CN114159946A - Absorbent for removing sulfur dioxide in flue gas and application thereof - Google Patents

Abstract

The invention provides an absorbent for removing sulfur dioxide in flue gas, which comprises 25-30 wt% of main absorption components, 0.01-0.1 wt% of heat stable salt inhibitor and the balance of water; the main absorption component is a mixture of 4,4'- (1, 2-ethylidene) dimorpholine and 4,4' - (oxybis (methylene)) dimorpholine. The absorbent has the characteristics of strong absorption performance, large absorption capacity, low cost, good regeneration effect, small generation amount of heat stable salt, equipment corrosion delay and the like, and better solves the defects of the existing sulfur dioxide removal technology. The invention also provides a method for circularly removing sulfur dioxide in flue gas by using the absorbent. The method of the invention realizes the operation in the environment with higher pH value, and reduces the requirement of equipment material; realizes the absorption and the desulfurization at higher temperature, thereby reducing the energy consumption of the process.

Description

Absorbent for removing sulfur dioxide in flue gas and application thereof

Technical Field

The invention relates to the energy-saving and environment-friendly industry, belongs to the field of separation treatment of waste gas, and particularly relates to an absorbent for removing sulfur dioxide gas in flue gas and application thereof.

Background

Sulfur dioxide (SO)₂) Is the simplest sulfur oxide in nature and is harmful to human health. SO (SO)₂The acid rain acts with water vapor in the air to form acid rain, and the acid rain environment can acidify soil and water to different degrees; in addition, SO is inhaled for a long time₂Can affect the health of the human body.

At present, the flue gas SO₂The removal method can be divided into a dry method, a semi-dry method and a wet method. The dry method and the semi-dry method have the disadvantages of low desulfurization efficiency, high investment and operation cost, a large amount of sulfate byproducts and the like. The wet desulphurization has great advantages in the aspects of desulphurization efficiency, investment and energy consumption, and SO₂Can be recycled.

In the prior art, there have been some researches on absorbents for removing sulfur dioxide from flue gas. Patent document CN107019996A of china petroleum engineering construction ltd discloses an application of a lactam derivative as an absorbent containing a desulfurization enhancing additive, an activating agent, a cosolvent, an antioxidant and a corrosion inhibitor. Patent document CN105848757B by kangshi technologies, canada, discloses the use of an aqueous absorbent containing a water-soluble half-salt of a diamine and a high concentration of a Heat Stable Salt (HSS), which has the problems of rapid formation of heat stable salts and a large amount of amine-containing wastewater formed by online desalination. Patent document CN105833667A of sichuan Kangshengyuan company discloses an absorbent mainly comprising hydroxyethyldiamine sulfate, wherein the molar ratio of the main agent sulfate to the hydroxyethyldiamine is 0.4 to 1.2. These prior absorbents have the limitations of high cost, complex operation, short life cycle, and high heat stability salt content.

Therefore, there is a need to provide a new absorbent for removing sulfur dioxide from flue gas, so as to improve the removal efficiency and reduce the cost.

Disclosure of Invention

The invention aims to provide an absorbent and a technology for removing sulfur dioxide in flue gas under the conditions of higher temperature and higher pH value, thereby overcoming the defects of the existing wet-method sulfur dioxide removal technology and realizing the upgrading of energy conservation and emission reduction of a flue gas desulfurization device.

The purpose of the invention is realized by the following technical scheme:

firstly, providing an absorbent for removing sulfur dioxide in flue gas, wherein the absorbent comprises, by weight, 25% -30% of a main absorption component, 0.01% -0.1% of a heat-stable salt inhibitor and the balance of water; the main absorption component is a mixture of 4,4'- (1, 2-ethylidene) dimorpholine and 4,4' - (oxybis (methylene)) dimorpholine.

In the preferred absorbent of the present invention, the main absorbent component is a mixture of 4,4'- (1, 2-ethylidene) dimorpholine and 4,4' - (oxybis (methylene)) dimorpholine in an equal mass ratio.

In the preferred absorbent of the present invention, the thermostable salt inhibitor is selected from one or more of L- (+) -threose-type-2, 3,4,5, 6-pentahydroxy-2-hexenoic acid-4-lactone sodium, butylated hydroxyanisole, 4-butylamino-2, 2,6, 6-tetramethylpiperidine, 4-hydroxy-2, 2,6, 6-tetramethylpiperidine-1-oxyl, sodium hypophosphite and calcium hypophosphite; more preferably 4-butylamine-2, 2,6, 6-tetramethylpiperidine.

