Method for recovering methylal from glycine glyphosate byproduct chloromethane
By adopting multi-stage adsorption and alkaline washing pretreatment technology in the production process of glycine glyphosate, the problem of poor recovery effect in chloromethane was successfully solved, achieving efficient recycling and cost-saving effects.
Patent Information
- Application Number
- CN202411616428.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-13
- Publication Date
- 2025-02-25
AI Technical Summary
The prior art has limited effect in recycling methylacetal in chloromethane during the production process of glycine glyphosate, and the distillation process equipment has high initial investment and large energy consumption, resulting in production costs and waste sewage discharge problems.
Multi-stage adsorption treatment is carried out in series by multiple adsorbers, combined with alkaline washing pretreatment and low-pressure steam desorption technology, and efficient recovery of formaldehyde is performed using non-polar macroporous adsorption resin.
It has achieved efficient recycling of methylacetal in chloromethane, reducing production energy consumption and waste sewage discharge, reducing sulfuric acid consumption, saving production costs, and increasing the secondary sales revenue of methylacetal.
Smart Images
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Abstract
Description
Technical Field
[0001] The invention relates to the field of methylal recovery, in particular to a method for recovering methylal from methyl chloride, a byproduct of glycine and glyphosate. Background Art
[0002] In the process of producing glyphosate by the glycine method, a large amount of byproduct methyl chloride is generated; the methyl chloride gas includes methanol, methylal, hydrogen chloride, dimethyl ether, air and other impurities, of which pure methyl chloride accounts for about 60% to 70% by volume; according to rough statistics, for every ton of glyphosate technical produced, about 500 kg of methyl chloride is produced. How to efficiently recover methylal and other substances in methyl chloride has an important impact on reducing production costs and improving the utilization rate of raw materials.
[0003] At present, the recovery process of chloromethane mainly uses a large amount of water for washing and absorption, but the treatment effect is relatively limited, and it will be accompanied by more energy consumption and wastewater discharge. Huang Jianjun et al. disclosed a process for continuous recovery of dimethyl phosphite-glyphosate co-produced tail gas, which mainly removes methylal and methanol in the mixed gas through multi-tower water washing; Patent CN110698320B discloses a continuous recovery device and continuous recovery process of glyphosate hydrolysis gas phase, which mainly uses a de-methanol tower, an absorption tower, a distillation tower and other devices, and uses a water washing and distillation method to remove hydrogen chloride and water in the glyphosate hydrolysis gas. Although this method can effectively recover the liquid phase components in chloromethane, the equipment involved in the distillation step is relatively large in the initial investment, resulting in a significant increase in production costs.
[0004] Therefore, developing an efficient recovery process for methylal from the by-product chloroform of glycine and glyphosate to obtain high-content, low-impurity chloroform while reducing production energy consumption and waste water discharge is an industry technical problem that urgently needs to be solved. Summary of the invention
[0005] In order to solve the above technical problems, the present invention proposes a method for recovering methylal from chloromethane, a byproduct of glycine glyphosate, which mainly comprises the following steps:
[0006] S1, adsorption treatment;
[0007] S2, desorption treatment;
[0008] S3, tail gas purge treatment;
[0009] S4. Spray treatment.
[0010] As an implementable case, the adsorption treatment step includes: passing the methyl chloride tail gas treated with alkali washing into an adsorber for adsorption treatment.
