A thermodynamic investigation of gasification coupled chemical looping combustion (CLC) of carbon (coal) is presented in this paper. Both steam and CO2 are used for gasification within the temperature range of 500–1200°C. Chemical equilibrium model was considered for the gasifier and CLC fuel reactor. The trends in product compositions and energy requirements of the gasifier, fuel reactor, and air reactor were determined. Coal (carbon) gasification using 1.5？mol H2O and 1.5？mol CO2 per mole carbon at 1 bar pressure and 650°C delivered maximum energy (？390.157？kJ) from the process. Such detailed thermodynamic studies can be useful to design chemical looping combustion processes using different fuels. 1. Introduction Coal is the most abundantly available cheap fossil fuel worldwide and its reserves are estimated to outlast oil and natural gas reserves [1]. Coal is mainly used for energy generation: in coal fired power plants to produce electricity [2], hydrogen [3–5], and syngas production for FT synthesis or fuel cells [6, 7]. Combustion of coal or coal derived syngas in air results in generation of product gas mixture containing CO2, N2, and [8]. The separation of CO2 from such gaseous streams is extremely difficult and expensive. Hence these product gases are directly vented to the atmosphere without CO2 separation. This environmental pollution is a major drawback of energy generation from coal. CO2 emissions from such processes are mainly responsible for global warming and climate change phenomenon [9]. The 2010 CO2 emissions have increased to 389.0？ppm and burning of fossil fuels is one of the main causes as reported by the World Meteorological Organization [10]. Such tragic scenarios were foreseen and therefore research in clean energy generation using coal had already started globally. Chemical looping combustion (CLC) technology is a result of such research efforts. CLC uses a solid oxygen carrier (OC) to oxidize the carbon and hydrogen present in the fuel to CO2 and H2O, respectively, in an endothermic fuel reactor. Oxides such as NiO, CuO, and Fe2O3 and sulphates such as CaSO4 have been widely used as oxygen carriers in chemical looping processes. The reduced OC is regenerated by air oxidation in an exothermic air reactor [11, 12]. Both the reactors are interconnected and operate simultaneously. The energy released in the CLC system is of similar magnitude as direct combustion, but with a crucial advantage of having CO2 and nitrogen streams completely separated [13, 14]. The pure CO2 steam can be captured/sequestered easily thereby reducing CO2
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