CN117717878A - Ionic liquid and method for efficiently absorbing toluene waste gas at normal pressure - Google Patents
Ionic liquid and method for efficiently absorbing toluene waste gas at normal pressure Download PDFInfo
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- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 title claims abstract description 531
- 239000002608 ionic liquid Substances 0.000 title claims abstract description 79
- 238000000034 method Methods 0.000 title claims abstract description 68
- 239000002912 waste gas Substances 0.000 title claims abstract description 37
- 238000010521 absorption reaction Methods 0.000 claims abstract description 76
- 239000007789 gas Substances 0.000 claims abstract description 39
- 238000003795 desorption Methods 0.000 claims abstract description 32
- IQQRAVYLUAZUGX-UHFFFAOYSA-N 1-butyl-3-methylimidazolium Chemical compound CCCCN1C=C[N+](C)=C1 IQQRAVYLUAZUGX-UHFFFAOYSA-N 0.000 claims abstract description 21
- 239000007788 liquid Substances 0.000 claims abstract description 16
- 238000000746 purification Methods 0.000 claims abstract description 13
- 238000007664 blowing Methods 0.000 claims description 16
- 239000000047 product Substances 0.000 claims description 16
- 238000007872 degassing Methods 0.000 claims description 13
- 239000012043 crude product Substances 0.000 claims description 9
- 238000001704 evaporation Methods 0.000 claims description 5
- 230000008020 evaporation Effects 0.000 claims description 5
- 238000004064 recycling Methods 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 2
- 238000010992 reflux Methods 0.000 claims description 2
- 238000000926 separation method Methods 0.000 claims description 2
- 238000001816 cooling Methods 0.000 claims 2
- 239000006096 absorbing agent Substances 0.000 claims 1
- 239000002250 absorbent Substances 0.000 abstract description 22
- 230000002745 absorbent Effects 0.000 abstract description 22
- 230000008929 regeneration Effects 0.000 abstract description 10
- 238000011069 regeneration method Methods 0.000 abstract description 10
- 239000002904 solvent Substances 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 10
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 7
- 238000010926 purge Methods 0.000 description 6
- 238000009833 condensation Methods 0.000 description 5
- 230000005494 condensation Effects 0.000 description 5
- 238000005516 engineering process Methods 0.000 description 4
- 238000005265 energy consumption Methods 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- MQIUGAXCHLFZKX-UHFFFAOYSA-N Di-n-octyl phthalate Natural products CCCCCCCCOC(=O)C1=CC=CC=C1C(=O)OCCCCCCCC MQIUGAXCHLFZKX-UHFFFAOYSA-N 0.000 description 1
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 description 1
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 239000000809 air pollutant Substances 0.000 description 1
- 231100001243 air pollutant Toxicity 0.000 description 1
- 238000003915 air pollution Methods 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- BJQHLKABXJIVAM-UHFFFAOYSA-N bis(2-ethylhexyl) phthalate Chemical compound CCCCC(CC)COC(=O)C1=CC=CC=C1C(=O)OCC(CC)CCCC BJQHLKABXJIVAM-UHFFFAOYSA-N 0.000 description 1
- 238000007084 catalytic combustion reaction Methods 0.000 description 1
- 239000013064 chemical raw material Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000002440 industrial waste Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 150000002892 organic cations Chemical class 0.000 description 1
- 238000005504 petroleum refining Methods 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- HXJUTPCZVOIRIF-UHFFFAOYSA-N sulfolane Chemical compound O=S1(=O)CCCC1 HXJUTPCZVOIRIF-UHFFFAOYSA-N 0.000 description 1
- 229920003002 synthetic resin Polymers 0.000 description 1
- 239000000057 synthetic resin Substances 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 125000003944 tolyl group Chemical group 0.000 description 1
- 230000001988 toxicity Effects 0.000 description 1
- 231100000419 toxicity Toxicity 0.000 description 1
- 239000012855 volatile organic compound Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- Gas Separation By Absorption (AREA)
Abstract
The invention provides an ionic liquid for efficiently absorbing toluene waste gas at normal pressure and a method thereof, wherein the method adopts the ionic liquid [ Bmim ]][PF 6 ]、[Bmim][BF 4 ]、[Bmim][NTf 2 ]One of them is used as toluene absorbent, and passed through toluene absorption tower to separate out toluene from waste gas, and dissolved in ionic liquid so as to obtain purified gas and ionAnd (5) sub-liquid absorption liquid. The ionic liquid absorption liquid is desorbed to obtain ionic liquid containing a small amount of toluene, and then the ionic liquid is subjected to normal pressure stripping and purification, so that the toluene content in the ionic liquid is reduced from 0.9% -1.5% to below 0.0004%, and the process heat load can be reduced by about 70% -90%. The invention optimizes the pressure of the toluene absorption tower and the toluene stripping tower, and the energy cost and the total annual cost of the whole process are the lowest. The desorption temperature of the adopted ionic liquid regeneration process is 120-169 ℃, and the ionic liquid can be heated by low-pressure steam. The desorption temperature of the traditional ionic liquid absorption process is 310 ℃, and superheated steam needs to be consumed. Compared with the traditional process, the desorption temperature of the invention is reduced by more than 45 percent.
