The main technical development direction of Chinas steel metallurgy field

Academician Wang Guodong: Main technical development direction in China's steel metallurgy field

  

As the most important raw material industry, the iron and steel industry has the most fundamental task of providing the society with a sufficient quantity and quality of high-performance steel products with the lowest environmental and ecological load, with the lowest environmental and ecological load, with the highest efficiency and labor productivity. Development, national security, and the needs of people's lives. To accomplish such a task, I believe that the steel industry should grasp the following main technical development directions in the field of iron and steel metallurgy:

1. Low carbon iron making technology

In the context of global efforts to reduce greenhouse gas emissions, the international steel industry is actively developing technologies to reduce CO2 emissions from ironmaking processes, one of which is along the blast furnace low-carbon ironmaking technology, focusing on the study of blast furnace carbon-iron composites. New charge materials such as charge, recycling of blast furnace top gas, hydrogen-containing substances (hydrogen-rich, natural gas, COG) injection, high oxygen enrichment (oxygen-rich rate ≥30% or total oxygen) injection, limited amount of coal injection. The injection of hydrogen-containing substances (rich hydrogen injection) has the effect of significantly reducing carbon emissions, and increasing the blowing content of hydrogen is a development trend of blast furnace technology, and particular attention should be paid. In addition, the high pellets are better than the furnace material structure optimization, the ratio of the size of the charge to the furnace and the distribution optimization optimization, and the high efficiency blast furnace smelting technology is also being implemented.

2. Low-carbon, emission-reducing non-blast furnace ironmaking technology

Another important research direction of ironmaking technology is non-blast furnace ironmaking technology. Compared with blast furnace ironmaking technology, non-blast furnace ironmaking technology is beneficial to get rid of the shortage of coking coal resources, change energy structure, save energy, greatly reduce SOx and NOx emissions in coking and sintering, and protect the environment. Rank important directions and means. Non-blast furnace ironmaking technology uses hydrogen reduction, which can significantly reduce CO2 emissions.

1) smelting reduction technology

The smelting reduction techniques for non-blast furnace ironmaking include Himmelt, Hisarna, COREX, FINEX, and flash iron making. The FINEX smelting reduction technology developed by Pohang Korea has been industrialized and started to be exported. At the same time, Posco combined FINEX with other technologies to form new non-blast furnace ironmaking technologies, such as POIST process, mixed hydrogen reduction process, and nuclear hydrogen reduction process. The American Iron and Steel Association is currently working on a non-blast furnace ironmaking project to reduce CO2 emissions from the steel industry, including hydrogen production by hydrogen flash smelting (using hydrogen as fuel), molten oxide electrolysis research, new suspension ironmaking technology, and carbon dioxide geological storage research. Wait. Baosteel of China has introduced COREX smelting reduction technology. In consideration of economic factors, it has moved to Xinjiang to continue its work. Academician Zhang Wenhai is working on the development of flash ironmaking technology and is building a pilot test device in Hebei.

Most of the above smelting reduction techniques have not been able to get rid of the basic conditions of using pulverized coal as a raw material, and therefore, the effect on carbon emissions is limited. We should develop a low-cost, high-efficiency, low-carbon smelting reduction ironmaking technology with Chinese characteristics, based on its advantages and problems, using hydrogen-based reducing agents.

2) Direct reduction technology

There are many ways to directly reduce, such as direct reduction of tunnel kiln, direct reduction of rotary kiln, direct reduction of shaft furnace. The fuel can be coal based or gas based. However, the most successful one is the direct reduction of gas-based shaft furnace. There is already a gas-based shaft furnace direct reduction device with an annual output of 2,5-3 million tons of natural gas in industrial operation. It is developing rapidly in areas with abundant natural gas and low prices, and is currently the main production method of DRI. In view of China's situation, the use of selected iron concentrates and non-coking coal gas, followed by continuous hot charging furnace smelting, may produce high quality pure steel at a lower cost than the blast furnace, which is competitive for some small steel mills. The mode of production is worthy of combining China's national conditions, especially for the research and application of China's unique resources such as high-chromium vanadium-titanium ore, boron-bearing ore, and out of China's own road.

Direct reduction of gas-based shaft furnace In addition to the use of coal-based gas as a reducing agent, natural gas, hydrogen, etc. can also be used as a reducing agent, and can be used in a certain proportion. In today's emphasis on reducing carbon emissions, increasing the proportion of hydrogen has become the development direction of direct reduction of gas-based shaft furnaces. Therefore, the transition from direct reduction of gas-based shaft furnace to hydrogen-based reducing agent to achieve significant reduction of carbon dioxide should be the main direction of efforts in the future.

