Dynamic Simulation and Control Design for Pulverized-Coal-Fired Oxy-Combustion Power Plants

Abstract

Oxy-combustion is a technically feasible and economically competitive pathway for capturing CO₂ emissions from coal-fired power plants. However, it still faces with challenges for control and operation since combustion agents and plant configuration are altered. The paper focuses on investigating dynamic behavior and controllability of a pulverized-coal-fired oxy-combustion power plant through dynamic simulation and control system design which is based on a systematical top-down analysis and bottom-up design method. In the proposed control structure, feed-forward control structure for oxygen product purity in air separation unit, flue gas O₂ control structure for favorable combustion, cascade control loops for maintaining steam temperatures in boiler island, and double temperature control structure for CO₂ compression and purification unit are designed to obtain effective and safe operation. A high ramp rate (5 %/min) process is applied to validate the complex control system, and it is found that dynamic model runs smoothly and all the objective parameters are maintained around their setpoints or reached to a new steady-state value. Comprehensive dynamic model with specified control system provides guidelines for engineers to operate commercial oxy-combustion power plants.