Experimental demonstration of control strategies for a Gas Switching Combustion reactor for power production with integrated CO2 capture

This paper reports on operational control strategies for a Gas Switching Combustion (GSC) reactor concept for power generation with integrated CO2 capture. This concept uses a single reactor where air and gaseous fuel feeds are alternated into a bed of oxygen carrier. No external solids circulation is required in this concept and thereby many technical and scale-up challenges that are encountered in the conventional Chemical Looping Combustion processes based on interconnected fluidized bed systems are circumvented. A first demonstration of this concept has shown that the reactor temperature undergoes large variations across the redox cycle due to the highly exothermic reaction of air with the oxygen carrier. This paper presents and demonstrates the experimental feasibility of a number of heat management techniques implemented in order to minimize the temperature variation and thereby improve the electric efficiency of the GSC concept when integrated into a combined cycle power plant. Three heat management strategies have been devised based on theoretical calculations; two of them involve air feed dilution using nitrogen while the third uses a secondary air injection point to force part of the air feed during the oxidation stage to slip through the bed without reacting with the oxygen carrier. The three investigated heat management strategies succeeded to greatly reduce the temperature rise across the redox cycle although to different extents. However, the one with the secondary concentrated air injection shows greater economic potential for implementation in the GSC reactor, since it does not require a depleted air recirculation that is required for the two other strategies. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.