[0011] Furthermore, the adsorption treatment step includes: when the adsorber A1 and adsorber B2 are first started, the adsorber A1 is put into use in series, the adsorber B2 is subjected to primary adsorption treatment, and the adsorber B2 is subjected to secondary adsorption treatment; the methyl chloride tail gas that has been subjected to alkali washing is introduced into the adsorber A1, and after adsorption, it is sent to the adsorber B2 by the adsorption fan 6 for continued adsorption, and the tail gas after adsorption is discharged into the tail gas main pipe 11; when the adsorber A1 is saturated with adsorption, it is offline, and the adsorber B2 and adsorber C3 are switched to the adsorber B2 and adsorber C3, and the adsorber B2 is subjected to primary adsorption treatment, and the adsorber C3 is subjected to secondary adsorption treatment; when the adsorber B2 is saturated with adsorption, it is switched to the adsorber C3 and adsorber D4, and the adsorber C3 is subjected to primary adsorption treatment, and the adsorber D4 is subjected to secondary adsorption treatment; when the adsorber C3 is saturated with adsorption, it is switched to the adsorber D4 and adsorber A1; adsorber A1, adsorber B2, adsorber C3 and adsorber D4 are ... 4 are all acceptable: adsorption-desorption-adsorption, and cyclic use; after switching to adsorber D4 and adsorber A1, adsorber D4 performs primary adsorption treatment, and adsorber A1 performs secondary adsorption treatment; and so on, until all the adsorbers are saturated with adsorption.
[0012] As an implementable case, the volume concentration of methylal in the chloromethane tail gas treated with alkali washing is less than 10%.
[0013] Furthermore, the intake flow rate of the chloromethane tail gas treated with alkali washing is 800-1100 Nm 3 / h.
[0014] As an implementable case, the adsorption resins in adsorber A1, adsorber B2, adsorber C3, and adsorber D4 are all non-polar macroporous adsorption resins, and the non-polar macroporous adsorption resins include styrene exchange resins and / or polyacrylic acid exchange resins.
[0015] Furthermore, the volume of the adsorption resin in the adsorber A1, adsorber B2, adsorber C3, and adsorber D4 is 5 to 6 m 3 .
[0016] As an implementable case, the temperature of the adsorption treatment is 20-60°C.
[0017] As an implementable case, the adsorption treatment time is 60 to 120 minutes. When the adsorption time is reached, the system automatically switches to the desorption treatment stage.
[0018] In the prior art, the most common treatment method for the tail gas of glycine and glyphosate is distillation recovery. However, the initial cost of the equipment involved in the distillation process is relatively high, and the energy consumption in the recovery is large. In addition, the distillation process is mainly based on the separation of substances with different volatilities. Therefore, it is difficult to achieve complete separation for substances with similar volatilities. Therefore, the present invention creatively uses a method of connecting multiple adsorbers in series. The multi-stage series setting can more effectively adsorb methylal in chloromethane. In the series structure, each adsorber includes adsorber A1, adsorber B2, adsorber C3, and adsorber D4, which can adsorb methylal in the tail gas of chloromethane to a certain extent. In addition, the present invention generally preferably uses non-polar macroporous resins such as styrene exchange resins or polyacrylic acid exchange resins as adsorption resins. Non-polar adsorption resins are polymer materials without any functional groups obtained by polymerization of monomers with very small dipole moments. The surface hydrophobicity of the pores is relatively strong, and it can react with the hydrophobic parts of small molecules such as methylal, thereby effectively adsorbing organic matter in the chloromethane tail gas. However, due to the limited adsorption saturation of the adsorption resin, it is not easy to treat chloromethane tail gas with a high volume concentration of methylal. In the present invention, the chloromethane tail gas is subjected to a pretreatment step of alkali washing, which can effectively reduce the volume concentration of methylal in the chloromethane tail gas. Preferably, the chloromethane tail gas with a volume concentration of methylal less than 10% after alkali washing can be used in conjunction with a multi-stage series adsorption device to achieve more efficient tail gas treatment and methylal adsorption.
[0019] As an implementable case, the desorption treatment step includes: introducing low-pressure steam and increasing the temperature to perform desorption treatment.
[0020] Furthermore, the desorption treatment step includes: introducing low-pressure steam to heat the adsorption resin in the adsorber A1 that has been saturated with adsorption, and when the temperature reaches the desorption temperature, effective desorption begins, and the high-temperature desorbed gas is cooled by the condenser 7, and then transported to the oil-water separator 10 for stratification, the upper layer enters the methylal recovery tower 8 for recovery, and the lower water layer is sent to the wastewater system 9, and the condensed uncondensed gas returns to the front end of the adsorption fan 6 for re-adsorption until the desorption stage is completed; for adsorber B2, adsorber C3 and adsorber D4, the desorption treatment steps are the same.
