JP2022160860A - Acid gas treatment system and method - Google Patents

Abstract

To provide an acidic gas treatment system capable of, when removing oxygen from acidic gas absorption liquid (rich absorption liquid) absorbing acidic gas, suppressing removal of active ingredients in the acidic gas absorption liquid and acidic gases other than oxygen, such as carbon dioxide.SOLUTION: In one embodiment, an acidic gas treatment system comprises: an absorber 1 that makes acidic gas absorption liquid L absorb acidic gas in exhaust gas G0; a regenerator 61 that dissipates the acidic gas from the acidic gas absorption liquid L (R) discharged from the absorber 1, and discharges the acidic gas from the acidic gas absorption liquid dissipating the acidic gas and gas containing the dissipated acidic gas; and an oxygen remover 42 disposed between the absorber 1 and the regenerator 61. The oxygen remover 42 having a first space and a second space divided by a membrane 43, while sending the acidic gas absorption liquid L (R) discharged from the absorber 1 to the regenerator 61 side through the first space, makes the gas containing oxygen in the acidic gas absorption liquid L (R) move from the acidic gas absorption liquid which is passing through the first space to the second space through the membrane 43.SELECTED DRAWING: Figure 1

Description

Embodiments of the present invention relate to acid gas treatment systems and methods.

For example, carbon dioxide generated by burning fossil fuels is said to be the main cause of global warming due to the greenhouse effect. Large-scale sources of carbon dioxide include, for example, thermal power plants and ironworks. Carbon dioxide is contained in exhaust gases emitted from such sources and is emitted to the atmosphere along with the exhaust gases.

Recently, the technology for removing carbon dioxide from the exhaust gas as described above, specifically carbon dioxide capture and storage technology (CCS: Carbon Dioxide Capture and Storage) has attracted attention. If carbon dioxide is removed from the exhaust gas to suppress its release into the atmosphere, it will be possible to efficiently remove the cause of global warming.

As an example of CCS, focusing on the point that carbon dioxide in the exhaust gas is an acidic gas component, by bringing the exhaust gas and an acidic gas absorbing solution (hereinafter abbreviated as absorbing solution) into gas-liquid contact, There is a method of absorbing the acid gas component and removing the acid gas component from the exhaust gas. As the absorption liquid, for example, a solution containing an active ingredient such as an amino group-containing compound (amine compound) is used.

A system using the above method has already been put into practical use. and a regenerator for heating the absorbent that has absorbed the acid gas to diffuse the acid gas component from the absorbent. This system is generally adapted to reuse the absorbent regenerated in the regenerator in the absorber, and the absorbent is circulated in the system between the absorber and the regenerator.

In addition to carbon dioxide, the exhaust gas treated by the system as described above usually contains components such as nitrogen and oxygen. In this case, when the exhaust gas and the absorbing liquid are brought into contact with each other, not only carbon dioxide but also oxygen can be absorbed by the absorbing liquid.

However, when oxygen is absorbed into the absorbent, the oxygen may cause corrosion of various devices. Therefore, it is desirable to prevent oxygen from being absorbed by the absorbing liquid or to be able to remove oxygen from the absorbing liquid.

As a method for removing the oxygen absorbed by the absorbing liquid, there is a technique of contacting the absorbing liquid that has absorbed carbon dioxide, which is a rich absorbing liquid, with a gas that does not contain oxygen, and reducing the pressure of the absorbing liquid that has absorbed carbon dioxide. , techniques for removing and degassing oxygen from absorption liquids are known.

However, the technique of contacting an oxygen-free gas with a rich absorbent requires a large amount of oxygen-free gas. In addition, active ingredients such as amine-based compounds can migrate from the rich absorbent to oxygen gas, and carbon dioxide can also migrate to oxygen-free gas. As such, processing steps may be required, such as recovery of the active ingredient and carbon dioxide from the oxygen-free gas. Therefore, there is a possibility that the efficiency of the carbon dioxide recovery process may be lowered.

In the removal of oxygen by reducing pressure, oxygen can be removed from the rich absorbing liquid by reducing pressure. In this case as well, not only oxygen but also active ingredients such as amine compounds and carbon dioxide can be removed from the rich absorbing liquid. . Therefore, in this case as well, there is a possibility that the efficiency of the carbon dioxide recovery process will be lowered.

