JPH07241440A - Waste combustion gas purifying method and device therefor - Google Patents

Abstract

PURPOSE:To remove CO2 in a waste combustion gas without lowering the combustion efficiency. CONSTITUTION:The waste gas from a combustor 1 such as a boiler is brought into contact with an aq. alkanolamine soln. as an absorbent liq. in a CO2 absorption tower 12 to absorb CO2, the absorbent liq. having absorbed CO2 is heated in a regeneration tower 18 to drive off the CO2 and regenerated, the regenerated absorbent liq. is circulated to the tower, and the waste combustion gas is purified. In this process, the absorbent liq. having absorbed CO2 is heated by the heat retained by the waste gas and the condensation heat of the steam in the waste gas in a first heater 25. Meanwhile, the heated absorbent liq. is heated by the heat retained by the high-temp. waste gas immediately after leaving the combustor such as a boiler to drive off CO2 in the regeneration tower and regenerated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for purifying combustion exhaust gas, and more particularly to a combustion exhaust gas capable of highly efficiently and efficiently removing dust particles, sulfur oxides and carbon dioxide gas in combustion exhaust gas such as boilers. The present invention relates to a purification method and device.

[0002]

2. Description of the Related Art From the viewpoint of preventing air pollution and pollution, in a large apparatus for burning fossil fuel such as petroleum or coal containing a relatively large amount of sulfur, such as a boiler for power generation, dust and sulfur in exhaust gas are included. Oxides (SO ₂ and SO ₃ or less, S
Many electric dust collectors and wet flue gas desulfurizers are installed to remove and reduce O _x ). FIG. 6 is a diagram showing a system flow of a conventional boiler exhaust gas dedusting and wet flue gas desulfurization apparatus.

Exhaust gas emitted from the boiler 1 is collected by the electric dust collector 2
Is removed by dust and cooled to approximately 90 ° C by the gas / gas heater 4.
After being treated, it is introduced into the desulfurization device 5, and SO in the exhaust gas_XStone
Ash (CaCO₃) Containing gypsum (CaSO_Four)
Are removed and recovered. SO _XHarmless discharge with minutes removed
After the moisture is removed by the demister 6, the gas is
It is reheated by the gas heater 4 and released into the atmosphere from the chimney 8.
It Insert fans 3 and 7 in the middle, push in the gas, and suck
ing.

A flue gas purification system that combines such an electric dust collector and a lime-gypsum method wet flue gas desulfurization device can reduce the concentration of exhaust dust to 30 mg / Nm ³ or less and has a high desulfurization rate of 95% or more, There is also an advantage that secondary plaster can be used, which is very useful for preventing air pollution and many plants are operating. However, recently, there is a movement and a demand to regulate the amount of discharged dust particles to 5 mg / Nm ³ or less, which is about 1/6 of the conventional amount.

Further, from the viewpoint of preventing or suppressing global warming
Carbon dioxide (CO₂) Request to separate and collect
Is increasing. Figure 7 shows alkanolamines (example
For example, the absorption method using an aqueous solution of monoethanolamine)
CO in exhaust gas₂Assembling the removal device into the boiler exhaust gas purification system
It is a figure which shows the integrated system flow. Desulfurization equipment 5, Mi
Exhaust gas discharged from the Statcher 6 is blower 10 and cooler
CO via 11₂Introduced into absorption tower 12
CO in liquid-gas contact₂To absorb. CO ₂Removed
The discharged exhaust gas passes through the amine cleaning system 15 and the thermistor 16.
Therefore, after the amine and water in the gas have been removed, the boiler
Returned to the exhaust gas flue and reheated by the gas / gas heater 4.
After that, it is discharged from the chimney as harmless gas by the fan 7.
On the other hand CO ₂The amine aqueous solution that absorbed
Of the high temperature that was sent and regenerated by the heat exchanger 17 in the regeneration tower 18.
CO after being heated by heat exchange with the amine absorbing liquid₂Expulsion
It is then sent to the regeneration tower 18. CO₂At the playout tower 18
Is the high temperature heated in the heat exchanger 17 in the reboiler 20.
The warm amine absorption liquid is heated by steam, and the amine absorption liquid
To CO₂Is banished. The expelled CO₂Gas is
The mist is removed by the strike separator 19 and pure CO₂Recovery
Collected in system 22. CO₂Absorbed amine absorption liquid
Is cooled by the heat exchanger 17 and the cooler 11 and then sucked.
CO is returned to the collecting tower₂Used for absorption of.

