Deep purification device and method for glyphosate byproduct chloromethane

Abstract

The invention provides a glyphosate byproduct chloromethane deep purification device and method.The purification device comprises a compressor, the compressor is connected with a first-stage condenser, the top of the first-stage condenser is connected with a second-stage condenser, the top of the second-stage condenser is connected with a gas-liquid separator, and the top of the gas-liquid separator is connected with a first-stage water scrubber; the top of the first-stage washing tower is connected with a first-stage washing gas-liquid separator, the first-stage washing gas-liquid separator is connected with a second-stage washing tower, and the top of the second-stage washing tower is connected with a demisting tower. The purification method comprises the steps of pressurized condensation, first-stage water washing, second-stage water washing and demisting drying. According to the invention, organic impurities and hydrogen chloride are efficiently removed through a synergistic process of pressurized condensation, secondary water washing and demisting, and the consumption of concentrated sulfuric acid in the subsequent drying process is reduced.

Description

Technical Field

[0001] This invention belongs to the field of glyphosate production by-product recovery technology, specifically relating to a deep purification device and method for glyphosate by-product chloromethane. Background Technology

[0002] Glyphosate and its raw material dimethyl phosphite both produce chloromethane, which contains certain components such as methanol, methylal, dimethyl ether, hydrogen chloride, and chloroethane. Impurities are typically removed through water washing and alkaline washing. However, in practical production, large-scale water washing is impractical, as it would generate substantial wastewater requiring treatment. After water washing, the chloromethane is further dehydrated and purified using concentrated sulfuric acid. Due to the numerous and complex components of chloromethane impurities, existing processes cannot effectively purify and absorb organic impurities. Consequently, most gaseous organic impurities are removed using concentrated sulfuric acid, resulting in high sulfuric acid consumption and the generation of large amounts of dilute sulfuric acid. With increasingly stringent environmental regulations, the cost of treating dilute sulfuric acid will continue to rise. Therefore, a deep purification method that can efficiently remove organic impurities and reduce concentrated sulfuric acid consumption is urgently needed. Summary of the Invention

[0003] This invention aims to provide a device and method for deep purification of glyphosate byproduct chloromethane. Through a synergistic process of "pressurized condensation-secondary water washing-demisting," it efficiently removes organic impurities and hydrogen chloride, reducing the consumption of concentrated sulfuric acid in the subsequent drying process. The technical solution is as follows: A deep purification device for glyphosate byproduct chloromethane includes a compressor connected to a primary condenser, a secondary condenser connected to the top of the primary condenser, a gas-liquid separator connected to the top of the secondary condenser, a primary water scrubbing tower connected to the top of the gas-liquid separator, a primary water scrubbing gas-liquid separator connected to the top of the primary water scrubbing tower, a secondary water scrubbing tower connected to the top of the secondary water scrubbing tower, and a demister tower connected to the top of the secondary water scrubbing tower.

[0004] Furthermore, the bottom of the secondary water washing tower is connected to a secondary water washing heat exchanger via a secondary water washing pump, and the secondary water washing heat exchanger is connected to the primary water washing tower.

[0005] Furthermore, a soft water inlet is provided above the secondary water washing tower; the outlet of the secondary water washing heat exchanger is connected above the primary water washing tower.

[0006] Furthermore, the bottoms of the primary condenser, secondary condenser, gas-liquid separator, and primary water washing gas-liquid separator are all connected to the bottom of the primary water washing tower; the bottom of the primary water washing tower is connected to the inlet of the secondary water washing heat exchanger.

[0007] Furthermore, the compressor is connected to a crude chloromethane gas pipeline at its front end, and the crude chloromethane gas pipeline is equipped with an inlet shut-off valve; a reflux regulating valve is provided between the compressor inlet pipeline and the outlet pipeline; the secondary water washing tower is connected to an outlet regulating valve for controlling the liquid level of the secondary water washing tower at its rear end; and the demister tower is connected to an exhaust regulating valve for stabilizing the system pressure at its rear end.

