Due to the need to meet stringent environmental regulations and to minimize capital and operating costs, the design and operation of coke-oven-gas (COG) desulfurization processes must be optimized. For H,S scrubbers, this paper presents a rigorous rate model that accounts for not only mass and heat transfer mechanisms, but also complex and reversible chemical reactions involving H2S, CO2 NH3 and associated ions. The model need not use a chemical enhancement factor based on simplified reaction mechanisms. This model can be extended to simulation of NH3 scrubbers, deacifiers and NH3 stills of COG desulfurization processes.