A high concentration methanol waste gas treatment system

Abstract

The invention discloses a high-concentration methanol waste gas treatment system, including a multi-effect absorption tower, which is sequentially provided with a mixed adsorption section, a spray pipe 1, a spray device, a liquid storage tank 1, a falling film absorption section and a liquid storage tank 2 from top to bottom, a filler for improving the mixing performance of water mist and waste gas is provided in the mixed adsorption section, the mixed adsorption device is connected with a water mist generator, the water mist generator is connected with a soft water inlet pipe, the multi-effect absorption tower between the mixed adsorption section and the spray device is connected with a high-concentration methanol waste gas inlet pipe, the spray pipe 1 is connected with the liquid storage tank 2 through a circulating pump 2, a partition for extending the waste gas spraying stroke is provided in the spray device, and a spray device connected with the mixed adsorption section is provided on the multi-effect absorption tower between the falling film absorption section and the liquid storage tank 2. The invention has a high degree of integration, low investment, effectively reduces the floor space, improves the absorption effect, significantly improves the operation stability and convenience, and efficiently achieves standard emission.

Description

Technical Field

[0001] The invention relates to the technical field of waste gas treatment, and in particular to a high-concentration methanol waste gas treatment system. Background Art

[0002] Methanol is a good chemical solvent with low freezing point and low viscosity. It is widely used in formaldehyde manufacturing, pesticide production and other industries. In the process of formaldehyde manufacturing and pesticide production, a large amount of methanol is used. Methanol is easy to volatilize, and a large amount of high-concentration methanol waste gas will inevitably be produced. Methanol is toxic, and high-concentration methanol waste gas will cause great harm to the human body and the environment. As environmental protection requirements become more and more stringent, high-concentration methanol waste gas must be treated to meet the standards before it can be discharged.

[0003] For high-concentration methanol waste gas, the industry currently mainly adopts one-stage spray or two-stage spray absorption treatment. However, due to the incomplete spray contact effect, the treated waste gas still contains a large amount of methanol. The waste gas cannot be discharged directly because the treatment does not meet the standards. In response to this situation, the industry currently mainly adopts two methods: (1) The treated waste gas is sent to RTO for combustion treatment. This method requires the addition of a set of RTO devices, resulting in increased construction investment and increased floor space. In addition, because the methanol concentration contained in the waste gas is not enough to support its own combustion, a large amount of additional fuel is required, resulting in increased operating costs; (2) The treated waste gas is sent to an activated carbon adsorption device. This method requires the addition of a set of activated carbon adsorption devices. After a period of activated carbon adsorption, the adsorption efficiency decreases and the activated carbon needs to be replaced. The operating cost is very high. In addition, the activated carbon after methanol adsorption is hazardous waste, and the temporary storage and treatment methods are strict, and the treatment cost is high. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a high-concentration methanol waste gas treatment system with good absorption effect, stable and convenient operation, high degree of integration and low investment.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions: a high-concentration methanol waste gas treatment system, comprising a multi-effect absorption tower, the multi-effect absorption tower is provided with a mixed adsorption section, a spray pipe 1, a spray device, a liquid storage tank 1, a falling film absorption section and a liquid storage tank 2 in sequence from top to bottom, the mixed adsorption section is provided with a filler for improving the mixing performance of water mist and waste gas, the mixed adsorption section is connected to a water mist generator, the water mist generator is connected to a soft water inlet pipe, the multi-effect absorption between the mixed adsorption section and the spray device The collecting tower is connected with an air inlet pipe for high-concentration methanol waste gas, the spray pipe one and the liquid storage tank two are connected with a circulating pump two, the spray device is provided with a partition for extending the waste gas spraying stroke, the liquid storage tank one below the spray device is connected with the multi-effect absorption tower above the falling film absorption section, the multi-effect absorption tower between the falling film absorption section and the liquid storage tank two is provided with an injection device connected with the mixed adsorption section, and the multi-effect absorption tower between the falling film absorption section and the liquid storage tank one is connected with an exhaust gas discharge pipe.

