Waste gas comprehensive treatment system and method for purifying methanol-containing tail gas by using same

Abstract

The invention belongs to the technical field of environmental treatment, and particularly relates to a comprehensive waste gas treatment system and a method for purifying methanol-containing tail gas by using the comprehensive waste gas treatment system. The waste gas comprehensive treatment system provided by the invention comprises a washing tower 6, a waste gas container 1 communicated with a gas inlet in the lower part of the washing tower 6, a regenerated wastewater container 2 and a demineralized water container 3 which are respectively communicated with a liquid inlet in the upper part of the washing tower 6, and a wastewater treatment unit 5 communicated with a liquid outlet in the bottom of the washing tower 6, the emptying device 4 is communicated with a gas outlet in the top of the washing tower 6; and the wastewater treatment unit 5 comprises microorganisms. When the waste gas comprehensive treatment system provided by the invention is used for treating the methanol-containing tail gas, the regenerated wastewater is used for replacing part of demineralized water, so that the consumption of the demineralized water is reduced on the premise of ensuring that the methanol content in the purified tail gas is relatively low, and the treatment cost is greatly reduced. Meanwhile, integrated treatment of waste gas and waste water is achieved, the treatment cost is reduced, and meanwhile waste generated in the treatment process is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental treatment, and in particular relates to a comprehensive waste gas treatment system and a method for purifying methanol-containing tail gas using the same. Background Art

[0002] Chemical production processes generate tail gas containing methanol, which can pollute the environment if discharged directly. To minimize environmental impact, methanol is typically separated from the tail gas through water washing. However, traditional water washing methods consume a lot of water and generate a large amount of wastewater, which can easily lead to secondary pollution. Summary of the Invention

[0003] In view of this, the present invention provides a comprehensive waste gas treatment system and a method for purifying methanol-containing tail gas using the same. The method provided by the present invention realizes the recycling of wastewater, reduces the use of desalted water, and greatly reduces the cost of treating methanol-containing tail gas; at the same time, the method provided by the present invention reuses the wastewater after treating methanol-containing tail gas, avoiding the generation of secondary pollution.

[0004] In order to solve the above technical problems, the present invention provides a comprehensive waste gas treatment system, comprising a washing tower 6, an exhaust gas container 1 connected to the lower air inlet of the washing tower 6, a regenerated wastewater container 2 and a desalted water container 3 respectively connected to the upper liquid inlet of the washing tower 6, a wastewater treatment unit 5 connected to the bottom liquid outlet of the washing tower 6, and an emptying device 4 connected to the top air outlet of the washing tower 6;

[0005] The wastewater treatment unit 5 includes microorganisms.

[0006] Preferably, the exhaust gas container 1 is connected to the washing tower 6 through an induced draft fan 7.

[0007] Preferably, the liquid outlet at the bottom of the washing tower 6 is connected to the wastewater treatment unit 5 via a delivery pump 8;

[0008] A valve and a flow meter are provided in the pipeline connecting the delivery pump 8 and the wastewater treatment unit 5 .

[0009] Preferably, a reflux pipe is provided at the liquid outlet of the delivery pump 8, the reflux pipe is connected to the washing port in the middle of the washing tower 6, and a valve and a flow meter are provided in the reflux pipe.

[0010] The present invention also provides the use of the comprehensive waste gas treatment system described in the above technical solution in treating methanol-containing tail gas.

[0011] The present invention also provides a method for purifying methanol-containing tail gas using the comprehensive waste gas treatment system described in the above technical solution, comprising the following steps:

[0012] The mixture of the regenerated wastewater and the desalted water is subjected to countercurrent adsorption with the methanol-containing tail gas in a washing tower 6 to obtain purified tail gas and methanol-containing wastewater respectively;

[0013] Utilizing the exhaust device 4 to exhaust the purified tail gas;

[0014] The methanol-containing wastewater is transported to the wastewater treatment unit 5 as a carbon source for biofilm wastewater treatment.

