CN215209190U - Recovery system of methyl chloride in glyphosate tail gas - Google Patents
Recovery system of methyl chloride in glyphosate tail gas Download PDFInfo
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- CN215209190U CN215209190U CN202023289207.5U CN202023289207U CN215209190U CN 215209190 U CN215209190 U CN 215209190U CN 202023289207 U CN202023289207 U CN 202023289207U CN 215209190 U CN215209190 U CN 215209190U
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Abstract
The utility model discloses a recovery system of methyl chloride in glyphosate tail gas includes compressor, condensing equipment, vapour and liquid separator, membrane separator and pressure swing adsorption ware in proper order according to the commodity circulation direction, vapour and liquid separator's noncondensable gas export links to each other with the entry of membrane separator, the infiltration side export of membrane separator links to each other with the entry of compressor, what the membrane separator held back the side export and links to each other with the entry of pressure swing adsorption ware, the desorption gas play of pressure swing adsorption wareThe port is connected to the inlet of the compressor and the membrane separator comprises a separation membrane having a preferential permeability to methyl chloride. The utility model discloses integrated compression condensation, membrane separation and pressure swing adsorption technique, recovery process security is high, and the high efficiency realizes that the chloromethane rate of recovery can reach more than 99.99%, and chloromethane content is less than 20mg/m in the purified gas3The emission requirement of reaching the standard is met, a cold source at the temperature of-35 ℃ is not needed, and the investment of equipment and pipelines and the energy consumption are obviously reduced.
Description
Technical Field
The utility model relates to a chemical industry separation technology field, concretely relates to system for retrieve methyl chloride from glyphosate production technology tail gas.
Background
Glyphosate is a broad-spectrum biocidal herbicide, and a large amount of tail gas containing chloromethane is generated in the production process of glyphosate, and the direct emission of glyphosate can pollute the atmospheric environment; meanwhile, methyl chloride is also a chemical solvent and methylating agent, and is a main raw material for preparing organic silicon polymers and other chlorinated hydrocarbons. Therefore, the recovery of methyl chloride from glyphosate tail gas has important economic and social environmental benefits.
The byproduct tail gas generated in the synthesis of glyphosate by the alkyl ester method contains large amount of methyl chloride, methylal, methanol, hydrogen chloride, moisture, air and the like. At present, the main recovery process is to recover liquid methyl chloride by compressing and condensing (generally adopting three-stage condensation with the temperature of-35 ℃) after washing and drying tail gas. The recovery rate in the process is generally 85-95%, and the non-condensable gas still contains 7-10V% of chloromethane, which cannot meet the requirement of direct discharge.
SUMMERY OF THE UTILITY MODEL
The utility model discloses to the proposition of above problem, and the recovery system of chloromethane in a glyphosate tail gas of research and design. The utility model discloses a technical means as follows:
the utility model provides a recovery system of methyl chloride in glyphosate tail gas, includes compressor, condensing equipment, vapour and liquid separator, membrane separator and pressure swing adsorber according to the commodity circulation direction in proper order, the noncondensable gas outlet of vapour and liquid separator links to each other with the entry of membrane separator, the infiltration side export of membrane separator links to each other with the entry of pressure swing adsorber, the desorption gas outlet of pressure swing adsorber links to each other with the entry of compressor, the membrane separator includes the separation membrane that has the preferential permeability to methyl chloride.
Furthermore, the condensing device sequentially comprises a primary condenser, a reheater and a secondary condenser according to the material flow direction, the non-condensable gas outlet of the gas-liquid separator is connected with the cold medium inlet of the reheater, and the cold medium outlet of the reheater is connected with the inlet of the membrane separator.
Furthermore, the medium of the primary condenser is circulating water, and the medium of the secondary condenser is saline water with the temperature of-15 ℃.
Furthermore, the pressure swing adsorber at least comprises two adsorption towers, the adsorption towers alternately perform adsorption and desorption, and an adsorbent with a separation coefficient of more than 6 is arranged in the adsorption towers.
Further, the adsorbent is 13X molecular sieve and activated carbon.