Japanese Patent Application Laid-Open No. 2001-19416 Japanese Patent Application Laid-Open No. 2001-25628

Therefore, the problem to be solved by the present invention is that when removing oxygen from an acidic gas absorbing liquid (rich absorbing liquid) that has absorbed acidic gas, the active ingredients of the acidic gas absorbing liquid and acidic gases other than oxygen such as carbon dioxide are removed. An object of the present invention is to provide an acid gas treatment system and method capable of suppressing the removal of .

In one embodiment, an acidic gas treatment system is configured such that an acidic gas-containing gas and an acidic gas-absorbing liquid are brought into contact with each other, and the acidic gas-absorbing liquid that has absorbed the acidic gas from the acidic gas-containing gas and the acidic gas that has been removed from the acidic gas-containing gas. an absorber for discharging the acidic gas-containing gas discharged from the absorber, the acidic gas-absorbing liquid that diffuses the acidic gas from the acidic gas-absorbing liquid discharged from the absorber, and the acidic gas-absorbing liquid that diffuses the acidic gas; and a regenerator for discharging a gas containing the acidic gas, and an oxygen remover provided between the absorber and the regenerator. The oxygen remover has a first space and a second space partitioned by a membrane, and sends the acidic gas-absorbing liquid discharged from the absorber through the first space to the regenerator side. and moving the oxygen-containing gas in the acidic gas-absorbing liquid from the acidic gas-absorbing liquid passing through the first space to the second space through the membrane.

In one embodiment, the method for treating an acidic gas includes bringing an acidic gas-containing gas and an acidic gas-absorbing liquid into contact with each other, the acidic gas-absorbing liquid absorbing the acidic gas from the acidic gas-containing gas, and removing the acidic gas from the acidic gas-containing gas. a removal step of removing oxygen-containing gas from the acidic gas-absorbing liquid discharged in the absorption step; a regeneration step of diffusing the acidic gas and discharging the acidic gas absorbing liquid from which the acidic gas has been diffused and the gas containing the diffused acidic gas. In the removing step, the oxygen-containing gas contained in the acidic gas absorbing liquid is passed through the first space of the first space and the second space partitioned by a membrane while the acidic gas absorbing liquid discharged in the absorbing step is passed through the first space. from the acidic gas absorbing liquid passing through the first space through the membrane to the second space.

According to the present invention, when oxygen is removed from the acidic gas absorbing liquid (rich absorbing liquid) that has absorbed acidic gas, the active ingredients of the acidic gas absorbing liquid and acidic gases other than oxygen such as carbon dioxide are removed. can be suppressed.

1 illustrates an acid gas treatment system according to one embodiment; FIG. FIG. 2 is a schematic cross-sectional view of an oxygen remover provided in the acid gas treatment system shown in FIG. 1;

An embodiment will be described in detail below with reference to the accompanying drawings.

An acid gas treatment system S according to one embodiment shown in FIG. 1 is configured as a carbon dioxide recovery system as an example. The acid gas treatment system S separates and recovers carbon dioxide from the exhaust gas G0 containing carbon dioxide, which is an acid gas-containing gas.

<Acid gas treatment system>
First, the overall configuration of the acid gas treatment system S will be described.

As shown in FIG. 1 , the acid gas treatment system S includes an absorber 1 and a regenerator 61 . The absorber 1 brings the flue gas G0 flowing from the flue gas line 11 into contact with the acidic gas absorbing liquid L (hereinafter abbreviated as absorbing liquid), and causes the absorbing liquid L to absorb carbon dioxide. The absorber 1 includes an absorbent L (R) that is a rich absorbent that has absorbed carbon dioxide from the acidic gas-containing gas G0, an absorber discharge gas G1 that is an acidic gas-containing gas from which carbon dioxide has been removed, to discharge.

The regenerator 61 receives the rich absorbent L(R) discharged from the absorber 1 as described above, and diffuses carbon dioxide from the rich absorbent L(R). Then, the regenerator 61 discharges an absorbent L, which is a lean absorbent from which carbon dioxide has been diffused, and a regenerator exhaust gas G2 containing carbon dioxide. In the acid gas treatment system S, the absorbent L, which has been regenerated by dispersing carbon dioxide in the regenerator 61 as described above, is discharged from the regenerator 61 and supplied to the absorber 1 . That is, the absorbent L circulates between the absorber 1 and the regenerator 61 and is repeatedly used in the system.