[0021] As an practicable case, the desorption treatment time is 60-120 minutes.
[0022] As an practicable example, the temperature of the desorption treatment is 90-120°C.
[0023] As an implementable example, the pressure of the low-pressure steam in the desorption process does not exceed 35 kPa.
[0024] As an implementable case, the tail gas purge treatment step includes: after the desorption is completed, the purge fan 5 is started to purge the adsorber A1 and the residual desorbed gas in the desorption pipeline, and enters the oil-water separator 10 after condensation, and the purge gas returns to the front end of the adsorption fan 6 through the top of the condenser 7 for adsorption; for adsorber B2, adsorber C3 and adsorber D4, the tail gas purge steps are the same.
[0025] As an implementable case, the spray treatment includes: after the tail gas purge is completed, start the spray water to spray and cool the adsorber A1, the spray water enters the wastewater system 9 after condensation, and finally start the purge fan 5 to purge the free water in the adsorber A1; for adsorber B2, adsorber C3 and adsorber D4, the steps of the spray treatment are the same.
[0026] Beneficial Effects
[0027] (i) The present invention creatively adopts the steps of adsorption treatment, desorption treatment, tail gas purge treatment and spray treatment, which can effectively absorb methylal in the chloroform byproduct of glycine and glyphosate, avoid the operation of distillation, and the process cost is relatively low.
[0028] (ii) In the process of adsorption treatment, the present invention uses multiple adsorbers in series for joint adsorption, which can efficiently adsorb methylal in the methyl chloride tail gas, and the recovered methylal can be further processed and sold for a second time, thereby increasing corporate profits.
[0029] (III) Although the multi-stage adsorber connected in series can efficiently recover methylal in the chloromethane tail gas, the present invention still requires a pretreatment step of alkali washing the chloromethane tail gas to reduce the volume concentration of methylal in the chloromethane tail gas to less than 10%, so that the adsorber can achieve a better adsorption effect.
[0030] (IV) The present invention selects a specific non-polar large-pore adsorption resin, which can specifically recover methylal from methyl chloride, and the adsorption saturated adsorption resin can be effectively desorbed by steam heating, the desorption step is simple, and the cost is low; after adsorption, the volume concentration of methyl chloride in the methyl chloride tail gas is greater than 98%, and the volume concentration of methylal is less than 1%.
[0031] (V) The recovery process provided by the present invention can significantly reduce the volume concentration of methylal in the by-product chloromethane in the glyphosate production process, and reduce the sulfuric acid consumption in the subsequent chloromethane recovery section; based on the reduction of concentrated sulfuric acid consumption by 30 kg per ton of chloromethane tail gas, the annual recovery of chloromethane is 20,000 tons, 98% sulfuric acid is 490 yuan / t, and the sales price of dilute sulfuric acid is 500 yuan / t, the recovery process can be expected to save sulfuric acid raw materials and processing costs of 700,000 yuan / year; at the same time, the recovered methylal can generate additional sales revenue. Based on the annual recovery of 1,150 tons of methylal and the sales profit of methylal at 2,500 yuan / t, the estimated additional sales revenue is 1.4 million yuan / year, and the expenses of washing water, steam and wastewater treatment can be reduced, thereby improving the comprehensive benefits of the product. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Figure 1 It is a schematic diagram of the process flow of the adsorption treatment step in Examples 1-3 and Comparative Example 1; wherein: 1-adsorber A, 2-adsorber B, 3-adsorber C, 4-adsorber D, 5-purge fan, 6-adsorption fan, 7-condenser, 8-methylal recovery tower, 9-wastewater system, 10-oil-water separator, 11-exhaust main pipe.
