Flue gas decarburization absorbent and decarburization method

Abstract

The invention provides a flue gas decarbonization absorbent which comprises the following components in percentage by weight: 5wt%-45wt% of a main absorption component which is selected from a dihydroxy alkyl piperazine compound; 2 wt% to 40 wt% of an activator; 0 wt% to 5 wt% of an antifoaming agent; 0 wt% to 5 wt% of an antioxidant; and 20 wt%-80 wt% of water. The flue gas decarburization absorbent provided by the invention has good stability and can give consideration to both absorption and desorption performance. The decarburizing agent provided by the invention can remove and recover carbon dioxide in mixed gases such as limestone rotary kiln flue gas, blast furnace gas, natural gas, power plant boiler flue gas, blast furnace hot blast stove flue gas, coke oven flue gas and the like, and has the advantages of high desorption rate of carbon dioxide in flue gas, low regeneration energy consumption, low volatility and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of gas separation and purification, and in particular relates to a flue gas decarbonization absorbent and a decarbonization method. Background Art

[0002] Global warming is one of the major challenges facing human society. Excessive carbon dioxide emissions have been widely recognized as one of the most important sources of global climate change. In order to reduce CO2 emissions, it is imperative to develop economical, efficient and large-scale CO2 capture technology. At present, there are mainly adsorption, chemical absorption, membrane absorption, low-temperature fractionation and other methods for absorbing carbon dioxide. The chemical absorption method using chemical solvents is considered to be the most effective method for capturing CO2 after combustion. Organic amine solutions are commonly used absorbents, mainly ethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA) and methyldiethanolamine (MDEA), AEEA (hydroxyethylethylenediamine) and DETA (diethylenetriamine). Among them, MEA has the advantages of fast absorption rate, high absorption capacity and low viscosity, but its regeneration energy consumption is high and it is easy to degrade. The CO2 absorption capacity of DEA solution is low, and the CO2 absorption rate of TEA and MDEA is relatively slow. Polyamines such as AEEA and DETA also have shortcomings such as high viscosity and slow regeneration rate.

[0003] Research has found that piperazine organic amines have advantages over ethylenediamine and alcohol amines, such as high boiling point, less solvent loss, and less corrosion to equipment. However, the main problems of organic amine carbon dioxide capture technology are still the large loss of flue gas decarbonization absorbent and high desorption energy consumption. The development of low volatility, low desorption energy consumption and efficient carbon dioxide absorption absorbent has always been a difficulty and hot spot in the research of carbon dioxide capture process technology.

[0004] The main components of the existing flue gas decarbonization absorbents, such as monoethanolamine, piperazine, and diazabicyclooctane, have relatively low boiling points (148.5°C to 174°C). During the solution regeneration process, they are highly volatile and have a large loss, resulting in poor stability of the decarbonization solution, which in turn affects the stability of the decarbonization system. Although diethanolamine has a high boiling point, it is easily oxidized and degraded. It has high alkalinity and a strong binding force with carbon dioxide, requiring a relatively high desorption energy consumption. Activators such as diethylenetriamine and tetraethylenepentamine synergistically improve the removal effect of carbon dioxide with main absorbents such as diazabicyclooctane, but there are shortcomings such as low desorption efficiency of the flue gas decarbonization absorbent. In addition, straight-chain organic amines such as diethylenetriamine have the disadvantages of being easily oxidized and having poor stability.

[0005] Therefore, it becomes a problem to be solved to provide a flue gas absorbent that can take into account both absorption and analysis performance, reduce flue gas decarbonization escape, and has low treatment energy consumption. Summary of the invention

[0006] In view of this, the technical problem to be solved by the present invention is to provide a flue gas decarbonization absorbent and a decarbonization method. The flue gas decarbonization absorbent provided by the present invention can take into account both absorption and analysis performance, reduce flue gas decarbonization escape, and has low processing energy consumption.

[0007] The present invention provides a flue gas decarbonization absorbent, comprising:

[0008] 5wt% to 45wt% of a main absorption component, wherein the main absorption component is selected from bishydroxyalkyl piperazine compounds;

[0009] 2wt% to 40wt% of an activator, wherein the activator is selected from a mixture of piperazine and monohydroxyalkyl piperazine compounds;

[0010] 0wt% to 5wt% of a defoaming agent;

[0011] 0wt% to 5wt% of an antioxidant;

[0012] 20wt% to 80wt% water.

[0013] Preferably, the bishydroxyalkyl piperazine compound is selected from one or more of N,N-di-(2-hydroxyethyl) piperazine, N,N-di-(3-hydroxypropyl) piperazine, and N-2-hydroxyethyl-N-3-hydroxypropyl piperazine.

[0014] Preferably, the monohydroxyalkyl piperazine compound is one of N-2-hydroxyethyl piperazine and N-3-hydroxypropyl piperazine or a mixture thereof, and the mass ratio of piperazine to the monohydroxyalkyl piperazine compound is 1:0.1-10.

[0015] Preferably, the defoaming agent is one or more of polyoxypropylene oxyethylene glycerol ether, polydimethylsiloxane, and ethylene glycol siloxane.

