CN108159842B - Method for reducing VOC content in tail gas generated by methane chloride device - Google Patents
Method for reducing VOC content in tail gas generated by methane chloride device Download PDFInfo
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- CN108159842B CN108159842B CN201711402266.9A CN201711402266A CN108159842B CN 108159842 B CN108159842 B CN 108159842B CN 201711402266 A CN201711402266 A CN 201711402266A CN 108159842 B CN108159842 B CN 108159842B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1487—Removing organic compounds
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/14—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by absorption
- B01D53/1425—Regeneration of liquid absorbents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2252/00—Absorbents, i.e. solvents and liquid materials for gas absorption
- B01D2252/20—Organic absorbents
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2257/00—Components to be removed
- B01D2257/70—Organic compounds not provided for in groups B01D2257/00 - B01D2257/602
- B01D2257/708—Volatile organic compounds V.O.C.'s
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
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- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
Abstract
The invention provides a method for reducing VOC content in tail gas generated by a methane chloride device, which comprises the following steps: introducing tail gas generated by a methane chloride device from the middle lower part of the spray absorption tower, spraying an absorbent from the top of the spray absorption tower, and absorbing VOC (volatile organic compounds) except hydrogen chloride in the tail gas; the obtained unabsorbed tail gas enters a tail gas buffer tank from the top of the spray absorption tower; the obtained rich absorbent solution enters an analytic tower from the top of the analytic tower after heat exchange, and VOC in the rich absorbent solution is analyzed; the analyzed VOC overflows from the top of the analysis tower and enters an organic matter buffer tank for recycling; the absorbent barren solution obtained after the desorption is discharged from the bottom of the desorption tower by utilizing the pressure difference, and enters the top of the spray absorption tower for recycling through condensation. The method effectively reduces the content of VOC in the tail gas of the methane chloride device, simultaneously realizes the recycling of materials in the tail gas, and ensures the maximum benefit of the operation of the device.
Description
Technical Field
The invention relates to a method for treating tail gas, in particular to a method for reducing the content of VOC (volatile organic compounds) in the tail gas generated by a methane chloride device, and belongs to the technical field of environmental chemical industry.
Background
In recent years, the situation of air pollution in China is getting more severe, and the emission of Volatile Organic Compounds (VOC) seriously affects the quality of environmental air. The world health organization defines VOCs as: the compound with the boiling point of 50-250 ℃ has the saturated vapor pressure of over 133.32Pa at room temperature, and is an organic matter existing in the air in the form of steam at room temperature.
At present, a large amount of tail gas is generated in the production process of methane chloride, and the main components of the tail gas comprise hydrogen chloride and organic substances such as methyl chloride, dichloromethane, chloroform, carbon tetrachloride and the like. Most enterprises adopt simple water absorption or alkali absorption treatment process, the treatment effeciency is low, still can produce the higher spent acid of VOC content or the high salt waste water that contains simultaneously, leads to the reduction of follow-up system throughput, has aggravated the environmental protection pressure and the treatment cost of enterprise greatly to need collect the tail gas that each equipment discharged in the device, concentrate purification recovery processing.
