Organic amine-alcohol aqueous sulfur dioxide liquid-liquid phase change absorbent and its preparation method and application

Abstract

The present invention relates to the technical field of gas separation and energy conservation and emission reduction, and specifically to an organic amine-alcohol aqueous SO2 liquid-liquid phase change absorbent and its preparation method and application. The absorbent comprises the following components: 10-30 parts by weight of a piperazine organic amine, 5 to 60 parts by weight of a phase separator, and 0.1 to 10 parts by weight of a phase change aid; the piperazine organic amine contains an alkylhydroxyl group, and the alkylhydroxyl group is selected from one or two of hydroxyethyl or hydroxypropyl; the phase separator is selected from one or more of C4 to C7 alcohols, and the phase change aid is selected from an inorganic acid or an organic acid. The preparation method of the liquid-liquid phase change absorbent comprises the following steps: adding a raw material containing a piperazine organic amine, a phase separator, and a phase change aid into water, and dissolving the raw material to obtain the liquid-liquid phase change absorbent. The absorbent can improve the SO2 desorption efficiency, reduce the desorption energy consumption, and significantly reduce the operating costs of the enterprise.

Description

Technical Field

[0001] The present invention relates to the technical field of gas separation and energy conservation and emission reduction, and in particular to an organic amine-alcohol water-based SO2 liquid-liquid phase change absorbent, a preparation method thereof, and applications thereof. Background Art

[0002] Chemical absorption of acidic gases such as SO2 or CO2 has the advantages of fast absorption rate, large absorption capacity and good selectivity. The process is mature and applicable to a wide range of acidic gas concentrations in waste gas. However, the rich liquid after absorption needs to be thermally desorbed at high temperature to remove the acidic gas SO2 or CO2 before the absorbent can be recycled. The high energy consumption restricts its development.

[0003] Phase change absorption refers to the formation of two phases, rich and poor, with a large difference in the amount of SO2 loaded during or after the absorption of SO2. Only the rich phase with a higher load is sent to the regeneration tower, which greatly reduces the volume of the regeneration solution and can significantly reduce the regeneration energy consumption. Most of the SO2 phase change absorbents reported so far are solvent-based, and undergo liquid-solid phase change after absorption. The Chinese patent "A mixed organic solution for capturing CO2 and SO2 acidic gases by phase change" (CN201510675190.1) uses a mixed solution composed of organic amine absorbents such as chain polyamines, alcoholamines, and amides and organic solvents such as alcohols, ethers, ketones, and esters to absorb SO2, and then the liquid and solid phases are separated. The solid is heated to 115°C and 0.27Mpa to achieve SO2 recovery. However, the viscosity of these phase change absorbents is very high, which is not conducive to heat and mass transfer and fluid transportation, and the phase separation time required is long. To reduce the viscosity of the organic phase, the patented "Method for Regenerating the Organic Phase After Desulfurization and Decarbonization with a Phase Change Absorbent" (CN201610440435.7) utilizes the displacement, cavitation, and resonance effects of ultrasound on the phase change absorbent to regenerate the rich liquid. However, this requires an ultrasonic device in the regeneration tower, resulting in a complex system, high investment, and consumption of ultrasonic energy, making practical industrial application difficult. Furthermore, the solids produced during phase change absorption can easily clog pipelines, creating instabilities in practical applications.

[0004] Since the SO2-containing flue gas processed in industrial production is often a wet gas containing a large amount of saturated water, non-aqueous solvent-based phase change absorbents cannot meet industrial requirements. The Chinese invention patent "An MDEA composite absorbent and separation method for acid gas separation" (CN201610035154.3) is based on the solubility effect of MDEA and invented a composite absorbent composed of MDEA, water-immiscible alcohols and water. Before absorbing the acid gas, it is a homogeneous phase. After absorbing the acid gas, a lean liquid phase with a low acid gas load and a rich liquid phase with a high acid gas load are formed. Only the rich liquid phase enters the desorption unit, reducing the desorption energy consumption. Since H2S, SO2, etc. are toxic or corrosive, the embodiments of this patent only use the absorption of CO2 as an example to illustrate the advantages and characteristics of the invented liquid-liquid phase change absorbent. The patent "A phase change absorption liquid for capturing sulfur dioxide" (CN201811230995.5) also discloses a SO2 absorption liquid composed of an alcoholamine absorbent, sulfone and water. Compared with the conventional desulfurization process, the absorption liquid reduces the desorption liquid processing volume by 30%-55% (mass fraction), significantly reducing the desorption energy consumption. Summary of the Invention

[0005] The technical problem solved by the present invention is that although alcoholamines are widely used in the field of chemical absorption of CO2 and H2S, their selectivity for SO2 is poor. Furthermore, due to the strong corrosiveness of SO2 and the poor stability of alcoholamines, alcoholamines are rarely used as SO2 absorbents in industry. Organic amine wet flue gas desulfurization technology has the advantages of high desulfurization rate, good selectivity, high absorbent recycling rate, and no secondary pollution. Currently, it is increasingly widely used in industries such as non-ferrous metallurgy, sulfuric acid industry, and coal chemical industry. Existing organic amine desulfurizers mostly focus on their absorption capacity for SO2. To make the organic amine desulfurization process more efficient, the absorbent needs to be recycled after desorption. However, the desorption efficiency, recycling rate, and recycling effect of the current absorbents need to be improved. In addition, the rich amine solution after absorption needs to be heated at high temperature to desorb SO2, which requires the consumption of a large amount of raw steam and high regeneration energy consumption, resulting in excessively high operating costs for enterprises, limiting the widespread application of organic amine desulfurizers in industry. From the perspective of industrial application, the development of water-soluble SO2 liquid-liquid phase change absorbent is of great significance to reducing the energy consumption of organic amine desulfurization system, reducing system operating costs and improving the economic benefits of enterprises.

