A method and system for reducing the corrosiveness of CO2 absorbents in flue gas.

Abstract

The application discloses a method and system for reducing the corrosion of flue gas CO2 alcohol amine absorbent, comprising the following steps: desulfurized flue gas enters the bottom of a comprehensive tower through a first induced draft fan, is reversely contacted with a first absorbent after passing through a gas distributor, is reversely contacted with a second absorbent in a first packing section after passing through a first gas rising cap, is reversely contacted with a third absorbent in a second packing section after passing through a second gas rising cap, then passes through a demister, enters a dehumidification and oxygen removal tower from the comprehensive tower, enters an absorption tower through a second induced draft fan, and performs CO2 capture; the purified flue gas is discharged from the top of the tower; rich amine liquid discharged from the bottom of the absorption tower enters a dissolved oxygen removal device; the rich amine liquid with part of dissolved oxygen removed enters a subsequent regeneration unit to perform cyclic regeneration and use. Through the method, the introduction of chlorine ions and oxygen in a flue gas CO2 alcohol amine capture system can be reduced, the oxidative degradation of the alcohol amine absorbent can be delayed, the corrosiveness of the amine liquid can be reduced, and the long-period operation of the device is ensured.

Description

Technical Field

[0001] This invention belongs to the field of gas purification technology, specifically relating to a method and system for reducing the corrosiveness of CO2 absorbents in flue gas. Background Technology

[0002] Alkylamines are currently the most widely used gas purification agents in the petrochemical and natural gas industries, mainly including monoethanolamine, diethanolamine, diisopropanolamine, and methyldiethanolamine. However, amine absorbents inevitably undergo oxidative degradation during use, producing products such as carboxylic acids, amino acids, amides, amines, aldehydes, and ammonia. Some of these products form salts with the amines, which, because they cannot release the amines during regeneration, are called heat-stable salts. The accumulation of heat-stable salts in amine process systems leads to a series of problems, including decreased purification efficiency, solution foaming, and equipment corrosion. Common methods to inhibit the oxidative degradation of amine solutions include adding oxidation inhibitors, such as sulfites. However, the introduction of salts exacerbates foaming of the amine solution, leading to increased energy consumption. Therefore, to reduce the corrosiveness of the amine solution and ensure long-term operation of the equipment, it is necessary to reduce the oxygen introduction into the flue gas CO2 capture system.

[0003] Chinese Patent Application No. 202310748073.8 discloses a flue gas deoxygenation device and method. The deoxygenation device includes a deoxygenation reactor; the inlet of the deoxygenation reactor is connected to a combustion furnace, and the outlet of the deoxygenation reactor is connected to a pyrolysis device. High-temperature flue gas generated during combustion furnace operation enters the deoxygenation reactor, which converts oxygen in the high-temperature flue gas into carbon dioxide. The carbon dioxide then enters the pyrolysis device with the high-temperature flue gas and mixes with oil-based rock cuttings in a fluidized state for heat transfer. The deoxygenation reactor in this flue gas deoxygenation device is located between the combustion furnace and the pyrolysis device. The deoxygenation reactor can recover and reuse the high-temperature flue gas generated by the combustion furnace and reduce the oxygen content in the high-temperature flue gas, allowing the high-temperature flue gas to be directly used as a heat carrier in the fluidized bed pyrolysis process of oil-based rock cuttings. This reduces the cost of preparing oxygen-free high-temperature flue gas, thereby effectively reducing the cost of the fluidized bed pyrolysis process of oil-based rock cuttings. However, this device and method primarily address the high-temperature flue gas generated during combustion furnace operation, with flue gas temperatures reaching 800-1100℃, which falls under the category of high-temperature deoxygenation. Its effectiveness on desulfurized flue gas remains to be seen. Currently, there are relatively few reports on low-temperature deoxygenation technologies for flue gas. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method and system for reducing the corrosiveness of CO2 amine absorbents in flue gas, which can effectively remove HCl and oxygen from flue gas, and simultaneously effectively remove dissolved oxygen from amine solutions.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for reducing the corrosiveness of CO2 absorbents in flue gas includes the following steps:

[0007] The desulfurization flue gas enters the bottom of the integrated tower via the first induced draft fan. After passing through the gas distributor, it comes into counter-current contact with the first absorbent, resulting in preliminary desulfurization. Subsequently, the pre-desulfurized flue gas passes through the first gas riser cap and comes into counter-current contact with the second absorbent in the first packing section, resulting in secondary desulfurization. Then, the secondary desulfurized flue gas passes through the second gas riser cap and comes into counter-current contact with the third absorbent in the second packing section, resulting in tertiary desulfurization. The tertiary desulfurized flue gas then exits the integrated tower via the demister and enters the dehumidification and deoxygenation tower to obtain pretreated flue gas. The pretreated flue gas enters the absorption tower via the second induced draft fan for CO2 capture. After capture, the purified flue gas is discharged from the top of the absorption tower, and the amine-rich liquid discharged from the bottom of the absorption tower enters the dissolved oxygen removal device to remove dissolved oxygen. The amine-rich liquid with partially dissolved oxygen removed enters the subsequent regeneration unit for recycling and reuse.

[0008] Preferably, the first absorbent is tap water, which circulates at the bottom of the integrated tower, and its pH value is controlled between 5 and 7.

[0009] Preferably, the second absorbent is a salt solution of one or more of NaHCO3, KHCO3, Ca(HCO3)2, and NH4HCO3, with a mass concentration of 0.1-10% and a pH value controlled at 7-9.

[0010] Preferably, the third absorbent is a salt solution of one or more of Na2SO3, NaHSO3, K2SO3, and KHSO3, with a mass concentration of 0.1-10% and a pH value controlled at 7-9.

[0011] Preferably, the bed in the dehumidification and deoxygenation tower is a molecular sieve loaded with FeO, and the loading of the active component FeO is 0.5-15 wt%.

[0012] Preferably, the dissolved oxygen removal device is a tubular membrane gas-liquid contactor, with the tube-side medium being amine-rich liquid and the shell-side medium being gas, and the shell-side pressure controlled at 0.1-0.5 kPa.

[0013] Preferably, the membrane module in the dissolved oxygen removal device is made of one of hollow polyethylene fiber, hollow polypropylene fiber or hollow polyvinylidene fluoride fiber, and the membrane module has a porosity of 20-25% and a pore size range of 20-50 nm.

[0014] A system for implementing the method of reducing the corrosivity of CO2 amine absorbent in flue gas includes a combined tower, a dehumidification and deoxygenation tower, an absorption tower, and a dissolved oxygen removal device connected in sequence. The combined tower is provided with a gas distributor, a first gas rising cap, a first packing section, a second gas rising cap, a second packing section, and a demister in sequence from top to bottom.

[0015] Preferably, a first spray distributor is provided between the gas distributor and the first gas rising cap, a second spray distributor is provided between the first packing section and the second gas rising cap, and a third spray distributor is provided between the second packing section and the demister.

[0016] Preferably, a second induced draft fan is provided between the dehumidification and deoxygenation tower and the absorption tower, and two dehumidification and deoxygenation towers are arranged side by side.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The method for reducing the corrosiveness of CO2 amine absorbents in flue gas provided by this invention involves three treatments of the desulfurized flue gas within a combined treatment tower. First, the desulfurized flue gas is contacted with a first absorbent, primarily water, to dissolve acidic gases and initially remove acidic gases (HCl, SO2, NO2) and solid particles from the flue gas. Subsequently, it is contacted with a second absorbent, a carbonate solution, which reacts with the acidic gases in the flue gas to further remove them and prevent the acidic gases from affecting the flue gas. The process involves pre-treating the flue gas with a third absorbent to enhance its adsorption efficiency. The flue gas then comes into contact with this third absorbent, a sulfite solution that reacts with oxygen in the flue gas, initially removing O2. Next, the flue gas is introduced into a dehumidification and deoxygenation tower for further removal of O2 and H2O. Finally, the flue gas enters an absorption tower where amine solution captures CO2. The purified flue gas exits the absorption tower, while the amine solution undergoes dissolved oxygen removal and is subsequently recycled. This pre-treatment removes most of the oxygen and hydrogen chloride, while also removing dissolved oxygen from the amine solution. This slows down the oxidative degradation of the amine absorbent, reduces amine consumption, lowers the corrosiveness of the amine solution, reduces equipment maintenance and repair costs, ensures long-term operation of the equipment, and extends its service life. The flue gas treated by this method has already undergone denitrification and desulfurization unit treatment, reducing the temperature to 40-50℃. The temperature of the sprayed absorbent is at room temperature, and the entire process is essentially carried out at room temperature, reducing energy consumption. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a system for reducing the corrosiveness of CO2 absorbents in flue gas according to the present invention.