The method for reducing the VOC content in the tail gas in the prior art mainly comprises the following steps: condensation, absorption, adsorption, direct combustion, catalytic oxidation, biological purification, and the like. Wherein, the condensation method, the absorption method and the adsorption method can not only treat the pollution caused by the tail gas, but also realize the recycling of resources. Chinese patent document CN 203816452U discloses a system for treating byproduct tail gas from the production of methyl chloride, which comprises a feed heat exchanger and a purification tower, wherein a cooling device is arranged at the top of the purification tower; pre-cooling the byproduct tail gas generated in the production of methyl chloride by a feeding heat exchanger, then, condensing the tail gas in a purification tower, extracting hydrogen chloride gas from the top of the purification tower, and discharging chlorine-containing components except the hydrogen chloride after condensation along with the kettle liquid; the utility model adopts the condensation mode to separate the reaction tail gas mixture, and can directly obtain the hydrogen chloride gas, but the patent does not mention a device for further treating the chloromethane by-product tail gas, and the device is only used for the tail gas containing chlorine components and hydrogen chloride, and the problem that the chlorine components are mixed into the hydrogen chloride due to insufficient condensation also exists; chinese patent document CN201551948U discloses a methane chloride generation tail gas absorption device, which comprises a falling film absorption tank, wherein the falling film absorption tank is connected with a methane chloride generation tower through a first pipeline, an absorption liquid pipe and a first liquid outlet pipe are installed on the falling film absorption tank, the falling film absorption tank is communicated with a tail gas absorption tower through a second pipeline, a spray pipe is installed on the upper part of the tail gas absorption tower, the spray pipe is communicated with a water source through a water pipe, and a second liquid outlet pipe is installed on the lower part of the tail gas absorption tower; the utility model discloses an adopt the two-stage to absorb, although can fully absorb the chloride in the tail gas, this utility model absorption liquid is two kinds, and the volume is big, and the recovery is recycled comparatively loaded down with trivial details to mention in this patent and utilize 22% hydrochloric acid and water to absorb byproduct tail gas, can realize containing hydrochloric acid and chlorine-containing organic matter in the absorption liquid that the absorption obtained, lead to separating difficulty, absorption liquid utilization ratio low, do not relate to the recycling of absorption liquid in addition yet.
The biological purification method needs continuous and stable airflow, has poor operation stability, and produces tail gas with discontinuity and uncontrollable property; in addition, the stability of the biological purification system is affected during the shutdown of the device, and the operation of the biological purification system requires huge operation cost and management cost. The catalytic oxidation method can realize the effective utilization of methyl chloride in the tail gas, but the tail gas contains other impurity gases, which can cause certain damage to the catalyst, reduce the service life of the catalyst and improve the operation cost of the whole device.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a method for reducing the content of VOC in tail gas generated by a methane chloride device; according to the invention, the VOC content in the tail gas is effectively reduced by using a solvent absorption method on the basis of the existing device, the operation cost of the device can be reduced to the maximum extent, the treatment requirement can be met, the absorbent can be recycled, and the separated HCl, chloromethane and the like can be recycled; the method is green, economic and environment-friendly, and realizes the reutilization of waste resources.
The technical scheme of the invention is as follows:
a method of reducing the VOC content of tail gas from a methane chloride plant comprising the steps of:
(1) introducing tail gas generated by a methane chloride device from the middle lower part of a spray absorption tower, spraying an absorbent from the top of the spray absorption tower, and absorbing VOC (volatile organic compounds) except hydrogen chloride in the tail gas to obtain unabsorbed tail gas and absorbent rich liquid at the bottom of the spray absorption tower;
(2) the unabsorbed tail gas in the step (1) enters a tail gas buffer tank from the top of the spray absorption tower; the absorbent rich solution at the bottom of the spraying absorption tower in the step (1) enters an analysis tower from the top of the analysis tower after heat exchange, and VOC in the absorbent rich solution is analyzed to obtain VOC and absorbent barren solution;
(3) the VOC analyzed in the step (2) overflows from the top of the analysis tower and enters an organic matter buffer tank for recycling; and (3) discharging the absorbent barren solution obtained in the step (2) from the bottom of the desorption tower by utilizing the pressure difference between the desorption tower and the spray absorption tower, and allowing the absorbent barren solution to enter the spray absorption tower from the top of the spray absorption tower for continuous spraying after condensation for recycling.
Preferably according to the invention, the off-gas produced by the methane chloride plant in step (1) consists essentially of: 20-60 wt% of hydrogen chloride, 40-80 wt% of chloromethane, 0.5-10 wt% of dichloromethane, 0-5 wt% of chloroform and 0-2 wt% of carbon tetrachloride.
According to the invention, the spray absorption tower in the step (1) is preferably a packed tower, the height of the tower is controlled to be 15-25 m, and the packing material is one of carbon steel, 304 metal wire mesh, PTFE, impregnated graphite or MONEL.
According to the invention, the absorbent in the step (1) is preferably one or a combination of more than two of diesel oil, carbon tetrachloride, silicon tetrachloride, toluene, cyclohexane, methyl ethyl ketone, cyclohexanone, DMF, a surfactant or dichloroethane.
