Pressurised Chemical Looping Combustion (PCLC): Air Reactor design

Abstract

Bioenergy combustion with Carbon Capture and Storage (BECCS) is a key technology to achieve carbon negative emissions power generation. This can be achieved by coupling the biofuels combustion with CO2 capture and storage (CCS). The lowest cost for CCS corresponds at the moment to the Chemical Looping Combustion (CLC) process. This can use biofuels which can be gaseous (biomethane, biogas or syngas etc.), liquid (biodiesel, bioethanol, biobutanol and pyrolysis oils etc.) or solids (wood dust, charcoal dust, wood chips, wood pellets etc.) While plant design with gaseous and liquid biofuels would be simpler, plants using solid biofuels and based on two couple fluidisd beds would need the use of a third reactor named carbon stripper. In the specific case if we plan to couple a CLC plant with a turbo expander (to achieve the high efficiencies of a combined cycle power plant) we have to work with pressurized reactors. However, there are some technical barriers to the coupling of a chemical looping combustor with a turbo expander, such as: the operation of the combustor in pressurised conditions; the inventory balance among reactors; elutriated particles reaching the turbo expander. This explaind why there is no commercial plant at the moment capable to do this. The aim of this paper is to present a model for the dimensioning of an air reactor to be coupled to a turbo expander of the power of about 12 MWe. Based on this, the air mass flow can be obtained and the geometric parameters can be calculated, to have an air velocity which is needed to achieve the fast fluidization regime and to ensure a high conversion rate as well as particles and heat exchage among air and fuel reactor.

Dimensioning Air Reactor and Fuel Reactor of a Pressurized Chemical Looping Combustor to Be Coupled to a Gas Turbine: Part 1, the Air Reactor

“…These numbers are correspondent t the order of magnitude of the velocities, which are reported in Kronberger et al, 2005 [15 The solids volume fraction in the air reactor is presented in Figure 6. Velocities profiles inside the air reactor, adapted from (using logarithmic scale) [55].…”