Modeling and Simulation of non-Catalytic Laminar Combustion of Methane to Synthesis Gas

The effect of operating conditions on the performance of non-catalytic laminar premixed combustion of methane to synthesis gas is investigated. To this end, the effect of feed methane to oxygen ratio on the minimum required preheat temperature, and the effects of feed methane to oxygen ratio, feed steam to methane ratio, and pressure on methane conversion and syngas selectivity are taken into account. Simultaneous interaction of mass and heat transfer phenomena and hydrodynamic with chemical kinetics are studied using a one-dimensional model. The well-known GRI 3.0 mechanism is applied to model the kinetics of methane oxidation reactions. The open-source numerical subroutine of TWOPNT is employed to solve the set of model equations. The model can well predict the relevant experimental data. The effect of pressure on reducing the required preheat temperature for a lean fuel is more than a rich one so that for feed methane to oxygen ratio of 0.25, increasing the pressure from 1 to 60 bar reduces the minimum required preheat temperature by 200 K and 800 K, respectively. The reaction mixture can ignite at room temperature of 298 K for feed methane to oxygen ratio of 0.5-0.7. Moreover, increasing the content of steam and methane in feed has similar effects on methane conversion whereas their effect on syngas selectivity is opposite. Increasing the feed steam to carbon ratio up to 4 reduces the syngas yield by 83-90 percent. Steam injection to feed is necessary for reducing the soot formation and increasing the hydrogen content. An increase in pressure continuously increases the methane conversion and reactor temperature for feed methane to oxygen ratio of 0.25 while for ratios of 2 and 2.5 there are optimum pressures of 30 and 35 bar in which these parameters reach a maximum value.