A method for recovering process water from glyphosate acid mother liquor

Abstract

The application provides a method for recovering process water from glyphosate acid mother liquor, wherein the glyphosate acid mother liquor is added with sodium carbonate, stirred, circulated, and pH value is adjusted to obtain pretreated mother liquor; the pretreated mother liquor is degassed, and the removed carbon dioxide and low-boiling organic substances are absorbed by using liquid alkali or solid alkali; a deodorizing agent is added into the absorption liquid to remove odor to obtain a mixed liquid containing sodium carbonate hydrate and sodium bicarbonate hydrate microcrystals; the acid mother liquor is pretreated by using sodium carbonate, and evaporation condensate water is separated and recovered from the pretreatment; and triethylamine hydrochloride is recovered. The evaporation condensate water recovered from the glyphosate mother liquor has low organic nitrogen content, no odor, and quality indexes meeting process requirements, and can be directly reused or used as supplementary water after being further purified by a membrane for processes such as chloromethane recovery, hydrochloric acid recovery and material washing in glyphosate production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of glyphosate production by glycine method, and particularly relates to a method for recovering process water from glyphosate acid mother liquor. BACKGROUND

[0002] Glyphosate is a highly efficient, low-toxic, broad-spectrum, non-selective herbicide with excellent biological characteristics. There are two routes for the mainstream production process of glyphosate at present: glycine method and IDA method. The mainstream process for producing glyphosate in China is glycine method. In 2022, the national glyphosate production capacity was 500,000 tons, and the glycine method accounted for about 70% of the national glyphosate production capacity.

[0003] The glyphosate synthesis process by glycine method is simple and the product quality is high, but there are problems of large mother liquor yield, high salt content, and large wastewater quantity. The existing mother liquor treatment process is that the acid mother liquor is first neutralized by liquid alkali to recover triethylamine, and then the alkali mother liquor is subjected to catalytic oxidation, evaporation and concentration, by-product phosphate and sodium chloride, and evaporation condensate water cannot be recycled and utilized due to high organic nitrogen, and it is also difficult to be subjected to biochemical treatment. Therefore, it is an urgent practical problem to improve the water quality of evaporation condensate water and realize batch recycling to achieve emission reduction. There are also some other methods, such as patent CN100551927C glyphosate mother liquor recycling method and patent CN201810961051 glyphosate by-product ammonia water and alkali comprehensive utilization method, which propose to use ammonium bicarbonate or sodium bicarbonate to treat glyphosate mother liquor, which can reduce the amount of wastewater generated, but the problem of high organic nitrogen in the mother liquor evaporation condensate water cannot be recycled is still not solved. SUMMARY

[0004] In view of the problems existing in the prior art, the application provides a method for recovering process water from glyphosate acid mother liquor. The glyphosate acid mother liquor can be treated by the process method to recover relatively clean evaporation condensate liquid, the pH value is neutral, and in particular, the organic nitrogen content is low and there is no irritating odor, which solves the problems of large evaporation condensate water odor and unrecyclability of glyphosate mother liquor in the traditional process, and recycling in the glyphosate production process can be realized, thereby significantly reducing the wastewater discharge quantity of glyphosate mother liquor treatment.

[0005] The technical scheme adopted by the application is as follows:

[0006] A method for recovering process water from glyphosate acid mother liquor, comprising the following steps:

[0007] Step 1. Pretreatment of acid mother liquor:

[0008] 1.1 Add glyphosate acid mother liquor and sodium carbonate into a reactor, stir, circulate, and adjust the pH value to obtain a pretreated mother liquor;

[0009] 1.2 degassing the pretreated mother liquor to remove carbon dioxide and low boiling organic compounds, and using liquid or solid base to absorb the removed carbon dioxide and low boiling organic compounds to obtain an absorption liquid;

[0010] 1.3 adding a deodorant to the absorption liquid of 1.2 to eliminate the irritating odor of the absorption liquid, concentrating and crystallizing to obtain a mixed liquid containing sodium carbonate hydrate and sodium bicarbonate hydrate microcrystals;

[0011] 1.4 recycling the mixed liquid of 1.3 to 1.1;

[0012] Step 2. Separation and recovery of evaporation condensate water and triethylamine hydrochloride from pretreatment:

