JP2544554B2 - Method for removing CO2 in combustion exhaust gas - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently removing and recovering CO ₂ (carbon dioxide gas) contained in a combustion exhaust gas of a boiler in thermal power generation.

[0002]

2. Description of the Related Art In recent years, the greenhouse effect of CO ₂ has been pointed out as one of the causes of the global warming phenomenon, and countermeasures against it have become urgent internationally in order to protect the global environment. CO ₂
The sources of these are all human activity fields that burn fossil fuels, and their emission regulations are likely to be tightened in the future. As one of the countermeasures, a method of recovering CO _{2 in} combustion exhaust gas from a boiler and storing the recovered CO ₂ without releasing it to the atmosphere are targeted at power generation facilities of thermal power plants that use large amounts of fossil fuels. The method is being actively researched.

By the way, the applicant of the present application has previously proposed a process of removing CO ₂ contained in combustion exhaust gas by reducing energy consumption and recovering it (Japanese Patent Application No. 1-3332854). ).

In FIG. 3, the boiler combustion exhaust gas containing CO ₂ from the boiler 1 is sent to the exhaust gas cooler 15 after being boosted by the boiler exhaust gas blower 14, and the cooling water 16
The cooling waste water 17 is discharged to the outside of the system by being cooled by the CO ₂ absorption tower 18.

[0005] In the CO ₂ absorber 18, the combustion exhaust gas is alternating contact with CO ₂ absorbing liquid 19 that has been reproduced based on alkanolamine, CO ₂ in the combustion exhaust gas is absorbed in the CO ₂ absorbing liquid 19 by a chemical reaction It The exhaust gas 21 from which CO ₂ has been removed is released outside the system. The CO ₂ absorbent 20 that has absorbed CO ₂ is pressurized by the rich solvent pump 22, heated by the absorbent regenerated by the rich / lean solvent heat exchanger 23, and supplied to the CO ₂ absorbent regeneration tower 24. .

[0006] are heated in the CO ₂ absorbing solution regeneration tower 24 a lower portion of the CO ₂ absorbing liquid low-pressure steam extracted from the low pressure turbine 7 at reboiler 30 (3kg / cm ² absolute pressure) 13. CO ₂ accompanied by water vapor is guided to the overhead condenser 25 from the top of the CO ₂ absorbent regeneration tower 24. The condensed water condensed in the reboiler 30 is reboiler condensate pump 32.
Is mixed with the boiler feed water that has been boosted in pressure and preheated to raise the temperature of the boiler feed water, and the boiler feed water is supplied to the boiler 1.

[0007] CO ₂ accompanied the released steam from the top of the CO ₂ absorbing solution regeneration tower 24 was preheated by the overhead condenser 25 the boiler feed water boosted by the boiler feed water pump 12, cooled by an overhead cooler 26, Water is separated in the separator 27, and CO ₂ is guided to another process through a line 28 and collected. The water separated by the separator 27 is converted into CO ₂ by the condensed water circulation pump 29.
It is supplied to the absorption liquid regeneration tower 24.

The regenerated CO ₂ absorbent is pressurized by the lean solvent pump 31, cooled by the CO ₂ absorbent which has absorbed CO ₂ in the rich / lean solvent heat exchanger 23, and then by the lean solvent cooler 39. It is further cooled and supplied to the CO ₂ absorption tower 18.

On the other hand, the high-pressure, high-temperature steam 2 generated and heated by the boiler 1 drives the high-pressure steam turbine 3 and is then heated as a high-pressure steam turbine exhaust 4 by the reheater 5 in the boiler 1 and reheated. The medium pressure steam 6 is sent to the low pressure turbine 7.

Low-pressure turbine extraction air 13 is supplied from the low-pressure portion of the low-pressure turbine 7, supplied to the reboiler 30, the low-pressure turbine exhaust 9 is condensed in the condenser 10, and condensed water 11 is condensed by the boiler feed pump 12 into an overhead condenser 25. Sent to.

Examples of alkanolamines that absorb CO ₂ include aqueous solutions of monoethanolamine, diethanolamine, triethanolamine, methyldiethanolamine, diisopropanolamine, diglycolamine and the like, and mixed solutions thereof. An aqueous solution of ethanolamine is preferably used.