[0006] Furthermore, the injection device includes an injector, a first inlet of the injector is connected to the liquid storage tank 2 through a circulation pump 1, a second inlet of the injector is connected to the top of the multiple-effect absorption tower, and an outlet of the injector is connected to the multiple-effect absorption tower between the falling film absorption section and the liquid storage tank 2.

[0007] Furthermore, the spray device includes a primary spray section and a secondary spray section formed by vertical spacing of the partition.

[0008] Furthermore, the liquid storage tank 1 discharges the liquid in the liquid storage tank 1 to the spray pipe 2 above the falling film absorption section through a liquid level interlocking valve.

[0009] Furthermore, the mixed adsorption section is connected to the liquid storage tank one through a pipe two for discharging the liquid in the mixed adsorption section to the liquid storage tank one, and the multi-effect absorption tower between the mixed adsorption section and the spraying device is connected to a pipe one for introducing the exhaust gas into the mixed adsorption section, and the pipe two is inserted below the liquid level of the liquid storage tank one.

[0010] Furthermore, a complexing absorption tower is provided between the multiple-effect absorption tower and the tail gas discharge pipe for further absorbing trace methanol in the exhaust gas through a complexing agent.

[0011] Furthermore, the complex absorption tower is provided with a complex absorption section and a liquid storage tank three from top to bottom, a circulation pump three is connected between the liquid storage tank three and the spray pipe three above the complex absorption section, and the tail gas discharge pipe is connected to the top of the complex absorption tower.

[0012] Furthermore, a demisting layer is provided above the spray pipe 2 and the spray pipe 3 to reduce the moisture content of the exhaust gas.

[0013] Furthermore, the water outlets of the circulating pump 1, the circulating pump 2, and the circulating pump 3 and the pipeline 1 are all provided with check valves.

[0014] Furthermore, the complexing agent is a mixture of one or more of aluminum chloride, magnesium chloride and calcium chloride.

[0015] Compared with the prior art, the advantages of the present invention are: the present invention utilizes multiple technologies such as multi-effect absorption, mixed adsorption, and complex absorption to couple the treatment of high-concentration methanol waste gas, with a high degree of integration and low investment, effectively reducing the floor space, improving the absorption effect, significantly improving the operational stability and convenience, and efficiently achieving standard emissions; it comprehensively solves the difficulties of poor removal effect in the traditional high-concentration methanol waste gas process, and the need to add activated carbon adsorption, RTO and other devices at the back end, resulting in high investment, large floor space and the generation of hazardous waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic structural diagram of an embodiment of the present invention.

[0017] In the figure: 1. Multi-effect absorption tower; 11. Mixed adsorption section; 12. Spray pipe one; 13. Liquid storage tank one; 14. Falling film absorption section; 15. Liquid storage tank two; 16. Spray pipe two; 171. Secondary spray section; 172. Primary spray section; 181. Pipeline one; 182. Pipeline two; 2. Water mist generator; 21. Soft water inlet pipe; 3. High-concentration methanol waste gas inlet pipe; 4. Circulation device; 41. Circulation pump one; 42. Circulation pump two; 43. Circulation pump three; 5. Tail gas emission pipe; 6. Ejector; 7. Liquid level interlocking valve; 8. Complex absorption tower; 81. Complex absorption section; 82. Liquid storage tank three; 83. Spray pipe three; 84. Demisting layer. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] See attached Figure 1The present embodiment comprises a multi-effect absorption tower 1, which is provided with a mixed absorption section 11, a spray pipe 12, a spray device, a liquid storage tank 13, a falling film absorption section 14 and a liquid storage tank 2 15 from top to bottom in sequence, a filler for improving the mixing performance of water mist and exhaust gas is provided in the mixed absorption section 11, the mixed absorption section 11 is connected to a water mist generator 2, the water mist generator 2 is connected to a soft water inlet pipe 21, a high-concentration methanol exhaust gas inlet pipe 3 is connected to the multi-effect absorption tower 1 between the mixed absorption section 11 and the spray device, and the spray pipe 13 is connected to the multi-effect absorption tower 1 between the mixed absorption section 11 and the spray device. A 12 is connected to a liquid storage tank 15 through a circulation pump 42. A partition is provided in the spray device for extending the exhaust gas spraying stroke. The liquid storage tank 13 below the spray device is connected to the multi-effect absorption tower 1 above the falling film absorption section 14 through a pipeline. The multi-effect absorption tower 1 between the falling film absorption section 14 and the liquid storage tank 15 is provided with an injection device connected to the mixed adsorption section 11. The multi-effect absorption tower 1 between the falling film absorption section 14 and the liquid storage tank 13 is connected to an exhaust gas emission pipe, and the exhaust gas emission pipe is connected to the complex absorption tower 8.