[0013] 2.1 transferring the pretreated mother liquor after removal of carbon dioxide into an evaporator for evaporation and concentration to separate evaporation condensate water, triethylamine hydrochloride and concentrated liquid;

[0014] 2.2 collecting the evaporation condensate water and recycling it to the glyphosate production process;

[0015] 2.3 selling or recycling triethylamine hydrochloride with liquid base to recover triethylamine;

[0016] 2.4 neutralizing the concentrated liquid with liquid base to convert residual triethylamine salt in the concentrated liquid into triethylamine, separating and recovering triethylamine, and recycling the remaining phosphorus-rich base mother liquor to further recover phosphorus resources by wet oxidation to recover phosphate or incineration to produce pyrophosphate;

[0017] Step 3: Recycling evaporation condensate water to the glyphosate production process:

[0018] 3.1 recycling evaporation condensate water to the hydrochloric acid recovery process, replacing part or all of the soft water with evaporation condensate water to absorb hydrogen chloride gas, and the byproduct hydrochloric acid can be used in the glyphosate acidolysis process;

[0019] 3.2 recycling evaporation condensate water to the chloromethane recovery process, replacing part or all of the soft water in the water washing tower with evaporation condensate water to wash organic components in the chloromethane tail gas, mainly methanol and methylal, and the water washing liquid is recycled to recover organic components;

[0020] 3.3 recycling evaporation condensate water to replace part or all of the soft water in the glyphosate washing process, and the washing water is recycled again in the crystallization liquid.

[0021] Preferably, in step 1.1, the mass ratio of glyphosate acid mother liquor to sodium carbonate is 100:(1-10), and the preferred mass ratio is 100:(3-8).

[0022] Preferably, in step 1.1, the pH value of the acid mother liquor is adjusted to 2-5 using sodium carbonate, and the preferred pH value is 3.0-4.0.

[0023] Preferably, in step 1.2, the degassing temperature of the pretreated mother liquor is 25-75°C, and the degassing pressure is -100 kPa-0 kPa. Further preferably, in step 1.2, the degassing temperature of the pretreated mother liquor is 35-65°C, and the degassing pressure is -90 kPa-50 kPa.

[0024] Preferably, in step 1.2, the absorption of carbon dioxide with liquid alkali is regenerated into sodium carbonate, and the concentration of the liquid alkali is 5%-50%. Preferably, the concentration of the liquid alkali is 35%-45%.

[0025] Further preferably, the concentration of the liquid alkali is 35%-45%.

[0026] Preferably, in step 1.3, the deodorizing agent is hydrogen peroxide or solid sodium peroxide, and 30% hydrogen peroxide is used for purification and deodorization, and the mass ratio of the glyphosate acid mother liquor to the deodorizing agent is 1:(100-500).

[0027] Preferably, in step 1.3, the deodorizing temperature is 50-110°C.

[0028] Further preferably, the deodorizing temperature is 60-90°C.

[0029] Preferably, in step 2.1, the evaporation ratio of the pretreated mother liquor is 10%-60%.

[0030] Further preferably, the evaporation ratio of the pretreated mother liquor is 30%-50%.

[0031] In step 2.1, the evaporation temperature of the pretreated mother liquor is 60-120°C, preferably 100-110°C, or under the condition of negative pressure 0.08-0.1 Mpa, the evaporation temperature is 60-70°C.

[0032] Preferably, in step 2.3, triethylamine hydrochloride is neutralized with liquid alkali to recover triethylamine, and the pH value of the neutralization is 8-12.

[0033] Preferably, in step 3.1, the evaporation condensate water is used in the hydrochloric acid recovery process, and the mass ratio of the evaporation condensate water to hydrogen chloride is (1-5):1.

[0034] Further preferably, the mass ratio of the evaporation condensate water to hydrogen chloride is (2-2.5):1.

[0035] Preferably, in step 3.2, the evaporation condensate water is used in the chloromethane recovery process, and the COD value of the water washing water is controlled to be 50000-200000 ppm.

[0036] Further preferably, the COD value of the water washing water is controlled to be 100000-150000 ppm.

[0037] Preferably, in step 3.3, the evaporated condensate water is used in the glyphosate process, and the mass ratio of the evaporated condensate water to glyphosate is (0.4-1.5):1.

