Integrating a Top-Gas Recycling and CO2 Electrolysis Process for H2-Rich Gas Injection and Reduce CO2 Emissions from an Ironmaking Blast Furnace.

Yichao Hu,Yinxuan Qiu,Liangyuan Hao,Jian Chen,Victor Rudolph,Thomas Edward Rufford,Geoff Wang

doi:10.3390/ma15062008

Abstract

Introducing CO2 electrochemical conversion technology to the iron-making blast furnace not only reduces CO2 emissions, but also produces H2 as a byproduct that can be used as an auxiliary reductant to further decrease carbon consumption and emissions. With adequate H2 supply to the blast furnace, the injection of H2 is limited because of the disadvantageous thermodynamic characteristics of the H2 reduction reaction in the blast furnace. This paper presents thermodynamic analysis of H2 behaviour at different stages with the thermal requirement consideration of an iron-making blast furnace. The effect of injecting CO2 lean top gas and CO2 conversion products H2–CO gas through the raceway and/or shaft tuyeres are investigated under different operating conditions. H2 utilisation efficiency and corresponding injection volume are studied by considering different reduction stages. The relationship between H2 injection and coke rate is established. Injecting 7.9–10.9 m3/tHM of H2 saved 1 kg/tHM coke rate, depending on injection position. Compared with the traditional blast furnace, injecting 80 m3/tHM of H2 with a medium oxygen enrichment rate (9%) and integrating CO2 capture and conversion reduces CO2 emissions from 534 to 278 m3/tHM. However, increasing the hydrogen injection amount causes this iron-making process to consume more energy than a traditional blast furnace does.

Highlights

Traditional blast furnace (BF) iron making relies on carbon and contributes to over 70%
Coke is converted into a high-temperature CO gas and performs an exothermic reaction with iron ores, resulting in a large amount of CO and CO2 leaving the furnace with top gas
A static energy balance model of the BF was adopted with this thermodynamic model

Summary

Introduction

Traditional blast furnace (BF) iron making relies on carbon and contributes to over 70%. Of CO2 emissions in the iron and steel industry [1]. Coke is converted into a high-temperature CO gas and performs an exothermic reaction with iron ores, resulting in a large amount of CO and CO2 leaving the furnace with top gas. Every tonne of hot metal (tHM) produced from a traditional BF requires about 500 kg/tHM carbon and generates around 1.2 tonnes of CO2 emissions [2,3]. There were various attempts for a clean iron-making process to reduce CO2 emissions [4–7]. Compared to CO reduction that generates CO2 , reducing iron ores by hydrogen only forms water vapor. Hydrogen enables a higher gas flow rate, and a faster reduction in iron ores and productivity than only

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