CN112058021A - Low-temperature methanol washing tail gas VOCs treatment method and device - Google Patents

Abstract

The invention belongs to the technical field of waste gas treatment of chemical plants, and particularly relates to a method and a device for treating VOCs (volatile organic compounds) in low-temperature methanol washing tail gas, which comprises a washing tower, wherein a waste water pipeline for discharging waste water is arranged at the bottom of the washing tower, a tower bottom temperature measuring element is arranged at the bottom of the washing tower, the detection end of the tower bottom temperature measuring element extends into the washing tower, the tower bottom temperature measuring element is fixedly connected with the washing tower, and the tail gas pipeline is connected to the lower part of the lowest layer tower plate of the washing tower; the device is washed to low temperature methyl alcohol influence is less, and the methyl alcohol in the waste water can be retrieved and circulate to low temperature methyl alcohol through methyl alcohol water separation unit and wash the unit reuse, and whole equipment area is little, and the throughput is good, adopts the device that the washing method was handled VOCs, absorbent cyclic utilization, and the working costs is little, and the energy consumption is little, and disposable investment is low, has better economic advantages.

Description

A kind of low temperature methanol washing tail gas VOCs treatment method and device

technical field

The invention belongs to the technical field of waste gas treatment in chemical plants, and in particular relates to a method and a device for treating VOCs in low-temperature methanol washing tail gas.

Background technique

VOCs refer to volatile organic compounds that are easily at room temperature. Most of them exist in incomplete combustion in chemical processes, process emissions from chemical preparation units, volatilization of oil products and volatilization of solvents during use, etc. The common types of VOCs are hydrocarbons, benzene series, aldehydes and alcohols. When the concentration of VOCs in the air is too high, it is easy to cause acute poisoning. In mild cases, symptoms such as headache, dizziness, cough, nausea, and vomiting may occur. In severe cases, it may cause liver poisoning or even coma. Long-term living in this environment will cause chronic poisoning. , damage the liver and nervous system.

The treatment methods of VOCs are mainly preventive measures to prevent leakage and treatment process measures mainly to end treatment. Common treatment technologies include process substitution, oxidative decomposition, biodegradation, absorption and adsorption.

Coal-to-synthesis gas is the first step in the preparation of many chemical products using coal as raw material. The crude synthesis gas contains a large amount of excess CO2, a small amount of H2S, COS and other acid gases. These acid gases are unfavorable for production and must be removed. Methanol washing is an important operation unit in the coal chemical process. Its core function is the acid gas removal technology. It mainly uses methanol as an absorbent, and uses methanol to greatly dissolve acid gases (CO2, H2S, COS, etc.) at low temperature. Excellent characteristics, remove the acid gas in the raw gas, the CO2-rich product gas separated in the process of low temperature absorption and washing contains a large amount of methanol, the methanol in the tail gas belongs to the category of VOCs treatment, through the VOCs treatment technology Not only can a large amount of methanol be recovered and reused, but also the VOCs in the exhaust gas can be treated to meet the emission standards.

SUMMARY OF THE INVENTION

In order to solve the problems raised in the above background art. The invention provides a low-temperature methanol washing tail gas VOCs treatment method and device, which have the characteristics of reliable process performance, convenient operation and broad application prospect.

In order to achieve the above purpose, the present invention provides the following technical solutions: a low-temperature methanol washing tail gas VOCs treatment device, comprising a water washing tower, the bottom of the water washing tower is provided with a waste water pipeline for discharging waste water, and the bottom of the water washing tower is provided with a tower Bottom temperature measuring element, the detection end of the tower bottom temperature measuring element extends into the interior of the water washing tower, the tower bottom temperature measuring element is fixedly connected with the water washing tower, and the tail gas pipeline is connected to the lowermost layer of the water washing tower Below the column plate, the end of the tail gas pipeline runs through the water washing tower and is fixedly connected with the water washing tower. The interior of the water washing tower, that is, close to the top of the tail gas pipeline, is provided with a layer-by-layer downcomer. The downcomer is fixedly connected to the water washing tower, the downcomer is connected to the float valve tray, the float valve tray is fixed inside the water wash tower, and a wire mesh is arranged above the float valve tray demister, the wire mesh demister is fixedly installed on the inner side wall of the water washing tower, and the top of the outer side wall of the water washing tower is provided with a desalted water pipeline, and the desalted water pipeline is located in the float valve tray, the wire mesh Between the net demisters, the desalinated water pipeline is fixedly connected with the water washing tower, the top of the water washing tower is provided with an air outlet pipeline, and the air outlet pipeline is fixedly connected with the water washing tower.

