Slug flow model for coal combustion and desulfurization in fluidized beds: theoretical formulation

Abstract

A model is developed for coal combustion in fluidized beds including devolatilization under slugging conditions, with sulfur removal effected by a sorbent of limestone or dolomite. The gasflow analysis is based on the slug flow theory of Hovmand and Davidson with modifications to account for the bubbling region below the point where slug formation starts. Solids are assumed to be back-mixed, and for this condition, char-size distributions and sorbent sulfate loadings in the bed are determined. The gaseous reactant balances are carried out for both oxygen and sulfur dioxide under plug flow conditions, with the reaction rates based on coal size and sorbent sulfate loading. The expressions for the combustion efficiency and sulfur reaction are derived.