Compared with the prior art, a recovery system of methyl chloride in glyphosate tail gas have following advantage:
1. the membrane separation process is intrinsically safe, the compression condensation and pressure swing adsorption processes are high in safety, and the whole integrated recovery process is safe and reliable;
2. the integrated compression condensation, membrane separation and pressure swing adsorption technology can efficiently realize that the recovery rate of the chloromethane can reach more than 99.99 percent, and the content of the chloromethane in the purified gas is lower than 20mg/m3The emission standard is met;
3. compared with the existing compression and three-stage condensation (the temperature of the three-stage condensation is-35 ℃), the common frozen brine/refrigerant with the temperature not lower than-15 ℃ is adopted as a cold source, the-35 ℃ cold source is not required, and the equipment and the pipeline are made of common carbon steel materials, so that the investment and the energy consumption of the equipment and the pipeline are obviously reduced.
Drawings
Fig. 1 is a schematic diagram of a recovery system for methyl chloride in glyphosate tail gas according to an embodiment of the present invention.
FIG. 2 is a graph showing the change of condensation temperature with pressure when the concentration of methyl chloride in the non-condensable gas reached 19V%.
Detailed Description
A method for recovering methyl chloride in glyphosate tail gas sequentially comprises a compression condensation process, a membrane separation process and a pressure swing adsorption process, and comprises the following steps: in the process of compression and condensation, the tail gas of the glyphosate production process is compressed and condensed, the pressure is increased to 0.7MPaG-1.0MPaG, the tail gas is condensed until the concentration of methyl chloride in the non-condensable gas is higher than the upper explosion limit, and gas-liquid separation is carried out to obtain a liquid methyl chloride product and the non-condensable gas; the non-condensable gas enters a membrane separation process, the concentration of methyl chloride on the interception side of the membrane separation process is lower than the lower explosion limit, and the gas on the permeation side of the membrane separation process returns to a compression condensation process; and (3) introducing the intercepted gas in the membrane separation process into a pressure swing adsorption process, and controlling the concentration of the methyl chloride in the desorbed gas in the pressure swing adsorption process to be higher than the upper explosion limit.
The chloromethane is inflammable explosive gas (the explosion limit is 8.1V% -17.4V%), and the concentration of the chloromethane is controlled to be higher than the upper explosion limit or lower than the lower explosion limit, so that the whole integrated recovery process is safe and reliable. Preferably, the condensation process is controlled to condense the methyl chloride in the non-condensable gas to a concentration of more than 19V%. The concentration of methyl chloride on the interception side in the separation process of the membrane is controlled to be less than 5V%, and the concentration of desorbed gas is controlled to be more than 19V% in the pressure swing adsorption process. Condensing to not lower than-8 ℃ in the compression and condensation process. The control of the concentration of methyl chloride at the interception side in the membrane separation process is realized by controlling the cutting rate of the membrane, the pressure swing adsorption process uses an adsorbent with the separation coefficient of more than 6, and the concentration of methyl chloride in the desorbed gas is higher than the upper explosion limit by controlling the concentration of enrichment.
In a preferred embodiment, the condensation process comprises a primary condensation process, a reheating process and a secondary condensation process, wherein the non-condensable gas in the gas-liquid separation process and the output gas in the primary condensation process are subjected to heat exchange in the reheating process to reheat the non-condensable gas, and the reheated non-condensable gas enters the membrane separation process, wherein the condensation temperature in the secondary condensation process is not lower than-8 ℃. The tail gas is pressurized by a compressor, the temperature is gradually reduced to the secondary condensation temperature by a primary condenser, a reheater and a secondary condenser, and then the tail gas enters a gas-liquid separator for gas-liquid separation to obtain a liquid methyl chloride product and non-condensable gas with the concentration of the methyl chloride higher than the upper explosion limit; the non-condensable gas and the gas output by the first-stage condenser are subjected to heat exchange in a reheater to obtain reheated non-condensable gas, and the reheated non-condensable gas enters a membrane separation process.
In the compression and condensation process, the lower the secondary condensation temperature is, the higher the liquefaction rate is, and the lower the concentration of methyl chloride in the non-condensable gas is. The utility model discloses in, accessible control second grade condensing temperature makes the chloromethane concentration in the noncondensable gas be higher than the explosion upper limit. FIG. 2 shows the condensation temperature as a function of pressure for a methyl chloride concentration in the non-condensable gas of up to 19V%, which is above the upper explosive limit. Therefore, in the condensation pressure range of 0.7MPaG to 1.0MPaG, the concentration of the methyl chloride in the non-condensable gas can be ensured to be higher than the upper explosion limit as long as the condensation temperature is not lower than-8 ℃.
