Influence of the hydrogen-rich on the furnace thermal efficiency

Highlights: • Iν fixed velocity mixing fuel, the flame length is reduced when adding more hydrogen. • Orange-yellowish brightness decrease with increasing tail gas to hydrocarbon fuel. • Adding hydrogen to hydrocarbon fuel will improve the velocity and stability flame. - Abstract: In this research a full-scale furnace is used to recover the hydrogen-rich tail gas as fuel. Adding hydrogen gas to hydrocarbon fuel will reduce the ignition delay of methane, increase the flame velocity and speed up the relatively slow reaction rate of methane to improve the flame stability. The results show that the flame length and orange-yellowish brightness decrease as the amount of tail gas fuel added to the natural gas increases, because of the lower C/H ratio in the flame. Moreover, at a fixed flow rate of hydrocarbon fuel, the moving length of the burning flame is reduced as the amount of hydrogen increases, and thus the visible flame length becomes shorter. Additionally, burning the mixture of tail gas reduces the pressure and increases the gas rising velocity in the furnace radiation and convective zones compared to burning pure tail gas, and thus the gas temperatures in the convective zone and in the flue are raised. The furnace convective zone temperature and the flue gas temperature are 793.6 °C and 350.7 °C, respectively, for burning the mixture fuel (45 vol. % tail gas + 55 vol. % natural gas) vs. 648.5 °C and 346.3 °C for burning the pure tail gas.