Method for treating waste liquid generated in preparation of O-methylisourea bisulfate by urea method

Abstract

The invention discloses a waste liquid treatment method for preparing O-methylisourea hydrogen sulfate by a urea method, which aims at overcoming the defects of an organic acid-containing waste liquid treatment method which is high in organic matter content, low in moisture content, high in acid content, high in temperature and explosive, adopts a combined treatment method of alkali and a dispersing agent, and gasifies the dispersing agent through heat generated in a neutralization process; according to the present invention, the heat in the whole reaction process is removed so as to ensure the safety of the reaction process, and the presence of the dispersant reduces the viscosity of the system, simplifies the by-product preparation steps, improves the by-product quality, has advantages of high resource utilization rate, low equipment requirement, low waste liquid component requirement, and effective hazardous waste amount reduction; meanwhile, the dispersing agent can be repeatedly used, the treatment method is simple, the treatment time is short, the treatment efficiency is high, and the method has good environmental benefits and is suitable for large-scale popularization and application.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of chemical environmental protection technology, and particularly relates to a method for treating waste liquid in preparation of O-methyl isourea hydrogen sulfate by a urea method. BACKGROUND

[0002] O-methyl isourea hydrogen sulfate is a chemical used for synthesizing fluorouracil antitumor drugs, imidazole anthelmintics and new herbicides, etc. A large amount of waste liquid containing high-concentration sulfuric acid is generated in the preparation of O-methyl isourea hydrogen sulfate by a urea method. The organic matter content in the waste liquid is about 40%-60%, the water content is about 3%, and the sulfuric acid content is about 50%. The waste liquid also has problems of high viscosity, easy solidification at low temperature, etc.

[0003] Concentrated sulfuric acid itself has strong oxidizing property, and the organic components in the acid-containing waste liquid are relatively complex. Unsaturated hydrocarbons will polymerize in the system containing concentrated sulfuric acid, especially in a low-moisture system, the viscosity of the waste acid is increased.

[0004] At present, the treatment methods for the waste liquid containing organic matter and sulfuric acid mainly include physical methods and chemical methods.

[0005] 1) Physical method, mainly including adsorption method and extraction method: ① The adsorption method is to use resin or activated carbon or other substances to adsorb the organic matter in the acid-containing waste liquid, so as to obtain waste acid by-products with low organic matter content. This method is only suitable for dilute acid with low organic matter content, and has the problems of high treatment cost and large amount of hazardous waste.

[0006] 2) Chemical method, mainly including neutralization method: solid alkali or liquid alkali is directly added to the waste acid to adjust the acidity. For high-concentration organic waste acid, the reaction is not uniform in the operation process, and the recovered by-product salt needs subsequent treatment. For low-concentration organic waste acid, the scheme is relatively practical, but the process is complex, the energy consumption is high, and the resource consumption is large.

[0007] Therefore, it is urgent to develop a treatment method which is simple in steps and can realize the resource utilization, harmless treatment and reduction of the waste liquid containing organic matter and acid. SUMMARY

[0008] In view of the above-mentioned disadvantages of the prior art, the purpose of the present application is to provide a urea method for preparing O-methyl isourea hydrogen sulfate waste liquid treatment method, aiming at the deficiency of high organic matter, low moisture, high acid and high temperature explosion of acid-containing organic waste liquid treatment method, using the method of alkali and dispersant combined treatment, through the heat generated in the neutralization process to make the dispersant gasification, so as to remove the heat in the whole reaction process, ensure the safety of the reaction process, at the same time, the existence of dispersant makes the viscosity of the system reduce, simplifies the by-product preparation step and improves the by-product quality, high resource utilization rate, low equipment requirement, low waste liquid component requirement, has the advantages of effectively reducing the amount of hazardous waste; At the same time, the dispersant can be reused, the treatment method is simple, the treatment time is short, the treatment efficiency is high, has good environmental benefits, is suitable for large-scale popularization and application.

