KR101190725B1 - Apparatus for separating acid gas from mixed gas - Google Patents

Abstract

The acid gas separation and recovery apparatus of the present invention includes a first absorption tower for producing a saturated first absorbent by reacting an acid gas contained in a first absorbent and combustion exhaust gas; A second absorption tower reacting with a second absorbent and an acid gas included in combustion exhaust gas discharged from the first absorption tower to generate a saturated second absorbent; And a stripping tower upper portion for regenerating the saturated first absorbent with a regenerating first absorbent and supplying the saturated absorbent to the first absorption tower, and a lower stripping tower for regenerating the saturated second absorbent with a regenerating second absorbent and supplying the second absorbing tower to the second absorbing tower. An acid gas separation and recovery apparatus comprising: a first absorbent is an absorbent that requires less renewable energy than the second absorbent, and the second absorbent reacts with the acid gas more rapidly than the first absorbent. Is a fast absorbent.
According to the present invention, since the amine or amino acid salt-based compound reacting at a low temperature in both the first absorption tower and the second absorption tower as an absorbent does not require a separate cooler unlike the prior art.

Description

Acid gas separation and recovery unit {APPARATUS FOR SEPARATING ACID GAS FROM MIXED GAS}

The present invention relates to an acid gas separation recovery apparatus, and more particularly, to an acid gas separation recovery apparatus for circulating two or more absorbents independently to reduce acid gas separation recovery energy.

As the industry develops, the concentration of acidic gases such as carbon dioxide (CO ₂ ), methane (CH ₄ ), hydrogen sulfide (H ₂ S), carbonyl sulfide (COS), etc. increases in the atmosphere. Internationally, efforts are being made to prevent global warming by tightening regulations on the emission and disposal of acid gases.

Among the acid gases that cause global warming, carbon dioxide accounts for more than 50% of the emitted acid gas, and much research is being conducted on technologies for suppressing the emission of carbon dioxide.

Techniques for suppressing carbon dioxide emission include energy saving technology for reducing carbon dioxide emission, technology for separating and recovering carbon dioxide, technology for using or immobilizing carbon dioxide, and renewable energy technology that does not emit carbon dioxide.

As a technique for separating and recovering carbon dioxide, absorption, adsorption, membrane separation, deep cooling, and the like have been proposed. Absorption is a method of separating and recovering carbon dioxide by using an absorbent. The absorption method has high efficiency and stability, is easy to process a large volume of gas, and is suitable for low concentration gas separation, which can be easily applied to most industrial and power plants.

1 is a view illustrating a general acid gas separation recovery process.

Referring to FIG. 1, a general acid gas separation and recovery process contacts combustion exhaust gas with an absorbent in an absorption tower so that the acid gas is absorbed into the absorbent. The absorbent absorbing acid gas from the absorption tower is injected into the upper part of the stripping column via a heat exchanger. The stripping column regenerates the absorbent by removing the acid gas chemically bound to the absorbent using thermal energy of steam supplied through the reboiler. The stripped acid gas and water vapor are phase separated in the reflex drum. The separated steam is recovered as condensate (H ₂ O) and fed back to the stripping column, where the acid gas is converted to storage or other useful high value chemicals through acid gas recovery and treatment. The absorbent regenerated in the stripping tower is transferred to the absorption tower after the temperature is lowered through the heat exchanger.

However, in the general acid gas separation and recovery process, the absorption tower and the stripping column are configured in one stage, respectively, and when two or more types of absorbents are mixed and used, there is a problem in that the advantages of mixing the absorbents are reduced. In addition, there is a problem in that energy efficiency is lowered due to the lack of mutual heat exchange of the absorbent circulation path and the unrecovered heat of the acid gas discharged to the top of the stripping column.

Recently, in order to reduce energy required for the recovery and recovery of acidic gas, a technology for separating and recovering acidic gas by mixing various amine compounds has been developed. 2 is a view illustrating such a conventional acid gas separation recovery process.

Referring to FIG. 2, in the conventional acid gas separation and recovery process, the alkanolamine absorbent combined with the acid gas of the combustion flue gas in the upper absorption tower 28 is injected into the stripping column bottom 30 to heat supplied from an external heating source. And the alkali metal carbonate combined with the acid gas of the combustion flue gas in the lower absorption tower 25 is injected into the upper part of the stripping column 35 through indirect heat exchange with the fluid condensed on the upper part of the stripping column 30. Is played.