[0006] The purpose of the present invention is to provide an organic amine-alcohol aqueous SO2 liquid-liquid phase change absorbent with high absorption efficiency, good selectivity, high desorption rate, low regeneration energy consumption, energy saving and environmental protection. The absorbent is used to capture SO2, is soluble in water, and can be used in an aqueous environment.

[0007] To address the aforementioned technical issues, the present invention provides an organic amine-alcohol aqueous SO2 liquid-liquid phase-change absorbent. After absorbing SO2, this absorbent rapidly separates into two aqueous phases: a lower aqueous phase that is SO2-rich and an upper aqueous phase that is SO2-lean. This SO2-rich phase (lower aqueous phase) only needs to be fed to a desorption tower for regeneration, thus addressing the high desorption energy consumption of existing non-phase-change absorption systems.

[0008] Specifically, to address the deficiencies of the prior art, the present invention provides the following technical solutions:

[0009] An organic amine-alcohol aqueous SO2 liquid-liquid phase change absorbent, characterized in that the absorbent comprises the following components:

[0010] 10-30 parts by weight of a piperazine organic amine, 5-60 parts by weight of a phase separator, and 0.1-10 parts by weight of a phase change agent; the piperazine organic amine contains an alkylhydroxyl group, and the alkylhydroxyl group is selected from one or two of hydroxyethyl or hydroxypropyl; the phase separator is selected from one or more of C4-C7 alcohols, and the phase change agent is selected from an inorganic acid or an organic acid.

[0011] Preferably, in the above liquid-liquid phase change absorbent, the absorbent comprises the following components: 15-30 parts by weight of a piperazine organic amine, 10-45 parts by weight of a phase separation agent, and 0.1-5 parts by weight of a phase change auxiliary agent.

[0012] Preferably, in the above liquid-liquid phase change absorbent, the piperazine organic amine is 20-30 parts by weight, preferably 25-30 parts by weight;

[0013] Preferably, in the above liquid-liquid phase change absorbent, the phase separation agent is 15-45 parts by weight, preferably 20-45 parts by weight, more preferably 20-30 parts by weight;

[0014] Preferably, in the liquid-liquid phase change absorbent, the phase change auxiliary agent is 0.5-5 parts by weight, preferably 3-5 parts by weight.

[0015] Preferably, in the above-mentioned liquid-liquid phase change absorbent, the piperazine organic amine is selected from one or more of N-hydroxyethylpiperazine, N,N-bis(2-hydroxyethyl)piperazine, N,N-bis(2-hydroxypropyl)piperazine or N-hydroxyethyl-N-hydroxypropylpiperazine.

[0016] Preferably, in the above liquid-liquid phase-change absorbent, the piperazine organic amine contains at least N-hydroxyethylpiperazine.

[0017] Preferably, in the above-mentioned liquid-liquid phase change absorbent, the piperazine organic amine in the absorbent is a mixture of N,N-bis(2-hydroxyethyl)piperazine (BHEP) and N-hydroxyethylpiperazine (HEP) or a mixture of N,N-bis(2-hydroxypropyl)piperazine (HPP) and N-hydroxyethylpiperazine (HEP).

[0018] Preferably, in the liquid-liquid phase change absorbent, the mass fraction of the N-hydroxyethylpiperazine in the piperazine organic amine is 10% to 20%.

[0019] Preferably, in the above liquid-liquid phase change absorbent, the phase separator is selected from one or more of n-butanol, n-pentanol, sec-pentanol, cyclohexanol or 1,7-heptanediol.

[0020] Preferably, in the above liquid-liquid phase change absorbent, the number of hydroxyl groups of the phase separator is 1-2.

[0021] Preferably, in the above liquid-liquid phase change absorbent, the phase change auxiliary agent is selected from one or more of sulfuric acid, phosphoric acid, hydrochloric acid or boric acid.

[0022] Preferably, in the above liquid-liquid phase change absorbent, the phase change auxiliary agent is selected from boric acid, hydrochloric acid or phosphoric acid.

[0023] Preferably, in the above liquid-liquid phase change absorbent, the absorbent further comprises water, and the weight proportion of the water is 30-70 parts.

[0024] The present invention also provides a method for preparing an organic amine-alcohol aqueous SO2 liquid-liquid phase change absorbent, which is characterized by comprising the following steps:

[0025] Raw materials including piperazine organic amine, phase separation agent and phase change auxiliary agent are added into water and dissolved to obtain the organic amine-alcohol water-based SO2 liquid-liquid phase change absorbent.

[0026] The present invention also provides a method for capturing SO2, characterized in that it comprises the following steps:

[0027] (1) Absorption process: The SO2-containing gas is mixed with the above-mentioned liquid-liquid phase change absorbent. After the absorption reaction, the absorption liquid is rapidly separated into a lower water phase and an upper water phase;

[0028] (2) Desorption process: The lower aqueous phase is heated for desorption, and the lean liquid obtained after desorption is mixed with the upper aqueous phase obtained in step (1) and recycled as an absorbent.

[0029] Preferably, in the above-mentioned method for capturing SO2, the temperature of the absorption reaction process is 20-50°C, and the temperature of the desorption process is 80-120°C, preferably 100-110°C.

[0030] Preferably, in the above method for capturing SO2, the volume fraction of SO2 in the SO2-containing gas is 0.1% to 15%, preferably 5% to 15%. The flow rate of the gas is 1.0-2.0 L / min.

[0031] Preferably, in the above method for capturing SO2, the absorption process takes 120 to 180 minutes.

[0032] Preferably, in the above method for capturing SO2, the temperature of the desorption process is 105-110°C and the time of the desorption process is 0.5-3.5 hours, preferably 2.5-3.5 hours.

