bottom of the rectifying Tata exports the product after the concentrating of obtaining, and wherein nitric acid content is 45wt%, and sulfuric acid content is 5wt%; Send back to nitrification again, flow is 3460 kilograms/hour;
The gas phase of rectifying tower 1 cat head gets into first-stage condenser 2, under 73 ℃, carries out condensation and gets the one-level phlegma, then the one-level phlegma is sent back to the cat head of rectifying tower 1, and as first phegma of rectifying tower 1, reflux ratio is 0.19; Remaining one-level phlegma is effluxed processing as nitric acid preconcentration technique waste water, and flow is 7550 kilograms/hour, and wherein, the content of nitric acid is 0.9wt%;
The tail gas of first-stage condenser 2 gets into secondary condenser 3 again, under 59 ℃, carries out condensation and gets B-grade condensation liquid, all sends B-grade condensation liquid back to rectifying tower 1 as second phegma then, and this B-grade condensation liquid locates to get into rectifying tower 1 80 ℃ of rectifying tower 1 rectifying section.
The comparative example 1
Adopt the flow process of Fig. 2.
Rectifying tower adopts packing tower, and theoretical plate number is 10.
From the spent acid of the washing procedure of nitrification, flow is 4100 kilograms/hour, and wherein the content of nitric acid is 20wt%, and vitriolic content is 8wt%.From the sour vapour of spent acid stripping process, flow is 7020 kilograms/hour, and wherein nitric acid content is 10～12wt%, and sulfuric acid content is 0.2wt%.
Above-mentioned spent acid and sour vapour are sent into rectifying tower 1, rectifying under 60kPa vacuum tightness, tower top temperature is 78 ℃; Column bottom temperature is 99 ℃; Reboiler at the bottom of the rectifying Tata exports the product after the concentrating of obtaining, and wherein nitric acid content is at 50wt%, and sulfuric acid content is at 10wt%; Send back to nitrification again, flow is 3500 kilograms/hour;
The gas phase of rectifying tower 1 cat head gets into first-stage condenser 2, under 74 ℃, carries out condensation and gets the one-level phlegma, and the one-level phlegma is effluxed processing as nitric acid preconcentration technique waste water, and flow is 7510 kilograms/hour, and wherein, the content of nitric acid is 2wt%;
The tail gas of first-stage condenser 2 gets into secondary condenser 3 again, under 60 ℃, carries out condensation, then B-grade condensation liquid is all sent back to the cat head of rectifying tower, as the phegma of rectifying tower 1.
Claims (9)
1. the nitric acid pre-concentration method of spent acid concentration technology during a DNT is produced; It comprises the steps: to make sour vapour from the spent acid of the washing procedure of nitrification and/or spent acid stripping process to get in the rectifying tower under the vacuum tightness of 60～64kPa, to carry out rectification under vacuum; Reboiler at the bottom of being arranged at said rectifying Tata vaporize concentrated after product, said concentrated after product is sent back to nitrification; The tower top temperature of said rectifying tower is 73～78 ℃, and column bottom temperature is 95～103 ℃;
Wherein, the gas phase that is arranged in the cat head of said rectifying tower gets into first-stage condenser and carries out condensation, the one-level phlegma, send said one-level phlegma the cat head of said rectifying tower back to, as first phegma of said rectifying tower, reflux ratio is 0.18～0.2; Remaining one-level phlegma is discharged as the waste water of nitric acid preconcentration technique;
The tail gas of said first-stage condenser gets into secondary condenser again; Carry out condensation and get B-grade condensation liquid; All send said B-grade condensation liquid back to said rectifying tower as second phegma, said B-grade condensation liquid locates to get into rectifying tower 80～82 ℃ of the rectifying section of said rectifying tower.
2. the method for claim 1 is characterized in that: the content of nitric acid is 18～20wt% in the spent acid of said washing procedure from nitrification, and vitriolic content is 5～8wt%.
3. the method for claim 1, it is characterized in that: the content of nitric acid is 10～12wt% in the sour vapour of said spent acid stripping process, vitriolic content is 0.2～0.5wt%.
4. the method for claim 1, it is characterized in that: nitric acid content is 45～50wt% in the said concentrated after product, sulfuric acid content is 5～10wt%.
5. like each described method in the claim 1～4, it is characterized in that: being condensate under 72～74 ℃ in the said first-stage condenser carried out.
6. like each described method in the claim 1～5, it is characterized in that: being condensate under 58～62 ℃ in the said secondary condenser carried out.
7. the method for claim 1, it is characterized in that: described rectifying tower is a packed tower.
8. method as claimed in claim 7 is characterized in that: the theoretical plate number of said packed tower is 8～12.
9. method as claimed in claim 8 is characterized in that: the theoretical plate number of said packed tower is 10.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN105329864A (en) * | 2015-12-01 | 2016-02-17 | 南京师范大学 | Resourceful treatment method of waste acid solution in nitrobenzene production process |
| CN113786639A (en) * | 2021-10-13 | 2021-12-14 | 中国天辰工程有限公司 | Quenching and dewatering process method for cyclohexanol dehydrogenation product |
| CN114715863A (en) * | 2022-05-06 | 2022-07-08 | 天津大学浙江绍兴研究院 | Process for recovering nitration waste acid of insoluble organic matters |
| CN115611746A (en) * | 2022-11-02 | 2023-01-17 | 天津大学浙江绍兴研究院 | Process and equipment for continuous nitration production of 3-methyl-2-nitrobenzoic acid |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113786639A (en) * | 2021-10-13 | 2021-12-14 | 中国天辰工程有限公司 | Quenching and dewatering process method for cyclohexanol dehydrogenation product |
| CN114715863A (en) * | 2022-05-06 | 2022-07-08 | 天津大学浙江绍兴研究院 | Process for recovering nitration waste acid of insoluble organic matters |
| CN115611746A (en) * | 2022-11-02 | 2023-01-17 | 天津大学浙江绍兴研究院 | Process and equipment for continuous nitration production of 3-methyl-2-nitrobenzoic acid |
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