Combustibility behavior of PCI coals, green petroleum coke and charcoal fines used as fuel for injection into blast furnace tuyeres.

Abstract

Pulverized coal injection (PCI) into blast furnace tuyeres is widely used by integrated steel mills worldwide to reduce the consumption of coke and costs. High injection rates are desirable. The big challenge is to achieve them with cheaper and lower quality raw materials, without losing the quality of the hot metal and the productivity of the blast furnace. An increase in the injection rate leads to improved fuel selection. Thus, it is important to have knowledge of the injected fuel quality variables that affect the burning efficiency and the replacement rate of the coke into the furnace, as well as the quality of the hot metal and the stability of the furnace. In this context, the present study is based on the chemical characterization and combustibility behavior of four fuels: Australian coal (CMA), North-American coal (CMN), charcoal fines (MCV) and green petroleum coke (CVP) and fuel blends. Results of chemical analysis show that the CMA, CMN, MVC and CVP are within the ranges of acceptable values in the PCI process for the ash and sulfur contents. The order of combustibility by thermogravimetric analysis was MCV>CMN>CMA>CVP. However, the combustion rate obtained by the simulator test, performed under extreme conditions of short residence time and high temperature, presented a different order of combustion rate of MCV>CVP>CMA>CMN, which may be related to the mineral on char. The blend that presented the best burning efficiency was obtained for the composition containing 20%MCV+80%CVP, followed by blends containing 80 and 90% of CMA, respectively.