[0033] Preferably, in the above-mentioned method for capturing SO2, in step (1), the volume of the lower aqueous phase in the absorption tower accounts for 20% to 90% of the total liquid phase volume. Preferably, the lower aqueous phase in the absorption tower accounts for 40% to 90% of the total liquid phase volume, and preferably 65% ​​to 85%.

[0034] Preferably, in the above method for capturing SO2, in step (1), the ratio of the concentration of SO2 in the lower and upper aqueous phases is (3-15):1, preferably (5-15):1.

[0035] The present invention also provides application of the organic amine-alcohol water-based SO2 liquid-liquid phase change absorbent in the field of flue gas desulfurization.

[0036] The advantages of the present invention are:

[0037] (1) The phase-change absorbent provided by the present invention can improve the SO2 desorption efficiency, reduce the desorption energy consumption, increase the cyclic absorption capacity and recycling effect of the absorbent, and significantly reduce the operating costs of the enterprise.

[0038] (2) In the phase-change absorbent provided by the present invention, the low-polarity phase-separating agent organic alcohol allows the piperazine-type organic amine to quickly separate into two aqueous phases after absorbing a small amount of SO2. Moreover, since the upper aqueous phase only carries a very small amount of SO2, only the lower aqueous phase loaded with SO2 needs to be desorbed, thereby reducing the volume of the desorbed rich liquid and significantly reducing the desorption energy consumption.

[0039] (3) The piperazine organic amine and the organic alcohol with a longer carbon chain in the phase change absorbent provided by the present invention have a high boiling point, thereby avoiding the volatility loss of the absorbent and the solvent.

[0040] (4) The phase change auxiliary agent in the phase change absorbent provided by the present invention can not only reduce the volatilization loss of piperazine organic amines, but also increase the polarity of the absorption product and promote the occurrence of phase change.

[0041] (5) The phase change absorbent provided by the present invention is an aqueous solution with low viscosity and excellent heat and mass transfer performance and transportation performance. Therefore, there is no need to replace or modify the heat exchanger, pump, etc. in the existing industrial organic amine desulfurization system, and it is easy to use.

[0042] In summary, the phase change absorbent provided by the present invention has a large cyclic absorption capacity for SO2, a fast absorption rate, a high desorption efficiency, and a low desorption energy consumption. The method and process for using the absorbent provided by the present invention are energy-saving and environmentally friendly, with no secondary pollution. The absorbent can be recycled multiple times, with better recycling utilization rate and recycling effect, and has broad application prospects. DETAILED DESCRIPTION

[0043] In view of the fact that the absorption effect and stability of the absorbents currently used to capture SO2 need to be improved, the present invention mixes a specific phase separation agent with a piperazine organic amine absorbent, a phase change additive and water in an appropriate proportion to form a new phase change absorbent. The absorbent has strong stability, high absorption efficiency, and is more energy-saving and environmentally friendly during use.

[0044] In a preferred embodiment, the present invention provides an organic amine-alcohol water-based SO2 liquid-liquid phase change absorbent for absorbing and separating SO2, the absorbent consisting of an organic amine desulfurizer, a phase separator, a phase change aid and water, wherein the organic amine desulfurizer is a mixture of one or more of the piperazine organic amines N-hydroxyethylpiperazine HEP, N,N-bis(2-hydroxyethyl)piperazine BHEP and N,N-bis(2-hydroxypropyl)piperazine HPP, N-hydroxyethyl-N-hydroxypropylpiperazine (HEHPP), the phase separator is any one or a combination of two of C4 to C7 alcohols, and the phase change aid is one or two of sulfuric acid, phosphoric acid, hydrochloric acid and boric acid.

[0045] In the liquid-liquid phase change absorbent, the mass fraction of the piperazine organic amine is 10% to 30%, the mass fraction of the phase separator is 5% to 60%, the mass fraction of the phase change auxiliary agent is 0.1% to 10%, and the rest is water.

[0046] Preferably, in the liquid-liquid phase change absorbent, the mass fraction of the piperazine organic amine is 15% to 30%, the mass fraction of the phase separation agent is 15% to 45%, the mass fraction of the phase change auxiliary agent is 0.5% to 5%, and the remainder is water.

[0047] Preferably, the piperazine organic amine in the liquid-liquid phase change absorbent is a mixture of N,N-bis(2-hydroxyethyl)piperazine BHEP and N-hydroxyethylpiperazine HEP or a mixture of N,N-bis(2-hydroxypropyl)piperazine HPP and N-hydroxyethylpiperazine HEP.

[0048] Preferably, the phase separation agent in the liquid-liquid phase change absorbent is any one of n-butanol, n-pentanol, sec-pentanol, cyclohexanol or 1,7-heptanediol, or a combination of two thereof.

[0049] Preferably, by adjusting the absorbent composition ratio, the phase-change absorbent spontaneously forms liquid-liquid two phases after absorbing SO2, and the volume of the lower phase accounts for 20% to 85% of the total liquid phase volume ratio.

[0050] Preferably, by adjusting the absorbent composition ratio, the phase-change absorbent spontaneously forms liquid-liquid two phases after absorbing SO2, and the volume of the lower phase accounts for 65% to 85% of the total liquid phase volume ratio.

[0051] In another preferred embodiment, the present invention provides a method for capturing SO2, comprising the following steps:

[0052] After the SO2-containing flue gas and the above-mentioned absorbent are mixed and reacted, the absorbent is divided into a lower water phase and an upper water phase. The lower water phase is passed into a desorption device for desorption. The lean liquid obtained after desorption is mixed with the upper water phase and recycled as an absorbent.