According to the invention, the spraying temperature of the absorbent in the step (1) is preferably-10 to 30 ℃, the tower pressure of a spraying absorption tower is controlled to be 0 to 50kPa, and the spraying rate is controlled to be 10 to 20m3/h。
Preferably, in step (1), the introduction rate of the tail gas into the spray absorption tower is 140-175Nm3/h。
According to the invention, in the step (1), when the mass concentration of the absorbent in the absorbent rich solution at the bottom of the spraying absorption tower is more than or equal to 80%, the absorbent is continuously recycled for spraying the tail gas; and (3) when the mass concentration of the absorbent in the absorbent rich solution at the bottom of the spray absorption tower in the step (1) is less than 80%, carrying out the treatment of the step (2) on the absorbent rich solution.
Preferably, in step (1), the unabsorbed tail gas mainly comprises hydrogen chloride, and the mass content of hydrogen chloride in the unabsorbed tail gas is 86% or more.
Preferably, in the step (2), the hydrogen chloride in the tail gas buffer tank is absorbed by water to prepare hydrochloric acid or is directly used for hydrochlorination, and the absorption temperature is 20-30 ℃. The hydrochlorination mainly utilizes methanol to react with hydrogen chloride to prepare methyl chloride, and the normal operation of the reaction can not be influenced by a small amount of methyl chloride contained in the raw material hydrogen chloride.
Preferably, in the step (2), the temperature of the rich absorbent solution is increased to 40-50 ℃ after heat exchange.
Preferably, the desorption tower in the step (2) is a packed tower, the height of the tower is controlled to be 10-30 m, and the packing material is one of carbon steel, 304 metal wire mesh, PTFE, impregnated graphite or MONEL; the analysis temperature at the bottom of the tower is 120-190 ℃, the temperature at the top of the tower is 15-40 ℃, and the pressure of the tower is controlled at 0.2-0.5 MPa.
Preferably, in step (3), the gas overflowing from the top of the desorption tower mainly comprises the following components: 80-95 wt% of chloromethane, 2-12 wt% of dichloromethane, 0.5-6 wt% of chloroform and 0-1 wt% of carbon tetrachloride.
Preferably, according to the present invention, the VOC gas in the organic matter buffer tank of step (3) can be introduced into a thermal chlorination system for use. The VOC in the organic matter buffer tank is mainly methyl chloride and also contains a small amount of dichloromethane, chloroform and carbon tetrachloride, and the thermal chlorination system is mainly used for preparing dichloromethane and chloroform by reacting methyl chloride with chlorine and can further recycle the methyl chloride in tail gas.
According to the present invention, it is preferable that the concentration of the absorbent in the absorbent lean solution in the step (3) is 98 wt% or more.
According to the invention, the condensation in the step (3) is preferably three-stage condensation, and the three-stage condensation is carried out by respectively condensing the absorbent rich solution with the temperature of-10-30 ℃, the circulating water with the temperature of 15-30 ℃ and the dichloromethane with the temperature of-20-10 ℃.
The equipment used in the invention can be conventional equipment in the field, the tail gas generated by the methane chloride device is the tail gas generated in the production process of methane chloride, and the method of the invention is a conventional method unless specially stated.
The invention has the technical characteristics and beneficial effects that:
1. the absorbent selected by the invention can effectively absorb organic chloride in the tail gas without basically absorbing hydrogen chloride, and can resolve the organic matters in the absorbent by changing the temperature, and the resolution rate can reach more than 95%; the temperature is controlled to be-10-30 ℃ in the tail gas absorption process, the air pressure is controlled to be 0-0.05 MPa, the absorption condition is mild, the tail gas absorption process can be realized by conventional equipment, and the operation is simple; the absorbed tail gas is mainly hydrogen chloride, and can be used for preparing hydrochloric acid by water absorption or for hydrochlorination, so that the hydrogen chloride is recycled, and the VOC content in the tail gas is obviously reduced; organic matters such as the resolved chloromethane and dichloromethane can be recycled after water/alkali washing treatment or returned to a thermal chlorination system for use, so that the recycling of materials is realized; the analyzed absorbent realizes the recycling by utilizing the pressure difference between the two towers, reduces the use of a circulating pump and saves the cost; the discharge of the absorption tower kettle is absorbent rich liquid at the temperature of-10-30 ℃, the discharge of the desorption tower kettle is absorbent lean liquid at the temperature of 120-180 ℃, the absorbent rich liquid is used for condensing the absorbent lean liquid, the heat exchange of two materials can be realized, the high-level heat energy of the absorbent lean liquid is fully utilized, the energy consumption is reduced, the consumption of circulating water or low-temperature dichloromethane required by cooling the absorbent lean liquid is reduced, namely, the load of a condenser is reduced, a reboiler at the tower bottom is required for heating the absorbent rich liquid after the absorbent rich liquid enters the desorption tower, the consumption of steam in the reboiler can be reduced after the absorbent rich liquid exchanges heat with the absorbent lean liquid, and the cost is saved.