[0009] In order to achieve the above-mentioned purpose and other related purposes, the present application provides a urea method for preparing O-methyl isourea hydrogen sulfate waste liquid treatment method, which comprises the steps of adding dispersant and alkali under the condition that the temperature is not higher than the boiling point of the dispersant, adjusting the pH to less than 7, separating the by-product under the condition of cooling and / or heat preservation, and recovering the dispersant.

[0010] Further, after adding the dispersant and alkali, the pH is adjusted to 5.5-6.5.

[0011] Further, the cooling condition when adding the dispersant and alkali is below the boiling point of the dispersant.

[0012] Further, the dispersant is a polar solvent and its boiling point is not higher than the decomposition and explosion temperature of the waste liquid; preferably, the dispersant is methanol or ethanol.

[0013] Further, the mass of the dispersant added is more than 1.2 times the mass of the waste liquid.

[0014] Further, the alkali is a solid alkali or a gaseous alkali.

[0015] Further, the solid alkali is sodium hydroxide, magnesium oxide or calcium oxide; the gaseous alkali is ammonia.

[0016] Further, the feeding mode is slow feeding.

[0017] Further, the reaction temperature is the reflux temperature of the dispersant.

[0018] Further, the reflux reaction temperature needs a reflux condenser to remove heat and maintain the temperature.

[0019] Further, the by-product is alkali metal sulfate or ammonium sulfate; the method for separating the by-product includes filtration, suction filtration and / or centrifugation.

[0020] Further, the separation by-product process needs to use 0.2 times the mass of the dispersant of the waste liquid mass for elution.

[0021] Further, the method for recovering the dispersant is to first reduce pressure distillation and then rectification.

[0022] Further, the recovery rate of the by-product is ≥80%; and further, the recovery rate of the by-product is ≥90%.

[0023] Due to the above technology, the present application has the following advantages compared with the prior art:

[0024] 1) The waste liquid containing high-concentration sulfuric acid in the prior art contains a large amount of organic matter with unclear components in addition to a large amount of waste sulfuric acid, so there is a problem of high viscosity that cannot be treated and can only be incinerated as hazardous waste. If the high-concentration sulfuric acid contained in the waste liquid is forcibly utilized by adding alkali, the problem of large heat release of acid-base neutralization reaction and the temperature rise of the waste liquid will occur. If the water content in the waste liquid is low or there is no water, the high temperature will intensify the decomposition of the organic matter and the further heat release of the polymerization reaction of sulfuric acid and unsaturated hydrocarbons in the waste liquid, resulting in a local overheated reaction and safety risks. In addition, by-products of alkali metal sulfate or ammonium sulfate will be continuously precipitated during the introduction of alkali, and the by-product salt and the organic impurities will be wrapped in each other and not easy to separate. The present application uses a dispersant to dissolve the organic matter in the waste liquid in the dispersant, thereby reducing the viscosity of the waste liquid. At the same time, the by-product alkali metal sulfate or ammonium sulfate prepared during the introduction of alkali is also uniformly dispersed in the system. The heat generated by the reaction is removed through the boiling reflux process of the dispersant, effectively avoiding the problems of decomposition and explosion caused by the reaction being too intense at high temperature. Further, the low-boiling-point dispersant usually has low viscosity, and the mixing of the dispersant and the waste liquid reduces the viscosity of the waste liquid, making the solid-liquid separation process difficult and improving the efficiency.

[0025] 2) The present application significantly improves the quality of the by-product alkali metal sulfate or ammonium sulfate, has high resource utilization rate, low requirements for equipment and waste liquid components, easy reaction, simple treatment method, short time, high efficiency, and is suitable for large-scale popularization and application.