By attaching such an absorption method CO ₂ removal device to the exhaust gas purification system, 90% or more of CO ₂ in the exhaust gas can be removed, and a CO ₂ gas of high purity of 99.9% or more can be recovered.

[0007]

In order to prevent global warming, it is necessary not to increase CO ₂ in the atmosphere any more, and the most practical method for achieving this is relatively It is to establish a technology for removing and recovering CO ₂ from a thermal power plant that produces a large amount of exhaust gas from a fixed location.

CO ₂ can be recovered by installing the CO ₂ removal / recovery system using the above-mentioned amine solution in the boiler exhaust gas purification system as shown in FIG. 7, but the problem with this system is that CO ₂ CO from absorbed amine liquid
That is, a large amount of heat energy is required to expel ₂ . Usually, CO ₂ cannot be expelled unless it is heated to 90 to 120 ° C., so part of the high temperature steam of the boiler is diverted to the heating source. For this reason, it is said that the power generation efficiency is reduced by 10% or more in trial calculation. Since the power generation efficiency of the current coal-fired thermal power plant is around 40%, if the efficiency becomes less than 30%, the energy loss will be too large to be realized.

Therefore, the greatest problem in removing and recovering CO ₂ from boiler exhaust gas is that a large amount of energy is required, and an object of the present invention is to solve this problem of the prior art. Moreover, in the prior art, the gas discharged from the desulfurization device was reheated by a gas / gas heater or the like and released to the atmosphere from the chimney at 70 ° C. or higher, but this is a small amount (<30 mg / Nm ³ ) of exhaust gas. This is because the untreated dust particles are contained in it, and the temperature is raised in order to disperse them in the distance. If the amount of dust particles can be reduced to an extremely low level (eg <5 mg / Nm ³ ), the exhaust gas temperature can be lowered as compared with the prior art, and more boiler exhaust gas heat can be recovered.

[0010]

In order to achieve the above object, the invention claimed in the present application is as follows. (1) flue gas is contacted with the absorption liquid with an aqueous alkanolamine solution in a CO ₂ absorption tower to absorb the CO ₂ of the combustion exhaust gas, CO ₂ purge by heating the absorbent solution that has absorbed the CO ₂ In the method for purifying combustion exhaust gas in which CO ₂ is expelled and regenerated in the regeneration tower and then circulated to the CO ₂ absorption tower, the absorption liquid having absorbed the CO ₂ is used to heat the combustion exhaust gas by using a heat exchanger for heating the absorption liquid. And a method for purifying combustion exhaust gas, which comprises heating by utilizing the heat of condensation of liquid vapor in the combustion gas, and then regenerating the CO _{2 in a} regeneration tower.

(2) A dust collector for removing dust particles in the combustion exhaust gas, and a desulfurization device for removing sulfur oxides in the exhaust gas,
CO for absorbing and removing CO ₂ in the exhaust gas by using an absorbing liquid
In the combustion exhaust gas purifying apparatus that includes a ₂ removing device, by heating the absorbent solution that has absorbed CO ₂ by the hot exhaust gas immediately after exiting from the combustion device sends a CO ₂ purge regenerator CO ₂
Absorbing liquid final heater, dust collector for removing dust particles in the exhaust gas heat-recovered by the final heater, and heating the CO ₂ absorbing liquid extracted from the CO ₂ absorption tower by the exhaust gas exiting the dust collector A first heater for CO ₂ absorbing liquid that recovers the heat of condensation of vapor in the exhaust gas, a wet exhaust gas desulfurization device that removes sulfur oxides in the exhaust gas that exits the first heater, and a desulfurization device. And a CO ₂ absorption tower that absorbs and removes CO _{2 in} the exhaust gas using an absorption liquid, and the absorption liquid heated by the CO ₂ absorption liquid first heater is heated by the absorption liquid regenerated by the CO ₂ discharge regeneration tower a heat exchange device for feeding the CO ₂ absorbing solution final heater After, CO ₂ absorbing liquid final heater CO ₂ absorbing liquid that has been heated by the CO ₂ removal acceptance the absorbing solution in CO ₂ purge regeneration tower and A combustion exhaust gas purifying device characterized by being provided.

