Optimizing methanol synthesis combining steelworks off-gases and renewable hydrogen

Renewable hydrogen improves the carbon balance of the methanol synthesis process but raises the production costs rendering a suitable hydrogen utilization strategy necessary. This work proposes different operating maps and reactor configurations that lead to improved hydrogen utilization and thus lower production costs. A mixture of steelworks off-gases is investigated as feedstock for the synthesis. At first, the conventional single-reactor loop operation is investigated, whereas in the second part, multi-reactor configurations are proposed to improve the process performance. Crucial operating variables are optimized to achieve optimum hydrogen utilization con-ditions for the investigated reactor setups. Results showed that recycling improved the performance in the single -reactor but no substantial improvements are observed for the multi-reactor setups. Overall, the four-reactor concept improves significantly the process efficiency that consequently could reduce the associated produc-tion costs: 13% lower hydrogen, 30% lower feedstock, 27% lower compression requirements and higher CO2 conversion (63%) per produced methanol unit.