Tech Update: Hydrogen-based DRI first step to decarbonising China's steel industry

*Constraints on hydrogen injection in traditional BFs
*Steep energy storage and transportation costs a deterrent
*Low market demand for H2-based DRI
*2050 timeline for large-scale replacement of grey H2

In 2019, China's power, steel, cement and coal chemical industries emitted about 7.76 billion tonnes (bnt) of carbon dioxide, accounting for 72% of the country's total emissions. As carbon peaking and carbon neutrality have become the main themes of global industrial development, the steel industry, which ranks second in carbon emissions, needs to undergo profound changes.

Due to its huge emissions reduction potential, many steel companies are deploying hydrogen metallurgy, green hydrogen preparation and hydrogen supply projects. The industry is making a transition from carbon metallurgy to hydrogen metallurgy.

BF versus shaft furnace

Hydrogen metallurgy uses hydrogen instead of carbon as the reducing agent and energy source to make iron, and the reduction product is water, which can achieve zero carbon emissions. The mainstream hydrogen metallurgy technology routes today are blast furnace (BF) hydrogen-rich smelting and gas-based direct reduction shaft furnace iron-making.

In BF hydrogen reduction, hydrogen-rich gas such as natural gas and coke oven gas are injected into the furnace. BF hydrogen-rich reduction can reduce emissions to an extent by speeding up the reduction of the charge.

However, because the process is based on traditional BFs, the skeleton effect of coke cannot be completely replaced and there is a limit to the amount of hydrogen injection. Emissions reduction in BF through the use of hydrogen can reach 10%-20%.

Gas-based direct reduction in a shaft furnace uses a mixture of hydrogen and carbon monoxide as the reducing agent. The iron ore is converted into DRI, which is then put into an EAF for further smelting.

So, compared with the hydrogen-rich reduction in BF, emissions per tonne can be reduced by more than 50%. This method is more suitable for hydrogen metallurgy.

However, gas-based shaft furnaces have many problems such as a strong endothermic effect, increased H2 gas flow into the furnace, increased production costs, decreased Hz reduction rate, high product activity and difficult passivation transportation.

At present, the leading instances of hydrogen metallurgy technology are the Swedish iron anhydride HYBRIT project, the Salzgitter SALCOS project, the voestalpine H2FUTURE project, and ThyssenKrupp's Carbon2Chem project.

Steel-chemical-hydrogen coupling

A few steel enterprises in China have released hydrogen metallurgy plans and built demonstration projects which are still in the stage of industrial testing.

Considering factors such as gas source, preparation, storage, transportation and cost, most of the hydrogen used is still grey hydrogen. There is a long way to go before green hydrogen metallurgy can be implemented on a broad scale.

Hydrogen metallurgy helps to promote the utilisation of carbon resources and the development of green short-process steelmaking methods. It also enables non-fossil energy smelting and develops steel-chemical-hydrogen energy coupling for carbon reduction.

In addition, hydrogen energy has also achieved good results in energy conservation and environmental protection in the logistics and transportation domain of China's iron and steel industry.

Green hydrogen economy

The global steel industry has improved energy efficiency and consumption has been reduced by 50% over the past 30 years. At present, the energy consumption of the global steel industry accounts for about 8% of the world's total, while carbon emissions account for 7% of the world's total.

The research on global hydrogen metallurgy is mainly divided into three stages: a) establishing a pilot demonstration project to verify the feasibility of large-scale hydrogen metallurgy before 2025; b) using hydrogen in by-products such as coke oven gas for metallurgical purposes by 2030; and c) substituting green hydrogen for grey hydrogen and the large-scale industrial application of hydrogen metallurgy by 2050.

While hydrogen metallurgy is conducive to energy conservation and emissions reduction, the iron and steel industry provides more landing applications for hydrogen energy and enriches the downstream industrial chain of hydrogen energy.

However, the green hydrogen economy still needs to be improved. The challenges are lack of experience in technical application, high hydrogen energy storage and transportation costs and insufficient downstream market demand for hydrogen-based DRI products.

The utilisation of hydrogen energy should be promoted for the whole industrial chain of hydrogen production, storage, transportation and use. At this stage, the cost of hydrogen smelting is much higher than traditional production processes. The role of market-oriented mechanisms in technological innovation and other fields should be fully utilised.