Description
Technical Field
The invention relates to the field of VOCs treatment, in particular to an ionic liquid and a method for efficiently absorbing toluene waste gas at normal pressure.
Background
Toluene is an important chemical raw material, and has low boiling point (boiling point 110.6 ℃), easy volatilization and certain toxicity. If the toluene content in the waste gas is too high, serious harm is caused to human body and environment. The national standards GB 31570-2015, GB 31572-2015 and GB 31571-2015 issued by the current ecological environment department require that the toluene content in air pollutants of petroleum refining industry, petrochemical industry and synthetic resin industry is lower than 15mg/m 3 . For the purification treatment of toluene-containing waste gas, methods including activated carbon adsorption, thermal decomposition, condensation, solvent absorption and the like, and in addition, researchers have developed novel treatment technologies such as a biomembrane method, an ozone decomposition method, a catalytic combustion method, a plasma decomposition method and the like. Among them, the solvent absorption technology is to separate and recover gas mixtures by utilizing the different solubilities of different gases in selected absorbents. Toluene absorption technology transfers toluene from a gas phase to a liquid phase through treatment modes such as temperature change, pressure change and the like, and then the absorption liquid is subjected to desorption treatment to recover the toluene, and meanwhile, the solvent is regenerated and recycled. The absorption method is suitable for toluene waste gas with lower concentration and larger gas flow, has the advantages of low cost, simple operation, environmental friendliness, resource conservation and the like, and is a main flow mode for treating toluene waste gas at present.
The absorption method solvent mainly comprises an organic solvent and an ionic liquid, wherein the ionic liquid absorbent is used as a novel green solvent, generally refers to an organic salt absorbent consisting of controllable organic cations and anions, which has the advantages of controllable structure, high thermal stability,The ionic liquid is extremely weak in volatility, good in toluene solubility and low in regeneration energy consumption, has a good application prospect in toluene absorption, and is a current mainstream research direction by taking the ionic liquid as an absorbent. In the absorbent and application of the toluene in the recovered industrial waste gas disclosed in CN 109364695A, a composite solvent consisting of polyethylene glycol dimethyl ether (NHD) and N-methylpyrrolidone (NMP) or sulfolane or dioctyl phthalate is used as an absorbent, the absorbent is used for obtaining purified gas and absorbing rich liquid, and the rich liquid can be reused after reduced pressure distillation and regeneration. The method has low absorption efficiency of the p-toluene, only 88.1-93.1%, and the toluene content in the purified gas is still very high and exceeds the national emission standard (15 mg/m) 3 ) The loss rate of the solvent reaches 3.56%, the lost solvent is easy to cause secondary pollution to the atmosphere, and meanwhile, the purity of the toluene obtained by condensation does not reach the industrial grade standard. CN 107715651a discloses a high-efficiency low-loss solvent and flow path for absorbing toluene, which uses NMP as an absorbent, and the process comprises an absorption tower and two regeneration towers. The lower section of the absorption tower firstly adopts NMP as a solvent to absorb and remove toluene in waste gas, and the tail gas after the absorption treatment can carry a small amount of NMP to enter the upper section of the absorption tower, and then adopts water as a solvent to absorb the NMP. The absorption rich liquid is respectively fed into a regeneration tower (1) and a regeneration tower (2) to regenerate the solvent. The absorption rate of the upper section and the lower section of the absorption tower of the scheme is only 98.5%, the mass fraction of the NMP serving as the absorbent regenerated by the two regeneration towers is lower and is only 99.7% and 99.8%, and the absorption performance of the absorption tower can be influenced, so that the toluene content in the purified gas is increased. Meanwhile, the purity of toluene obtained by desorption in the scheme does not reach the industrial grade standard.
