Dynamic model for subcritical circulating fluidized bed boiler-turbine units operated in a wide-load range

Abstract

As the proportion of renewable energy generation increases in power grid, most of circulating fluidized bed (CFB) boiler-turbine units are required to operate in a wide-load range to maintain the stability of power grid. However, few studies focus on modeling of CFB units operated in a wide-load range, especially in ultra-low load. This study develops a dynamic model for subcritical CFB boiler-turbine units operated in a wide-load range, which can provide foundation for designing flexible operation mode. In this work, different characteristics of subcritical CFB units in ultra-low load were analyzed. Then, the model structure with balance between complexity and accuracy was derives from mass and energy conservation laws as well as thermodynamic principles. The parameters and functions in model were identified based on running data from a 330 MW subcritical CFB unit. Validation results show that the of model has satisfactory accuracy in wide-load range, from ultra-low load to full load. Besides, the model can reflect essential dynamic characteristics of the unit. Therefore, the model can be feasible for performance analysis and testing control strategy.