[0008] This invention also provides a method for deep purification of glyphosate byproduct chloromethane, using the above-mentioned apparatus, comprising the following steps: (1) Pressurized condensation: The chloromethane byproduct of glyphosate enters the compressor through the inlet pipe and is compressed to 0.3-0.5MPa. The gas phase then enters the first-stage condenser and the second-stage condenser in sequence. After condensation, it enters the gas-liquid separator. The separated liquid phase impurities are discharged, and the gas phase enters the first-stage water washing tower. (2) Primary water washing: The gas phase enters the primary water washing tower from the bottom of the primary water washing tower. The secondary circulating water washing liquid, which is heated to 30-40℃ by the secondary water washing water heat exchanger, is sprayed from the top of the primary water washing tower. The gas phase and the secondary circulating water washing liquid come into countercurrent contact. (3) Secondary water washing: The gas phase after primary water washing is discharged from the top of the primary water washing tower and enters the primary water washing gas-liquid separator. The separated gas phase enters the secondary water washing tower from the bottom and comes into countercurrent contact with the 20-30℃ fresh demineralized water entering from the top of the tower. After the secondary water washing liquid is heated by the secondary water washing water heat exchanger, part of it flows back to the primary water washing tower and part of it is collected. (4) Demisting and drying: The gas phase after secondary water washing is discharged from the top of the secondary water washing tower and enters the demisting tower to remove the mist droplets entrained in the gas phase. The demisted gas phase enters the concentrated sulfuric acid drying process.

[0009] Furthermore, the cooling medium of the first-stage condenser is circulating water, and the outlet temperature of the circulating water is 40-50℃; the cooling medium of the second-stage condenser is chilled water, and the outlet temperature of the chilled water is 10-20℃.

[0010] Furthermore, the primary water washing tower is equipped with a 304 stainless steel packing area, which is located between the gas phase inlet and the water washing liquid inlet. The secondary water washing tower is equipped with a 304 stainless steel packing area, which is located between the gas phase inlet and the water washing liquid inlet.

[0011] Furthermore, in step (2), the spray density of the secondary circulating water washing solution is 8-12 m³ / (m²·h), preferably 10 m³ / (m²·h); the primary water washing mainly removes hydrogen chloride and some methanol, wherein the hydrogen chloride removal rate is ≥99%; In step (3), the temperature of the fresh desalinated water is 20-30℃, and the liquid-to-gas ratio is 1:(5-7), preferably 1:6; the secondary water washing deeply absorbs methyl acetal and dimethyl ether, wherein the dimethyl ether removal rate is ≥85% and the methyl acetal removal rate is ≥90%; the water washing liquid of the collected part contains 5-10% methanol.

[0012] Furthermore, in step (4), the demister is equipped with a 316L stainless steel wire mesh demister with a mesh size of 110-130 mesh, preferably 120 mesh; after demistering, the gas phase water content is <0.5g / Nm³.

[0013] Pressurized condensation process: The by-product chloromethane is first compressed to 0.3-0.5 MPa by a screw compressor (pressurization can increase the solubility of organic impurities in water; for example, the solubility of dimethyl ether at 0.4 MPa is 3-4 times higher than at atmospheric pressure). Then, it passes through a primary condenser (cooled to 40-50℃ by circulating water) and a secondary condenser (cooled to 10-20℃ by chilled water) to condense some high-boiling-point impurities (such as methanol) into a liquid phase. After separation by a gas-liquid separator, it is discharged, and the residual methanol in the gas phase is reduced to below 0.3%.

[0014] Secondary water washing process: Primary water washing: The gas phase enters the packed tower and comes into countercurrent contact with the secondary circulating water washing liquid, which has been heated to 30-40℃ by a heat exchanger (spray density 10m³ / (m²·h)). It mainly removes hydrogen chloride (neutralization reaction) and some methanol (increased solubility), with a hydrogen chloride removal rate ≥99%. Secondary water washing: The gas phase after primary water washing enters another packed tower and comes into countercurrent contact with fresh demineralized water (20-30℃) (liquid-to-gas ratio 1:6) to deeply absorb methyl acetal, dimethyl ether, etc., with a dimethyl ether removal rate of ≥85% and a methyl acetal removal rate of ≥90%. After being cooled by a heat exchanger, part of the secondary water washing liquid is returned to the primary water washing tower (to reduce fresh water consumption), and part is collected (containing 5-10% methanol, which can be recycled).

