(45c) Alternative Pathways for Decarbonizing Methanol Production Plants through Advanced Technologies

The growing need for a sustainable and low-carbon energy source globally has increased the demand for alternative fuels, such as methanol, which has a lower carbon footprint compared to conventional fossil fuels. However, the conventional production and combustion of methanol still contribute substantially to CO₂ emissions, with a carbon intensity of approximately 110 g CO₂ eq/MJ using natural gas as a feedstock, which is currently the most used feedstock and process fuel for methanol production [1]. Some industries optimize the process by using CO₂ in the feed, which helps reduce the carbon footprint by about 10 g/MJ and increases output by 10%[1]. This work explores pathways to decarbonize the convectional methanol plants, with a particular focus on assessing the viability and impact of various advanced technologies. Specifically, it examines three scenarios: (1) using CARGEN® (Carbon Generator) technology, (2) combining methane decomposition with the water-gas shift reaction (WGSR), and (3) integrating water electrolysis with WGSR. The primary goal is to assess and compare these scenarios based on their economic viability (CAPEX and OPEX) and carbon intensity. The methodology involves building and simulating a base case of a conventional methanol plant in ASPEN^® Plus based on established literature, where a pre-treated shale gas undergoes partial oxidation reforming to produce syngas, followed by a WGSR to achieve the desired H₂/CO ratio of 2:1 for methanol synthesis, after which the conditioned syngas proceeds to the methanol synthesis stage. Finally, the product stream is processed through a flash column to get pure methanol. Process validation was achieved by comparing the simulation results with literature data. The CO₂ equivalent for the base case was calculated as 0.4219 kg CO₂/kg MeOH using electricity as the energy source. This closely validates with the GREET model’s reported footprint of 0.4145 kg CO₂/kg MeOH for natural gas-based methanol production (1.8% variance). This work aims to study the environmental and economic impact of each decarbonization scenario, with a focus on CARGEN’s potential to decarbonize the reformer step in the methanol case, which is typically the most energy-intensive part of the process. For all cases, the methanol production rate is fixed to be 5000 tons/day based on the literature. For the CARGEN® case, the direct CO₂ emissions are expected to be lower than 0.2422 kg CO₂/kg MeOH (direct CO₂ emission of the base case), as the CO₂ recycle stream is being utilized in the CARGEN® reactor. The indirect CO₂ calculations are still under assessment as well, but the results are expected to be higher in the case of CARGEN® due to processing volume, compression duties, and heating requirements. The results and outcomes will be further discussed and covered in the presentation.

References:

[1] Methanol Institute, “carbon footprint of methanol.” [Online]. Available: www.methanol.org