Thermodynamic analysis of tri-reforming of oxy-fuel combustion exhaust gas

A thermodynamic equilibrium analysis of the tri-reforming of oxy-combustion exhaust gases based on the minimisation of the Gibbs energy, was performed. To capture the effect of air leakage into the oxy-combustion boiler, two cases were investigated, representing 10 % and 1% combustion air leakage. The effects of temperature, pressure, and the ratio of methane to carbon dioxide (CH4/CO2) on the tri-reforming of the exhaust gases was studied. The domain of the practical operating regime for the tri-reforming of exhaust gases which is circumscribed by the maximum operating temperature, minimum CO2 conversion and zero-coke equilibrium was identified. In addition, three reactions (steam reforming, dry reforming and reverse water gas shift) were identified to be dominating in the temperature domain above the zero-coke equilibrium temperature. Within the boundaries of the practical operating regime, the tri-reforming of coal oxy-combustion exhaust gas results in more than three times the net conversion of CO2/kg CH4, when compared to the tri-reforming of conventional coal combustion exhaust gas.