Thermodynamic assessment of tri-reforming of methane with optimization of operating conditions to achieve suitable syngas for methanol production
摘要
The present study consists of two parts. In the first part, a thermodynamic assessment of the reactions involved in the tri-reforming of methane (TRM) to syngas was conducted using a stoichiometric approach by simultaneously solving a system of nonlinear equilibrium equations. Using the results, the effects of operational variables, including temperature, pressure, and the molar ratios of H2O, CO2, and O2 to CH4, were investigated on reactant conversions, product yields, and the H2/CO ratio. The results revealed that while increasing temperature promotes CH4 and CO2 conversions, H2O conversion exhibits a non-monotonic trend due to the competition between reforming and the reverse water-gas shift (RWGS) reaction. Higher temperatures and lower pressures generally enhance the yields of H2 and CO, though the H2/CO ratio decreases as temperature rises. Furthermore, increasing the CO2 feed ratios reduces the H2/CO ratio, whereas increasing the H2O ratio effectively enriches the syngas with hydrogen. In the second part, a Genetic Algorithm (GA) was employed to identify optimal operating conditions for producing syngas with a target H₂/CO ratio of 2.0, suitable for methanol synthesis, subject to CH4 and CO2 conversion constraints exceeding 90%. The optimal conditions were identified as: Temperature = 989 °C, Pressure = 1.0 bar, and a feed ratio of CH₄:H₂O: CO₂:O₂ = 1:0.61:0.30:0.10. Under these optimized parameters, a CH4 conversion of 99.8% and a CO2 conversion of 90.0% were achieved, yielding a syngas ratio of 1.99. These results are fully consistent with industrial requirements for methanol synthesis and align with the parametric sensitivity trends established in the thermodynamic analysis.