[0015] Preferably, the pH value of the regenerated wastewater is 6.5-9, the total amount of suspended solids in the regenerated wastewater is <100 ppm, the mass concentration of sulfide in the regenerated wastewater is 100-250 mg / L, the mass concentration of chloride ions in the regenerated wastewater is 200-600 mg / L, and the mass concentration of ammonia nitrogen in the regenerated wastewater is 1500-2000 mg / L.

[0016] Preferably, the mass ratio of the regenerated wastewater to the desalted water is 1.8 to 2.3:1.

[0017] Preferably, the mass concentration of methanol in the methanol-containing tail gas is 119-291 mg / Nm 3 The volume flow rate of the methanol-containing tail gas is 100,000 to 120,000 Nm 3 / h.

[0018] Preferably, the mass ratio of the mixed solution of the regenerated wastewater and the desalted water to the methanol-containing tail gas is 1-2:10-20.

[0019] The present invention provides a comprehensive waste gas treatment system, comprising a washing tower 6, a waste gas container 1 connected to the lower air inlet of the washing tower 6, a regenerated wastewater container 2 and a desalted water container 3 respectively connected to the upper liquid inlet of the washing tower 6, a wastewater treatment unit 5 connected to the bottom liquid outlet of the washing tower 6, and an emptying device 4 connected to the top air outlet of the washing tower 6; the wastewater treatment unit 5 includes microorganisms. When the comprehensive waste gas treatment system provided by the present invention is used to treat methanol-containing tail gas, the regenerated wastewater is used to replace part of the desalted water, and the methanol content in the purified tail gas is ensured to be less than 50mg / Nm 3Under the premise of reducing the amount of desalted water, the treatment cost is greatly reduced. At the same time, the present invention uses the methanol in the methanol-containing wastewater obtained after treatment as the carbon source of the downstream wastewater treatment unit, which can provide nutrients for microorganisms to promote the growth and metabolism of microorganisms and accelerate the degradation of pollutants; the downstream wastewater treatment unit does not need to supplement the carbon source by using the upstream methanol-containing wastewater, thereby reducing the carbon source consumption and wastewater treatment cost; and the reuse of methanol-containing wastewater reduces its impact on the environment. The comprehensive waste gas treatment system provided by the present invention couples waste gas and wastewater treatment technologies to achieve integrated treatment of waste gas and wastewater, reducing treatment costs while reducing the generation of waste during the treatment process. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic structural diagram of the comprehensive exhaust gas treatment system provided by the present invention;

[0021] Figure 2 Schematic diagram of the structure of the comprehensive exhaust gas treatment system used in an embodiment of the present invention;

[0022] Among them, 1 is the exhaust gas container, 2 is the regenerated wastewater container, 3 is the desalted water container, 4 is the emptying device, 5 is the wastewater treatment unit, 6 is the washing tower, 7 is the induced draft fan, and 8 is the delivery pump. DETAILED DESCRIPTION

[0023] The present invention provides a comprehensive waste gas treatment system, comprising a washing tower 6, an exhaust gas container 1 connected to the lower air inlet of the washing tower 6, a regenerated wastewater container 2 and a desalted water container 3 respectively connected to the upper liquid inlet of the washing tower 6, a wastewater treatment unit 5 connected to the bottom liquid outlet of the washing tower 6, and an emptying device 4 connected to the top air outlet of the washing tower 6;

[0024] The wastewater treatment unit 5 includes microorganisms.

[0025] As a specific embodiment of the present invention, the comprehensive exhaust gas treatment system includes a scrubber 6, which can be a packed tower containing Pall rings. The scrubber 6 can be constructed of 304 stainless steel, which reduces corrosion. As a specific embodiment of the present invention, a safety valve can be installed at the top of the scrubber 6. The model of the safety valve can be 3K4-HTB-G, and the set pressure can be 0.45 MPaG. The present invention can release gas through the safety valve to the cold flare pipe network to prevent overpressure in the equipment.

[0026] As a specific embodiment of the present invention, the exhaust gas comprehensive treatment system includes an exhaust gas container 1 connected to the lower air inlet of the washing tower 6. The exhaust gas container 1 can be connected to the washing tower 6 through an induced draft fan 7. In the present invention, the induced draft fan 7 can provide power for the methanol-containing tail gas to ensure its pressure and flow.

