Perspectives on the reducing CO2 emissions of gas-based DRI in steelmaking

Abstract

The economics of the gas-based DRI unit depends on various factors, viz., quality and cost of the raw materials, reducing agents, operational efficiency and CO2 emission. Natural gas and synthetic gas (produced from coal gasification) are used as reductants in gas-based direct reduction processes. In the present study, the authors have developed a methodology for utilizing surplus or waste coke oven gas in place of syngas and thereby reducing the consumption of coal in the gasifier to produce a little bit greener steel. In this process, the syngas is enriched by mixing of adequate quantity of clean coke oven gas before entering the reduction furnace. Consequently, syngas consumption decreases and thereby reduces the coal requirement in the gasifier to produce the syngas, which helps decrease the CO2 emissions for eco-friendly steelmaking for a sustainable future. Results confirmed that coke oven gas (COG) is a good substitute for syngas. It has successfully replaced the syngas 1.18 times, i.e., 56,000 Nm3/h COG is replacing 66,000 Nm3/h syngas without affecting the DRI productivity. Subsequently, 1.8 times costlier syngas requirement reduces significantly in the DRI unit. This reduction of syngas reduces coal consumption, which directly decreases the CO2 emission in DRI production. Hence, the invented methodology in the existing syngas DRI plant reduces the DRI production cost by 860 INR/t, thereby reducing CO2 emissions by ∼300 kg/t. The developed technology was successfully implemented in the 1.8 MTPA gas-based DRI unit at Jindal Steel & Power Limited.