CFD simulation and experimental investigation on co-combustion characteristics of pulverized coal and natural gas in blast furnace injection

Natural Gas Injection (NGI) technology in blast furnaces (BFs) is a promising strategy to reduce coal dependency and mitigate carbon emissions. This study systematically investigates the combustion behavior of pulverized coal (PC) and the thermal state of the tuyere-raceway zone under composite injection of NG and PC, using integrated experimental and computational fluid dynamics (CFD) simulations. The results revealed that NGI increases the gas-phase temperature within the tuyere by 15–20 % compared to PC-only injection, but excessive NGI reduces the raceway high-temperature zone by 8–12 % and lowers PC burnout rate by 5–7 %. NGI enhances hydrogen mole fraction in coal gas by 20–30 % while reducing CO mole fraction by 15–20 %, improving ore reducibility and energy efficiency. Experimental validation confirms that NGI volume inversely correlates with PC combustion efficiency, with a 6.8 % reduction in PC burnout rate observed when NGI increases from 0 to 80 m 3 /t. Unlike prior studies focused on single-fuel injection or qualitative trends, this work quantifies the trade-offs between NGI-induced thermal benefits and PC combustion deterioration. The results provide critical insights for optimizing BF tuyere injection strategies to balance decarbonization goals with combustion efficiency, addressing a key gap in existing literature. • Analysis of PC combustion and BF conditions with NG-PC co-injection via experiments and simulations. • Conversion of BF operating conditions into experimental parameters for co-injection investigation. • NG volume impacts PC combustion and raceway dynamics, highlighting emission reduction trade-offs. • Results guide optimization of BF fuel injection, supporting steel industry low-carbon transition.