JPH09155141A - Absorption device of carbon dioxide gas in exhaust gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the structure of a regeneration tower in an absorption tower of carbon dioxide gas from becoming complicated and to reduce heat consumption of the regeneration tower. SOLUTION: The packed bed of a regeneration part in a regeneration tower is divided into at least two steps of the upper step 42 of the regeneration part and the lower step 43 of the regeneration part in the direction of height. A carbon dioxide gas-rich absorption liquid line 4 is branched into the upper step carbon dioxide gas-rich absorption liquid line 40 and the lower step carbon dioxide gas-rich absorption liquid line 41. Means are provided by which carbon dioxide gas-rich absorption liquid is supplied from the line 40 to the upper step 42 and supplied from the line 41 to the lower step 43. Further, means are provided by which absorption liquid is drawn out from the lower part of the upper step 42 and steam is directly introduced into the lower part of the upper step 42 from a reboiler 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for absorbing carbon dioxide gas in exhaust gas suitable for reducing heat input to a regenerator reboiler for regenerating an absorbent.

[0002]

2. Description of the Related Art In recent years, carbon dioxide concentration in the atmosphere has increased due to an increase in consumption of fossil fuels, and there is a concern about global warming. It is listed as a global goal to reduce carbon dioxide emissions to the level of 1990 in the year 2000. However, it cannot be denied that the rise in carbon dioxide concentration in the atmosphere will not stop and global warming will become serious. Therefore, considering the future increase in energy demand accompanying the economic growth of each country,
It must be called an urgent task to develop new technologies for recovery. An amine absorption method using an alkanolamine as an absorbent is known for removing and recovering carbon dioxide. A typical carbon dioxide gas absorption device by this amine absorption method will be described. FIG. 3 is a flow chart showing the configuration of a conventional carbon dioxide gas absorption device for exhaust gas. As shown in this figure, the exhaust gas 11 containing carbon dioxide gas generated from a combustion device (not shown) is pressurized by a fan (not shown) and introduced into the bottom of the absorption tower 1. The exhaust gas 11 comes into countercurrent contact with an absorption liquid which is an aqueous solution of monoethanolamine (hereinafter referred to as MEA) flowing down from the upper part of the absorption tower absorption part 12 while rising in the absorption tower absorption part 12 of the absorption tower 1, Carbon dioxide is absorbed. The exhaust gas 7 from which carbon dioxide has been removed is guided to a chimney (not shown) or the outside of the system. The carbon dioxide rich absorption liquid that has absorbed carbon dioxide is supplied from the bottom of the absorption tower 1 to the regeneration tower 2 in the carbon dioxide rich absorption liquid line 4 via the absorption liquid heat exchanger 8 by a pump. The carbon dioxide rich absorption liquid comes into countercurrent contact with the absorption liquid vapor from the reboiler 3 rising from the lower part of the regeneration tower regeneration part 13 while flowing down the regeneration tower regeneration part 13 of the regeneration tower 2 to release carbon dioxide gas ( Stripped). The vapor from the reboiler 3 serves as a heat source for raising the absorption liquid to a temperature required for desorption of carbon dioxide gas, and also serves as a carrier gas for stripping the carbon dioxide gas in the absorption liquid.

Here, the structure around the reboiler 3 for generating the vapor of the absorbing liquid will be described. The absorbing liquid that has flowed down the regeneration tower regeneration unit 13 is once stored in the chimney 30 below the regeneration tower regeneration unit 13.
Stored in the regenerator 3 through the chimney liquid withdrawing line 31. In the reboiler 3, the absorption liquid is evaporated by the steam supplied from the outside to become vapor, and the reboiler vapor line 32 is guided to the lower portion of the chimney 30. MEA by evaporation of steam
The reboiler liquid withdrawing line 33 guides the absorption liquid having a predetermined concentration to the bottom of the regeneration tower 2. By arranging the level of each device in the order of the chimney 30, the reboiler 3, and the bottom of the regeneration tower 2, the absorbing liquid flows down naturally. The carbon dioxide lean absorption liquid regenerated in the regeneration tower 2 is supplied from the bottom of the regeneration tower 2 to the absorption tower 1 in the carbon dioxide lean absorption liquid line 5 by the pump through the absorption liquid heat exchanger 8 and the inside of the carbon dioxide absorption device. Circulate. An absorption tower water washing section 6 is provided at the top of the absorption tower 1, and the mist of the absorption liquid entrained in the exhaust gas rising from the absorption tower absorption section 12 is washed and removed with circulating water at 30 to 50 ° C. ing. Similarly, a regeneration tower washing section 21 is provided at the top of the regeneration tower 2 so that the carbon dioxide gas rising from the regeneration tower regeneration section 13 is cooled by the overhead condenser 9 and at the same time saturated water vapor is condensed into the carbon dioxide gas. The gas is separated into gas and liquid by the reflux drum 10 and is returned to the regeneration tower water washing section 21 as the reflux 20 at 30 to 50 ° C. to wash and remove the mist of the absorbing liquid accompanying the carbon dioxide gas.