[0033] Figure 2 It is a schematic diagram of the process flow of the desorption treatment step in Examples 1-3 and Comparative Example 1; wherein: 1-adsorber A, 2-adsorber B, 3-adsorber C, 4-adsorber D, 5-purge fan, 6-adsorption fan, 7-condenser, 8-methylal recovery tower, 9-wastewater system, 10-oil-water separator, 11-exhaust main pipe.
[0034] Figure 3 It is a process flow diagram of the tail gas purge treatment step in Examples 1-3 and Comparative Example 1; wherein: 1- adsorber A, 2- adsorber B, 3- adsorber C, 4- adsorber D, 5- purge fan, 6- adsorption fan, 7- condenser, 8- acetal recovery tower, 9- wastewater system, 10- oil-water separator, 11- tail gas main pipe.
[0035] Figure 4 It is a schematic diagram of the process flow of the spray treatment step in Examples 1-3 and Comparative Example 1; wherein: 1-adsorber A, 2-adsorber B, 3-adsorber C, 4-adsorber D, 5-purge fan, 6-adsorption fan, 7-condenser, 8-methylal recovery tower, 9-wastewater system, 10-oil-water separator, 11-exhaust main pipe. DETAILED DESCRIPTION
[0036] Example 1
[0037] This example proposes a method for recovering methylal from chloromethane, a byproduct of glycine glyphosate, which mainly includes the following steps:
[0038] S1. Adsorption treatment: At the initial start-up, adsorber A1 and adsorber B2 are put into use in series, adsorber A1 performs primary adsorption treatment, and adsorber B2 performs secondary adsorption treatment; the chloroform tail gas with a volume concentration of 90% chloroform and a volume concentration of 7% methylal after alkali washing is introduced into adsorber A1, and the air intake flow rate is 1000Nm 3 / h, after adsorption, it is sent to adsorber B2 by adsorption fan 6 for further adsorption, and the exhaust gas after adsorption is discharged into the exhaust main pipe 11; when adsorber A1 is saturated with adsorption and goes offline, it is switched to adsorber B2 and adsorber C3, adsorber B2 performs primary adsorption treatment, and adsorber C3 performs secondary adsorption treatment; when adsorber B2 is saturated with adsorption, it is switched to adsorber C3 and adsorber D4, adsorber C3 performs primary adsorption treatment, and adsorber D4 performs secondary adsorption treatment; when adsorber C3 is saturated with adsorption, it is switched to adsorber D4 and adsorber A1; adsorber A1, adsorber B2, adsorber C3 and adsorber D4 can all: adsorption-desorption-adsorption, and are cyclically used; after switching to adsorber D4 and adsorber A1, adsorber D4 4 for primary adsorption treatment, adsorber A1 for secondary adsorption treatment; and so on, until all the adsorbers are saturated with adsorption; wherein the adsorption temperature is 35°C, the adsorption time is 70 min, and the amount of adsorption resin in each adsorber is 5.6 m 3 ; When the adsorption time is reached, the system automatically switches to the desorption treatment stage;
[0039] S2, desorption treatment: low-pressure steam with a pressure of 33 kPa is introduced to raise the temperature of the adsorption resin in the adsorber A1 that has been saturated with adsorption to 90°C, and effective desorption begins. The desorption time is 75 minutes. The high-temperature desorbed gas is cooled by the condenser 7 and then transported to the oil-water separator 10 for stratification. The upper layer enters the methylal recovery tower 8 for recovery, and the lower water layer is sent to the wastewater system 9. The condensed uncondensed gas returns to the front end of the adsorption fan 6 for re-adsorption until the desorption stage is completed; for the adsorbers B 2, C 3 and D 4 that have been saturated with adsorption, the desorption steps are the same;
[0040] S3, tail gas purge treatment: after desorption is completed, start the purge fan 5 to purge the residual desorbed gas in the adsorber A1 and the desorption pipeline, and enter the oil-water separator 10 after condensation. The purge gas returns to the front end of the adsorption fan 6 through the top of the condenser 7 for adsorption; for adsorber B 2, adsorber C 3 and adsorber D 4, the tail gas purge steps are the same;
[0041] S4, spray treatment: after the tail gas purge is completed, start the spray water to spray and cool down the adsorber A1, and the spray water enters the wastewater system 9 after condensation, and finally start the purge fan 5 to purge the free water in the adsorber A1; for adsorber B2, adsorber C3 and adsorber D4, the steps of spray treatment are the same.