Preferably, the input end of the waste water pipeline is provided with a tower bottom drain pump, the tower bottom drain pump is electrically connected to an external power source, and the tower bottom drain pump is sealedly connected to the waste water pipeline, and the tower bottom drain pump is connected in a sealed manner. The input end of the pump is provided with a waste water pipeline flow regulating valve, and the waste water pipeline flow regulating valve is electrically connected with the tower bottom drainage pump.

Preferably, a differential pressure liquid level transmitter is provided on the outer side wall of the bottom end of the water washing tower, and the input and output ends of the differential pressure liquid level transmitter penetrate through the water washing tower and extend into the Inside the water washing tower, the differential pressure liquid level transmitter is fixedly connected with the water washing tower.

Preferably, the input end of the tail gas pipeline is provided with a tail gas pipeline flow regulating valve, and the tail gas pipeline flow regulating valve is fixedly connected with the tail gas pipeline.

Preferably, a tower bottom pressure transmitter is provided on the outer side wall of the bottom end of the water washing tower, the tower bottom pressure transmitter is fixedly connected with the water washing tower, and the tower bottom pressure transmitter is electrically connected to an external power source. sexual connection.

Preferably, the output end of the desalinated water pipeline is provided with a desalted water pipeline flow control valve, the desalted water pipeline flow control valve is fixedly connected with the desalted water pipeline, and the desalted water pipeline flow control valve is electrically connected to an external power source connect.

Preferably, a tower top pressure transmitter and a tower top temperature measuring element are respectively installed on the top of the water washing tower, and both the tower top pressure transmitter and the tower top temperature measuring element are fixedly connected to the water washing tower.

Preferably, the output end of the air outlet pipe is fixedly connected with a flow control valve of the air outlet pipe, and the flow control valve of the air outlet pipe is electrically connected to an external power source.

A method for treating VOCs in low-temperature methanol washing tail gas, comprising the following steps:

Step S1, the tail gas rich in VOCs from the low-temperature methanol washing tail gas pipeline enters the bottom of the washing tower, and the tail gas moves from bottom to top through the valve hole of the float valve tray of the washing tower;

Step S2, the desalted water enters the upper part of the washing tower from the desalted water pipeline, and the desalinated water flows to the bottom of the tower along the float valve tray and the S-type downcomer from top to bottom, and the tail gas and the desalted water are carried out on the float valve tray. Exchange, desalted water to absorb VOCs in exhaust gas;

In step S3, the purified tail gas enters the discharge system from the gas outlet pipe, and the waste water at the bottom of the tower that absorbs VOCs enters the methanol water separation system from the bottom drain pump of the tower. A pressure transmitter and temperature measuring element are installed at the bottom of the tower to measure the pressure change of the washing tower, the pressure drop and temperature change of the whole tower at any time, and the pressure difference liquid level transmitter is installed at the bottom of the tower to monitor the liquid level change at the bottom of the tower.

Compared with the prior art, the beneficial effects of the present invention are:

In the present invention, the water washing tower is treated with low-temperature methanol washing tail gas VOCs, the process is simple, the operation is convenient, and the environmental effect is good, the treated tail gas meets the requirements of the national standard, and the methanol content in the low-temperature methanol washing and venting waste gas of the purification device is not more than 50mg/Nm3, The method has little influence on the low-temperature methanol washing device, the methanol in the wastewater can be recovered through the methanol-water separation unit and recycled to the low-temperature methanol washing unit for reuse, the whole device occupies a small area, and has good processing capacity, and the VOCs are treated by the water washing method. It has the advantages of low operating cost, low energy consumption, low one-time investment, and good economic advantages. This set of devices is applied to complete sets of devices for processing high-risk chemical exhaust gas. The operating conditions are normal temperature and no Involving high temperature and other operational hidden dangers that are prone to safety accidents, the entire set of devices is relatively safe.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the specification, and are used to explain the present invention together with the embodiments of the present invention, and do not constitute a limitation to the present invention. In the attached image:

FIG. 1 is a schematic structural diagram of the present invention.