[0015] Defogging process: After being washed with water, the gas phase enters the demister tower and is then processed by a 316L stainless steel wire mesh demister (120 mesh) to remove entrained droplets (reducing the water content to below 0.5 g / Nm³), thus preventing droplets from being carried into the subsequent drying process to dilute concentrated sulfuric acid.

[0016] Control logic: The compressor stabilizes the outlet pressure (fluctuation ≤ ±0.02MPa) through frequency conversion (30-50Hz) and reflux regulating valve. The liquid level in the secondary water washing tower is controlled at 40% (±5%) by the outlet regulating valve to ensure stable spraying effect; The total system pressure is controlled at 0.3 MPa by the regulating valve at the outlet of the demister tower to avoid pressure fluctuations affecting the absorption efficiency.

[0017] The beneficial effects of this invention are as follows: By using the apparatus and method provided by this invention, the total removal rates of dimethyl ether and methylal in glyphosate by-product chloromethane reach over 85% and 90%, respectively, solving the problem of insufficient removal of organic impurities by existing water washing methods; concentrated sulfuric acid consumption is reduced by 55-60%, waste sulfuric acid production is reduced by over 50%, and the annual waste acid disposal cost is reduced by approximately RMB 2 million (based on a 100,000-ton / year plant); the secondary water washing extract contains 5-10% methanol, which can be reused as a raw material in production, improving resource utilization; through multi-stage control, the system pressure and liquid level fluctuations are ≤±5%, and the purity of purified chloromethane is stable at over 99.5%. Attached Figure Description

[0018] Figure 1 A schematic diagram of the device structure of the present invention.

[0019] The diagram shows the following components: 1. Compressor; 2. Primary condenser; 3. Secondary condenser; 4. Gas-liquid separator; 5. Primary water washing tower; 6. Primary water washing gas-liquid separator; 7. Secondary water washing heat exchanger; 8. Secondary water washing pump; 9. Secondary water washing tower; 10. Demisting tower; 11. Inlet shut-off valve; 12. Return flow regulating valve; 13. Outlet regulating valve; 14. Exhaust regulating valve. Detailed Implementation

[0020] The embodiments of the present invention will be described in detail below with reference to the examples. The following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

[0021] Example 1 A deep purification device for glyphosate byproduct chloromethane includes a compressor 1, a primary condenser 2 connected to the compressor 1, a secondary condenser 3 connected to the top of the primary condenser 2, a gas-liquid separator 4 connected to the top of the secondary condenser 3, a primary water scrubbing tower 5 connected to the top of the gas-liquid separator 4, a primary water scrubbing gas-liquid separator 6 connected to the top of the primary water scrubbing tower 5, a secondary water scrubbing tower 9 connected to the top of the secondary water scrubbing tower 9, and a demisting tower 10 connected to the top of the secondary water scrubbing tower 9.

[0022] Furthermore, the bottom of the secondary water washing tower 9 is connected to the secondary water washing heat exchanger 7 via the secondary water washing extraction pump 8, and the secondary water washing heat exchanger 7 is connected to the primary water washing tower 5.

[0023] Furthermore, a soft water inlet is provided above the secondary water washing tower 9; the outlet of the secondary water washing heat exchanger 7 is connected above the primary water washing tower 5.

[0024] Furthermore, the bottoms of the primary condenser 2, the secondary condenser 3, the gas-liquid separator 4, and the primary water washing gas-liquid separator 6 are all connected to the bottom of the primary water washing tower 5; the bottom of the primary water washing tower 5 is connected to the inlet of the secondary water washing heat exchanger 7.

