Absorption of hydrogen sulfide gas in ammoniacal solution of zinc chloride is accompanied with an instantaneous chemical reaction forming zinc sulfide precipitates. Such reactions are moat suited for operation of spray drying with reaction. A mathematical model for the system which incorporates chemical reaction, heat, mass and momentum transfer has been proposed. It is assumed that the gases and the spray droplets move in co-current plug flow mode end spray is considered monodiaperse for sake of simplicity. The differential equations derived for the modal have been solved as an initial value problem uslng the Runge-Kutta method. The variations of temperature, humidity, droplet diame-ter. moisture content and concentrations of reactants are pra-dieted along the length of the column and compared with exprimental data.