By adopting the above method, the power generation efficiency is lowered as compared with the case where CO ₂ is not removed, but it is possible to suppress the degree to a low level. That is, as an example, when 90% of CO ₂ in the exhaust gas of a natural gas fired power plant boiler is removed, and when a heat source for heating the reboiler 30 is obtained by combustion, it corresponds to 18.9% of the combustion heat amount of the power plant boiler. Need fuel to do. Therefore, the power generation efficiency with respect to the amount of combustion heat is reduced by 6.3% from 36.4% when CO ₂ is not removed to 30.1%.
However, according to the method proposed above, steam of 3 kg / cm ² absolute pressure is extracted from the low-pressure steam turbine 7, the reboiler 30 is heated by this steam, and the boiler feed water can be heated by the condensed water of this steam. By performing heat exchange between the boiler feed water and CO ₂ accompanied by steam from the CO ₂ absorbent regeneration tower in the overhead condenser, the extraction air for heating the boiler feed water can be reduced. Therefore, although the shaft power of the low-pressure steam turbine was reduced, the power generation efficiency with respect to the combustion heat quantity could be reduced to 4.5%, and the power generation efficiency could be improved by 1.8%. Similarly, it was revealed that an improvement of 3.4% can be achieved when a combined cycle gas turbine is adopted.

[0013]

By adopting the method proposed above, it is possible to minimize the decrease in power generation efficiency associated with CO ₂ removal / recovery, but it is intended to apply it to an existing thermal power plant. In this case, since steam is extracted from the turbine, it is necessary to modify the turbine, which causes a problem of large-scale construction.

[0014]

SUMMARY OF THE INVENTION In view of the above circumstances when the power generation is performed while absorbing and removing CO ₂ contained in combustion exhaust gas discharged from a boiler, the present inventors
As a result of earnest study, it is possible to solve the above problems by supplying exhaust gas of a steam turbine that drives a compression or cooling compressor for liquefying the recovered CO ₂ or steam extracted from the steam turbine to a reboiler as a heating source. The present invention has been completed and the present invention has been completed.

That is, the present invention is as follows: (1) CO _{2 in} the exhaust gas of a boiler for generating steam for driving a steam turbine is absorbed and removed by a CO ₂ absorbing liquid, and the removed CO ₂ is liquefied by compression and cooling. with stores, the CO ₂ absorbent that has absorbed CO ₂ in a system for reproducing in a CO ₂ absorbing solution regeneration tower having a reboiler, from the exhaust steam or steam turbine of a steam turbine which drives a compressor or cooling compressor CO ₂ A method for removing CO _{2 from} combustion exhaust gas, characterized in that the extracted steam is supplied to a reboiler as a heating source for regeneration of the CO ₂ absorbent.

(2) The steam turbine is a high-pressure steam turbine and
And low-pressure steam turbine.
Branch from the air line or low pressure steam turbine supply steam line
Method of removing CO ₂ in the combustion exhaust gas according to the above 1, which comprises using was to steam obtained driving the steam turbine which drives a compressor or cooling compressor CO _2. Is. Hereinafter, the present invention will be described in detail with reference to the drawings.

[0017]

1 and 2 are process diagrams illustrating the CO ₂ removal method of the present invention. 1 and 2, only the main equipment is shown and the auxiliary equipment is omitted. If necessary, tanks, valves, pumps, heat exchangers, etc. are provided. Devices having the same reference numerals as those in FIG. 3 indicate the same devices.

In FIG. 1, a branch line 40 is provided in the steam line 6 for the low-pressure steam turbine reheated by the boiler, and the steam is used to use the steam turbines 41 and 4 in FIG.
Drive 3 The line 40 may be provided by branching to the line 4 that returns from the high-pressure turbine 3 to the boiler 1.
If a medium-pressure turbine is provided, its exhaust steam line may be branched.

The CO ₂ separated by the separator 27 of FIG. 1 is compressed by the compressor 42 of FIG. 2 by the line 28, cooled by the cooler 46, and then dehydrated in the dehydration step 47. The dehydrated CO ₂ is further cooled by the cooler 48 and stored in the liquefied CO ₂ tank 52. The steam turbine 43 shown in FIG. 2 is a compressor 4 for compressing a refrigerant.
4 is provided to drive the compressed refrigerant and heat exchanger 49
It is cooled by the drum 50 and received by the drum 50, and is flash-cooled by the flash pulp 51 and supplied to the cooler 48.

