Preparation of a compounded alcohol amine absorbent for flue gas with low co 2 partial pressure and use thereof

Abstract

A polyhydric alcohol amine absorbent suitable for a CO2 capture process from a flue gas with a low CO2 partial pressure, which takes continuous operation stability and safety into account. The polyhydric alcohol amine absorbent comprises the following main components: a main absorbent, an auxiliary absorbent, an antioxidant, a corrosion inhibitor and water, and the concentration of the absorbent is 22-58% by mass fraction, wherein the main absorbent comprises one or two of diethylenetriamine, N,N-diethylethanolamine and hydroxyethyl ethylenediamine; the auxiliary absorbent comprises one or two of monoethanolamine, 2-amino-2-methyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol and 2-amino-2-methyl-1-propanol; the antioxidant comprises one or two of butanone oxime, acetoxime, hydrazine carbonate and ammonium sulfite; the corrosion inhibitor is sodium vanadate; and the balance is desalinated water.

Description

Preparation and application of a composite alcohol amine absorbent for low CO2 partial pressure flue gas

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on November 1, 2023, with application number 2023114409484 and application name “Preparation and Application of a Composite Alcoholamine Absorbent for Low CO2 Partial Pressure Flue Gas”, the entire contents of which are incorporated by reference into the application. Technical Field

[0002] The present application belongs to the field of CO2 capture by post-combustion chemical absorption method in thermal power plants, and specifically relates to the preparation and application of a composite alcohol amine absorbent for low CO2 partial pressure flue gas. Background Art

[0003] As human socioeconomic development becomes increasingly energy-dependent, the widespread use of fossil fuels has brought about a series of environmental problems. Using CO2 capture and storage technologies to separate, store, and permanently isolate CO2 from concentrated industrial emission sources is a key measure to address the conflict between fossil energy dependence and climate change. Chemical absorption CO2 capture is a key technology for achieving large-scale CO2 capture. Primary amines, such as MEA, are highly reactive and react rapidly with CO2, effectively reducing the height of carbon capture absorption towers in thermal power plants, thereby lowering investment costs. MEA is also easy to produce, ensuring a stable raw material supply. However, MEA processes face significant challenges in practical application. The reaction heat of MEA with CO2 is very high, generating a highly stable carbamate. Solvent regeneration through pyrolysis requires significant heat consumption. Furthermore, MEA readily reacts with activated gases in flue gases, resulting in significant MEA loss. The resulting byproducts further corrode equipment and promote MEA degradation.

[0004] In the existing technology, single traditional alcohol amine absorbent has great limitations in CO2 partial pressure flue gas, and its significant problems include slow reaction rate, small absorption capacity and high regeneration energy consumption. Therefore, it is necessary to explore a compound alcohol amine absorbent for low CO2 partial pressure flue gas.

[0005] Application Contents

[0006] The purpose of this application is to provide a composite alcohol amine absorbent for low CO2 partial pressure flue gas, and to use it to absorb CO2 by optimizing the reflux process of regenerated gas condensate.

[0007] The technical problems to be solved by this application are: increasing the reaction rate, increasing the absorption capacity, and reducing the regeneration energy consumption.

[0008] The purpose of this application can be achieved through the following technical solutions:

[0009] A preparation method for a composite alcohol amine absorbent for low CO2 partial pressure flue gas comprises the following steps:

[0010] S1. The polyol amine absorbent is composed of the following components in mass fractions: 18%-40% of a main absorbent, 3%-15% of an auxiliary absorbent, 0.5%-1.5% of an antioxidant, 0.5%-1.5% of a corrosion inhibitor, and 42%-78% of water.

[0011] S2. The main absorbent includes one or more of diethylenetriamine, N,N-diethylethanolamine and hydroxyethylethylenediamine.

[0012] S3. The absorbent aid comprises one or more of monoethanolamine, 2-amino-2-methyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol and 2-amino-2-methyl-1-propanol.

[0013] S4. The antioxidant comprises one or more of butanone oxime, acetone oxime, hydrazine carbonate and ammonium sulfite.

[0014] S5. The corrosion inhibitor is sodium vanadate.

[0015] Furthermore, the specific preparation steps of the polyol amine absorbent are:

[0016] Add the main absorbent to the aqueous solution, mix well, add the auxiliary absorbent, stir, control the temperature at 30℃-40℃, 30min-45min, then add the antioxidant and corrosion inhibitor, mix well to obtain the polyol amine absorbent.

