Governing processes of gas and oil injection into the blast furnace

To enhance the blast furnace process, the practice of injecting reducing agents into the blast furnace is used. In a metallurgical plant of the voestalpine Stahl, so far the injection of oil is practiced. The availability of gases like coke oven gas (COG) makes it possible to substitute reducing agents like heavy oil. The injection of gas and oil, respectively, shows different reaction characteristics and therefore different reducing conditions are obtained. In this work, theoretical considerations are made about the different conversion characteristics of oil and gas. The calculations, done by using computational fluid dynamics (CFD), provide a detailed description of the oil and gas flow injected in the hot blast. For gas injection, the mixing of gas and blast and their conversion are considered in tuyere and raceway. For oil injection, additionally the evaporation of the oil droplets takes place. The injection of gas with one lance shows an inhomogeneous distribution in temperature and velocity due to the high injection velocity compared to oil injection. For the injection of oil, evaporation of the oil droplets takes place and the gas formed reacts with the hot blast. There, the distribution of temperature, velocity and concentrations is more homogeneous than for gas injection. A variation of the oil droplet size injected shows for larger droplets (400 mu m and more) an incomplete evaporation and distributions similar as for the gas injection.