Blast furnace blowing

Drying air heaters and ovens

The blast furnace and the block of air heaters are dried after they are tested for density and after the installation of all the equipment. To remove moisture from the refractory masonry, it is heated to temperatures of 100-165 ° C. Typically, the duration of drying and heating of air heaters is about 7 days.

Refractory masonry blast furnace contains a significant amount of moisture. When drying the oven, moisture is removed through the top. To facilitate the removal of moisture from the bream, it is dried as each row is laid using electric heating devices. The most convenient, safe and cheapest way to dry a blast furnace is by hot air drying. Therefore, the drying of air heaters is usually completed before drying the oven. The blast furnace is dried according to the following schedule: gradual heating to 600 ° C for 2 days, holding at this temperature for 1.5 days and natural cooling (usually about 1.5 days) ^[1] .

Loading charge charge

The following requirements are imposed on the charge charge .

• Iron ore materials that are part of blowing charges should be easily reducible to reduce the degree of direct reduction in the process of blowing the furnace and reduce the specific consumption of coke .
• Burden materials must be strong, since materials are loaded into the furnace from a great height.
• The amount of fines (fractions less than 5 mm) in the iron ore material should be minimal.
• Coke, which is part of the charge charge, must be low sulfur. This is due to the high consumption of coke in the blowing charge, which makes it difficult to obtain cast iron , conditional on the sulfur content.
• Burden materials should contain a minimum amount of hygroscopic moisture. This is due to the fact that the evaporation of moisture from the charge during the blowing process, unlike the usual blast furnace mode, occurs with additional heat and an increase in coke consumption.

Blowing charge is characterized primarily by the high specific consumption of coke. This is dictated by the need to heat both the charge column and the refractory masonry to operating temperatures ^[2] .

Blowing charge is calculated on receiving cast iron with a silicon content of 1.5-2.0%. In this case, graphitization of the refractory masonry and the formation of a stable skull are occurring. Blowing charge is calculated on the basis of slag CaO / SiO ₂ = 0.9-1.1. Despite the high sulfur content in the blowing charge, an increase in the basicity of slag above the specified is considered impractical because of the increase in their melting points, and also because the main slag is of the “short” type; this can contribute to the formation of crusts in the initial period of operation of the blast furnace. Blowing charge often consists of 4-5 charges, each of which includes 5-7 innings ^{[3] [4]} .

The task of the initial moment of blowing a blast furnace is to provide quick ignition of fuel on all air lances, to “trigger” the charge in the very first hours after blowing and to prevent clogging of the hearth, which complicates the development of smelting products. The loaded hearth should have good gas permeability, provide drainage of cast iron and slag melts, as well as the ability to quickly open the cast iron letok.

When loading, the bottom of the furnace, including the hearth, is specially prepared for receiving the charge charge. The main preparatory operations are as follows.

• Shotcrete walls of the hearth and the surface of the bream with refractory concrete or lining with fireclay bricks of the walls of the metal receiver and shoulders.
• Covering the shoulders with sleepers .
• Checking the tightness of the air tuyere installation.
• Installation of slag devices.
• Laying granular blast-furnace slag on the flask of the furnace to the threshold of the cast-iron notch (sump of the furnace) to create a protective layer on the flask and to slag the seams of its surface.
• 4-inch-diameter steel pipes are introduced into the cast iron flats (if there are several), reaching the center of the hearth. 7-10 mm holes are made along the length of the pipe (inside the furnace), which are staggered along its surface. This is necessary to direct the flow of heated gases to the bottom of the furnace and to heat the furnace hearth.

After preparatory operations, the furnace is actually loaded ^[5] .

Blow-up period

In the blow-up period, the charge and refractory masonry warm up. Typically, the initial set amount of blast is 50–70% of the nominal. Blowing speeds reach 230 m / s, and in Japanese practice blowing furnaces up to 260-300 m / s.

At the end of heating the masonry of the furnace and the beginning of the expenditure of heat on the actual process is indicated by the temperature rise of the masonry of the mine on the horizon of the top ^[5] .

First production of pig iron and slag

The time of the first release depends on the number of feeds of the charge. Approximately this time is from 16 to 24 hours ^{[6] [7]} .

The furnace loading begins after the charge is moved at a blast furnace gas pressure of at least 6–7 kPa (600–700 mm water column). After the blow-up period, normal operation of the blast furnace occurs ^[8] .

• Domain process
• Blast furnace

• Wegman E.F. , Zherebin B.N., Pokhvisnev A.N. et al. Iron metallurgy. - Moscow: Academic book, 2004 .-- 774 p. - ISBN 5-94628-120-8 .
• Ramm A.N. Modern domain process. - Moscow: Metallurgy, 1980 .-- 303 p.
• Babarykin NN Theory and technology of the domain process. - Magnitogorsk: GOU VPO "MSTU", 2009. - P. 15. - 257 p.
• Dmitriev A. N. et al. Fundamentals of the theory and technology of blast furnace smelting. - Ekaterinburg: Institute of Metallurgy, Ural Branch of the Russian Academy of Sciences, 2005. - 541 p. - ISBN 5-7691-1588-2 .