[0004]

In the conventional regeneration tower, the carbon dioxide rich absorbent introduced into the regeneration tower 13 reaches the boiling point immediately after it begins to flow down in the regeneration tower regeneration section 13, and the carbon dioxide gas is locally desorbed to regenerate it. In the case of the packed tower type regeneration tower 2, the flow velocity of the gas in the tower 2 is increased, and the flowing down of the absorbing liquid is obstructed by the flooding phenomenon, and the regeneration tower 2 cannot be operated. Therefore, in order to suppress such a phenomenon, the operating pressure of the regeneration tower 2 is increased to 0.3 to 0.6 kgf / cm ² to raise the boiling point of the absorbing liquid to slow the desorption of carbon dioxide gas. By increasing the operating pressure of the regeneration tower 2, it is necessary to increase the strength of the regeneration tower 2 as a pressure vessel, and it is also obligatory to install a safety valve.

FIG. 4 is a flow chart of a regeneration tower of a conventional carbon dioxide gas absorption device. This figure shows the exhaust gas treatment amount of 1,000
The structure of the regeneration tower of the Nm ³ / h pilot plant is shown. FIG. 5 is a chart showing the relationship between the carbon dioxide rich absorbent introduction temperature and the temperature distribution in the tower in the regeneration tower of FIG. FIG.
Pressure regeneration tower 2 shown in 0.6kgf / cm ^2, the regenerator 2
The temperature of the carbon dioxide rich absorbent supplied to the reactor was started at 100 ° C., and the intermediate temperature of the regeneration tower regeneration section 13 was 98 ° C. as indicated by the triangle marks in FIG. Next, when the temperature of the carbon dioxide rich absorbent supplied to the regeneration tower 2 was raised from 100 ° C. to 102 ° C., the intermediate temperature of the regeneration tower regeneration section 13 was as shown in FIG.
As indicated by the circle, the temperature reached 91 ° C. and the absorbing liquid stopped flowing down. This phenomenon occurs because the carbon dioxide gas is rapidly desorbed at the upper part of the regeneration tower regenerator 13 and the heat of the desorption reaction is removed from the absorbent, so that the temperature of the absorbent decreases and reaches the middle of the regeneration tower regenerator 13. However, it is considered that the flooding phenomenon occurred due to the increase in the gas flow velocity in the regeneration tower regeneration section 13. In order to prevent such a situation that the regeneration tower 2 becomes inoperable, the operating pressure of the regeneration tower 2 is increased and the temperature of the carbon dioxide rich absorbent supplied to the regeneration tower 2 is set to 10 to 10 from the boiling point.
You have to lower it by 15 degrees. Increasing the operating pressure of the regeneration tower 2 causes problems such as increasing the strength of the regeneration tower 2 and installing a safety valve, and lowering the temperature of the carbon dioxide rich absorbent reduces the heat input to the regeneration tower 2. Therefore, in order to secure the heat necessary for desorption of carbon dioxide, the heat input to the reboiler 3, that is, the supply amount of steam must be increased. An object of the present invention is to prevent the structure of the regeneration tower of the carbon dioxide absorption device from becoming complicated and reduce the heat consumption of the regeneration tower.

