JPH0626362A - Co2 gas turbine cycle - Google Patents

Abstract

PURPOSE:To eliminate excessive CO2 by a low-priced means and improve heat efficiency by diverging part of exhaust gas flowing to a waste heat recovery boiler from a gas turbine in a CO2 gas turbine cycle or part of exhaust gas flowing to a compressor from an exhaust gas condenser, and leading it to an excessive CO2 eliminator supplied with magnetite as a catalyst. CONSTITUTION:Part of exchaust gas flowing to a waste heat recovery boiler 7 from a gas turbine 5 is led to an excessive CO2 eliminator 10. The CO2 eliminator 10 is supplied with active magnetite as a catalyst, and (CH4+2O2) is generated under the existence of steam to eliminate CO2. The generated CH4 reaches a combustor 3 through a cooler 11 and a compressor 12, and O2 is led to an O2 compressor 2 through a cooler 13. As another means, part of exhaust gas flowing to a compressor 4 from an exhaust gas condenser 8 can be led to the excess CO2 eliminator 10. CO2 is thus eliminated by a low-priced means, and the generated CH4 and O2 are made into fuel and combustion oxygen to improve the heat efficiency of a plant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a CO ₂ gas turbine cycle, and more particularly to a system for removing surplus CO ₂ increased by combustion from a CO ₂ gas turbine cycle system.

[0002]

_2. Description of the Related Art As a conventional CO ₂ gas turbine cycle, there is one proposed by the present applicant as Japanese Patent Application No. 3-68070, and its outline will be described with reference to FIG.

[0003] In FIG. 3, O ₂ where N ₂ is separated in the air by O ₂ production apparatus 1 is pressurized in O ₂ compressor 2 is supplied to the combustor 3, fuel is burned. A gas turbine forming a semi-closed cycle is composed of a compressor 4 and a gas turbine 5, and CO ₂ circulates. That is, the CO ₂ compressed by the compressor 4 is heated by the combustor 3 to reach a high temperature and expanded by the gas turbine 5. The gas turbine 5
The generator 6 is driven together with the compressor 4. The exhaust gas discharged from the gas turbine 5 is then steam-generated in the exhaust heat recovery boiler 7, moisture is removed in the exhaust gas condenser 8 acting as a precooler, and CO ₂ whose temperature has dropped is again compressed by the compressor 4 Run into the circulation cycle.

CO generated by combustion of fuel
_{Since 2} increases the amount of circulating gas, excess CO ₂ is extracted outside by the liquefaction separation device 9. That is, the compressor 4
The CO ₂ bypassed from the outlet of is introduced into the liquefaction separation device 9. CO ₂ pressure at the outlet of the compressor 4 is 14 ata
The saturation temperature at this pressure is about -40 ° C. On the other hand, the saturation temperature under atmospheric pressure is −78.5 ° C., which corresponds to the sublimation temperature of dry ice. Therefore, the gas-liquid separation under pressure is easier than the gas-solid separation method, and the power cost of the separation device can be reduced.

Incidentally, the CO ₂ removal rate (CO ₂ increase rate which becomes an excess due to O ₂ supplement) is usually about 20%. The low-temperature exhaust gas after liquefying and separating CO ₂ is returned to the inlet side of the compressor 4 to lower the compressor inlet gas temperature and reduce its driving power.

[0006]

The conventional CO ₂ gas turbine cycle as described above has the following problems. (1) The liquefaction separation apparatus for extracting CO ₂ from the system must cool CO ₂ to −40 ° C., and its operating cost is high. (2) The construction cost of the liquefaction separation device is high. (3) The extracted liquid CO ₂ is not used,
It is discarded while still having cold heat, reducing the thermal efficiency of the plant.

The present invention has been made in order to solve the problems of the prior art as described above, and it is possible to remove surplus CO ₂ by an inexpensive means without using a CO ₂ liquefaction separation device and to improve plant thermal efficiency. An object is to provide a CO ₂ gas turbine cycle made possible.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is characterized in that hot gas produced in a combustor is sequentially flown to a gas turbine, an exhaust heat recovery boiler, an exhaust gas condenser and a compressor. In a CO ₂ gas turbine cycle in which CO ₂ is circulated back to the combustor, a part of the exhaust gas flowing from the gas turbine to the exhaust heat recovery boiler or the exhaust gas flowing from the exhaust gas condenser to the compressor is branched to produce magnetite. It is designed to lead to a surplus CO ₂ removal device using the catalyst as a catalyst.

[0009]

According to the above means, the surplus CO ₂ is CO ₂ + 2H ₂ O + heat by the CO ₂ removing device using magnetite as a catalyst.
CH ₄ + 2O ₂ undergoes a chemical reaction to be removed. And
CH ₄ generated in this surplus CO ₂ removal device can be recovered as gas turbine fuel, and O ₂ can be recovered as combustion oxygen.

[0010]

Embodiments of the present invention will be described in detail below with reference to FIGS. FIG. 1 shows a first embodiment of the present invention,
FIG. 2 shows a second embodiment of the present invention, and the same parts as those shown in FIG. 3 are designated by the same reference numerals and their duplicated description will be omitted.

First, referring to FIG. 1, according to the first embodiment of the present invention, a portion of the exhaust gas flowing from before the exhaust heat recovery boiler 7, that is, from the gas turbine 5 to the exhaust heat recovery boiler 7, removes excess CO _2. It is led to the device 10. Activated magnetite is supplied as a catalyst to the CO ₂ removing device 10,
₂ is CO _{2 using} magnetite as a catalyst in the presence of water vapor.
+ 2H ₂ O + heat → CH ₄ + 2O ₂ undergoes a chemical reaction to be removed. Then, CH ₄ generated in the surplus CO ₂ removal device 10 is supplied to the combustor 3 via the cooler 11 and the compressor 12, and O ₂ is cooled by the cooler 13 and then sucked in by the O ₂ compressor 2. Be guided to the side.