In a preferable embodiment of the present invention, the pH of the absorbent is 9.0 to 11.0, and more preferably 9.5 to 10.5.

In the preferred absorbent of the present invention, the main absorbent component accounts for 25% by weight.

In the preferred absorbent, the heat-stable salt inhibitor accounts for 0.01-0.05% by weight; preferably 0.01% or 0.05%.

The most preferred absorbent of the present invention comprises, by weight percent, 25% of the main absorbent component, 0.05% of the heat stable salt inhibitor, and the balance water; the main absorption component is a mixture of 4,4'- (1, 2-ethylidene) dimorpholine and 4,4' - (oxybis (methylene)) dimorpholine according to equal mass ratio; the heat stable salt inhibitor is 4-butylamine-2, 2,6, 6-tetramethylpiperidine.

On the basis, the invention also provides a method for circularly removing sulfur dioxide in flue gas by using the absorbent, which comprises the following steps:

1) mixing and contacting the flue gas to be treated containing sulfur dioxide with the absorbent at the temperature of 25-60 ℃ and under the condition that the pH value is 4-11 to obtain rich solution after absorption and dischargeable flue gas;

2) heating the absorbed rich solution obtained in the step 1) to 80-120 ℃, desorbing and regenerating to obtain sulfur dioxide gas and barren solution;

3) the barren liquor obtained in the step 2) is used as an absorbent in the step 1).

In the preferable method of the invention, the flue gas to be treated in 1) is mixed and contacted with the absorbent at 35-50 ℃; most preferably 40-50 deg.C.

In the method, the mixed contact pH condition of the flue gas to be treated containing sulfur dioxide and the absorbent is 4-11, the pH range is usually the pH dynamic change range of the whole contact process of the flue gas to be treated and the absorbent, namely, the pH value of the absorbent is about 9-11 in the initial contact process, the pH value of the absorbent is gradually reduced along with the extension of the contact time due to the accumulation of the sulfur dioxide in the flue gas absorbed by the absorbent, but the final pH value is not lower than 4. In the preferable method, the flue gas to be treated in 1) is mixed and contacted with the absorbent in the invention at a pH value of 4.0-10.5; more preferably, the pH value is 4.5-10.5; most preferably at a pH of 6 to 10.5.

In the preferred method of the invention, the mixing contact in 1) is that the flue gas to be treated and the absorbent in the invention are in countercurrent flow contact at a gas-liquid volume ratio of 1000: 1.

In the preferable method of the invention, the temperature for heating and regenerating the rich solution in the step 2) is 100-115 ℃.

In a further preferred method, the heating regeneration is heating by using steam, and the ratio of the steam for regeneration in the step 2) to the flue gas to be treated in the step 1) (kg/Nm)³) Is 0.25:1 to 0.6:1, preferably 0.25: 1.

In a most preferred embodiment of the present invention, the method for circularly removing sulfur dioxide from flue gas by using the absorbent of the present invention comprises:

1) introducing the flue gas containing sulfur dioxide to be treated and the absorbent into an absorption tower from the lower part and the middle part respectively, and carrying out reverse flow contact at the temperature of 50 ℃ and under the condition of pH 4.5-10.5 according to the gas-liquid volume ratio of 1000:1 to obtain the absorbed rich liquid and the dischargeable flue gas; discharging the rich liquid from the bottom of the absorption tower after absorption; the dischargeable flue gas is discharged from the top of the absorption tower;

2) pumping the absorbed rich liquid discharged from the bottom of the absorption tower in the step 1) into the upper part of a regeneration tower, introducing water vapor from the lower part of the regeneration tower, heating the absorbed rich liquid to 100-115 ℃ by the water vapor in the regeneration tower, desorbing and regenerating to obtain sulfur dioxide gas and barren liquor;

3) discharging the sulfur dioxide gas obtained in the step 2) from the top of the regeneration tower and introducing the sulfur dioxide gas to a sulfur production device; and (3) discharging the barren solution from the bottom of the regeneration tower, pumping the barren solution into the middle part of the absorption tower in the step 1) and recycling the barren solution as an absorbent.

