The use of combined-blast is the main way to improve the energy efficiency of blast furnaces

Abstract

The world production of hot metal and pig iron in 2012 reached 1.3 billion tons. More than 500 million tons of metallurgical coke produced from 650 million tons of expensive coking coals was consumed in blast furnaces to achieve this production goal. Metallurgical coke is a major contributor to the production costs of hot metal and pig iron, typically making up to 48-52% of the hot metal operating cost. Because of this, the reduction in metallurgical coke consumption was always a major goal for blast furnace operators. Supplemental fuels, especially in the form of a combined blast, are typically used to reduce coke consumption in a blast furnace. The major types of combined blast and supplemental fuels are as follows: oxygen enrichment, natural gas, oil and pulverized coal injection. The replacement coefficients of coke by these supplement fuels depend on the fuel quality, the arrangement of the injection process and adjustments in the blast furnace operating practice to optimize heat and mass transfer processes, metallic yield, gas dynamics and material movement. The fundamentals of the blast furnace process to achieve a highly efficient operation of the blast furnace with combined blast are discussed in this paper. The methodology of this research and development work is based on the theory of heat transfer in a blast furnace combined with local and overall heat and mass balances, the analysis of temperature distribution and material and gas movement. As a result, the maximum achievable replacement coefficients and reduction in the operating cost of hot metal were estimated alongside the required adjustments in blast furnace operation. © 2014 WIT Press.