2. When the mass concentration of the absorbent in the absorbent rich solution at the bottom of the spray absorption tower is more than or equal to 80%, the absorbent rich solution is continuously recycled for spraying the tail gas, so that the steps are simplified, and the cost is saved; when the mass concentration of the absorbent in the absorbent rich solution is less than 80%, the absorbent rich solution is analyzed, so that the analysis times can be reduced, the cost is saved, and more VOC gas obtained by single analysis is simple and efficient.
3. The method can reduce the content of VOC in the tail gas on the basis of the existing device, can reduce the operation cost of the device to the maximum extent and meet the treatment requirement, simultaneously, the VOC gases such as hydrogen chloride, methyl chloride and the like obtained by separation can be recycled, the used absorbent can be recycled, the whole method is convenient to operate, stable to operate, economic and environment-friendly, and the reutilization of waste resources is realized to the maximum extent.
4. The three-stage condensation is to cool the absorbent barren solution from the desorption tower by using the absorbent rich solution, the circulating water and the low-temperature dichloromethane respectively, so that the temperature of the absorbent barren solution is reduced from 120-180 ℃ to-10-30 ℃, the requirements of process conditions are met, and meanwhile, the circulating water and the absorbent rich solution are used for two-stage condensation, so that the energy consumption is saved, and the production cost is reduced.
Drawings
FIG. 1 is a schematic diagram of the process for reducing the VOC content of the tail gas from a methane chloride plant according to the present invention.
Detailed Description
The invention is further described below with reference to process flow diagrams and examples.
Meanwhile, the experimental methods described in the following examples are all conventional methods unless otherwise specified; the reagents, equipment and materials, unless otherwise indicated, are well known in the art and are commercially available.
In the embodiment, the spray absorption tower is a packed tower, the height of the tower is 18m, and the packing material is PTFE; the desorption tower is a packed tower, the height of the tower is 28m, and the packing material is 304 wire mesh.
Example 1
In this embodiment, the composition of the tail gas generated by the methane chloride plant is: 23.2 wt% of hydrogen chloride, 72 wt% of chloromethane, 3.8 wt% of dichloromethane, 0.8 wt% of chloroform and 0.2 wt% of carbon tetrachloride.
A method of reducing the VOC content of the tail gas from a methane chloride plant, as shown in figure 1, comprising the steps of:
tail gas containing chloromethane, dichloromethane, chloroform, carbon tetrachloride, hydrogen chloride, etc. in 150 Nm/min from the middle lower part of the spray absorption tower3The flow rate of the gas is introduced at a speed of-2 to 0 ℃ for 15m, and the absorbent is carbon tetrachloride3Spraying at a speed of/h from the top of the spraying absorption tower to absorb VOC organic matters except hydrogen chloride in tail gas, and controlling the pressure of the spraying absorption tower to be 30 KPa; unabsorbed hydrogen chloride enters the tail gas buffer tank from the top of the spray absorption tower, and is absorbed by water (the absorption temperature is 25-30 ℃) to prepare hydrochloric acid or is directly used for hydrochlorination; the bottom of the spray absorption tower is connected with a circulating pump, the content of carbon tetrachloride in the absorbent rich liquid after tail gas absorption is 85.6 wt%, the absorbent rich liquid is heated to 40-50 ℃ by a circulating condenser 2 and enters an analysis tower from the upper part, the temperature of the bottom of the analysis tower is controlled at 132 ℃ by a reboiler at the bottom of the analysis tower, the pressure of a kettle of the analysis tower is controlled at 0.3MPa, the temperature of the top of the tower is controlled at 20-25 ℃, the pressure of the top of the tower is controlled at 0.28MPa, and the analyzed light-component VOC organic matter enters an organic matter buffer tank from the top of the tower and is supplied for thermal chlorination; the obtained absorbent barren solution is subjected to three-stage condensation (condensers 2, 3 and 4 are respectively absorbent passing through the temperature of-10-30 ℃) from the bottom of the desorption tower by utilizing the pressure difference of the two towersRich solution, circulating water with the temperature of 15-30 ℃ and dichloromethane with the temperature of-20 to-10 ℃ are condensed) and then enter from the top of the spray absorption tower to be mixed with the absorbent circulating in the spray absorption tower for spraying, so that the recycling of the absorbent is realized.
