Amine non-aqueous absorbent for capturing carbon dioxide and method of using the same

Abstract

The invention discloses an amine non-aqueous absorbent for carbon dioxide capture, wherein the composition and mass percentage thereof are 20-30% of a main absorbent, 3-9% of an auxiliary absorbent, and the rest of a composite solvent; wherein the composite solvent is composed of a mixture of a polyol and an organic alcohol ether, and the mass ratio of the polyol to the organic alcohol ether is (2-5):(5-2); the amine non-aqueous absorbent provided by the invention has the characteristics of good absorption effect, fast desorption rate, high desorption load, strong cycle stability and low energy consumption.

Description

Technical Field

[0001] The invention belongs to the field of gas separation, and in particular relates to an amine non-aqueous absorbent for capturing carbon dioxide and a use method thereof. Background Art

[0002] At present, countries around the world generally believe that carbon dioxide capture, storage and utilization technology (CCUS) is the most important technology that is most likely to achieve large-scale carbon dioxide emission reduction. Carbon dioxide capture technology is a key link in CCUS, but because of its huge capture system, it consumes a lot of energy, accounting for more than 70% of the total carbon dioxide emission reduction cost, which has brought huge economic pressure to the development of the entire CCUS. Therefore, the development of economical and energy-saving carbon dioxide capture technology is of great practical significance to achieving carbon dioxide emission reduction.

[0003] At present, the main carbon dioxide capture technologies include chemical absorption, physical absorption, solid adsorption, membrane separation, etc. Among them, chemical absorption is the most widely used in industry. This method often uses an aqueous solution of alcohol amine as an absorbent. Because there are many types of alcohol amines, their performance in absorbing carbon dioxide is also different. For example, the advantages of using aqueous solutions of primary and secondary amines as absorbents are fast absorption rate, but the disadvantages are low desorption rate and small circulation capacity; the advantages of using aqueous solutions of tertiary amines as absorbents are large absorption load, but the disadvantages are extremely slow reaction rate, and the operating pressure needs to be increased or an active agent needs to be added; the aqueous solution of hindered amine 2-amino-2-methyl-1-propanol (AMP) is used as an absorbent, and the absorption and desorption performance are excellent, but the disadvantages are expensive price and serious amine loss. It can be seen that it is difficult to balance the absorption and desorption performance of alcohol amine aqueous solutions as absorbents; in addition, the presence of water causes the desorption process to consume a large amount of sensible heat and latent heat, which increases the capture energy consumption cost. Therefore, in recent years, researchers have developed non-aqueous absorbents to improve carbon dioxide capture performance and reduce capture energy consumption.

[0004] CN 110152454 A discloses a ternary non-aqueous phase absorption system composed of 2-amino-2-methyl-1-propanol (AMP), hydroxyethylethylenediamine (AAEA) and n-methylpyrrolidone (NMP); CN 107789951A discloses a non-aqueous system composed of an organic alcohol amine and an alcohol ether solvent, wherein the organic alcohol amine is one of ethanolamine, 2-amino-2-methyl-1-propanol, diethanolamine, and 2-(methylamino)ethanol, and the alcohol ether solvent is one of ethylene glycol monomethyl ether, ethylene glycol ethyl ether, ethylene glycol butyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, and propylene glycol methyl ether. CN105854529 A discloses a non-aqueous solvent carbon dioxide capture liquid composed of a composite organic amine and an organic solvent, wherein the composite organic amine is an active amine and a hindered amine, and the organic solvent is ethylene glycol and / or a lower alcohol.

[0005] In summary, it can be seen that a lot of progress has been made in the research on developing non-aqueous absorbents based on organic amines. Compared with aqueous solutions of alcohol amines, such absorbents have the advantages of low energy consumption and easy desorption, and have broad application prospects. It is necessary to further develop absorbents with better performance. Summary of the invention

[0006] The present invention provides an amine non-aqueous absorbent for capturing carbon dioxide and a method for using the same. The absorbent provided by the present invention has the characteristics of good absorption effect, fast desorption rate, high desorption load, strong cycle stability, low energy consumption, etc.