3) Direct hydrogen reduction

VAI has developed a long-term plan for 20 years to promote the development of hydrogen reduction technology, and the CO2 emission reduction target is positioned at 50%. In the first phase, the traditional blast furnace-converter long-flow steel plant in Austria was used to directly reduce the iron hot briquetting block HBI using a gas-based shaft furnace, and at the same time, the natural gas-based shaft furnace of the DRI plant in Texas, USA was changed into a hydrogen shaft furnace ( It has already reduced emissions by 40% compared to the use of coal and coke. In the second stage, it takes another 10-15 years to increase the amount of hydrogen used in the blast furnace to achieve hydrogen as the main reducing agent, but not all of it replaces pulverized coal and coke. Reduce CO2 emissions from the source, rather than relying on capture and fixation technologies to reduce CO2 emissions. At present, hydrogen production piloting is underway, and the production process based on hydrogen reduction around 2030 will be put into practical use on a large scale. With the increasing pressure on CO2 emission reduction, hydrogen reduction technology will be more and more valued by the steel industry, ushered in the opportunity of vigorous development.

Research on hydrogen reduction technology, such as biomass reduction technology and nuclear hydrogen reduction process, should be the main development direction. Therefore, the source of low-cost hydrogen has become an important issue. In cooperation with the nuclear energy industry, research on nuclear hydrogen reduction processes should be an important direction.

4) Direct metallurgy based on smelting reduction of hydrogen metallurgy

The chief professors of the Iron and Steel Metallurgy Department of the 2011 Steel Collaborative Innovation Center of Northeastern University proposed a direct steelmaking design scheme based on hydrogen metallurgy for smelting reduction. The scheme uses cold-purified ultra-pure iron concentrate as raw material to achieve source reduction. Ultra-pure molten steel is obtained by 1200 ° C rapid hydrogen reduction and 1600 ° C high energy density iron bath smelting reduction. After continuous casting and rolling, high quality and high cleanliness steel materials are obtained. This process completely eliminates ironmaking and realizes a continuous and integrated production mode of continuous charging, continuous steel making, continuous casting and rolling, with simplified process and improved production efficiency.

5) Technology for separation, collection, storage and utilization of carbon dioxide

It is hoped that through this research, carbon dioxide recovery and storage will be used to significantly reduce carbon emissions during ironmaking and get out of the path of low carbon emissions.

3. Steelmaking technology

1) High-efficiency desulfurization hot metal pretreatment technology

Develop a high-efficiency hot metal pretreatment method with strong mixing and blowing to reduce the sulfur content to an extremely low level in a short time.

2) New process for efficient refining of ladle powder at the bottom of ladle

Development of ladle bottom dusting technology in the refining process outside the furnace. There is no iron loss in the bottom powder spraying process, and the stirring kinetic conditions are better than the top spray powder. The supporting technology is mature and easy to realize. The investment in transformation is low and the original process is not changed. An ultra-low sulfur clean steel production platform can be established to achieve a good sulfur removal effect.

3) Oxide metallurgy technology to manufacture large-line energy welding steel

Carbon oxide steel, HSLA, high-strength steel, etc. for large-line energy welding can be developed by using oxide metallurgy technology. This technology is contrary to the traditional "pure" and "clean" ideas, using the effective control of the inclusion properties (distribution, composition and size) during the steelmaking process, in subsequent solidification, rolling, cooling, Improve the structure of the steel during use to achieve the desired structure and new properties, such as steel for large-line energy welding.

4) Microstructure uniformity control of thick gauge structural steel

The smelting process control implemented by the oxide metallurgy technology is combined with the rolling and cooling control in the subsequent rolling process. On the basis of the smelting process control, a certain final rolling temperature control and cooling rate control are implemented, and a full section can be obtained. (uniform) fine-grained steel with thick crystal structure, high strength and toughness and large-line energy welding performance, can be applied to steel production such as thick plate, heavy-duty H-beam, thick-walled seamless steel pipe.

4, high-quality special steel high efficiency, low cost special metallurgy new process

1) Three refining techniques

After the conventional electric furnace or converter process, three times of refining, such as vacuum consumable furnace or electroslag remelting, can be used to obtain high-purity special steel for high-efficiency and low-cost preparation of special steel materials for aerospace applications. Other high performance metal materials.

2) New generation special steel cleaning and homogenization refining technology

Research and development of a new generation of special steel ladle clean refining technology characterized by non-polluting, heating and deoxidation of molten steel, high-end stainless steel pressurized nitrogen-added metallurgy new technology, electroslag remelting technology based on conductive crystallizer, etc., for the production of high-end alloy steel



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