Multi-stage series absorption process for sulfur dioxide generated by incineration of sulfur-containing waste gas

Abstract

The invention discloses a multi-stage series absorption process for sulfur dioxide generated by incineration of sulfur-containing waste gas. SO2 in flue gas of an incinerator is subjected to multi-stage absorption, and then a solution containing sodium hydrogen sulfite can be obtained. The flue gas absorption device is formed by connecting a washing tank, a first-stage alkali liquor absorption tower, a second-stage alkali liquor absorption tower and a third-stage alkali liquor absorption tower in series, so that the aim of multi-stage absorption is fulfilled; and purified gas which is extracted from the top of the third-stage alkali liquor absorption tower and absorbed is discharged by a chimney. The device has the beneficial effects that the washing tank can effectively remove particle impurities such as carbon black and sulfur in the flue gas of the incinerator, the temperature of the flue gas from the incinerator can be reduced, and then the flue gas is cooled by the tower top condenser of the first-stage alkali liquor absorption tower, so that the absorption efficiency of the absorption tower is maintained at the optimal temperature to absorb sulfur dioxide in the flue gas of the incinerator; sodium hydroxide and sodium sulfite mixed alkali liquor is adopted for absorption, a sodium hydrogen sulfite solution is obtained, the content of sulfur dioxide (smaller than 100 ppm) in flue gas is effectively reduced, and the online monitoring requirement is met.

Description

Technical Field

[0001] The patent of this invention belongs to the field of sulfur-containing tail gas treatment, and specifically relates to a method of using desalted water and sodium hydroxide-sodium sulfite mixed alkali solution to react with sulfur dioxide generated after the incineration of sulfur-containing waste gas through a multi-stage series absorption method to generate a sodium bisulfite solution, thereby absorbing sulfur dioxide in the tail gas, reducing the amount of sulfur-containing tail gas, and meeting emission standards. Background Art

[0002] In the production process of dimethyl sulfoxide, sulfur-containing compounds will enter the tail gas section during the raw material preparation and distillation process to form sulfur-containing waste gas, which cannot be discharged directly into the atmosphere. At present, one of the main ways to treat sulfur-containing waste gas is to pass it into an incinerator for incineration, where the sulfur-containing compounds undergo a chemical reaction to generate sulfur dioxide, which is then further treated to purify the sulfur-containing waste gas. However, the "Petroleum Refining Industry Pollutant Emission Standard" (GB31570-2015) proposes that the SO2 limit for acid gas recovery devices in areas with small environmental capacity and fragile ecology must be lower than 100 mg / m 3 Based on this, the patent of the present invention uses water and mixed alkali solution (sodium hydroxide-sodium sulfite) for multi-stage series absorption to absorb sulfur dioxide produced after the incineration of sulfur-containing waste gas to generate sodium bisulfite solution. The innovation of this process lies in the setting of four-stage absorption, including primary water absorption and tertiary alkali absorption. The device mainly includes a water washing tank, a primary alkali absorption tower, a secondary alkali absorption tower and a tertiary alkali absorption tower. The water washing tank performs preliminary absorption of the sulfur-containing flue gas after incineration, which can remove solid particle impurities in the flue gas and ensure that the temperature of the flue gas sent to the alkali absorption tower is maintained at 40-60°C; and the mixed alkali solution of sodium hydroxide and sodium sulfite is used as the absorption liquid to ensure the efficiency of sulfur dioxide absorption in the primary, secondary and tertiary alkali absorption towers. The use of this device to purify sulfur-containing tail gas has the advantages of safety, environmental protection, simple process and high absorption efficiency. Summary of the invention

[0003] The invention aims to provide a method for reacting desalted water and sodium hydroxide-sodium sulfite mixed alkali solution with sulfur dioxide in sulfur-containing tail gas by spraying, and the process is divided into two processes: water absorption and alkali absorption.