[0016] Preferably, the antioxidant is one or more of 2,6-di-tert-butyl-p-cresol, 4-tert-butylcatechol, dodecyl hydroquinone, and p-hydroxyphenol.

[0017] Preferably, the pH of the flue gas decarbonization absorbent is 8-12.

[0018] The present invention also provides a method for preparing the above flue gas decarbonization absorbent, comprising the following steps:

[0019] The main absorption component, the activator, the defoamer, the antioxidant and water are mixed to obtain the flue gas decarbonization absorbent.

[0020] The present invention also provides a system for cyclically removing carbon dioxide from flue gas, comprising: a carbon dioxide flue gas distribution device (2), a carbon dioxide absorption device (3), a regeneration tower (9), a heat exchange system and a control system;

[0021] The carbon dioxide absorption device (3) is provided with a flue gas decarbonization absorbent according to any one of claims 1 to 6;

[0022] An acid gas extraction device (13) is provided at the top of the regeneration tower (9).

[0023] The present invention also provides a method for cyclically removing carbon dioxide from flue gas, including absorption of carbon dioxide, analysis of carbon dioxide, recycling of flue gas decarbonization absorbent and capture and recovery of decarbonization absorbent in flue gas, wherein the carbon dioxide is absorbed by the flue gas decarbonization absorbent.

[0024] The present invention also provides a method for cyclically removing carbon dioxide from flue gas, comprising the following steps:

[0025] (1) Carbon dioxide absorption: The flue gas to be treated containing carbon dioxide is absorbed by a flue gas decarbonization absorbent at 20 to 60°C to obtain a rich liquid and purified flue gas;

[0026] (2) Carbon dioxide desorption: The rich liquid is heated to 80-100°C and enters the regeneration tower for desorption. The top pressure of the regeneration tower is controlled to be -10-60 kPa. Carbon dioxide gas and lean liquid are obtained by desorption and regeneration.

[0027] (3) Recycling of flue gas decarbonization absorbent: the lean liquid obtained in step (2) is used as a flue gas decarbonization absorbent in step (1) after heat exchange cooling;

[0028] (4) Capture and recovery of decarbonizing agent in flue gas: The flue gas obtained after purification in step (1) is washed with desalted water in the decarbonizing agent recovery tower (3-2) at the top of the carbon dioxide absorption device (3), and the washing liquid is used for the preparation of flue gas decarbonizing agent or added to the lean liquid of step (3).

[0029] Compared with the prior art, the present invention provides a flue gas decarbonization absorbent, comprising: 5wt% to 45wt% of a main absorption component, wherein the main absorption component is selected from dihydroxyalkyl piperazine compounds; 2wt% to 40wt% of an activator; 0wt% to 5wt% of a defoamer; 0wt% to 5wt% of an antioxidant; and 20wt% to 80wt% of water. The flue gas decarbonization absorbent provided by the present invention has good stability and can take into account both absorption and analytical performance. The decarbonization agent provided by the present invention can remove and recover carbon dioxide from mixed gases such as limestone rotary kiln flue gas, blast furnace gas, natural gas, power plant boiler flue gas, blast furnace hot blast furnace flue gas, and coke oven flue gas. The flue gas decarbonization agent has the advantages of a large desorption rate of carbon dioxide in flue gas, low regeneration energy consumption, and low volatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1A schematic diagram of the structure of the system for cyclically removing carbon dioxide from flue gas provided by the present invention.

[0031] Figure markings: 1-boosting fan, 2-gas distribution device, 3-1-CO2 absorption tower, 3-2-decarbonizer recovery tower, 4-rich liquid tank, 5-recovery liquid tank, 6-lean and rich liquid heat exchanger, 7-lean liquid recooler, 8-rich liquid reheater, 9-regeneration tower, 10-reboiler, 11-acid gas condenser, 12-gas-liquid separator, 13-acid gas extraction device, 14-oil bath heating device, p1~p4-liquid pumps. DETAILED DESCRIPTION

[0032] The present invention provides a flue gas decarbonization absorbent, comprising:

[0033] 5wt% to 45wt% of a main absorption component, wherein the main absorption component is selected from bishydroxyalkyl piperazine compounds;

[0034] 2wt% to 40wt% of an activator, wherein the activator is selected from a mixture of piperazine and monohydroxyalkyl piperazine compounds;

[0035] 0wt% to 5wt% of a defoaming agent;

[0036] 0wt% to 5wt% of an antioxidant;

[0037] 20wt% to 80wt% water.

[0038] The flue gas decarbonization absorbent provided by the present invention includes 5wt% to 45wt% of the main absorption component, which can be 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, or any value between 5wt% and 45wt%, preferably 10wt% to 40wt%, and more preferably 15wt% to 35wt%. The main absorption component is selected from bishydroxyalkyl piperazine compounds. Preferably, the bishydroxyalkyl piperazine compounds are selected from one or more of N, N-di-(2-hydroxyethyl) piperazine, N, N-di-(3-hydroxypropyl) piperazine, and N-2-hydroxyethyl-N-3-hydroxypropyl piperazine. Further preferably, the bishydroxyalkyl piperazine compounds are selected from N, N-di-(2-hydroxyethyl) piperazine, N, N-di-(3-hydroxypropyl) piperazine or N-2-hydroxyethyl-N-3-hydroxypropyl piperazine.