According to the conventional acid gas separation recovery process using two kinds of absorbents, the cost of absorbent regeneration can be reduced by using different properties of the two absorbents. However, the conventional acid gas separation and recovery process using two kinds of absorbents uses an alkali metal oxide reacting at a high temperature and an alkynolamine reacting at a low temperature as an absorbent, so that combustion exhaust gas passing through the lower absorption tower 25 is used as an upper absorption tower. A separate chiller 26 is needed to feed 28. In addition, heat recovery for the steam and acid gas mixed gas discharged to the upper part of the stripping column 35 is not achieved, and heat exchange between circulating absorbents is not performed, thereby reducing energy efficiency.

The present invention has been made to solve the above-mentioned problems, heat exchange the cooled exhaust gas supplied to the lower absorption tower and the gas discharged after the reaction in the lower absorption tower, recover the heat of the acid gas discharged from the stripping tower The purpose is to provide an acid gas separation and recovery apparatus for preheating the saturated absorbent supplied to the stripping column.

Another object of the present invention is to provide an acid gas separation and recovery device for reacting an absorbent which requires less renewable energy and combustion exhaust gas in a lower absorption tower, and reacting an unreacted acid gas in a lower absorption tower in an upper absorption tower. have.

The acid gas separation and recovery apparatus of the present invention for achieving the above object, the first absorption tower and the first absorbent to generate a saturated first absorber by the acid gas contained in the cooled combustion exhaust gas; A second absorption tower reacting with a second absorbent and an acid gas included in the gas discharged from the first absorption tower to generate a saturated second absorbent; And a stripping tower upper portion for regenerating the saturated first absorbent with a regenerating first absorbent and supplying the saturated absorbent to the first absorption tower, and a lower stripping tower for regenerating the saturated second absorbent with a regenerating second absorbent and supplying the second absorbing tower to the second absorbing tower. An acid gas separation and recovery apparatus comprising: a first absorbent is an absorbent that requires less renewable energy than the second absorbent, and the second absorbent reacts with the acid gas more rapidly than the first absorbent. Is a fast absorbent.

The first absorbent may be at least one secondary, tertiary or sterically hindered amine or amino acid salt compound, and the second absorbent may be a primary, secondary amine or amino acid salt compound.

The cooled combustion exhaust gas and the gas discharged from the first absorption tower are preferably heat-exchanged through a heat exchanger.

The saturated first absorbent and the regenerated first absorbent may be heat exchanged through a first heat exchanger, and the saturated second absorbent and the regenerated second absorbent may be heat exchanged through a second heat exchanger.

The acid gas saturated with water vapor discharged to the upper portion of the stripping column may be heat-exchanged through the regenerated first absorbent and the regenerated second absorbent and the heat exchanger, respectively.

The acid gas separation and recovery apparatus of the present invention is a saturation that is supplied to the stripping column by heat exchange between the gas discharged from the lower absorption tower and the cooled combustion exhaust gas supplied to the lower absorption tower, and recovers heat of the acid gas discharged from the stripping tower. Since the absorbent can be preheated, it is possible to efficiently use energy to reduce the operating cost of the acid gas separation and recovery apparatus.

In addition, the present invention reacts the absorbent which requires less renewable energy with the combustion flue gas in the lower absorption tower, and reacts the fast absorbing agent in the upper absorption tower and the unreacted acid gas in the lower absorption tower, thereby absorbing the absorbent in the stripping tower. In addition to reducing the cost of regeneration, there is an effect that can increase the acid gas removal efficiency.

1 is a view showing a general acid gas separation recovery process.
2 is a view showing a conventional acid gas separation recovery process.
3 is a view showing a process of the acid gas separation recovery apparatus according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

Figure 3 is a view showing a process of the acid gas separation recovery apparatus according to an embodiment of the present invention.

Referring to Figure 3, the acid gas separation recovery apparatus according to an embodiment of the present invention, the first absorption tower 110, the second absorption tower 120 and the stripping tower 200.

The first absorbent 110 is supplied with a first absorbent and the combustion exhaust gas 10. The first absorbent is an absorbent that requires less renewable energy than the second absorbent, for example one or more secondary, tertiary or sterically hindered amine or amino acid salt based compounds. The combustion flue gas 10 includes at least one acidic gas of carbon dioxide (CO ₂ ), hydrogen sulfide (H ₂ S), sulfur dioxide (SO ₂ ), nitrogen dioxide (NO ₂ ), and carbonyl sulfide (COS).