The absorption liquid L is, for example, an amine-based aqueous solution containing an amine-based compound (amino group-containing compound) and water. Examples of amine compounds include primary amines such as monoethanolamine and 2-amino-2-methyl-1-propanol, secondary amines such as diethanolamine and 2-methylaminoethanol, and triethanol. amines, tertiary amines such as N-methyldiethanolamine, polyethylenepolyamines such as ethylenediamine, triethylenediamine, diethylenetriamine, cyclic amines such as piperazines, piperidines, pyrrolidines, polyamines such as xylylenediamine and amino acids such as methylaminocarboxylic acid, and the like, and these can be used singly or in combination of two or more.

The absorption liquid L is used as an aqueous solution containing 10 to 70% by weight of the amine compound. In addition, the absorption liquid L includes a reaction accelerator, a nitrogen-containing compound that improves the absorption performance of acidic gases such as carbon dioxide, an anticorrosive agent for preventing corrosion of plant equipment, an antifoaming agent for preventing foaming, and , an antioxidant for preventing deterioration of the absorbing liquid, a pH adjuster, and other compounds may be appropriately contained in an arbitrary ratio within a range that does not impair the effect of the absorbing liquid L.

The exhaust gas G0 is an exhaust gas containing carbon dioxide, and is, for example, combustion exhaust gas discharged from a boiler, gas turbine, etc. of a thermal power plant, process exhaust gas generated in a steelworks, or the like. The exhaust gas G0 is, for example, pressurized by a blower or the like, cooled by a cooler, and then introduced from the lower part of the absorber 1 through the flue.

More specifically, the absorber 1 includes an absorption section 2 that brings the exhaust gas G0 and the absorption liquid L into gas-liquid contact and causes the absorption liquid L to absorb carbon dioxide, and a gas cleaning section 3 that is arranged above the absorption section 2. , have

The absorber 1 is configured as, for example, a packed countercurrent type gas-liquid contact device, and the absorption part 2 is formed of a packing material to improve the gas-liquid contact efficiency. The exhaust gas G0 flows into the absorbing section 2 from below and comes into countercurrent contact with the absorbent L flowing into the absorbing section 2 from above.

When the flue gas G0 and the absorbing liquid L are in countercurrent contact, the flue gas G0 and the absorbing liquid L react to form, for example, a thermally decomposable salt and a thermally stable amine salt, and the carbon dioxide in the flue gas G0 becomes the absorbing liquid L. absorbed by The rich absorbent L(R) that has absorbed carbon dioxide falls downward from the absorbing part 2 and accumulates in the lower part of the absorber 1 . At this time, the rich absorption liquid L(R) contains, for example, the above-described thermally decomposable salt and thermally stable amine salt. In addition, oxygen contained in the exhaust gas G0 can also be absorbed by the rich absorbent L(R).

On the other hand, the exhaust gas G0 that has flowed into the absorption section 2 from below as described above flows out upward from the absorption section 2 as the carbon dioxide-removed gas Gm, and flows into the gas cleaning section 3 . When the carbon dioxide-removed gas Gm flows into the gas cleaning unit 3, the gas cleaning unit 3 cleans the carbon dioxide-removed gas Gm with the cleaning liquid CL, and recovers the active components of the absorbent (such as amine) accompanying the carbon dioxide-removed gas Gm. do. The gas cleaning unit 3 is arranged above, downstream of the absorbing unit 2, in the direction in which the carbon dioxide-removed gas Gm flows. After the carbon dioxide-removed gas Gm is washed, it becomes an absorber discharge gas G1 from which the effective components of the absorbent have been recovered.

A liquid disperser may be provided above the gas cleaning unit 3 , and in this case, the cleaning liquid CL is dispersed and dropped toward the gas cleaning unit 3 . Moreover, although the gas cleaning unit 3 in the present embodiment is housed inside the absorber 1 , the gas cleaning unit 3 may be provided outside the absorber 1 .

In addition, in the present embodiment, the cleaning liquid CL after the cleaning process flowing downward from the gas cleaning section 3 is stored in a cleaning liquid reservoir (not shown) provided in the lower part of the gas cleaning section 3 and above the absorbent inlet. ). Then, the cleaning liquid CL accumulated in the cleaning liquid reservoir is resupplied to the gas cleaning section 3 from above the gas cleaning section 3 through the cleaning liquid circulation line 12 by driving the circulation pump 21 .

The cleaning liquid CL is repeatedly used through the cleaning liquid circulation line 12, but if the concentration of the active ingredient of the absorbing liquid in the cleaning liquid CL increases, the cleaning performance deteriorates. A part of the cleaning liquid CL may be discharged or mixed with the absorbing liquid L when the cleaning performance of the cleaning liquid CL is lowered. Further, when the cleaning performance of the cleaning liquid CL is lowered, new cleaning liquid CL may be introduced into the cleaning liquid circulation line 12 or the like. The more acidic the cleaning liquid CL, the higher the cleaning efficiency. For example, pure water or sulfuric acid water may be used.