[0007] The composition and mass percentage of the amine non-aqueous absorbent for capturing carbon dioxide of the present invention are as follows: 20-30% of a main absorbent, 3-9% of an auxiliary absorbent, and the rest being a composite solvent; wherein the composite solvent is composed of a mixture of a polyol and an organic alcohol ether, and the mass ratio of the polyol to the organic alcohol ether is (2-5):(5-2).

[0008] The main absorbent is one or more of N-(2-hydroxyethyl)ethylenediamine, N-aminoethylpiperazine and diethylenetriamine; the auxiliary absorbent is 2-amino-2-methyl-1-propanol and / or piperazine.

[0009] The polyol in the composite solvent is one of ethylene glycol, diethylene glycol and glycerol, and the organic alcohol ether is one of ethylene glycol monomethyl ether, ethylene glycol ethyl ether and ethylene glycol monopropyl ether.

[0010] Another object of the present invention is to provide a method for using the above-mentioned amine non-aqueous absorbent for carbon dioxide capture, the specific steps of which are:

[0011] S1. First, dehydrate the gas containing carbon dioxide with ethylene glycol, and then make the dehydrated gas contact with an amine non-aqueous absorbent to react, and obtain a carbon dioxide-rich absorption liquid after absorption saturation. The absorption temperature is 30°C to 50°C, and the absorption pressure is normal pressure;

[0012] S2. The carbon dioxide-rich absorption liquid is heated and desorbed to release carbon dioxide. After desorption, a carbon dioxide-poor absorption liquid is obtained. The desorption temperature is 100°C to 120°C and the desorption pressure is normal pressure.

[0013] S3. The lean carbon dioxide absorption liquid is continuously used for carbon dioxide absorption, followed by desorption, and the cycle is repeated to achieve multiple absorption and regeneration cycles of the amine non-aqueous absorbent.

[0014] Compared with the existing technology, the present invention has the following technical effects:

[0015] (1) The amino-based non-aqueous absorbent provided by the present invention has a main absorbent with a large absorption capacity, and the auxiliary absorbent can adjust the viscosity and / or absorption rate of the absorbent. The two complement each other and give full play to the absorption capacity of the absorbent;

[0016] (2) The amine-based non-aqueous absorbent provided by the present invention uses a composite solvent with a high boiling point, a small specific heat capacity, and a low evaporation enthalpy to replace the traditional water solvent, thereby reducing the solvent loss and regeneration energy consumption in the process of capturing carbon dioxide, thereby reducing the capture cost;

[0017] (3) The amine-based non-aqueous absorbent provided by the present invention has good desorption performance, and has the characteristics of fast desorption rate and large desorption amount;

[0018] (4) The amine-based non-aqueous absorbent provided by the present invention has strong thermochemical stability, and the absorbent still maintains a good capture effect after multiple cycles;

[0019] In summary, the amine-based non-aqueous absorbent provided by the present invention has great application potential in capturing carbon dioxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The carbon dioxide absorption effect diagram of the absorbent described in Example 1, Example 2, Comparative Example 1, Comparative Example 2 and Comparative Example 3;

[0021] Figure 2 It is a comparison chart of carbon dioxide absorption load and desorption load of the absorbents described in Example 1, Example 2, Comparative Example 1 and Comparative Example 3;

[0022] Figure 3 This is a comparison chart of the desorption rates of carbon dioxide in desorption experiments of the absorbents described in Example 1, Example 2, Comparative Example 1 and Comparative Example 3;

[0023] Figure 4 is the carbon dioxide load of the absorbent of Example 1 after 4 cycles;

[0024] Figure 5 is the carbon dioxide load of the absorbent of Example 2 after 4 cycles. DETAILED DESCRIPTION

[0025] The present invention is further described in detail below by way of examples, but the protection scope of the present invention is not limited to the contents described above.