[0042] In this example, the methyl chloride gas content in the methyl chloride tail gas after adsorption is 99.1%, and the volume concentration of methylal is 0.5%; the volume concentration of methylal in the recovered methylal solution is 90.2%, and the volume concentration of methyl chloride is 0.08%.
[0043] The adsorption resin was purchased from Xi'an Jinwotai Environmental Protection Technology Co., Ltd. with the brand name innovate-G11.
[0044] Example 2
[0045] This example proposes a method for recovering methylal from chloromethane, a byproduct of glycine glyphosate, which mainly includes the following steps:
[0046] S1. Adsorption treatment: At the initial start-up, adsorber A1 and adsorber B2 are put into use in series, adsorber A1 performs primary adsorption treatment, and adsorber B2 performs secondary adsorption treatment; the chloroform tail gas with a volume concentration of 90% chloroform and a volume concentration of 7% methylal treated with alkali washing is introduced into adsorber A1, and the air intake flow rate is 800Nm 3 / h, after adsorption, it is sent to adsorber B2 by adsorption fan 6 for further adsorption, and the exhaust gas after adsorption is discharged into the exhaust main pipe 11; when adsorber A1 is saturated with adsorption and goes offline, it is switched to adsorber B2 and adsorber C3, adsorber B2 performs primary adsorption treatment, and adsorber C3 performs secondary adsorption treatment; when adsorber B2 is saturated with adsorption, it is switched to adsorber C3 and adsorber D4, adsorber C3 performs primary adsorption treatment, and adsorber D4 performs secondary adsorption treatment; when adsorber C3 is saturated with adsorption, it is switched to adsorber D4 and adsorber A1; adsorber A1, adsorber B2, adsorber C3 and adsorber D4 can all be: adsorption-desorption-adsorption, and recycled; after switching to adsorber D4 and adsorber A1, adsorber D4 4 for primary adsorption treatment, adsorber A1 for secondary adsorption treatment; and so on, until all the adsorbers are saturated with adsorption; the adsorption temperature is 40 ° C, the adsorption time is 100 min, and the amount of adsorption resin in each adsorber is 5.6 m 3 ; When the adsorption time is reached, the system automatically switches to the desorption treatment stage;
[0047] S2, desorption treatment: low-pressure steam with a pressure of 34 kPa is introduced to raise the temperature of the adsorption resin in the adsorber A1 that has been saturated with adsorption to 100°C, and effective desorption begins. The desorption time is 60 minutes. The high-temperature desorbed gas is cooled by the condenser 7 and then transported to the oil-water separator 10 for stratification. The upper layer enters the methylal recovery tower 8 for recovery, and the lower water layer is sent to the wastewater system 9. The condensed uncondensed gas returns to the front end of the adsorption fan 6 for re-adsorption until the desorption stage is completed; for the adsorbers B2, C3 and D4 that have been saturated with adsorption, the desorption steps are the same;
[0048] S3, tail gas purge treatment: after desorption is completed, start the purge fan 5 to purge the adsorber A1 and the residual desorbed gas in the desorption pipeline, and enter the oil-water separator 10 after condensation. The purge gas returns to the front end of the adsorption fan 6 through the top of the condenser 7 for adsorption; for adsorber B2, adsorber C3 and adsorber D4, the tail gas purge steps are the same;
[0049] S4, spray treatment: after the tail gas purge is completed, start the spray water to spray and cool down the adsorber A1, and the spray water enters the wastewater system 9 after condensation, and finally start the purge fan 5 to purge the free water in the adsorber A1; for adsorber B2, adsorber C3 and adsorber D4, the steps of spray treatment are the same.