[0020] In the diagram, 1. First induced draft fan; 2. Gas distributor; 3. First spray distributor; 4. First gas riser cap; 5. First packing section; 6. Second spray distributor; 7. Second gas riser cap; 8. Second packing section; 9. Third spray distributor; 10. Integrated tower; 11. Demister; 12. Dehumidification and deoxygenation tower; 13. Second induced draft fan; 14. Absorption tower; 15. Dissolved oxygen removal device. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1

[0023] A system for reducing the corrosiveness of CO2 amine absorbent in flue gas includes a combined tower 10, a dehumidification and deoxygenation tower 12, an absorption tower 14, and a dissolved oxygen removal device 15 connected in sequence. The combined tower 10 is provided with a gas distributor 2, a first gas rising cap 4, a first packing section 5, a second gas rising cap 7, a second packing section 8, and a demister 11 arranged in sequence from top to bottom.

[0024] In this embodiment, a first spray distributor 3 is provided between the gas distributor 2 and the first gas rising cap 4, a second spray distributor 6 is provided between the first packing section 5 and the second gas rising cap 7, and a third spray distributor 9 is provided between the second packing section 8 and the demister 11.

[0025] In this embodiment, a second induced draft fan 13 is provided between the dehumidification and deoxygenation tower 12 and the absorption tower 14. Two dehumidification and deoxygenation towers 12 are arranged side by side, one in operation and one on standby.

[0026] Example 2

[0027] A method for reducing the corrosiveness of CO2 absorbents in flue gas includes the following steps:

[0028] The desulfurization flue gas enters the bottom of the integrated tower 10 via the first induced draft fan 1. After passing through the gas distributor 2, it comes into counter-current contact with the first absorbent sprayed from the first spray distributor 3, initially removing acidic gases (HCl, SO2, NO2) and solid particles from the flue gas, resulting in preliminarily desulfurized flue gas. Subsequently, the preliminarily desulfurized flue gas passes through the first gas riser 4 and comes into counter-current contact with the second absorbent sprayed from the second spray distributor 6 in the first packing section 5, further removing acidic gases, resulting in secondary desulfurized flue gas. Then, the secondary desulfurized flue gas passes through the second gas riser 7 and comes into contact with the third absorbent sprayed from the third spray distributor 9 in the second... The packing section 8 is in counter-current contact, initially removing O2 from the flue gas to obtain tertiary de-treated flue gas. Then, the tertiary de-treated flue gas passes through the demister 11 and exits the integrated tower 10 into the dehumidification and deoxygenation tower 12 to further remove O2 and H2O from the flue gas, resulting in pretreated flue gas. The pretreated flue gas enters the absorption tower 14 through the second induced draft fan 13 for CO2 capture. After capture, the purified flue gas is discharged from the top of the absorption tower 14, and the rich amine liquid discharged from the bottom of the absorption tower 14 enters the dissolved oxygen removal device 15 to remove dissolved oxygen from the rich amine liquid. The rich amine liquid with some dissolved oxygen removed enters the subsequent regeneration unit for recycling and reuse.

[0029] In this embodiment, the first absorbent is water, which circulates at the bottom of the integrated tower, and its pH value is controlled at 6.

