Method and system for recovering carbon dioxide from reaction tail gas

Abstract

The invention provides a method and a system for recovering carbon dioxide from reaction tail gas. The method for recovering carbon dioxide from reaction tail gas comprises the following steps: S1, providing sodium hydroxide absorption liquid with the concentration of 8.7-9%; s2, introducing the reaction tail gas into an absorption tower from the bottom of the absorption tower, adding a sodium hydroxide absorption liquid into the absorption tower from the top of the absorption tower, and absorbing carbon dioxide in the reaction tail gas by the sodium hydroxide absorption liquid to obtain an absorbed solution with the sodium hydroxide mass fraction of 1-3%; wherein the reaction tail gas is tail gas containing carbon dioxide generated in the benzyl alcohol production process, and the mass ratio of the sodium hydroxide absorption liquid added into the absorption tower to the reaction tail gas is (22-25): 1; and S3, introducing the absorbed solution into an alkaline water tank for producing benzyl alcohol. According to the invention, efficient emission reduction and resource recycling can be realized at the same time, and the effects of emission reduction, carbon reduction and cost saving are achieved.

Description

Technical Field

[0001] This invention belongs to the field of chemical waste gas treatment technology, specifically relating to a method and system for recovering carbon dioxide from reaction waste gas. Background Technology

[0002] The production of benzyl alcohol generates a large amount of reaction tail gas containing carbon dioxide (CO2). Currently, while alkaline absorption can be used to treat this tail gas, traditional alkaline scrubbing is only a final-end treatment method. The resulting sodium carbonate solution is treated as hazardous waste, failing to effectively utilize carbon resources and increasing solid waste disposal costs. Therefore, developing a closed-loop tail gas treatment process that can simultaneously achieve efficient emission reduction and resource recovery is of great significance. Summary of the Invention

[0003] In view of this, the present invention provides a method and system for recovering carbon dioxide from reaction tail gas, which can simultaneously achieve efficient emission reduction and resource reuse, thereby achieving the effects of emission reduction, carbon reduction and cost saving.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for recovering carbon dioxide from reaction tail gas, comprising the following steps: S1. Provide sodium hydroxide absorbent solution with a concentration of 8.7%~9%; S2. The reaction tail gas is introduced into the absorption tower from the bottom, and the sodium hydroxide absorbent is added into the absorption tower from the top. The sodium hydroxide absorbent absorbs the carbon dioxide in the reaction tail gas to obtain an absorption solution with a sodium hydroxide mass fraction of 1% to 3%. The reaction tail gas is the tail gas containing carbon dioxide generated during the production of benzyl alcohol. The mass ratio of the sodium hydroxide absorbent added to the absorption tower to the reaction tail gas is (22~25):1. S3. Pass the absorbed solution into an alkaline water tank for the production of benzyl alcohol.

[0005] Preferably, step S1 includes: mixing liquid alkali with a concentration of 48% with water in an alkali-refining kettle to obtain a sodium hydroxide absorption solution with a concentration of 8.7% to 9%.

[0006] Preferably, in step S1, the temperature of the sodium hydroxide absorption solution is 40°C to 50°C.

[0007] Preferably, in step S2, if the mass fraction of sodium hydroxide in the absorbed solution is less than 1%, the amount of sodium hydroxide absorbent added is increased; if the mass fraction of sodium hydroxide in the absorbed solution is greater than 3%, a portion of the absorbed solution is added to the absorption tower until the mass fraction of sodium hydroxide in the absorbed solution is 1% to 3%.

[0008] Preferably, in step S2, the sodium hydroxide absorbent is added to the absorption tower by spraying.

[0009] Secondly, the present invention also provides a system for recovering carbon dioxide from reaction tail gas, for realizing the method of recovering carbon dioxide from reaction tail gas, the system including an absorption tower and an alkaline water tank, the top of the absorption tower is provided with a liquid inlet and a gas outlet, and the bottom is provided with a gas inlet and a liquid outlet, the liquid outlet being connected to the alkaline water tank.