[0038] Further preferably, the mass ratio of the evaporated condensate water to glyphosate is (0.6-1):1.

[0039] Compared with the prior art, the following beneficial effects are achieved:

[0040] 1. Sodium carbonate is used to replace liquid alkali, so that the water generated when the pH value of the mother liquor is adjusted is reduced, and carbon dioxide and low-boiling organic substances are removed through degassing.

[0041] 2. The carbon dioxide and low-boiling organic substances generated in the degassing process are recycled and regenerated through deodorization and liquid alkali absorption. The selected deodorizing agent is a green and clean oxidizing agent. Carbon dioxide can be recycled and regenerated into sodium carbonate through liquid alkali, and no waste gas pollution is generated.

[0042] 3. The pre-treatment mother liquor is concentrated through evaporation, and the evaporated condensate water can be directly reused. The remaining concentrated mother liquor is only 30%-40% of the original mother liquor, which can greatly reduce the treatment amount of the alkali mother liquor, reduce the post-treatment pressure, and reduce the environmental protection risk.

[0043] 4. The evaporated condensate water recovered from the glyphosate mother liquor has low organic nitrogen content and no odor, and the quality indicators meet the process requirements, so that the evaporated condensate water can be directly reused or used as make-up water after further purification by a membrane for the processes of chloromethane recovery, hydrochloric acid recovery, and material washing in the glyphosate production.

[0044] 5. The process can also recover triethylamine hydrochloride, which can be refined and sold or recover triethylamine. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 The process flowchart of the present application. DETAILED DESCRIPTION

[0046] In order to better understand the present application, the content of the present application will be further illustrated below in combination with examples and drawings. However, in order for those skilled in the art to fully understand the technical solutions and beneficial effects of the present application, the present application will be further described in combination with specific examples. The examples are only simple examples of the present application, and do not represent or limit the protection scope of the present application. The protection scope of the present application is subject to the claims.

[0047] The glyphosate acid mother liquor described in the examples and comparative examples is obtained by adjusting the pH value of the synthesis liquid to 0.3-1.5 after hydrolysis and acid hydrolysis in the process of synthesizing glyphosate by the glycine method, and then fully crystallizing and separating the glyphosate wet powder and the glyphosate acid mother liquor.

[0048] The main components of the glyphosate acid mother liquor are triethylamine hydrochloride 27%, glyphosate 5%, glyphosate 1.5%, phosphorous acid 1.8%, hydrochloric acid 1.4%, glyphosate derivative 0.9%, glycine 0.5%, and the rest is unknown.

[0049] Example 1

[0050] A process for treating a glyphosate mother liquor, comprising the following steps:

[0051] The glyphosate acid mother liquor 1000g was put into a 2000ml flask, 55g of sodium carbonate was added, the pH value was adjusted to 4.0, the temperature was controlled at 50℃, and the reaction was stirred for 20min. The removed gas was absorbed by liquid alkali, the mother liquor lost 25.5g, 2g of 30% hydrogen peroxide was added to the absorption liquid, the temperature was controlled at 90℃, and the stirring was performed for 20min. The recovered sodium carbonate solid was 29g, and the filtrate was used for triethylamine recovery.

[0052] The pre-treated mother liquor was concentrated by evaporation, the evaporation was performed at a negative pressure of-0.09Mpa, the evaporation condensate water was collected, when the weight of the evaporation condensate water reached 450g, the evaporation was stopped, and the temperature was lowered for crystallization. The water quality of the evaporation condensate was detected, the pH value was 7.5, the organic nitrogen was 12ppm, and the total phosphorus was 0.1ppm. The evaporation condensate was collected for later use.

[0053] After the concentrated mother liquor was crystallized, 275g of triethylamine hydrochloride was filtered out and collected for later use. The acid concentrated mother liquor was 304.5g, the pH value was adjusted to 9.5 by using 40% liquid alkali, triethylamine was recovered by standing, 240.5g of 40% liquid alkali was consumed, and the alkali mother liquor was 526.5g, which was collected for later use.