In view of the above-mentioned shortcomings, an ionic liquid absorbent and a treatment method capable of realizing high-efficiency absorption of toluene waste gas under normal pressure condition are urgently needed in the industry at present.
Disclosure of Invention
The problems of high energy consumption, high material consumption and secondary air pollution in the toluene absorption process based on organic solvents are main bottlenecks for limiting the green development of absorption technologies. The non-volatile and highly efficient absorption properties of ionic liquids are of great value to solve this problem. However, the existing ionic liquid absorption process has high absorption pressure, the toluene content in the regenerated ionic liquid is higher, so that the consumption of the ionic liquid is higher, the temperature and the energy consumption of the ionic liquid in the regeneration process are higher, and a large amount of superheated steam is required to be consumed. The invention aims to provide an ionic liquid absorbent and a process method capable of efficiently treating toluene waste gas under the condition of normal pressure absorption, so that tail gas reaches the national allowable emission standard, and meanwhile, the process also requires the purification of toluene to reach 99.5% of industrial grade products, and resources are efficiently recovered.
The invention provides an ionic liquid for efficiently absorbing toluene waste gas at normal pressure and a method thereof, wherein the method adopts the ionic liquid [ Bmim ]][PF 6 ]、[Bmim][BF 4 ]、[Bmim][NTf 2 ]One of them is used as toluene absorbent, and passed through toluene absorption tower to separate out toluene from waste gas, and dissolved in ionic liquid so as to obtain the invented product which can meet the national discharge standard of 15mg/m 3 And an ionic liquid absorption liquid containing high-concentration toluene. And then, desorbing the ionic liquid absorption liquid containing high-concentration toluene through a toluene desorber to obtain a toluene crude product and an ionic liquid containing a small amount of toluene, wherein the toluene crude product is subjected to a pressurizing condensation flash evaporation process to obtain a toluene product with the mass fraction of 99.5%. The ionic liquid containing a small amount of toluene enters the top of the toluene stripping tower, the blowing and degassing obtained by the split flow of the splitter enters from the bottom of the stripping tower, the small amount of toluene in the ionic liquid is stripped, the toluene content in the ionic liquid can be reduced from 0.9% -1.5% to below 0.0004%, the waste gas at the top of the stripping tower flows back, and the waste gas is mixed with the toluene waste gas and then enters the absorption tower for re-absorption.
Specifically, the invention is realized by the following technical means:
the invention discloses an ionic liquid for efficiently absorbing toluene waste gas at normal pressure, which comprises the following components:
[Bmim][PF 6 ]、[Bmim][BF 4 ]、[Bmim][NTf 2 ]any one of them is used as toluene absorbent.
The invention also discloses a method for absorbing toluene at normal pressure by adopting the ionic liquid, which comprises the following steps:
(1) Toluene waste gas enters a toluene absorption tower from the bottom of the tower and flows in the absorption tower from bottom to top, meanwhile, ionic liquid is fed from a top feed inlet of the absorption tower and contacts with waste gas in the absorption tower in countercurrent from top to bottom in the absorption tower, and after the toluene waste gas is absorbed by the ionic liquid, the toluene content in the top purified gas is less than or equal to 15mg/m 3 And (5) discharging after reaching the standard. The ionic liquid absorption liquid containing high-concentration toluene flows out from the bottom of the absorption tower. Wherein the theoretical plate number of the toluene absorption tower is 10-30 plates, the operating pressure is 1bar, and the feeding temperature is 35 ℃.
(2) And (3) heating the ionic liquid absorption liquid obtained in the step (1) by a heat exchanger, then enabling the ionic liquid absorption liquid to enter a toluene desorption tower for flash separation, extracting a toluene crude product from the top of the desorption tower, and enabling the ionic liquid regenerated for the first time to flow out from the bottom of the desorption tower. Wherein the temperature of the heat exchanger is 120-169 ℃, and the operating pressure of the toluene desorption tower is 0.1-0.5 bar.