The rich absorbent L(R) accumulated in the lower part of the absorber 1 is discharged from the lower part of the absorber 1 and sent to the regenerator 61 through the rich absorbent supply line 13 . Here, in the present embodiment, an oxygen remover 42 is provided between the absorber 1 and the regenerator 61, and the rich absorbent L(R) discharged from the absorber 1 passes through the oxygen remover 42. It flows into the regenerator 61 .

Specifically, the rich absorbent supply line 13 includes a rich liquid pump 41 , an oxygen remover 42 arranged downstream of the rich liquid pump 41 , and a heat exchanger 51 arranged downstream of the oxygen remover 42 . and a pressure regulator 52 arranged downstream of the heat exchanger 51 .

The rich absorbent L(R) discharged from the absorber 1 is introduced into the oxygen remover 42 by driving the rich liquid pump 41 . In the present embodiment, the rich absorbent L(R) is pressurized by the rich liquid pump 41 and introduced into the oxygen remover 42, but the pressurization is not necessarily required. The oxygen remover 42 removes oxygen from the rich absorbent L(R), more precisely removes oxygen-containing gas, and then sends the rich absorbent L(R) to the heat exchanger 51 . Details of the oxygen remover 42 will be described later.

The heat exchanger 51 heat-exchanges the rich absorbent L(R) from which oxygen has been removed with the absorbent L which is the lean absorbent regenerated by the regenerator 61 . After that, the rich absorbent L(R) flows into the regenerator 61 via the pressure regulator 52 . The pressure regulating device 52 can adjust the pressure of the rich absorbing liquid L(R) to a predetermined value or less, thereby controlling the pressure to be suitable for the regenerator 61 . Note that the pressure regulator 52 may be, for example, a pressure reducing valve or the like.

When the heat exchanger 51 exchanges heat between the rich absorbent L(R) and the lean absorbent L, the lean absorbent L serves as a heat source, and the rich absorbent L(R) is heated. heated. Conversely, the rich absorbent L(R) serves as a cooling source, and the absorbent L, which is the lean absorbent, is cooled. As the heat exchanger 51, a known heat exchanger such as a plate heat exchanger or a shell and tube heat exchanger can be used.

The rich absorbent L(R) flowing into the regenerator 61 from the pressure regulator 52 is deoxygenated. As described above, the regenerator 61 diffuses carbon dioxide from the rich absorbent L(R), regenerates the rich absorbent L(R) as the absorbent L that is the lean absorbent, The liquid L and the regenerator exhaust gas G2 containing carbon dioxide are discharged.

In the regenerator 61, the rich absorbing liquid L(R) is heated by water vapor (steam) generated by the reboiler 71, thereby dissipating the carbon dioxide contained in the rich absorbing liquid L(R). The rich absorbing liquid L(R) from which carbon dioxide has been diffused becomes the absorbing liquid L as a lean absorbing liquid from which part or all of the carbon dioxide has been removed. When the rich absorbing liquid L(R) is heated by water vapor, the absorbing liquid L generates water vapor, and carbon dioxide remaining in the absorbing liquid L may rise together with the water vapor. Carbon dioxide and water vapor diffused from the rich absorbent L(R) in the regenerator 61 are discharged from the regenerator 61 as regenerator discharge gas G2.

In the present embodiment, the regenerator exhaust gas G2 containing carbon dioxide is discharged from the upper part of the regenerator 61, and then cooled by the cooling water in the cooler 63, so that the condensed water W in which water vapor is condensed and the gas and the regenerator exhaust gas G2 as it is. After that, the regenerator exhaust gas G2 containing condensed water W and carbon dioxide flows into the gas-liquid separator 65 .

Then, the gas-liquid separator 65 discharges the condensed water W from the lower part and supplies it to the upper part of the regenerator 61 . On the other hand, the gas-liquid separator 65 discharges the regenerator exhaust gas G2 from above. The regenerator exhaust gas G2 discharged from the gas-liquid separator 65 is recovered as high-purity carbon dioxide by separating the condensed water. As described above, the acid gas treatment system S recovers carbon dioxide. On the other hand, the absorbent L, which is the lean absorbent discharged from the regenerator 61 , is supplied to the absorber 1 via the heat exchanger 51 and the cooler 81 by driving the lean liquid supply pump 82 .