[0026] 3) The present application overcomes the problem that the waste liquid containing high-concentration sulfuric acid in the prior art cannot be treated and can only be treated as hazardous waste. By introducing a dispersant, the sulfuric acid in the acid-containing waste liquid is fully utilized, and the dispersant can be recovered by distillation and rectification and repeatedly used in the process, achieving a recovery rate of the dispersant ≥90% and significantly reducing the amount of hazardous waste. DETAILED DESCRIPTION

[0027] For better understanding of the present application, the following further describes the present application in conjunction with specific examples. These examples are used to illustrate the main reactions and basic features of the present application, and are not limited by the following examples. The implementation conditions used in the examples can be further adjusted according to specific requirements, and the implementation conditions not mentioned are usually the conditions in conventional experiments.

[0028] The present application is further described below in conjunction with examples through the description of the examples.

[0029] Example 1

[0030] 1) Pretreatment: After the reaction kettle is baked, nitrogen replacement is performed. A pneumatic pump is used to pump 267 kg of waste liquid of O-methyl isourea bisulfite prepared by urea method (the organic matter content of the waste liquid is about 51%, including O-methyl isourea bisulfite about 17%, urea condensate about 28%, urea about 6%, the sulfuric acid content is about 44%, and the moisture content is about 5%) into the reaction kettle. A pneumatic pump is used to pump 1.2 times the mass of the dispersant methanol into the waste liquid. During the process of pumping methanol, the temperature is always maintained below the boiling point temperature of methanol;

[0031] 2) Ammonia passage: the ammonia valve is opened. During the ammonia passage process, the temperature in the reaction kettle is maintained at 65°C, the methanol is in reflux state, and the pH in the kettle is 5.5 to 6.5 when the ammonia passage is stopped. After the ammonia passage is stopped, the kettle is placed for 10 minutes, and the pH in the kettle is re-measured to be 5.5 to 6.5.

[0032] 3) Ammonium sulfate separation: the reaction kettle is cooled to below the flash point temperature of 12.22°C. Ammonium sulfate salt is separated by centrifugation. 53.4 kg of methanol is used for washing twice. After centrifugation, the obtained salt is placed in a vacuum drying oven for drying. The temperature is set to 60°C, and the negative pressure is -0.95 MPa. After drying, 152.29 kg of ammonium sulfate meeting the national fertilizer grade standard type I is obtained, with a purity of 99.87%. The yield calculated based on the sulfuric acid content in the waste liquid is 96.12%.

[0033] 4) Recovery of dispersant: the combined methanol is transferred to a distillation kettle for vacuum desolventization. After desolventization, the bottom liquid is placed in a barrel as high-calorific-value organic matter for incineration. The fraction is transferred to a rectification tower for refining methanol. Finally, 362.2 kg of methanol is recovered, with a purity of 99.31% and a yield of 96.23%. The organic kettle residue is reduced by 113.06 kg, and the hazardous waste is reduced by 42.35%. The pH of the waste liquid is neutral.

[0034] Example 2

[0035] 1) Pretreatment: After the reaction kettle is baked, nitrogen replacement is performed. A pneumatic pump is used to pump 267 kg of waste liquid of O-methyl isourea bisulfite prepared by urea method (the organic matter content of the waste liquid is about 51%, including O-methyl isourea bisulfite about 17%, urea condensate about 28%, urea about 6%, the sulfuric acid content is about 44%, and the moisture content is about 5%) into the reaction kettle. A pneumatic pump is used to pump 1.2 times the mass of the dispersant methanol into the waste liquid. During the process of pumping methanol, the temperature is always maintained below the boiling point temperature of methanol;

[0036] 2) Ammonia passage: open the ammonia valve, maintain the temperature in the reactor at 65°C during the ammonia passage, the methanol is in reflux state, stop the ammonia passage when the pH in the reactor is 3-4. After stopping the ammonia passage, retest the pH in the reactor after standing for 10 min and maintaining the temperature at 3-4;

[0037] 3) Separation of ammonium sulfate: cool the reactor to below the flash point temperature of 12.22°C, centrifugally separate the ammonium sulfate salt, wash twice with 56 kg of methanol, and after centrifugation, the obtained salt is placed in a vacuum drying oven, the temperature is set to 60°C, and the negative pressure is -0.95 MPa, after drying, 140.21 kg of type I ammonium sulfate of national fertilizer standard is obtained, the purity is 99.12%, and the yield calculated based on the sulfuric acid content in the waste acid is 87.74%;

