Coke Strength Reaction

Many coke plants and blast furnaces around the world use CSR as a specification just as important as cold strength, size, and chemistry. Researchers have studied reactivity and its influence on blast furnace performance and productivity. The use of both physical and mathematical models of the various blast furnace zones, the monitoring and sampling of heavily-instrumented blast furnaces, and the quenching and subsequent sampling of commercial furnaces have aided in determining the effect of changes in coke reactivity on furnace operating parameters such as fuel rate, furnace permeability, and hot metal production. It has been widely reported in the literature that increases in CSR have led to decreases in blast furnace fuel rates. The magnitude of fuel rate reductions varies for different blast furnaces and operating parameters. The exact effect of coke reactivity on blast furnace performance is not completely clear; however, most furnace operators agree that the coke should not readily react at lower temperatures in the upper zone of the furnace to avoid wasted carbon. Also, highly reactive coke may become substantially weakened so that it cannot properly support the burden during its descent through the blast furnace. By the time the coke works its way to the high temperature combustion zone, or raceway, the coke may become so weak that it causes major upsets to occur in raceway performance. Poor raceway behavior restricts both gas and liquid permeability in the blast furnace, reducing overall furnace efficiency.

As a result of major changes in blast furnace operating parameters and practices through the 1990's such, as increased usage of auxiliary fuels and improved operating efficiency, coke rates to the blast furnace have dropped well below 1000 pounds per ton of hot metal. Thus, the need for strong and consistent coke properties has become greater than ever. Ideally, cokes should be high in CSR and low in corresponding reactivity. The optimum CSR will depend on the particular blast furnace, its associated practices, and overall production goals.