[0027] As a specific embodiment of the present invention, the comprehensive waste gas treatment system includes a regenerated wastewater container 2 and a desalted water container 3 respectively connected to the upper liquid inlet of the washing tower 6; the regenerated wastewater container 2 and the desalted water container 3 can be connected to the washing tower 6 in parallel, and a valve and a flow meter can be set on the pipeline connecting the regenerated wastewater container 2 and the washing tower 6; a valve and a flow meter can be set on the pipeline connecting the desalted water container 3 and the washing tower 6.

[0028] As a specific embodiment of the present invention, the comprehensive waste gas treatment system includes a wastewater treatment unit 5 connected to the bottom liquid outlet of the washing tower 6; the bottom liquid outlet of the washing tower 6 can be connected to the wastewater treatment unit 5 through a delivery pump 8; a valve and a flow meter can be provided in the pipeline connecting the delivery pump 8 and the wastewater treatment unit 5; the wastewater treatment unit 5 includes microorganisms.

[0029] In one embodiment of the present invention, a reflux pipe can be provided at the outlet of the delivery pump 8, the reflux pipe being connected to the wash port in the middle of the scrubbing tower 6. The reflux pipe is provided with a valve and a flow meter. In the present invention, the methanol-containing wastewater obtained by treating the methanol-containing tail gas can be transported to the scrubbing tower via the reflux pipe to flush the packing in the scrubbing tower, thereby recycling the methanol-containing wastewater.

[0030] As a specific embodiment of the present invention, the exhaust gas comprehensive treatment system includes an exhaust device 4 connected to the top outlet of the scrubber 6; the exhaust device can be an outlet valve. In the present invention, the purified exhaust gas can be discharged through the exhaust device 4.

[0031] Figure 1 This is a structural schematic diagram of the comprehensive waste gas treatment system provided by the present invention, wherein 1 is a waste gas container, 2 is a regenerated wastewater container, 3 is a desalted water container, 4 is an emptying device, 5 is a wastewater treatment unit, 6 is a washing tower, 7 is an induced draft fan, and 8 is a delivery pump.

[0032] The present invention also provides the use of the comprehensive waste gas treatment system described in the above technical solution in treating methanol-containing tail gas.

[0033] The present invention also provides a method for purifying methanol-containing tail gas using the comprehensive waste gas treatment system described in the above technical solution, comprising the following steps:

[0034] The mixture of the regenerated wastewater and the desalted water is subjected to countercurrent adsorption with the methanol-containing tail gas in a washing tower 6 to obtain purified tail gas and methanol-containing wastewater respectively;

[0035] Utilizing the exhaust device 4 to exhaust the purified tail gas;

[0036] The methanol-containing wastewater is transported to the wastewater treatment unit 5 as a carbon source for biofilm wastewater treatment.

[0037] The present invention conducts countercurrent adsorption of a mixture of regenerated wastewater and desalted water with methanol-containing tail gas in a scrubbing tower 6 to obtain purified tail gas and methanol-containing wastewater, respectively. As a specific embodiment of the present invention, the pH value of the regenerated wastewater can be 6.5 to 9, or 7 to 8; the total amount of suspended solids in the regenerated wastewater can be less than 100 ppm, or 50 to 90 ppm; the mass concentration of sulfide in the regenerated wastewater can be 100 to 250 mg / L, or 120 to 200 mg / L; the mass concentration of chloride ions in the regenerated wastewater can be 200 to 600 mg / L, or 300 to 500 mg / L; and the mass concentration of ammonia nitrogen in the regenerated wastewater can be 1500 to 2000 mg / L, or 1600 to 1800 mg / L. As a specific embodiment of the present invention, the regenerated wastewater can be obtained by regenerating wastewater, which can include wastewater generated during coal gasification. In a specific embodiment of the present invention, before conveying the regenerated wastewater to the scrubber 6, the process may further include: mixing the regenerated wastewater with a flocculant, subjecting the mixture to sedimentation, and then filtering. The flocculant may be a polyacrylamide aqueous solution having a mass concentration of 5 to 8 wt%, or even 6 to 7 wt%. The present invention removes solid impurities from the regenerated wastewater through sedimentation and filtration, thereby preventing clogging of the scrubber or pipeline.

