Thermodynamic analysis of solar energy integrated underground coal gasification in the context of cleaner fossil power generation

Underground coal gasification (UCG) is an in-situ physico-chemical process for the conversion of deep coal resources into useful product gas. The UCG process is inherently a clean coal technology avoiding several difficulties of conventional coal mining process. However, it is a complex in-situ phenomenon depending on site-specific geological parameters. Energy loss occurs in a UCG process due to water influx, underground cavity pressure drop, gas loss to the surrounding strata and high temperature gasifying medium, which are major challenges of UCG operation. These losses can be compensated if UCG is integrated with solar energy, which is a renewable and a cleaner source of energy. In the present study, two types of low pressure UCG based power plants are conceptualised using solar energy – (i) a conventional steam turbine cycle consisting of a high pressure, a medium pressure and a low pressure turbine and (ii) a gas turbine cycle with supercritical carbon dioxide (sCO2) as a working fluid operating in a combined cycle power plant system. The scope of integration of solar power on the UCG based power plant systems is discussed for cleaner energy production. A detailed thermodynamic analysis is carried out to estimate the thermal efficiency of both cycles for cases with and without the integration of solar energy. A net thermal efficiency of the solar-UCG based steam turbine cycle is found as 28.2% with carbon capture and storage (CCS). The solar-UCG based sCO2 gas turbine cycle shows a high net thermal efficiency of 32.9% with CCS, which is 4% higher than the respective system without having solar energy utilization.

[1]  Ata D. Akbari,et al.  Thermoeconomic analysis & optimization of the combined supercritical CO2 (carbon dioxide) recompression Brayton/organic Rankine cycle , 2014 .

[2]  Malin Song,et al.  Comprehensive efficiency evaluation of coal enterprises from production and pollution treatment process , 2015 .

[3]  Jahar Sarkar,et al.  Optimization of recompression S-CO2 power cycle with reheating , 2009 .

[4]  Sudip Ghosh,et al.  Thermodynamic performance study of an integrated gasification fuel cell combined cycle—an energy analysis , 2003 .

[5]  Yu Qian,et al.  Environmental impact and techno-economic analysis of the coal gasification process with/without CO2 capture , 2014 .

[6]  V. Prabu,et al.  INTEGRATION OF UNDERGROUND COAL GASIFICATION WITH A SOLID OXIDE FUEL CELL SYSTEM FOR CLEAN COAL UTILIZATION , 2012 .

[7]  David A. Bell,et al.  Coal Gasification and Its Applications , 2010 .

[8]  Ali Abbas,et al.  A novel modeling approach to optimize oxygen–steam ratios in coal gasification process , 2015 .

[9]  Vaclav Dostal,et al.  A supercritical carbon dioxide cycle for next generation nuclear reactors , 2004 .

[10]  Peter Harriott,et al.  Unit Operations of Chemical Engineering , 2004 .

[11]  Eugeniusz Krause,et al.  SEMI TECHNICAL UNDERGROUND COAL GASIFICATION (UCG) USING THE SHAFT METHOD IN EXPERIMENTAL MINE BARBARA , 2012 .

[12]  K. S. Reddy,et al.  4-E (Energy, Exergy, Environment, and Economic) analysis of solar thermal aided coal-fired power plants , 2010 .

[13]  Markus Eck,et al.  Thermal storage concept for solar thermal power plants with direct steam generation , 2014 .

[14]  Sanjay M. Mahajani,et al.  Underground coal gasification: A new clean coal utilization technique for India , 2007 .

[15]  V. Prabu.  Integration of in-situ CO2-oxy coal gasification with advanced power generating systems performing in a chemical looping approach of clean combustion , 2015 .

[16]  O. Le Corre,et al.  Environmental performance assessment of retrofitting existing coal fired power plants to co-firing with biomass: carbon footprint and emergy approach , 2015 .

[17]  Y. Kato,et al.  Medium temperature carbon dioxide gas turbine reactor , 2004 .

[18]  Sreenivas Jayanti,et al.  Optimized enriched CO2 recycle oxy-fuel combustion for high ash coals , 2012 .

[19]  Soteris A. Kalogirou,et al.  Parabolic trough collector system for low temperature steam generation: Design and performance characteristics , 1996 .

[20]  Soteris A. Kalogirou,et al.  Solar thermal collectors and applications , 2004 .

[21]  Gholamreza Zahedi,et al.  Underground coal gasification: From fundamentals to applications , 2013 .

[22]  Ricardo Vasquez Padilla,et al.  Exergetic analysis of supercritical CO2 Brayton cycles integrated with solar central receivers , 2015 .

[23]  Kristin M. Brown.  IN SITU COAL GASIFICATION: AN EMERGING TECHNOLOGY 1 , 2012 .

[24]  Rafig Azzam,et al.  Development of a techno-economic model for dynamic calculation of cost of electricity, energy demand and CO2 emissions of an integrated UCG–CCS process , 2014 .

[25]  Andrea Lazzaretto,et al.  Innovative biomass to power conversion systems based on cascaded supercritical CO2 Brayton cycles , 2014 .

[26]  Ambuj D. Sagar,et al.  Carbon mitigation in the indian coal-power sector: Options and recommendations , 2009 .

[27]  V. Prabu,et al.  CO2 enhanced in-situ oxy-coal gasification based carbon-neutral conventional power generating systems , 2015 .

[28]  Antonio Rovira,et al.  Performance study of solar power plants with CO2 as working fluid. A promising design window , 2015 .