(3) A dust collector for removing dust particles in the combustion exhaust gas, and a desulfurizer for removing sulfur oxides in the exhaust gas,
CO for absorbing and removing CO ₂ in the exhaust gas by using an absorbing liquid
_In a combustion exhaust gas purifying apparatus equipped with a ₂ removal device, an integrated exhaust gas heat recovery CO ₂ that heats the absorption liquid that has absorbed CO ₂ by the high temperature exhaust gas immediately after it leaves the boiler and expels CO ₂ in the absorption liquid A discharge tower, an apparatus for spraying a calcium compound desulfurizing agent and water to the exhaust gas heat-recovered by the integrated exhaust gas heat recovery CO ₂ discharge tower, and an electrostatic precipitator for removing dust particles in the exhaust gas exiting the spray apparatus. , C extracted from the CO ₂ absorption tower by the exhaust gas leaving the electric dust collector
Wet exhaust gas by heating the O ₂ absorbing solution for removing the first heater CO ₂ absorbing solution for recovering heat of condensation of the vapors in the exhaust gas, sulfur oxides in the exhaust gas exiting the first heater A desulfurizer, a CO ₂ absorption tower for absorbing and removing CO _{2 in} the exhaust gas leaving the desulfurizer using an absorbing liquid, and the CO ₂ absorbing liquid first
The integrated exhaust gas heat recovery C for absorbing liquid heated by a heater
A combustion exhaust gas purifying apparatus, which is provided with a heat exchange device which is heated by a regenerated absorption liquid from an O ₂ purging tower and is supplied to the tower for integrated exhaust gas heat recovery CO ₂ purging.

[0013]

The operation of the constituent elements of the present invention will be described below. Each element number is a number in FIGS. 1 and 2 described later. The exhaust gas discharged from the coal-fired boiler 1 is usually at 200 to 300 ° C., and the CO ₂ absorbing amine heater (1) 23 is installed at the exhaust gas outlet to heat the amine liquid that has absorbed CO ₂ , Is cooled to 60-90 ° C. The exhaust gas cooled to 60 to 90 ° C. is introduced into a low temperature electrostatic precipitator to collect and remove coal ash and dust particles in the exhaust gas. An electric dust collector is usually installed in an exhaust gas atmosphere of 200 to 300 ° C., but a method of collecting dust at a low temperature of 60 to 90 ° C., in a sense of high humidity (low temperature electric dust collector) is more efficient, It has the advantage of reducing the amount of dust particles in the exhaust gas to 5 mg / Nm ³ or less.

The exhaust gas, which has been cooled to 60 to 90 ° C. and whose dust has been removed, is then sent to the CO ₂ absorption amine heater (2) 25 by the fan 3 and cooled to 30 to 50 ° C. Since the exhaust gas contains 10 to 15% of water vapor, water is condensed when cooled to 30 to 50 ° C., and the heat of condensation of water vapor can be recovered in addition to the temperature drop. In other words, the heat of recovery of exhaust gas can be effectively used for heating the amine liquid that has absorbed CO ₂ .

When the condensate is obtained by cooling the exhaust gas temperature to 30 to 50 ° C., which is much lower than the conventional temperature of 90 to 120 ° C., the recovery heat including the condensation heat can be utilized for the amine heating and the desulfurization apparatus 5 There is an advantage that the make-up water of the above can be reduced or eliminated, and the desulfurization reaction by the lime slurry can be promoted. Also in the wet flue gas desulfurization apparatus 5, when the exhaust gas temperature is cooled to a low temperature of 30 to 50 ° C., the temperature of the absorbing solution is also lowered, the desulfurization reaction can be promoted, and there is an advantage in terms of the performance of the desulfurization apparatus.

Exhaust gas from which sulfur oxides have been removed by the desulfurization device 5 and water has been removed by the mist catcher 6 is CO
_The CO ₂ is removed in the ₂ absorption tower 12, and becomes an extremely clean and harmless gas containing only nitrogen, oxygen and water of vapor pressure, and is discharged from the chimney 8. The amine liquid having absorbed CO ₂ is conveyed by the pump 13 and heated by the CO ₂ absorption amine heater (2) 25, the heat exchanger 17 and the CO ₂ absorption amine heater (1) 23, and the CO ₂ displacement regeneration tower. CO ₂ is expelled at 18 and is returned to the CO ₂ absorption tower 12 via the heat exchanger 17 again.