[0010] Preferably, a water tank is provided below the absorption tower, the liquid outlet of the absorption tower is connected to the water tank, and the water tank is connected to the top of the absorption tower and the alkaline water tank respectively.

[0011] Preferably, an alkaline water buffer tank is provided between the water tank and the alkaline water tank, and the alkaline water buffer tank is connected to both the water tank and the alkaline water tank.

[0012] Preferably, it also includes an alkali-refining kettle, which is connected to the liquid inlet of the absorption tower.

[0013] Preferably, the system further includes a reaction vessel, which is connected to the alkaline water tank. The reaction vessel is provided with a tail gas outlet, which is connected to the gas inlet of the absorption tower.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, by limiting the concentration of sodium hydroxide absorbent, the mass ratio of sodium hydroxide absorbent added to the absorption tower to the reaction tail gas, and the mass fraction of sodium hydroxide in the solution after absorption, carbon dioxide in the reaction tail gas can be efficiently absorbed, effectively reducing carbon emissions. At the same time, the absorption product can be directly used as a raw material for benzyl alcohol production, saving procurement costs. Thus, efficient emission reduction and resource recycling can be achieved simultaneously, achieving the effects of emission reduction, carbon reduction, and cost saving. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the system for recovering carbon dioxide from reaction tail gas provided by the present invention.

[0016] Explanation of reference numerals in the attached figures: 1. Alkali treatment kettle; 2. Absorption tower; 3. Water tank; 4. Alkali water buffer tank; 5. Alkali water tank; 6. Reactor; 7. Tail gas buffer tank; 8. Carbon adsorption tower. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention.

[0018] In a first aspect, the present invention provides a method for recovering carbon dioxide from reaction tail gas, comprising the following steps: S1. Provide sodium hydroxide absorbent solution with a concentration of 8.7%~9%; S2. The reaction tail gas is introduced into the absorption tower 2 from the bottom, and the sodium hydroxide absorbent is added into the absorption tower 2 from the top. The sodium hydroxide absorbent absorbs the carbon dioxide in the reaction tail gas to obtain an absorption solution with a sodium hydroxide mass fraction of 1% to 3%. The reaction tail gas is the tail gas containing carbon dioxide generated during the production of benzyl alcohol. The mass ratio of the sodium hydroxide absorbent added to the absorption tower 2 to the reaction tail gas is (22~25):1. S3. Pass the absorbed solution into alkaline water tank 5 for the production of benzyl alcohol.

[0019] In this invention, by limiting the concentration of sodium hydroxide absorbent, the mass ratio of sodium hydroxide absorbent added to absorption tower 2 to the reaction tail gas, and the mass fraction of sodium hydroxide in the solution after absorption, carbon dioxide in the reaction tail gas can be efficiently absorbed, effectively reducing carbon emissions. At the same time, the absorption product can be directly used as a raw material for benzyl alcohol production, saving procurement costs. Thus, efficient emission reduction and resource recycling can be achieved simultaneously, achieving the effects of emission reduction, carbon reduction, and cost saving.

[0020] It should be noted that the concentration in the sodium hydroxide absorbent solution with a concentration of 8.7%~9% refers to the mass fraction of sodium hydroxide in the absorbent solution. The concentration of the sodium hydroxide absorbent solution can be 8.7%, 8.8%, 8.9%, or 9.0%. The reaction tail gas is introduced into the absorption tower 2 from the bottom, and the sodium hydroxide absorbent solution is added to the absorption tower 2 from the top. The sodium hydroxide absorbent solution and the reaction tail gas undergo a countercurrent absorption reaction in the absorption tower 2. The sodium hydroxide absorbent solution efficiently absorbs carbon dioxide in the reaction tail gas. The mass ratio of the sodium hydroxide absorbent solution added to the absorption tower 2 to the reaction tail gas can be 22:1, 23:1, 24:1, or 25:1. The resulting absorption solution with a sodium hydroxide mass fraction of 1%~3% can be directly used as a raw material for benzyl alcohol production. It can also prevent the generation of sodium bicarbonate and avoid clogging of equipment and pipelines.