[0020] It is difficult to effectively capture all the methanol molecules in the exhaust gas by the spraying method. In this embodiment, a water mist generator 2 is used to generate a large amount of water mist. After the water mist and the exhaust gas are fully mixed in the mixed adsorption section 11, the methanol molecules in the exhaust gas are fully adsorbed on the tiny water mist and are easily fully captured. Because the diameter of the water mist is small, the contact area with the exhaust gas is significantly increased, thereby significantly improving the treatment effect, solving the problem that it is difficult to effectively capture all the methanol molecules in the exhaust gas by the liquid spraying method. A falling film absorption section 14 is set at the bottom of the multi-effect absorption tower 1, which can further improve the removal rate of methanol in the exhaust gas.

[0021] In addition, this embodiment adopts falling film absorption, which can also significantly reduce the water content in the exhaust gas; it uses multiple technologies such as multi-effect absorption, mixed adsorption, and complex absorption to couple the treatment of high-concentration methanol exhaust gas, with a high degree of integration and low investment, effectively reducing the floor space, improving the absorption effect, and significantly improving the operational stability and convenience, and efficiently achieving standard emissions; it comprehensively solves the difficult problems of poor removal effect in the traditional high-concentration methanol exhaust gas treatment process, and the need to add activated carbon adsorption, RTO and other devices at the back end, resulting in high investment, large floor space, and the generation of hazardous waste.

[0022] The injection device includes an injector 6, the first inlet of the injector 6 is connected to the second liquid storage tank 15 through a circulation pump 1 41, the second inlet of the injector 6 is connected to the top of the multi-effect absorption tower 1, and the outlet of the injector 6 is connected to the multi-effect absorption tower 1 between the falling film absorption section 14 and the second liquid storage tank 15. The injector 6 is used to transfer the gaseous water mist adsorbed with methanol from the gaseous state to the liquid state, so that the methanol in the waste gas is efficiently removed; in addition, the injector 6 generates a vacuum in the mixed adsorption section 11, so that the waste gas has a flow power in the whole system, so that the system is free from the setting of the induced draft fan, and the energy consumption and noise of the system are reduced; when the mixed absorption method is used to treat high-concentration methanol waste gas, a large number of methanol molecules are adsorbed on the tiny water mist, and how to effectively desorb the tiny water mist from the waste gas becomes the key to this technology. This embodiment uses an injector 6, and the tiny water mist is quickly dissolved into the solution through the injector 6, and the methanol adsorbed on the water mist is dissolved into the water together, so as to effectively reduce the methanol concentration in the waste gas.

[0023] The spraying device includes a secondary spraying section 171 and a primary spraying section 172 formed by vertical spacing of a partition. The secondary spraying section 171 and the primary spraying section 172 are both from the same spraying pipe, and the spraying liquid is transported from the bottom of the multi-effect absorption tower 1 through a circulation pump 2 42, and the spraying liquid falling from the secondary spraying section 171 and the primary spraying section 172 is stored in a liquid storage tank 13.