Particularly, the point of the present invention is that CO
_{(2) An} absorption amine heater is provided in the exhaust gas heat recovery system so that the heat of the boiler exhaust gas is used to the maximum extent possible for heating the amine absorption liquid. When the boiler exhaust gas heat is not sufficient to drive CO _{2 out of the} amine absorbing solution, it is also necessary to install the reboiler 20 and supplement the boiler auxiliary steam as shown in FIG.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a flow of a high performance and high efficiency flue gas purification system according to the present invention, and FIG. 2 shows details of the system flow. When the devices are listed by the flow of exhaust gas, boiler 1, C
O ₂ absorption amine heater (1) 23, low temperature electrostatic precipitator 2
4, fan 3, CO ₂ absorption amine heater (2) 25, desulfurization device 5, mist catcher 6, blower 10, CO ₂
The absorption tower 12, the amine cleaning system 15, the fan 7, and the chimney 8 are used.

Along the flow of the CO ₂ absorbing amine liquid,
A CO ₂ absorption tower 12, a pump 13, a CO ₂ absorption amine heater (2) 25, a heat exchanger 17, a CO ₂ absorption amine heater (1) 23, a CO ₂ removal regeneration tower 18, and a reboiler 20 are installed. . In FIG. 2, between the CO ₂ absorption amine heater (1) 23 and the low temperature electrostatic precipitator 24, lime (CaC
Although an O ₃ ) or slaked lime (Ca (OH) ₂ ) supply system 26 and a water spray system 27 are described, by installing such devices, a desulfurization reaction occurs in the low temperature electrostatic precipitator 24, and a part thereof is generated. Alternatively, most of the SO _x are to be removed in advance, but it is within the scope of the present invention whether or not these devices are installed.

The advantages and features of the system of the present invention are:
It is possible to use the heat quantity of exhaust gas as effectively as possible.
CO₂Can reduce the amount of heat required to drive the
Reduce power generation efficiency at power stations from 40 to 30% or less as before
Can be reduced to a few percent or less
It In the system of the present invention, a gas / gas heater is installed
Desulfurization and CO removal ₂Generated exhaust gas is relatively low
Exhausted from the chimney at a temperature (30-50 ° C). Harmful gas
Emitting exhaust gas that does not contain liquefied natural gas
Boiler that burns (LNG) or LNG combustion gas turbine
Heat recovery steam generator (HRSG)
And there is no problem. From another perspective, LNG-fired
Dust and SO in exhaust gas such as boilers_xDoes not include
In the stem, a low temperature electrostatic precipitator or desulfurizer is not necessary.
CO in exhaust gas₂Only remove and collect
It Therefore, in the case of LNG burning, low temperature electricity
Dust collector 24, fan 3, desulfurization device 5, mist catcher
-6, lime or slaked lime supply system 26, water spray system 27
However, this system also belongs to the present invention.

FIGS. 3 and 4 show another embodiment of the flow of the high performance and high efficiency flue gas purification system according to the present invention. Figure 3
Is the C for the high-performance and high-efficiency flue gas purification system of FIG.
An exhaust gas heat utilization CO ₂ removal regeneration tower 28 in which an O ₂ absorption amine heater (1) and a CO ₂ removal regeneration tower are integrated is installed at the boiler outlet. The system of FIG. 3 is the same as that of FIG. 2 in terms of thermal efficiency, but the number of devices can be reduced, which is effective for space saving and compactness.