[0054] Example 2

[0055] A process for treating a glyphosate mother liquor, comprising the following steps:

[0056] The glyphosate acid mother liquor 1000g was put into a 2000ml three-necked flask, 40g of sodium carbonate was added, the pH value was adjusted to 2.5, the temperature was controlled at 50℃, and the stirring was performed for 20min to remove the gas. The mother liquor lost 18.6g, 100g of 45% liquid alkali was used to absorb the tail gas, 2g of 30% hydrogen peroxide was added to the absorption liquid, the temperature was controlled at 90℃, and the stirring was performed for 20min. The purified organic matter was crystallized by lowering the temperature, filtered, and 18g of sodium carbonate solid was recovered. The filtrate was used for triethylamine recovery.

[0057] The pre-treated mother liquor was concentrated by evaporation, the evaporation was performed at a pressure of-0.09Mpa, the evaporation condensate water was collected, when the weight of the evaporation condensate water reached 450g, the evaporation was stopped, and the temperature was lowered for crystallization. The water quality of the evaporation condensate was detected, the pH value was 5.5, the organic nitrogen was 22ppm, and the total phosphorus was 1.1ppm. The evaporation condensate was collected for later use.

[0058] After the crystallization of the concentrated mother liquor, triethylamine hydrochloride 275 g is filtered out and collected for later use. The acidic concentrated mother liquor 306.9 g is neutralized by using 40% liquid alkali to adjust the pH value to 9.5. The consumption of 40% liquid alkali is 245 g. The triethylamine is recovered by standing. The alkali mother liquor 534 g is collected for later use.

[0059] Example 3

[0060] A process method for treating glyphosate mother liquor, comprising the following steps:

[0061] Glyphosate acid mother liquor 1000 g is put into a 2000 ml three-necked flask. Sodium carbonate 48 g is added to adjust the pH value to 3.0. The temperature is controlled at 50 ℃ to stir for 20 min to remove gas. The weight of the mother liquor is reduced by 22.5 g. 110 g of 40% liquid alkali is used to absorb the tail gas. 2 g of 30% hydrogen peroxide is added to the absorption liquid. The temperature is controlled at 90 ℃ to stir for 20 min to purify the organic matter. The temperature is lowered to crystallize and filter. Sodium carbonate solid 26 g is recovered. The filtrate is used for triethylamine recovery.

[0062] The pre-treatment mother liquor is evaporated and concentrated. The evaporation is controlled at a pressure of -0.09 Mpa. The evaporation condensate water is collected. When the weight of the condensate water reaches 450 g, the evaporation is stopped. The temperature is lowered to crystallize. The water quality of the evaporation condensate is detected. The pH value is 6.5. The organic nitrogen is 19 ppm. The total phosphorus is 1.0 ppm. The evaporation condensate is collected for later use.

[0063] After the crystallization of the concentrated mother liquor, triethylamine hydrochloride 277 g is filtered out and collected for later use. The acidic concentrated mother liquor 298.5 g is neutralized by using 40% liquid alkali to adjust the pH value to 9.5. The consumption of 40% liquid alkali is 242 g. The alkali mother liquor 528.5 g is collected for later use.

[0064] Example 4

[0065] A process method for treating glyphosate mother liquor, comprising the following steps:

[0066] Glyphosate acid mother liquor 1000 g is put into a 2000 ml three-necked flask. Sodium carbonate 48 g is added to adjust the pH value to 3.0. The temperature is controlled at 50 ℃ to stir for 20 min to remove gas. The weight of the mother liquor is reduced by 22.5 g. 110 g of 40% liquid alkali is used to absorb the tail gas. 2 g of 30% hydrogen peroxide is added to the absorption liquid. The temperature is controlled at 90 ℃ to stir for 20 min to purify the organic matter. The temperature is lowered to crystallize and filter. Sodium carbonate solid 26 g is recovered. The filtrate is used for triethylamine recovery.

[0067] The pre-treatment mother liquor is evaporated and concentrated. The evaporation is controlled at a pressure of -0.09 Mpa. The evaporation condensate water is collected. When the weight of the condensate water reaches 450 g, the evaporation is stopped. The temperature is lowered to crystallize. The water quality of the evaporation condensate is detected. The pH value is 6.5. The organic nitrogen is 19 ppm. The total phosphorus is 1.0 ppm. The evaporation condensate is collected for later use.