Through detection, the main components in the tail gas overflowing from the top of the spray absorption tower comprise 98.55 wt% of hydrogen chloride, 0.51 wt% of methyl chloride, 0.38 wt% of dichloromethane, 0.21 wt% of chloroform and 0.34 wt% of carbon tetrachloride; the contents of main components discharged from the top of the desorption tower comprise 94.05 wt% of chloromethane, 4.85 wt% of dichloromethane, 0.98 wt% of chloroform and 0.12 wt% of carbon tetrachloride; the content of carbon tetrachloride in the desorbed absorbent barren solution can reach 98.5 wt%.
Example 2
In this embodiment, the components of the tail gas generated by the methane chloride device are 45 wt% of hydrogen chloride, 48.5 wt% of methyl chloride, 4.8 wt% of dichloromethane, 1.2 wt% of chloroform, 0.48 wt% of carbon tetrachloride and 0.02 wt% of others.
A method of reducing the VOC content of the tail gas from a methane chloride plant as described in example 1, except that:
cyclohexane is used as absorbent, the spraying temperature is controlled between-5 ℃ and-3 ℃, and the speed of introducing tail gas into a spraying absorption tower is 175Nm3And h, controlling the cyclohexane content in the absorbent rich solution after tail gas absorption to be 89.5 wt%, controlling the bottom temperature of the desorption tower to be 136 ℃, controlling the kettle pressure of the desorption tower to be 0.32MPa, controlling the top temperature of the desorption tower to be 18-22 ℃, and controlling the top pressure of the desorption tower to be 0.3 MPa.
Through detection, the content of the components in the tail gas overflowing from the top of the spray absorption tower is 96.35 wt% of hydrogen chloride, 1.46 wt% of methyl chloride, 1.33 wt% of dichloromethane, 0.71 wt% of chloroform, 0.13 wt% of carbon tetrachloride and 0.02 wt% of the rest; the contents of the components discharged from the top of the desorption tower were 89.72 wt% of methyl chloride, 7.84 wt% of methylene chloride, 1.63 wt% of chloroform, 0.79 wt% of carbon tetrachloride and 0.02 wt% of the others. The cyclohexane content in the absorption agent barren solution after the desorption can reach 98.8 wt%.
Example 3
In this example, the composition of the tail gas generated by the methane chloride device was 38.4 wt% of hydrogen chloride, 57.1 wt% of methyl chloride, 3.2 wt% of methylene chloride, 1.15 wt% of chloroform, and 0.15 wt% of the others.
A method of reducing the VOC content of the tail gas from a methane chloride plant as described in example 1, except that:
cyclohexanone is used as an absorbent, the spraying temperature is controlled to be 0-2 ℃, and the speed of introducing tail gas into a spraying absorption tower is 162Nm3And h, the content of cyclohexanone in the absorbent rich solution after tail gas absorption is 87.5 wt%, the bottom temperature of the desorption tower is controlled to be 182 ℃, the bottom pressure of the desorption tower is controlled to be 0.22MPa, the top temperature of the desorption tower is controlled to be 27-30 ℃, and the top pressure of the desorption tower is 0.20 MPa.