[0039] The flue gas decarbonization absorbent provided by the present invention also includes 2wt% to 40wt% of an activator, which can be 2wt%, 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, or any value between 2wt% and 40wt%. The activator is selected from a mixture of piperazine and a monohydroxyalkyl piperazine compound, wherein the mass ratio of piperazine to the monohydroxyalkyl piperazine compound is 1:0.1 to 10, which can be 1:0.1, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, or any value between 1:0.1 and 10. The weight fraction of the secondary amine is preferably 10 to 40%, and more preferably 15 to 35%. The monohydroxyalkyl piperazine compound is one of N-2-hydroxyethyl piperazine and N-3-hydroxypropyl piperazine or a mixture thereof, preferably N-2-hydroxyethyl piperazine or N-3-hydroxypropyl piperazine.

[0040] The flue gas decarbonization absorbent provided by the present invention also includes 0wt% to 5wt% of a defoamer, which can be 0wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, or any value between 0wt% and 5wt%. The defoamer is one or more of polyoxypropylene oxyethylene glycerol ether, polydimethylsiloxane, and ethylene glycol siloxane.

[0041] The flue gas decarbonization absorbent provided by the present invention also includes 0wt% to 5wt% of an antioxidant, which can be 0wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, or any value between 0wt% and 5wt%. The antioxidant is one or more of 2,6-di-tert-butyl-p-cresol, 4-tert-butyl-catechol, dodecyl hydroquinone, and p-hydroxyphenol.

[0042] The flue gas decarbonization absorbent provided by the present invention also includes 20wt% to 80wt% of water, which may be 20wt%, 30wt%, 40wt%, 50wt%, 60wt%, 70wt%, 80wt%, or any value between 20wt% and 80wt%.

[0043] The pH value of the flue gas decarbonization absorbent of the present invention is 8-12, and can be 8, 9, 10, 11, 12, or any value between 8 and 12.

[0044] In the present invention, the decarbonization absorbent formed by the tertiary amine and the secondary amine, the tertiary amine is present in the solution, the protonated secondary amine and the tertiary amine are in balance with each other, further catalyzing the reaction of CO2 with water to form tertiary amine bicarbonate, the presence of the tertiary amine at high temperature promotes the hydrolysis of the tertiary amine bicarbonate, and improves the desorption performance of the decarbonization agent.

[0045] The main absorbent of the present invention contains two hydroxyl groups, has good water solubility and low vapor pressure, contains two amine groups, and tertiary amines have higher CO2 absorption capacity than secondary amines, and have larger absorption capacity. This is because primary amines and secondary amines tend to carbamates, in which 1 mole of CO2 consumes 2 moles of amines. The principle of absorbing CO2 is as follows:

[0046] CO2+H2O→H2CO3 1-1

[0047] H2CO3→HCO3 - +H + 1-2

[0048] CO2+H2O→HCO3 - +H + 1-3

[0049] HCO3 - →H + +CO3 2- 1-4

[0050] CO2+H2O+NR3R4R5→R3R4R5NH + +HCO3 - 1-5

[0051] The tertiary amine does not contain a hydrogen atom on its N atom and does not form a stable carbamate. It only acts as a buffer to react with the H formed in reaction 1-3. + The amine salt of bicarbonate produces CO2 in a 1:1 ratio with the amine, so it is more effective than primary and secondary amines to reach higher loads. Since the reaction of CO2 dissolving in water in reaction 1-1 is limited, the mass transfer rate of the aqueous solution in the tertiary amine CO2 decarbonization absorbent is also limited. This requires additional reaction catalysts to eliminate or weaken the impact of the limited mass transfer rate of tertiary amines and CO2, and secondary amines are a very advantageous catalyst for increasing the mass transfer rate of CO2. There are 1 or 2 H atoms on the N atoms of secondary and primary amines, and their steric hindered structures are more conducive to the reaction of primary or secondary amines with CO2 to form carbamates, see reaction 1-6.

[0052] 2R1R2NH+CO2→R1R2N CO3 2- H2N + R1R2 1-6

[0053] The strength of the binding force of the N atom to form the carbamate bond is in the order of primary amine > secondary amine > tertiary amine. The carbamate on the primary amine is more stable than that on the secondary amine and is difficult to hydrolyze. The carbamate on the secondary amine is hydrolyzed into bicarbonate and protonated amine, see reaction 1-7.

[0054] R1R2N CO3 2- H2N + R1R2+H2O→R1R2NH2 + +HCO3 - +R1R2NH 1-7

[0055] The tertiary amine is present in the solution, and the protonated secondary amine and the tertiary amine are in equilibrium with each other, further catalyzing the reaction of CO2 with water and forming tertiary amine bicarbonate, see reaction formula 1-8.

[0056] R1R2NH2 + +NR3R4R5→R1R2NH+R3R4R5NH + 1-8

[0057] The decarbonization absorbent formed by tertiary amine and secondary amine provided by the present invention has a reaction ratio of 1:1 between tertiary amine and CO2, which overcomes the disadvantage that the reaction ratio of primary amine and secondary amine with CO2 is about 2:1. At the same time, the fast mass transfer reaction rate of secondary amine and CO2 is utilized to reduce or eliminate the disadvantage of low mass transfer rate of tertiary amine.