[0006]

The above object is to provide an absorption tower for absorbing carbon dioxide gas in exhaust gas by using a circulating absorption liquid,
In a carbon dioxide gas absorption device in exhaust gas having a regeneration tower for regenerating the carbon dioxide rich absorbent from the absorption tower and the vapor from the reboiler at the gas-liquid contact section, the gas-liquid contact section comprises a plurality of and This is achieved by providing means for supplying the carbon dioxide rich absorption liquid, which are arranged in series in the height direction and are provided at the uppermost part of each of the gas-liquid contact portions.
The above-mentioned purpose is a regeneration in which a carbon dioxide rich absorption liquid from the absorption tower and the vapor from the reboiler are brought into contact with each other at a gas-liquid contact part to regenerate the absorption tower that absorbs carbon dioxide gas in the exhaust gas by using the circulating absorption liquid. In a device for absorbing carbon dioxide gas in exhaust gas having a tower, the gas-liquid contact portions are composed of a plurality and are arranged in series in the height direction, and the carbon dioxide-rich absorption liquid is supplied to the uppermost part of each of the gas-liquid contact portions. Means, a liquid reservoir arranged at the bottom of each gas-liquid contact portion, and a liquid pipe communicating from the respective liquid reservoir to the reboiler,
This is achieved by providing a steam pipe that communicates from the reboiler to the bottom of each of the gas-liquid contact portions.

The gas-liquid contact portion of the regeneration tower is divided into a plurality of parts,
With the configuration that the carbon dioxide rich absorbent is dispersed and supplied to each gas-liquid contact part, the desorption of carbon dioxide is dispersed without concentration, and the operation pressure is raised to slow the desorption of carbon dioxide. Since it is not necessary to lower the supply temperature of the carbon dioxide rich absorbent, it is possible to prevent the structure of the regeneration tower from becoming complicated, and to prevent an increase in heat input to the reboiler of the regeneration tower.
Since the steam from the reboiler is directly introduced into the upper gas-liquid contact section of the regeneration tower, the carbon dioxide rich absorbent and vapor from the reboiler are evenly contacted at each gas-liquid contact section, improving the thermal efficiency of the entire regeneration tower. To do.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flow chart showing the configuration of a carbon dioxide gas absorption device in exhaust gas according to an embodiment of the present invention.
The basic configuration of the present carbon dioxide absorption device is as shown in FIG. 2, and the feature of the present invention is that the packed bed filled with Raschig rings and the like of the regeneration tower regeneration section is regenerated at least in the height direction with the upper section 42 of the regeneration tower regeneration section. The tower regeneration section is divided into two lower stages 43, and the carbon dioxide rich absorption liquid line 4 is branched into an upper carbon dioxide rich absorption liquid line 40 and a lower carbon dioxide rich absorption liquid line 41, and the carbon dioxide rich absorption liquid 40 is divided into upper carbon dioxide rich absorption liquid line 40. From the lower carbon dioxide rich absorbent line 41 to the lower part 4 of the regeneration tower regeneration part.
3 to supply. By dividing the carbon dioxide-rich absorption liquid and supplying it to the regeneration tower regeneration section in this way, the desorption of carbon dioxide gas in the vicinity of each carbon dioxide-rich absorption liquid supply nozzle becomes slow, and the flooding phenomenon as in the past does not occur. Therefore, the operation of raising the operating pressure of the regeneration tower 2 and the operation of lowering the temperature of the carbon dioxide rich absorbent are not required, so that the structure of the regeneration tower 2 becomes simple and the steam consumption supplied to the reboiler 3 can be reduced.

Next, another embodiment of the present invention will be described.
FIG. 2 is a flowchart showing the configuration of a carbon dioxide gas absorption device for exhaust gas according to another embodiment of the present invention. As shown in this figure, the chimney 34 is provided at the lower part of the upper part 42 of the regeneration section of the regeneration tower, and the chimney liquid extraction line 3 for extracting the absorbing liquid from the chimney 34.
5 and a reboiler steam line 36 for introducing steam from the reboiler 3 to the lower part of the upper stage 42 of the regeneration tower regeneration section are newly provided. The structure shown in this figure is provided with a means for extracting the absorption liquid from the lower part of the upper part 42 of the regeneration tower regeneration part shown in FIG. 1 and directly introducing the vapor from the reboiler 3 to the lower part of the upper part 42 of the regeneration tower regeneration part. With such a configuration, the carbon dioxide rich absorbent in each regeneration tower regeneration section, that is, the regeneration tower regeneration section upper stage 42 and the regeneration tower regeneration section lower stage 43, is uniformly contacted with the vapor from the reboiler 3, and regeneration is performed. The thermal efficiency of the entire tower is improved.