[0053] In another preferred embodiment, the present invention provides an application of an organic amine-alcohol aqueous SO2 liquid-liquid phase change absorbent in the field of SO2 capture, comprising the following steps:

[0054] S1, using the above-mentioned piperazine organic amine as an absorbent with a mass fraction of 10% to 30%, adding an organic alcohol with a mass fraction of 10% to 45%, then adding an acid with a mass fraction of 0.1% to 6.0% as a phase change aid, and finally using water to prepare a homogeneous aqueous solution in a certain proportion as a phase change absorbent;

[0055] In step S2, the phase-change absorbent prepared in step S1 is used to absorb and separate simulated flue gas containing a SO2 volume fraction of 0.1% to 15% with the remainder being N2, at an absorption temperature of 20°C to 50°C. After absorbing SO2, the gas spontaneously separates into two phases: a lower aqueous phase, a SO2-rich phase, containing most of the organic amine salts resulting from the reaction of the organic amine with SO2, water, and a small amount of phase-separating agent; and an upper aqueous phase, a SO2-lean phase, containing a small amount of the organic amine salts resulting from the reaction of the organic amine with SO2, water, and a large amount of phase-separating agent.

[0056] In step S3, the upper and lower aqueous phases after SO2 absorption are separated, with the lower aqueous phase being sent for desorption and regeneration. The desorption and regeneration process takes place at a temperature of 100-120°C for 0.5-3.5 hours, and the desorbed SO2 is recycled. The lean amine solution after rich phase regeneration is mixed with the upper aqueous phase to produce a liquid-liquid phase change absorbent for cyclic SO2 absorption.

[0057] The piperazine organic amine described in the present invention refers to a compound containing a piperazine structure. Preferably, an alkylhydroxyl group is connected to the nitrogen atom of the piperazine structure.

[0058] The following specific examples further illustrate the organic amine-alcohol aqueous SO2 liquid-liquid phase change absorbent of the present invention, its preparation method and application.

[0059] The piperazine organic amine HEP described in the present invention is N-hydroxyethylpiperazine, the organic amine BHEP is N,N-bis(2-hydroxyethyl)piperazine, also known as 1,4-bis(2-hydroxyethyl)piperazine, the organic amine HPP is N,N-bis(2-hydroxypropyl)piperazine, also known as 1,4-bis(2-hydroxypropyl)piperazine, prepared by the method described in Example 1, Step A of CN101584961A, and the organic amine HEHPP is N-hydroxyethyl-N-hydroxypropylpiperazine, also known as 1-(2-hydroxyethyl)-4-(2-hydroxypropyl)piperazine, prepared by the steps described in Example 1 of CN103638779A. Other reagents were purchased from China National Pharmaceutical Group. In the following examples, the simulated flue gas, except for SO2, consists of N2.

[0060] Example 1

[0061] A liquid-liquid phase-change absorbent for SO₂ capture was prepared by combining N,N-bis(2-hydroxyethyl)piperazine (BHEP), n-butanol, and water, followed by the addition of sulfuric acid. The resulting absorbent contained 30% BHEP by weight, 20% n-butanol by weight, 3.5% sulfuric acid by weight, and the remainder being water.

[0062] Simulated flue gas containing 9% SO₂ was passed through 100g of the absorbent at a flow rate of 1.4L / min, an absorption temperature of 25°C, and an absorption time of 120min. After absorbing the SO₂, the absorbent automatically formed a liquid-liquid two-phase system, with the lower aqueous phase accounting for 80.7% of the total volume. The ratio of SO₂ concentrations in the lower and upper aqueous phases was 10.8, and the absorbent absorbed 0.6874mol / mol of amine. The SO₂-rich phase (i.e., the lower aqueous phase) was sent for desorption and regeneration at a regeneration temperature of 107°C and a regeneration time of 180min. The SO₂ cycle absorption EQ was 0.4342mol / mol of amine, and the SO₂ desorption rate was 74.6%.

[0063] Compared to an absorbent without n-butanol, this example reduced the amount of regenerated liquid by 19%, increased the circulating absorption capacity (EQ) by 26.4%, increased the desorption efficiency (DE) by 12.8%, and reduced the regeneration energy consumption (Q) by 34%. While the viscosity of the absorbent without n-butanol was 10.5 cP, the viscosity of the rich phase in this example increased to 25.0 cP, which remains relatively low.

[0064] Among them, the method for detecting the SO2 concentration in the upper and lower water phases after absorption by the absorbent is the iodine titration method, and the viscosity is measured by a rotational viscometer.

[0065] Circulating absorption amount EQ = the difference between the SO2 loading of the rich liquid obtained after the absorption liquid absorbs SO2 and the SO2 loading of the lean liquid obtained after desorption, that is, the number of moles of SO2 desorbed from each mole of organic amine, the unit is molSO2 / molamine.

[0066] Desorption rate DE of the desorption process = the amount of SO2 desorbed / the amount of SO2 in the rich solution before desorption × 100%

[0067] The energy consumption Q of the desorption process refers to the amount of electricity consumed to desorb a unit mass of SO2, and its unit is GJ / tSO2.

[0068] Example 2

[0069] An absorbent for SO2 capture was prepared by mixing N,N-bis(2-hydroxyethyl)piperazine (BHEP), n-butanol, and water, followed by the addition of boric acid. The absorbent contained 30% BHEP by weight, 20% n-butanol by weight, 3.5% boric acid by weight, and the remainder water.

[0070] Simulated flue gas containing 9.1% SO₂ was passed through 100g of the absorbent at a flow rate of 1.4L / min, an absorption temperature of 25°C, and an absorption time of 120 minutes. After SO₂ absorption, the absorbent formed two liquid-liquid phases, with the lower aqueous phase accounting for 80.4% of the total volume. The SO₂ concentration ratio between the lower and upper aqueous phases was 11.2, and the absorbent absorbed 0.801mol / mol of amine. The SO₂-rich phase was then desorbed and regenerated at a temperature of 107°C and a regeneration time of 180 minutes. The SO₂ cycle absorption EQ was 0.429mol / mol of amine, and the SO₂ desorption rate was 78.2%.