[0058] In addition, in the present invention, the molecular structure of hydroxyalkyl piperazine is a piperazine six-membered ring structure, which can effectively inhibit the chain breaking of the molecule and the polymerization between molecules. The six-membered ring symmetrical structure shows excellent molecular structure stability. The hydroxyalkyl substituents connected to the piperazine molecular skeleton form a steric hindered amine structure, which further improves the water solubility of the molecule, reduces the binding force of the tertiary amine bicarbonate bond, and achieves a lower vapor pressure than the piperazine substance. In particular, the dihydroxyalkyl symmetrical molecular structure on the piperazine molecular skeleton has a higher boiling point, greatly reduces the volatility of its water-soluble substances, reduces the loss of the absorbent in the decarbonization and capture process of the flue gas decarbonization agent, and greatly improves the desorption performance of the carbon capture absorbent.

[0059] The present invention also provides a method for preparing the above flue gas decarbonization absorbent, comprising the following steps:

[0060] The main absorption component, the activator, the defoamer, the antioxidant and water are mixed to obtain the flue gas decarbonization absorbent.

[0061] Specifically, the main absorption component is mixed and stirred with water under heating conditions to dissolve, and the heating temperature is 30-60°C, which can be 30, 40, 50, 60, or any value between 30 and 60°C.

[0062] Then add the activator, stir, and after mixing evenly, add the antioxidant and defoaming component in sequence, then add water to make up the volume, stir evenly to obtain the flue gas decarbonization absorbent.

[0063] The present invention also provides a system for cyclically removing carbon dioxide from flue gas, comprising: a carbon dioxide flue gas distribution device, a carbon dioxide absorption device, a regeneration device, a heat exchange system and a control system.

[0064] For details, see Figure 1 , Figure 1 A schematic diagram of the structure of the system for cyclically removing carbon dioxide from flue gas provided by the present invention.

[0065] The system for cyclically removing carbon dioxide from flue gas provided by the present invention comprises a carbon dioxide flue gas distribution device (2). Preferably, the carbon dioxide flue gas distribution device (2) is connected to a booster fan (1), and the outlet of the booster fan (1) is connected to the inlet of the carbon dioxide flue gas distribution device (2).

[0066] The system for cyclically removing carbon dioxide from flue gas provided by the present invention also includes a carbon dioxide absorption device (3) whose inlet is connected to the outlet of the carbon dioxide flue gas distribution device. The carbon dioxide absorption device (3) includes a CO2 absorption tower (3-1) and a decarbonizing agent recovery tower (3-2). The CO2 absorption tower (3-1) is used to capture carbon dioxide in the flue gas, and the decarbonizing agent recovery tower (3-2) is used to wash, capture and recover the decarbonizing solution entrained in the flue gas after the CO2 flue gas in the CO2 absorption tower (3-1) is removed from the flue gas.

[0067] The flue gas containing carbon dioxide enters the CO2 absorption tower (3-1) through the lower inlet of the carbon dioxide absorption device (3), and the CO2 absorption tower (3-1) is provided with the flue gas decarbonization absorbent mentioned above. The flue gas containing carbon dioxide is captured by the contact reaction with the flue gas decarbonization absorbent.

[0068] A recovery liquid outlet is provided in the decarbonizing agent recovery tower (3-2) of the carbon dioxide absorption device (3), and the recovery liquid outlet is connected to the inlet of the recovery liquid tank (5), and a liquid pump (p2) is provided at the outlet of the recovery liquid tank (5), and the outlet of the liquid pump (p2) is connected to the upper liquid inlet of the carbon dioxide absorption device (3). The carbon dioxide absorption device (3), the recovery liquid tank (5) and the liquid pump (p2) form a loop.

[0069] In the CO2 absorption tower (3-1), the flue gas reacts with the flue gas decarbonization absorbent to capture the CO2 in the flue gas. In the decarbonization agent recovery tower (3-2), the decarbonization solution in the flue gas is captured and recovered. There are liquid cut-off plates, gas lifting hoods and other devices in the middle of the two functional sections of the CO2 absorption tower (3-1) and the decarbonization agent recovery tower (3-2). The captured liquid of the decarbonization agent recovery tower (3-2) is collected separately. After the flue gas is captured and recovered by the decarbonization agent recovery tower (3-2), it is directly discharged.

[0070] The system for cyclically removing carbon dioxide from flue gas provided by the present invention further comprises a rich liquid tank (4) whose inlet is connected to the outlet of the carbon dioxide absorption device, wherein the solution that captures carbon dioxide is called rich liquid.

[0071] The system for cyclically removing carbon dioxide from flue gas provided by the present invention further comprises a lean-rich liquid heat exchanger (6) whose inlet is connected to the outlet of the rich liquid tank. Preferably, a liquid pump (p1) is provided between the rich liquid tank (4) and the lean-rich liquid heat exchanger (6).

