Methanol production based on methane tri-reforming: Process modeling and optimization

•An optimal and green process is designed for CO2 conversion to methanol.•The proposed process is modelled based on the mass and energy balance equations.•An optimization problem is formulated to maximize methanol production.•Methane conversion and methanol production rate in the optimized process are 99.91 % and 265.6 ton day−1.•The CO2 conversion in the proposed process is 19.78 % at optimal condition. In this research an process flowsheet is introduced for carbon dioxide conversion to methanol and a mathematical framework is prepared to analyze the operability of proposed plant. The main steps in the designed process are syngas production through methane tri-reframing, syngas purification, methanol synthesis in the isothermal reactor and syngas recycling. To develop a detail framework, the methane and syngas conversion sections are heterogeneously simulated based on the energy and mass conservation laws, and integrated with the considered equilibrium-based model for separation sections. To prove the correctness of developed model, the simulations results are compared with the experimental data at the same condition. Then, an optimization problem is formulated to determine the optimal operating condition of designed process considering methanol production capacity as objective. Since feeding policy is a key strategy to shift tri-reforming reactions toward the desired condition, the applied single-bed tri-reformer in the designed process is substituted by a multi-bed reactor and methanol production capacity is calculated. It concludes that applying the multi-bed reformer changes the tri-reforming reactions toward the hydrogen synthesis side and increases the methanol production rate from 200 to 265 ton day−1.