[0071] Compared to a homogeneous absorbent without n-butanol, this example reduced the amount of regenerated liquid by 21%, increased the circulating absorption capacity (EQ) by 31.2%, increased the desorption efficiency (DE) by 28.5%, and reduced the regeneration energy consumption (Q) by 38.1%. While the viscosity of the absorbent without n-butanol was 11.3 cP, the viscosity of the rich phase in this example increased to 24.6 cP, a slight increase that remained relatively low.

[0072] Example 3

[0073] An absorbent for SO2 capture was prepared by mixing N,N-bis(2-hydroxyethyl)piperazine (BHEP), n-butanol, and water, followed by the addition of phosphoric acid. The resulting absorbent contained 30% BHEP by weight, 20% n-butanol by weight, 3.5% phosphoric acid by weight, and the remainder being water.

[0074] Simulated flue gas containing 9.1% SO₂ was passed through 100g of the absorbent at a flow rate of 1.4L / min, an absorption temperature of 25°C, and an absorption time of 120 minutes. After absorbing the SO₂, the absorbent formed a liquid-liquid two-phase system, with the lower aqueous phase accounting for 81.1% of the total volume. The SO₂ concentration ratio between the lower and upper aqueous phases was 12.9, and the absorbent absorbed 0.709mol / mol of amine. The SO₂-rich phase was then desorbed and regenerated at a temperature of 107°C and a regeneration time of 180 minutes. The SO₂ cycle absorption EQ was 0.367mol / mol of amine, and the SO₂ desorption rate was 59.7%.

[0075] Compared to a homogeneous absorbent without n-butanol, this example reduced the amount of regenerated liquid by 19%, increased the circulating absorption capacity (EQ) by 27.8%, increased the desorption efficiency (DE) by 32.3%, and reduced the regeneration energy consumption (Q) by 33.4%. While the viscosity of the absorbent without n-butanol was 10.5 cP, the viscosity of the rich phase in this example increased to 30.2 cP, a slight but still relatively small increase.

[0076] Example 4

[0077] An absorbent for SO2 capture was prepared by mixing N,N-bis(2-hydroxyethyl)piperazine (BHEP), n-butanol, and water, followed by the addition of hydrochloric acid. The absorbent contained 30% BHEP by weight, 20% n-butanol by weight, 3.5% hydrochloric acid by weight, and the remainder being water.

[0078] Simulated flue gas containing 9.1% SO₂ was passed through 100g of the absorbent at a flow rate of 1.4L / min, an absorption temperature of 25°C, and an absorption time of 120 minutes. After absorbing the SO₂, the absorbent formed a liquid-liquid two-phase system, with the lower aqueous phase accounting for 83.6% of the total volume. The SO₂ concentration ratio between the lower and upper aqueous phases was 8.1, and the absorbent absorbed 0.689mol / mol of amine. The SO₂-rich phase was then desorbed and regenerated at a temperature of 107°C and a regeneration time of 180 minutes. The SO₂ cycle absorption EQ was 0.385mol / mol of amine, and the SO₂ desorption rate was 42.3%.

[0079] Compared to a homogeneous absorbent without n-butanol, this example reduced the amount of regenerated liquid by 17%, increased the circulating absorption capacity (EQ) by 25.4%, increased the desorption efficiency (DE) by 20.8%, and reduced the regeneration energy consumption (Q) by 32.1%. While the viscosity of the absorbent without n-butanol was 10.5 cP, the viscosity of the rich phase in this example increased to 28.5 cP, a slight but still relatively small increase.

[0080] By comparing Examples 1 to 4, it can be found that the type of phase change additive in the phase change absorbent has a certain influence on the phase change absorbent. This is because the acid affects the polarity of the organic amine salt. The polar organic amine salt has a strong salting-out ability and has an advantage in competing with the organic solvent for free water, thereby expelling the organic solvent and separating it into liquid-liquid phases.

[0081] Example 5

[0082] An absorbent for SO2 capture was prepared by mixing N,N-bis(2-hydroxypropyl)piperazine (HPP), n-butanol, and water, followed by the addition of boric acid. The absorbent contained 20% HPP by weight, 15% n-butanol by weight, 2.0% boric acid by weight, and the remainder being water.

[0083] Simulated flue gas containing 11.1% SO₂ was passed through 100g of absorbent at a flow rate of 1.6L / min, an absorption temperature of 25°C, and an absorption time of 120 minutes. After absorbing the SO₂, the absorbent formed a liquid-liquid two-phase system, with the lower aqueous phase accounting for 83.6% of the total volume. The ratio of SO₂ concentrations in the lower and upper aqueous phases was 8.21, and the absorbent absorbed 0.858 mol / mol of amine. The SO₂-rich phase was then desorbed and regenerated at a temperature of 106°C and a regeneration time of 180 minutes. The SO₂ cycle absorption EQ was 0.415 mol / mol of amine, and the SO₂ desorption rate was 80.6%.

[0084] Compared to a homogeneous absorbent without n-butanol, this example reduced the amount of regenerated liquid by 16%, increased the circulating absorption capacity (EQ) by 28.3%, increased the desorption efficiency (DE) by 16.5%, and reduced the regeneration energy consumption (Q) by 16.2%. While the viscosity of the absorbent without n-butanol was 6.1 cP, the viscosity of the rich phase in this example was 8.1 cP, still relatively low.

[0085] Example 6

[0086] An absorbent for SO2 capture was prepared by mixing N,N-bis(2-hydroxypropyl)piperazine (HPP), n-butanol, and water, followed by the addition of boric acid. The absorbent contained 20% HPP by weight, 20% n-butanol by weight, 2.0% boric acid by weight, and the remainder being water.