Compared with the prior art, the renewable absorbent provided by the invention can be regenerated in a higher pH value environment, which is a new breakthrough of the solvent. The operation under the environment of higher pH value is realized, and the requirement of equipment material is reduced; realizes the absorption and the desulfurization at higher temperature, thereby reducing the energy consumption of the process. In addition, the solvent has the characteristics of strong absorption performance, large absorption capacity, low cost, good regeneration effect, small heat-stable salt generation amount, equipment corrosion delay and the like, well overcomes the defects of the existing sulfur dioxide removal technology, realizes energy conservation and emission reduction and resource recycling of a flue gas desulfurization device, and conforms to the strategy of sustainable development of China.

Drawings

FIG. 1 shows SO removal of flue gas used in examples 4 and 5₂The process flow diagram of (1).

The reference numerals are explained below:

1. a venturi tube; 2. a quench tower; 3. An absorption tower; 4. a rich liquor pump; 5. a lean-rich liquid heat exchanger; 6. A regeneration tower; 7. A barren liquor pump; 8. A lean liquid cooler.

Detailed Description

The absorbent for removing sulfur dioxide from flue gas according to the present invention comprises the following examples, which further illustrate the present invention but do not limit the present invention in any way.

The absorbent for removing sulfur dioxide from flue gas and the test method provided by the present invention are described in detail with reference to the following examples, but they should not be construed as limiting the scope of the present invention.

Example 1:

an absorbent for removing sulfur dioxide from flue gas contains 12.5 wt% of 4,4'- (1, 2-ethylidene) dimorpholine and 12.5 wt% of 4,4' - (oxybis (methylene)) dimorpholine as main absorption components, and also contains 0.05 wt% of 4-butylamine-2, 2,6, 6-tetramethylpiperidine as heat stable salt inhibitor, and the balance of water, and the pH of the absorbent is 10.5.

Example 2:

an absorbent for removing sulfur dioxide from flue gas contains 12.5 wt% of 4,4'- (1, 2-ethylidene) dimorpholine and 12.5 wt% of 4,4' - (oxybis (methylene)) dimorpholine as main absorption components, and also contains 0.01 wt% of 4-butyl amino-2, 2,6, 6-tetramethyl piperidine as heat stable salt inhibitor, and the balance of water, and the pH of the absorbent is 10.2.

Example 3:

the absorbent for removing sulfur dioxide from flue gas contains 15 wt% of 4,4'- (1, 2-ethylidene) dimorpholine and 15 wt% of 4,4' - (oxybis (methylene)) dimorpholine as main absorption components, and also contains 0.05 wt% of 4-butylamine-2, 2,6, 6-tetramethylpiperidine as heat stable salt inhibitor, and the balance of water, and the pH value of the absorbent is 10.

Comparative example 1:

an absorbent for removing sulfur dioxide in flue gas contains 25 wt% of 4,4' - (oxybis (methylene)) dimorpholine as a main absorption component, 0.05 wt% of 4-butylamine-2, 2,6, 6-tetramethylpiperidine as a heat stable salt inhibitor, and the balance of water.

Comparative example 2:

an absorbent for removing sulfur dioxide in flue gas contains 25 wt% of 4,4' - (1, 2-ethylidene) dimorpholine as a main absorption component, 0.05 wt% of 4-butylamine-2, 2,6, 6-tetramethylpiperidine as a heat stable salt inhibitor and the balance of water.

Comparative example 3:

the absorbent for removing sulfur dioxide from flue gas contains 5 wt% of 4,4'- (1, 2-ethylidene) dimorpholine and 5 wt% of 4,4' - (oxybis (methylene)) dimorpholine as main absorption components, and also contains 0.05 wt% of 4-butylamine-2, 2,6, 6-tetramethylpiperidine as heat stable salt inhibitor, and the balance of water.

Comparative example 4:

the absorbent for removing sulfur dioxide from flue gas contains 7.5 wt% of 4,4'- (1, 2-ethylidene) dimorpholine and 7.5 wt% of 4,4' - (oxybis (methylene)) dimorpholine as main absorption components, and also contains 0.05 wt% of 4-butylamine-2, 2,6, 6-tetramethylpiperidine as heat stable salt inhibitor, and the balance of water.

Comparative example 5:

the absorbent for removing sulfur dioxide from flue gas contains 20 wt% of 4,4'- (1, 2-ethylidene) dimorpholine and 20 wt% of 4,4' - (oxybis (methylene)) dimorpholine as main absorption components, and also contains 0.05 wt% of 4-butylamine-2, 2,6, 6-tetramethylpiperidine as heat stable salt inhibitor, and the balance of water.