[0068] After the crystallization of the concentrated mother liquor, triethylamine hydrochloride 273.5 g was filtered out and collected for use, and the acidic concentrated mother liquor 304 g was neutralized by using 40% liquid alkali to adjust the pH value to 9.5. The consumption of 40% liquid alkali was 240.5 g, and the alkali mother liquor 521.2 g was collected for use.

[0069] Example 5

[0070] A process method for treating glyphosate mother liquor, comprising the following steps:

[0071] Glyphosate acid mother liquor 1000 g was put into a 2000 ml three-necked flask, sodium carbonate 55 g was added, the pH value was adjusted to 4.0, and the temperature was controlled at 50°C for stirring for 20 min to remove gas. The weight of the mother liquor was reduced by 25.5 g, 110 g of 40% liquid alkali was used to absorb the tail gas, 2 g of 30% hydrogen peroxide was added to the absorption liquid, the temperature was controlled at 90°C for stirring for 20 min, the organic matter was purified, and the sodium carbonate solid 29 was recovered. The filtrate was used for triethylamine recovery.

[0072] The pre-treatment mother liquor was evaporated and concentrated, the evaporation was controlled at a pressure of -0.09 Mpa, the evaporation condensate water was collected, and when the weight of the condensate water reached 350 g, the evaporation was stopped, and the temperature was lowered for crystallization. The water quality of the evaporation condensate was detected, the pH value was 6.9, the organic nitrogen was 6 ppm, and the total phosphorus was 0.1 ppm. The evaporation condensate was collected for use.

[0073] After the crystallization of the concentrated mother liquor, triethylamine hydrochloride 205.5 g was filtered out and collected for use, and the acidic concentrated mother liquor 474 g was neutralized by using 40% liquid alkali to adjust the pH value to 9.5. The consumption of 40% liquid alkali was 293.8 g, and the alkali mother liquor 700.8 g was collected for use.

[0074] Example 6

[0075] A process method for treating glyphosate mother liquor, comprising the following steps:

[0076] Glyphosate acid mother liquor 1000 g was put into a 2000 ml three-necked flask, sodium carbonate 55 g was added, the pH value was adjusted to 4.0, and the temperature was controlled at 50°C for stirring for 20 min to remove gas. The weight of the mother liquor was reduced by 25.5 g, 110 g of 40% liquid alkali was used to absorb the tail gas, 2 g of 30% hydrogen peroxide was added to the absorption liquid, the temperature was controlled at 90°C for stirring for 20 min, the organic matter was purified, and the sodium carbonate solid 29 was recovered. The filtrate was used for triethylamine recovery.

[0077] The pre-treatment mother liquor was evaporated and concentrated, the evaporation was controlled at a pressure of -0.09 Mpa, the evaporation condensate water was collected, and when the weight of the condensate water reached 500 g, the evaporation was stopped, and the temperature was lowered for crystallization. The water quality of the evaporation condensate was detected, the pH value was 7.9, the organic nitrogen was 20 ppm, and the total phosphorus was 0.2 ppm. The evaporation condensate was collected for use.

[0078] After the crystallization of the concentrated mother liquor, triethylamine hydrochloride 317.5 g was filtered out and collected for use, and the acidic concentrated mother liquor 212 g was neutralized with 40% liquid alkali to adjust the pH value to 9.5, 40% liquid alkali was consumed 221 g, and the alkali mother liquor 432.3 g was collected for use.

[0079] Example 7

[0080] Glyphosate acid mother liquor 10 kg was put into a 20 L reaction kettle, sodium carbonate was added to adjust the pH value to 4.0, and 552 g of sodium carbonate was consumed. The temperature was controlled at 50°C, and the gas was removed by stirring for 40 min. The weight of the mother liquor was reduced by 255 g. 1100 g of 40% liquid alkali was used to absorb the tail gas. 20 g of 30% hydrogen peroxide was added to the absorption liquid. The temperature was controlled at 90°C, and the organic matter was purified by stirring for 30 min. The temperature was lowered to crystallize and filter. The sodium carbonate solid 293 was recovered, and the filtrate was used for triethylamine recovery.