<Oxygen remover>
The oxygen remover 42 provided in the acid gas treatment system S will be described in detail below with reference to FIGS. 1 and 2. FIG.

The oxygen remover 42 in this embodiment has a housing 42A and a membrane 43 contained within the housing 42A. As shown in FIG. 2, the oxygen remover 42 partitions the interior of the housing 42A into a first space R1 and a second space R2 by a membrane 43, and the rich absorbent L(R) discharged from the absorber 1 is While sending to the regenerator 61 side through the first space R1, the gas containing oxygen in the rich absorbent L(R) is transferred from the rich absorbent L(R) passing through the first space R1 through the membrane 43 to the second Move to space R2.

The housing 42A in the present embodiment includes a cylindrical housing body 421 that accommodates the membrane 43 and is open at both ends, an introduction portion 422 provided to cover the open portion on one end side of the housing body 421, and a housing body 421. and a discharge portion 423 provided to cover the open portion on the other end side. The first space R<b>1 and the second space R<b>2 described above are formed inside the housing body 421 .

The introduction part 422 is hollow, receives the rich absorption liquid L(R) from the liquid inlet 422a, and introduces it into the interior thereof. The discharge part 423 is also hollow, and after receiving the rich absorbing liquid L(R) that has passed through the first space R1, the liquid is supplied from the liquid outlet 423a to the heat exchanger 51 side.

The membrane 43 in this embodiment is a hollow fiber membrane, and strictly speaking, it is a bundle of hollow fiber membranes. The membrane 43 fixes one end of each tubular hollow fiber membrane to the introduction part 422 . One end of each hollow fiber membrane is open to the internal space of the introduction part 422 so that the rich absorbent L(R) can be introduced from the introduction part 422 . The membrane 43 also fixes the other end of each hollow fiber membrane to the discharge section 423 . The other end of each hollow fiber membrane is open to the internal space of the discharge part 423 so that the rich absorption liquid L (R) passing through the inside of each hollow fiber membrane can be supplied to the internal space of the discharge part 423. .

That is, in the present embodiment, the internal space of each hollow fiber membrane constituting the membrane 43 forms the first space R1, and the space outside the membrane 43 in the housing body 421 forms the second space R2. ing.

The oxygen remover 42 as described above introduces the rich absorbing liquid L(R) sent out from the rich liquid pump 41, and the rich absorbing liquid L(R) is introduced into the introduction portion 422 and the inside of the membrane 43 (first space). R1), and the discharge portion 423 in this order, and sent to the heat exchanger 51 side.

Here, when the rich absorbing liquid L(R) passes through the first space R1 inside the membrane 43, which is a hollow fiber membrane, the pressure of the rich absorbing liquid L(R) increases, and the pressure in the first space R1 is relatively larger than the pressure in the second space R2. As a result, oxygen in the rich absorbent L(R) passing through the membrane 43 passes through the membrane 43 toward the second space R2 having a relatively low pressure, and as a result, the oxygen remover 42 can remove oxygen in the rich absorbent L(R).

In the present embodiment, the rich liquid pump 41 pressurizes the rich absorbing liquid L(R) and introduces it into the oxygen remover 42, and the rich liquid pump 41 functions as a pressurizing device for the rich absorbing liquid L(R). do. This promotes the removal of oxygen from the rich absorbent L(R) passing through the first space R1. The pressure in the first space R1 may be made higher than the pressure in the second space R2 by using a decompression device that reduces the pressure in the second space R2. The pressurizing device and the decompressing device may be used together, or only one of them may be used.

Moreover, when oxygen moves from the first space R1 to the second space R2, strictly speaking, components other than oxygen also move to the second space R. Therefore, strictly speaking, "oxygen-containing gas" moves from the first space R1 to the second space R2. This oxygen-containing gas may contain carbon dioxide, but the carbon dioxide in the rich absorbent L(R) basically reacts with the active ingredient of the absorbent and is adsorbed (retained) by the active ingredient of the absorbent. ). Therefore, the movement of carbon dioxide from the first space R1 to the second space R2 is suppressed.

Carbon dioxide in the rich absorbent L(R) is likely to separate from the absorbent component due to temperature rise. Therefore, the movement of carbon dioxide from the first space R1 to the second space R2 can be effectively suppressed.

