Conceptual design of a 100 MWth CLC unit for solid fuel combustion

Abstract

The conceptual design of a 100MWth unit for coal combustion with CO2 capture by in-situ Gasification Chemical Looping Combustion (iG-CLC) was done. Ilmenite was considered the oxygen carrier and a highly reactive sub-bituminous coal was the fuel. The main components of the iG-CLC unit were a fuel reactor, a carbon stripper and an air reactor. Mass and enthalpy balances were performed to determine the solids circulation flow rate, temperature of the reactors, steam and air requirements, and heat duty of heat exchangers. Fluid dynamics considerations and cyclones sizes were taken into account for the conceptual design and the dimensioning of these devices. In addition, optimized operating conditions obtained with a mathematical model were considered in the design procedure. Then, the performance of the iG-CLC unit was estimated with the model. Some benefits were identified when recirculated CO2 was used to fluidize the carbon stripper and fuel reactor, regarding both fuel reactor performance and energy integration of the iG-CLC system. Thus, a CO2 capture value of 95% with a carbon stripper with 98% efficiency and an oxygen demand in exit gases from the fuel reactor of 7% was predicted with a solids inventory in the fuel reactor of 750kg/MWth. Moreover, the energy penalty related to steam generation was minimized when H2O was replaced by CO2. Results presented in this work can be used to estimate the net efficiency of the plant in future works.