[0072] In the present invention, a lean liquid outlet and a rich liquid outlet are provided at the top of the lean-rich liquid heat exchanger (6), wherein the lean liquid outlet is connected to the inlet of the lean liquid subcooler (7), and the outlet of the lean liquid subcooler (7) is connected to the middle inlet of the carbon dioxide absorption device (3).

[0073] The rich liquid outlet is connected to the inlet of the rich liquid reheater (8).

[0074] The system for cyclically removing carbon dioxide from flue gas provided by the present invention further comprises a regeneration tower (9) whose inlet is connected to the outlet of the rich liquid reheater.

[0075] The top outlet of the regeneration tower (9) is connected to the acid gas extraction device (13). Furthermore, the top outlet of the regeneration tower (9) is also connected to the inlet of the acid gas condenser (11), the outlet of the acid gas condenser (11) is connected to the inlet of the gas-liquid separator (12), and the outlet of the gas-liquid separator (12) is connected to the inlet of the upper part of the tower wall of the regeneration tower (9). Preferably, a liquid pump (p4) is provided between the outlet of the gas-liquid separator (12) and the inlet of the upper part of the tower wall of the regeneration tower (9).

[0076] Preferably, a liquid pump (p3) is provided between the outlet at the bottom of the regeneration tower (9) and the bottom inlet of the lean-rich liquid heat exchanger (6).

[0077] The system for cyclically removing carbon dioxide from flue gas provided by the present invention also includes a reboiler (10) whose inlet is connected to the first outlet of the regeneration tower, and the top outlet of the reboiler (10) is connected to the inlet of the lower part of the tower wall of the regeneration tower (9).

[0078] The system for cyclically removing carbon dioxide from flue gas provided by the present invention further comprises an oil bath heating device (14) whose inlet is connected to the outlet at the bottom of the reboiler (10).

[0079] Specifically, the operation process of the equipment includes: the flue gas enters from the bottom of the carbon dioxide absorption device (3), is captured by the flue gas decarbonization absorbent during the contact reaction, the decarbonized flue gas enters the top of the carbon dioxide absorption device (3), is washed with desalted water, and is discharged from the top outlet of the carbon dioxide absorption device (3) after demisting.

[0080] The solution that captures carbon dioxide is called rich liquid. It flows into the rich liquid tank (4) from the bottom of the carbon dioxide absorption device (3), is pumped into the first heat exchanger (lean-rich liquid heat exchanger (6)) by a liquid pump p1, and is sent to the second heat exchanger (rich liquid reheater (8)) after heat exchange. The heated rich liquid is sent to the regeneration tower (9) from the inlet, and is heated in the packing layer with the acid gas rising from the bottom of the regeneration tower (9). It is heated and desorbed. The desorbed rich liquid is sent to the reboiler (10) for heating and desorption. The desorbed lean liquid The liquid and acid gas are returned from the upper part of the reboiler to the bottom of the regeneration tower (9) [a liquid cut-off plate is arranged between the returned high-temperature lean liquid and the high-temperature rich liquid flowing into the reboiler (10), the high-temperature lean liquid flows out from the bottom of the tower, the high-temperature acid gas flows upward from the gas riser hole of the liquid cut-off plate, and contacts and exchanges heat with the high-temperature rich liquid flowing down from the top of the tower in the packing in the opposite direction, and the high-temperature rich liquid after heat exchange flows out from the side of the liquid cut-off plate and enters the upper part of the reboiler (10)], the acid gas rises along the regeneration tower, and the high-temperature lean liquid is sent to the first heat exchanger for heat exchange. The lean liquid after heat exchange is sent to the lean liquid recooler (7), and the lean liquid after cooling is sent to the carbon dioxide absorption device (3) for recycling. The high-temperature acid gas contacts with the second inlet rich liquid and the first inlet acid gas condensate in turn, and is further sent to the acid gas condenser (11) for further cooling, and then separated by the gas-liquid separator (12), and then the acid gas extraction device (13) is used for extraction.

[0081] The exhaust device is used to extract the acid gas from the top of the regeneration tower. A back-pressure valve is arranged between the acid gas outlet at the top of the regeneration tower and the exhaust device. The opening of the back-pressure valve can adjust the pressure at the top of the regeneration tower. When the pressure at the top of the regeneration tower cannot be reduced by adjusting the opening of the back-pressure valve, the exhaust device is used to adjust the pressure at the top of the tower. At the same time, the back-pressure valve and the exhaust device can be used together to adjust the pressure at the top of the regeneration tower.

[0082] The present invention arranges an acid gas extraction device at the top of the regeneration tower, so that the pressure at the top of the tower can be controlled. The pressure is reduced, thereby reducing the temperature of the decarbonizer entering the reboiler, improving the reheating efficiency of the flue gas decarbonization absorbent in the reboiler, and reducing the amount of condensing medium for the high-temperature acid gas.

[0083] The present invention also provides a method for cyclically removing carbon dioxide from flue gas, including absorption of carbon dioxide, analysis of carbon dioxide, recycling of flue gas decarbonization absorbent and capture and recovery of decarbonization absorbent in flue gas, wherein the carbon dioxide is absorbed by the flue gas decarbonization absorbent.

