Exergoeconomic assessment and optimization of a syngas production system with a desired H2/CO ratio based on methane tri-reforming process

Based on methane tri-reforming process, a novel syngas producing system is proposed. The proposed system is analyzed in details from the viewpoints of thermodynamics and economics. In order to calculate the reactor volume required for its cost evaluation, a one dimensional homogenous model, based on the chemical kinetics of tri-reforming reactions is conducted for a fixed bed reactor. Influence of some design parameters including the reactor inlet temperature, system pressure, feed composition and reactor length on the reforming process as well as on the system performance is examined. Then, an optimization process is performed to maximize the overall energy efficiency. The results of parametric study demonstrate that the main indicators of system including H-2 yield, H-2/CO ratio, CH4 and CO2 conversions, energy efficiency and unit cost of the produced syngas are enhanced at thermodynamic conditions of high temperatures and low pressures. It is observed that, when the H2O concentration in the feed composition increases or the CO2 concentration decreases, the unit cost of produced syngas is reduced. In addition, the optimization process yields a maximum overall energy efficiency of 92.46 %. At this optimum design point, the unit cost of produced syngas is calculated as 4.48 $/GJ. Moreover, it is revealed that close to the reactor entrance, all oxygen is consumed by the methane combustion and the mixture temperature increases rapidly to a maximum value.