A simplified model Of SO2 capture by limestone in 71 MWe pressurized fluidized bed combustor

摘要

A mathematical model Of SO2 capture by uncalcined limestone particles with solid attrition under pressurized fluidized bed combustion conditions was developed based on the shrinking unreacted-core model. Since the thickness of the product layer is sufficiently much smaller than the particle size, a flat surface model was employed. The difference in SO2 capture behavior between continuous solid attrition and intermittent attrition was investigated. The reaction rate for intermittent solid attrition was found to be lower than that for continuous attrition mode under low SO2 concentration conditions. A simple mathematical expression to calculate reaction rate Of SO2 capture per unit external surface area of limestone is proposed. The present simplified mathematical model of SO2 capture by single limestone particle under periodical attrition conditions was applied to the analysis of a large-scale pressurized fluidized bed combustor. By giving the period of attrition as a parameter, the experimental results agreed well with the model results. From the vertical concentration profile Of SO2 concentration, the emission of SO2 was found to be governed by the balance between SO2 formation rate from char and SO2 capture by limestone at the upper surface of the dense bed. A simplified expression to estimate SO2 emission from pressurized fluidized bed combustors was proposed. (C) 2002 Elsevier Science Ltd. All rights reserved. [References: 11]