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Carbon dioxide management by chemical conversion to methanol: HYDROGENATION and BI-REFORMING

Wiesberg, Igor L., de Medeiros, José Luiz, Alves, Rita M.B., Coutinho, Paulo L.A., Araújo, Ofélia Q.F.
Energy conversion and management 2016 v.125 pp. 320-335
acidification, bioethanol, business enterprises, capital, carbon dioxide, clean energy, economic feasibility, emissions, energy, energy industry, environmental assessment, environmental performance, feedstocks, fossils, global warming, hydrogen, hydrogenation, methanol, natural gas, prices, profitability, raw materials, synthesis gas, uncertainty, water power, United States
Chemical conversion of carbon dioxide to methanol has the potential to address two relevant sustainability issues: economically feasible replacement of fossil raw materials and avoidance of greenhouse gas emissions. However, chemical stability of carbon dioxide is a challenging impediment to conversion requiring severe reaction conditions at the expense of increased energy input, therefore adding capital, operation and environmental costs, which could result in partial or total override of its potential sustainability as feedstock to the chemical and energy industries. This work investigates two innovative chemical destinations of carbon dioxide to methanol, namely a direct conversion through carbon dioxide hydrogenation (HYDROGENATION), and an indirect via carbon dioxide conversion to syngas through bi-reforming (BI-REFORMING). Process simulation is used to obtain mass and energy balances needed to support assessment of economic and environmental performance. A business scenario is considered where an industrial source of nearly pure carbon dioxide exists and an investment decision for utilization of carbon dioxide is faced. Due to uncertainties in prices of the raw materials, hydrogen (HYDROGENATION) and natural gas (BI-REFORMING), the decision procedure includes the definition of price thresholds to reach profitability. Sensitivity analyses are performed varying costs with greater uncertainty, i.e., carbon dioxide and methanol, and recalculating maximum allowable prices of raw materials. The analyses show that in a Brazilian scenario, BI-REFORMING is unlikely to be feasible, while HYDROGENATION would be viable, and with superior environmental performance, if the price of hydrogen remains inferior to 1000US$/t. A scenario of cheap natural gas at 2.74US$/MMBtu, as in the United States, would favor BI-REFORMING, which yields returns that are superior to those of HYDROGENATION even with hydrogen prices as low as 800US$/t. The integrated scenario of HYDROGENATION has an advantage of about 50US$/t in the methanol price in comparison to its non-integrated alternative. The environmental analysis revealed that both routes contribute to reduce global warming potential, and the reduction is intensified with a clean energy source (hydropower), with additional environmental benefit of decreasing acidification potential. For fossil energy supply, HYDROGENATION succeeds to reduce 87% of the emissions from the carbon dioxide source (bioethanol plant). Moving to a clean energy scenario increases the efficiency to 98%. BI-REFORMING is unable to reduce emissions (rather increasing it by 105%) in the fossil based energy scenario, however, for clean energy supply, it emits only 46% of the input of carbon dioxide from the bioethanol plant.