CO is generated by the heat of the boiler exhaust gas₂Which has absorbed
When heating the aqueous mining solution, the coal-fired boiler exhaust gas is C
O₂The gas is the most and the water is little
Gets stricter. CO targeting coal-fired boilers
₂Heat recovery when concentration: 12%, water: 10%
Describe the calculation result. CO in boiler exhaust gas₂Absorption method
The system for removing and recovering is usually L / G (where L is the absorption liquid cycle).
Circulation flow rate, G is the flow rate of exhaust gas)
Quantity; 10⁶Nm ³/ h, liquid circulation amount; 3.5 × 10³m³/ h
In this case, if heat is recovered until the exhaust gas temperature is lowered by 100 ° C, CO
₂The absorption liquid can be heated up to about 10 ℃ and heated up to 200 ℃.
When collected, the temperature can be raised by about 20 ° C. Also, about 10 in exhaust gas
% Of water vapor is included, and the exhaust gas temperature is 30 to 50 ° C.
When it is cooled to the temperature below and the water vapor is condensed, the heat recovery rate is 90%.
Assuming CO₂The absorption liquid can be heated up to 12 ° C
It Conventional CO₂In the absorber, the amine absorbing liquid temperature is 30
CO at ~ 50 ° C₂Up to 70 ° C in the heat exchanger 17
Heat and heat to 100-120 ° C with a reboiler
₂However, in the system of the present invention, the boiler discharge
Utilizing the heat of water, CO₂Absorption amine heater (1) (2)
Since the absorption liquid can be heated up to 20 to 30 ° C in the reboiler,
It suffices to heat 0 to 20 ° C, and
It can be reduced to 3 to 1/5 and power generation efficiency can be reduced to 1/3 to 1 of the conventional one.
It can be / 5.

[0023] Figure 4, CO ₂ purge CO also heat the CO ₂ gas discharged from the regenerator 18 (usually 90 to 120 ° C.)
It is intended to further improve the thermal efficiency by using it for heating the ₂ absorption amine, and the CO ₂ absorption amine heater (3) 29 is installed in place of the cooler 11 attached to the upper part of the CO ₂ removal regeneration tower 18. is there. The system of FIG. 4 can further reduce the decrease in power generation efficiency.

In the conventional system, the power generation efficiency was reduced from 40% to 30% when the CO ₂ removal device was installed, but the use of the system of the present invention reduced the power generation efficiency by 1/3.
Since it can be reduced to ⅕, it can be operated with a power generation efficiency of 33 to 38%. Fig. 5 shows that LN is used as boiler fuel.
7 shows a flow chart of a CO ₂ removal system in exhaust gas when using a fuel that does not generate SO _x or dust such as G. Since the exhaust gas does not contain SO _x or dust particles, the desulfurization device 5 and the low-temperature electrostatic precipitator 24 are not required, and therefore the system is removed. This system also belongs to the present invention.

[0025]

By using the high-performance and high-efficiency flue gas purification system according to the present invention, CO ₂ in exhaust gas discharged from a boiler for thermal power generation can be removed without causing a large energy loss and a reduction in power generation efficiency. Yes, it can contribute to the prevention of global warming. In addition, because the electric dust collector and desulfurization device are placed in a lower temperature section than before, dust removal and desulfurization efficiency is improved,
If it is the same size, the performance will improve, and if it is the same, it can be made compact.

According to the present invention, the absorption-type CO ₂ removal and recovery device can be made practical.

[Brief description of drawings]

FIG. 1 is a flow chart of a high performance and high efficiency flue gas purification system according to the present invention.

FIG. 2 is a flow chart of a high performance and high efficiency flue gas purification system according to the present invention.

FIG. 3 is another embodiment of the high-performance and high-efficiency flue gas purification system flow according to the present invention.

FIG. 4 is another embodiment of the high-performance and high-efficiency flue gas purification system flow according to the present invention.

FIG. 5 is another embodiment of the high-performance and high-efficiency flue gas purification system flow according to the present invention.

FIG. 6 is a flow chart of a boiler exhaust gas purification system according to a conventional technique.

FIG. 7 is a flow chart in which a CO ₂ removal and recovery device by an amine absorption method is installed in a boiler exhaust gas purification system which is a conventional technique.

[Explanation of symbols]

1 ... boiler, 3 ... blower fan, 5 ... desulfurizer, 6 ... mist catcher, 7 ... induction fan, 8 ... chimney, 10 ... blower, 11 ... cooler, 12 ... CO ₂ absorption tower, 13 ... pump, 14 ... absorbent Liquid supply system, 15 ... Amine cleaning system, 16 ...
Demister, 17 ... Heat exchanger, 18 ... CO ₂ drive-out regeneration tower, 19 ... Mist separator, 20 ... Heater (reboiler), 22 ... Pure CO ₂ recovery system, 23 ... CO ₂ absorption amine heater (1), 24 ... low temperature electrostatic precipitator, 25 ... CO ₂ absorption amine heater (2), 26 ... lime or slaked lime supply system, 27 ... water spray system, 28 ... exhaust gas heat utilization CO ₂ drive-out regeneration tower, 29 ... CO ₂ absorption amine heater (3).

