Optimization of Coke Oven Gas Desulfurization and Combined Cycle Power Plant Electricity Generation

Many steel refineries generate significant quantities of coke oven gas (COG), which is in some cases used only to generate low pressure steam and small amounts of electric power. In order to improve energy efficiency and reduce net greenhouse gas emissions, a combined cycle power plant (CCPP) where COG is used as fuel is proposed. However, desulfurization is necessary before the COG can be used as a fuel input for a CCPP. Using a local steel refinery as a case study, a proposed desulfurization process is designed to limit the H2S content in COG to less than 1 ppmv, and simulated using ProMax. In addition, the proposed CCPP plant is simulated in Aspen Plus and is optimized using GAMS to global optimality with net present value as the objective function. Furthermore, the carbon tax is considered in this study. The optimized CCPP plant was observed to generate more than twice the electrical efficiency when compared to the status quo for the existing steel refinery. Thus, by generating more electricity within the plant gate, the need to purchase electricity reduces, and hence reducing the lifecycle of CO2 emissions considerably.