In the membrane separation process, the reheated non-condensable gas obtained in the compression and condensation process enters a membrane separator, and an organic hydrocarbon separation membrane which preferentially permeates methyl chloride components is arranged in the membrane separator. The permeation side obtains the chloromethane-rich gas which is higher than the upper explosion limit, and the chloromethane-rich gas returns to the compression and condensation process for recycling; the lean chloromethane gas with the concentration lower than the lower explosion limit is obtained at the interception side and enters the pressure swing adsorption process. The permeation of methyl chloride gas from the high pressure side of the membrane to the low pressure permeate side, which can be considered as an expansion process, has a joule-thomson effect, and the temperature of the gas is gradually reduced. The temperature on the permeate side of the membrane will drop by 5-8 deg.C and the temperature on the tail gas side of the membrane will drop by 6-15 deg.C relative to the inlet gas temperature. The concentration of the methyl chloride in the permeation gas is increased by 10V-30V% and is higher than the upper explosion limit, and the concentration of the methyl chloride in the tail gas is reduced to be lower than 5V% and is lower than the lower explosion limit. Since the temperature of the gas in the membrane separation process is gradually lowered without additional energy input, it is intrinsically safe to experience the explosive range of the gas during the membrane separation process.
In the membrane separation process, the cutting rate of the membrane is defined as the flow rate of permeation gas/the flow rate of raw material gas, and the higher the cutting rate is, the larger the permeation gas amount of methyl chloride is, and the lower the concentration of methyl chloride on the interception side is. The utility model discloses a cutting rate of controlling diaphragm guarantees that the chloromethane concentration that the side was held back to the membrane is less than the explosion lower limit. Table 1 shows the correspondence between condensation temperature, pressure and membrane cutting rate when the concentration of methyl chloride on the membrane rejection side reached 5V% (below the lower explosion limit). It can be seen that when the condensation pressure is in the range of 0.7MPaG to 1.0MPag and the condensation temperature is not lower than-8 ℃, the concentration of methyl chloride on the intercepted side can be ensured to be lower than the lower explosion limit as long as the condensation temperature is higher than the corresponding cutting rate. In actual work, the film cutting rate can be improved by increasing the film area.
TABLE 1 comparison table of membrane separation cutting rate at different condensation pressures and temperatures when the concentration of chloromethane at the membrane interception side is 5% (lower than the lower explosion limit)
In the pressure swing adsorption process, the poor chloromethane gas obtained in the membrane separation process enters a pressure swing adsorber for further separation and recovery, and because the concentration of chloromethane after membrane separation is greatly reduced and is lower than the lower explosion limit, the heat generated in the adsorption process is low, and the safety of the adsorption process is greatly improved. Purified gas with the concentration lower than the emission standard is obtained after pressure swing adsorption and is directly discharged. The desorption process is a heat absorption process, the temperature of the gas is reduced, meanwhile, the concentration of the chloromethane in the desorption gas is enriched by 6-10 times compared with that of the inlet gas, the concentration of the desorption gas is generally 20-40V% and is higher than the upper explosion limit, and the desorption gas returns to the compression and condensation process for recycling.
In the pressure swing adsorption process, the adsorbent is firstly screened, the pore size distribution test and the static and dynamic adsorption performance test are carried out, and the selective separability of the different adsorbents on the adsorption of the chloromethane, the nitrogen and the oxygen under different working conditions is determined. The utility model discloses well selection separation coefficient is at the adsorbent more than 6 for chloromethane can enrich more than 6 times than admitting air in the desorption gas, and concentration reaches more than 20V%, is higher than the explosion upper limit. The preferred adsorbent of the utility model is 13X molecular sieve and active carbon.
As shown in fig. 1, a recovery system of methyl chloride in glyphosate tail gas, is used for realizing the utility model discloses a recovery method of methyl chloride in glyphosate tail gas, according to the commodity circulation direction in proper order including compressor 1, condensing equipment, vapour and liquid separator 5, membrane separator 6 and pressure swing adsorber 7, the noncondensable gas export of vapour and liquid separator 5 links to each other with the entry of membrane separator 6, the infiltration side export of membrane separator 6 links to each other with the entry of compressor 1, the interception side export of membrane separator 6 links to each other with the entry of pressure swing adsorber 7, the desorption gas export of pressure swing adsorber 7 links to each other with the entry of compressor 1, membrane separator 6 includes the separation membrane that has the preferential permeability to methyl chloride, preferred organic hydrocarbon separation membrane.
