New technological solutions to protect the lining of blast-furnace hearths

The use of schungite as a partial replacement for coke is practiced in Russia at a number of metallurgical plants, both in the production of foundry iron (its primary use) and in making conversion pig iron. The largest amount of coke is replaced when foundry iron is being made, the replacement coefficient in this case having a value within the range 0.8–1.3. Studies that included continuous monitoring of the temperature of the carbon blocks in blast furnaces with volumes of 1719, 3200, and 5580 m³ unambiguously demonstrate that the thickness of the slag crust in blast furnaces increases with the use of schungite. Protecting the lining of the hearth through the use of schungite is also accompanied by a decrease in coke consumption. __________ Translated from Metallurg, No. 8, pp. 53–57, August, 2007.     

Monitoring the wear of the refractory lining in the blast-furnace hearth

The Razgar Gorna computer program is developed for calculating two-dimensional temperature fields in any vertical and horizontal cross section of the blast-furnace hearth. In the calculations, the heat-conduction equations are solved by means of readings from many temperature sensors (up to 1000, depending on the volume) installed within the furnace lining between the refractory modules. Continuous temperature monitoring at each point permits the determination of the remaining lining thickness and prediction of the onset of lining wear, as necessary. A mathematical model is employed in continuous temperature monitoring of the lining. The database of the Razgar Gorna program relies on the collection, analysis, and transmission of information from the temperature or heat-flux sensors. The program is in use at blast furnaces in Chinese steelworks at Jinan (two furnaces), Jiyuan, and Liuzhou.     

Calculating the blast-furnace profile

A mathematical model is developed for calculating the height and outline of the working space in a blast furnace from the batch surface to the axis of the air tuyere, on the basis of data regarding the density, acceleration of the batch flux, and pressure difference of the gas. The optimal working height of blast furnaces in smelting titanomagnetite sinter and pellets is 10.1–21.8 m. For larger furnace height, relatively immobile refractory batch is formed in the bosh and periodically slips to the hearth, with impairment of the furnace’s thermal state. The calculated values obtained provide guidelines in the design and reconstruction of shaft furnaces.     

Controlling the blast-furnace hearth

At OAO EVRAZ ZSMK, the operation of the blast-furnace hearth is regulated by means of special briquets with good granulometric composition, high iron content, and low impurity content. The briquet charge depends on the total iron-ore consumption, primarily in the intermediate region of the furnace. With steady briquet content (around 2.1% of the charge), the variation in the hearth obstruction is smooth and confined to a narrow range. When the briquets account for 1.0–2.5% of the total charge, the actual mean furnace productivity increases by 6.7%; the adjusted value increases by 3.5%. The actual coke consumption is reduced by 0.5%, and the adjusted value by 0.7%.