In 2019, my country’s pig iron output was 809.3652 million tons, accounting for 63.97% of the world’s iron output, an increase of 5.33% year-on-year, which shows that it is difficult to resolve my country’s ironmaking overcapacity. Individual enterprises eliminated and shut down small blast furnaces, built medium-sized blast furnaces, and carried out capacity replacement; however, medium-sized blast furnaces had a high operating coefficient, and there was an increase in output.
Technical and economic indicators of blast furnace ironmaking In 2019, key iron and steel enterprises increased their energy conservation efforts and adopted comprehensive measures to work hard to achieve the energy-saving and emission-reduction targets stipulated by the state, and achieved an overall reduction in energy consumption in the ironmaking system process, which was completed for my country’s steel industry Contributions have been made to the energy-saving goals of the 13th Five-Year Plan.
In 2019, the fuel ratio of blast furnace ironmaking in key iron and steel enterprises in the country (some enterprises did not include the small lump coke ratio) was 535.03kg/t, an increase of 0.42kg/t over the previous year; the ratio of coke into the furnace was 372.11kg/t, an increase over the previous year 3.56kg/t; the ratio of coal injection was 139.12kg/t, down 2.89kg/t from the previous year; the iron content of the ore into the furnace was 57.42%, an increase of 1.04% from the previous year, and the hot air temperature was 1147.47°C, which was an increase 15.38℃ higher; utilization coefficient of 2.59t/m3·d, an increase of 0.01t/m3·d over the previous year.
At present, the advanced and backward indicators of my country’s iron smelting enterprises coexist and are at different stages of development. In order to promote the progress of my country’s ironmaking production technology, achieve energy saving and emission reduction goals, and enhance the market competitiveness of ironmaking enterprises, we should increase the promotion of mature, advanced and practical ironmaking technology and equipment.
my country’s non-blast furnace ironmaking technology is developing slowly
Non-blast furnace ironmaking requirements for raw fuels: reduced gas composition (CO+H2 content> 92%), natural gas is best, coal is used to produce gas, which is costly; iron ore contains more than 65% of iron, which is harmful Low impurity content.
Up to now, my country’s non-blast furnace ironmaking technology has developed slowly, without major new developments, and the production technology level has fallen behind the international advanced level. In recent years, my country’s reduced iron production has been below 600,000 tons/year. Tunnel kiln direct reduction iron plants have high energy consumption, high pollutant emissions, and unstable product quality, and they must be phased out. In 2007, domestic enterprises introduced COREX and improved many major deficiencies in design and technology. Now they have basically mastered the production technology and reached a relatively good state. There are still many problems that need to be resolved.
In recent years, my country has built a batch of rotary hearth furnaces. The rotary hearth furnaces of Shagang, Maanshan Iron and Steel, Japan Steel, and Laiwu Steel are mainly used to process iron-containing dust and mud from iron and steel enterprises; and the rotary hearth furnaces of Panzhihua Iron and Steel and Sichuan Longman Group Compound iron ore. The charge in the rotary hearth furnace is heated and reduced on a rotating plate, mainly relying on radiation heat transfer, the thermal efficiency is low, the reduced pellets, the heating and reducing atmosphere on the bottom of the plate are insufficient, and The metallization rate of the product is low (usually 60%~80%), the energy consumption is high (the thermal efficiency is up to 50%), and the FeO content is high. It is difficult to produce raw materials of quality that can meet the needs of electric furnaces. Therefore, the metallization rate, process energy consumption, and production cost of the product are all inadequate compared with the blast furnace. The main problem is that the product quality does not meet the standards required for electric furnace production (quality requirements for direct reduced iron: H88 grade iron Grade ＞88%~90%, H90 grade iron content should be higher than 90%~92%, H94 grade requires iron content ＞94%; metallization rate is required for level 1＞94%, level 2＞92%, level 3＞ 90%, level 4>88%; SiO2 content <3%~7.5%. For every 1% increase in SiO2 content, 2% more lime should be added to the electric furnace steelmaking, the slag volume will increase by 30kg/t, and the electric furnace will consume 18.5kWh/ t). Although the rotary hearth furnaces of some companies have passed the technical appraisal of experts, they need further scientific analysis, practical testing, and withstand the test of time before they can be universally recognized in the industry. People in the industry believe that the treatment of iron-containing dust and sludge by rotary hearth furnaces is reasonable, and the product has a low metallization rate. It can reduce the coke ratio when used in blast furnaces and cannot be used for electric furnace production; if iron ore is used for reduction in rotary hearth furnaces, it is not necessary The blast furnace causes high costs and the process is not feasible. If a rotary hearth furnace is used to process vanadium-titanium magnetite and recover titanium oxide, although the energy consumption is high, the economy is good.
Therefore, the author still suggests that my country should strengthen research and follow up on new developments in non-blast furnace ironmaking technology at home and abroad, and refrain from large-scale promotion of new non-blast furnace ironmaking facilities to avoid negative impacts.
Post time: Nov-21-2020