[0038] 4) Recovery of dispersant: transfer the dispersant methanol to the distillation kettle for vacuum desolventization, after desolventization, the bottom liquid is placed in a barrel for high-heat-value organic matter incineration, and the fraction is transferred to a rectification tower for refined methanol, finally, 379.88 kg of methanol is recovered, the purity is 98.92%, and the yield is 95.86%. The organic kettle residue is reduced by 104.1 kg, the hazardous waste is reduced by 37.18%, and the waste liquid is acidic.

[0039] Example 3

[0040] 1) Pretreatment: after oven-drying the reactor, nitrogen replacement is performed, 200 kg of waste acid (the composition is basically the same as above, and the sulfuric acid content is about 46%) is pumped into the reactor by using a pneumatic pump, and 240 kg of methanol is pumped in by using a pneumatic pump to ensure that the temperature is maintained below the boiling point of methanol during the methanol passage;

[0041] 2) Ammonia passage: open the ammonia valve, maintain the temperature in the reactor at 65°C during the ammonia passage, the methanol is in reflux state, stop the ammonia passage when the pH in the reactor is 5.5 to 6.5. After stopping the ammonia passage, retest the pH in the reactor after standing for 10 min and maintaining the temperature at 5.5 to 6.5;

[0042] 3) Separation of ammonium sulfate: do not change the temperature of the reactor, directly centrifugally separate the ammonium sulfate salt, wash twice with 40 kg of methanol, and after centrifugation, the obtained salt is placed in a vacuum drying oven, the temperature is set to 60°C, and the negative pressure is -0.95 MPa, after drying, 102.34 kg of type I ammonium sulfate of national fertilizer standard is obtained, the purity is 99.14%, and the yield calculated based on the sulfuric acid content in the waste acid is 81.88%;

[0043] 4) Recovery of dispersant: the dispersant methanol is transferred to the distillation kettle for vacuum desolventizing, and the bottom liquid after desolventizing is put into a barrel as high-heat-value organic matter for incineration. The distillate obtained by desolventizing is transferred to a rectification tower for refining methanol. Finally, 273.21 kg of methanol is recovered, with a purity of 97.47% and a yield of 95.11%. The organic acid-containing waste liquid is reduced by 75.98 kg, the hazardous waste is reduced by 37.99%, and the waste liquid pH is neutral.

[0044] Example 4

[0045] 1) Pretreatment: After the reaction kettle is baked, nitrogen replacement is performed. A pneumatic pump is used to pump 200 kg of waste acid (the composition of the waste liquid is basically the same as above, and the sulfuric acid content is about 43%) into the reaction kettle. A pneumatic pump is used to pump 240 kg of methanol, ensuring that the temperature is always maintained below the boiling point of methanol during the methanol process;

[0046] 2) Ammonia passage: open the ammonia valve, maintain the temperature in the reaction kettle at 65°C during the ammonia passage process, and the methanol is in reflux state. When the pH in the kettle is 5.5 to 6.5, stop passing ammonia. After stopping the ammonia passage, stand for 10 min and retest the pH in the kettle to be 5.5 to 6.5;

[0047] 3) Separation of ammonium sulfate: the reaction kettle is cooled to below the flash point temperature of 12.22°C, and ammonium sulfate salt is separated by centrifugation. 10 kg of methanol is used for washing twice. After centrifugation, the obtained salt is placed in a vacuum drying oven for drying. The temperature is set to 60°C, and the negative pressure is -0.95 MPa. After drying, 107.1 kg of national fertilizer grade standard type II ammonium sulfate is obtained, with a purity of 90.93%, and a yield of 84.07% calculated based on the sulfuric acid content in the waste acid;

[0048] 4) Recovery of dispersant: the dispersant methanol is transferred to the distillation kettle for vacuum desolventizing, and the bottom liquid after desolventizing is put into a barrel as high-heat-value organic matter for incineration. The distillate obtained by desolventizing is transferred to a rectification tower for refining methanol. Finally, 273.21 kg of methanol is recovered, with a purity of 97.47% and a yield of 95.11%. The organic acid-containing waste liquid is reduced by 75.98 kg, the hazardous waste is reduced by 37.99%, and the waste liquid pH is neutral.

