In this paper, modeling and simulation of the unsteady-state SO2 converters with one or two inter-stage heat exchangers have been done. Effects of the input SO2 concentration, the superficial velocity, the cycle duration of the flow reversal, and the heat removal capacity of the inter-stage heat exchangers, and even the inert packing sections sandwiching the catalyst bed, have been discussed. The results obtained show considerable performance improvements by using the inter-stage heat removal over the adiabatic unsteady state converters for the relatively concentrated gases involving SO2.