Design of a New Sustainable Methanol Plant Coupled to an Ethanol Distillery

Abstract

Abstract Contemplating the situation of biofuels globally, the objective of this work was to investigate the methanol synthesis using the carbon dioxide captured by fermentation process in bioethanol production distilleries, carrying out an integrated analysis of this system. Up to now, studies have been limited to performing only energy evaluation of the methanol production hydrogenating CO2 from fossil sources. Systems assessed in this perspective usually are not economically viable due to the cost associated to obtain hydrogen. Thus, in this work we designed a new sustainable methanol production process from a renewable source. Aiming to promote the advancement and applicability of carbon capture processes, an industrial methanol plant is modeled in Aspen Plus®. The hydrogen required is produced electrolyzing treated water of the distilleries, producing oxygen as a byproduct. Design parameters are manipulated applying factorial design and sensitivity analysis techniques. Once listed the parameters (i.e., amount of processed sugarcane and products prices) it was possible to treat each of them as a factor with different levels in the factorial design. The response surfaces are obtained according to the amount of bagasse used to cogenerate energy, which has a direct relation with the hydrogen production, attempting to maximize the profits for a plant operating 8600 h/y, reducing the total energy consumption and operating costs. The results show that the problem of high-energy consumption for the hydrogen production via electrolysis can be bypassed using co-generated energy, being possible and viable to synthesize this process in distilleries able to emit more than 350,000 ton.year- 1 of CO2 with enough cogeneration systems. The profits obtained by this process are derived from the methanol and oxygen produced being significantly superior by a factor of 4.5 compared to sale of electricity and 8.8 for sales of hydrogen and oxygen. The designed plant led us to conclude that this process can be implemented being an innovative option for carbon mitigation contributing to the sustainable production of methanol.