Utilising CO2 from manganese plant flue gas for methanol production: System design and optimisation

A potential measure to mitigate climate change and high energy consumption is the conversion of the abundant carbon dioxide (CO2) in industrial flue gas into value-added products. Herein, combined with the 300,000 tonnes of electrolytic manganese metal technical renovation project of Tianyuan Manganese Industry in Ningxia, the methanol production performed using 10,000 tonnes of CO2 annually is simulated. The hydrogen produced by alkaline hydro-electrolysis through solar and wind power generation is mixed with the CO2 purified in the manganese dioxide roasting workshop of the self-made manganese plant and fed into the methanol reactor with a Cu/Zn/Al/Zr catalyst. The methanol thus obtained is sold after separation and purification. The water at the bottom of the rectifying column is mixed with fresh water and circulated in the water electrolytic unit for hydrogen production. The design of the supporting photovoltaic (PV) power generation systems is simulated using TRNSYS18 software. Results show that the optimal reaction temperature, pressure and space velocity for methanol preparation using this system are 501 K, 50 bar and 5.9 m3/kgcat h, respectively. Simulation results indicate that the proposed methanol production process boasts a higher energy efficiency and process yield than the conventional process. Consequently, potential annual profits would increase by USD6.71 x 107 along with reduced greenhouse gas emissions. This study thus provides a novel approach for cogeneration of green methanol while reducing industrial waste gas emission.