Techno-economic and environmental impact analysis of tuyere injection of hot reducing gas from low-rank coal gasification in blast furnace

Abstract

Our goal is to find a strategy to reduce coke use during operation of a blast furnace (BF). This study focuses on the techno-economic and environmental impact analysis of tuyere injection of hot reducing gas (HRG) from low-rank coal (LRC) gasification in the BF. LRC gasification by entrained-flow gasifier is introduced to make gaseous fuel, and the cleaning process of the raw syngas is implemented using Aspen Plus V10. The effects of HRG injection are evaluated using a BF model derived from the Rist operating diagram. Integrated results from raw fuel to the BF were analyzed considering economic, energy, and environmental aspects. By injecting rich syngas (>95 vol %) into the BF at 1150 K, coke replacement ratio is estimated to be 0.354 kg/Nm3 without adverse impact on the BF. The most sensitive economic factor is coke price. The energy efficiency of raw syngas cleaning process, relative energy intensity of LRC, gas utilization ratio are 57.5%, 90.6%, and 50.0% respectively. Utilization of HRG can reduce CO2 emission by 21.88 ktCO2/yr compared to the reference BF operation.