Flue Gas Desulphurization at Low Temperatures Using Coal Fly Ash/Ca-Based Sorbent:Determination of Rate Limiting Step

摘要

A kinetic model for flue gas desulphurization (FGD) using siliceous sorbent was carried out using various different potential/exponential expressions for the rate equation and structural/volumetric expressions for the solid phase equation. The kinetic parameters of the mathematical model were obtained from a series of desulphurization experimental reactions conducted under isothermal conditions at various operating parameters. MATLAB software was utilized to solve the partial differential equations using the finite difference method. It was found that the rate limiting step is a combination of reaction and ash diffusion, in which the former dominates initially and the latter dominates at the later reaction stage. Pre-exponential factor of rate constant, ko, and activation energy, Ea, have been determined as 0.15 s?1 and 15,052 J/mol?1, respectively. As a result, a modified shrinking core model with reaction control coupled with exponential expression of the rate equation was found to best describe the experimental data with an error of 4.8%.