Although the membrane 43 is a hollow fiber membrane in the present embodiment, the membrane 43 is not limited to a hollow fiber membrane, and may be any material that allows gas to pass through. Also, the material of the film 43 may be organic or inorganic. However, it is desirable to be hydrophobic. Also, the shape of the film 43 may be flat. In this case, in order to ensure a long contact time (residence time) between the membrane 43 and the rich absorbent L(R), the oxygen remover 42 allows the rich absorbent L(R) to flow out to the heat exchanger 51 side. may be provided with a flow control valve or the like for limiting the

The oxygen-containing gas that has moved to the second space R2 as described above is discharged to the outside from the oxygen discharge port 421a provided in the housing body 421, as indicated by the arrow α in FIG. In the present embodiment, the oxygen-containing gas that has moved to the second space R2 is introduced into the gas-liquid separator 44 through the upstream discharge pipe 45 connected to the oxygen discharge port 421a.

The gas-liquid separator 44 separates the oxygen-containing gas into the oxygen gas condensed water Wo and the gaseous oxygen-containing gas, discharges the oxygen gas condensed water Wo from the bottom, and removes the gaseous oxygen. Contained gas is discharged from above through a downstream discharge pipe 46 . The downstream discharge pipe 46 is provided with a carbon dioxide sensor 48 that detects the carbon dioxide concentration of gas containing oxygen.

The carbon dioxide concentration detected by the carbon dioxide sensor 48 is sent to the controller 100 . The control unit 100 in the present embodiment controls the rich liquid pump 41 as a pressurizing device based on the carbon dioxide concentration detected by the carbon dioxide sensor 48, and controls the pressure in the first space R1 and the pressure in the second space R2. Adjust the difference between Note that when a decompression device is used, the control unit 100 may control the pressurization device and/or the decompression device based on the carbon dioxide concentration detected by the carbon dioxide sensor 48 . Note that examples of the control unit 100 are a processor, an electric circuit, a computer, and the like.

If the pressure of the rich absorbent L(R) introduced into the oxygen remover 42 is too high, the oxygen-containing gas that permeates the membrane 43 will be contaminated with a large amount of the absorbent effective component of the rich absorbent L(R) and carbon dioxide. There is a risk of it happening. In this case, the performance of the absorbent may be lowered and the recovery rate of carbon dioxide may be lowered due to the decrease in the active ingredient of the absorbent. On the other hand, in the present embodiment, the rich liquid pump 41 is controlled based on the carbon dioxide concentration detected by the carbon dioxide sensor 48, and the carbon dioxide concentration detected by the carbon dioxide sensor 48 is controlled to a predetermined value or less. The difference between the pressure in the first space R1 and the pressure in the second space R2 is adjusted to be smaller. As a result, it is possible to suppress excessive permeation of the absorbent effective component and carbon dioxide of the rich absorbent L(R) through the membrane 43, thereby suppressing a decrease in the performance of the absorbent and a decrease in the carbon dioxide recovery rate.

Further, when the pressure of the rich absorbent L(R) discharged from the oxygen remover 42 is high, there is a possibility that the processing of the regenerator 61 is affected. In consideration of this, the pressure regulator 52 described above regulates the pressure of the rich absorbing liquid L(R) discharged from the oxygen remover 42 to a predetermined value or less. Specifically, in the present embodiment, detection information from a pressure sensor (not shown) that detects the pressure of the rich absorbing liquid L(R) flowing between the heat exchanger 51 and the pressure regulator 52 is sent to the control unit 100. The control unit 100 controls the pressure regulator 52 . The arrangement position of the pressure regulator 52 is not particularly limited as long as it is between the oxygen remover 42 and the regenerator 61 .

<Action>
Next, the operation of the acid gas treatment system S described above will be described.

The exhaust gas G0 introduced into the acid gas treatment system S first flows into the absorber 1 . The absorber 1 brings the exhaust gas G0 and the absorbing liquid L into contact with each other and causes the absorbing liquid L to absorb carbon dioxide. Then, the absorber 1 discharges the rich absorbent L(R) that has absorbed carbon dioxide from the acid gas-containing gas G0 and the absorber discharge gas G1 from which carbon dioxide has been removed (absorption step). Specifically, the absorber discharge gas G1 is washed by the gas washing unit 3 in the state of the carbon dioxide-removed gas Gm immediately after the carbon dioxide is removed, thereby becoming the absorber discharge gas G1, which is discharged to the outside of the absorber 1. Ejected.

On the other hand, the rich absorbent (R) that has absorbed carbon dioxide flows into the oxygen remover 42 . Here, the oxygen remover 42 sends the rich absorbing liquid L(R) through the first space R1 to the regenerator 61 side, while removing the oxygen-containing gas in the rich absorbing liquid L(R) into the first space R1. The rich absorbent L(R) passing through the space R1 is moved to the second space R2 through the membrane 43 (removal step).