[0004] The reaction equation in this process is as follows: SO2+H2O=H2SO32NaOH+H2SO3=2NaHSO3+2H2O 2NaOH+SO2=Na2SO3+H2ONa2SO3+SO2+H2O=2NaHSO3 The present invention is achieved through the following technical solutions: The flue gas after the sulfur-containing waste gas is burned in the incinerator first enters the water washing tank and contacts with the circulating washing liquid (deionized water) in the tank. The soot, sulfur particles and other solid particles in the flue gas are washed down and filtered out by the filter in front of the circulating pump. The filter needs to be cleaned regularly to avoid clogging, and the flue gas is cooled to 50-70℃ at the same time; When the pH value of the washing liquid in the washing tank reaches about 4.5, it is discharged into the primary alkali liquid absorption tower, and then new desalted water is added to absorb the flue gas; the washed flue gas flows out from the top of the washing tank and enters the primary alkali liquid absorption tower; the sodium hydroxide-sodium sulfite mixed alkali liquid continues to absorb sulfur dioxide in the flue gas, and trace amounts of sulfur trioxide in the flue gas are also absorbed; the absorption liquid is cooled by the condenser on the circulation pipeline to ensure that the absorption liquid temperature is below 60°C; The washed flue gas flows out from the top of the primary alkali liquid absorption tower, and enters from the bottom of the secondary alkali liquid absorption tower and the tertiary alkali liquid absorption tower in turn; the flue gas continues to remove sulfur dioxide in the secondary alkali liquid absorption tower and the tertiary alkali liquid absorption tower; The purified flue gas then flows out from the top of the tertiary alkali solution absorption tower, passes through the liquid retaining hood and liquid remover on the top of the tower, is drawn out by the purified flue gas induced draft fan, and is sent to the chimney for high-point discharge. The sulfur dioxide content in the flue gas is ≤100ppm.

[0005] After being treated in a water washing tank, the flue gas enters a primary alkaline solution absorption tower, which can effectively remove particulate impurities in the flue gas and preliminarily cool the flue gas to prevent particulate impurities from clogging the equipment or causing equipment corrosion. Sodium hydroxide-sodium sulfite mixed alkaline solution is used as the absorption liquid to further improve the absorption efficiency of sulfur dioxide in the flue gas.

[0006] Finally, the solutions after water absorption and mixed alkali solution absorption are discharged from the primary alkali solution absorption tower to obtain sodium bisulfite solution, which also contains a small amount of sodium sulfate, etc.

[0007] The device has a high degree of automation, simple process and operation, and can effectively treat sulfur dioxide generated after sulfur-containing waste gas is incinerated in an incinerator, thereby reducing environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 The present invention is a simplified flow chart of the device.

[0009] (1): Incinerator, (2): Water washing tank, (3): Primary alkali solution absorption tower, (4): Primary alkali solution absorption tower condenser, (5): Secondary alkali solution absorption tower, (6): Third alkali solution absorption tower, (7): Induced draft fan, (8): Smoke brine, (9): Liquid alkali (sodium hydroxide) tank, (10): Sodium sulfite solution tank, (11): Filter. DETAILED DESCRIPTION

[0010] The present invention is further described below in conjunction with the accompanying drawings and embodiments. These embodiments should be understood to be only used to illustrate the present invention and not to limit the protection scope of the present invention.

[0011] The sulfur-containing flue gas from the incinerator has a temperature of about 170-240°C. It enters from the bottom of the water washing tank and contacts the circulating water that enters from the top of the water washing tank and sprays down in reverse. The flue gas is cooled to 50-70°C. The particulate impurities and part of the sulfur dioxide in the flue gas enter the circulating water. The particulate impurities are filtered through the filter. When the pH of the water absorption liquid reaches 4.5-5.0, the water absorption liquid is discharged into the primary alkali absorption tower. When the pH in the tank is lower than 4.5, the corrosion risk to the equipment will increase rapidly. At this time, the valve is switched to discharge the absorption liquid into the primary alkali absorption tower, and new desalted water is added at the same time.

