The impact of recycling portion of the desuffurized gas stream and the amt. of spray levels used in the absorber on the flue gas desuffurization efficiency was simulated. The recycling a part of the desuffurized stream gas resulted in increasing the efficiency of the process by approx. 1%, while the gas recycle, together with an increased no. of spray levels resulted in increasing the efficiency of gas purifn. by approx. 4%.