(3) Pressurizing the toluene crude product obtained in the step (2) through a compressor, condensing to 35 ℃ through a heat exchanger, and then entering a flash tank for flash evaporation and purification. And (3) obtaining a toluene product with the purity of 99.5% at the bottom of the flash tank, and refluxing the rest of non-condensable gas from the top of the flash tank, mixing with toluene waste gas, and then feeding the mixture into a toluene absorption tower for re-absorption. Wherein the outlet pressure of the compressor is 1-9 bar.
(4) And (3) carrying out secondary purification on the ionic liquid subjected to primary regeneration in the step (2) through a toluene stripping tower, so that the toluene content in the ionic liquid is reduced from 0.9% -1.5% to below 0.0004%. The ionic liquid regenerated for the first time is pressurized to 1bar through a centrifugal pump, and then enters a toluene stripping tower from a tower top feed inlet and flows from top to bottom. The purified gas discharged from the top of the tower in the step (1) is shunted by a shunt to obtain blowing and degassing, the blowing and degassing enters from the bottom of the blowing and degassing tower, and the blowing and degassing contacts with the ionic liquid in the blowing and degassing tower in a countercurrent way from bottom to top, the toluene waste gas obtained from the top of the blowing and degassing tower flows back, is mixed with the toluene waste gas and then enters a toluene absorption tower to be absorbed again, and the secondarily purified ionic liquid flows back to the ionic liquid feeding port of the absorption tower for recycling. Wherein the theoretical plate number of the toluene stripping tower is 3-10 plates, the operating pressure is 1bar, and the feeding temperature is 120-169 ℃.
The invention has the beneficial effects that:
1. the method adopts the ionic liquid recovered from the toluene stripping tower and the toluene desorbing tower to carry out secondary purification, so that the toluene content in the ionic liquid is reduced from 0.9 to 1.5 percent to below 0.0004 percent, and the heat load of the process can be reduced by about 70 to 90 percent.
2. The invention optimizes the pressure of the toluene absorption tower and the toluene stripping tower, and when the pressure is 1bar, the energy cost and the total annual cost of the whole process are the lowest.
3. The invention adopts ionic liquid [ Bmim ]][PF 6 ]、[Bmim][BF 4 ]、[Bmim][NTf 2 ]The toluene absorbent has high absorption efficiency on toluene, and the absorbent is not volatilized and lost, and does not cause secondary pollution to the atmosphere.
4. The desorption temperature of the ionic liquid regeneration process adopted by the invention is 120-169 ℃, and the ionic liquid can be heated by low-pressure steam. The desorption temperature of the traditional ionic liquid absorption process is 310 ℃, and superheated steam needs to be consumed. Compared with the traditional process, the desorption temperature of the invention is reduced by more than 45 percent.
5. The method is used for purifying the toluene crude product obtained by desorption through a pressurizing condensation flash evaporation process, so that the toluene crude product reaches the industrial grade standard, and the recycling recovery of toluene waste gas is realized.
Drawings
FIG. 1 is a process flow diagram of the present invention (atmospheric absorption of toluene);
FIG. 2 is a comparative process flow for high pressure absorption of toluene.
Detailed Description
The flow chart of the method of the invention is shown in fig. 1, which comprises the following steps: the method comprises the steps of a toluene absorption tower, a toluene desorption tower, a toluene stripping tower, a flash tank, a compressor, a pressure reducing valve, a heat exchanger and a centrifugal pump, wherein the bottom of the toluene absorption tower is an exhaust gas feed inlet, the top of the toluene absorption tower is an ionic liquid feed inlet, a tower top product is purified gas reaching national emission standards, the tower bottom product is an ionic liquid absorption liquid containing toluene, the ionic liquid absorption liquid containing toluene is conveyed to the toluene desorption tower for desorption, the tower top product is a toluene crude product, the toluene product with the mass fraction of 99.5% is obtained through a compression condensation flash evaporation process, the tower bottom product is an ionic liquid containing a small amount of toluene, and the ionic liquid is subjected to secondary purification through the toluene stripping tower, so that the high-purity ionic liquid can be obtained.