[0038] As a specific embodiment of the present invention, the mass ratio of the regenerated wastewater to the desalted water can be 1.8 to 2.3:1, and can be specifically 1.8:1, 2:1, 2.1:1, 2.2:1 or 2.3:1.

[0039] As a specific embodiment of the present invention, the mass concentration of methanol in the methanol-containing tail gas can be 119 to 291 mg / Nm 3 , can also be 150~250mg / Nm 3 The temperature of the methanol-containing tail gas can be 20-35°C, or 25-30°C; the volume flow rate of the methanol-containing tail gas can be 100,000-120,000 Nm 3 / h, which can be specifically 100000Nm 3 / h、105000Nm 3 / h、110000Nm3 / h or 120000Nm 3 / h.

[0040] As a specific embodiment of the present invention, the mass ratio of the mixed solution of regenerated wastewater and desalted water to the methanol-containing tail gas can be 1-2:10-20, and can be specifically 1.7:10, 1.7:15, 1.7:18, 1.7:19, or 1.7:20.

[0041] After obtaining the purified tail gas, the present invention uses the exhaust device 4 to exhaust the purified tail gas. As a specific embodiment of the present invention, the mass concentration of methanol in the purified tail gas can be 50 mg / Nm 3 Below, it can also be 20~40mg / Nm 3 .

[0042] After obtaining the methanol-containing wastewater, the present invention transports the methanol-containing wastewater to the wastewater treatment unit 5 as a carbon source for biofilm wastewater treatment. As a specific embodiment of the present invention, part of the methanol-containing wastewater can also be refluxed to the washing tower 6 to wash the filler.

[0043] In order to further illustrate the present invention, the technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0044] Example Utilization Figure 2 The system shown purifies tail gas containing methanol.

[0045] Example 1

[0046] (1) Tail gas process flow: After heat exchange in the heat exchanger, the temperature of the methanol-containing tail gas is 20°C (the methanol-containing tail gas includes CO2, N2, H2S and CH3OH, and the CH3OH content is 200mg / Nm 3 ) through the induced draft fan (centrifugal fan, equipment design flow rate 100816.21Nm 3 / h) to raise the pressure to above 10kPa, according to 100000Nm 3 / h is fed into the washing tower 6 (filled with ball rings, 4200mm in diameter and 15950mm in height) through the air inlet at the lower part of the washing tower 6, and is subjected to countercurrent adsorption washing with a mixed solution of regenerated wastewater (flow rate of 6t / h) and desalted water (flow rate of only 3t / h) to obtain purified tail gas and methanol-containing wastewater; the methanol content in the purified tail gas after adsorption washing is 30mg / Nm 3 Vent through the outlet valve at the top of the scrubber.

[0047] The regenerated wastewater is obtained by regenerating the wastewater generated in the coal gasification process. The pH value of the regenerated wastewater is 7.5 (the pH value is adjusted by adding nitric acid with a mass concentration of 40%), the total amount of suspended solids is 70ppm, the mass concentration of sulfide is 180mg / L (hydrogen sulfide in the wastewater is removed by steam stripping), the mass concentration of chloride ions is 400mg / L, and the mass concentration of ammonia nitrogen is 1800mg / L; the regenerated wastewater and flocculant (polyacrylamide with a mass concentration of 5%) are mixed for sedimentation and filtration, and then mixed with desalted water and transported to the washing tower; the mass ratio of regenerated wastewater to desalted water is 2:1.

[0048] (2) Wastewater process flow: The methanol-containing wastewater is pressurized to 0.8 MPa by a delivery pump (flow rate 28.5 t / h, head 50 m, motor power 11 kW) and then delivered in two streams. One stream is regulated to 17 t / h by a flow meter and refluxed to the washing tower through a reflux pipe to wash the filler. The other stream is regulated to 9 t / h by a flow meter and sent to the methanol washing liquid level regulating valve for merging and then sent to the downstream wastewater treatment unit 5. The methanol in the methanol-containing wastewater provides a carbon source for the wastewater treatment unit 5.