[0050] In this example, the methyl chloride gas content in the methyl chloride tail gas after adsorption is 99.3%, and the volume concentration of methylal is 0.2%; the volume concentration of methylal in the recovered methylal solution is 91.2%, and the volume concentration of methyl chloride is 0.05%.
[0051] The adsorption resin was purchased from Xi'an Jinwotai Environmental Protection Technology Co., Ltd. with the brand name innovate-G11.
[0052] Example 3
[0053] This example proposes a method for recovering methylal from chloromethane, a byproduct of glycine glyphosate, which mainly includes the following steps:
[0054] S1. Adsorption treatment: At the initial start-up, adsorber A1 and adsorber B2 are put into use in series, adsorber A1 performs primary adsorption treatment, adsorber B2 performs secondary adsorption treatment; the chloroform tail gas with a volume concentration of 90% chloroform and a volume concentration of 7% methylal after alkali washing is introduced into adsorber A1, and the air intake flow rate is 1090Nm 3 / h, after adsorption, it is sent to adsorber B2 by adsorption fan 6 for further adsorption, and the exhaust gas after adsorption is discharged into the exhaust main pipe 11; when adsorber A1 is saturated with adsorption and goes offline, it is switched to adsorber B2 and adsorber C3, adsorber B2 performs primary adsorption treatment, and adsorber C3 performs secondary adsorption treatment; when adsorber B2 is saturated with adsorption, it is switched to adsorber C3 and adsorber D4, adsorber C3 performs primary adsorption treatment, and adsorber D4 performs secondary adsorption treatment; when adsorber C3 is saturated with adsorption, it is switched to adsorber D4 and adsorber A1; adsorber A1, adsorber B2, adsorber C3 and adsorber D4 can all be: adsorption-desorption-adsorption, and recycled; after switching to adsorber D4 and adsorber A1, adsorber D4 performs primary adsorption treatment, and adsorber A 1. Perform secondary adsorption treatment; and so on, until all the adsorbers are saturated with adsorption; the adsorption temperature is 50°C, the adsorption time is 70 minutes, and the amount of adsorption resin in each adsorber is 5.6 m 3 ; When the adsorption time is reached, the system automatically switches to the desorption treatment stage;
[0055] S2, desorption treatment: low-pressure steam with a pressure of 34 kPa is introduced to raise the temperature of the adsorption resin in the adsorber A1 that has been saturated with adsorption to 90°C, and effective desorption begins. The desorption time is 75 minutes. The high-temperature desorbed gas is cooled by the condenser 7 and then transported to the oil-water separator 10 for stratification. The upper layer enters the methylal recovery tower 8 for recovery, and the lower water layer is sent to the wastewater system 9. The condensed uncondensed gas returns to the front end of the adsorption fan 6 for re-adsorption until the desorption stage is completed; for the adsorbers B2, C3 and D4 that have been saturated with adsorption, the desorption steps are the same;
[0056] S3, tail gas purge treatment: after desorption is completed, start the purge fan 5 to purge the adsorber A1 and the residual desorbed gas in the desorption pipeline, and enter the oil-water separator 10 after condensation. The purge gas returns to the front end of the adsorption fan 6 through the top of the condenser 7 for adsorption; for adsorber B2, adsorber C3 and adsorber D4, the tail gas purge steps are the same;
[0057] S4, spray treatment: after the tail gas purge is completed, start the spray water to spray and cool down the adsorber A1, and the spray water enters the wastewater system 9 after condensation, and finally start the purge fan 5 to purge the free water in the adsorber A1; for adsorber B2, adsorber C3 and adsorber D4, the steps of spray treatment are the same.
[0058] In this example, the methyl chloride gas content in the methyl chloride tail gas after adsorption is 98.5%, and the volume concentration of methylal is 0.8%; the volume concentration of methylal in the recovered methylal solution is 90.0%, and the volume concentration of methyl chloride is 0.11%.
