Steel

Blowing oxygen to make steel: blowing oxygen to make steel, has been widely used in all countries, has become an important way to leap forward the development of iron and steel industry. The main ways of oxygen blowing steelmaking are: pure oxygen top blowing or bottom blowing in converter, electric solitary furnace steelmaking and open hearth steelmaking.

The oxygen consumption of converter steelmaking is 50~60m3 per ton of steel; The oxygen consumption per ton of steel is 10~25m3; Open-hearth steelmaking consumes 20~40m3 oxygen per ton of steel. Percentage of various steelmaking methods in countries or regions of the world in 1993 (%), among which: Converter steel is 63.8% (61.8% in USA, 68.8% in Japan, 100% in Luxembourg and 90.1% in Austria), and EAF steel is 21.8% (38.2% in USA, 31.2% in Japan). 9.9% for Austria), 14.2% for open-hearth steel (0 for US, Japan and Austria), and 0.2% for other steel (0 for US, Japan and Austria). World: converter 59.4%, electric arc furnace 31.0%, open hearth furnace 9.6%, other 0.1%. In the 1990s, the short process technology of electric furnace developed vigorously in the world. Modern large electric furnace adopts various enhanced oxygen supply technology to improve production efficiency and reduce power consumption. Compared with 30 years ago, the smelting cycle of electric furnace is reduced from 210min to 55min, the smelting power consumption is reduced from 650kWh/t to 350kWh/t, and the oxygen consumption is increased from 8m3/t to 35-60m3 /t. The oxygen for steelmaking requires the purity of oxygen to reach 99.6%, avoiding oxygen absorption by molten steel. Generally, the main pipe pressure is greater than 2MPa, the working pressure is greater than 1.2MPa, and the gas is required to be clean, without water or oil.

In addition, rolling steel per ton of steel oxygen consumption 3~6m3, steel processing, continuous casting billet flame cutting, flame clearance, furnace lining flame per ton of steel oxygen consumption 11.4~14.2m3.

Oxygen enriched blast furnace coal injection for iron making: Oxygen enriched blast furnace coal injection for iron making can improve the utilization factor and reduce the coke ratio. From March 12, 1991 to May 24, 1991, Shougang Company carried out a high oxygen enriched coal injection test in No.1 blast furnace. The highest oxygen enriched rate reached 5.5%, and the increase of pig iron was 2.5%~3.0% for each oxygen enriched 1% in blast wind. The heating value of gas can be increased by 1.28%~2.00% per 1% oxygen enrichment, which is equivalent to the increase of air temperature by 32~79℃.

Ansteel No.2 blast furnace oxygen-enriched coal injection smelting test (March 1992 ~ March 1993), oxygen provided by Ansteel oxygen plant, gas volume 10000~12000m3/h, purity 99.5%, pressure 1.2~1.6MPa (before entering the blast furnace cold air decompression to 0.6MPa). For safety, nitrogen and pressure sharing facilities are installed in the system. Smelting results show that, after oxygen enriched air blowing, the average increase of oxygen enriched 1% can be 2.27%, the temperature increases by 35℃, and the cost of iron per ton is reduced by 6.91 yuan. December 14~15, 1993, the Department of science and technology of the Ministry of Metallurgy organization appraisal, when enriched oxygen to 24.71%, the amount of coal injection reached 161kg/t, coke ratio into the furnace to 407kg/t, comprehensive coke ratio to 536kg/t.

Smelting reduction ironmaking: In the 21st century, the basic requirement for the development of iron and steel industry is to eliminate environmental pollution. In order to change the pollution situation of iron and steel industry, many developed countries have invested heavily in developing smelting reduction iron making technology. Molten reduction uses pure oxygen combustion coal instead of coke to make iron. At the same time, a large amount of high calorific value clean gas is produced as energy output.

Posco has ordered from Voestalpine a COREX melting reduction furnace unit (model C-2000, 2000 tons of iron per day) with an annual output of 600-700,000 tons of molten iron, which has been put into production in December 1995. Compared with the traditional blast furnace process route, the cost of molten iron in COREX equipment is reduced by 30%, SO2 emission is reduced by 94%, NOx is reduced by 78%, and dust is reduced by 97%.