In the present embodiment, when the rich absorbing liquid L(R) passes through the first space R1 inside the membrane 43, which is a hollow fiber membrane, the pressure of the rich absorbing liquid L(R) rises and the first space The pressure in R1 becomes relatively higher than the pressure in the second space R2. As a result, oxygen in the rich absorbing liquid L(R) passing through the inside of the membrane 43 passes through the membrane 43 toward the second space R2 having a relatively low pressure. As a result, the oxygen remover 42 removes oxygen from the rich absorbent L(R).

Next, the rich absorbent L(R) that has flowed out of the oxygen remover 42 is heated in the heat exchanger 51 , and then flows into the regenerator 61 after being pressure-regulated by the pressure regulator 52 as necessary.

The regenerator 61 diffuses carbon dioxide from the received rich absorbent L(R), and discharges the lean absorbent L from which carbon dioxide has been diffused and the regenerator exhaust gas G2 containing carbon dioxide (regeneration process). . The regenerated lean absorbent L is sent to the absorber 1 and reused repeatedly for carbon dioxide separation treatment.

On the other hand, the regenerator exhaust gas G2 is cooled by the cooling water in the cooler 63, so that it is separated into the condensed water W in which water vapor is condensed and the regenerator exhaust gas G2 as gas, followed by gas-liquid separation. It flows into vessel 65 . The gas-liquid separator 65 discharges the condensed water W from the bottom, supplies it to the top of the regenerator 61, and discharges the regenerator exhaust gas G2 from the top. The regenerator exhaust gas G2 discharged from the gas-liquid separator 65 becomes high-purity carbon dioxide by separating the condensed water.

According to the acidic gas treatment system S according to the present embodiment described above, when oxygen is removed from the rich absorbent L(R) that has absorbed carbon dioxide, which is an acidic gas, the rich absorbent L(R) is It is possible to suppress removal of acidic gases other than oxygen such as active ingredients and carbon dioxide from the rich absorbent L(R).

Specifically, in the present embodiment, when the rich absorbing liquid L(R) passes through the first space R1 inside the membrane 43, which is a hollow fiber membrane, the pressure of the rich absorbing liquid L(R) naturally rises. However, the pressure in the first space R1 is relatively higher than the pressure in the second space R2. As a result, oxygen in the rich absorbing liquid L(R) passing through the inside of the membrane 43 passes through the membrane 43 toward the second space R2 having a relatively low pressure. As a result, the oxygen remover 42 can remove oxygen from the rich absorbent L(R). At this time, since the rich absorbing liquid L(R) has not yet been heated, the carbon dioxide in the rich absorbing liquid L(R) is adsorbed (held) by the effective component of the absorbing liquid. Therefore, the movement of carbon dioxide from the first space R1 to the second space R2 is suppressed. Therefore, in the oxygen remover 42, it is possible to suppress the removal of the active ingredients of the rich absorbent L(R) and acidic gases other than oxygen such as carbon dioxide from the rich absorbent L(R).

In particular, since the oxygen remover 42 is provided between the absorber 1 and the heat exchanger 51, the movement of carbon dioxide from the first space R1 to the second space R2 is effectively suppressed.

In addition, the oxygen remover 42 can remove oxygen while suppressing the desorption of the active ingredient and carbon dioxide from the rich absorption liquid L(R) with a simple configuration using the membrane 43. It is advantageous in terms of manufacturing cost and manufacturing efficiency in any case when introducing it into the equipment of.

Although the embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

S... Acidic gas treatment system 1... Absorber 2... Absorber 3... Gas cleaning part 11... Exhaust gas line 12... Washing liquid circulation line 13... Rich absorbent supply line 21... Circulating pump 41... Rich Liquid pump 42 Oxygen remover 42A Housing 421 Housing body 422 Introduction part 422a Liquid inlet 423 Discharge part 423a Liquid outlet 43 Membrane 44 Gas-liquid separator 45 ... upstream discharge pipe, 46 ... downstream discharge pipe, 48 ... carbon dioxide sensor, 51 ... heat exchanger, 52 ... pressure regulator, 61 ... regenerator, 63 ... cooler, 65 ... gas-liquid separator, 71 ... reboiler, 81...cooler, R1...first space, R2...second space, L...acid gas absorbent (lean absorbent), L(R)...acid gas absorbent that has absorbed carbon dioxide (rich absorbent), CL ... Cleaning liquid, G0 ... Exhaust gas, Gm ... Carbon dioxide removal gas, G1 ... Absorber exhaust gas, G2 ... Regenerator exhaust gas

