CN215196194U - Purification device for caprolactam procedure volatile organic compounds waste gas - Google Patents
Purification device for caprolactam procedure volatile organic compounds waste gas Download PDFInfo
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- CN215196194U CN215196194U CN202120591518.2U CN202120591518U CN215196194U CN 215196194 U CN215196194 U CN 215196194U CN 202120591518 U CN202120591518 U CN 202120591518U CN 215196194 U CN215196194 U CN 215196194U
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Abstract
The invention discloses a purification device for volatile organic compounds waste gas in a caprolactam working procedure, which comprises a volatile organic compound storage tank, wherein the top of the volatile organic compound storage tank is provided with a gas phase outlet, and the gas phase outlet is connected to a gas phase inlet of a washing tower through a waste gas pipeline; the upper part of the washing tower is provided with an absorption liquid inlet, the top of the washing tower is provided with a tail gas outlet, and the bottom of the washing tower is provided with an absorption liquid outlet; the amide oil pipeline is connected to the absorption liquid input port, the tail gas outlet is provided with a tail gas pipeline and a fan, the absorption liquid outlet at the bottom of the washing tower is provided with an absorption liquid conveying pump inlet pipeline which is connected to an absorption liquid conveying pump, and the absorption liquid conveying pump is connected to the upper part of the washing tower through an absorption liquid backflow pipeline for backflow; the absorption liquid conveying pump is also connected to the extraction tower through an absorption liquid extraction pipeline. Adopt the device, can retrieve the unorganized waste gas that discharges that volatile organic compounds storage tank produced, can not only solve the environmental protection problem, can also produce economic benefits.
Description
Technical Field
The invention belongs to the field of chemical industry, and relates to a purification device for volatile organic compounds waste gas in a caprolactam working procedure.
Background
Currently, caprolactam refining processes include an extraction step that uses benzene as a solvent for extraction. The extraction system comprises a hexane extraction tank, a back extraction tank, a benzene storage tank, a benzene hexane storage tank, benzene refining and benzene stripping, and benzene is used as a solvent to be recycled in the system.
In the operation process of the system, nitrogen seal single-breathing valves are arranged in a hexane extraction tank, a back extraction tank, a benzene storage tank and a benzene hexane storage tank, but the benzene-containing waste gas is still exhaled from the single-breathing valves; the freezing water heat exchanger is arranged at the exhaust point for benzene refining and benzene stripping, so that the partial pressure of benzene vapor is reduced, and the emission of the benzene vapor is reduced. However, the problems of large benzene consumption and peculiar smell on site cannot be solved completely.
In the caprolactam industry, the processes are mostly adopted in the devices before 2019, and the consumption of benzene is about 5kg/t of caprolactam. New devices are newly built after 2019, most of the new devices use a fan to intensively pressurize the benzene-containing waste gas and then condense the benzene-containing waste gas to recover liquid benzene, and the tail gas which cannot be condensed is incinerated. In addition, the technology of VOC treatment by membrane absorption is available, but the recovery rate is not too high due to the inexhaustibility, and a great safety risk exists.
Disclosure of Invention
The invention provides a purification device for volatile organic compound waste gas in a caprolactam working procedure, which is used for recovering inorganically discharged waste gas generated by a volatile organic compound storage tank, not only can solve the problem of environmental protection, but also can generate economic benefit.
The invention has the technical scheme that the device for purifying the volatile organic compound waste gas in the caprolactam working procedure comprises a volatile organic compound storage tank, wherein the top of the volatile organic compound storage tank is provided with a gas phase outlet, and the gas phase outlet is connected to a gas phase inlet of a washing tower through a waste gas pipeline; the upper part of the washing tower is provided with an absorption liquid inlet, the top of the washing tower is provided with a tail gas outlet, and the bottom of the washing tower is provided with an absorption liquid outlet; the amide oil pipeline is connected to the absorption liquid input port, the tail gas outlet is provided with a tail gas pipeline and a fan, the absorption liquid outlet at the bottom of the washing tower is provided with an absorption liquid conveying pump inlet pipeline which is connected to an absorption liquid conveying pump, and the absorption liquid conveying pump is connected to the upper part of the washing tower through an absorption liquid backflow pipeline for backflow; the absorption liquid conveying pump is also connected to the extraction tower through an absorption liquid extraction pipeline.
Further, the gas phase outlet of the volatile organic compound storage tank is also connected with an emptying pipe, and a flame arrester and a single-breath valve are installed on the emptying pipe.
Further, a first nitrogen pipeline is arranged above the volatile organic compound storage tank.
Further, the middle part of the washing tower is also connected with a second nitrogen pipeline.
Furthermore, the volatile organic compound storage tanks are multiple and are operated in parallel.
Further, the washing tower is a packed tower or a sieve plate tower.