The combustion exhaust gas 10 may be supplied to the lower end of the first absorption tower 110 through the combustion gas supply line while being cooled by a cooling device (not shown) in order to overcome the pressure drop generated in the absorption tower. The upper end of the first absorption tower 110 and the lower end of the second absorption tower 120 are connected by a connection line in which the first heat exchanger 130 is installed. The cooling path 192 and the connection line branched from the combustion gas supply line cross each other through the first heat exchanger 130 to exchange heat with each other.

The second absorption tower 120 is supplied with the second absorbent and the unreacted gas 11 from the first absorption tower 110. The second absorbent is an absorbent having a faster reaction rate with an acidic gas than the first absorbent, for example, a primary, secondary amine or amino acid salt compound.

The stripping tower 200 includes a stripping tower top 210 and a stripping tower bottom 220.

The stripping tower upper portion 210 and the first absorption tower 110 are connected to the first net environment path 170 through which the first absorbent circulates. The first pure environmental path 170 is a lower end of the first supply line 172 and the upper part of the stripping tower 210 to which the saturated first absorbent is supplied from the lower end of the first absorption tower 110 to the upper part of the upper stripping tower 210. And a second supply line 174 through which the regenerated first absorbent is supplied to the top of the first absorption tower 110. The first supply line 172 and the second supply line 174 cross each other through the second heat exchanger 150 so that the saturated first absorbent and the regenerated first absorbent may exchange heat.

 The stripping tower lower portion 220 and the second absorption tower 120 are connected to the second net environment path 180 through which the second absorbent is circulated. The second pure environment path 180 is a lower end of the third supply line 182 and the lower stripping column 220 to which the saturated second absorbent is supplied from the lower end of the second absorption tower 120 to the upper end of the stripping tower 220. And a fourth supply line 184 through which the regenerated second absorbent is supplied to the upper end of the second absorption tower 120. The third supply line 182 and the fourth supply line 184 cross each other through the third heat exchanger 152 so that the saturated second absorbent and the regenerated second absorbent may exchange heat.

The upper end of the stripping tower 210 is connected to the energy recovery path 190. The energy recovery path 190 and the first supply line 172 cross each other through the fourth heat exchanger 140 to recover the heat of the high temperature carbon dioxide and preheat the saturated first absorbent. The energy recovery path 190 and the third supply line 182 cross each other through the fifth heat exchanger 142 to recover the heat of the high temperature carbon dioxide and preheat the saturated second absorbent. Unexplained 230 is a valve, 232 is a pump, 234 is a reflux drum, and 236 is a heat exchanger.

Hereinafter will be described the operation of the acid gas separation recovery apparatus according to an embodiment of the present invention.

First, the operation of the first absorption tower 110 and the second absorption tower 120 will be described. In the first absorption tower 110, while the first absorbent and the combustion exhaust gas 10 are in countercurrent contact, the first absorbent absorbs the acid gas included in the combustion exhaust gas 10 to generate a saturated first absorbent. .

In the first absorption tower 110, the gas 11 whose temperature rises due to the exothermic reaction between the first absorbent and the acid gas is supplied to the lower portion of the second absorption tower 120 through a connection line. In this case, the gas 11 discharged from the upper end of the first absorption tower 110 may be cooled by heat exchange with the combustion exhaust gas 10 through the first heat exchanger 130, and then supplied to the second absorption tower 120.

Since both the first absorption tower 110 and the second absorption tower 120 of the present embodiment use an amine or an amino acid salt compound reacting at a low temperature as an absorbent, the first absorption tower 110 and the second absorption tower 120 The small temperature difference eliminates the need for a separate cooler. In addition, by cooling the reaction heat generated in the first absorption tower 110 through the first heat exchanger 130, it is possible to properly maintain the temperature of the combustion exhaust gas 11 supplied to the second absorption tower 120.

In addition, by absorbing most of the acidic gas in the combustion flue gas (10) as a first absorbent that requires less renewable energy, and absorbing some remaining acidic gas as a second absorbent having a fast reaction rate, the absorbent is recovered in the stripping column (200). The acid gas can be efficiently separated from the combustion exhaust gas 10 while minimizing thermal energy.

Next, heat exchange between the saturated first absorbent and the regenerated first absorbent in the first pure environment furnace 170 will be described. Since the stripping tower 200 requires a higher reaction temperature than the first absorption tower 110, the regeneration first absorbent discharged from the stripping tower 210 may include a saturated first discharged from the bottom of the first absorption tower 110. The temperature is higher than the absorbent.

