Energy Optimization Studies for Integrated Steel Plant Employing Diverse Steel-Making Route: Models and Evolutionary Algorithms-Based Approach

Abstract

ABSTRACT Presently, blast furnace-basic oxygen furnace (BF-BOF) route is conventionally used in integrated steel plants (ISPs). As availability and cost of coking coal are becoming serious issues, alternative routes of iron and steel production such as COREX, shaft-based process for direct reduction of iron and electric arc furnace in combination with BF-BOF route is becoming a matter of focus. The possibility of energy efficiency improvement using such a mixed route in ISPs is dependent on proper utilization of fuel gases generated in addition to the total input fuel bearing resources to the plant. A flow-sheet simulation approach has been developed using phenomenological and stoichiometric modeling of the important process steps. Optimization for lowering input fuel energy and maximizing available fuel gas energy has been developed based on evolutionary algorithms using simulated flow-sheet streams. The fuel gas used downstream needs to be tailored to higher calorific values (CVs) in the gas network for critical downstream applications. Two cases of high CV-mixed fuel gas have been considered comprising (a) principally mix of coke oven gas and COREX off-gas and (b) mix of blast furnace gas and coke oven gas in 2:1 volume ratio along with high CV gases such as COREX off-gas and BOF converter gas. Energy optimization possibilities exist which simultaneously minimize input fuel energy and maximize high CV fuel gas for downstream use. The flow-sheet solutions simultaneously lead to configuration predictions with fractional stream splits.