Ph.D, Indian Institute of Technology Guwahati
CO2 as gasifying medium will progress Boudouard reaction (C+CO2->2CO), calorific value gas
Increase in the demand of energy and the depletion of fossil fuels drag the attention towards the utilization of deep unmined coal resources . Due to the huge availability of coal resources worldwide, the gasification technology of coal plays an important role for the energy production . The gasification of coal leads to the production of high calorific valuable gases such as hydrogen, carbon monoxide, methane and lighter hydrocarbons, which can be directly used for the power generation or for the production of various chemical feed stocks in chemical industries. Underground coal gasification (UCG) is a feasible technology for the utilization of deep underground coal resources without any ash disposal problem as compared to the conventional gasification technologies . The UCG technology also paves a way for the storage of CO2 in deep coal seam cavity after exploiting its coal resources . Therefore, the UCG integrated carbon capture and storage (CCS) is a feasible solution for the sequestration of carbon gas after the utilization of its chemical energy. The UCG is an in-situ clean coal technology, which converts the unmineable coal into valuable calorific value gases effectively without much environmental pollution. Indian coals have high ash content and therefore, mining, transporting and washing of coals for the gasification process would result in an uneconomic operation. Further, it would lead to land, water and air pollution . In India, around 37% of the coal resources are found at a depth more than 300 m. In order to exploit these resources, UCG is found to be a promising technology Oxidizing/gasifying agents play an essential role in the economy of underground coal gasification (UCG). The selection of feed gas to UCG depends on the prevailing conditions and inherent properties of coal seam. Steam based UCG operation leads to transportation and operational difficulty for efficient gasification. Alternatively, CO2 gas is a potential gasifying medium for coal gasification and this option may avoid energy losses in a UCG seam.Thus, in the current research, borehole coal combustion and gasification experiments are carried out to simulate CO2 enhanced UCG system. The syn gas produced will be CO enriched which will be further integrated with conventional and advanced power generating system. Also UCG experiments are simulated in laboratory scale using CO2/O2 and the results are compared with pure oxygen and oxygen enriched air based UCG operation.
Abstract: O2/CO2 based underground coal gasification (UCG) is a promising clean coal technology for the exploitation of deep underground coal resources with a minimal difficulty of the operation. However, the generated syngas of the underground is enriched with carbon monoxide and it should be converted into a clean gas on the above ground for the end use. In the present study, a clean mode of power generation is proposed using the CO enriched UCG syngas. Firstly, the UCG gas is reformed into pure hydrogen using chemical looping reforming (CLR) method. Secondly, the pure hydrogen obtained from CLR process is used suitably to generate electric power in a proton exchange membrane fuel cell (PEMFC) system. Hence, carbon energy is converted into hydrogen energy through the CLR technique and this clean gas is efficiently transformed into electrical energy using the PEMFC system. A net efficiency for converting CO enriched gas into H2 through conventional system using water gas shifting reactors is evaluated and compared with the CLR system. An energy analysis of O2/CO2 based UCG integrated with CLR-PEMFC shows 43.6% net efficiency with carbon capture and storage (CCS).
Pub.: 28 Sep '16, Pinned: 24 Aug '17
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