[0049] Example 5

[0050] 1) Pretreatment: After the reaction kettle is baked, nitrogen replacement is performed. A pneumatic pump is used to pump 200 kg of waste acid (the composition of the waste liquid is basically the same as above, and the sulfuric acid content is about 43%) into the reaction kettle. A pneumatic pump is used to pump 240 kg of methanol, ensuring that the temperature is always maintained below the boiling point of methanol during the methanol process;

[0051] 2) Ammonia passage: open the ammonia valve, maintain the temperature in the reactor at 65°C during the ammonia passage process, stop the ammonia passage when the pH in the reactor is 5.5 to 6.5. After stopping the ammonia passage, retest the pH in the reactor after standing for 10 min and maintaining the temperature at 5.5 to 6.5;

[0052] 3) Separation of ammonium sulfate: cool the reactor to below the flash point temperature of 12.22°C, centrifugally separate the ammonium sulfate salt, wash twice with 40 kg of methanol, and after centrifugation, the obtained salt is placed in a vacuum drying oven for drying, the temperature is set to 60°C, and the negative pressure is -0.95 MPa. After drying, 107.12 kg of type II ammonium sulfate of the national fertilizer grade standard is obtained, with a purity of 91.13%, and the yield calculated based on the sulfuric acid content in the waste acid is 88.38%;

[0053] 4) Recovery of dispersant: transfer the dispersant methanol to the distillation kettle for vacuum desolventization, and after desolventization, the bottom liquid is placed in a barrel for incineration as high-calorie organic matter. The fraction obtained after desolventization is transferred to a rectification column for refining methanol. Finally, 211.79 kg of methanol is recovered, with a purity of 98.36% and a yield of 94.69%. The organic acid-containing waste liquid is reduced by 79.53 kg, and the hazardous waste is reduced by 39.76%, and the waste liquid pH is neutral.

[0054] Example 6

[0055] 1) Pretreatment: after oven-drying the reactor, nitrogen replacement is performed, 200 kg of waste acid (the composition is basically the same as above, and the sulfuric acid content is about 44%) is pumped into the reactor using a pneumatic pump, and 260 kg of methanol is pumped in through a pneumatic pump to ensure that the temperature during methanol passage is always maintained below the boiling point temperature of methanol;

[0056] 2) Ammonia passage: open the ammonia valve, maintain the temperature in the reactor at 65°C during the ammonia passage process, stop the ammonia passage when the pH in the reactor is 5.5 to 6.5. After stopping the ammonia passage, retest the pH in the reactor after standing for 10 min and maintaining the temperature at 5.5 to 6.5;

[0057] 3) Separation of ammonium sulfate: cool the reactor to below the flash point temperature of 12.22°C, centrifugally separate the ammonium sulfate salt, wash twice with 40 kg of methanol, and after centrifugation, the obtained salt is placed in a vacuum drying oven for drying, the temperature is set to 60°C, and the negative pressure is -0.95 MPa. After drying, 107.12 kg of type II ammonium sulfate of the national fertilizer grade standard is obtained, with a purity of 91.13%, and the yield calculated based on the sulfuric acid content in the waste acid is 88.38%;

[0058] 4) Recovery of dispersant: the dispersant methanol is transferred to the distillation kettle for desolventization under reduced pressure, and the bottom liquid after desolventization is placed in a barrel as high-heat-value organic matter for incineration. The distillate obtained by desolventization is transferred to a rectification tower for refined methanol. Finally, 287.63 kg of methanol is recovered, with a purity of 99.42% and a yield of 95.32%. The organic acid-containing waste liquid is reduced by 84.94 kg, the hazardous waste is reduced by 42.47%, and the waste liquid pH is neutral.