[0026] Example 1: The composition and mass percentage of the amine non-aqueous absorbent of this example are 25% N-(2-hydroxyethyl)ethylenediamine, 5% piperazine, 28% ethylene glycol, and 42% ethylene glycol ether; the composition is mixed and stirred in proportion to obtain the amine non-aqueous absorbent;

[0027] At the same time, a comparative absorbent (monoethanolamine 30%, water 70%) was prepared as comparative example 1; a comparative absorbent (N-(2-hydroxyethyl)ethylenediamine 30%, ethylene glycol ethyl ether 70%) was prepared as comparative example 2; a comparative absorbent (N-(2-hydroxyethyl)ethylenediamine 30%, ethylene glycol 70%) was prepared as comparative example 3;

[0028] The above-prepared amine non-aqueous absorbent, comparative example 1, comparative example 2, and comparative example 3 absorbent were used to capture carbon dioxide, and the specific operation was as follows:

[0029] Weigh 50g of absorbent on a balance and put it into a transparent bubbling absorption bottle. Keep the water bath at a constant temperature of 40℃, then pass carbon dioxide gas (volume concentration is 99.9%) into the absorbent for contact reaction. Start timing at the same time, detect and record the outlet carbon dioxide flow rate, and obtain a carbon dioxide-rich absorption liquid after the absorption is completed. The inlet carbon dioxide flow rate is 120mL / min, the absorption time is 90min, and the pressure is 0.1MPa. Detect and record the outlet carbon dioxide flow rate, and obtain a carbon dioxide-rich absorption liquid after the absorption is completed; the phase state of the absorbent after absorbing CO2 is shown in Figure 1 As can be seen from the figure, Example 1, Comparative Example 1 and Comparative Example 3 are uniform liquids, and Comparative Example 2 is solid (in terms of absorption, the solid product is viscous and will block the reactor pipeline, increasing the risk and reducing the mass transfer efficiency of CO2 in the absorbent; in terms of regeneration, the solid is difficult to separate and is easily heated unevenly during heating and desorption, which increases the equipment cost). The results show that the absorbent prepared in this embodiment can maintain a liquid state like the traditional absorbent (Comparative Example 1); further comparison of the absorption effect of the uniform liquid phase absorbent, the absorption load results are shown in Figure 2 ;

[0030] The desorption experiment was carried out on the carbon dioxide-rich absorption liquid that had completed absorption. The specific experimental method was as follows: the carbon dioxide-rich absorption agent that had completed absorption was transferred to a three-necked flask connected to a condensation reflux tube (containing a rotor in the flask), the speed was 120 rpm, the oil bath was kept at a constant temperature of 120°C, and then the condensing water was turned on and the speed was adjusted to desorb carbon dioxide. At the same time, the timing was started. The desorption time was 40 minutes, the pressure was normal pressure, the outlet carbon dioxide flow rate was detected and recorded, and the carbon dioxide-lean absorption liquid was obtained after the desorption was completed. The desorption rate results are shown in Figure 3 , the desorption load results are shown in Figure 2 .

[0031] Example 2: The composition of the amine non-aqueous absorbent of this example is as follows: 25% N-aminoethylpiperazine, 5% 2-amino-2-methyl-1-propanol, 28% ethylene glycol, and 42% ethylene glycol ether. The components are mixed and stirred in proportion to obtain the amine non-aqueous absorbent; the comparative example is the same as that of Example 1;

[0032] The above-prepared amine non-aqueous absorbent and the absorbent of Comparative Example 1 were used to capture carbon dioxide, and the specific operation was as follows:

[0033] Weigh 50g of absorbent with a balance and put it into a transparent bubbling absorption bottle. Keep the water bath temperature at 40℃, then pass carbon dioxide gas with a volume concentration of 99.9% into the absorbent for contact reaction. Start timing at the same time. The absorption time is 90min, the inlet carbon dioxide flow rate is 120mL / min, the pressure is 0.1MPa, and the outlet carbon dioxide flow rate is detected and recorded. After the absorption is completed, a carbon dioxide-rich absorption liquid is obtained; the absorption load results are shown in Figure 2 ;

[0034] The desorption experiment was carried out on the carbon dioxide-rich absorption liquid that had completed absorption. The specific experimental method was as follows: the carbon dioxide-rich absorption agent that had completed absorption was transferred to a three-necked flask connected to a condensation reflux tube (containing a rotor in the flask), the speed was 120 rpm, the oil bath was kept at a constant temperature of 120°C, and then the condensing water was turned on and the speed was adjusted to desorb carbon dioxide. At the same time, the timing was started. The desorption time was 40 minutes, the pressure was normal pressure, the outlet carbon dioxide flow rate was detected and recorded, and the carbon dioxide-lean absorption liquid was obtained after the desorption was completed. The desorption rate results are shown in Figure 3 , the desorption load results are shown in Figure 2 .

