Comparative Study on Coke Oven Gas and Refined Hydrogen-Rich Gas Injection in Blast Furnace: Effects on Tuyere and Raceway Behavior

Hydrogen-rich gas injection is a promising technology to reduce the carbon emission from blast furnace ironmaking process. To compare the behavior of coke oven gas (COG) and refined hydrogen-rich gas (RHG) in tuyere and raceway, numerical study is performed considering the blowpipe, tuyere, raceway, and porous coke bed. Results show that injection of hydrogen-rich gas leads to a local high-temperature zone near gas lance outlet and a faster consumption of oxygen. These two aspects have opposite effects on coal combustion and together affect the coal burnout rate increasing first and then decreasing with the increase in gas injection rate. Maximum burnout rates by COG and RHG injection are reached at 20 and 40 Nm³/t, respectively. To keep the same blast flow rate, blast pressure should increase 33.7 and 28.8 kPa, respectively, for 80 Nm³/t COG and RHG injection, compared to the no gas injection condition. More methane content in COG results in more gaseous combustion products, delayed local temperature increase, lower raceway temperature, higher pressure drop, and lower tuyere coke consumption. Replacement rate of tuyere coke consumption by COG injection is fitted as 0.08 kg/Nm³, while RHG injection has little influence. H₂ volume fraction in furnace increases with the increase in gas injection rate, which would promote the indirect reduction reactions and hence reducing the coke consumption further. COG presents larger potential than RHG to decrease coke consumption.