Comparative example 6:

an absorbent for removing sulfur dioxide in flue gas contains 12.5 wt% of 4,4'- (1, 2-ethylidene) dimorpholine and 12.5 wt% of 4,4' - (oxybis (methylene)) dimorpholine as main absorption components, and also contains 0.05 wt% of L- (+) -threose-type-2, 3,4,5, 6-pentahydroxy-2-hexenoic acid-4-lactone sodium as a heat stable salt inhibitor, and the balance of water.

Comparative example 7:

an absorbent for removing sulfur dioxide from flue gas contains 12.5 wt% of 4,4'- (1, 2-ethylidene) dimorpholine and 12.5 wt% of 4,4' - (oxybis (methylene)) dimorpholine as main absorption components, and the balance of water.

Comparative example 8:

an absorbent for removing sulfur dioxide in flue gas comprises, by weight, 25% of bis-hydroxyethyl piperazine sulfate as a main absorption component, and the balance of water, wherein the pH value of the absorbent is 5.2.

Comparative example 9:

an absorbent for removing sulfur dioxide in flue gas comprises 25 wt% of N-hydroxyethyl piperazine sulfate as a main absorption component, the balance of water, and the pH value of the absorbent is 5.2.

Comparative example 10:

an absorbent for removing sulfur dioxide in flue gas comprises 25 wt% of 4,4' -methylenedimorpholine as a main absorption component, the balance of water, and the pH value of the absorbent is 10.

Comparative example 11:

an absorbent for removing sulfur dioxide in flue gas comprises 25 wt% of 1,2' -dipiperidine ethane as a main absorption component, the balance of water, and the pH value of the absorbent is 10.

Experimental example 1:

the optimization test is carried out by adopting a bubbling type small absorption device, and a coulometer is used for tracking SO in the purified gas after absorption₂The content of (c) varies.

The absorption process of the raw material gas comprises the following steps: adding SO₂、CO₂、O₂、N₂The 4 gases are proportionally prepared into simulated flue gas required by experiments, a bubbler filled with absorbent is placed in a constant-temperature water bath kettle and enters a flue gas absorption device at a certain flow rate, and SO of the absorbed gases is measured at regular intervals₂And (4) concentration. By measuring SO of the absorbed gas₂Concentration, reflecting the absorptive properties of the agent. SO of absorbed gas₂The smaller the concentration, the better the absorption properties of the agent.

The above experiments were carried out with the three absorbents of example 1, comparative example 1 and comparative example 2, respectively, and the results of the experimental tests are given in table 1 below:

table 1: desulfurization test results of absorbents of different main absorption components

As shown in table 1 above, the main absorbent component is preferably a mixture of 4,4'- (1, 2-ethylidene) dimorpholine and 4,4' - (oxybis (methylene)) dimorpholine in a mass ratio of 1:1, and the mixture has the highest desulfurization efficiency and strong absorbent purification ability when used as the main absorbent component, and can realize ultra-clean zero discharge.

Experimental example 2:

desulfurization experiments were performed using the experimental apparatus and analytical method in experimental example 1, using the absorbents of example 1, example 3, comparative example 4, and comparative example 5. The results of the experiment are shown in table 2 below:

table 2: comparison of absorption Properties of Main absorbent component at different concentrations

As shown in table 2 above, the absorbent desulfurization efficiency gradually increases as the concentration of the main absorbent component increases, but when the concentration of the main absorbent component is further increased, the desulfurization efficiency rather decreases. Therefore, when the concentration of the main absorption component is 25-30%, the desulfurization efficiency is highest, the purification capacity of the absorbent is strong, and ultra-clean zero emission can be realized.

Experimental example 3:

the heat stable salt suppression experiment was performed using the experimental apparatus in experimental example 1, using the absorbents of example 1, comparative example 6 and comparative example 7 as the absorbent lean solution. Analysis of SO in absorbent barren solutions using ion chromatography₄ ^2-And (4) concentration. After the absorbent is absorbed and regenerated for a long time, SO₂The resulting sulfite or bisulfite is oxidized to SO₄ ^2-，SO₄ ^2-Reacting with an absorbent to produce a thermally stable ammonium salt. SO in barren solution₄ ^2-The concentration of (A) is in direct proportion to the concentration of the heat stable salt, and the concentration of the heat stable salt can be directly reflected.

Table 3: comparison of different thermostable salt inhibitors

As shown in Table 3 above, the thermostable salt inhibitor is preferably 4-butylamine-2, 2,6, 6-tetramethylpiperidine, which has the highest ability to inhibit thermostable salt.