[0012] After preliminary washing and cooling, the sulfur-containing flue gas flows out from the top of the water washing tank and enters the lower part of the primary alkali absorption tower. The absorption liquid in the primary alkali absorption tower comes from the secondary alkali absorption tower, the liquid alkali tank and the sodium sulfite solution tank. The absorption liquid is sprayed from the top of the tower and contacts with the sulfur-containing flue gas coming from the bottom to further absorb the sulfur dioxide in the flue gas; the mixed alkali and sulfur dioxide react to release heat, and the temperature of the absorption liquid rises; the absorption liquid in the primary alkali absorption tower is cooled by the condenser under the action of the primary desulfurization circulation pump to reduce the temperature of the absorption liquid and ensure that the temperature of the absorption liquid is maintained at 30-50°C. In this process, part of the sulfur dioxide is absorbed; the pH of the absorption liquid in the tower is controlled between 4.5-5.5, and the absorption time is controlled between 4-8 hours; when the pH of the absorption liquid is around 4.5, the solute in the absorption liquid is sodium bisulfite, and there is basically no sodium carbonate. The absorption liquid is discharged from the bottom of the tower to the collection tank, and the absorption liquid is replenished by the secondary alkali absorption tower.

[0013] The sulfur-containing flue gas washed by the primary alkali liquid absorption tower flows out from the top of the tower and enters the secondary alkali liquid absorption tower to continue absorbing the remaining sulfur dioxide in the sulfur-containing flue gas. The pH in the secondary alkali liquid absorption tower is controlled at 5.5-6.5; when the pH in the secondary alkali liquid absorption tower is around 5.5, the absorption liquid is discharged into the primary alkali liquid absorption tower, and at the same time, the absorption liquid is replenished from the tertiary alkali liquid absorption tower to continue absorbing sulfur dioxide.

[0014] The sulfur-containing flue gas washed by the secondary alkali solution absorption tower flows out from the top of the tower. At this time, the sulfur dioxide content in the sulfur-containing flue gas is very low, and it enters the tertiary alkali solution absorption tower for further absorption. The absorption liquid in the tertiary alkali solution absorption tower comes from the liquid alkali tank and the sodium sulfite solution tank. The pH in the tower is controlled above 8.5 (generally 8.5-13.5). When the pH in the tertiary alkali solution absorption tower is about to be less than 8.5, open the outlet valves of the liquid alkali tank and the sodium sulfite solution tank and add mixed alkali solution in proportion to maintain the pH in the tower to ensure that the sulfur dioxide in the sulfur-containing flue gas is completely absorbed.

[0015] The discharge and discharge of the absorption liquid in the three alkali liquid absorption towers is a dynamic process. According to the pH value of the mixed alkali liquid in the absorption tower and the concentration of sodium hydroxide, the tertiary absorption liquid is discharged into the secondary alkali liquid absorption tower, and the secondary absorption liquid is discharged into the primary alkali liquid absorption tower. At the same time, the tertiary alkali liquid absorption tower is continuously replenished with new mixed alkali liquid (sodium hydroxide-sodium sulfite solution); the absorption liquid of all towers is discharged from the primary alkali liquid absorption tower to the collection tank to obtain sodium bisulfite solution. The purified flue gas is extracted by the purified flue gas induced draft fan, and after pressurization, it is sent out of the boundary area and sent to the chimney for high-point discharge.

[0016] The top of the three-stage alkali liquid absorption tower is equipped with a liquid shield and a liquid remover to remove the liquid entrained in the flue gas. The purified flue gas absorbed by the three-stage alkali liquid absorption tower is discharged through a chimney after passing through an induced draft fan.

[0017] In the initial mixed alkali solution, V (40-50% liquid alkali): V (8-15% sodium sulfite solution) are mixed in a volume ratio of 1:1, and the pH condition is controlled.