[0087] Simulated flue gas containing 11.1% SO₂ was passed through 100g of absorbent at a flow rate of 1.6L / min, an absorption temperature of 25°C, and an absorption time of 120 minutes. After absorbing the SO₂, the absorbent formed two liquid-liquid phases, with the lower aqueous phase accounting for 78.3% of the total volume. The ratio of the lower and upper aqueous phases to the SO₂ concentration was 7.81, and the absorbent absorbed 0.809mol / mol of amine. The SO₂-rich phase was then desorbed and regenerated at a temperature of 106°C and a regeneration time of 180 minutes. The SO₂ cycle absorption EQ was 0.469mol / mol of amine, and the SO₂ desorption rate was 83.6%.

[0088] Compared to a homogeneous absorbent without n-butanol, this embodiment reduced the amount of regenerated liquid by 22%, increased the circulating absorption capacity (EQ) by 30.5%, increased the desorption efficiency (DE) by 20.6%, and reduced the regeneration energy consumption (Q) by 25.6%. While the viscosity of the absorbent without n-butanol was 6.1 cP, the viscosity of the rich phase in this embodiment was 10.5 cP, which is still relatively low.

[0089] Example 7

[0090] An absorbent for SO2 capture was prepared by mixing N,N-bis(2-hydroxypropyl)piperazine (HPP), n-butanol, and water, followed by the addition of boric acid. The absorbent contained 20% HPP by weight, 45% n-butanol by weight, 2.0% boric acid by weight, and the remainder being water.

[0091] Simulated flue gas containing 11.1% SO₂ was passed through 100g of absorbent at a flow rate of 1.6L / min, an absorption temperature of 25°C, and an absorption time of 120 minutes. After absorbing the SO₂, the absorbent formed two liquid-liquid phases, with the lower aqueous phase accounting for 69.7% of the total volume. The ratio of the lower and upper aqueous phases to the SO₂ concentration was 5.62, and the absorbent absorbed 0.756mol / mol of amine. The SO₂-rich phase was desorbed and regenerated at a regeneration temperature of 106°C and a regeneration time of 180 minutes. The SO₂ cycle absorption EQ was 0.505mol / mol of amine, and the SO₂ desorption rate was 86.1%.

[0092] Compared to a homogeneous absorbent without n-butanol, this embodiment reduced the amount of regenerated liquid by 30%, increased the circulating absorption capacity (EQ) by 31.2%, increased the desorption efficiency (DE) by 27.6%, and reduced the regeneration energy consumption (Q) by 20.9%. While the viscosity of the absorbent without n-butanol was 6.1 cP, the viscosity of the rich phase in this embodiment was 19.3 cP, which is still relatively low.

[0093] Comparing Examples 5 to 7, it can be found that the higher the mass fraction of n-butanol in the phase-change absorbent, the lower the amount of SO₂ absorbed. This is mainly due to the increased viscosity of the lower phase after absorption separation, which reduces mass transfer efficiency. The higher the mass fraction of n-butanol, the more obvious this effect is. However, as the mass fraction of n-butanol increases, the reduction rate of regenerated treatment liquid, the increase rate of circulating absorption capacity, the increase rate of desorption rate, and the reduction rate of regeneration energy consumption all gradually increase.

[0094] Example 8

[0095] An absorbent for SO₂ capture was prepared by mixing N,N-bis(2-hydroxypropyl)piperazine (HPP), n-butanol, and water, followed by the addition of boric acid. The absorbent contained 20% HPP by weight, 20% n-butanol by weight, 1.2% boric acid by weight, and the remainder being water.

[0096] Simulated flue gas containing 11.1% SO₂ was passed through 100g of absorbent at a flow rate of 1.6L / min, an absorption temperature of 25°C, and an absorption time of 120 minutes. After absorbing the SO₂, the absorbent formed a liquid-liquid two-phase system, with the lower aqueous phase accounting for 81.1% of the total volume. The SO₂ concentration ratio between the lower and upper aqueous phases was 3.99, and the absorbent absorbed 1.03 mol / mol of amine. The SO₂-rich phase was then desorbed and regenerated at a temperature of 106°C and a regeneration time of 180 minutes. The SO₂ cycle absorption EQ was 0.383 mol / mol of amine, and the SO₂ desorption rate was 71.5%.

[0097] Compared to a homogeneous absorbent without n-butanol, this example reduced the amount of regenerated liquid by 19%, increased the circulating absorption capacity (EQ) by 28.0%, increased the desorption efficiency (DE) by 32.0%, and reduced the regeneration energy consumption (Q) by 19.8%. While the viscosity of the absorbent without n-butanol was 6.1 cP, the viscosity of the rich phase in this example was 9.8 cP, still relatively low.

[0098] Example 9

[0099] An absorbent for SO2 capture was prepared by mixing N,N-bis(2-hydroxypropyl)piperazine (HPP), n-butanol, and water, followed by the addition of boric acid. The absorbent contained 20% HPP by weight, 20% n-butanol by weight, 0.32% boric acid by weight, and the remainder being water.

[0100] Simulated flue gas containing 11.1% SO₂ was passed through 100g of absorbent at a temperature of 25°C for 120 minutes. After SO₂ absorption, the absorbent formed two liquid-liquid phases, with the lower aqueous phase accounting for 80.8% of the total volume. The SO₂ concentration ratio between the lower and upper aqueous phases was 3.24, and the absorbent absorbed 1.052 mol / mol of amine. The SO₂-rich phase was then desorbed and regenerated at a temperature of 106°C for 180 minutes. The SO₂ cycle absorption EQ was 0.366 mol / mol of amine, and the SO₂ desorption efficiency was 67%.

[0101] Compared to a homogeneous absorbent without n-butanol, this example reduced the amount of regenerated liquid by 17.8%, increased the circulating absorption capacity (EQ) by 25.4%, increased the desorption efficiency (DE) by 25.5%, and reduced the regeneration energy consumption (Q) by 17.8%. While the viscosity of the absorbent without n-butanol was 5.0 cP, the viscosity of the rich phase in this example was 6.08 cP, which is still relatively low.