[0059] The adsorption resin was purchased from Xi'an Jinwotai Environmental Protection Technology Co., Ltd. with the brand name innovate-G11.
[0060] Comparative Example 1
[0061] This example proposes a method for recovering methylal from chloromethane, a byproduct of glycine glyphosate, which mainly includes the following steps:
[0062] S1. Adsorption treatment: At the initial start-up, adsorber A1 and adsorber B2 are put into use in series, adsorber A1 performs primary adsorption treatment, and adsorber B2 performs secondary adsorption treatment; the chloroform tail gas with a volume concentration of 85% chloroform and a volume concentration of 11% methylal after alkali washing is introduced into adsorber A1, and the air intake flow rate is 1000Nm 3 / h, after adsorption, it is sent to adsorber B2 by adsorption fan 6 for further adsorption, and the exhaust gas after adsorption is discharged into the exhaust main pipe 11; when adsorber A1 is saturated with adsorption and offline, it is switched to adsorber B2 and adsorber C3, adsorber B2 performs primary adsorption treatment, and adsorber C3 performs secondary adsorption treatment; when adsorber B2 is saturated with adsorption, it is switched to adsorber C3 and adsorber D4, adsorber C3 performs primary adsorption treatment, and adsorber D4 performs secondary adsorption treatment; when adsorber C3 is saturated with adsorption, it is switched to adsorber D4 and adsorber A1; adsorber A1, adsorber B2, adsorber C3 and adsorber D4 can all: adsorption-desorption-adsorption, and are cyclically used; after switching to adsorber D4 and adsorber A1, adsorber D4 4 for primary adsorption treatment, adsorber A1 for secondary adsorption treatment; and so on, until all the adsorbers are saturated with adsorption; the adsorption temperature is 35°C, the adsorption time is 70 min, and the amount of adsorption resin in each adsorber is 5.6 m 3 ; When the adsorption time is reached, the system automatically switches to the desorption treatment stage.
[0063] S2, desorption treatment: low-pressure steam with a pressure of 34 kPa is introduced to raise the temperature of the adsorption resin in the adsorber A1 that has been saturated with adsorption to 90°C, and effective desorption begins. The desorption time is 75 minutes. The high-temperature desorbed gas is cooled by the condenser 7 and then transported to the oil-water separator 10 for stratification. The upper layer enters the methylal recovery tower 8 for recovery, and the lower water layer is sent to the wastewater system 9. The condensed uncondensed gas returns to the front end of the adsorption fan 6 for re-adsorption until the desorption stage is completed; for the adsorbers B2, C3 and D4 that have been saturated with adsorption, the desorption steps are the same;
[0064] S3, tail gas purge treatment: after desorption is completed, start the purge fan 5 to purge the residual desorbed gas in the adsorber A1 and the desorption pipeline, and enter the oil-water separator 10 after condensation. The purge gas returns to the front end of the adsorption fan 6 through the top of the condenser 7 for adsorption; for adsorber B 2, adsorber C 3 and adsorber D 4, the tail gas purge steps are the same;
[0065] S4, spray treatment: after the tail gas purge is completed, start the spray water to spray and cool down the adsorber A1, and the spray water enters the wastewater system 9 after condensation, and finally start the purge fan 5 to purge the free water in the adsorber A1; for adsorber B2, adsorber C3 and adsorber D4, the steps of spray treatment are the same.
[0066] In this example, the methyl chloride gas content in the methyl chloride tail gas after adsorption is 94.9%, and the volume concentration of methylal is 3.7%; the volume concentration of methylal in the recovered methylal solution is 89.3%, and the volume concentration of methyl chloride is 0.19%.
[0067] The adsorption resin was purchased from Xi'an Jinwotai Environmental Protection Technology Co., Ltd. with the brand name innovate-G11.