[0081] The pre-treatment mother liquor was evaporated and concentrated. The evaporation was controlled at a pressure of -0.09 Mpa. The evaporation condensate water was collected. When the weight of the condensate water reached 4500 g, the evaporation was stopped, and the temperature was lowered to crystallize. The water quality of the evaporation condensate was detected. The pH value was 7.3, the organic nitrogen was 11 ppm, and the total phosphorus was 0.1 ppm. The evaporation condensate was collected for use.

[0082] After the crystallization of the concentrated mother liquor, triethylamine hydrochloride 2760 g was filtered out and collected for use, and the acidic concentrated mother liquor 3035 g was neutralized with 40% liquid alkali to adjust the pH value to 9.5, 40% liquid alkali was consumed 2405 g, and the alkali mother liquor 5230 g was collected for use.

[0083] Example 8

[0084] The evaporation condensate obtained from examples 1 to 7 was combined and mixed uniformly, and was used for glyphosate washing. Glyphosate crystallization slurry 500 g was taken, the mother liquor was filtered out, 100 g of evaporation condensate was used for washing and filtering, and after drying, 110 g of glyphosate dry powder with a content of 95.5% was obtained. The washing water was combined with the acid mother liquor.

[0085] Example 9

[0086] The evaporation condensate obtained from examples 1 to 7 was combined and mixed uniformly, and was used for hydrochloric acid recovery. Hydrochloric acid 2 kg was prepared, and the quality of the hydrochloric acid was detected. The calcium and magnesium content was 10 ppm, and the content was 30.2%. The prepared hydrochloric acid was used for glyphosate acidolysis process. Glycine and formaldehyde were added under the condition of methanol as solvent and triethylamine as catalyst, and then were subjected to condensation reaction with dimethyl phosphite. The prepared hydrochloric acid was used for acidolysis. After dealcoholization, crystallization, washing, and drying, glyphosate was obtained with a yield of 76.5% and a content of 95.7%.

[0087] Comparative Example 1

[0088] The glyphosate acid mother liquor 1000g was put into a 2000ml three-necked flask, and the pressure was controlled at -0.09Mpa for evaporation. 450g of evaporation condensate water was collected, and the water quality of the evaporation condensate was detected. The pH value was 3.0, the organic nitrogen was 75ppm, and the total phosphorus was 1.1ppm. After crystallization of the concentrated mother liquor, 260g of triethylamine hydrochloride was filtered out and collected for standby use. The acidic concentrated mother liquor was 290g, and the pH value was adjusted to 9.5 using 40% liquid alkali. 295g of 40% liquid alkali was consumed to obtain 556.2g of alkali mother liquor, which was collected for standby use.

[0089] Comparative Example 2

[0090] The glyphosate acid mother liquor 1000g was put into a 2000ml three-necked flask, and 100g of sodium carbonate was added to adjust the pH value to 6. A small amount of precipitate appeared in the mother liquor, and the temperature was controlled at 50℃ for 20min to remove gas. The weight of the mother liquor was reduced by 42g. 110g of 40% liquid alkali was used to absorb the tail gas. 2g of 30% hydrogen peroxide was added to the absorption liquid, and the temperature was controlled at 90℃ for 20min for purification of the organic matter. After cooling and crystallization, 85g of sodium carbonate solid was recovered, and the filtrate was used for triethylamine recovery.

[0091] The pretreated mother liquor was concentrated by evaporation, and the pressure was controlled at -0.09Mpa for evaporation. The evaporation condensate water was collected, and when the weight of the condensate water reached 450g, the evaporation was stopped, and the temperature was lowered for crystallization. The water quality of the evaporation condensate was detected. The pH value was 10, the organic nitrogen was 22ppm, and the total phosphorus was 0.2ppm. The evaporation condensate was collected for standby use.

[0092] After crystallization of the concentrated mother liquor, 305.5g of triethylamine hydrochloride was filtered out and collected for standby use. The acidic concentrated mother liquor was 302.5g, and the pH value was adjusted to 9.5 using 40% liquid alkali. 248g of 40% liquid alkali was consumed to obtain 531.5g of alkali mother liquor, which was collected for standby use.