The condensing device comprises a primary condenser 2, a reheater 3 and a secondary condenser 4 in sequence according to the material flow direction, a non-condensable gas outlet of the gas-liquid separator 5 is connected with a cooling medium inlet of the reheater 3, and a cooling medium outlet of the reheater 3 is connected with an inlet of the membrane separator 6. In this embodiment, the medium of the first-stage condenser 2 is circulating water, and the medium of the second-stage condenser 4 is brine at-15 ℃.
The pressure swing adsorber 7 at least comprises two adsorption towers, the adsorption towers alternately perform adsorption and desorption, an adsorbent with a separation coefficient of more than 6 is arranged in the adsorption towers, so that methyl chloride in desorbed gas can be enriched by more than 6 times compared with inlet gas, the concentration reaches more than 20V%, and is higher than the upper explosion limit, and the preferred adsorbent is 13X molecular sieve and activated carbon.
Example 1
The embodiment discloses a method for recovering methyl chloride in glyphosate tail gas, wherein the gas content of raw material gas is 845m3Hr, pressure of 0.08MPa, temperature of 30 deg.C, composition as follows:
| components | CH3Cl | N2 | O2 | CO2 | CH4 |
| Composition (V%) | 65.83 | 28.48 | 4.75 | 0.76 | 0.19 |
As shown in fig. 1, the raw material gas a of this embodiment firstly enters the compressor 1 to be pressurized to 0.80MPaG, and then the temperature is gradually reduced to the secondary condensation temperature of-8 ℃ through the primary condenser 2, the reheater 3 and the secondary condenser 4, and then enters the gas-liquid separator 5 to be subjected to gas-liquid separation. The liquid methyl chloride product f is obtained at the bottom, and the methyl chloride content in the top non-condensable gas g is 21.14 percent and is higher than the upper explosion limit.The-8 ℃ non-condensable gas g and the output gas c of the first-stage condenser 2 at 40 ℃ are subjected to heat exchange in a reheater 3 to obtain reheated non-condensable gas h, the reheated non-condensable gas h enters a membrane separator 6 with an organic hydrocarbon separation membrane with preferential permeability to chloromethane, and chloromethane-rich gas i is obtained at the permeation side, the content of chloromethane is 36.02 percent, the gas is further away from the upper explosion limit, and the gas returns to a compressor 1 for recycling; the trapped side is used to obtain chloromethane-poor gas j, the chloromethane content of which is 4.95 percent and is lower than the lower explosion limit. The chlorine-poor methane gas j enters a pressure swing adsorber 7 for further separation and recovery, and the content of the methyl chloride in the obtained purified gas l is about 16mg/m3The air can be directly discharged when meeting the national emission standard; the desorption gas k rich in methyl chloride, the content of the methyl chloride is 30.26 percent and is higher than the upper explosion limit, and the desorption gas k returns to the compressor 1 for recycling.
The material balance table of this example is as follows:
example 2
The embodiment discloses a method for recovering methyl chloride in glyphosate tail gas, wherein the gas content of raw gas is 560m3Hr, pressure of 0.08MPa, temperature of 30 deg.C, composition as follows:
| components | CH3Cl | N2 | O2 | CO2 | CH4 |
| Composition (V%) | 77.69 | 19.12 | 1.53 | 1.53 | 0.13 |
As shown in fig. 1, the raw material gas a of this embodiment firstly enters the compressor 1 to be pressurized to 0.75MPaG, and then the temperature is gradually reduced to the secondary condensation temperature of 10 ℃ through the primary condenser 2, the reheater 3 and the secondary condenser 4, and then enters the gas-liquid separator 5 to be subjected to gas-liquid separation. The liquid methyl chloride product f is obtained at the bottom, and the methyl chloride content in the top non-condensable gas g is 41.75 percent and is higher than the upper explosion limit. The 10 ℃ noncondensable gas g and the 40 ℃ gas c output by the first-stage condenser 2 are subjected to heat exchange in a reheater 3 to obtain reheated noncondensable gas h, the reheated noncondensable gas h enters a membrane separator 6 with an organic hydrocarbon separation membrane with preferential permeability to chloromethane, and chloromethane-rich gas i is obtained at the permeation side, wherein the content of chloromethane is 53.17 percent and is far away from the upper explosion limit, and the gas is returned to a compressor 1 for recycling; the trapped side is used to obtain chloromethane-poor gas j, the chloromethane content of which is 4.08 percent and is lower than the lower explosion limit. The chlorine-poor methane gas j enters a pressure swing adsorber 7 for further separation and recovery, and the content of the methyl chloride in the obtained purified gas l is about 18mg/m3The air can be directly discharged when meeting the national emission standard; the desorbed gas k rich in methyl chloride, the content of the methyl chloride of which is 26.20 percent and is higher than the upper explosion limit, returns to the compressor 1 for recycling.