[0049] Example 1: The methanol content in the tail gas is reduced from 200 mg / Nm 3 Reduced to 30mg / Nm 3 , ensuring that the exhaust gas meets the requirements of GB 31571 "Petrochemical Industry Pollutant Emission Standard"; low washing water consumption: the washing water used in the washing tower mainly utilizes the regenerated wastewater from coal gasification, and a small amount of clean desalted water is added to reduce the washing water consumption; the flow rate of the supplementary clean desalted water is only 3t / h, and the flow rate of recycled regenerated wastewater is 6t / h, saving 6t / h of desalted water consumption.

[0050] In this invention, the methanol in the methanol-containing wastewater serves as a carbon source for downstream wastewater treatment, providing carbon nutrition for microorganisms, promoting their growth and metabolism, and accelerating pollutant degradation. By using the upstream methanol-containing wastewater, the downstream wastewater treatment unit does not need to supplement with an additional carbon source, reducing carbon source consumption and wastewater treatment costs.

[0051] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A comprehensive waste gas treatment system, characterized in that: The invention comprises a washing tower (6), an exhaust gas container (1) connected to the lower air inlet of the washing tower (6), a regenerated wastewater container (2) and a desalted water container (3) respectively connected to the upper liquid inlet of the washing tower (6), a wastewater treatment unit (5) connected to the bottom liquid outlet of the washing tower (6), and an emptying device (4) connected to the top air outlet of the washing tower (6); The wastewater treatment unit (5) includes microorganisms.

2. The comprehensive exhaust gas treatment system according to claim 1, characterized in that: The waste gas container (1) is connected to the washing tower (6) via an induced draft fan (7).

3. The comprehensive exhaust gas treatment system according to claim 1, characterized in that: The liquid outlet at the bottom of the washing tower (6) is connected to the wastewater treatment unit (5) via a delivery pump (8); A valve and a flow meter are provided in the pipeline connecting the delivery pump (8) and the wastewater treatment unit (5).

4. The comprehensive exhaust gas treatment system according to claim 3, characterized in that: A reflux pipe is provided at the liquid outlet of the delivery pump (8), the reflux pipe is communicated with the washing port in the middle of the washing tower (6), and a valve and a flow meter are provided in the reflux pipe.

5. Use of the comprehensive waste gas treatment system according to any one of claims 1 to 4 in treating methanol-containing tail gas.

6. A method for purifying methanol-containing tail gas using the comprehensive waste gas treatment system according to any one of claims 1 to 4, characterized in that: The following steps are involved: The mixed solution of the regenerated wastewater and the desalted water is subjected to countercurrent adsorption with the methanol-containing tail gas in a washing tower (6) to obtain purified tail gas and methanol-containing wastewater respectively; Utilizing the exhaust device (4) to exhaust the purified tail gas; The methanol-containing wastewater is transported to a wastewater treatment unit (5) and used as a carbon source for biofilm wastewater treatment.

7. The method for purifying methanol-containing tail gas according to claim 6, characterized in that: The pH value of the regenerated wastewater is 6.5-9, the total amount of suspended solids in the regenerated wastewater is less than 100 ppm, the mass concentration of sulfide in the regenerated wastewater is 100-250 mg / L, the mass concentration of chloride ions in the regenerated wastewater is 200-600 mg / L, and the mass concentration of ammonia nitrogen in the regenerated wastewater is 1500-2000 mg / L.

8. The method for purifying methanol-containing tail gas according to claim 6 or 7, characterized in that: The mass ratio of the regenerated wastewater to the desalted water is 1.8 to 2.3:

1.

9. The method for purifying methanol-containing tail gas according to claim 6, characterized in that: The mass concentration of methanol in the methanol-containing tail gas is 119-291 mg / Nm 3 The volume flow rate of the methanol-containing tail gas is 100,000 to 120,000 Nm 3 / h.

10. The method for purifying methanol-containing tail gas according to claim 6 or 9, characterized in that: The mass ratio of the mixed liquid of the regenerated wastewater and the desalted water to the methanol-containing tail gas is 1-2:10-20.

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