[0021] In some embodiments, step S1 includes: mixing 48% liquid alkali with water in an alkali-refining reactor 1 to obtain a sodium hydroxide absorbent solution with a concentration of 8.7% to 9%. Using a 48% concentration liquid alkali mixed with water facilitates industrial production. The water can be distilled water.

[0022] In some embodiments, in step S1, the temperature of the sodium hydroxide absorbent is 40°C to 50°C. A temperature within this range can improve the absorption efficiency of carbon dioxide in the reaction tail gas. It should be noted that when preparing the sodium hydroxide absorbent by mixing 48% liquid alkali with water in the alkali-dissolving reactor 1, circulating water can be introduced into the coil of the alkali-dissolving reactor 1 to absorb the heat released during the dilution of the liquid alkali, thus controlling the temperature to 40°C to 50°C.

[0023] In some embodiments, in step S2, if the mass fraction of sodium hydroxide in the absorbed solution is less than 1%, the amount of sodium hydroxide absorbent added is increased; if the mass fraction of sodium hydroxide in the absorbed solution is greater than 3%, a portion of the absorbed solution is added to absorption tower 2 until the mass fraction of sodium hydroxide in the absorbed solution is 1%~3%. The mass fraction of sodium hydroxide in the absorbed solution can be monitored using detection methods. By adjusting the absorbed solution in the above manner, the mass fraction of sodium hydroxide in the absorbed solution can be controlled to be 1%~3%. Through flow control and circulation adjustment mechanisms, the stability of the composition of the absorbed solution can be ensured, guaranteeing the safety and reliability of the recycled product for the main production process, and making it easy to promote and implement in industry.

[0024] In some embodiments, in step S2, the sodium hydroxide absorbent is added to the absorption tower 2 by spraying. Spraying the sodium hydroxide absorbent from the top of the absorption tower 2 allows for more thorough contact between the absorbent and the reaction tail gas, thereby improving the absorption efficiency of carbon dioxide in the reaction tail gas.

[0025] Secondly, please refer to Figure 1 The present invention also provides a system for recovering carbon dioxide from reaction tail gas, for realizing the method of recovering carbon dioxide from reaction tail gas. The system includes an absorption tower 2 and an alkaline water tank 5. The top of the absorption tower 2 is provided with a liquid inlet and a gas outlet, and the bottom is provided with a gas inlet and a liquid outlet. The liquid outlet is connected to the alkaline water tank 5.

[0026] In this invention, the reaction tail gas is introduced into the absorption tower 2 through the bottom inlet, and the sodium hydroxide absorbent is added into the absorption tower 2 through the top inlet. The sodium hydroxide absorbent and the reaction tail gas undergo a countercurrent absorption reaction in the absorption tower 2. The sodium hydroxide absorbent efficiently absorbs the carbon dioxide in the reaction tail gas, and the resulting absorbed solution is discharged through the outlet and introduced into the alkaline water tank 5 for the production of benzyl alcohol. After being adsorbed by the sodium hydroxide absorbent, the reaction tail gas is discharged through the top outlet.

[0027] In some embodiments, a water tank 3 is provided below the absorption tower 2, and the outlet of the absorption tower 2 is connected to the water tank 3. The water tank 3 is connected to the top of the absorption tower 2 and the alkaline water tank 5. The absorbed solution is discharged into the water tank 3 through the outlet. When the mass fraction of sodium hydroxide in the absorbed solution in the water tank 3 is 1%~3% (qualified Na2CO3, NaOH solution), the absorbed solution in the water tank 3 is passed into the alkaline water tank 5. If the mass fraction of sodium hydroxide in the absorbed solution in the water tank 3 is greater than 3%, part of the absorbed solution in the water tank 3 can be added to the absorption tower 2 from the top to adjust the mass fraction of the absorbed solution in the water tank 3. A return port can be provided at the top of the absorption tower 2, and the water tank 3 is connected to the return port.