[0018] During the cyclic absorption process, the absorption liquid in the tertiary alkali solution absorption tower uses sodium hydroxide solution and sodium sulfite solution to control the pH value at 8.5-13.5; wherein the mass concentration of the sodium hydroxide solution is 15%-30%.

[0019] In some embodiments, after mixed alkali absorption, the mass concentration of the sodium hydroxide solution is also controlled to be 15%-30%; when it is insufficient, the amount of the mixed alkali washing solution is controlled by adding.

[0020] The absorption liquid in the secondary alkali solution absorption tower adopts sodium hydroxide solution and sodium sulfite solution to control the pH value at 5.5-6.5, wherein the mass concentration of the sodium hydroxide solution is 5%-15%.

[0021] In some embodiments, after mixed alkali absorption, during the process of introducing the tertiary alkali washing solution into the secondary alkali washing solution for alkali washing, the mass concentration of the sodium hydroxide solution in the mixed alkali washing solution is also controlled to be 5%-15%.

[0022] The absorption liquid in the primary alkali solution absorption tower adopts sodium hydroxide solution and sodium sulfite solution to control the pH value at 4.5-5.5, wherein the mass concentration of sodium hydroxide solution in the mixed alkali washing liquid is also controlled to be less than 5%; the mass concentration of the obtained sodium bisulfite solution is 15%-40%.

[0023] In some embodiments, further, it is preferred that after the mixed alkali absorption, during the alkaline washing process of introducing the secondary alkaline washing solution into the primary alkaline washing solution, the mass concentration of the sodium hydroxide solution in the mixed alkaline washing solution is also controlled to be less than 2%; the mass concentration of the sodium bisulfite solution is 15%-40%.

[0024] After the above four-stage absorption, the sulfur dioxide content in the sulfur-containing flue gas reaches below 100ppm, ensuring qualified exhaust emissions.

[0025] Example 1 like Figure 1 As shown, sulfur-containing tail gas (including sulfur-containing compounds such as methyl mercaptan, dimethyl sulfide, methanol, carbon disulfide and hydrogen sulfide) enters the incinerator for incineration, the temperature of the water washing tank is controlled at 65°C, and the pH is controlled at 4.5-5.5; the initial mixed alkali solution (V (48% liquid alkali): V (8% sodium sulfite solution)) enters the third-level alkali solution absorption tower at a volume ratio of 1:1 to absorb sulfur dioxide in the flue gas, the temperature is controlled at 55-70°C, the pH is controlled at 8.5-11, and the sodium hydroxide concentration is about 20%-25%; the temperature of the secondary alkali solution absorption tower is controlled at 55-70°C, the pH is controlled at 5.5-6.5, and the sodium hydroxide concentration is about 10%-15%; the temperature of the primary alkali solution absorption tower is controlled at 65°C, the pH is controlled at 4.5-5.5, and the sodium hydroxide concentration is less than 2%; when the pH of the primary alkali solution absorption tower is about 4.5, the absorption liquid is discharged to obtain a sodium bisulfite solution with a concentration of 15-25%.

[0026] It was determined that the sulfur dioxide content in the purified flue gas was 48ppm; Example 2 like Figure 1 As shown, sulfur-containing tail gas (including sulfur-containing compounds such as methyl mercaptan, dimethyl sulfide, methanol, carbon disulfide and hydrogen sulfide) enters the incinerator for incineration, the temperature of the water washing tank is controlled at 40-50°C, and the pH is controlled at 4.5-5.5; the initial mixed alkali solution (V (48% liquid alkali): V (9% sodium sulfite solution)) enters the third-level alkali solution absorption tower at a volume ratio of 1:1 to absorb sulfur dioxide in the flue gas, the temperature is controlled at 40-50°C, the pH is controlled at 8.5-11, and the sodium hydroxide concentration is about 15%-20%; the temperature of the second-level alkali solution absorption tower is controlled at 40-50°C, the pH is controlled at 5.5-6.5, and the sodium hydroxide concentration is about 5%-10%; the temperature of the first-level alkali solution absorption tower is controlled at 40-50°C, the pH is controlled at 4.5-5.5, and the sodium hydroxide concentration is less than 2%. When the pH of the first-level alkali solution absorption tower is about 4.5, the absorption liquid is discharged to obtain a sodium bisulfite solution with a concentration of 20-35%.