[0030] In this embodiment, the second absorbent is a NaHCO3 salt solution, which is recycled and has a mass concentration of 4% and a pH value controlled at 8.

[0031] In this embodiment, the third absorbent is a Na2SO3 salt solution, which is recycled and has a mass concentration of 3% and a pH value controlled at 8.

[0032] In this embodiment, the bed in the dehumidification and deoxygenation tower 12 is a molecular sieve loaded with FeO, and the loading of the active component FeO is 2wt%.

[0033] In this embodiment, the dissolved oxygen removal device 15 is a tubular membrane gas-liquid contactor, with the tube-side medium being amine-rich liquid and the shell-side medium being gas, and the shell-side space pressure being controlled at 0.5 kPa.

[0034] In this embodiment, the membrane module in the dissolved oxygen removal device is made of hollow polyethylene fiber, with a porosity of 20% and a pore size range of 20-50 nm.

[0035] The dissolved oxygen concentration of the amine solution exiting the absorption tower 12 was measured to be 26 mg / L, and the dissolved oxygen concentration of the amine solution exiting the dissolved oxygen removal device 15 was 12 mg / L.

[0036] Example 3

[0037] A method for reducing the corrosiveness of CO2 absorbents in flue gas includes the following steps:

[0038] The desulfurization flue gas enters the bottom of the integrated tower 10 via the first induced draft fan 1. After passing through the gas distributor 2, it comes into counter-current contact with the first absorbent sprayed from the first spray distributor 3, initially removing acidic gases (HCl, SO2, NO2) and solid particles from the flue gas, resulting in preliminarily desulfurized flue gas. Subsequently, the preliminarily desulfurized flue gas passes through the first gas riser 4 and comes into counter-current contact with the second absorbent sprayed from the second spray distributor 6 in the first packing section 5, further removing acidic gases, resulting in secondary desulfurized flue gas. Then, the secondary desulfurized flue gas passes through the second gas riser 7 and comes into contact with the third absorbent sprayed from the third spray distributor 9 in the second... The packing section 8 is in counter-current contact, initially removing O2 from the flue gas to obtain tertiary de-treated flue gas. Then, the tertiary de-treated flue gas passes through the demister 11 and exits the integrated tower 10 into the dehumidification and deoxygenation tower 12 to further remove O2 and H2O from the flue gas, resulting in pretreated flue gas. The pretreated flue gas enters the absorption tower 14 through the second induced draft fan 13 for CO2 capture. After capture, the purified flue gas is discharged from the top of the absorption tower 14, and the rich amine liquid discharged from the bottom of the absorption tower 14 enters the dissolved oxygen removal device 15 to remove dissolved oxygen from the rich amine liquid. The rich amine liquid with some dissolved oxygen removed enters the subsequent regeneration unit for recycling and reuse.

[0039] In this embodiment, the first absorbent is water, which circulates at the bottom of the integrated tower, and its pH value is controlled at 6.

[0040] In this embodiment, the second absorbent is a NaHCO3 salt solution, which is recycled and has a mass concentration of 4% and a pH value controlled at 8.

[0041] In this embodiment, the third absorbent is a Na2SO3 salt solution, which is recycled and has a mass concentration of 3% and a pH value controlled at 8.

[0042] In this embodiment, the bed in the dehumidification and deoxygenation tower 12 is a molecular sieve loaded with FeO, and the loading of the active component FeO is 5wt%.

[0043] In this embodiment, the dissolved oxygen removal device 15 is a tubular membrane gas-liquid contactor, with the tube-side medium being amine-rich liquid and the shell-side medium being gas, and the shell-side space pressure being controlled at 0.5 kPa.

[0044] In this embodiment, the membrane module in the dissolved oxygen removal device is made of hollow polyethylene fiber, with a porosity of 20% and a pore size range of 20-50 nm.

[0045] The dissolved oxygen concentration of the amine solution exiting the absorption tower 12 was measured to be 25.2 mg / L, and the dissolved oxygen concentration of the amine solution exiting the dissolved oxygen removal device 15 was 9.5 mg / L.

