Blast furnace operation with natural gas injection and minimum theoretical flame temperature

The operation of blast furnaces using natural gas and oxygen enriched blast ( composite blast technology) is being used in many iron and steel companies to reduce the consumption of coke per unit weight of hot metal. The addition of oxygen to the air blast and injection of natural gas through tuyeres have a different effect on the basic variables of the blast furnace processes such as the temperature in the hearth, the degree of direct reduction and the dynamic conditions of the gas in the furnace. The most important reason for saving coke in composite blast technology is the decrease in the share of direct reduction of iron oxide. The main controlling parameter in the operation of the blast furnace using natural gas injection is the theoretical flame temperature. The amount of natural gas in the blast can be optimised to attain the minimum value of the theoretical flame temperature. The present paper presents the theoretical bases of the composite blast technology using natural gas injection and develops an accurate method to calculate the theoretical flame temperature.