Control of An Oxy-fuel Capture and Purification Unit For Coal-Based Power Plants

Oxy-fuel combustion is a promising CO2 mitigation technology that will allow the continued utilisation of abundant coal reserves in the power sector in a carbon-constrained world. The CO2 capture and purification unit (CO2CPU) is an important unit that determines the CO2 product quality and energy consumption of the oxy-fired power plants. Several studies have been published on this unit but information on the dynamic behaviour of the CO2CPU is limited. This study developed a dynamic model of the pilot- scale CanmetENERGY's CO2CPU (CanCO2). Dynamic modelling of the CO2CPU is challenging due to the highly-integrated flow sheet structure and the occurrence of two phase flow heat transfer in heat exchangers. This study takes into account the property variation in the two phase region while calculating the heat transfer coefficients in heat exchanger models. Detailed mathematical models are provided and transient analyses were performed to gain insight into the dynamic behaviour of the CO2CPU. Dynamic data obtained from the transient analysis was used to design a suitable control scheme for this process and study the dynamic operability of this process in closed-loop. A decentralized multi-loop control scheme for the CO2CPU is proposed based on the Relative Gain Array (RGA) method. The performance of the proposed control structure was evaluated for both disturbance rejection and set point tracking scenarios. Stable closed loop responses were obtained.