[0028] In some embodiments, the water tank 3 is connected to the top of the absorption tower 2 via a first pipe, and a first pressurizing pump is installed on the first pipe. The first pressurizing pump is used to pressurize and transport a portion of the absorbed solution in the water tank 3 to the absorption tower 2 to adjust the mass fraction of the absorbed solution.

[0029] In some embodiments, an alkaline buffer tank 4 is provided between the water tank 3 and the alkaline water tank 5, and the alkaline buffer tank 4 is connected to both the water tank 3 and the alkaline water tank 5. The alkaline buffer tank 4 is used for transferring and storing the absorbed sodium hydroxide solution with a mass fraction of 1% to 3%.

[0030] In some embodiments, the system further includes an alkali-refining reactor 1, which is connected to the inlet of the absorption tower 2. The alkali-refining reactor 1 is used to prepare a sodium hydroxide absorption solution with a concentration of 8.7% to 9%.

[0031] In some embodiments, the inlet of the alkali-dissolving kettle 1 and the inlet of the absorption tower 2 are connected by a second pipeline, on which a second pressurizing pump and a first flow control device are respectively installed. The second pressurizing pump is used to pressurize and deliver the sodium hydroxide absorbent in the alkali-dissolving kettle 1 to the absorption tower 2, and the first flow control device is used to control the amount of sodium hydroxide absorbent added.

[0032] In some embodiments, the system further includes a reaction vessel 6, which is connected to the alkaline water tank 5. The reaction vessel 6 is provided with a tail gas outlet, which is connected to the inlet of the absorption tower 2. The reaction vessel 6 is used to produce benzyl alcohol, and the tail gas containing carbon dioxide produced is discharged through the tail gas outlet and introduced into the absorption tower 2 from the inlet at the top of the absorption tower 2.

[0033] In some embodiments, a tail gas buffer tank 7 is provided between the reactor 6 and the absorption tower 2, and the tail gas buffer tank 7 is connected to the tail gas outlet of the reactor 6 and the gas inlet of the absorption tower 2. The tail gas buffer tank 7 is used for transferring and storing the reaction tail gas.

[0034] In some embodiments, the tail gas buffer tank 7 is connected to the air inlet at the top of the absorption tower 2 via a third pipe, on which a fan and a second flow control device are respectively installed. The fan is used to pressurize and transport the reaction tail gas in the tail gas buffer tank 7 to the absorption tower 2, and the second flow control device is used to control the amount of reaction tail gas added.

[0035] In some embodiments, a spray tower is provided in the absorption tower 2. The spray tower is located at the top of the absorption tower 2 and is connected to the liquid inlet of the absorption tower 2. The spray tower is used to add sodium hydroxide absorbent to the absorption tower 2 by spraying.

[0036] In some embodiments, the system further includes a carbon adsorption tower 8, the inlet of which is connected to the outlet of the absorption tower 2, and the carbon adsorption tower 8 is provided with an exhaust port open to the atmosphere. The carbon adsorption tower 8 is used to remove harmful substances from the exhaust gas after adsorption.

[0037] Example 1 This embodiment provides a method for recovering carbon dioxide from reaction tail gas, including the following steps: In the alkali treatment kettle 1, 48% liquid alkali is mixed with distilled water to prepare a sodium hydroxide absorption solution with a concentration of 8.7%. The reaction tail gas is introduced into the absorption tower 2 from the bottom, and the amount of carbon dioxide in the reaction tail gas is 2100 kg / h. Sodium hydroxide absorbent is sprayed into the absorption tower 2 from the top, and the flow rate of sodium hydroxide absorbent is controlled at 48300 kg / h by a pressure pump and a flow meter (i.e., maintaining a liquid-to-gas mass ratio of 23:1). In the absorption tower 2, the gas and liquid phases are in countercurrent contact, and carbon dioxide is absorbed efficiently. After absorption, the solution flows into water tank 3 and overflows into alkaline water buffer tank 4.

