Production of Negative-Emissions Steel Using a Reducing Gas Derived from DFB Gasification

Sébastien Pissot,Henrik Thunman,Martin Seemann,Peter Samuelsson

doi:10.3390/en14164835

Sébastien Pissot, Henrik Thunman + Show 2 more

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https://doi.org/10.3390/en14164835

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Abstract

A dual fluidized bed (DFB) gasification process is proposed to produce sustainable reducing gas for the direct reduction (DR) of iron ore. This novel steelmaking route is compared with the established process for DR, which is based on natural gas, and with the emerging DR technology using electrolysis-generated hydrogen as the reducing gas. The DFB-DR route is found to produce reducing gas that meets the requirement of the DR reactor, based on existing MIDREX plants, and which is produced with an energetic efficiency comparable with the natural gas route. The DFB-DR path is the only route considered that allows negative CO2 emissions, enabling a 145% decrease in emissions relative to the traditional blast furnace–basic oxygen furnace (BF–BOF) route. A reducing gas cost between 45–60 EUR/MWh is obtained, which makes it competitive with the hydrogen route, but not the natural gas route. The cost estimation for liquid steel production shows that, in Sweden, the DFB-DR route cannot compete with the natural gas and BF–BOF routes without a cost associated with carbon emissions and a revenue attributed to negative emissions. When the cost and revenue are set as equal, the DFB-DR route becomes the most competitive for a carbon price >60 EUR/tCO2.

Highlights

The iron and steel industry accounts for 4–7% of global CO2 emissions, making it one of the largest industrial emitters [1]
The results presented in this work reveal that the dual fluidized bed (DFB) gasification loop and gashandling section proposed for the DFB-direct reduction (DR) route can provide a reducing gas of quality similar to that of a natural-gas-based MIDREX plant, and whose reduction potential is, sufficient to achieve a high degree of metallization in the DR reactor
The DFB-DR process is found to be capable of producing a reducing gas that meets the requirement of the MIDREX process, which is the most commonly used DR reactor type

Summary

Introduction

The iron and steel industry accounts for 4–7% of global CO2 emissions, making it one of the largest industrial emitters [1]. The emissions intensity of the steelmaking industry is due to the use of fossil fuels, mainly coal and coke, to provide the energy required by the process as well as a reducing agent. Since the 1970s, direct reduction (DR) processes, which rely on natural gas rather than coal or coke, have emerged and gained traction. In DR processes, iron ore in the form of lumps, pellets, or fine powder is reduced in the solid state to direct reduced iron (DRI), which is thereafter converted to steel in an electric arc furnace (EAF). Hydrogen, produced from water electrolysis using fossil-free electricity, is an alternative to natural gas that has been proposed for the DRI-EAF route, as it can reduce iron ore to metal iron. The first pilot plant to test the production of DRI using hydrogen was started in 2020

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