[0027] It was determined that the sulfur dioxide content in the purified flue gas was 25ppm; Example 3 like Figure 1As shown, sulfur-containing tail gas (including sulfur-containing compounds such as methyl mercaptan, dimethyl sulfide, methanol, carbon disulfide and hydrogen sulfide) enters the incinerator for incineration, the temperature of the water washing tank is controlled at 40-50°C, and the pH is controlled at 4.5-5.5; the initial mixed alkali solution (V (48% liquid alkali): V (12% sodium sulfite solution)) enters the third-level alkali solution absorption tower at a volume ratio of 1:1 to absorb sulfur dioxide in the flue gas, the temperature is controlled at 40-50°C, the pH is controlled at 8.5-11, and the sodium hydroxide concentration is about 15-18%; the temperature of the second-level alkali solution absorption tower is controlled at 40-50°C, the pH is controlled at 5.5-6.5, and the sodium hydroxide concentration is about 13%-15%; the temperature of the first-level alkali solution absorption tower is controlled at 40-50°C, the pH is controlled at 4.5-5.5, and the sodium hydroxide concentration is less than 2%. When the pH of the first-level alkali solution absorption tower is about 4.5, the absorption liquid is discharged to obtain a sodium bisulfite solution with a concentration of 10-15%.

[0028] It was measured that the sulfur dioxide content in the purified flue gas was 61ppm.

[0029] Example 4 like Figure 1 As shown, sulfur-containing tail gas (including sulfur-containing compounds such as methyl mercaptan, dimethyl sulfide, methanol, carbon disulfide and hydrogen sulfide) enters the incinerator for incineration, the temperature of the water washing tank is controlled at 40-50℃, and the pH is controlled at 4.5-5.5; the initial alkali solution (48% sodium hydroxide solution) enters the third-level alkali solution absorption tower to absorb sulfur dioxide in the flue gas, the temperature is controlled at 40-50℃, the pH is controlled at 8.5-11, and the sodium hydroxide concentration is about 30-40%; the temperature of the second-level alkali solution absorption tower is controlled at 40-50℃, the pH is controlled at 5.5-6.5, and the sodium hydroxide concentration is about 15%-25%; the temperature of the first-level alkali solution absorption tower is controlled at 40-50℃, the pH is controlled at 4.5-5.5, and the sodium hydroxide concentration is less than 5%. When the pH of the first-level alkali solution absorption tower is about 4.5, the absorption liquid is discharged to obtain a sodium bisulfite solution with a concentration of 8-12%.

[0030] It was measured that the sulfur dioxide content in the purified flue gas was 412ppm.

Claims

1. A multi-stage series absorption method for sulfur dioxide generated by the incineration of sulfur-containing waste gas, characterized in that: The steps include: The sulfur dioxide-containing flue gas after incineration is sequentially washed with water, absorbed and purified by liquid alkali in the primary alkali liquid absorption tower, the secondary alkali liquid absorption tower and the tertiary alkali liquid absorption tower, and the purified flue gas is discharged into the flue gas brine through the induced draft fan; During the three-stage alkali solution absorption process, the absorption liquid is successively introduced from the absorption liquid of the tertiary alkali solution absorption tower into the secondary alkali solution absorption tower for absorption, and then introduced from the absorption liquid of the secondary alkali solution absorption tower into the primary alkali solution absorption tower for absorption, and the absorption liquid after water washing is introduced into the primary alkali solution absorption tower for absorption.

