Dynamic performance simulation of a USC-CFB boiler system

Abstract

In this study, a physics-based dynamic model of a USC-CFB boiler system, where the supercritical steam flow is interrelated with the solid-gas flow, is proposed. In this model, the total boiler system is divided into a number of heat exchanger models, where the solid-gas flow and steam flow are discretized to accommodate the complicated physical phenomena of the USC-CFB boiler. The supercritical steam flow is closely connected to the solid-gas flow in terms of heat transfer in the discretized cells. Especially, the physical phenomena of the fluidized bed furnace such as the solid hydrodynamics of the core-annulus model, combustion reactions, and heat transfer mechanism of the solid and gas flow are applied. By utilizing the proposed model, the dynamic behavior of the USC-CFB boiler is investigated by simulating the mass and energy flows and the heat transfer rates according to the various dynamic events. In particular, this model quantitatively assessed the effect of the solid behavior on the temperatures of the CFB loop under various operating conditions. Improved understanding of the performance of the CFB loop can contribute to predict the dynamic behavior of the CFB plants. In addition, the dynamic performance of the USC-CFB boiler system was quantitatively investigated by simulating the steam temperature under various load change rates. The effect of the circulating solids on the steam temperature was evaluated by adjusting the inlet solid flow into the external heat exchanger. The plant performance data generated through the model-based simulation can be used for the efficient and safe operation of the power plant system.