[0038] The test results showed that the mass fraction of sodium hydroxide (NaOH) in the solution after absorption was 1.9% and the mass fraction of sodium carbonate (Na2CO3) was 9.4%, which met the control requirement of 1%~3% for sodium hydroxide. The solution after absorption was pumped into alkaline water tank 5 for later use and reused in the benzyl alcohol reaction synthesis section. The carbon dioxide absorption efficiency of the reaction tail gas was 91%.

[0039] Unless otherwise specified, all raw materials used in this invention are existing substances that can be purchased directly from the market.

[0040] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for recovering carbon dioxide from reaction tail gas, characterized in that, Includes the following steps: S1. Provide sodium hydroxide absorbent solution with a concentration of 8.7%~9%; S2. The reaction tail gas is introduced into the absorption tower from the bottom, and the sodium hydroxide absorbent is added into the absorption tower from the top. The sodium hydroxide absorbent absorbs the carbon dioxide in the reaction tail gas to obtain an absorption solution with a sodium hydroxide mass fraction of 1% to 3%. The reaction tail gas is the tail gas containing carbon dioxide generated during the production of benzyl alcohol. The mass ratio of the sodium hydroxide absorbent added to the absorption tower to the reaction tail gas is (22~25):

1. S3. Pass the absorbed solution into an alkaline water tank for the production of benzyl alcohol.

2. The method for recovering carbon dioxide from reaction tail gas according to claim 1, characterized in that, Step S1 includes: mixing 48% liquid alkali with water in an alkali dissolving kettle to obtain a sodium hydroxide absorption solution with a concentration of 8.7%~9%.

3. The method for recovering carbon dioxide from reaction tail gas according to claim 1, characterized in that, In step S1, the temperature of the sodium hydroxide absorption solution is 40℃~50℃.

4. The method for recovering carbon dioxide from reaction tail gas according to claim 1, characterized in that, In step S2, if the mass fraction of sodium hydroxide in the absorbed solution is less than 1%, the amount of sodium hydroxide absorbent added is increased; if the mass fraction of sodium hydroxide in the absorbed solution is greater than 3%, a portion of the absorbed solution is added to the absorption tower until the mass fraction of sodium hydroxide in the absorbed solution is 1% to 3%.

5. The method for recovering carbon dioxide from reaction tail gas according to claim 1, characterized in that, In step S2, the sodium hydroxide absorbent is added to the absorption tower by spraying.

6. A system for recovering carbon dioxide from reaction tail gas, characterized in that, The system for implementing the method for recovering carbon dioxide from reaction tail gas according to any one of claims 1 to 5 includes an absorption tower and an alkaline water tank. The top of the absorption tower is provided with a liquid inlet and a gas outlet, and the bottom is provided with a gas inlet and a liquid outlet. The liquid outlet is connected to the alkaline water tank.

7. The system for recovering carbon dioxide from reaction tail gas according to claim 6, characterized in that, A water tank is provided below the absorption tower, and the liquid outlet of the absorption tower is connected to the water tank. The water tank is connected to the top of the absorption tower and the alkali water tank.

8. The system for recovering carbon dioxide from reaction tail gas according to claim 7, characterized in that, An alkaline water buffer tank is provided between the water tank and the alkaline water tank, and the alkaline water buffer tank is connected to both the water tank and the alkaline water tank.

9. The system for recovering carbon dioxide from reaction tail gas according to claim 6, characterized in that, It also includes an alkali-refining kettle, which is connected to the liquid inlet of the absorption tower.

10. The system for recovering carbon dioxide from reaction tail gas according to claim 6, characterized in that, It also includes a reaction vessel, which is connected to the alkaline water tank. The reaction vessel is provided with a tail gas outlet, which is connected to the gas inlet of the absorption tower.

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