[0024] In the traditional process, a spray tower is used to wash methanol in the waste gas. The poor treatment effect is generally caused by the short contact time between the waste gas and the spray liquid, which is not sufficient. In the traditional process, multiple spray towers are also used in series. Although the washing effect is improved, the floor space is too large, the one-time investment of the equipment increases, and the required spray pumps also increase accordingly. In this embodiment, the secondary spray section 171 and the primary spray section 172 are arranged side by side at the same height position of the multi-effect absorption tower 1, which not only increases the travel of the waste gas in the spray filler, but also effectively improves the spray absorption effect; and only one spray is used for the two spray sections, which improves the operational stability and reduces the floor space of the spray head inside the tower.

[0025] The liquid storage tank 13 discharges the liquid in the liquid storage tank 13 to the spray pipe 2 16 above the falling film absorption section 14 through the liquid level interlocking valve 7. The liquid storage tank 13 at the bottom of the primary spray section 172 and the secondary spray section 171 is provided with a pipe opening connected to the spray pipe 2 16 at the top of the falling film absorption section 14. The connecting pipeline is provided with a regulating valve, which is interlocked with the liquid level of the liquid storage tank 13, so that the spray liquid is from top to bottom, and the operation is convenient, continuous and stable, realizing full automatic operation.

[0026] The mixed adsorption section 11 is connected to the liquid storage tank 13 by a pipe 182 for discharging the liquid in the mixed adsorption section 11 to the liquid storage tank 13. The pipe is inserted below the liquid level of the liquid storage tank 13 to prevent the waste gas from entering the mixed adsorption section 11 through the pipe 182, causing a short circuit of the waste gas. The multi-effect absorption tower 1 between the mixed adsorption section 11 and the spray device is connected to a pipe 181 for introducing the waste gas into the mixed adsorption section 11.

[0027] A complexing absorption tower 8 is provided between the multiple-effect absorption tower 1 and the tail gas discharge pipe 5 to further absorb trace methanol in the exhaust gas through a complexing agent. After the multiple-effect absorption in the multiple-effect absorption tower 1, most of the methanol in the exhaust gas is removed, and only a trace amount of methanol is contained in the exhaust gas; by providing the complexing absorption tower 8, the trace amount of methanol in the exhaust gas can be removed, and the exhaust gas can be discharged up to standard.

[0028] The complex absorption tower 8 is provided with a complex absorption section 81 and a liquid storage tank 3 82 from top to bottom, and the liquid storage tank 3 82 is connected to the spray pipe 3 83 above the complex absorption section 81 through a circulation pump 3 43, and the tail gas discharge pipe 5 is connected to the top of the complex absorption tower 8. In the complex absorption tower 8, the waste gas and the complex absorption liquid flow in countercurrent, and the methanol in the waste gas reacts with the complex absorption liquid to form a complex body, so that the residual trace methanol in the waste gas can be efficiently removed in the complex absorption tower 8. After the waste gas passes through the demisting layer 84 set at the top of the complex absorption tower 8 to reduce the moisture content, it is discharged from the top of the complex absorption tower 8 in compliance with the standards.

[0029] A demisting layer 84 for reducing the moisture content of the exhaust gas is provided above the spray pipe 2 16 and the spray pipe 3 83. After the exhaust gas passes through the falling film absorption section 14 and is reversely absorbed by the spray liquid, the exhaust gas further rises, and then passes through the demisting layer 84 provided at the top of the falling film absorption section 14 to reduce the moisture content, and then flows out from the top of the falling film absorption section 14.

[0030] Check valves are provided on the water outlets of the circulation pump 1 41 , the circulation pump 2 42 , and the circulation pump 3 43 and the pipeline 1 181 .