The invention has the following beneficial effects:
according to the invention, the amide oil in the caprolactam generation process is used as an absorption solution to wash and absorb the volatile organic waste gas, and after the absorption tail gas in the absorption solution reaches a certain concentration, the extraction process is introduced for extraction and separation, so that the benzene in the organic waste gas can be recycled, the environmental protection problem can be solved, and the economic benefit can be generated.
Drawings
Fig. 1 is a schematic structural diagram of the device provided by the present invention.
In the figure: 1-volatile organic compound storage tank; 2-flame arrestors; 3-single exhalation valve; 4-a washing column; 5-absorption liquid delivery pump; 6, a fan; 7-a first nitrogen gas line; 8-an emptying pipe; 9-an exhaust gas conduit; 10-an absorption liquid conveying pipeline; 11-the absorption liquid goes to an extraction pipeline; 12-an absorption liquid return line; 13-a first nitrogen line; 14-a wash column tail gas pipeline; 15-a fan outlet duct; 16-absorption liquid delivery pump inlet pipeline
Detailed Description
Embodiments of the present invention will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention.
A device for purifying volatile organic waste gas in a caprolactam working procedure is disclosed, wherein the waste gas is derived from benzene-containing waste gas generated in an extraction working procedure in a caprolactam refining process, and the main components of the waste gas are benzene steam and cyclohexane. The device comprises a volatile organic compound storage tank 1, wherein the top of the volatile organic compound storage tank is provided with a gas phase outlet, and the gas phase outlet is connected to a gas phase inlet of a washing tower 4 through a waste gas pipeline 9; the upper part of the washing tower is provided with an absorption liquid inlet, the top of the washing tower is provided with a tail gas outlet, and the bottom of the washing tower is provided with an absorption liquid outlet; the amide oil pipeline 10 is connected to an absorption liquid input port, a tail gas pipeline 14 and a fan 6 are installed at a tail gas outlet, an absorption liquid conveying pump inlet pipeline 16 is arranged at an absorption liquid outlet at the bottom of the washing tower and connected to an absorption liquid conveying pump 5, and the absorption liquid conveying pump 5 is connected to the upper part of the washing tower 4 through an absorption liquid backflow pipeline 12 to perform backflow; the absorption liquid transfer pump 5 is also connected to the extraction column through an absorption liquid-to-extraction pipe 11.
The absorption liquid of the washing tower is amide oil, which comes from an ammonium sulfate procedure in a caprolactam refining process, and the main component of the absorption liquid is a mixed solution consisting of caprolactam, water, ammonium sulfate and a small amount of organic matters. Specifically, the aqueous solution contains 65-75% of caprolactam by mass; the amide oil absorbs the benzene-containing waste gas and is collected at the bottom of the washing tower and then can be conveyed to an extraction process for extraction.
Preferably, the gas phase outlet of the volatile organic compound storage tank is also connected with a vent pipe 8, and a flame arrester 2 and a single-breath valve 3 are installed on the vent pipe. And after the waste gas generated by the volatile organic compound storage tank is conveyed to a washing tower through a pipeline for washing and purification, the waste gas is conveyed to incineration treatment by a tail gas pipeline and a fan. When the washing tower operates abnormally, the waste gas generated by the volatile organic compound storage tank can be directly discharged through the flame arrester and the single-breath valve, so that the operation safety of the storage tank is ensured.
Preferably, a first nitrogen pipeline 7 is also arranged above the volatile organic compound storage tank.
Preferably, a second nitrogen pipeline 13 is also connected to the middle part of the washing tower.
Preferably, the volatile organic compound storage tank is a plurality of volatile organic compound storage tanks, and the plurality of volatile organic compound storage tanks are operated in parallel.
Preferably, the washing column is a packed column or a sieve plate column. More preferably a packed column.
The volatile organic compound storage tank 1 is a normal pressure storage tank, and the pressure of the volatile organic compound storage tank is controlled jointly through a nitrogen pressure control loop PIC001 and an exhaust gas pressure control loop PIC 002. The normal control range of the pressure control points PI002 and PI003 is 0.5-4 kPa (G); when the pressure of the pressure control point PI003 exceeds 4kPa (G), a cut-off valve XV004 arranged on the emptying pipe 8 is opened; when the pressure of PI003 is less than or equal to 4kPa (G), a shut-off valve XV004 arranged on the emptying pipe is closed. The outlet of the absorption liquid delivery pump 5 is provided with two branches: when the amide oil conveyed from the ammonium sulfate process is normal, the amide oil is stably conveyed to the extraction tower through a control circuit formed by a flow meter FI009 and a regulating valve FV 010; when the ammonium sulfate procedure can not normally convey the amide oil, the FV010 is closed to stop conveying the amide oil to the extraction tower, and the absorption liquid is sent to the extraction pipeline to flow back to the washing tower 4, thereby ensuring the washing effect of the washing tower.
