Replacing nature gas (NG) by recovered hydrogen-rich tail gas to fuel a full-scale furnace has been proved to improve furnace efficiency and reduce NOx formation. Adjusting residual O2 concentration in flue gases, air preheat temperature and furnace damper angle will further improve the efficiency of the furnace burning the recovered hydrogen-rich tail gas. Prolonging the residence time of the hot gas flow increases the heat release time and reduces the time for the fuel to reach burning temperature so that the furnace efficiency can be improved. On-site test results using a full-scale furnace show that reducing the residual O2 concentration in flue gases from 4.0 to 3.0 vol.% raises the furnace efficiency by 0.6%. Raising the pre-heated incoming air temperature from 200 °C to 240 °C and reducing furnace damper opening angle from 45° to 39° save 2.4 × 106 and 1.9 × 106 m3 of natural gas, respectively. Integrating the adjustment of flue gas residual O2 concentration, temperature of incoming air temperature, and furnace damper opening angle will assist industries in achieving higher overall furnace efficiency and reducing carbon dioxide emission.
