Effective utilization of using natural gas injection in the production of pig iron

Abstract

The technology of using natural gas injection and oxygen enrichment blast (composite blast technology) to produce hot metal is widely applied in the modern blast furnaces to save the consumption of coke per unit weigh of hot metal. Coke to be used in the blast furnaces at the Egyptian Iron and Steel Company (EISC) is imported whereas natural gas is locally produced. The approximate ratio of natural gas to coke price is 1:3, accordingly EISC implemented the composite blast technology as an effective route for pig iron cost reduction. Up to a certain limit, utilization of natural gas to replace coke in the blast furnace is beneficial for the pig iron cost. The effectiveness of blast furnace operation on composite blast technique depends on the proportioning of oxygen and natural gas consumption which determine the value of the theoretical flame temperature (an operational index for blast furnace). The present study introduces an analysis for the real data of blast furnaces Nos. 3 and 4 at EISC. The average values of operating data of these furnaces in 1980–1982 and 2000–2002 were selected to analyze the technology of natural gas injection without and with oxygen enrichment of air blast respectively. A model for the prediction of theoretical flame temperature of combustion was demonstrated to clarify the effective utilization of natural gas in the blast furnace at EISC and determine the optimum natural gas consumption figure. It was found that the amount of natural gas injection by tuyeres should be increased to the minimum value of theoretical flame temperature.