[0084] Specifically, the following steps are included:

[0085] (1) Carbon dioxide absorption: The flue gas to be treated containing carbon dioxide is absorbed by a flue gas decarbonization absorbent at 20 to 60°C to obtain a rich liquid and purified flue gas;

[0086] Among them, the contact pH of the mixture of the flue gas to be treated and the flue gas decarbonization absorbent is 8 to 12, which can be 8, 9, 10, 11, 12, or any value between 8 and 12. The pH variation range is the dynamic pH variation range of the entire contact process between the flue gas to be treated and the absorbent.

[0087] The volume ratio of decarbonization absorbent (lean liquid) to flue gas is 1 to 6 L / Nm 3 , can be 1, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, or 1-6 L / Nm 3 Any value in between.

[0088] (2) Carbon dioxide desorption: The rich liquid is heated to 80-100°C and enters the regeneration tower for desorption. The top pressure of the regeneration tower is controlled to be -10-60 kPa. Carbon dioxide gas and lean liquid are obtained by desorption and regeneration.

[0089] After heating, the temperature of the rich liquid entering the regeneration tower is 85-105°C, which is further optimized to 85-100°C;

[0090] The temperature of the acid vapor at the top of the regeneration tower (9) is in a corresponding relationship with the temperature of the high-temperature lean liquid at the outlet of the reboiler (10).

[0091] When the pressure is 10kpa, the temperature of the high-temperature lean liquid is 100±1℃, and the temperature of the rich liquid entering the tower is 85℃;

[0092] When the pressure is 20kpa, the temperature of the high-temperature lean liquid is 102±1℃, and the temperature of the rich liquid entering the tower is 85℃;

[0093] When the pressure is 40kpa, the temperature of the high-temperature lean liquid is 107±1℃, and the temperature of the rich liquid entering the tower is 85℃.

[0094] Furthermore, the regeneration tower rich liquid is heated by steam or oil bath, preferably by oil bath circulation in a reboiler, with an oil circulation volume of 3.5 to 5 m 3 / h, can be 3.5, 4, 4.5, 5, or 3.5-5m 3 / h, the oil bath temperature is 108-124° C., and can be 108, 110, 112, 115, 117, 120, 122, 124, or any value between 108 and 124° C. Furthermore, an oil temperature measuring device is provided at the inlet and outlet oil pipelines of the reboiler.

[0095] After the high-temperature acid gas obtained in step (2) is condensed, the condensate is returned to the regeneration tower from the top of the regeneration tower, and the obtained purified gas is sent to the acid gas washing tower by a suction device (the device is not in the Figure 1 embodied in the embodiment), washed with desalted water.

[0096] (3) Recycling of flue gas decarbonization absorbent: The lean liquid obtained in step (2) is used as a flue gas decarbonization absorbent in step (1) after heat exchange cooling.

[0097] (4) Capture and recovery of decarbonizing agent in flue gas: The flue gas obtained after purification in step (1) is washed with desalted water in the decarbonizing agent recovery tower (3-2) at the top of the carbon dioxide absorption device (3), and the washing liquid is used for the preparation of flue gas decarbonizing agent or added to the lean liquid of step (3).

[0098] In the present invention, by utilizing the difference in the structures of secondary tertiary amine and tertiary amine, the activator in the flue gas decarbonization absorbent and the main absorption component form a complementary absorption and desorption.

[0099] The escape loss of flue gas decarbonization absorbent in the absorption tower and regeneration tower is evaluated.

[0100] In order to further understand the present invention, the flue gas decarbonization absorbent and the decarbonization method provided by the present invention are described below in conjunction with embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0101] (1) Flue gas parameter conditions

[0102] The composition of the simulated flue gas is (volume): CO2: 10%; O2: 15.5%; H2O: 9.5%; N2: 63.94%, CO: 1.05%; trace amounts of carbides and nitrogen oxides.

[0103] (2) Flue gas circulation absorption process parameters

[0104] Smoke volume is 25m 3 / h, absorption temperature is ~40℃, solution circulation volume is 70L / h, recovery section recovery liquid spray volume is 70L / h, rich liquid preheating temperature entering regeneration tower is 85℃, desorption tower top pressure is 10kpa, oil bath circulation volume is 4.5m 3 / h, the oil bath temperature is 112℃.

[0105] (3) System for cyclic removal of carbon dioxide from flue gas

[0106] The system for cyclically removing carbon dioxide from flue gas provided by the present invention comprises a carbon dioxide flue gas distribution device (2). The carbon dioxide flue gas distribution device (2) is connected to a booster fan (1), and the outlet of the booster fan (1) is connected to the inlet of the carbon dioxide flue gas distribution device (2).

[0107] The system for cyclically removing carbon dioxide from flue gas provided by the present invention also includes a carbon dioxide absorption device (3) whose inlet is connected to the outlet of the carbon dioxide flue gas distribution device. The carbon dioxide absorption device (3) includes a CO2 absorption tower (3-1) and a decarbonizing agent recovery tower (3-2). The CO2 absorption tower (3-1) is used to capture carbon dioxide in the flue gas, and the decarbonizing agent recovery tower (3-2) is used to wash, capture and recover the decarbonizing solution entrained in the flue gas after the CO2 flue gas in the CO2 absorption tower (3-1) is removed from the flue gas. The flue gas containing carbon dioxide enters the CO2 absorption tower (3-1) through the lower inlet of the carbon dioxide absorption device (3), and the CO2 absorption tower (3-1) is provided with a flue gas decarbonizing absorbent, and the flue gas containing carbon dioxide and the flue gas decarbonizing absorbent are captured in a contact reaction.