The material balance table of this example is as follows:
the embodiment of the utility model provides an in each material chloromethane content all be outside explosion limit scope. The recovery rate of the chloromethane in the whole process reaches 99.99 percent, and the tail gas is discharged up to the standard.
Example 3
The embodiment discloses a recovery system of methyl chloride in glyphosate tail gas. As shown in fig. 1, a raw material gas a firstly enters a compressor 1 for pressurization, then the temperature is gradually reduced to the secondary condensation temperature through a primary condenser 2, a reheater 3 and a secondary condenser 4, and then the raw material gas enters a gas-liquid separator 5 for gas-liquid separation, so as to obtain a liquid methyl chloride product f and a non-condensable gas g with the concentration of the methyl chloride higher than the upper explosion limit. The non-condensable gas g and the gas c output by the first-stage condenser 2 are subjected to heat exchange in a reheater 3 to obtain reheated non-condensable gas h, the reheated non-condensable gas h enters a membrane separator 6 with an organic hydrocarbon separation membrane with preferential permeability to methyl chloride, and a methyl chloride-rich gas i is obtained at the permeation side and returns to a compressor 1 for recycling; the trapped side obtains the lean chloromethane j with the concentration lower than the lower explosion limit, and the lean chloromethane j enters a pressure swing adsorber 7 for further separation and recovery. Directly discharging the obtained purified gas l with the concentration of the chloromethane lower than the discharge standard; the desorbed gas k with the concentration higher than the explosion limit is returned to the compressor 1 for recycling.
The above-mentioned embodiments are only for describing the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention, and various modifications and improvements made by those skilled in the art without departing from the design spirit of the present invention should fall into the protection scope defined by the claims of the present invention.
Claims (5)
1. The recovery system of methyl chloride in glyphosate tail gas is characterized by comprising a compressor, a condensing device, a gas-liquid separator, a membrane separator and a pressure swing adsorber in sequence according to the material flow direction, wherein a noncondensable gas outlet of the gas-liquid separator is connected with an inlet of the membrane separator, an outlet on the permeation side of the membrane separator is connected with an inlet of the compressor, an outlet on the interception side of the membrane separator is connected with an inlet of the pressure swing adsorber, a desorption gas outlet of the pressure swing adsorber is connected with an inlet of the compressor, and the membrane separator comprises a separation membrane with preferential permeability to methyl chloride.
2. The system for recovering methyl chloride from glyphosate tail gas according to claim 1, wherein the condensing device comprises a primary condenser, a reheater and a secondary condenser in sequence according to the material flow direction, the non-condensable gas outlet of the gas-liquid separator is connected with the cold medium inlet of the reheater, and the cold medium outlet of the reheater is connected with the inlet of the membrane separator.
3. The system for recovering methyl chloride from glyphosate tail gas according to claim 2, wherein the medium of the primary condenser is circulating water, and the medium of the secondary condenser is brine at-15 ℃.
4. The system for recovering methyl chloride from glyphosate tail gas according to claim 1, 2 or 3, characterized in that the pressure swing adsorber comprises at least two adsorption towers, the adsorption towers alternately perform adsorption and desorption, and an adsorbent with a separation coefficient of more than 6 is arranged in the adsorption towers.
5. The system for recovering methyl chloride from glyphosate tail gas according to claim 4, wherein the adsorbent is 13X molecular sieve and activated carbon.
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| CN202023289207.5U CN215209190U (en) | 2020-12-30 | 2020-12-30 | Recovery system of methyl chloride in glyphosate tail gas |
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| CN202023289207.5U CN215209190U (en) | 2020-12-30 | 2020-12-30 | Recovery system of methyl chloride in glyphosate tail gas |
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