Comparison of Equilibrium-Stage and Rate-Based Models of a H2S Scrubber for Purification of Coke Oven Gas

Abstract

In recent years, one of the most important challenges worldwide is to meet increasingly stricter environmental regulations while maintaining the profitability of plants. Modelling particular parts of existing technologies can help efficient operation, reduce energy consumption, minimize emissions, and keep operating costs low. Furthermore, adequately validated models provide the opportunity to examine different equipment designs, operating parameters side by side without hindering the technological process. The coke oven gas purification technology of a Hungarian coke oven plant was studied in this research work. As a by-product of coke production, approximately 40,000 - 60,000 m3 crude coke oven gas is generated every hour, which has to be cleaned before being used for energy purposes. First, the cooled crude coke oven gas is fed into the hydrogen sulfide scrubber in a counter-current flow. Then, the hydrogen sulfide is absorbed in an ammonia-rich washing liquid coming from the following two ammonia scrubbers. In this study, two mathematical models, equilibrium-stage and rate-based models, were used to simulate the removal of H2S from coke oven gas in the Aspen Plus process simulator program. The validation of the models was performed by using the operating measurements of the outlet streams. The results closely approximate the measured composition of the outflows. However, the simulation results predicted by the rate-based model show better agreement than the equilibrium model compared with the experimental data. With the use of the rate-based model, a sensitivity analysis was made, taking into account the parameters that have a tremendous impact on the cleaning process and can also be controlled by appropriate intervention. The creation of this model was the first step in building the simulation of the entire gas purification process, which will be used to optimize the operation and create an operator training system.