Co-injection of Noncoking Coal and Natural Gas in Blast Furnace.

The most radical method for saving coke in ironmaking is to inject gaseous, liquid and solid substitutes into the blast furnace (BF) hearth by means of tuyeres. Use of one or another type of auxiliary fuel depends on the ratio of their prices, their deposits and the peculiarity of the technology. This paper presents the basic theoretical proposals of a technology for the simultaneous injection by tuyeres of natural gas (NG) and pulverized coal (PC) with any ratio up to complete exception of one of them. A laboratory study has been carried out of the thermal decomposition and gasification of different types of coals. Determination has been made of the softening temperature and melting temperature of the ash of these coals. These temperatures play an important role in optimizing the tuyere assembly design, raceway processes and slag regimes. The factors which determine the oxidizing potential of the raceway have been established. A study has been made of the comparative estimation of NG and PC and the compensation rates for BF operational conditions with simultaneous injection ranges of 0-100 m3/tHM NG and 0-200 kg/tHM PC, at a flame temperature of 1950-2150ºC and maintaining other blast and burden parameters constant. The rates automatically compensate the changes in temperature and the thermal and oxidizing potential in the raceway. This technology and tuyere assembly design are successfully used at two BFs.