[0059] Example 7

[0060] 1) Pretreatment: After the reaction kettle is baked, nitrogen replacement is performed. A pneumatic pump is used to pump 200 kg of waste liquid (the composition of the waste liquid is basically the same as above, and the sulfuric acid content is about 44%) into the reaction kettle. A pneumatic pump is used to pump 240 kg of ethanol, and the ethanol flow is controlled to ensure that the temperature during the ethanol passing process is always maintained below 78°C.

[0061] 2) Ammonia passing: open the ammonia valve, and maintain the temperature in the reaction kettle at 78°C during the ammonia passing process. The ethanol is in a reflux state, and the pH in the kettle is 5.5 to 6.5 when the ammonia passing is stopped. After stopping the ammonia passing, the kettle is placed for 10 minutes, and the pH in the kettle is re-measured to be 5.5 to 6.5.

[0062] 3) Separation of ammonium sulfate: the reaction kettle is cooled to below the flash point temperature of 12.78°C, and ammonium sulfate salt is separated by centrifugation. 40 kg of ethanol is used for washing twice. After centrifugation, the obtained salt is placed in a vacuum drying oven for drying. The temperature is set to 60°C, and the negative pressure is -0.95 MPa. After drying, 113.61 kg of national fertilizer grade standard type I ammonium sulfate is obtained, with a purity of 99.25% and a yield of 95.13% calculated based on the sulfuric acid content in the waste acid.

[0063] 4) Recovery of dispersant: the dispersant ethanol is transferred to the distillation kettle for desolventization under reduced pressure. The bottom liquid after desolventization is placed in a barrel as high-heat-value organic matter for incineration. The distillate is transferred to a rectification tower for refined ethanol. Finally, 279.22 kg of ethanol is recovered, with a purity of 93.77% and a yield of 93.51%. The organic acid-containing waste liquid is reduced by 84.35 kg, the hazardous waste is reduced by 42.13%, and the waste liquid pH is neutral.

[0064] Example 8

[0065] 1) Pretreatment: After the reaction kettle is baked, nitrogen replacement is performed. A pneumatic pump is used to pump 200 kg of waste acid (the composition of the waste liquid is basically the same as above, and the sulfuric acid content is about 45%) into the reaction kettle. A pneumatic pump is used to pump 240 kg of methanol, and the temperature during the methanol passing process is always maintained below the boiling point temperature of methanol.

[0066] 2) Adding base: open the base valve, add solid sodium hydroxide to the waste liquid, maintain the temperature in the reaction kettle at 65°C during the addition of base, the methanol is in reflux state, stop adding solid sodium hydroxide when the pH in the kettle is 5.5 to 6.5. After stopping the addition, retest the pH in the kettle after standing for 10 min and maintaining the temperature at 5.5 to 6.5;

[0067] 3) Separation of sodium sulfate: cool the reaction kettle to below the flash point temperature of 12.22°C, centrifugally separate the sodium sulfate salt, wash twice with 40 kg of methanol, after centrifugation, the obtained salt is placed in a vacuum drying oven, the temperature is set to 60°C, the negative pressure is -0.95 MPa, after drying, 112.56 kg of national standard type I sodium sulfate is obtained, the purity is 98.15%, the yield is 84.72% calculated on the basis of the sulfuric acid content in the waste acid;

[0068] 4) Recovery of dispersant: transfer the dispersant methanol to the distillation kettle for vacuum desolventization, after desolventization, the bottom liquid is placed in a barrel for high-heat-value organic matter incineration, the fraction obtained after desolventization is transferred to a rectification column for refined methanol, finally 264.40 kg of methanol is recovered, the purity is 97.54%, the yield is 92.11%. The organic acid-containing waste liquid is reduced by 44.62 kg, the hazardous waste is reduced by 22.31%, and the waste liquid pH is neutral.

