Intensification of steam reforming process for off-gas upgrading and energy optimization using evolutionary algorithm

Abstract

H2 production by steam methane reforming (SMR) is an energy-intensive process at high reaction pressure and temperature. The objective of present work is to improve the efficiency of H2 production by optimizing turbine-integrated SMR-coal gasification process (SMRT-CG). The economic analysis of turbine-integrated SMR process (SMRT) was investigated with decision variables, such as flowrate of natural gas, reaction pressure, and turbine discharge pressure. The optimal price of H2 production was competitive after the addition of turbine. Genetic algorithm (GA) together with waste reduction (WAR) algorithm were used to evaluate the environmental impact of optimal SMRT. Optimization by non-dominated sorting genetic algorithm (NSGA-II) suggested that the total annual profit (TAP) would increase by $1.04 million/y while the effective process exergy loss (ΔExl,eff) would be reduced by 17.4%. Instead of serving as the fuel of SMR furnace, the H2 in tail gas was separated by a pressure-swing adsorption unit. After removing the concentrated CO2, the H2 and CH4 were introduced to a coal gasification plant (CG) to promote the syngas production. Further analysis confirmed that higher H2 formation rate of SMRT-CG process was realized compared to the original CG process due to the chemical looping with the tail gas.