[0093] Comparative Example 3

[0094] The glyphosate acid mother liquor 1000g was put into a 2000ml three-necked flask, and 40% liquid alkali 650g was added to adjust the pH value to 9.5. The triethylamine 215g was recovered by static layering, and the alkali mother liquor 1435g was obtained. The pressure was controlled at -0.09Mpa for evaporation, and the evaporation condensate water was collected. When the weight of the condensate water reached 450g, the evaporation was stopped, and the temperature was lowered for crystallization. The water quality of the evaporation condensate was detected. The pH value was 12, the organic nitrogen was 85ppm, and the total phosphorus was 0.2ppm. The evaporation condensate was collected for standby use. After crystallization of the concentrated mother liquor, 185g of sodium chloride solid was filtered out and collected for standby use. The alkali concentrated mother liquor was 800g, which was collected for standby use.

[0095] The water quality of the evaporation condensate and the dry powder content of glyphosate washing material of the examples and comparative examples were statistically analyzed, and the results are shown in Table 1.

[0096] Table 1

[0097] Project pH Organic nitrogen / ppm Total phosphorus / ppm Example 1 7.5 12 0.1 Example 2 5.5 22 1.1 Example 3 6.5 19 1.0 Example 4 7.5 9 0.1 Example 5 6.9 6 0.1 Example 6 7.9 20 0.2 Example 7 7.3 11 0.1 Comparative Example 1 3 75 1.1 Comparative Example 2 10 22 0.2 Comparative Example 3 12 85 0.2

[0098] From Table 1, it can be seen that the evaporated condensate water recovered in Examples 1-7 has good quality, low organic nitrogen content, low total phosphorus, and neutral pH value, meeting the process requirements for washing material, hydrochloric acid recovery and chloromethane recovery in glyphosate production. In Comparative Example 1, the acid mother liquor was directly evaporated and concentrated, and the evaporated condensate water obtained had low pH value and high organic nitrogen content. In Comparative Example 2, the acid mother liquor was evaporated and concentrated after the pH value was adjusted to be higher than the technical index, and the evaporated condensate water obtained had high pH value. In Comparative Example 3, the acid mother liquor was evaporated and concentrated after the triethylamine was recovered by neutralization with liquid caustic soda, and the evaporated condensate water obtained had high pH value and high organic nitrogen content. The evaporated condensate liquid obtained in Comparative Examples 1-3 cannot be directly reused or subjected to biochemical treatment.

[0099] The above examples are only preferred technical solutions of the present application, and should not be regarded as a limitation of the present application. The examples in the present application and the features in the examples can be combined with each other as long as there is no conflict. The protection scope of the present application should be based on the technical solutions recited in the claims, and the equivalent replacement solutions of the technical features recited in the claims are within the protection scope. That is, the equivalent replacement improvement within this range is also within the protection scope of the present application.

Claims

1. A method for recovering process water from glyphosate acidic mother liquor, characterized in that, Includes the following steps: The glyphosate acidic mother liquor is obtained in the glycine method for synthesizing glyphosate. After hydrolysis and acid hydrolysis, the synthesis liquid is adjusted to pH 0.3-1.5 for crystallization, and then glyphosate wet powder and glyphosate acidic mother liquor are obtained through solid-liquid separation. Step 1. Pretreatment of acidic mother liquor: 1.1 Add glyphosate acidic mother liquor and sodium carbonate to the reactor. The mass ratio of glyphosate acidic mother liquor to sodium carbonate is 100:(1-10). Stir, circulate, and adjust the pH value to 2-5 to obtain pretreated mother liquor. 1.2 The pretreated mother liquor is degassed at a temperature of 25-75℃ and a pressure of -100kPa-0kPa to remove carbon dioxide and low-boiling organic matter. Liquid alkali or solid alkali is used to absorb the removed carbon dioxide and low-boiling organic matter to obtain an absorbent liquid. 1.3 Add a deodorizing agent to the absorbent liquid described in 1.2 to deodorize and eliminate the irritating odor of the absorbent liquid. Concentrate and crystallize to obtain a mixed liquid containing sodium carbonate hydrate and sodium bicarbonate hydrate microcrystals. 1.4 The mixture described in 1.3 shall be reused in 1.1; Step 2. Separate and recover the evaporated condensate and triethylamine hydrochloride from the pretreatment mother liquor: 2.1 The pretreated mother liquor after carbon dioxide removal is transferred to an evaporator for evaporation and concentration, and the evaporation condensate, triethylamine hydrochloride and concentrate are separated. 2.2 Collect the condensate from the evaporation and reuse it in the glyphosate production process; 2.3 The precipitated triethylamine hydrochloride can be sold or reacted with liquid alkali to recover triethylamine; 2.4 The concentrate is neutralized with liquid alkali to convert the residual triethylamine salt in the concentrate into triethylamine. The triethylamine is then recovered in layers. The remaining phosphorus-rich alkali mother liquor is used to further recover phosphorus resources, and wet oxidation is used to recover phosphate or incineration is used to produce pyrophosphate. Step 3: Evaporation and condensation water is recycled for use in the glyphosate production process: 3.1 Evaporation condensate is reused in the hydrochloric acid recovery process, replacing part or all of the soft water, absorbing hydrogen chloride gas, and the by-product hydrochloric acid can be used in the glyphosate acid hydrolysis process. 3.2 Evaporation condensate is reused in the chloromethane recovery process. The evaporation condensate replaces part or all of the soft water in the water washing tower to wash the organic components in the chloromethane tail gas, mainly methanol and methyl acetal. The washing liquid enters the recovery tower to recover the organic components. 3.3 Evaporated condensate is used to replace part or all of the soft water in the glyphosate washing process, and the washing water is recycled again in the crystallization solution.