In the figure: 1. Water washing tower; 2. Floating valve tray; 3. Downcomer; 4. Wire mesh demister; 5. Desalted water pipeline; 6. Exhaust gas pipeline; 7. Waste water pipeline; 8. Gas outlet pipeline; 9, tower top pressure transmitter; 10, tower top temperature measuring element; 11, tower bottom pressure transmitter; 12, tower bottom temperature measuring element; 13, desalinated water pipeline flow control valve; 14, tail gas pipeline flow control valve ; 15. Wastewater pipeline flow control valve; 16. Outlet pipeline flow control valve; 17. Bottom drainage pump; 18. Differential pressure level transmitter.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Please refer to FIG. 1, the present invention provides the following technical solutions: a low-temperature methanol washing tail gas VOCs treatment device, comprising a water washing tower 1, the bottom of the water washing tower 1 is provided with a waste water pipeline 7 for discharging waste water, and the bottom of the water washing tower 1 is provided with a tower The bottom temperature measuring element 12, the detection end of the tower bottom temperature measuring element 12 extends into the interior of the washing tower 1, the temperature measuring element 12 at the bottom of the tower is fixedly connected with the washing tower 1, and the tail gas pipeline 6 is connected below the bottom plate of the washing tower 1 , the end of the tail gas pipeline 6 runs through the water washing tower 1 and is fixedly connected with the water washing tower 1. The interior of the water washing tower 1, that is, above the tail gas pipeline 6, is provided with a downcomer 3, and the downcomer 3 is fixedly connected with the water washing tower 1. The liquid pipe 3 is connected with the float valve tray 2, the float valve tray 2 is fixed in the interior of the water washing tower 1, a wire mesh demister 4 is arranged above the float valve tray 2, and the wire mesh demister 4 is fixedly installed in the water washing tower. The inner side wall of the tower 1, the top of the outer side wall of the water washing tower 1 is provided with a desalted water pipeline 5, and the desalted water pipeline 5 is located between the float valve tray 2 and the wire mesh demister 4, and the desalted water pipeline 5 is fixedly connected with the water washing tower 1. , the top of the water washing tower 1 is provided with an outlet pipe 8, and the outlet pipe 8 is fixedly connected with the water washing tower 1.

In this embodiment, the water washing tower 1 absorption method is used to absorb the low-temperature methanol washing tail gas containing VOCs gas, and the absorbent adopts desalinated water to avoid introducing new impurities, absorb and wash the methanol in the tail gas, and reduce the methanol content, so that the tail gas can be discharged Indicators, the water washing tower 1 adopts the floating valve tray 2 and the single overflow bow downcomer 3 tower internals, the low-temperature methanol washing tail gas and the demineralized water are in gas-liquid contact on the tray, and the gas-liquid mass transfer of the floating valve tray 2 The effect is good, it has the advantages of high absorption efficiency, large operation flexibility, strong ability to avoid clogging, and good processing capacity. The temperature measuring element 12 measures the pressure change of the washing tower, the pressure drop and temperature change of the whole tower at any time, and a pressure difference liquid level transmitter 18 is set at the bottom of the tower to monitor the liquid level change at the bottom of the tower. 6. Set up flow regulating valves respectively, and ensure the VOCs treatment effect and the smooth operation of the system by controlling the switch and adjusting the opening of the valve. The wastewater after washing in the absorption tower 1 is sent to the methanol water separation tower system by the bottom drainage pump 17 to absorb the waste water in the wastewater. Methanol, the absorbed methanol can be returned to the low-temperature methanol washing unit for reuse. Before the CO2 product gas after washing treatment enters the emission system, an online gas analysis and monitoring system is installed, which can detect the VOCs content in the exhaust gas and the treatment effect in real time, so as to adjust the operation in time. parameter.

Specifically, the input end of the waste water pipeline 7 is provided with a tower bottom drainage pump 17, the tower bottom drainage pump 17 is electrically connected to an external power source, and the tower bottom drainage pump 17 is sealedly connected to the waste water pipeline 7, and the input end of the tower bottom drainage pump 17 A waste water pipeline flow regulating valve 15 is provided, and the waste water pipeline flow regulating valve 15 is electrically connected with the tower bottom drainage pump 17 .

Specifically, a differential pressure liquid level transmitter 18 is provided on the outer side wall of the bottom end of the water washing tower 1 , and the input and output ends of the differential pressure liquid level transmitter 18 penetrate through the water washing tower 1 and extend into the water washing tower 1 . Inside, the differential pressure liquid level transmitter 18 is fixedly connected with the water washing tower 1 .

Specifically, the input end of the tail gas pipeline 6 is provided with a tail gas pipeline flow regulating valve 14 , and the tail gas pipeline flow regulating valve 14 is fixedly connected with the tail gas pipeline 6 .

Specifically, the bottom outer wall of the water washing tower 1 is provided with a tower bottom pressure transmitter 11, the tower bottom pressure transmitter 11 is fixedly connected with the water washing tower 1, and the tower bottom pressure transmitter 11 is electrically connected with an external power source.