[0031] The complexing agent is a mixture of one or more of aluminum chloride, magnesium chloride, and calcium chloride. The basic principle of complex absorption is: taking aluminum chloride as an example, methanol and aluminum chloride can form a complex AlCl3.10CH3OH, and the content of methanol adsorbed in the complex is high and stable. The complex absorption method can well remove trace methanol in the waste gas. And the complex can achieve complex decomposition under the condition of increasing the temperature, so as to realize the recycling of the complexing agent.

[0032] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and changes obtained without departing from the technical concept of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A high concentration methanol waste gas treatment system, characterized in that: The invention comprises a multi-effect absorption tower (1), wherein the multi-effect absorption tower (1) is provided with a mixing absorption section (11), a spray pipe (12), a spray device, a liquid storage tank (13), a falling film absorption section (14) and a liquid storage tank (15) in order from top to bottom; a filler for improving the mixing performance of water mist and exhaust gas is provided in the mixing absorption section (11); the mixing absorption section (11) is connected to a water mist generator (2); the water mist generator (2) is connected to a soft water inlet pipe (21); a high pressure pipe (21) is connected to the mixing absorption section (11) and the spray device; The invention relates to an exhaust gas inlet pipe (3) for concentrated methanol, a circulating pump (42) is connected between the spray pipe (12) and the liquid storage tank (15), a baffle for extending the exhaust gas spraying stroke is provided in the spray device, the liquid storage tank (13) below the spray device is connected to the spray pipe (16) above the falling film absorption section (14) through a pipeline, and a spray device connected to the mixed adsorption section (11) is provided on the multi-effect absorption tower (1) between the falling film absorption section (14) and the liquid storage tank (15), and the falling film absorption section (14) is connected to the liquid storage tank (1). (13) is connected to a tail gas discharge pipe; the injection device comprises an injector (6), a first inlet of the injector (6) is connected to the second liquid storage tank (15) through a circulation pump (41), a second inlet of the injector (6) is connected to the top of the multi-effect absorption tower (1), and an outlet of the injector (6) is connected to the multi-effect absorption tower (1) between the falling film absorption section (14) and the second liquid storage tank (15); the spray device comprises a primary spray section (172) and a secondary spray section ( 171); a complex absorption tower (8) for further absorbing trace methanol in the exhaust gas through a complexing agent is provided between the multiple-effect absorption tower (1) and the exhaust gas discharge pipe (5); the complex absorption tower (8) is provided with a complex absorption section (81) and a liquid storage tank (82) from top to bottom, a circulation pump (43) is connected between the liquid storage tank (82) and a spray pipe (83) above the complex absorption section (81), and the exhaust gas discharge pipe (5) is connected to the top of the complex absorption tower (8); the complexing agent is a mixture of one or more of aluminum chloride, magnesium chloride and calcium chloride.

2. The high-concentration methanol waste gas treatment system according to claim 1, characterized in that: The liquid storage tank 1 (13) is connected to a spray pipe 2 (16) through a liquid level interlocking valve (7) for discharging the liquid in the liquid storage tank 1 (13) to the top of the falling film absorption section (14).

3. The high-concentration methanol waste gas treatment system according to claim 1, characterized in that: A second pipe (182) for discharging the liquid in the mixed adsorption section (11) to the first liquid storage tank (13) is connected between the mixed adsorption section (11) and the first liquid storage tank (13); a first pipe (181) for introducing the waste gas into the mixed adsorption section (11) is connected on the multi-effect absorption tower (1) between the mixed adsorption section (11) and the spraying device; and the second pipe (182) is inserted below the liquid level of the first liquid storage tank (13).

4. The high-concentration methanol waste gas treatment system according to claim 1, characterized in that: A demisting layer (84) for reducing the moisture content of the exhaust gas is provided above the second spray pipe (16) and the third spray pipe (83).

5. A high-concentration methanol waste gas treatment system according to claim 3, characterized in that: Check valves are provided on the water outlets of the circulation pump 1 (41), the circulation pump 2 (42), and the circulation pump 3 (43) and the pipeline 1 (181).

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