[0035] Figure 2 By comparing the carbon dioxide absorption load and desorption load of the amine-based non-aqueous absorbent of Example 1 and Example 2, and the comparative absorbent of Comparative Example 1 and Comparative Example 3, it can be seen that the absorption effects of the amine-based non-aqueous absorbent and the comparative absorbent are equivalent, and the absorption load is not less than 2.0 mol / kg, but the desorption load of the amine-based non-aqueous absorbent is higher than that of the comparative absorbent, indicating that the amine-based non-aqueous absorbent provided by the present invention has good absorption and desorption capabilities.

[0036] Figure 3 By comparing the carbon dioxide desorption rates of the amine-based non-aqueous absorbents of Example 1 and Example 2, and the comparative absorbents of Example 1 and Example 3, it can be seen that the maximum desorption rates of the amine-based non-aqueous absorbents of Example 1 and Example 2 are both higher than those of the comparative absorbent, indicating that the amine-based non-aqueous absorbents of the present invention are easy to desorb.

[0037] Example 3: Cyclic stability test

[0038] The amine-based non-aqueous absorbents in Examples 1 and 2 were subjected to multiple absorption and desorption experiments. The relationship between the carbon dioxide absorption load and the number of cycles of the absorbents in Examples 1 and 2 was investigated through cycle experiments. The experimental results are shown in FIG. Figure 4 , 5It can be seen that the amine-based non-aqueous absorbents of Examples 1 and 2 can still maintain a stable carbon dioxide load after 4 cycles, indicating that the amine-based non-aqueous absorbents of the present invention have good cyclic stability.

[0039] The above description is only part of the embodiments of the present invention and is not intended to be the scope of protection of the present invention. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present invention are included in the scope of protection of the present invention.

Claims

1. An amine non-aqueous absorbent for capturing carbon dioxide, characterized in that: The composition and mass percentage are as follows: 20-30% of the main absorbent, 3-9% of the auxiliary absorbent, and the rest of the composite solvent; wherein the composite solvent is a mixture of polyols and organic alcohol ethers, and the mass ratio of the polyols to the organic alcohol ethers is (2-5):(5-2); The main absorbent is one or more of N-(2-hydroxyethyl)ethylenediamine, N-aminoethylpiperazine, and diethylenetriamine; the auxiliary absorbent is 2-amino-2-methyl-1-propanol and / or piperazine; the polyol in the composite solvent is one of ethylene glycol, diethylene glycol, and propylene glycol; and the organic alcohol ether in the composite solvent is one of ethylene glycol monomethyl ether, ethylene glycol ethyl ether, and ethylene glycol monopropyl ether.

2. The method for using the amine non-aqueous absorbent for capturing carbon dioxide according to claim 1, characterized in that: Here are the steps: (1) First, dehydrate the gas containing carbon dioxide with ethylene glycol, and then contact the dehydrated gas with an amine non-aqueous absorbent to react, and obtain a carbon dioxide-rich absorption liquid after absorption saturation. The absorption temperature is 30°C~50°C and the absorption pressure is normal pressure; (2) heating the carbon dioxide-rich absorption liquid in step (1) to desorb carbon dioxide, and obtaining a carbon dioxide-lean absorption liquid after desorption. The desorption temperature is 100° C. to 120° C., and the desorption pressure is atmospheric pressure; (3) The lean carbon dioxide absorption liquid continues to be used for carbon dioxide absorption, followed by desorption, and the cycle is repeated to achieve multiple absorption and regeneration cycles of the amine non-aqueous absorbent.

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