High-efficiency utilization of CO₂ in the methanol production by a novel parallel-series system combining steam and dry methane reforming

Global warming caused by the accumulation of atmospheric CO₂ has received widespread attention in recent years. The direct CO₂ integration process in NG-based methanol (MeOH) synthesis plant is one of the predominant CO₂ utilization technologies. However, a large amount of water produced in the MeOH reactor increasing the difficulty in the subsequent purification system and the high direct CO₂ emissions are caused by the low CO₂ conversion rate. In view of such issues, we propose an innovative MeOH production approach based on a parallel-series system combining steam methane reforming (SMR) and dry methane reforming (DMR) to achieve a high-efficiency utilization of CO₂. In this approach, the CO₂ from SMR and that from additional feeding are converted into CO with a proper amount in the DMR reformer, and thus the content of CO₂ in the make-up gas becomes more appropriate than that of existing processes, and the conversion rate of CO₂ to MeOH could be obviously increased, what is more, the corresponding direct emissions of CO₂ could be significantly reduced. On the other hand, the carbon efficiency is introduced to evaluate the conversion efficiency of all raw material (i.e., CH₄ and CO₂) containing the carbon atoms. The comparative evaluations are carried out using Aspen Plus V8.4^® and the proposed improved process is demonstrated to be more efficient than existing ones from views of technological, economic, and environmental metrics.