Evaluation of the reduction of CO2 emissions from a coal–to–liquids utilities plant by incorporating PBMR energy

Abstract

Due to the constantly growing environmental concerns about global warming, there is immense pressure on the coal-to-liquids (CTL) industry to lower carbon dioxide emissions. This study evaluates the cogeneration of electricity and process steam, using coal and nuclear heat obtained from a High Temperature Gas Cooled Reactor (HTGR) such as a Pebble Bed Modular Reactor (PBMR), for the use in a CTL plant. Three different cogeneration processes were investigated to resolve what influence nuclear cogenerated electricity and process steam would have on the carbon dioxide emissions and the unit production cost of electricity and process steam. The first process investigated utilises coal as combustion medium and an extraction/condensing steam turbine, together with the thermodynamic Rankine cycle, for the cogeneration of electricity and process steam. This process was used as a basis of comparison for the nuclear based cogeneration processes. The second process investigated utilises nuclear heat generated by a HTGR and the same power conversion system as the coal-based cogeneration system. Utilising a HTGR as a heat source can decrease the carbon dioxide emissions to approximately zero, with a 91.6% increase in electricity production cost. The last process investigated is the nuclear-based closed cycle gas turbine system where a gas turbine and Brayton cycle is coupled with a HTGR for the cogeneration of electricity and process steam. It was found on technical grounds that this process would not be viable for the cogeneration of electricity and process steam. The unit production cost of electricity and process steam generated by each process were determined through an economic analysis performed on each process. Overall it was found that the CTL industry could benefit a great deal from utilising nuclear heat as a heat source.