Example 4:

the sulfur tail gas of a petrochemical company is burnt to convert various sulfides in the tail gas into SO₂Then absorbing and regenerating with absorbent to obtain SO₂Returning to the sulfur production furnace to produce sulfur. SO in raw gas₂ 44000mg/Nm³At a flow rate of 30000Nm³The flow rate of the absorbent is 30000L/h, the absorption temperature is 40 ℃, and the gauge pressure is 1.006kPa, the process flow shown in the attached figure 1 is adopted:

after the sulfur flue gas after incineration sequentially passes through the venturi tube 1 and the quench tower 2 to be washed and cooled, the sulfur flue gas enters the absorption tower 3 from the lower part of the absorption tower 3 and is in countercurrent contact with an absorbent entering the absorption tower 3 from the middle part, and the flue gas meeting the emission requirement after absorption is emitted in the upper air at the top of the absorption tower 3. Absorption of SO₂The rich absorption liquid is discharged from the bottom of the absorption tower 3, pumped into a lean rich liquid heat exchanger 5 by a rich liquid pump for heat exchange and temperature rise, and then enters a regeneration tower 6 from the upper part for regeneration, steam is adopted at the bottom of the regeneration tower 6 as a heat source, and SO desorbed from the tower top is desorbed₂Together with water vapour, separated by cooling, SO₂The gas is sent to a sulfur production furnace to participate in sulfur production reaction. The condensed water is pumped to the top of the regeneration column 6 by a reflux pump. SO desorption in regeneration tower 6₂And the lean solution is discharged from the bottom of the regeneration tower 6, pumped to the lean-rich solution heat exchanger 5 through a lean solution pump 7 for heat exchange, cooled through a lean solution cooler 8 and then enters the middle part of the absorption tower 3 again. The absorbent circulates back and forth to form continuous absorption and desorption SO₂The process of (1).

The absorbent used was the absorbent of example 2.

The relevant parameters are shown in table 4:

TABLE 4

As can be seen from Table 4, the absorbent formulation of example 2 and the desulfurization process of this example provide high desulfurization efficiency and produce SO₂High gas content and stable quality.

Example 5:

real conditions were simulated using pilot plants like the absorber and regenerator columns of figure 1.

The experimental conditions are as follows: composition of raw material gas SO₂（44000mg/Nm³）、O₂（2.5%）、N₂The flow rate is 400L/h, the circulation amount of the absorbent is 0.4L/h, the corresponding gas-liquid ratio is 1000:1, the preheating temperature of the barren solution and the feed gas is 40 ℃, and the purified gas is lower than 40mg/Nm in the experiment³Set as the emission level. Desorbing by using low-pressure steam, wherein the flow rate of the steam is 100-200 g/h. The regeneration tower bottom/tower top temperature is 115 ℃/102 ℃; the height-diameter ratio of the absorption tower is about 11.

The relevant parameters are as follows:

table 5: comparison of regeneration energy consumption of different absorbents

The test was carried out using a mixed solution of 4,4'- (1, 2-ethylidene) dimorpholine and 4,4' - (oxybis (methylene)) dimorpholine formulated in equal proportions, and a solution of 4,4 '-methylenedimorpholine and a solution of 1,2' -dipiperidine ethane alone, respectively. As shown in Table 5, the formulations of the mixed solutions were 50% and 37.5% lower than those of the 4,4 '-methylenedimorpholine solution and the 1,2' -dipiperidinoethane solution, respectively, in terms of energy consumption for regeneration.

Example 6:

the experimental conditions in example 4 were used to change the lean liquid and feed gas preheating temperatures to 45 ℃ and 50 ℃ using the absorbents of example 1, comparative example 10, and comparative example 11, respectively.

The relevant parameters are shown in the following tables 6 and 7:

table 6: comparison of the absorption Properties at 45 ℃ of different absorbents

Table 7: comparison of the absorption Properties at 50 ℃ of different absorbents

As shown in tables 6 and 7, after the lean solution and the feed gas are preheated to 45 ℃ and 50 ℃, the absorbent of the invention can still maintain good absorption performance at higher temperature and can still realize ultra-clean zero discharge. This also contributes to saving energy in the actual production process.

Experimental example 4:

the corrosion rates of carbon steels in comparative example 8, comparative example 9 and example 1 were determined with reference to the test method for corrosion rates in GB/T39534-.

