Abstract
The concern on the effect of global warming due to greenhouse gases has been increasing. Carbon dioxide is the most powerful greenhouse gas and more than 40% of its emission is from fossil fuelled power plants. So the efficient use of fossil fuel with carbon dioxide capture is the best method for achieving the energy demands with less pollutant emissions. But the conventional capture technologies are more energy intensive and cause a drop in net power production. This energy penalty can be overcome by using Chemical looping combustion technique. In this technique, combustion occurs in two reactors Air reactor and Fuel reactor. The former is fluidised by air and the later by fuel. Metal oxides called oxygen carriers loop in between two reactors carrying oxygen and heat required for combustion to the fuel reactor. So there is no direct contact between air and fuel and results in pure combustion products-carbon dioxide and water. Therefore a separate air separation or gas separation unit is not required which are energy eating units in conventional capture methods. This work presents steady state simulations of three systems: Integrated Gasification Combined Cycle power plant (i) without carbon dioxide capture, (ii) with pre-combustion capture and (iii) integrated with chemical looping combustion. All the simulations are carried out using Aspen plus simulation package. High ash Indian coal is used as the fuel. The performance of each case is compared in terms of overall energy efficiency and carbon dioxide capture rate. The efficiencies of the system without capture, with looping combustion and with pre-combustion capture are found to be 42.69%, 40.2% and 35.8% respectively. The respective capture efficiencies of looping combustion and precombustion capture are 99.97% and 94%. It can be seen that the reduction in the overall efficiency is marginal in the case of chemical looping combustion. This shows the superiority of chemical looping combustion technique over the pre-combustion capture technique in terms of higher capture efficiency and overall plant thermal efficiency. An exergy analysis is also carried out to identify the units having higher exergy destruction rates. Parametric studies are carried out on these units to observe their effect on the overall plant performance. Thus, a process for an energy efficient and environment friendly utilization of high ash Indian coal is presented in this paper.