The fan 6 is provided with a frequency converter, a pressure control loop SIC004 is arranged between the frequency converter and the pressure at the top of the washing tower 4, and the pressure PI012 at the top of the washing tower is controlled to be stabilized at-1 kPa (G); the outlet air pressure is not more than 5kPa (G), so that accidents caused by the fact that the normal pressure storage tank exceeds the lower limit of the design pressure under abnormal conditions are prevented.
The device may also be provided with a safety instrumentation system for ensuring the safety of the device in case of an abnormal situation. The following logical relationships exist for the safety instrumented system: when the fan 6 is stopped, the XV005 is closed and the XV004 and XV011 are opened. The exhaust gas in the volatile organic compound storage tank can be discharged from the single-breather valve in time, so that overpressure is prevented; and secondly, replacing the washing tower by using nitrogen to prevent explosive mixtures from being formed in the washing tower.
Example 1:
after 500g of absorbent is taken and respectively added with pure benzene with different masses for dissolution, the VOC content above the solution is monitored, and the experimental results are shown in the following table 1:
table 1: surface VOC detection data in absorbent with different concentrations of benzene
In the above experiment, no delamination occurred, and when the benzene content was less than 3% wt, the VOC content above the solution was about 2 ppm. In general production, the benzene content is lower than 2 wt% and can meet the requirement.
Example 2:
a certain device 100 kt/year caprolactam device carries out VOC treatment, and the source of benzene-containing tail gas has: the benzene tank of the raw material tank area is emptied, the benzene pump tank is emptied, the top of the back extraction tower is emptied, the benzene distillation tail gas is emptied, the tail gas of the stripping system is emptied, and the tail gas enters the washing tower (4) in parallel.
The rated flow of a fan (6) at the top of the washing tower is 1000Nm3At normal operation frequency of 30Hz, the pressure PI012 of the washing tower (4) is controlled at-0.5 kPa, the liquid level LI008 of the washing tower (4) is controlled at 50% by LV007, and the absorbent outlet flow FI009 is controlled at 22m3H is used as the reference value. By continued monitoring, the following data are obtained in table 2 below:
table 2: comparison of VOC content in tail gas of absorption tower and benzene content in absorption liquid
As can be seen from Table 2, the higher the benzene content in the absorption liquid is, the higher the VOC content in the tail gas is, but after the scheme is modified, the benzene-containing tail gas of the caprolactam device of 100 kt/year can directly reach the emission standard.
Claims (6)
1. A purification device for caprolactam procedure volatile organic compounds waste gas is characterized by comprising a volatile organic compounds storage tank (1), wherein the top of the volatile organic compounds storage tank is provided with a gas phase outlet, and the gas phase outlet is connected to a gas phase inlet of a washing tower (4) through a waste gas pipeline (9); the upper part of the washing tower is provided with an absorption liquid inlet, the top of the washing tower is provided with a tail gas outlet, and the bottom of the washing tower is provided with an absorption liquid outlet; the amide oil pipeline (10) is connected to an absorption liquid input port, a tail gas pipeline (14) and a fan (6) are installed at a tail gas outlet, an absorption liquid inlet pipeline (16) of an absorption liquid conveying pump is arranged at an absorption liquid outlet at the bottom of the washing tower and connected to the absorption liquid conveying pump (5), and the absorption liquid conveying pump (5) is connected to the upper part of the washing tower (4) through an absorption liquid backflow pipeline (12) to perform backflow; the absorption liquid conveying pump (5) is also connected to the extraction tower through an absorption liquid extraction pipeline (11).
2. The purification apparatus according to claim 1, wherein: the gas phase outlet of the volatile organic compound storage tank is also connected with an emptying pipe (8), and the emptying pipe is provided with a flame arrester (2) and a single exhalation valve (3).
3. The purification apparatus according to claim 1, wherein: a first nitrogen pipeline (7) is also arranged above the volatile organic compound storage tank.
4. The purification apparatus according to claim 1, wherein: the middle part of the washing tower is also connected with a second nitrogen pipeline (13).
5. The purification apparatus according to claim 1, wherein: the volatile organic compound storage tanks are multiple and are operated in parallel.
6. The purification apparatus according to claim 1, wherein: the washing tower is a packed tower or a sieve plate tower.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202120591518.2U CN215196194U (en) | 2021-03-23 | 2021-03-23 | Purification device for caprolactam procedure volatile organic compounds waste gas |
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| CN202120591518.2U CN215196194U (en) | 2021-03-23 | 2021-03-23 | Purification device for caprolactam procedure volatile organic compounds waste gas |
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| CN215196194U true CN215196194U (en) | 2021-12-17 |
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