Specifically, the output end of the desalinated water pipeline 5 is provided with a desalted water pipeline flow regulating valve 13, which is fixedly connected to the desalted water pipeline 5, and is electrically connected to an external power source.

Specifically, a tower top pressure transmitter 9 and a tower top temperature measuring element 10 are respectively installed on the top of the water washing tower 1 .

Specifically, the output end of the gas outlet pipe 8 is fixedly connected with a gas outlet pipe flow regulating valve 16, and the gas outlet pipe flow regulating valve 16 is electrically connected to an external power source.

The low-temperature methanol washing tail gas VOCs are absorbed by the water washing method. The absorbent is demineralized water, which absorbs the methanol in the tail gas and reduces the VOCs content of the low-temperature methanol washing tail gas, so that the tail gas reaches the emission target. The multi-stage valve tower uses the multi-stage valve tray 2 as the interface for gas-liquid contact mass transfer. The valve tower has the advantages of good gas-liquid mass transfer effect, high processing capacity, high absorption efficiency and high operating flexibility. Water washing tower 1 The tower bottom and the top of the tower are equipped with a tower top pressure transmitter 9 and a tower top temperature measuring element 10 to measure the pressure change of the washing tower 1, the pressure drop and temperature change of the whole tower at any time, and a pressure difference liquid level transmitter 18 is installed at the bottom of the tower. , monitor the liquid level change at the bottom of the tower, set flow regulating valves at the inlet and outlet of the gas phase pipeline and the desalination pipeline respectively, and ensure the VOCs treatment effect and the smooth operation of the system by controlling the switch and adjusting the valve opening. It is sent to the methanol-water separation tower system to absorb the methanol in the wastewater, which can be returned to the low-temperature methanol washing unit for reuse. The CO2 product gas after water washing treatment is equipped with an online gas analysis and monitoring system before entering the discharge system, which can detect the VOCs content in the exhaust gas in real time. and processing effects for timely adjustment of operating parameters.

A method for treating VOCs in low-temperature methanol washing tail gas, comprising the following steps:

Step S1, the tail gas rich in VOCs from the low-temperature methanol washing tail gas pipeline 6 enters the bottom of the water washing tower 1, and the tail gas moves from bottom to top through the valve hole of the float valve tray 2 of the water washing tower 1;

Step S2, the desalted water enters the upper part of the washing tower 1 from the desalted water pipeline 5, and the desalinated water flows to the bottom of the tower along the float tray 2 and the downcomer 3S type from top to bottom, and the tail gas and the desalted water are in the float valve tray 2. The gas-liquid exchange is carried out on the upper side, and the desalinated water absorbs the VOCs in the exhaust gas;

Step S3, the purified tail gas enters the discharge system from the gas outlet pipe, and the waste water at the bottom of the tower that absorbs VOCs enters the methanol water separation system by the bottom drain pump 17. During the absorption process, a pressure transmitter 9 and a measuring device are set on the top of the water washing tower 1 during the absorption process. The temperature element 10, the pressure transmitter 11 and the temperature measuring element 12 are installed at the bottom of the tower to measure the pressure change of the washing tower 1, the pressure drop and temperature change of the whole tower at any time, and the pressure difference liquid level transmitter 18 is installed at the bottom of the tower to monitor the bottom of the tower. of liquid level changes.

Finally, it should be noted that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, the The technical solutions described in the foregoing embodiments may be modified, or some technical features thereof may be equivalently replaced. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (8)

1. The utility model provides a tail gas VOCs processing apparatus is washed to low temperature methyl alcohol which characterized in that: comprises a washing tower (1), wherein a wastewater pipeline (7) used for discharging wastewater is arranged at the bottom of the washing tower (1), a tower bottom temperature measuring element (12) is arranged at the bottom of the washing tower (1), the detection end of the tower bottom temperature measuring element (12) extends into the washing tower (1), the tower bottom temperature measuring element (12) is fixedly connected with the washing tower (1), a tail gas pipeline (6) is arranged at the bottom end of the washing tower (1), the end part of the tail gas pipeline (6) penetrates through the washing tower (1) and is fixedly connected with the washing tower (1), a layer-by-layer downcomer (3) is arranged in the washing tower (1), namely, a space above the tail gas pipeline (6), the downcomer (3) is fixedly connected with the washing tower (1), the downcomer (3) is connected with a float valve (2), and the float valve (2) is fixed in the washing tower (1), the upper layer of the floating valve tower plate (2) is provided with a wire mesh demister (4), the wire mesh demister (4) is fixedly installed on the inner side wall of the water washing tower (1), the top end of the outer side wall of the water washing tower (1) is provided with a desalted water pipeline (5), the desalted water pipeline (5) is located between the floating valve tower plate (2) and the wire mesh demister (4), the desalted water pipeline (5) is fixedly connected with the water washing tower (1), the top of the water washing tower (1) is provided with an air outlet pipeline (8), and the air outlet pipeline (8) is fixedly connected with the water washing tower (1).

