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Some effective measures for blast furnace energy conservation and emission reduction
Jan 19, 2018

Blast furnace energy-saving emission reduction has become the steel industry to achieve low-carbon development priorities. After years of energy conservation and emission reduction efforts, some large-scale iron enterprises in our country (such as Baosteel) have been able to reduce the energy consumption of the blast furnace process close to or reaching the world advanced level. Some high-level blast furnace equipment, the energy-saving emission reduction has been in the bottleneck stage. Therefore, the study of blast furnace energy-saving emission reduction, but also need to further seek new ideas and new methods.

Since the blast furnace reaction is a large-scale reduction process for deoxygenation by carbon, its nature determines the high energy consumption and high emission. Only by improving the raw fuel conditions, there is a limit to enhancing the energy-saving and emission reduction effects of operation and application of advanced equipment. In recent years, some researchers have proposed some effective energy-saving and emission-reduction measures that can be implemented without making fundamental technological changes to the blast furnace.

First, blowing waste plastic

Abandoned plastics used in blast furnace ironmaking process, including sorting, crushing and pelletizing, resulting in particles of appropriate size, instead of part of the pulverized coal injected into the blast furnace to reduce coke consumption. Spraying waste plastic can not only replace some of the coal, fuel savings, but also deal with white pollution, both energy saving and environmental protection. However, waste plastics will also bring harmful substances such as sulfur into the blast furnace, which should be paid attention to.

Second, the gas from the cycle

Blast furnace has a high thermal efficiency, at 60%. In addition to the loss of cooling water away and heat loss ~ 3%, blast furnace slag sensible heat ~ 4%, the other mainly for the effective use of blast furnace gas contained in the latent heat. Blast furnace gas is used to generate electricity, and its efficiency is less than 30%. The remaining 70% of the latent heat is wasted. At the same time, blast furnace gas combustion can cause a large amount of CO2 to be released into the atmosphere. In view of this situation, the use of full oxygen blast furnace can make good use of gas, which is characterized by using all-oxygen blast instead of the traditional hot air blasting, blast furnace gas generated at the top of the furnace CO2 and CO separation, and CO2 Trapping the remaining CO heating after re-blast into the blast furnace to reduce the fuel ratio, the formation of gas self-cycle. Oxygen blast furnaces are expected to reduce carbon consumption by 24% and coke ratio to 210 kg / t. CO2 emissions can be reduced by 50% and 26%, respectively, with or without sequestration.

Third, the injection of coke oven gas

Coke oven gas injection into the blast furnace, the blast furnace coke ratio can be reduced to 200 kg / t or less. Injection volume can be between 100 m3 / t and 200 m3 / t. Blast furnace coke oven gas injection nozzle installation site there are two: First, through the tuyere to replace the pulverized coal injection; the second is from the lower part of the furnace opening blowing holes for injection. Starting from the reaction principle in the furnace, coke oven gas injected from the lower part of the shaft body can avoid massive combustion directly at the tuyere, which makes the reduction of H2 and CO in the gas more indirect and theoretically more advantageous. Injection 1 m3 coke oven gas can replace about 0.7 kg coke or 0.8 kg pulverized coal.

Fourth, strengthen low-power design

The blast furnace project in the initial design stage to maximize energy-saving design. Including reasonable and compact logistics design, such as using one-can system, reducing the time of molten metal's downtime and reducing the temperature drop of molten iron; the requirement of energy medium should be calculated as accurately as possible to prevent the design value from being excessively surplus from the actual demand The amount of waste to form; equipment selection should be based on precise matching, especially fans, motors and other energy-intensive equipment to prevent the "big horse-drawn car"; in the pipeline design should strive to rationalize the layout to reduce heat loss of energy medium; etc.