Next, referring to FIG. 2, according to the second embodiment of the present invention, a part of the exhaust gas flowing after the exhaust gas condenser 8, that is, from the exhaust gas condenser 8 to the compressor 4 is a surplus of CO _2.
It is guided to the removing device 10. Activated magnetite is supplied as a catalyst to the CO ₂ removal device 10, and CO ₂ is CO ₂ + 2H _{2 using} CO ₂ as a catalyst in the presence of water vapor.
A chemical reaction of O + heat → CH ₄ + 2O ₂ is performed and removed.
CH ₄ generated in the surplus CO ₂ removal device 10 is supplied to the combustor 3 via the cooler 11 and the compressor 12, and O ₂ is cooled by the cooler 13 and then sucked in by the O ₂ compressor 2. Be guided to the side.

The chemical reaction between CO ₂ and magnetite is particularly likely to occur at a high temperature of 300 to 400 ° C., and the gas turbine exhaust gas before exhaust heat recovery usually has such a high temperature. The excess CO ₂ removal device 10 of the first embodiment shown in FIG. 1 is more than that of the second embodiment shown in FIG.
There is an advantage that operating costs can be reduced.

Further, as shown in each of FIG. 1 and FIG.
Preferably, N separated from O ₂ in the air by the O ₂ production apparatus 1 is used.
₂ is supplied to the combustor 3 at the time of start-up, whereby a large amount of O ₂ existing in the system at the time of start-up is forcibly replaced by N _2, and the reduction of the reducing power of active magnetite is prevented. There is.

[0015] That is, the active magnetite atom structurally unstable because highly reactive, e.g., compound binding is also decomposes CO ₂ → C + O ₂ in solid CO _2, the active magnetite surface C, O ₂ Is taken into the active magnetite deep layer to decompose CO ₂ . But,
At this time, if O ₂ is mixed with CO ₂ in the gas phase, the above reaction is caused by the oxidation reaction of active magnetite by O ₂ .
That action will be reduced. Therefore, when starting this O
By forcibly substituting ₂ for N ₂ , it is possible to prevent a reduction in the reducing power of active magnetite due to the above-mentioned alienation reaction.

[0016]

As described above, according to the present invention, the present invention returns the hot gas produced in the combustor sequential gas turbine exhaust heat recovery boiler to the combustor by flowing into the exhaust gas condenser and the compressor, CO ₂ In a CO ₂ gas turbine cycle in which the exhaust gas flowing from the gas turbine to the exhaust heat recovery boiler or the exhaust gas flowing from the exhaust gas condenser to the compressor is branched to generate excess CO ₂ using magnetite as a catalyst. It is designed to remove excess CO ₂ by introducing it to a removal device. Such an excess CO ₂ removal device that uses magnetite as a catalyst has lower operating costs and construction costs than conventional CO ₂ liquefaction separation devices. Is. Therefore, according to the present invention, the surplus O ₂ can be removed by an inexpensive means.

Further, CH ₄ generated in the surplus CO ₂ removal device
Is recovered as a gas turbine fuel and O ₂ is recovered as combustion oxygen, whereby the plant thermal efficiency can be improved. Furthermore, if N ₂ separated from O ₂ in the air is supplied to the combustor at the time of start-up in the O ₂ manufacturing apparatus, a large amount of O ₂ existing in the system at the time of start-up is forcibly replaced with N _2. Thus, it is possible to prevent a reduction in the reducing power of magnetite.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of a CO ₂ gas turbine cycle according to the present invention.

FIG. 2 is a system diagram showing another example of a CO ₂ gas turbine cycle according to the present invention.

FIG. 3 is a system diagram showing a conventional CO ₂ gas turbine cycle.

[Explanation of symbols]

1 O ₂ Manufacturing Equipment 2 O ₂ Compressor 3 Combustor 4 Compressor 5 Gas Turbine 6 Generator 7 Exhaust Heat Recovery Boiler 8 Exhaust Gas Condenser 10 Excess CO ₂ Removal Device 11 Cooler 12 Compressor 13 Cooler

Claims (4)

[Claims] 1. A sequential gas turbine the generated hot gas in the combustor, a heat recovery steam, flowing into the exhaust gas condenser and the compressor back to the combustor, the CO ₂ gas turbine cycle for circulating CO _2, A CO ₂ gas turbine cycle, characterized in that a part of the exhaust gas flowing from the gas turbine to the exhaust heat recovery boiler is branched so as to be guided to a surplus CO ₂ removal device using magnetite as a catalyst. 2. A sequential gas turbine the generated hot gas in the combustor, a heat recovery steam, flowing into the exhaust gas condenser and the compressor back to the combustor, the CO ₂ gas turbine cycle for circulating CO _2, A CO ₂ gas turbine cycle, characterized in that a part of the exhaust gas flowing from the exhaust gas condenser to the compressor is branched and guided to a surplus CO ₂ removal device using magnetite as a catalyst. 3. A CO ₂ gas turbine cycle according to claim 1 or 2, and O ₂ production apparatus for producing the O ₂ by separating the N ₂ from air, the O ₂ from the O ₂ production apparatus compressed And supplying O ₂ compressor to the combustor, CH ₄ generated in the surplus CO ₂ removal device is supplied to the combustor, and O ₂ is supplied to the suction side of the O ₂ compressor. A CO ₂ gas turbine cycle characterized by: 4. The CO ₂ gas turbine cycle according to claim 3, wherein N ₂ separated from O ₂ in the air by the O ₂ production apparatus is supplied to the combustor at the time of start-up. CO ₂ gas turbine cycle.