[0069] Example 9

[0070] 1) Pretreatment: after drying the reaction kettle, replace it with nitrogen, use a pneumatic pump to pump 200 kg of waste acid (the composition of the waste liquid is basically the same as above, the sulfuric acid content is about 43%) into the reaction kettle, and use a pneumatic pump to pump 240 kg of methanol to ensure that the temperature is always maintained below the boiling point of methanol during the methanol process;

[0071] 2) Adding base: open the base valve, add solid magnesium oxide to the waste liquid, maintain the temperature in the reaction kettle at 65°C during the addition of base, the methanol is in reflux state, stop adding solid magnesium oxide when the pH in the kettle is 5.5 to 6.5. After stopping the addition, retest the pH in the kettle after standing for 10 min and maintaining the temperature at 5.5 to 6.5;

[0072] 3) Separation of magnesium sulfate: cool the reaction kettle to below the flash point temperature of 12.22°C, centrifugally separate the magnesium sulfate salt, wash twice with 40 kg of methanol, after centrifugation, the obtained salt is placed in a vacuum drying oven, the temperature is set to 60°C, the negative pressure is -0.95 MPa, after drying, 87.10 kg of national standard type II magnesium sulfate is obtained, the yield is 80.92% calculated on the basis of the sulfuric acid content in the waste acid;

[0073] 4) Recovery of dispersant: the dispersant methanol is transferred to the distillation kettle for vacuum desolventizing, and the bottom liquid after desolventizing is put into a barrel as high-heat-value organic matter for incineration. The distillate obtained by desolventizing is transferred to a rectifying column for refining methanol. Finally, 261.3 kg of methanol is recovered, with a purity of 98.33% and a yield of 91.76%. The organic acid-containing waste liquid is reduced by 78.13 kg, the hazardous waste is reduced by 39.07%, and the waste liquid pH is neutral.

[0074] Example 10

[0075] 1) Pretreatment: After the reaction kettle is baked, nitrogen replacement is performed. A gas pump is used to pump 200 kg of waste liquid of O-methyl isourea bisulfite prepared by urea method (the composition of the waste liquid is basically the same as above, and the sulfuric acid content is about 45%) into the reaction kettle. A gas pump is used to pump 240 kg of dispersant dichloroethane with a mass of 1.2 times that of the waste liquid. During the process of introducing dichloroethane, the temperature is always maintained below the boiling point temperature of dichloroethane;

[0076] 2) Ammonia introduction: open the ammonia valve, and maintain the temperature in the reaction kettle at 83°C during the ammonia introduction process. The dichloroethane is in a reflux state, and the pH in the kettle is 5.5 to 6.5 when the ammonia introduction is stopped. After stopping the ammonia introduction, the kettle is placed for 10 minutes, and the pH is re-measured to be 5.5 to 6.5;

[0077] 3) Ammonium sulfate separation: the reaction kettle is cooled to below the flash point temperature of 12.22°C, and ammonium sulfate salt is separated by centrifugation. 40 kg of dichloroethane is used for washing twice. After centrifugation, the obtained salt is placed in a vacuum drying oven for drying. The temperature is set to 60°C, and the negative pressure is -0.95 MPa. After drying, 119.22 kg of ammonium sulfate meeting the national fertilizer grade standard type II is obtained, with a purity of 91.15% and a yield of 89.64% calculated based on the sulfuric acid content in the waste acid;

[0078] 4) Recovery of dispersant: the dispersant methanol is transferred to the distillation kettle for vacuum desolventizing, and the bottom liquid after desolventizing is put into a barrel as high-heat-value organic matter for incineration. The distillate obtained by desolventizing is transferred to a rectifying column for refining methanol. Finally, 261.3 kg of methanol is recovered, with a purity of 98.33% and a yield of 91.76%. The organic acid-containing waste liquid is reduced by 78.13 kg, the hazardous waste is reduced by 39.07%, and the waste liquid pH is neutral.