[0108] A recovery liquid outlet is provided in the decarbonizing agent recovery tower (3-2) of the carbon dioxide absorption device (3), and the recovery liquid outlet is connected to the inlet of the recovery liquid tank (5), and a liquid pump (p2) is provided at the outlet of the recovery liquid tank (5), and the outlet of the liquid pump (p2) is connected to the upper liquid inlet of the carbon dioxide absorption device (3). The carbon dioxide absorption device (3), the recovery liquid tank (5) and the liquid pump (p2) form a loop.

[0109] In the CO2 absorption tower (3-1), the flue gas reacts with the flue gas decarbonization absorbent to capture the CO2 in the flue gas. In the decarbonization agent recovery tower (3-2), the decarbonization solution in the flue gas is captured and recovered. There are liquid cut-off plates, gas lifting hoods and other devices in the middle of the two functional sections of the CO2 absorption tower (3-1) and the decarbonization agent recovery tower (3-2). The captured liquid of the decarbonization agent recovery tower (3-2) is collected separately. After the flue gas is captured and recovered by the decarbonization agent recovery tower (3-2), it is directly discharged.

[0110] The system for cyclically removing carbon dioxide from flue gas provided by the present invention also comprises a rich liquid tank (4) whose inlet is connected to the outlet of the carbon dioxide absorption device.

[0111] The system for cyclically removing carbon dioxide from flue gas provided by the present invention also includes a lean-rich liquid heat exchanger (6) whose inlet is connected to the outlet of the rich liquid tank. A liquid pump (p1) is arranged between the rich liquid tank (4) and the lean-rich liquid heat exchanger (6).

[0112] The top of the lean-rich liquid heat exchanger (6) is provided with a lean liquid outlet and a rich liquid outlet, wherein the lean liquid outlet is connected to the inlet of the lean liquid recooler (7), the outlet of the lean liquid recooler (7) is connected to the middle inlet of the carbon dioxide absorption device (3), and the rich liquid outlet is connected to the inlet of the rich liquid reheater (8).

[0113] The system for cyclically removing carbon dioxide from flue gas provided by the present invention also includes a regeneration tower (9) whose inlet is connected to the outlet of the rich liquid reheater. The top outlet of the regeneration tower (9) is connected to the acid gas extraction device (13). Furthermore, the top outlet of the regeneration tower (9) is also connected to the inlet of the acid gas condenser (11), the outlet of the acid gas condenser (11) is connected to the inlet of the gas-liquid separator (12), and the outlet of the gas-liquid separator (12) is connected to the upper inlet of the tower wall of the regeneration tower (9). A liquid pump (p4) is provided between the outlet of the gas-liquid separator (12) and the upper inlet of the tower wall of the regeneration tower (9).

[0114] A liquid pump (p3) is provided between the outlet at the bottom of the regeneration tower (9) and the bottom inlet of the lean-rich liquid heat exchanger (6).

[0115] The system for cyclically removing carbon dioxide from flue gas provided by the present invention also includes a reboiler (10) whose inlet is connected to the first outlet of the regeneration tower, and the top outlet of the reboiler (10) is connected to the inlet of the lower part of the tower wall of the regeneration tower (9).

[0116] The system for cyclically removing carbon dioxide from flue gas provided by the present invention further comprises an oil bath heating device (14) whose inlet is connected to the outlet at the bottom of the reboiler (10).

[0117] (4) Test results

[0118] Tables 1 to 3 show the weight ratio of flue gas decarbonization agent and the decarbonization effect of flue gas decarbonization absorbent using the above carbon dioxide capture device. The summary tables of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Tables 1 to 3.

[0119] In Table 1, the defoamer is polydimethylsiloxane and the antioxidant is dodecyl hydroquinone;

[0120] In Table 2, the defoamer is polyoxypropylene oxyethylene glycerol ether, and the antioxidant is 4-tert-butylcatechol;

[0121] In Table 3, the defoaming agent is polydimethylsiloxane and ethylene glycol siloxane in a mass ratio of 1:1, and the antioxidant is 2,6-di-tert-butyl-p-cresol and 4-tert-butylcatechol in a mass ratio of 1:1.

[0122] The decarbonizer concentration in the recovery section is determined by an ICP spectrometer (the inorganic carbon needs to be removed, and the pH of the solution is adjusted to about 7 with sulfuric acid (the acid reacts with formate to release carbon dioxide absorbed by the flue gas decarbonizer absorbent). There is no inorganic carbon in the solution, and then ICP is used to determine the carbon concentration in the solution. The decarbonizer concentration is converted based on the carbon concentration in the flue gas decarbonizer, the measured carbon concentration, the solution volume, etc.).

