Comprehensive evaluation of a CO2-capturing high-efficiency power generation system for utilizing waste heat from factories

Abstract

SUMMARYIt is becoming more important to realize CO 2 -capturing power generation systems (PGSs) for drastically decreasing an amount of CO 2 emission into the atmosphere. However, net power generation efficiency (NPGE) of a CO 2 -capturing system has been considered to be greatly deteriorated, since capturing CO 2 requires extra energy. This paper proposes a new CO 2 -capturing PGS that has a high-efficient NPGE by utilizing waste heat from factories. As an example of a waste heat, exhaust gas with temperature 2001C from refuse incinerator plants is adopted. In the proposed system, the temperature of saturated steam produced by utilizing the waste heat is raised by combusting fuel with the use of pure oxygen in a combustor, and is used as the main working fluid of a gas turbine PGS. It is estimated that the proposed system has a fuel-to-electricity NPGE of 59.3%, when turbine inlet temperature (TIT) is assumed to be 10001C. The economics of the proposed system is also evaluated and the CO 2 reduction cost is estimated to be small; 4.16 U.S. $ t À1 CO 2 compared with 32.1 U.S. $ t À1 CO 2 for a conventional steam turbine PGS. It is shown that CO 2 -capturing is not cost consuming but becomes to be profitable owing to improved power generation characteristics, when its TIT is increased from 1000 to 12001C.

Characteristics and Economics Evaluation of an H2O Turbine Reheat Cycle Power Generation System Based on Oxy-Combustion Method for Utilizing Exhaust Gas of Large Scale MCFC

“…Since the main compositions of the combustion gas become only H 2 O and CO 2 , the separation of CO 2 gas from H 2 O liquid (condensate) can be physically and automatically performed at the outlet of the condenser at the bottoming cycle in the proposed system [3][4][5][6][7][8][9][10].…”

“…This feature is fundamentally different from a system that captures CO 2 from flue gas by using a chemical absorbent, in which power output inevitably decreases and its powerselling income decreases. The proposed system is based on GT technologies, and as such it could be easily applied to small scale [1] and medium scale PGSs [9], as well as to large scale PGSs [10]. The fuel is burned by using O 2 and therefore the combustion reaction takes place in the combustor without N 2 gas.…”

“…The fuel is burned by using O 2 and therefore the combustion reaction takes place in the combustor without N 2 gas. Hence, no thermal NO x is produced in the proposed system when carbon hydride fuel is used [3][4][5][6][7][8][9][10]. Table 2.…”

“…Tables 2 and 3 show major exogenous variables and parameters used for estimating the characteristics of the STPS and the HTPS, and the values used for characteristics simulation, respectively. The values in Tables 2 and 3 are based on previous analyses performed by the authors on a variety of power generation systems, and are considered to be realizable by applying present technologies [3][4][5][6][7][8][9][10]. Table 4.…”

“…Unit power cost, depreciation year, benefit-cost ratio (BCR) and internal income rate of return (IRR), which indicates the average return rate of the invested capital, were adopted in the present research. Table 5 shows the values assumed for performing economic evaluation [3][4][5][6][7][8][9]; for simplicity of conversion, Japanese yen was converted into US dollar at a rate of 100 yen = 1 US $. Regenerator and condenser costs are taken into consideration as an additional facility cost for the HTPS, since these units do not exist in the conventional GT PGSs [1].…”