Performance prediction of a circulating fluidized bed boiler by heat exchangers block simulation at varying load conditions

Abstract

We propose a simplified mathematical model to describe and to predict the performance of a circulating fluidized bed boiler under varying loads. The model is a systematic approach for modeling a circulating fluidized bed boiler, which is a combination of zero-dimensional energy and mass balance model of heat exchanger blocks. Blocks of heat exchangers are integrated with the air–gas side, the water–steam side, and the solids side. Validation has been carried out by comparing calculated results with experimental data of a pilot-scale circulating fluidized bed boiler. In order to expand throughout the actual operating range, a correlation between the solids circulation rate and the superficial velocity was drawn, and overall heat transfer rates at varying loads were interpreted as representative heat transfer coefficients related with the suspension density. Boiler efficiencies and temperatures were predicted at the loads. Finally, partial load behavior of the boiler was investigated by characterizing performance parameters. This simulation model is hoped to improve the understanding of the boiler performance when operation parameters are selected.