Numerical Simulation of the Effect of CH4/CO Concentration on Combustion Characteristics of Low Calorific Value Syngas.

Abstract

The composition of low calorific value synthesis gas varies greatly depending on the raw material and processing technology, which makes the combustion extremely complicated. The three mechanisms of the GRI-Mech 3.0, Li-Model, and FFCM-Mech are used to numerically simulate CH4/CO/H2/N2 air premixed combustion by using ANSYS CHEMKIN-PRO. The numerical simulation is the calculation of laminar flame velocity and adiabatic flame temperature at an initial temperature of 298 K, an equivalence ratio of 0.6–1.4, and an initial pressure of 0.1–0.5 MPa, discussing through thermodynamics and chemical kinetics. The formation of NOX, H, and OH radicals by fuel composition was analyzed. The result shows that the concentrations of H, O, and OH radicals have a positive effect on laminar flame velocity. The combustion reaction of H2 is higher than that of CH4 and CO; with the increase of N2 content, the priority is higher. The thermal diffusivity of flame under different equivalence ratios is affected by inert gas, which affects adiabatic combustion temperature and laminar combustion velocity. In thermal kinetics and chemical kinetics, CH4 has more influence on combustion temperature than CO, while laminar flame velocity is relatively low. Under the change of initial pressure, the laminar combustion flux increases to the initial pressure and the laminar combustion velocity decreases to the increase in pressure. Reactions H + O2 = O + OH, HO2 + H = 2OH, and CH3 + HO2 = OH + CH3O are mainly due to change in the concentration of O, H, and OH radicals.