[0046] Example 4

[0047] A method for reducing the corrosiveness of CO2 absorbents in flue gas includes the following steps:

[0048] The desulfurization flue gas enters the bottom of the integrated tower 10 via the first induced draft fan 1. After passing through the gas distributor 2, it comes into counter-current contact with the first absorbent sprayed from the first spray distributor 3, initially removing acidic gases (HCl, SO2, NO2) and solid particles from the flue gas, resulting in preliminarily desulfurized flue gas. Subsequently, the preliminarily desulfurized flue gas passes through the first gas riser 4 and comes into counter-current contact with the second absorbent sprayed from the second spray distributor 6 in the first packing section 5, further removing acidic gases, resulting in secondary desulfurized flue gas. Then, the secondary desulfurized flue gas passes through the second gas riser 7 and comes into contact with the third absorbent sprayed from the third spray distributor 9 in the second... The packing section 8 is in counter-current contact, initially removing O2 from the flue gas to obtain tertiary de-treated flue gas. Then, the tertiary de-treated flue gas passes through the demister 11 and exits the integrated tower 10 into the dehumidification and deoxygenation tower 12 to further remove O2 and H2O from the flue gas, resulting in pretreated flue gas. The pretreated flue gas enters the absorption tower 14 through the second induced draft fan 13 for CO2 capture. After capture, the purified flue gas is discharged from the top of the absorption tower 14, and the rich amine liquid discharged from the bottom of the absorption tower 14 enters the dissolved oxygen removal device 15 to remove dissolved oxygen from the rich amine liquid. The rich amine liquid with some dissolved oxygen removed enters the subsequent regeneration unit for recycling and reuse.

[0049] In this embodiment, the first absorbent is water, which circulates at the bottom of the integrated tower, and its pH value is controlled at 6.

[0050] In this embodiment, the second absorbent is a NaHCO3 salt solution, which is recycled and has a mass concentration of 4% and a pH value controlled at 8.

[0051] In this embodiment, the third absorbent is a Na2SO3 salt solution, which is recycled and has a mass concentration of 3% and a pH value controlled at 8.

[0052] In this embodiment, the bed in the dehumidification and deoxygenation tower 12 is a molecular sieve loaded with FeO, and the loading of the active component FeO is 2wt%.

[0053] In this embodiment, the dissolved oxygen removal device 15 is a tubular membrane gas-liquid contactor, with the tube-side medium being amine-rich liquid and the shell-side medium being gas, and the shell-side space pressure being controlled at 0.5 kPa.

[0054] In this embodiment, the membrane module in the dissolved oxygen removal device is made of hollow polyethylene fiber, with a porosity of 25% and a pore size range of 20-50 nm.

[0055] The dissolved oxygen concentration of the amine solution exiting the absorption tower 12 was measured to be 26.6 mg / L, and the dissolved oxygen concentration of the amine solution exiting the dissolved oxygen removal device 15 was 14.5 mg / L.

[0056] Comparative Example 1

[0057] The desulfurized flue gas is directly fed into the absorption tower 12 via the second induced draft fan 11 for CO2 capture. After capture, the purified flue gas is discharged from the top of the absorption tower 12, and the rich amine liquid discharged from the bottom of the absorption tower 12 enters the dissolved oxygen removal device 13 to remove dissolved oxygen from the rich amine liquid. The rich amine liquid with some dissolved oxygen removed enters the subsequent regeneration unit for recycling and reuse.

[0058] In this comparative example, the dissolved oxygen removal device 15 is a tubular membrane gas-liquid contactor, with the tube-side medium being amine-rich liquid and the shell-side medium being gas, and the shell-side space pressure being controlled at 0.5 kPa.

[0059] In this comparative example, the membrane module in the dissolved oxygen removal device is made of hollow polyethylene fiber, with a porosity of 20% and a pore size range of 20-50 nm.

[0060] The dissolved oxygen concentration of the amine solution exiting the absorption tower 12 was measured to be 41.3 mg / L, and the dissolved oxygen concentration of the amine solution exiting the dissolved oxygen removal device 15 was 26 mg / L.