[0068] In the above implementation case, the method for testing the volume concentration of methyl chloride gas is:
[0069] Column temperature: 40℃ in the initial stage, keep for 4 min (until the chloromethane peak is completely discharged); increase the temperature to 220℃ at a rate of 32℃ / min, keep for 2 min;
[0070] Gasification chamber temperature: 260°C;
[0071] Detector temperature: 260°C;
[0072] N2 flow rate: 3mL / min;
[0073] Hydrogen flow rate: 40mL / min
[0074] Injection volume: 3 μL;
[0075] Chloromethane mass fraction w1 = (A1 / methane i )×× alkane, where A1 is the peak area of methyl chloride; Σ chloro i The sum of the peak areas of each component and the retention time were 1.11min;
[0076] Methylal mass fraction w2 = (A2 / acetal i )××aldehyde, where A2 is the acetal peak area; Σ acetal i The sum of the peak areas of each component and the retention time are 1.34min.
[0077] in:
[0078] The process flow diagram of the adsorption treatment step in Examples 1-3 and Comparative Example 1 is as follows Figure 1 shown.
[0079] The process flow diagram of the desorption treatment step in Examples 1-3 and Comparative Example 1 is as follows: Figure 2 shown.
[0080] The process flow diagram of the tail gas purge treatment step in Examples 1-3 and Comparative Example 1 is as follows: Figure 3 shown.
[0081] The process flow diagram of the spray treatment step in Examples 1-3 and Comparative Example 1 is as follows: Figure 4 shown.
Claims
1. A method for recovering methylal from chloromethane, a byproduct of glycine and glyphosate, characterized in that: The main steps include: S1, adsorption treatment; S2, desorption treatment; S3, tail gas purge treatment; S4. Spray treatment.
2. The method for recovering methylal from the glycine glyphosate byproduct methyl chloride according to claim 1, characterized in that: The adsorption treatment step comprises: introducing the methyl chloride tail gas treated with alkali washing into an adsorber for adsorption treatment.
3. The method for recovering methylal from the glycine glyphosate byproduct methyl chloride according to claim 2, characterized in that: The volume concentration of methylal in the chloromethane tail gas treated with alkali is less than 10%.
4. The method for recovering methylal from the glycine glyphosate byproduct methyl chloride according to claim 2, characterized in that: The intake flow rate of the chloromethane tail gas treated with alkali washing is 800-1100 Nm 3 / h.
5. The method for recovering methylal from the byproduct methyl chloride of glycine glyphosate according to any one of claims 1 to 4, characterized in that: The temperature of the adsorption treatment is 20-60°C.
6. The method for recovering methylal from the byproduct methyl chloride of glycine glyphosate according to claim 1, characterized in that: The desorption treatment step comprises: introducing low-pressure steam, increasing the temperature, and performing desorption treatment.
7. The method for recovering methylal from the byproduct methyl chloride of glycine glyphosate according to claim 6, characterized in that: The pressure of the low-pressure steam in the desorption process does not exceed 35 kPa.
8. The method for recovering methylal from the byproduct methyl chloride of glycine glyphosate according to claim 6, characterized in that: The temperature of the desorption treatment is 90-120°C.
9. The method for recovering methylal from the byproduct methyl chloride of glycine glyphosate according to claim 1, characterized in that: The tail gas purge treatment step comprises: After desorption is completed, the purge fan (5) is started to purge the residual desorbed gas in the adsorber A (1) and the desorption pipeline, and enters the oil-water separator (10) after condensation. The purge gas returns to the front end of the adsorption fan (6) through the top of the condenser (7) for adsorption. For adsorber B (2), adsorber C (3) and adsorber D (4), the tail gas purge steps are the same.
10. The method for recovering methylal from methyl chloride, a byproduct of glycine glyphosate, according to claim 1, characterized in that: The spray treatment comprises: After the tail gas purge is completed, the spray water is started to spray and cool the adsorber A (1). After condensation, it enters the wastewater system 9, and finally the purge fan (5) is started to purge the free water in the adsorber A (1); For adsorber B (2), adsorber C (3) and adsorber D (4), the steps of the spray treatment are the same.