The relevant parameters are as follows:

table 8: comparison of corrosion rates of different absorbents for carbon steels

As shown in Table 8 above, the absorbent of the present invention is less corrosive to equipment than comparative examples 8 and 9.

Claims (10)

1. An absorbent for removing sulfur dioxide in flue gas is characterized in that: the absorption material comprises, by weight, 25-30% of a main absorption component, 0.01-0.1% of a heat-stable salt inhibitor and the balance of water; the main absorption component is a mixture of 4,4'- (1, 2-ethylidene) dimorpholine and 4,4' - (oxybis (methylene)) dimorpholine.

2. The absorbent of claim 1, wherein: the main absorption component is a mixture of 4,4'- (1, 2-ethylidene) dimorpholine and 4,4' - (oxybis (methylene)) dimorpholine according to equal mass ratio, and the main absorption component accounts for 25% by weight.

3. The absorbent of claim 1, wherein: the heat stable salt inhibitor is selected from any one or a mixture of two of L- (+) -threose type-2, 3,4,5, 6-pentahydroxy-2-hexenoic acid-4-lactone sodium or 4-butylamine-2, 2,6, 6-tetramethylpiperidine.

4. An absorbent according to any one of claims 1 to 3, characterized in that: the pH value of the absorbent is 9.0-11.0.

5. An absorbent according to any one of claims 1 to 3, characterized in that: the heat-stable salt inhibitor accounts for 0.01-0.05% by weight.

6. An absorbent for removing sulfur dioxide in flue gas is characterized in that: the water-soluble absorption material comprises 25 percent of main absorption component, 0.05 percent of heat-stable salt inhibitor and the balance of water by weight percentage; the main absorption component is a mixture of 4,4'- (1, 2-ethylidene) dimorpholine and 4,4' - (oxybis (methylene)) dimorpholine according to equal mass ratio; the heat stable salt inhibitor is 4-butylamine-2, 2,6, 6-tetramethylpiperidine; the pH value of the absorbent is 9.5-10.5.

7. A method for circularly removing sulfur dioxide in flue gas by using the absorbent of any one of claims 1 to 6, comprising the following steps:

1) mixing and contacting the flue gas to be treated containing sulfur dioxide with the absorbent as defined in any one of claims 1 to 6 at 25-60 ℃ and under the condition of pH 4-11;

2) heating the absorbed rich solution obtained in the step 1) to 80-120 ℃, desorbing and regenerating to obtain sulfur dioxide gas and barren solution;

3) the barren liquor obtained in the step 2) is used as an absorbent in the step 1).

8. The method of claim 7, wherein: 1) the mixed contact is that the flue gas to be treated and the absorbent of any one of claims 1-6 are in countercurrent flow contact at the gas-liquid volume ratio of 1000: 1.

9. The method of claim 7, wherein: the heating regeneration is heating by using water vapor, and the ratio of the water vapor for regeneration in the step 2) to the flue gas to be treated in the step 1)(kg/Nm³) Is 0.25:1 to 0.6: 1.

10. A method for circularly removing sulfur dioxide in flue gas by using the absorbent of any one of claims 1-6, which is characterized by comprising the following steps:

1) introducing the flue gas containing sulfur dioxide to be treated and the absorbent of any one of claims 1-6 into an absorption tower from the lower part and the middle part respectively, and carrying out countercurrent flow contact at the temperature of 40 ℃ and under the condition of pH 4.5-10.5 according to the gas-liquid volume ratio of 1000:1 to obtain the absorbed rich solution and the dischargeable flue gas; discharging the rich liquid from the bottom of the absorption tower after absorption; the dischargeable flue gas is discharged from the top of the absorption tower;

2) pumping the absorbed rich liquid discharged from the bottom of the absorption tower in the step 1) into the upper part of a regeneration tower, introducing water vapor from the lower part of the regeneration tower, and leading the ratio (kg/Nm) of the water vapor to the flue gas to be treated in the step 1)³) The ratio of the absorbed rich solution to the sulfur dioxide gas is 0.25:1, and the absorbed rich solution is heated to 100-115 ℃ by water vapor in a regeneration tower for desorption and regeneration to obtain sulfur dioxide gas and barren solution;

3) discharging the sulfur dioxide gas obtained in the step 2) from the top of the regeneration tower and introducing the sulfur dioxide gas to a sulfur production device; and (3) discharging the barren solution from the bottom of the regeneration tower, pumping the barren solution into the middle part of the absorption tower in the step 1) and recycling the barren solution as an absorbent.

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