[0017] The dosage ratio of the main absorbent, water, auxiliary absorbent, antioxidant and corrosion inhibitor is (18-40) g: (42-78) mL: (3-15) g: (0.5-1.5) g: (0.5-1.5) g.

[0018] An application of a composite alcohol amine absorbent for low CO2 partial pressure flue gas, as shown in FIG1 , comprises the following steps:

[0019] S1. After being cooled by the scrubber, the flue gas enters the bottom of the absorption tower and contacts with the lean absorbent solution entering from the top of the absorption tower in a countercurrent manner to carry out the CO2 absorption process.

[0020] S2. After the CO2 absorption is completed, the flue gas is discharged from the top of the absorption tower and enters the recovery tower to recover the absorbent before being discharged.

[0021] S3. After absorbing CO2, the absorbent rich liquid is discharged from the bottom of the absorption tower. A portion of the rich liquid is reinjected and sent back to the top of the absorption tower together with the lean liquid. The other portion of the rich liquid is heat exchanged in the lean-rich liquid heat exchanger and then enters the top of the regeneration tower for desorption.

[0022] S4: The lean liquid of the desorbed absorbent passes through the lean-rich liquid heat exchanger and lean liquid cooler and enters the top of the absorption tower. The regenerated CO2 gas at the top of the regeneration tower is purified by the regeneration cooler and gas-liquid separator to obtain product CO2 gas.

[0023] S5. The condensed water of the regenerated gas flows back to the lean liquid inlet pipe of the absorption tower.

[0024] Beneficial effects of this application:

[0025] 1. In the technical solution of this application, the reaction between CO2 and the tertiary amine occurs simultaneously with the reaction between CO2 and the co-absorbent. The co-absorbent, such as a primary amine or a sterically hindered amine, rapidly binds to CO2 at the gas-liquid interface, transferring the CO2 to the absorbent in the liquid phase, thereby regenerating the absorbent. The co-absorbent molecules repeatedly shuttle between the gas-liquid interface and the liquid phase until the solution reaches saturation. A small amount of co-absorbent can effectively activate the absorbent, significantly shortening the reaction process between the absorbent and CO2 and increasing the reaction rate.

[0026] 2. The technical solution of the present application can ensure that the absorbent has a good absorption efficiency of 85% to 92% in a low CO2 environment, can operate stably for more than 2 years in an oxygen-rich environment, and the annual average performance degradation rate is less than 5% (calculated as CO2 capture rate). In addition, the absorbent of the present application is also suitable for CO2 capture systems of industrial flue gases or tail gases such as coal-fired power plant flue gas, natural gas processing, lime kiln flue gas, blast furnace gas, and coke oven gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a flow chart of the CO2 capture process. DETAILED DESCRIPTION

[0028] The following will be combined with the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0029] Example 1

[0030] The flue gas inlet volume of the capture system is 2857 Nm3 / h, the CO2 content is 4.493%, the flue gas temperature at the absorption tower inlet is 40°C, the absorbent circulation flow rate is 4.5 m3 / h, the regeneration tower pressure is 10 kPa, and the reheat steam parameters are 0.4 MPa(g) and 150°C; the valve of the regenerated gas condensate return pipe is closed, and an absorption test is carried out using the absorbent formula developed in this application. The CO2 capture system capture rate is 88.07%, and the regeneration energy consumption is 3.234 GJ / tCO2.

[0031] Comparative Example 1

[0032] The flue gas inlet volume of the capture system is 2857 Nm3 / h, the CO2 content is 4.493%, the flue gas temperature at the absorption tower inlet is 40°C, the absorbent circulation flow rate is 4.5 m3 / h, the regeneration tower pressure is 10 kPa, and the reheat steam parameters are 0.4 MPa(g) and 150°C; the regeneration gas condensation reflux pipe valve is opened, and the absorption test is carried out using the absorbent formula developed in this application. The CO2 capture system capture rate is 91.35%, and the regeneration energy consumption is 3.178 GJ / tCO2.

[0033] Example 1 and Comparative Example 1 compared the optimization effects of the regeneration gas condensate reflux process under the same flue gas conditions and absorbent conditions. The results showed that after the regeneration gas condensate reflux process was optimized, the capture efficiency was improved and the regeneration energy consumption was reduced.

