Self-optimizing control and safety assessment to achieve economic and safe operation for oxy-fuel combustion boiler island systems

Abstract

Oxy-fuel combustion is a promising carbon capture, utilization and storage (CCUS) method to reduce CO2 emissions in power plants. However, it faces with the issues of high energy-cost penalties and operating risks. In this work, a combined control optimization and safety analysis are applied to optimize the control and operation of oxy-fuel combustion boiler island system. To maximize the specific operating profit, a new self-optimizing control structure is proposed to optimize the selection of desirable controlled variables. This control structure shows a robust controllability and maintains a maximum specific operating profit around 28.7 $/tCO2. Moreover, the operating profit exhibits an opposite tendency to load change, increases with the increasing oxygen supply purity and keeps constant in presence of air leakage. The failure of oxygen concentration controller causes some fluctuations on the dynamic behavior of operating parameters at water-steam and flue gas sides. The loss of oxygen flow control loop leads to a larger effect on the dynamic responses of operating parameters than the fault of oxygen concentration control loop during load change and oxygen supply purity change operating scenarios. The results provide a new route to improve control reliabilities, reduce operating costs and guide safe operations for oxy-fuel combustion systems.