"Green steel" path exploration - hydrogen metallurgy

As a large carbon emitter, the steel industry accounts for about 15% of China's total carbon emissions. Under the background of the "double carbon" goal, how to embark on the road of "green steel" is an urgent problem for the entire industry.

Raw material or fuel substitution is one of the important measures to reduce CO2 emission. Hydrogen metallurgy technology uses hydrogen as a reducing agent instead of carbon reduction, which is one of the important ways to reduce CO2 emissions in long process steelmaking and ensure the green and sustainable development of steel industry.

In February 2022, the Ministry of Industry and Information Technology, the National Development and Reform Commission, and the Ministry of Ecology and Environment jointly issued the Guiding Opinions on Promoting the High-quality Development of the Steel Industry, clearly proposing to promote the research and development of advanced process technologies such as hydrogen metallurgy, low-carbon metallurgy, clean steel smelting, thin strip casting and rolling, and head less rolling.

What are the hydrogen metallurgy technology processes?

Hydrogen energy is an effective way to eliminate carbon emission in traditional steel and iron making process. Hydrogen energy can not only replace fossil fuel in blast furnace ironmaking, sintering, hot blast furnace, lime kiln, steel rolling furnace and other production processes, but also as a reducing agent to complete the reduction reaction in steelmaking process.

Typical hydrogen metallurgy processes mainly include hydrogen plasma direct steelmaking, hydrogen melting reduction and hydrogen direct reduction, among which the main ones are blast furnace hydrogen rich smelting and gas base direct reduction shaft furnace iron making.

Blast furnace hydrogen rich smelting is to inject hydrogen rich gas (coke oven gas, natural gas) or hydrogen into the blast furnace, is a low carbon iron making technology. The injection of H2 or hydrogen-rich gas in blast furnace can increase the production of pig iron, save coke and reduce carbon emission to a certain extent.

At present, the process has matured and has many advantages, such as improving the operation condition of blast furnace, increasing energy utilization efficiency, reducing the use of coal and coke, and reducing CO2 emissions. However, due to the limited amount of hydrogen injection, the carbon reduction range of hydrogen rich reduction in blast furnace is 10%-20%, and the effect is limited.

The gas base direct reduction shaft furnace uses H2 and CO mixed gas to convert iron ore into direct reduced iron and then put it into electric furnace for smelting. The process can control carbon emissions from the source, and the carbon reduction range can reach more than 50%, and the emission reduction potential is large.

What is the current situation of research and development and application of domestic hydrogen metallurgy industry?

In order to achieve the "double carbon" goal, China's iron and steel enterprises actively participate in the research and development of hydrogen metallurgy technology, and have successively built or will build related hydrogen metallurgy production lines. However, the hydrogen metallurgy process has not yet achieved large-scale development and application in China.

What are the factors that restrict the development of hydrogen metallurgy process?

The cost of hydrogen

Iron and steel industry production scale is huge, large-scale implementation of hydrogen metallurgy needs a large number of low cost, environmental friendly and environmental efficiency and energy conversion efficiency of high hydrogen sources. At present, hydrogen is a relatively expensive secondary energy, the price is high, so the future development of hydrogen metallurgy process largely depends on hydrogen large-scale, economic, green production and economic storage and transportation.

Technical barrier

There are still many key technologies to be solved in hydrogen metallurgy technology, such as the process of direct reduction of iron oxide by hydrogen is a strong endothermic reaction, and the problem of heat balance in the furnace in the reduction process needs to be solved.