2. The device for treating VOCs in the low-temperature methanol-washing tail gas according to claim 1, characterized in that: the input of waste water pipeline (7) is equipped with bottom of the tower drain pump (17), bottom of the tower drain pump (17) and external power source electric connection, just bottom of the tower drain pump (17) with waste water pipeline (7) sealing connection, the input of bottom of the tower drain pump (17) is equipped with waste water pipeline flow control valve (15), waste water pipeline flow control valve (15) with bottom of the tower drain pump (17) electric connection.

3. The device for treating VOCs in the low-temperature methanol-washing tail gas according to claim 2, characterized in that: be equipped with pressure differential liquid level changer (18) on the bottom lateral wall of scrubbing tower (1), the input of pressure differential liquid level changer (18), output all run through scrubbing tower (1) to stretch into extremely the inside of scrubbing tower (1), pressure differential liquid level changer (18) with scrubbing tower (1) fixed connection.

4. The device for treating VOCs in the low-temperature methanol-washing tail gas according to claim 3, wherein: the input end of the tail gas pipeline (6) is provided with a tail gas pipeline flow regulating valve (14), and the tail gas pipeline flow regulating valve (14) is fixedly connected with the tail gas pipeline (6).

5. The device of claim 4, wherein the device for treating VOCs in the low-temperature methanol-washing tail gas comprises: be equipped with pressure transmitter (11) at the bottom of the tower on the bottom lateral wall of washing tower (1), pressure transmitter (11) at the bottom of the tower with washing tower (1) fixed connection, pressure transmitter (11) and external power source electric connection at the bottom of the tower.

6. The device for treating VOCs in the low-temperature methanol-washing tail gas according to claim 5, wherein: the output of desalination water pipe way (5) is equipped with desalination water pipe way flow control valve (13), desalination water pipe way flow control valve (13) with desalination water pipe way (5) fixed connection, desalination water pipe way flow control valve (13) and external power source electric connection.

7. The device of claim 6, wherein the device for treating VOCs in the low-temperature methanol-washing tail gas comprises: the top of the washing tower (1) is respectively provided with a tower top pressure transmitter (9) and a tower top temperature measuring element (10), and the tower top pressure transmitter (9) and the tower top temperature measuring element (10) are fixedly connected with the washing tower (1).

8. The device for treating VOCs in the low-temperature methanol-washing tail gas according to claim 7, wherein: the output end of the air outlet pipeline (8) is fixedly connected with an air outlet pipeline flow regulating valve (16), and the air outlet pipeline flow regulating valve (16) is electrically connected with an external power supply.

A method for treating VOCs in low-temperature methanol washing tail gas is characterized by comprising the following steps: low temperature methanol washing tail gas VOCs processing apparatus, include the following step:

step S1, enabling the tail gas rich in VOCs from the low-temperature methanol washing tail gas pipeline (6) to enter the bottom of the water washing tower (1), and enabling the tail gas to move from bottom to top through a valve hole of a float valve tower plate (2) of the water washing tower (1);

step S2, enabling desalted water to enter the upper part of a water washing tower (1) from a desalted water pipeline (5), enabling the desalted water to flow to the bottom of the tower from top to bottom along an S shape of a float valve tray (2) and a downcomer (3), enabling tail gas and the desalted water to perform gas-liquid exchange on the float valve tray (2), and enabling the desalted water to absorb VOCs in the tail gas;

and S3, enabling the purified tail gas to enter a discharge system from an air outlet pipeline, enabling the tower bottom wastewater for absorbing the VOCs to enter a methanol-water separation system from a tower bottom drainage pump (17), arranging a pressure transmitter (9) and a temperature measuring element (10) on the top of a washing tower (1) in the absorption process, arranging a pressure transmitter (11) and a temperature measuring element (12) on the bottom of the tower to measure the pressure change of the washing tower, the pressure drop and the temperature change of the whole tower at any time, arranging a differential pressure liquid level transmitter (18) on the bottom of the tower, and monitoring the liquid level change at the bottom of the tower.

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