2. The multi-stage series absorption process for sulfur dioxide generated by the incineration of sulfur-containing waste gas according to claim 1 is characterized in that: During the water washing absorption process, the pH is maintained at 4.5-5.

0. When the pH is about to be less than 4.5, the aqueous solution is sent to the primary alkali solution absorption tower for absorption.

3. The multi-stage series absorption process for sulfur dioxide generated by the incineration of sulfur-containing waste gas according to claim 1 is characterized in that: The pH in the primary alkali liquid absorption tower is controlled at 4.5-5.

5. When the pH in the primary alkali liquid absorption tower is about to be less than 4.5, the absorption liquid in the secondary alkali liquid absorption tower is sent to the primary alkali liquid absorption tower to increase the pH in the tower; the absorption time of the primary alkali liquid absorption tower is controlled at 4-8 hours. When the pH is between 4.5-5.5, the absorption liquid is discharged to the collection tank; and the absorption liquid in the secondary alkali liquid absorption tower is sent to the primary alkali liquid absorption tower for continued absorption.

4. The multi-stage series absorption process for sulfur dioxide generated by the incineration of sulfur-containing waste gas according to claim 1 is characterized in that: The pH in the secondary alkali liquid absorption tower is controlled at 5.5-6.

5. When the pH in the secondary alkali liquid absorption tower is about to be less than 5.5, the solution in the tertiary alkali liquid absorption tower is sent to the secondary alkali liquid absorption tower to increase the pH in the tower.

5. The multi-stage series absorption process for sulfur dioxide generated by the incineration of sulfur-containing waste gas according to claim 1 is characterized in that: The pH in the tertiary alkali solution absorption tower is controlled at 8.5-13.

5. When the pH in the tertiary alkali solution absorption tower is about to be less than 8.5, open the outlet valves of the liquid alkali tank and the sodium sulfite solution tank and add mixed alkali solution in proportion to maintain the pH in the tower.

6. The multi-stage series absorption process for sulfur dioxide generated by the incineration of sulfur-containing waste gas according to claim 1 is characterized in that: The solution absorbed by the water washing tank, the primary alkali solution absorption tower, the secondary alkali solution absorption tower and the tertiary alkali solution absorption tower is discharged through the primary alkali solution absorption tower to obtain a solution containing sodium bisulfite.

7. The multi-stage series absorption process for sulfur dioxide generated by the incineration of sulfur-containing waste gas according to claim 1 is characterized in that: The top of the three-stage alkali liquid absorption tower is equipped with a liquid shield and a liquid remover to remove the liquid entrained in the flue gas. The purified flue gas absorbed by the three-stage alkali liquid absorption tower is discharged through a chimney after passing through an induced draft fan.

8. The multi-stage series absorption process for sulfur dioxide generated by the incineration of sulfur-containing waste gas according to claim 1 is characterized in that: The absorption liquid in the tertiary alkali solution absorption tower adopts sodium hydroxide solution and sodium sulfite solution to control the pH value at 8.5-13.5; wherein, in the initial solution, the mass concentration of sodium hydroxide solution is 40%-50%; the mass concentration of sodium sulfite solution is 8%-15%.

9. The multi-stage series absorption process for sulfur dioxide generated by the incineration of sulfur-containing waste gas according to claim 8, characterized in that: The absorption liquid in the secondary alkali solution absorption tower adopts sodium hydroxide solution and sodium sulfite solution to control the pH value at 5.5-6.5, wherein the mass concentration of the sodium hydroxide solution is 5%-15%.

10. The multi-stage series absorption process for sulfur dioxide generated by the incineration of sulfur-containing waste gas according to claim 8, characterized in that: The absorption liquid in the primary alkali solution absorption tower adopts sodium hydroxide solution and sodium sulfite solution to control the pH value at 4.5-5.5, wherein the mass concentration of the sodium hydroxide solution is less than 5%.

Images