The saturated first absorbent of the first supply line 172 may be supplied to the upper part of the stripping tower 210 in a preheated state by recovering heat of the regenerated first absorbent through the second heat exchanger 150. On the other hand, the regenerated first absorbent of the second supply line 174 may be supplied to the top of the first absorption tower 110 in a cooled state by dissipating heat to the saturated first absorbent through the second heat exchanger 150. . The heat exchange of the saturated first absorbent and the regenerated first absorbent in the first pure environment path 170 may improve the energy efficiency of the acidic gas separation and recovery apparatus according to the present embodiment.

Since the heat exchange between the saturated second absorbent and the regenerated second absorbent in the second pure environment furnace 180 is easily understood by those skilled in the art from the description of the heat exchange between the saturated first absorbent and the regenerated first absorbent in the first pure environment furnace 170. Detailed description will be omitted.

Next, the energy recovery using the acid gas discharged from the stripping column 200 will be described. The stripping tower 200 needs high heat energy to separate the acid gas from the saturated absorbent and regenerate the absorbent, so that the acid gas discharged to the top of the stripping column 200 has high heat energy.

The acid gas of the energy recovery path 190 is saturated in the first supply line 172 through the fourth heat exchanger 140 and in the third supply line 182 through the fifth heat exchanger 142. It releases heat to the second absorbent. Therefore, the saturated first absorbent of the first supply line 172 and the saturated second absorbent of the third supply line 182 may be preheated with heat recovered from the mixed gas and supplied to the stripping tower 200, respectively.

The valve 230 selectively regulates the fluid flowing in the line where the valve 230 is installed, and the pump 234 provides flow force to the fluid flowing in the line where the pump 234 is installed. Since the heat exchanger 236 and the reflux drum 234 separating the condensed water and the acid gas from the mixed gas discharged to the other stripping tower 200 are easily understood by those skilled in the art, detailed descriptions thereof will be omitted.

Although the detailed description of the present invention described above has been described with reference to a preferred embodiment of the present invention, a person skilled in the art without departing from the spirit and scope of the present invention described in the claims to be described later It will be understood that various modifications and variations can be made in the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

110: first absorption tower 120: second absorption tower
130,140,142,150,152: heat exchanger
160: reboiler 170: the first net environment
180: second net environment path 190: energy recovery path
192: cooling path 200: stripping tower
210: upper stripping tower 220: lower stripping tower

Claims (5)

A first absorption tower reacting with the first absorbent and the acid gas included in the cooled combustion exhaust gas to generate a saturated first absorbent; A second absorption tower for producing a saturated second absorbent by reacting a second absorbent with an unreacted acid gas in the first absorption tower; A stripping tower top for regenerating the saturated first absorbent with a regenerating first absorbent and supplying it to the first absorbing tower, and a stripping tower bottom for regenerating the saturated second absorbent with a regenerating second absorbent and supplying it to the second absorption tower. Stripping tower consisting of; A first supply line receiving the saturated first absorbent from the lower end of the first absorption tower to the upper end of the stripping tower, and receiving the regenerated first absorbent from the lower end of the upper part of the stripping tower to the top of the first absorption tower; A first circulation path composed of a second supply line; And
A third supply line receiving the saturated second absorbent from the lower end of the second absorption tower to the upper end of the stripping tower, and a fourth receiving the regeneration second absorbent from the lower end of the lower absorption tower to the top of the second absorption tower. A second circulation path composed of a supply line,
The first absorbent is an absorbent which requires less renewable energy than the second absorbent, and the second absorbent is an absorbent having a faster reaction rate with the acid gas than the first absorbent.
The cooled combustion exhaust gas and the combustion gas discharged from the first absorption tower exchange heat through the first heat exchanger 130,
The saturated first absorbent and the regenerated first absorbent are heat exchanged through a second heat exchanger 150 disposed on the first circulation path, and the saturated second absorbent and the regenerated second absorbent are disposed on the second circulation path. Heat exchange through the arranged third heat exchanger (152),
The acid gas discharged to the upper portion of the stripping column is heat-exchanged through the saturated first absorbent and the fourth heat exchanger 140, and heat-exchanged with the saturated second absorbent through the fifth heat exchanger 142. Acid gas separation and recovery unit.
The method of claim 1,
The first absorbent is at least one secondary, tertiary or sterically hindered amine or amino acid salt compound, the second absorbent is primary, secondary amine or amino acid salt compound, and the combustion flue gas is carbon dioxide (CO ₂ ), hydrogen sulfide (H ₂ S), sulfur dioxide (SO ₂ ), nitrogen dioxide (NO ₂ ) and carbonic acid sulfide (COS) at least one acidic gas separation and recovery device characterized in that it comprises an acid gas.
delete delete delete

Images