Ningbo Beilun Steel Works, also using smelting reduction iron making method, plans to adopt two sets of C-2000 COREX devices, iron making, double blowing converter, thin slab continuous casting and rolling, cold continuous rolling, the total investment of 12.6 billion yuan. The annual design of steel production 1.6 million tons. According to the estimate, if the pelletizing scheme is adopted, two sets of 62000m3/h air separation equipment should be equipped; In case of block mining scheme, two sets of 71000m3/h air separation equipment are required. Technical specifications: oxygen consumption 580m3/t iron, 2×600 type shaft furnace needs nitrogen 700m3/t iron. The requirement of oxygen purity can be lowered to 92-95% for the oxygen used in blast furnace oxygen-enriched ironmaking.

Full oxygen blast furnace ironmaking: The former Soviet Union Moscow Iron and Steel Research Institute, 1033m3 blast furnace on the 100% use of oxygen test, gas preheating in the hot blast furnace regenerator, and then instead of the usual hot air blown into the blast furnace, and then in each outlet into oxygen injection. The process was tested 12 times between 1985 and 1990, producing 250,000 tons of molten iron. In one test, the coke ratio of molten iron reached 3677kg/t, with oxygen 2517kg/t molten iron, and the daily production of molten iron containing 2.2%Si was 1700 tons.

Nitrogen in the steel plant application: mainly used as a protective gas, such as steel rolling, zinc plating, chromium plating, heat treatment (especially thin steel sheet) continuous casting, nitrogen as a protective gas, and nitrogen purity requirements of more than 99.99%. The chemical properties of argon are used in the smelting of special metals, such as lithium, beryllium, uranium, plutonium, thorium, titanium, zirconium, hafnium, niobium, tantalum and other rare metals needed in nuclear and space industries. Argon is used as an ambient gas in the reduction reaction. In the process of refining silicon and germanium and preparing single crystal, argon is also used as ambient gas to protect crystal growth.

In the process of steelmaking, argon is also used: for example, argon is blown into molten steel to make the composition uniform, purify the liquid steel, remove the impurities such as hydrogen, oxygen and nitrogen dissolved in the molten steel, and improve the quality of the billet. Blowing argon can also cancel the reduction period, shorten smelting time, increase output, and save energy. Argon blowing and protection is an important way to improve steel quality. It is reported that argon gas consumption is 1^3m3 tons of steel.

Oxygen, nitrogen and argon are indispensable industrial gases for steelmaking enterprises. According to Tianjin Steel Pipe Company, the company's self-produced secondary energy consumption is: annual oxygen consumption of 2046m3, in which the furnace process with oxygen accounted for about 79.2%, continuous casting cutting oxygen accounted for about 6.1%, scrap cutting oxygen accounted for about 5.9%, other oxygen accounted for about 8.8%; The annual nitrogen consumption is 21.41 million m3, of which 80.2% is for direct reduction iron protection, 15.3% is for smelting process, and 4.5% is for lime kiln and power plant. The annual consumption of argon is 294,000 m3, all of which is used for steelmaking, of which 61.8% is used for smelting and 38.2% for continuous casting.

It has been reported that the combined oxygen consumption of iron making, steel making and steel rolling has reached 100^ 140m3/t, nitrogen consumption 80^ 120m3/t and argon consumption 3^ 4m3/t.

Out-of-furnace REFINING: THE PRIMARY TASK faced by steelmaking and continuous casting enterprises is to improve the quality of steel and expand the variety of steel, while the OUT-OF-furnace refining process is the key, especially for the production of high grade steel and high value-added products and improve their competition. The refining of liquid steel outside the furnace is to move the refining tasks to be completed in the general steelmaking, such as desulfurization, deoxygenation, degassing, removal of non-metallic inclusions, adjustment of steel and liquid steel temperature, etc., to the "ladle" or special container outside the furnace. The off-furnace refining process is closely related to the use of industrial gases and can be generally divided into vacuum refining process and non-vacuum refining process.

Vacuum refining method includes :(1) vacuum blowing argon method (2) vacuum blowing oxygen decarbonization refining method (3) strong stirring vacuum blowing oxygen decarbonization refining method (4) converter vacuum blowing oxygen decarbonization refining method includes :(1) argon oxygen furnace decarbonization refining method (2) gas oxygen furnace decarbonization refining method (3) ladle blowing argon method (4) sealed blowing argon method (5) ladle with cover blowing argon method.