Through detection, the content of the components in the tail gas overflowing from the top of the spray absorption tower is 96.77 wt% of hydrogen chloride, 1.64 wt% of methyl chloride, 1.06 wt% of dichloromethane, 0.40 wt% of chloroform and 0.13 wt% of the rest; the contents of the components discharged from the top of the desorption tower were 93.58 wt% of methyl chloride, 4.61 wt% of methylene chloride, 1.64 wt% of chloroform and 0.17 wt% of the others. The cyclohexane content in the absorption agent barren solution after the desorption can reach 98.8 wt%.
Example 4
In this example, the composition of the tail gas is 12 wt% of hydrogen chloride, 78.5 wt% of methyl chloride, 6.8 wt% of methylene chloride, 2.5 wt% of chloroform, 0.06 wt% of carbon tetrachloride and 0.14 wt% of others.
A method of reducing the VOC content of the tail gas from a methane chloride plant as described in example 1, except that:
toluene is used as absorbent, the spraying temperature is controlled between-3 ℃ and-1 ℃, and the speed of introducing tail gas into a spraying absorption tower is 140Nm3And h, the toluene content in the absorbent rich solution after tail gas absorption is 86.3 wt%, the bottom temperature of the desorption tower is controlled at 162 ℃, the kettle pressure of the desorption tower is controlled at 0.29MPa, the top temperature of the desorption tower is controlled at 26-30 ℃, and the top pressure of the desorption tower is controlled at 0.27 MPa.
Through detection, the content of the components in the tail gas overflowing from the top of the spray absorption tower is 86.05 wt% of hydrogen chloride, 8.63 wt% of methyl chloride, 3.24 wt% of dichloromethane, 1.51 wt% of chloroform, 0.14 wt% of carbon tetrachloride and 0.43 wt% of the rest; the contents of the components discharged from the top of the desorption tower are 89.82 wt% of chloromethane, 7.38 wt% of dichloromethane, 2.66 wt% of chloroform, 0.05 wt% of carbon tetrachloride and 0.09 wt% of the rest. The cyclohexane content in the absorption agent barren solution after the desorption can reach 98.2 wt%.
Example 5
In this example, the composition of the tail gas generated by the methane chloride plant was 32.5 wt% of hydrogen chloride, 53.7 wt% of methyl chloride, 7.6 wt% of methylene chloride, 4.2 wt% of chloroform, 0.8 wt% of carbon tetrachloride, and 1.2 wt% of the others.
A method of reducing the VOC content of the tail gas from a methane chloride plant as described in example 1, except that:
the spraying temperature is controlled to be-2-1 ℃, and the rate of introducing the tail gas into the spraying absorption tower is 155Nm3H, the content of carbon tetrachloride in the absorbent rich solution after tail gas absorption is 86.0 wt%, the bottom temperature of the desorption tower is controlled at 135 ℃, the bottom pressure of the desorption tower is controlled at 0.32MPa, the top temperature of the desorption tower is controlled at 19-24 ℃, and the top pressure of the desorption tower is controlled at 0.31 MPa.
Through detection, the components in the tail gas overflowing from the top of the spray absorption tower comprise 96.83 wt% of hydrogen chloride, 0.54 wt% of methyl chloride, 0.18 wt% of dichloromethane, 0.15 wt% of chloroform, 0.36 wt% of carbon tetrachloride and the other 1.94 wt%; the contents of all components discharged from the top of the desorption tower are 81.83 wt% of methyl chloride, 11.43 wt% of dichloromethane, 5.59 wt% of chloroform, 0.32 wt% of carbon tetrachloride and 0.83 wt% of others; the content of carbon tetrachloride in the desorbed absorbent barren solution can reach 98.7 wt%.