Claims (12)

Absorption in which the acid-gas-containing gas and the acid-gas-absorbing liquid are brought into contact with each other, and the acid-gas-containing liquid that has absorbed the acid gas from the acid-gas-containing gas and the acid-gas-containing gas from which the acid gas has been removed are discharged. vessel and
a regenerator that diffuses the acidic gas from the acidic gas-absorbing liquid discharged from the absorber and discharges the acidic gas-absorbing liquid that has diffused the acidic gas and the gas containing the diffused acidic gas; ,
an oxygen remover provided between the absorber and the regenerator;
The oxygen remover has a first space and a second space partitioned by a membrane, and sends the acidic gas-absorbing liquid discharged from the absorber through the first space to the regenerator side. and an acidic gas treatment system, wherein gas containing oxygen in said acidic gas absorbing liquid is moved from said acidic gas absorbing liquid passing through said first space through said membrane to said second space. The oxygen remover makes the pressure in the first space higher than the pressure in the second space, thereby moving the oxygen-containing gas in the acidic gas absorbing liquid to the second space through the membrane. Item 1. The acid gas treatment system according to item 1. 3. The acid gas treatment system of claim 2, wherein said oxygen remover comprises a pressurization device and/or a pressure reduction device for increasing the pressure in said first space above the pressure in said second space. further comprising a carbon dioxide sensor that detects the carbon dioxide concentration of the oxygen-containing gas that has moved to the second space,
The acid gas treatment system according to claim 2 or 3, wherein the difference between the pressure in said first space and the pressure in said second space is adjusted based on the carbon dioxide concentration detected by said carbon dioxide sensor. 2. A pressure regulating device provided between said oxygen remover and said regenerator for adjusting the pressure of said acidic gas-absorbing liquid discharged from said oxygen remover to a predetermined value or less. 5. The acid gas treatment system according to any one of 1 to 4. further comprising a heat exchanger for exchanging heat between the acidic-gas-absorbing liquid that has absorbed the acidic gas discharged from the absorber and the acidic-gas-absorbing liquid that has dissipated the acidic gas discharged from the regenerator;
6. The acid gas treatment system of any of claims 1-5, wherein the oxygen remover is provided between the absorber and the heat exchanger. Absorption in which the acid-gas-containing gas and the acid-gas-absorbing liquid are brought into contact with each other, and the acid-gas-containing liquid that has absorbed the acid gas from the acid-gas-containing gas and the acid-gas-containing gas from which the acid gas has been removed are discharged. process and
a removal step of removing oxygen-containing gas from the acidic gas absorbing liquid discharged in the absorption step;
a regeneration step of diffusing the acidic gas from the acidic gas-absorbing liquid after the removing step, and discharging the acidic gas-absorbing liquid from which the acidic gas has been diffused and the gas containing the diffused acidic gas; prepared,
In the removing step, the oxygen-containing gas contained in the acidic gas absorbing liquid is passed through the first space of the first space and the second space partitioned by a membrane while the acidic gas absorbing liquid discharged in the absorbing step is passed through the first space. from the acidic gas absorbing liquid passing through the first space through the membrane to the second space. 3. In the removing step, the gas containing oxygen in the acidic gas absorbing liquid is moved to the second space through the membrane by making the pressure in the first space higher than the pressure in the second space. 7. The acid gas treatment method according to 7. 9. The acidic gas treatment method according to claim 8, wherein in said removing step, the pressure in said first space is made higher than the pressure in said second space by a pressurizing device and/or a depressurizing device. Detecting the carbon dioxide concentration of the oxygen-containing gas that has moved to the second space, and adjusting the difference between the pressure in the first space and the pressure in the second space based on the detected carbon dioxide concentration. Item 9. The acid gas treatment method according to Item 8 or 9. 11. The acidic gas treatment method according to any one of claims 7 to 10, wherein the pressure of said acidic gas absorbing liquid after said removal step is adjusted to a predetermined value or less, and then said regeneration step is performed. heat exchange between the acid-gas-absorbing liquid after the removing step, which is the acid-gas-absorbing liquid before being treated in the regeneration step, and the acid-gas-absorbing liquid from which the acid gas has been diffused after the regeneration step; The acid gas treatment method according to any one of claims 7 to 11, further comprising the step of causing.

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