Example 1
The flow of exhaust gas is as follows in the process flow shown in figure 1: 15000m 3 And/h, toluene content in the waste gas: 10000mg/m 3 Toluene absorbent: [ Bmim][BF 4 ]. The process parameters are as follows: the toluene absorption tower is fed at 35 ℃ and 1bar, the theoretical plate number is 19, the operation pressure of the toluene desorption tower is 0.5bar, the desorption temperature is 155 ℃, the temperature is reduced by 50% compared with comparative example 1, the theoretical plate number of the toluene stripping tower is 7, and the blowing amount is 400kmol/h. The final purge gas flow was 14963m 3 And/h, the toluene content in the purified gas is 14.87mg/m 3 The yield of toluene products is 131.7kg/h, the mass fraction is 99.5%, the toluene removal rate is 99.85%, and the secondary purification of the stripping tower reduces the toluene content in the ionic liquid from 0.97% to 0.000023%. The process heat load was 7439kW, which is reduced by 80.7% compared to comparative example 1.
Example 2
The flow of exhaust gas is as follows in the process flow shown in figure 1: 19000m 3 And/h, toluene content in the waste gas: 8000mg/m 3 Toluene absorbent: [ Bmim][PF 6 ]. The process parameters are as follows: the toluene absorption tower is fed at 35 ℃ and 1bar, the theoretical plate number is 24, the operation pressure of the toluene desorption tower is 0.3bar, the desorption temperature is 145 ℃, the temperature is reduced by 53% compared with comparative example 2, the theoretical plate number of the toluene stripping tower is 5, and the blowing amount is 500kmol/h. The final purge gas flow was 18976m 3 And/h, the toluene content in the purified gas is 14.84mg/m 3 The yield of toluene products is 133.4kg/h, the mass fraction is 99.5%, the toluene removal rate is 99.81%, and the secondary purification of the stripping tower reduces the toluene content in the ionic liquid from 1.22% to 0.000064%. The heat load of the process was 4700kW, which was reduced by 83.6% compared to comparative example 2.
Example 3
The flow of exhaust gas is as follows in the process flow shown in figure 1: 14000m 3 And/h, toluene content in the waste gas: 12000mg/m 3 Toluene absorbent: [ Bmim][NTf 2 ]. The process parameters are as follows: the toluene absorption tower is fed at 35 ℃ and 1bar, the theoretical plate number is 28, the operation pressure of the toluene desorption tower is 0.2bar, the desorption temperature is 140 ℃, 55% lower than that of comparative example 3, the theoretical plate number of the toluene stripping tower is 4, and the blowing amount is 300kmol/h. Final purge gas flow of 13968m 3 And/h, the toluene content in the purified gas is 14.9mg/m 3 The yield of toluene products is 147.6kg/h, the mass fraction is 99.5%, the toluene removal rate is 99.87%, and the secondary purification of the stripping tower reduces the toluene content in the ionic liquid from 0.95% to 0.00035%. The heat load of the process is 2934kW, which is reduced by 85.4% compared with comparative example 3.
Comparative example 1
The flow of exhaust gas is as follows in the process flow shown in figure 2: 15000m 3 And/h, toluene content in the waste gas: 10000mg/m 3 Toluene absorbent: [ Bmim][BF 4 ]. The process parameters are as follows: the toluene absorption column is fed at 35 ℃,20bar, the theoretical plate number is 19, the operation pressure of the toluene desorption column is 0.5bar, and the desorption temperature is 310 ℃. The final purge gas flow was 14963m 3 And/h, the toluene content in the purified gas is 14.85mg/m 3 The yield of toluene products is 131.7kg/h, the mass fraction is 99.5%, the toluene removal rate is 99.85%, the toluene content in the ionic liquid is 0.011% by the purification of a toluene desorber, and the heat load of the process is 38602kW.
Comparative example 2
The flow of exhaust gas is as follows in the process flow shown in figure 2: 19000m 3 And/h, toluene content in the waste gas: 8000mg/m 3 Toluene absorbent: [ Bmim][PF 6 ]. The process parameters are as follows: the toluene absorption column is fed at 35 ℃,20bar, the theoretical plate number is 24, the operation pressure of the toluene desorption column is 0.3bar, and the desorption temperature is 310 ℃. The final purge gas flow was 18963m 3 And/h, the toluene content in the purified gas is 14.88mg/m 3 The yield of toluene products is 133.4kg/h, the mass fraction is 99.5%, the toluene removal rate is 99.81%, the toluene desorber is used for purifying so that the toluene content in the ionic liquid is 0.016%, and the heat load of the process is 28594kW.