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C01B 31/20 B

Claims (3)

[Claims] 1. The combustion exhaust gas is brought into contact with an absorption liquid using an alkanolamine aqueous solution in a CO ₂ absorption tower to absorb CO ₂ in the combustion exhaust gas, and the absorption liquid absorbing the CO ₂ is heated to produce CO. _{In the} method for purifying combustion exhaust gas in which CO ₂ is expelled and regenerated in the repulsion regeneration tower and then circulated in the CO ₂ absorption tower, the absorption liquid that has absorbed the CO ₂ is converted into combustion exhaust gas by using a heat exchanger for heating the absorption liquid. After heating by using the retained heat and the condensation heat of the liquid vapor in the combustion gas, CO
₂ Combustion exhaust gas purification method characterized by regeneration in a drive-out regeneration tower. 2. A dust collector for removing dust particles in combustion exhaust gas, a desulfurization device for removing sulfur oxides in the exhaust gas, and CO ₂ for absorbing and removing CO _{2 in the} exhaust gas by using an absorption liquid.
In a flue gas purifying apparatus equipped with a removing device, a CO ₂ absorbing solution final heater that heats an absorbing solution that has absorbed CO ₂ by high-temperature flue gas immediately after it leaves the combustion apparatus and sends it to a CO ₂ scavenging regeneration tower, A dust collector that removes dust particles in the exhaust gas heat-recovered by the final heater, and the CO ₂ absorbing liquid extracted from the CO ₂ absorption tower by the exhaust gas that exits the dust collector to heat the condensation heat of the vapor in the exhaust gas. A first heater of the CO ₂ absorbing liquid to be recovered, a wet exhaust gas desulfurization device for removing sulfur oxides in the exhaust gas discharged from the first heater, and absorption of CO _{2 in} the exhaust gas discharged from the desulfurization device Absorbs and removes using liquid C
A heat exchange device that heats the absorption liquid heated by the O ₂ absorption tower and the CO ₂ absorption liquid first heater by the absorption liquid regenerated by the CO ₂ discharge regeneration tower, and then sends it to the CO ₂ absorption liquid final heater When the combustion exhaust gas purifying apparatus is characterized by providing a CO ₂ purge regeneration tower for removing CO ₂ acceptance the absorbent solution in the CO ₂ absorbing liquid that has been heated by the CO ₂ absorbing solution final heater. 3. A dust collector for removing dust particles in combustion exhaust gas, a desulfurizer for removing sulfur oxides in the exhaust gas, and CO ₂ for absorbing and removing CO _{2 in the} exhaust gas by using an absorption liquid.
In a combustion exhaust gas purifying apparatus equipped with a removal device, an integrated exhaust gas heat recovery CO ₂ expelling method for heating the absorption liquid that has absorbed CO ₂ by the high-temperature exhaust gas immediately after it leaves the boiler and expelling CO ₂ in the absorption liquid A tower, an apparatus for spraying a calcium compound desulfurizing agent and water to the exhaust gas heat-recovered by the integrated exhaust gas heat recovery CO ₂ drive tower, an electrostatic precipitator for removing dust particles in the exhaust gas exiting the spray apparatus, CO extracted from the CO ₂ absorption tower by the exhaust gas discharged from the electric dust collector
Wet flue gas desulfurization to remove the first heater CO ₂ absorbing solution by heating the ₂ absorbing solution to recover heat of condensation of the vapors in the exhaust gas, sulfur oxides in the exhaust gas exiting the first heater Apparatus, a CO ₂ absorption tower that absorbs and removes CO _{2 in} the exhaust gas leaving the desulfurization apparatus using an absorption liquid, and the CO ₂ absorption liquid first
The integrated exhaust gas heat recovery C for absorbing liquid heated by a heater
A combustion exhaust gas purifying device, comprising: a heat exchange device that is heated by a regenerated absorption liquid from an O ₂ discharge column and is supplied to the integrated type exhaust gas heat recovery CO ₂ discharge column.