[0102] By comparing Example 6 with Examples 8 to 9, it can be found that the greater the amount of phase change aid used in the phase change absorbent, the lower the SO2 load. This is because the acid will react with the organic amine, reducing the number of active absorption amines involved in the absorption, but increasing the circulating absorption capacity, reducing the amount of regeneration treatment liquid, and reducing the desorption energy consumption.

[0103] Example 10

[0104] An absorbent for SO₂ capture was prepared by mixing N,N-bis(2-hydroxypropyl)piperazine (HPP), N-hydroxyethylpiperazine (HEP), n-butanol, and water, followed by the addition of sulfuric acid. The absorbent contained 18% HPP by mass, 2% HEP by mass, 20% n-butanol by mass, 5.0% sulfuric acid by mass, and the remainder being water.

[0105] Simulated flue gas containing 9.1% SO₂ was passed through 100g of the absorbent at a flow rate of 1.5L / min, an absorption temperature of 40°C, and an absorption time of 180 minutes. After absorbing the SO₂, the absorbent formed a liquid-liquid two-phase system, with the lower aqueous phase accounting for 79.9% of the total volume. The SO₂ concentration ratio between the lower and upper aqueous phases was 7.23, and the absorbent absorbed 0.649mol / mol of amine. The SO₂-rich phase was then desorbed and regenerated at a temperature of 106°C and a regeneration time of 180 minutes. The SO₂ cycle absorption EQ was 0.50mol / mol of amine, and the SO₂ desorption rate was 85.6%.

[0106] Compared to a homogeneous absorbent without n-butanol, this embodiment reduced the amount of regenerated liquid by 20%, increased the circulating absorption capacity (EQ) by 23.8%, increased the desorption efficiency (DE) by 22.7%, and reduced the regeneration energy consumption (Q) by 22.9%. While the viscosity of the absorbent without n-butanol was 5.8 cP, the viscosity of the rich phase in this embodiment was 10.2 cP, still relatively low.

[0107] Example 11

[0108] An absorbent for SO2 capture was prepared by mixing N,N-bis(2-hydroxyethyl)piperazine (BHEP), N-hydroxyethylpiperazine (HEP), cyclohexanol, and water, followed by the addition of boric acid. The resulting absorbent contained 25.5% by mass of BHEP, 4.5% by mass of HEP, 30% by mass of cyclohexanol, 0.50% by mass of boric acid, and the remainder being water.

[0109] Simulated flue gas containing 11.2% SO₂ was passed through 100g of absorbent at a flow rate of 1.5L / min, with an absorption temperature of 40°C and an absorption time of 180 minutes. After absorbing the SO₂, the absorbent formed a liquid-liquid two-phase system, with the lower aqueous phase accounting for 76.0% of the total volume. The ratio of SO₂ concentrations in the lower and upper aqueous phases was 8.23, and the absorbent absorbed 1.1207mol / mol of amine. The SO₂-rich phase was then desorbed and regenerated at a temperature of 105°C and a regeneration time of 180 minutes. The SO₂ cycle absorption EQ was 0.53mol / mol of amine, and the SO₂ desorption rate was 82.3%.

[0110] Compared to a homogeneous absorbent without cyclohexanol, this example reduced the amount of regenerated liquid by 24%, increased the circulating absorption capacity (EQ) by 28.2%, increased the desorption efficiency (DE) by 20.8%, and reduced the regeneration energy consumption (Q) by 32.1%. While the viscosity of the absorbent without cyclohexanol was 11.2 cP, the viscosity of the rich phase in this example was 28.9 cP, which is still relatively low.

[0111] Example 12

[0112] An absorbent for SO2 capture was prepared by mixing N,N-bis(2-hydroxypropyl)piperazine (HPP), N-hydroxyethylpiperazine (HEP), 1,7-heptanediol, and water, followed by the addition of boric acid. The absorbent contained 25.5% by mass of HPP, 4.5% by mass of HEP, 30% by mass of 1,7-heptanediol, 0.5% by mass of boric acid, and the remainder being water.

[0113] Simulated flue gas containing 12.3% SO₂ was passed through 100g of absorbent at a flow rate of 1.5L / min, with an absorption temperature of 45°C and an absorption time of 180 minutes. After absorbing the SO₂, the absorbent formed a liquid-liquid two-phase system, with the lower aqueous phase accounting for 77.5% of the total volume. The SO₂ concentration ratio between the lower and upper aqueous phases was 9.45, and the absorbent absorbed 1.089mol / mol of amine. The SO₂-rich phase was then desorbed and regenerated at a temperature of 105°C and a regeneration time of 180 minutes. The SO₂ cycle absorption EQ was 0.55mol / mol of amine, and the SO₂ desorption rate was 80.2%.

[0114] Compared to a homogeneous absorbent without 1,7-heptanediol, the regeneration process liquid volume was reduced by 23%, the circulating absorption capacity (EQ) increased by 20.2%, the desorption efficiency (DE) increased by 25.6%, and the regeneration energy consumption (Q) decreased by 22.6%. The viscosity of the absorbent without 1,7-heptanediol was 12.1 cP, while the viscosity of the rich liquid phase in this example was 29.5 cP, which is still relatively low.

[0115] Example 13

[0116] An absorbent for SO2 capture was prepared by mixing N,N-bis(2-hydroxyethyl)piperazine (BHEP), N-hydroxyethylpiperazine (HEP), n-pentanol, and water, followed by the addition of boric acid. The resulting absorbent contained 24% by mass of BHEP, 6% by mass of HEP, 25% by mass of n-pentanol, 3.52% by mass of boric acid, and the remainder being water.