Comparative example 3
The flow of exhaust gas is as follows in the process flow shown in figure 2: 14000m 3 And/h, toluene content in the waste gas: 12000mg/m 3 Toluene absorbent: [ Bmim][NTf 2 ]. The process parameters are as follows: the toluene absorption column is fed at 35 ℃,20bar, the theoretical plate number is 28, the operation pressure of the toluene desorption column is 0.2bar, and the desorption temperature is 310 ℃. Final purge gas flow of 13959m 3 And/h, the toluene content in the purified gas is 14.74mg/m 3 The yield of toluene products is 147.6kg/h, the mass fraction is 99.5%, the toluene removal rate is 99.88%, the toluene content in the ionic liquid is 0.013% by the purification of a toluene desorber, and the heat load of the process is 20055kW.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, or alternatives falling within the spirit and principles of the invention.
Claims (8)
1. An ionic liquid for efficiently absorbing toluene exhaust gas at normal pressure, comprising:
[Bmim][PF 6 ]、[Bmim][BF 4 ]、[Bmim][NTf 2 ]any one of them.
2. A method for efficiently absorbing toluene exhaust gas at normal pressure, comprising:
an atmospheric absorption treatment of toluene using the ionic liquid according to claim 1 as a toluene absorber.
3. The method according to claim 2, comprising:
(1) Toluene waste gas enters a toluene absorption tower from the tower bottom, ionic liquid is fed from the tower top of the absorption tower, the toluene waste gas and the ionic liquid are in countercurrent contact in the absorption tower, and after the toluene waste gas is absorbed by the ionic liquid, the toluene content in the tower top purified gas is less than or equal to 15mg/m 3 The ionic liquid absorption liquid containing high-concentration toluene flows out from the bottom of the absorption tower;
(2) The ionic liquid absorption liquid containing high-concentration toluene obtained in the step (1) is heated by a heat exchanger and enters a toluene desorption tower for flash separation, a toluene crude product is extracted from the top of the desorption tower, and the ionic liquid regenerated for the first time flows out from the bottom of the desorption tower;
(3) Pressurizing the toluene crude product obtained in the step (2) through a compressor, condensing and cooling through a heat exchanger, then entering a flash tank for flash evaporation and purification, obtaining a toluene product with the mass purity of 99.5% at the bottom of the flash tank, refluxing the rest of non-condensable gas from the top of the flash tank, mixing with toluene waste gas, and then entering a toluene absorption tower for re-absorption;
(4) The ionic liquid regenerated for the first time in the step (2) is purified for the second time through a toluene stripping tower, so that the toluene content in the ionic liquid is reduced to below 0.0004 percent from 0.9 to 1.5 percent, the ionic liquid regenerated for the first time is pressurized to 1bar through a centrifugal pump, and then enters the toluene stripping tower from a feeding hole at the top of the tower and flows from top to bottom; the purified gas discharged from the top of the tower in the step (1) is shunted by a shunt to obtain blowing and degassing, the blowing and degassing enters from the bottom of the blowing and degassing tower, and the blowing and degassing contacts with the ionic liquid in the blowing and degassing tower in a countercurrent way from bottom to top, the toluene waste gas obtained from the top of the blowing and degassing tower flows back, is mixed with the toluene waste gas and then enters a toluene absorption tower to be absorbed again, and the secondarily purified ionic liquid flows back to the ionic liquid feeding port of the absorption tower for recycling.
4. A method according to claim 3, wherein:
the theoretical plate number of the toluene absorption tower in the step (1) is 10-30 plates, the operating pressure is 1bar, and the feeding temperature is 35 ℃.
5. A method according to claim 3, wherein:
the temperature of the heat exchanger in the step (2) is 120-169 ℃, and the operating pressure of the toluene desorption tower is 0.1-0.5 bar.
6. A method according to claim 3, wherein:
and (3) condensing and cooling the heat exchanger to 35 ℃.
7. A method according to claim 3, wherein:
the outlet pressure of the compressor in the step (3) is 1-9 bar.
8. A method according to claim 3, wherein:
the theoretical plate number of the toluene stripping tower in the step (4) is 3-10 plates, the operating pressure is 1bar, and the feeding temperature is 120-169 ℃.
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Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
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