In order to collect and store the CO ₂ absorbed / removed in the process of FIG. 1 in a liquid state in this way, as shown in FIG. 2, compressors 42, 4 for compressing and cooling CO ₂ are used.
4 is required. Electric power is used as the drive power source for these, and although it may be possible to use a motor, use steam used in the turbines 3 and 7 installed in the same plant just by branching the line. Therefore, by using a steam turbine as in the present invention,
It has a great effect. In the present invention, the drive steam for the steam turbines 41, 43 is not necessarily limited to the steam branched from the turbines 3, 7 etc. originating from the boiler 1, but these steams are used as shown in the figure. Is preferred.

The present invention is characterized in that the steam discharged from the steam turbines 41 and 43 for driving these compressors or the steam extracted is used as a heating source of the reboiler 30. Steam turbines 41, 4
It is considered that 3 is often newly installed in addition to the existing power generation equipment for the recovery of carbon dioxide gas. Therefore, the construction accompanying the adoption of the method of the present invention is also carried out from the existing turbine 7 or the like for extraction. This can be performed relatively easily as compared with the case of the previously proposed method which must be performed.

[0022]

As described in detail above, according to the present invention, the decrease in power generation efficiency is minimized, and
It is possible to operate the carbon dioxide absorption device to absorb and remove carbon dioxide, and to generate electricity while recovering it, without having to make major modifications to existing equipment.

[Brief description of drawings]

FIG. 1 is a partial process diagram illustrating a CO ₂ removal method of the present invention.

FIG. 2 is a partial process diagram illustrating the CO ₂ removal method of the present invention.

FIG. 3 is a process diagram illustrating a conventional CO ₂ removal method.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Zenji Hotta 3-3-22 Nakanoshima, Kita-ku, Osaka-shi Kansai Electric Power Co., Inc. (72) Inventor Kenji Kobayashi 3-2-22-2 Nakanoshima, Kita-ku, Osaka Kansai Inside Electric Power Company (72) Kunihiko Yoshida 3-11-20 Wakao-ji Temple, Amagasaki Kansai Electric Power Company (72) Inventor Shigeru Shimojo 3-11-20 Wakao-ji Temple, Amagasaki Kansai Electric Power Company Within the Research Institute of Technology (72) Inventor Mutsunori Karasaki 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Heavy Industries, Ltd. Head Office (72) Inventor Masaki Iijima 2-5-1, Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Heavy Industries, Ltd. Head Office (72) Inventor Toru Seto 4-2-2 Kannon Shinmachi, Nishi-ku, Hiroshima-shi Hiroshi Research Institute, Mitsubishi Heavy Industries, Ltd. (72) Inventor Oka KaoruAkira Hiroshima Nishi-ku Kan'onshin-cho, chome No. 6 No. 22 Mitsubishi Heavy Industries, Ltd. Hiroshima the laboratory (56) Reference Patent flat 4-350303 (JP, A) JP flat 3-193116 (JP, A)

Claims (2)

(57) [Claims] Claim: What is claimed is: 1. Generate steam for driving a steam turbine.
CO in boiler exhaust gas₂CO₂Absorption removal with absorption liquid
CO removed₂Compressed and cooled to liquefy and store
As well as CO₂CO absorbed₂Absorption liquid reboiler
CO with ₂In the system regenerated in the absorption liquid regeneration tower, C
O₂Steam turbine for driving compressors for compression or cooling
The steam discharged from the bottle or the steam extracted from the steam turbine
CO₂Supply to reboiler as a heat source for regeneration of absorbent
CO in combustion exhaust gas characterized by₂How to remove
Law. 2. The steam turbine comprises a high pressure steam turbine and a low steam turbine.
It consists of a pressure steam turbine,
In or out of the low pressure steam turbine supply steam line
Method of removing CO ₂ in the combustion exhaust gas according to claim 1, wherein the steam obtained is characterized by using the driving of the steam turbine to drive the compressor or cooling compressor CO ₂ Te.