[0117] Simulated flue gas containing 11.2% SO₂ was passed through 100g of absorbent at a flow rate of 1.5L / min, with an absorption temperature of 25°C and an absorption time of 180 minutes. After absorbing the SO₂, the absorbent formed a liquid-liquid two-phase system, with the lower aqueous phase accounting for 83.6% of the total volume. The SO₂ concentration ratio between the lower and upper aqueous phases was 8.1, and the absorbent absorbed 0.8023mol / mol of amine. The SO₂-rich phase was desorbed and regenerated at a regeneration temperature of 105°C and a regeneration time of 180 minutes. The SO₂ cycle absorption EQ was 0.65mol / mol of amine, and the SO₂ desorption rate was 76%.

[0118] Compared to a homogeneous absorbent without n-pentanol, this example reduced the amount of regenerated liquid by 16%, increased the circulating absorption capacity (EQ) by 26.2%, increased the desorption efficiency (DE) by 20.8%, and reduced the regeneration energy consumption (Q) by 32.1%. While the viscosity of the absorbent without n-pentanol was 10.5 cP, the viscosity of the rich phase in this example increased to 27.5 cP, a slight but still relatively low increase.

[0119] Example 14 Cyclic Absorption and Desorption

[0120] An absorbent for SO2 capture was prepared by mixing N,N-bis(2-hydroxyethyl)piperazine (BHEP), N-hydroxyethylpiperazine (HEP), n-butanol, and water, followed by the addition of boric acid. The resulting absorbent contained 22.5% by mass of BHEP, 2.5% by mass of HEP, 25% by mass of n-butanol, 3.52% by mass of boric acid, and the remainder being water.

[0121] Simulated flue gas containing 8.0% SO₂ was passed through 100g of absorbent at a flow rate of 1.2L / min, an absorption temperature of 25°C, and an absorption time of 150 minutes. After absorbing the SO₂, the absorbent formed a liquid-liquid two-phase system, with the lower aqueous phase accounting for 77.3% of the total volume. The ratio of SO₂ concentrations in the lower and upper aqueous phases was 13.12, and the absorbent absorbed 1.103 mol / mol of amine. The SO₂-rich phase was then desorbed and regenerated at a temperature of 105°C and a regeneration time of 180 minutes. The SO₂ cycle absorption EQ was 0.615 mol / mol of amine, and the SO₂ desorption rate was 86.9%.

[0122] The desorbed and regenerated amine solution is mixed with the upper water phase and used for cyclic absorption. After four cycles of absorption, the lower water phase accounts for 79.2% of the total volume, the ratio of the lower and upper water phases to the SO2 concentration is 10.33, the SO2 absorption capacity of the absorbent is 0.905 mol / mol amine, the SO2 cycle absorption capacity EQ is 0.695 mol / mol amine, and the SO2 desorption rate is 98.1%.

[0123] Compared to a homogeneous absorbent without n-butanol, the regeneration process liquid volume was reduced by 21%, the circulating absorption capacity (EQ) increased by 25.8%, the desorption efficiency (DE) increased by 35.6%, and the regeneration energy consumption (Q) decreased by 44.1%. The viscosity of the absorbent without n-butanol was 8.5 cP, while the viscosity of the rich liquid phase in this example was 28.6 cP, which is still relatively low.

[0124] The circulation load of the liquid-liquid phase change absorbent is greater than that of the homogeneous absorbent, indicating that the liquid-liquid phase change absorbent of the present invention has good regeneration performance and can significantly reduce regeneration energy consumption, which fully demonstrates that the aqueous phase change absorbent has broad application prospects.

Claims

1. An organic amine-alcohol aqueous SO2 liquid-liquid phase change absorbent, characterized in that: The SO2 liquid-liquid phase change absorbent comprises the following components: 15-30 parts by weight of piperazine organic amine, 15-45 parts by weight of phase separation agent and 0.1-5 parts by weight of phase change auxiliary agent, Wherein, the piperazine organic amine is selected from one or more of N-hydroxyethylpiperazine, N,N-bis(2-hydroxyethyl)piperazine, N,N-bis(2-hydroxypropyl)piperazine or N-hydroxyethyl-N-hydroxypropylpiperazine; the phase separator is selected from one or more of n-butanol, n-pentanol, sec-pentanol, cyclohexanol or 1,7-heptanediol; the phase change agent is selected from one or more of sulfuric acid, phosphoric acid, hydrochloric acid or boric acid, Among them, the SO2 liquid-liquid phase change absorbent spontaneously forms liquid-liquid two phases after absorbing SO2, and the volume of the lower phase accounts for 20% to 85% of the total liquid phase volume ratio.

2. The SO2 liquid-liquid phase-change absorbent according to claim 1, wherein: The piperazine organic amine contains at least N-hydroxyethylpiperazine.

3. The method for preparing the organic amine-alcohol aqueous SO2 liquid-liquid phase change absorbent according to claim 1 or 2, characterized in that: The steps include: The raw materials including piperazine organic amine, phase separation agent and phase change auxiliary agent are added into water and dissolved to obtain the SO2 liquid-liquid phase change absorbent.

4. A method for capturing SO2, characterized in that: The steps include: (1) Absorption process: mixing the SO2-containing gas with the SO2 liquid-liquid phase-change absorbent according to claim 1 or 2; after the absorption reaction, the absorption liquid is rapidly separated into a lower aqueous phase and an upper aqueous phase; (2) Desorption process: The lower aqueous phase is heated for desorption, and the lean liquid obtained after desorption is mixed with the upper aqueous phase obtained in step (1) and recycled as an absorbent.

5. The method according to claim 4, wherein: The temperature of the absorption process is 20-50°C, and the temperature of the desorption process is 80-120°C.

6. The method according to claim 5, wherein: The temperature of the desorption process is 100-110°C.

7. Use of the organic amine-alcohol aqueous SO2 liquid-liquid phase change absorbent according to claim 1 or 2 in the field of flue gas desulfurization.