2. The method according to claim 1, characterized in that, In step 1.1, the mass ratio of glyphosate acidic mother liquor to sodium carbonate is 100:(3-8).

3. The method according to claim 1, characterized in that, In step 1.1, sodium carbonate is used to adjust the pH of the acid mother liquor to 3.0-4.

0.

4. The method according to claim 1, characterized in that, In step 1.2, the degassing temperature of the pretreated mother liquor is 35-65℃; the degassing pressure is -90kPa to -50kPa.

5. The method according to claim 1, characterized in that, In step 1.2, liquid alkali is used to absorb carbon dioxide and regenerate it into sodium carbonate, with a concentration of 5%-50%.

6. The method according to claim 5, characterized in that, In step 1.2, the concentration of liquid alkali is 35%-45%.

7. The method according to claim 1, characterized in that, In step 1.3, the deodorizing agent is hydrogen peroxide or solid sodium peroxide, and 30% hydrogen peroxide is used for purification and deodorization treatment, with a mass ratio of 1:(100-500) to glyphosate mother liquor.

8. The method according to claim 1, characterized in that, In step 1.3, the deodorization temperature is 50-110℃.

9. The method according to claim 8, characterized in that, In step 1.3, the deodorization temperature is 60-90℃.

10. The method according to claim 1, characterized in that, In step 2.1, the evaporation rate of the pretreatment mother liquor is 10%-60%; In step 2.1, the evaporation temperature of the pretreatment mother liquor is 60-120℃, or the temperature is 60-70℃ under a negative pressure of 0.08-0.1Mpa.

11. The method according to claim 10, characterized in that, In step 2.1, the evaporation rate of the pretreatment mother liquor is 30%-50%; In step 2.1, the evaporation temperature of the pretreatment mother liquor is 100-110℃.

12. The method according to claim 1, characterized in that, In step 2.3, triethylamine hydrochloride is reacted with liquid alkali to recover triethylamine, and the neutralized pH value is 8-12.

13. The method according to claim 1, characterized in that, In step 3.1, the evaporated condensate is reused in the hydrochloric acid recovery process, and the mass ratio of evaporated condensate to hydrogen chloride is (1-5):1; In step 3.2, the evaporated condensate is reused in the chloromethane recovery process, and the COD value of the washing liquid is controlled at 50,000-200,000 ppm; In step 3.3, the evaporated condensate is recycled for the glyphosate washing process, and the mass ratio of evaporated condensate to glyphosate is (0.4-1.5):

1.

14. The method according to claim 13, characterized in that, In step 3.1, the evaporated condensate is reused in the hydrochloric acid recovery process, and the mass ratio of evaporated condensate to hydrogen chloride is (2-2.5):1; In step 3.2, the evaporated condensate is reused in the chloromethane recovery process, and the COD value of the washing liquid is controlled at 100,000-150,000 ppm; In step 3.3, the evaporated condensate is recycled for the glyphosate washing process, and the mass ratio of evaporated condensate to glyphosate is (0.6-1):1.

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