[0025] Furthermore, the compressor 1 is connected to a crude chloromethane gas pipeline at its front end, and an inlet shut-off valve 11 is provided on the crude chloromethane gas pipeline; a reflux regulating valve 12 is provided between the inlet pipeline and the outlet pipeline of the compressor 1; an outlet regulating valve 13 for controlling the liquid level of the secondary water washing tower 9 is connected to the rear end of the secondary water washing tower 9; and an exhaust regulating valve 14 for stabilizing the system pressure is connected to the rear end of the demister tower 10.

[0026] Example 2 Using the apparatus described in Example 1, taking the byproduct chloromethane (flow rate 800 Nm³ / h) of a 100,000-ton / year glyphosate plant as an example, the implementation steps are as follows: (1) Pressurized condensation: Crude chloromethane (containing 2.5% methanol, 0.6% dimethyl ether, 0.3% hydrogen chloride, and 2% methyl acetal) is compressed to 0.4 MPa by compressor 1, enters the first-stage condenser 2 to be cooled to 45°C, and then enters the second-stage condenser 3 to be cooled to 15°C. The liquid phase (containing 15% methanol, with a flow rate of about 50 kg / h) is separated by gas-liquid separator 4, and the methanol in the gas phase is reduced to 0.2%.

[0027] (2) First-stage water washing: The gas phase enters the bottom of the first-stage water washing tower 5 and comes into countercurrent contact with the circulating water washing liquid (from the second-stage water washing water heat exchanger 7) sprayed from the top of the first-stage water washing tower 5 at 35°C. The spray density of the circulating water washing liquid is 10 m³ / (m²·h). Hydrogen chloride is completely absorbed. After the first-stage water washing, the methanol content in the gas phase drops to 0.1%.

[0028] (3) Secondary water washing: The gas phase enters the gas-liquid separator 6 of the primary water washing and the separated gas phase enters the bottom of the secondary water washing tower 9 and comes into contact with the 25°C fresh water (liquid-to-gas ratio 1:6) sprayed from the top of the secondary water washing tower 9; in the gas phase after secondary water washing, the dimethyl ether is reduced to 0.09% and the methyl acetal is reduced to 0.05%; the secondary water washing liquid (45°C) is discharged from the bottom of the secondary water washing tower 9, 60% is cooled to 35°C by the secondary water washing water heat exchanger 7 and returned to the primary water washing tower 5, and the remaining 40% is collected. The collected liquid contains 8% methanol and can be used as raw material for production.

[0029] (4) Demisting and drying: The gas phase after secondary water washing enters the demisting tower 10 for demisting, and then enters the concentrated sulfuric acid drying process. The consumption of concentrated sulfuric acid is reduced from 100 kg / ton of chloromethane to 45 kg / ton, and the amount of waste sulfuric acid generated is reduced by 55%. The purity of the dried chloromethane is 99.67%.

Claims

1. A deep purification device for glyphosate byproduct chloromethane, characterized in that, Includes a compressor (1), the compressor (1) is connected to a primary condenser (2), the top of the primary condenser (2) is connected to a secondary condenser (3), the top of the secondary condenser (3) is connected to a gas-liquid separator (4), the top of the gas-liquid separator (4) is connected to a primary water scrubbing tower (5), the top of the primary water scrubbing tower (5) is connected to a primary water scrubbing gas-liquid separator (6), the primary water scrubbing gas-liquid separator (6) is connected to a secondary water scrubbing tower (9), and the top of the secondary water scrubbing tower (9) is connected to a demisting tower (10).

2. The deep purification device for glyphosate by-product chloromethane according to claim 1, characterized in that, The bottom of the secondary water washing tower (9) is connected to the secondary water washing heat exchanger (7) via the secondary water washing pump (8), and the secondary water washing heat exchanger (7) is connected to the primary water washing tower (5).

3. The deep purification device for glyphosate by-product chloromethane according to claim 1, characterized in that, The secondary water washing tower (9) is provided with a soft water inlet above it; the primary water washing tower (5) is connected to the outlet of the secondary water washing heat exchanger (7) above it.

4. The deep purification device for glyphosate by-product chloromethane according to claim 1, characterized in that, The bottoms of the primary condenser (2), secondary condenser (3), gas-liquid separator (4) and primary water washing gas-liquid separator (6) are all connected to the bottom of the primary water washing tower (5); the bottom of the primary water washing tower (5) is connected to the inlet of the secondary water washing heat exchanger (7).

