Theoretical Approach to Change Blast Furnace Regime With Natural Gas Injection

The operation of blast furnace using natural gas and oxygen enriched blast (composite blast technology) is considered in many countries to be standard operation for a modern blast furnace particularly in certain countries with cheap and stable supply of natural gas. The theoretical flame temperature (TFT) of combustion and the degree of direct reduction of iron oxides (r(d)) are considered as the main controlling parameters of composite blast technology. The calculated values of these parameters are mainly dependent on the amount of air blast consumption. This amount of air blast is measured before entering into blast stoves. Actually, some of air blast is lost through valves of air stoves. Consequently, the real volume of air blast in the furnace is less than the recorded value by amounts of 5% - 15% which is not considered in the estimation of r(d) and TFT. The purpose is to analyze the different methods for estimation of air blast inside the blast furnaces and develop a theoretical model to calculate air blast consumption with high accuracy. Based on the calculation of air blast consumption, a complete roadmap is demonstrated to change the operation regime parameters of blast furnaces working on composite blast technology.