Claims (6)
1. A method of reducing the VOC content of tail gas from a methane chloride plant comprising the steps of:
(1) introducing tail gas generated by a methane chloride device from the middle lower part of a spray absorption tower, spraying an absorbent from the top of the spray absorption tower, and absorbing VOC (volatile organic compounds) except hydrogen chloride in the tail gas to obtain unabsorbed tail gas and absorbent rich liquid at the bottom of the spray absorption tower; the absorbent is one or the combination of more than two of diesel oil, carbon tetrachloride, silicon tetrachloride, toluene, cyclohexane, methyl ethyl ketone, cyclohexanone, DMF, surfactant or dichloroethane; the spraying temperature of the absorbent is-10-30 ℃, the tower pressure of the spraying absorption tower is controlled to be 0-50 kPa, and the spraying rate is controlled to be 10-20 m3H; the introduction rate of the tail gas into the spray absorption tower is 140-175Nm3H; when the mass concentration of the absorbent in the absorbent rich solution at the bottom of the spraying absorption tower is more than or equal to 80 percent, the absorbent is continuously recycled for spraying the tail gas; when the mass concentration of the absorbent in the absorbent rich solution at the bottom of the spraying absorption tower is less than 80%, carrying out the treatment of the step (2) on the absorbent rich solution;
(2) the unabsorbed tail gas in the step (1) enters a tail gas buffer tank from the top of the spray absorption tower; the absorbent rich solution at the bottom of the spraying absorption tower in the step (1) enters an analysis tower from the top of the analysis tower after heat exchange, and VOC in the absorbent rich solution is analyzed to obtain VOC and absorbent barren solution; the temperature of the rich absorbent solution is raised to 40-50 ℃ after heat exchange; the resolving temperature at the bottom of the tower is 120-190 ℃, the temperature at the top of the tower is 15-40 ℃, and the pressure of the tower is controlled at 0.2-0.5 MPa;
(3) the VOC analyzed in the step (2) overflows from the top of the analysis tower and enters an organic matter buffer tank for recycling; discharging the absorbent barren solution obtained in the step (2) from the bottom of the desorption tower by utilizing the pressure difference between the desorption tower and the spray absorption tower, and allowing the absorbent barren solution to enter the spray absorption tower from the top of the spray absorption tower for continuous spraying after condensation for recycling; the condensation is three-stage condensation, and the three-stage condensation is respectively carried out by absorbent rich liquor with the temperature of-10-30 ℃, circulating water with the temperature of 15-30 ℃ and dichloromethane with the temperature of-20-10 ℃.
2. The method for reducing the content of VOC in the tail gas generated by the methane chloride device according to claim 1, wherein the spray absorption tower in the step (1) is a packed tower, the height of the tower is controlled to be 15-25 m, and the packing material is one of carbon steel, 304 wire mesh, PTFE, impregnated graphite or MONEL.
3. The method for reducing the VOC content in the tail gas generated by the methane chloride device according to the claim 1, wherein in the step (1), the unabsorbed tail gas mainly comprises hydrogen chloride, and the mass content of the hydrogen chloride in the unabsorbed tail gas is greater than or equal to 86%.
4. The method for reducing the content of VOC in the tail gas generated by the methane chloride device according to claim 1, wherein in the step (2), the hydrogen chloride in the tail gas buffer tank is absorbed by water to prepare hydrochloric acid or is directly used for hydrochlorination reaction, and the absorption temperature is 20-30 ℃.
5. The method for reducing the content of VOC in the tail gas generated by the methane chloride device according to claim 1, wherein the desorption tower in the step (2) is a packed tower, the height of the tower is controlled to be 10-30 m, and the packing material is one of carbon steel, 304 wire mesh, PTFE, impregnated graphite or MONEL.
6. The method for reducing the content of VOC in the tail gas generated by the methane chloride device according to the claim 1, characterized in that the VOC gas in the organic matter buffer tank in the step (3) can be introduced into a thermal chlorination system for use.
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| CN201711402266.9A CN108159842B (en) | 2017-12-22 | 2017-12-22 | Method for reducing VOC content in tail gas generated by methane chloride device |
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| CN109847538A (en) * | 2019-01-24 | 2019-06-07 | 上海泓济环保科技股份有限公司 | Methylene chloride waste gas processing method |
| CN111965263B (en) * | 2020-08-14 | 2022-05-13 | 西安圆方环境卫生检测技术有限公司 | Portable organic volatile matter short-term test appearance |
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| CN114425223A (en) * | 2020-10-15 | 2022-05-03 | 中国石油化工股份有限公司 | Tetrahydrofuran tail gas recovery system, method and application |
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