5. The deep purification device for glyphosate by-product chloromethane according to claim 1, characterized in that, The compressor (1) is connected to a crude chloromethane gas pipeline at its front end, and an inlet shut-off valve (11) is provided on the crude chloromethane gas pipeline; a reflux regulating valve (12) is provided between the inlet pipeline and the outlet pipeline of the compressor (1); the secondary water washing tower (9) is connected to an outlet regulating valve (13) for controlling the liquid level of the secondary water washing tower (9) at its rear end; and the demister tower (10) is connected to an exhaust regulating valve (14) for stabilizing the system pressure at its rear end.

6. A method for deep purification of chloromethane byproduct of glyphosate, characterized in that, Using the apparatus according to any one of claims 1-5, the steps include: (1) Pressurized condensation: The by-product chloromethane of glyphosate enters the compressor (1) through the inlet pipe and is compressed to 0.3-0.5MPa. The gas phase enters the first-stage condenser (2) and the second-stage condenser (3) in sequence. After condensation, it enters the gas-liquid separator (4). The separated liquid phase impurities are discharged, and the gas phase enters the first-stage water washing tower (5). (2) Primary water washing: The gas phase enters the primary water washing tower (5) from the bottom and is heated to 30-40℃ by the secondary water washing water heat exchanger (7). The secondary circulating water washing liquid is sprayed from the top of the primary water washing tower (5), and the gas phase and the secondary circulating water washing liquid come into countercurrent contact. (3) Secondary water washing: The gas phase after primary water washing is discharged from the top of the primary water washing tower (5) and enters the primary water washing gas-liquid separator (6). The separated gas phase enters the secondary water washing tower (9) from the bottom and comes into countercurrent contact with the 20-30℃ fresh demineralized water entering from the top of the tower. After the secondary water washing liquid is heated by the secondary water washing water heat exchanger (7), part of it flows back to the primary water washing tower (5) and part of it is collected. (4) Demisting and drying: The gas phase after secondary water washing is discharged from the top of the secondary water washing tower (9) and enters the demisting tower (10) to remove the mist droplets entrained in the gas phase. The demisted gas phase enters the concentrated sulfuric acid drying process.

7. The method for deep purification of glyphosate by-product chloromethane according to claim 6, characterized in that, The cooling medium of the first-stage condenser (2) is circulating water, and the outlet temperature of the circulating water is 40-50℃; the cooling medium of the second-stage condenser (3) is chilled water, and the outlet temperature of the chilled water is 10-20℃.

8. The method for deep purification of glyphosate by-product chloromethane according to claim 6, characterized in that, The primary water washing tower (5) is equipped with a 304 stainless steel packing area, which is located between the gas phase inlet and the water washing liquid inlet. The secondary water washing tower (9) is equipped with a 304 stainless steel packing area, which is located between the gas phase inlet and the water washing liquid inlet.

9. A method for deep purification of glyphosate byproduct chloromethane according to claim 6, characterized in that, In step (2), the spray density of the secondary circulating water washing solution is 8-12 m³ / (m²·h), preferably 10 m³ / (m²·h); the primary water washing mainly removes hydrogen chloride and some methanol, wherein the hydrogen chloride removal rate is ≥99%; In step (3), the temperature of the fresh desalinated water is 20-30℃, and the liquid-to-gas ratio is 1:(5-7), preferably 1:6; the secondary water washing deeply absorbs methyl acetal and dimethyl ether, wherein the dimethyl ether removal rate is ≥85% and the methyl acetal removal rate is ≥90%; the water washing liquid of the collected part contains 5-10% methanol.

10. A method for deep purification of glyphosate by-product chloromethane according to claim 6, characterized in that, In step (4), the demisting tower (10) is equipped with a 316L stainless steel wire mesh demister with a mesh size of 110-130 mesh, preferably 120 mesh; after demisting, the gas phase water content is <0.5g / Nm³.

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