[0061] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for reducing the corrosiveness of an alcohol amine absorbent for CO2 in flue gas, characterized in that, Includes the following steps: The desulfurized flue gas enters the bottom of the integrated tower (10) through the first induced draft fan (1), and after passing through the gas distributor (2), it comes into countercurrent contact with the first absorbent to obtain preliminary desulfurized flue gas; then the preliminary desulfurized flue gas passes through the first gas riser cap (4) and comes into countercurrent contact with the second absorbent in the first packing section (5) to obtain secondary desulfurized flue gas; then the secondary desulfurized flue gas passes through the second gas riser cap (7) and comes into countercurrent contact with the third absorbent in the second packing section (8) to obtain tertiary desulfurized flue gas; then the tertiary desulfurized flue gas exits the integrated tower (10) through the demister (11) and enters the dehumidification and deoxygenation tower (12) to obtain pretreated flue gas; The pretreated flue gas enters the absorption tower (14) via the second induced draft fan (13) for CO2 capture. After capture, the purified flue gas is discharged from the top of the absorption tower (14), and the rich amine liquid discharged from the bottom of the absorption tower (14) enters the dissolved oxygen removal device (15) to remove dissolved oxygen from the rich amine liquid. The rich amine liquid with some dissolved oxygen removed enters the subsequent regeneration unit for recycling and reuse. The first absorbent is water, which circulates at the bottom of the integrated tower, and its pH value is controlled at 5-7. The second absorbent is a salt solution of one or more of NaHCO3, KHCO3, Ca(HCO3)2, and NH4HCO3, with a mass concentration of 0.1-10% and a pH value controlled at 7-9; The third absorbent is a salt solution of one or more of Na2SO3, NaHSO3, K2SO3, and KHSO3, with a mass concentration of 0.1-10% and a pH value controlled at 7-9. The bed in the dehumidification and deoxygenation tower (12) is a molecular sieve loaded with FeO, and the loading of the active component FeO is 0.5-15wt%.

2. The method for reducing the corrosiveness of an alcohol amine absorbent for CO2 in flue gas according to claim 1, characterized in that, The dissolved oxygen removal device (15) is a tubular membrane gas-liquid contactor, with the tube-side medium being amine-rich liquid and the shell-side medium being gas, and the shell-side space pressure being controlled at 0.1-0.5 kPa.

3. The method for reducing the corrosiveness of CO2 absorbent in flue gas according to claim 2, characterized in that, The membrane module in the dissolved oxygen removal device is made of one of hollow polyethylene fiber, hollow polypropylene fiber or hollow polyvinylidene fluoride fiber, and the membrane module has a porosity of 20-25% and a pore size range of 20-50 nm.

4. The method for reducing the corrosiveness of CO2 absorbent in flue gas according to claim 1, characterized in that, The system for implementing the method of reducing the corrosivity of CO2 amine absorbent in flue gas includes a combined tower (10), a dehumidification and deoxygenation tower (12), an absorption tower (14), and a dissolved oxygen removal device (15) connected in sequence. The combined tower (10) is provided with a gas distributor (2), a first gas rising cap (4), a first packing section (5), a second gas rising cap (7), a second packing section (8), and a demister (11) in sequence from top to bottom.

5. The method for reducing the corrosiveness of an alcohol amine absorbent for CO2 in flue gas according to claim 4, characterized in that, A first spray distributor (3) is provided between the gas distributor (2) and the first gas rising cap (4), a second spray distributor (6) is provided between the first packing section (5) and the second gas rising cap (7), and a third spray distributor (9) is provided between the second packing section (8) and the demister (11).

6. The method for reducing the corrosiveness of an alcohol amine absorbent for CO2 in flue gas according to claim 4, characterized in that, A second induced draft fan (13) is provided between the dehumidification and deoxygenation tower (12) and the absorption tower (14), and two dehumidification and deoxygenation towers (12) are arranged side by side.

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