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. (C) 2018 Elsevier Ltd. All rights reserved.