[0034] Example 1 and Comparative Example 1 compared the optimization effects of the regeneration gas condensate reflux process under the same flue gas conditions and absorbent conditions. The results showed that after the regeneration gas condensate reflux process was optimized, the capture efficiency was improved and the regeneration energy consumption was reduced.

[0035] Example 2

[0036] The flue gas volume entering the capture system is 2700Nm3 / h, the CO2 content is 4.6%, the flue gas temperature at the absorption tower inlet is 40℃, the absorbent circulation flow rate is 4.0m3 / h, the regeneration tower pressure is 10kPa, and the reheat steam parameters are 0.4MPa(g) and 150℃; the absorption test was carried out using a formula with AMPD as the main absorbent. The CO2 capture system capture rate was 88.71%, and the regeneration energy consumption was 3.72GJ / tCO2.

[0037] Example 3

[0038] The flue gas volume entering the capture system is 2600Nm3 / h, the CO2 content is 4.6%, the flue gas temperature at the absorption tower inlet is 37.8℃, the absorbent circulation flow rate is 5.0m3 / h, the regeneration tower pressure is 10kPa, and the reheat steam parameters are 0.4MPa(g) and 150℃; the absorption test was carried out using a formula with AEEA as the main absorbent, and the CO2 capture system capture rate was 90.10%, and the regeneration energy consumption was 3.59GJ / tCO2.

[0039] The flue gas parameters of a natural gas power plant in Beijing are shown in Table 1:

[0040] Table 1. Flue gas parameters of a natural gas power plant in Beijing

[0041] Throughout the specification, references to terms such as "one embodiment," "example," or "specific example" indicate that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0042] The above content is merely an example and explanation of the present application. Technicians in this technical field may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the application or exceed the scope defined by the claims, they should all fall within the scope of protection of the present application.

Claims

1. A preparation of a composite alcohol amine absorbent for low CO2 partial pressure flue gas, wherein: The polyol amine absorbent is composed of the following components in mass fractions: 18%-40% of a main absorbent, 3%-15% of an auxiliary absorbent, 0.5%-1.5% of an antioxidant, 0.5%-1.5% of a corrosion inhibitor and 42%-78% of water.

2. The preparation of a composite alcohol amine absorbent for low CO2 partial pressure flue gas according to claim 1, wherein: The main absorbent includes one or more of diethylenetriamine, N,N-diethylethanolamine and hydroxyethylethylenediamine, which has a large CO2 absorption capacity and low regeneration energy consumption. The auxiliary absorbent includes one or more of monoethanolamine, 2-amino-2-methyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol and 2-amino-2-methyl-1-propanol, which quickly combines with CO2 at the gas-liquid interface and transfers CO2 to the main absorbent in the liquid phase in the form of carbamate. The antioxidant includes one or more of butanone oxime, acetone oxime, hydrazine carbonate and ammonium sulfite, and the corrosion inhibitor is sodium vanadate.

3. The preparation of a composite alcohol amine absorbent for low CO2 partial pressure flue gas according to claim 1, wherein: The present application is applicable to flue gas conditions, wherein the CO2 volume fraction is 3% to 7%, the O2 volume fraction is 9% to 13%, and the remaining main component is nitrogen.

4. An application of the composite alcohol amine absorbent for low CO2 partial pressure flue gas as claimed in any one of claims 1 to 3, wherein: The flue gas is cooled by the scrubber and enters the bottom of the absorber. After the CO2 absorption is completed, the flue gas is discharged from the top of the absorber and enters the recovery tower to recover the absorbent before being discharged. The recovered rich liquid re-enters the absorber. The absorbent rich liquid is discharged from the bottom of the absorber, and part of it is sent back to the top of the absorber together with the lean liquid. The other part of the rich liquid enters the top of the regeneration tower for desorption after heat exchange in the lean-rich liquid heat exchanger. The desorbed absorbent lean liquid enters the top of the absorber through the lean-rich liquid heat exchanger and the lean liquid cooler. The regenerated gas CO2 at the top of the regeneration tower is purified by the regeneration cooler and the gas-liquid separator to obtain the product gas CO2. The condensed water of the regenerated gas flows back to the lean liquid inlet pipe of the absorber.

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