[0079] Example 11

[0080] 1) Pretreatment: After the reaction kettle is baked, nitrogen replacement is performed. A gas pump is used to pump 200 kg of waste acid (the composition of the waste liquid is basically the same as above, and the sulfuric acid content is about 42%) into the reaction kettle. A gas pump is used to pump 240 kg of methanol, ensuring that the temperature is always maintained below the boiling point temperature of methanol during the methanol introduction process;

[0081] 2) Add base: open the base valve, add 30% liquid sodium hydroxide to the waste liquid, maintain the temperature in the reactor at 65°C during the addition of base, the methanol is in reflux state, stop adding 30% liquid sodium hydroxide when the pH in the reactor is 5.5 to 6.5. After stopping the addition, retest the pH in the reactor after standing for 10 min, which is 5.5 to 6.5;

[0082] 3) Separate sodium sulfate: cool the reactor to below the flash point temperature of 12.22°C, centrifuge the sodium sulfate salt, wash twice with 40 kg of methanol, and after centrifugation, obtain sodium sulfate, put it into a vacuum drying oven, set the temperature to 60°C, and the negative pressure to -0.95 MPa, after drying, obtain 42.17 kg of national standard type I sodium sulfate with a purity of 98.11%, and the yield is 34.03% based on the sulfuric acid content in the waste acid;

[0083] 4) Recover the dispersant: transfer the dispersant methanol to the distillation kettle for vacuum desolventization, after desolventization, the bottom liquid is placed in a barrel for high-heat-value organic matter incineration, the distillate obtained by desolventization is transferred to a rectification tower for refined methanol, finally recover 256.33 kg of methanol with a purity of 95.47%, and the yield is 87.40%. Due to the introduction of a large amount of water, the organic acid-containing waste liquid does not show a decrease, the organic waste liquid increases by 230.33 kg, the hazardous waste increases by 115.16%, and the waste liquid PH shows neutral.

[0084] The above examples are only preferred technical solutions of the present application, and should not be regarded as limiting the present application, the protection scope of the present application should be the technical solutions recited in the claims, including the equivalent replacement solutions of the technical features recited in the claims, i.e. within this range, the equivalent replacement improvement is also within the protection scope of the present application.

Claims

1. A method for treating waste liquor from the urea process for the production of O-methylisourea hydrogen sulfate, characterized in that, The step of adding dispersant and alkali under the condition that the temperature is not higher than the boiling point of the dispersant, adjusting the pH to less than 7, separating by-products under the condition of cooling and / or holding, and recovering the dispersant.

2. The waste liquid treatment method according to claim 1, wherein The cooling condition when adding the dispersant and alkali is below the boiling point of the dispersant.

3. The waste liquid treatment method according to claim 1, wherein The dispersant is a polar solvent and its boiling point is not higher than the decomposition and explosion temperature of the waste liquid; preferably, the dispersant is methanol or ethanol; preferably, the amount of the dispersant is 1.1-1.3 times of the waste liquid; more preferably, the amount of the dispersant is 1.2 times of the waste liquid.

4. The waste liquid treatment method according to claim 1, wherein The alkali is a solid alkali or a gaseous alkali.

5. The waste liquid treatment method according to claim 4, wherein The solid alkali is sodium hydroxide, magnesium oxide or calcium oxide; the gaseous alkali is ammonia; preferably, the alkali is ammonia.

6. The waste liquid treatment method according to claim 1, wherein The holding temperature after adjusting the pH is the reflux temperature of the dispersant.

7. The waste liquid treatment method according to claim 1, wherein The by-products are alkali metal sulfate or ammonium sulfate; the method of separating the by-products includes filtration, suction filtration and / or centrifugation.

8. The waste liquid treatment method according to claim 1, wherein The method of recovering the dispersant is first vacuum distillation and then rectification.

9. The waste liquid treatment method according to claim 1, wherein The recovery rate of the by-products is ≥80%; preferably, the recovery rate of the by-products is ≥90%.

10. The waste liquid treatment method according to claim 1, wherein The pH is adjusted to 5.5-6.5 after adding the dispersant and alkali.