[0123] Table 1

[0124]

[0125]

[0126] Table 2

[0127]

[0128] Table 3

[0129]

[0130] It can be seen from Tables 1 to 3 that the decarbonization absorbent of dihydroxyalkylpiperazine, monohydroxyalkylpiperazine and piperazine is superior to the decarbonization absorbent of dihydroxyalkylpiperazine and monohydroxyalkylpiperazine, and the decarbonization absorbent of dihydroxyalkylpiperazine and piperazine in CO2 absorption capacity, CO2 removal rate, decarbonization absorbent CO2 desorption rate and desorption energy consumption. At the same time, the decarbonization absorbent entrained in the flue gas after decarbonization is significantly reduced.

[0131] It can be seen from Table 1 that the flue gas decarbonization absorbent of the present invention is significantly superior to the flue gas decarbonization absorbent of a single component, and improves the defect that the desorption performance and absorption performance of the single decarbonization absorbent cannot be taken into account. At the same time, through the compounding of components, the desorption energy consumption of the decarbonization absorbent, the absorption capacity of CO2, and the entrainment and escape of the flue gas decarbonization absorbent in the flue gas are significantly improved.

[0132] In summary, the decarbonization agent provided by the present invention can be used to remove and recover carbon dioxide in flue gas, and the decarbonization solution has the advantages of large absorption capacity, high purification degree, high decarbonization rate, high desorption rate, and low regeneration energy consumption.

[0133] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A flue gas decarbonization absorbent, characterized in that: include: 5wt% to 45wt% of a main absorption component, wherein the main absorption component is selected from bishydroxyalkyl piperazine compounds; 2wt% to 40wt% of an activator, wherein the activator is selected from a mixture of piperazine and monohydroxyalkyl piperazine compounds; 0wt% to 5wt% of a defoaming agent; 0wt% to 5wt% of an antioxidant; 20wt% to 80wt% water.

2. The flue gas decarbonization absorbent according to claim 1, characterized in that: The bishydroxyalkyl piperazine compound is selected from one or more of N,N-di-(2-hydroxyethyl) piperazine, N,N-di-(3-hydroxypropyl) piperazine, and N-2-hydroxyethyl-N-3-hydroxypropyl piperazine.

3. The flue gas decarbonization absorbent according to claim 1, characterized in that: The monohydroxyalkyl piperazine compound is one of N-2-hydroxyethyl piperazine and N-3-hydroxypropyl piperazine or a mixture thereof, and the mass ratio of piperazine to the monohydroxyalkyl piperazine compound is 1:0.1-10.

4. The flue gas decarbonization absorbent according to claim 1, characterized in that: The defoaming agent is one or more of polyoxypropylene oxyethylene glycerol ether, polydimethylsiloxane, and ethylene glycol siloxane.

5. The flue gas decarbonization absorbent according to claim 1, characterized in that: The antioxidant is one or more of 2,6-di-tert-butyl-p-cresol, 4-tert-butylcatechol, dodecyl hydroquinone and p-hydroxyphenol.

6. The flue gas decarbonization absorbent according to claim 1, characterized in that: The pH of the flue gas decarbonization absorbent is 8-12.

7. A method for preparing a flue gas decarbonization absorbent according to any one of claims 1 to 6, characterized in that: The following steps are involved: The main absorption component, the activator, the defoamer, the antioxidant and water are mixed to obtain the flue gas decarbonization absorbent.

8. A system for cyclically removing carbon dioxide from flue gas, characterized in that: include: A carbon dioxide flue gas distribution device (2), a carbon dioxide absorption device (3), a regeneration tower (9), a heat exchange system and a control system; The carbon dioxide absorption device (3) is provided with a flue gas decarbonization absorbent according to any one of claims 1 to 6; An acid gas extraction device (13) is provided at the top of the regeneration tower (9).

9. A method for cyclically removing carbon dioxide from flue gas, characterized in that: The invention comprises the absorption of carbon dioxide, the analysis of carbon dioxide, the recycling of flue gas decarbonization absorbent and the capture and recovery of decarbonization absorbent in flue gas. The carbon dioxide is absorbed by the flue gas decarbonization absorbent according to any one of claims 1 to 6.

10. A method for cyclically removing carbon dioxide from flue gas, characterized in that: The following steps are involved: (1) Carbon dioxide absorption: The flue gas to be treated containing carbon dioxide is absorbed by a flue gas decarbonization absorbent at 20 to 60°C to obtain a rich liquid and purified flue gas; (2) Carbon dioxide desorption: The rich liquid is heated to 80-100°C and enters the regeneration tower for desorption. The top pressure of the regeneration tower is controlled to be -10-60 kPa. Carbon dioxide gas and lean liquid are obtained by desorption and regeneration. (3) Recycling of flue gas decarbonization absorbent: the lean liquid obtained in step (2) is used as a flue gas decarbonization absorbent in step (1) after heat exchange cooling; (4) Capture and recovery of decarbonizing agent in flue gas: The flue gas obtained after purification in step (1) is washed with desalted water in the decarbonizing agent recovery tower (3-2) at the top of the carbon dioxide absorption device (3), and the washing liquid is used for the preparation of flue gas decarbonizing agent or added to the lean liquid of step (3).

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