Dynamic modeling and control for pulverized-coal-fired oxy-combustion boiler island

Oxy-fuel combustion is one of competitive and promising carbon capture technologies for restraining CO2 emissions from power plants. Dynamic simulation of oxy-combustion system, which is essential for gaining its dynamic characteristics, can help to evaluate and improve process design, and to develop control system and operational strategies. This paper focuses on dynamic simulation and control design for a conceptual 600 MWe oxy-combustion pulverized-coal-fired boiler. The steady-state model using a pseudo coal to substitute real coal is established, validated, and then transformed into the dynamic model which uses pressure-driven solution. The control system, which aims to automatically regulating flue gas O2 concentration within reasonable range (2-7 mol.% in this study), is designed and applied to the dynamic boiler model. Three planned disturbances of load change, oxygen purity (from cryogenic air separation unit) ramp change and air in-leakage (from boiler) step change are conducted. Detailed dynamic behavior from water side and flue gas side is obtained and analyzed to help engineering operation in real plant. Mode switching process and alternative control strategy are simulated and discussed. Comprehensive dynamic model with specified control system provides possibility to study the dynamic characteristics of full-train oxy-combustion power plants.