[0010]

According to the present invention, the gas-liquid contact portion of the regeneration tower is divided into a plurality of parts, and the carbon dioxide rich absorption liquid is dispersed and supplied to each gas-liquid contact portion, whereby desorption of carbon dioxide gas is dispersed. Therefore, it is not necessary to increase the operating pressure of the regeneration tower and to lower the supply temperature of the carbon dioxide rich absorbent, so that the structure of the regeneration tower is not complicated and an increase in heat input to the reboiler can be prevented. Since the steam from the reboiler is directly introduced into the upper gas-liquid contact section of the regeneration tower, the carbon dioxide rich absorbent and vapor from the reboiler are evenly contacted at each gas-liquid contact section, improving the thermal efficiency of the entire regeneration tower. To do.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a configuration of a carbon dioxide gas absorption device in exhaust gas according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a configuration of a carbon dioxide gas absorption device for exhaust gas according to another embodiment of the present invention.

FIG. 3 is a flowchart showing a configuration of a conventional carbon dioxide gas absorption device in exhaust gas.

FIG. 4 is a flowchart of a regeneration tower of a conventional carbon dioxide gas absorption device.

5 is a chart showing a relationship between a carbon dioxide-rich absorption liquid introduction temperature and a temperature distribution in the tower in the regeneration tower of FIG.

[Explanation of symbols]

 1 Absorption Tower 2 Regeneration Tower 3 Reboiler 4 Carbon Dioxide Rich Absorption Liquid Line 5 Carbon Dioxide Lean Absorption Liquid Line 6 Absorption Tower Rinsing Part 7 Carbon Dioxide Removed Exhaust Gas 8 Absorption Liquid Heat Exchanger 9 Overhead Condenser 10 Reflux Drum 11 Exhaust Gas 12 Absorption Tower absorption section 13 Regeneration tower regeneration section 14 Circulating water line 20 Reflux 21 Regeneration tower water washing section 30 Chimney 31 Chimney liquid withdrawal line 32 Reboiler steam line 33 Reboiler liquid withdrawal line 34 Chimney 35 Chimni liquid withdrawal line 36 Reboiler steam line 40 Upper carbon dioxide Gas-rich absorption liquid line 41 Lower stage Carbon dioxide-rich absorption liquid line 42 Regeneration tower regeneration section upper stage 43 Regeneration tower regeneration section lower stage

Claims (2)

[Claims] 1. An absorption tower that absorbs carbon dioxide gas in exhaust gas using a circulating absorption liquid, and a carbon dioxide-rich absorption liquid from the absorption tower and steam from a reboiler are brought into contact with each other at a gas-liquid contact portion to regenerate them. In a device for absorbing carbon dioxide gas in exhaust gas having a regeneration tower, the gas-liquid contact parts are arranged in series in a height direction and are arranged in series, and the carbon dioxide-rich absorption liquid is placed at the top of each of the gas-liquid contact parts. An apparatus for absorbing carbon dioxide gas in exhaust gas, characterized in that it is provided with a supply means. 2. An absorption tower that absorbs carbon dioxide gas in exhaust gas by using a circulating absorption liquid, and a carbon dioxide-rich absorption liquid from the absorption tower and steam from a reboiler are brought into contact with each other at a gas-liquid contact portion to regenerate them. In a device for absorbing carbon dioxide gas in exhaust gas having a regeneration tower, the gas-liquid contact portion is composed of a plurality and is arranged in series in the height direction, and the carbon dioxide rich absorbent is supplied to the top of each gas-liquid contact portion. Means, a liquid reservoir arranged at the bottom of each of the gas-liquid contact portions, a liquid pipe communicating from each of the liquid reservoirs to the reboiler, and at the bottom of each of the gas-liquid contact portions from the reboiler. An apparatus for absorbing carbon dioxide gas in exhaust gas, comprising: a steam pipe communicating with the steam pipe.