Patent ID: 8728423

Claim:
A method for flue gas treatment comprising: arranging an exhaust heat recovery boiler at a downstream side of a gas turbine; supplying the exhaust heat recovery boiler with the flue gas emitted from the gas turbine through a first line connecting the gas turbine with the exhaust heat recovery boiler; emitting the flue gas from the exhaust heat recovery boiler through a second line connected to the exhaust heat recovery boiler; branching from either one of the first line and the second line a part of the flue gas emitted from respective one of the gas turbine and the exhaust heat recovery boiler through a branch line connected to an auxiliary boiler; supplying the auxiliary boiler with fuel and at least the part of the flue gas; causing a combustion in the auxiliary boiler using the fuel and at least a part of the flue gas, thereby increasing a concentration of carbon dioxide in the flue gas; generating a high-pressure steam at the auxiliary boiler; emitting the flue gas from the auxiliary boiler through a third line connected to the auxiliary boiler; connecting the second line and the third line with a carbon dioxide recovery apparatus through a fourth line; combining the flue gas emitted from the auxiliary boiler with the flue gas emitted from the exhaust heat recovery boiler in the fourth line so that the carbon dioxide concentration of a combined flue gas is increased to a concentration range where the carbon dioxide recovering apparatus works efficiently; recovering carbon dioxide included in combined emission of the auxiliary boiler and the exhaust heat recovery boiler having increased carbon dioxide concentration in a carbon dioxide recovery apparatus; supplying a carbon dioxide compression apparatus with the carbon dioxide recovered in the recovering step and the high-pressure steam generated at the generating step; and compressing the carbon dioxide supplied using the high-pressure steam in the carbon dioxide compression apparatus, wherein the recovering step employs the high-pressure steam after being used in the compressing step for separating the carbon dioxide, and the method further includes returning steam condensate to the auxiliary boiler.