Methanol synthesis through CO2 capture and hydrogenation: Thermal integration, energy performance and techno-economic assessment

Abstract

This work assesses the opportunity of using “green” methanol (MeOH) produced from renewable electricity as a vector for the decarbonization of chemical process industry. We developed a comprehensive process model to simulate all the relevant sections for the conversion of 1.25 t/h of captured CO2 from a coal-fired power plant to methanol, using “green” hydrogen via water electrolysis. We applied the pinch analysis methodology for an improved thermal management of the integrated carbon capture, electrolysis and methanol synthesis plant. A network of recovery heat exchangers was designed with the pinch analysis methodology, allowing a thermal energy saving of 4.59 MW, with a net reduction of heating and cooling demands by 81 % and 47 %, respectively, and an improvement of the global efficiency of the plant from 26.74 % to 37.22. We followed a bottom-up approach for the techno-economic assessment, defining a confidence range for the main indicators of system economic viability. We assessed their sensitivity to the cost of electricity from seven renewable energy sources and to the option of selling oxygen produced by water electrolysis, in three different cost scenarios (1-optimistic, 2-realistic, 3-pessimistic). The estimated values of the cost of methanol (COM) span from a maximum range of 2624–2706 €/t (in the case of concentrated solar power) to a minimum of 565–647 €/t (hydropower with highest valorization of electrolytic oxygen), hence resulting in line with the future trends of methanol market price (400–800 €/t) in five of the considered configurations. We have finally estimated the levelized cost of methanol (LCOM) ensuring an internal rate of return ranging from 0 to 10 % for each of the techno-economic scenarios identified. Assuming 10 % as the target, LCOM in case of hydropower as renewable energy source spans from 874 to 1356 €/t, hence close to the future market price of MeOH with margin of improvement (655–1135 €/t) in case of lower costs of electric energy.