Dynamic Tests and Results in an Oxy-fuel Circulating Fluidized Bed Combustor with Warm Flue Gas Recycle

As one of the most promising technologies for carbon capture and storage (CCS) in coal-fired power plants, oxy-fuel circulating fluidized bed (CFB) has received increasing attention. Most of the research on oxy-fuel CFB has been focused on simulations or experiments that fall under the steady-state behavior study. This research focuses on the dynamic behaviors in a 50 kWth oxy-fuel circulating fluidized bed combustor (CFBC) with warm flue gas recycle, where the oxygen concentration in the primary oxidant streams is in the range of 21-25 vol %. Dynamic step change tests concerning the coal feed rate and coal type were conducted. The dynamic response indicates that both the coal feed rate step change and coal type impact the bed temperature and oxygen concentration in the oxy-fuel CFBC. Additional units, such as air separation unit (ASU), bring new effects to the system dynamics in oxy-combustion, which can potentially result in increased time delay and low rate of change in the dynamic response of temperatures. In the dynamic tests, the oxygen concentration in the flue gas fluctuates in the form of a sinusoidal wave because of the fast volatile combustion and the delay in the char ignition. The system dynamics during the air-oxy transition and after a shutoff of the coal flow were also investigated in this work.