SU1726540A1 - Method of heat treatment of ore-carbon single-layer pellets - Google Patents

Abstract

The invention relates to the preparation of raw materials in the ferrous metallurgy, in particular to the production of agglomerated iron ore materials. SUMMARY OF THE INVENTION: 4-20 mm ore-coal pellets are loaded onto a conveyor machine, dried, pellet fuel is ignited from an external heat flow with a capacity of (0.25-0.40) 106 kJ / T pellets, and then sintered and subjected to cooling. The thermal capacity of internal sources and heat sinks in the pellets is set depending on their size. For pellets with a fraction of 4-6 mm, this power is set to 6.0-6.5 of the external heat flux power, and with increasing pellet size for every 2 mm it is increased by 0.4-0.6 of the external heat flux. The regulation of internal sources and heat sinks by size of pellets leads to a significant improvement in the quality of the finished product by increasing the content of residual carbon in the pellets. (Ls

Description

The invention relates to the preparation of raw materials in the ferrous metallurgy, in particular to the production of agglomerated iron ore materials.

The aim of the invention is to improve the quality of the finished product.

The heat treatment of the ore-coal pellets is divided into drying, ignition, sintering and cooling. Drying of the pellets is carried out at temperatures up to 400 ° C to avoid destruction of the pellets due to thermal stresses and the active condensation of moisture on the surface of the granules. The ignition is carried out by burning external fuel in an incendiary furnace, obtaining combustion products with a temperature of 1000-1300 ° C, sucking these products through the layer from top to bottom and igniting solid fuel rolled into granules. Sintering is carried out by the heat of oxidation of the solid carbon of the granules when it is sucked through the layer of atmospheric air. Cooling is carried out upon completion of the sintering of the granules — with intensive filtration of the cooling agent through the bed.

The heat treatment is subjected to granules with a particle size of 4-20 mm. With a smaller pellet size (less than 4 mm), the gas permeability of the layer decreases, the residual carbon of the pellets burns to a value below 0.45%, i.e. the quality of the finished product deteriorates. With a larger particle size of pellets (more than 20 mm), their mechanical and metallurgical strength is insufficient for domain processing.

The amount of external heat flow in the igniter should be maintained

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within (0,25-0,40) -106 kJ / t of pellets. With a lower external heat flux (less than 0.25-U6 kJ / ton of pellets), reliable ignition of solid carbon of pellets is not ensured, their sintering process is destabilized, and the quality of finished products deteriorates. With a higher power of external heat flow (more than 0.40–106 kJ / t pellets), the quality of the finished product no longer improves, and the specific heat consumption per process increases.

The total thermal capacity of the internal heat source with a pellet size of 4-6 mm is set to 6.0-6.5 of the external heat flux power. With a smaller total thermal capacity of the internal heat source (less than 6.0 from the external heat flux power), the residual carbon content in the finished product is not enough for reliable and sufficiently significant intensification of the domain redistribution (note that for the domain redistribution, the residual carbon content in the granules must be kept within 0.45-9.50%). With a larger total thermal capacity of the internal heat source (more than 6.5 external heat fluxes) under conditions of a developed total surface of the firing layer of pellets, their sintering into one solid mass (sinter), deterioration of the finished product quality, including pellet strength, becomes possible. The indicated value of the total thermal capacity of the internal heat source is valid only for pellets up to 6.0 mm. Exceeding this size requires an increase in the total thermal capacity of the internal heat source. Otherwise, without improving the sintering process (in the absence of sintering), the content of residual carbon in the final product decreases, i.e. its quality is deteriorating.

An increase in the average size of pellets, starting from 6.0 mm, for every 2 mm should be accompanied by an increase in the total thermal capacity of the internal heat source by 0.4-0.6 of the external heat flux. In the absence of such an increase in the total heat output of the internal heat source, the residual carbon content in the finished product begins to decline and the quality of the finished product deteriorates. With an increase in the total thermal power of the internal heat source by a smaller amount (less than 0.4 of the external heat flow power), the residual content

carbon in the finished product does not reach the limit values and the quality of blast-furnace raw material deteriorates. With an increase in the total thermal capacity of the internal heat source by a larger amount (more than

0.6 of the external heat flux), it becomes possible for the sintering of the pellets into one continuous mass, which significantly impairs their quality.

Reducing the consumption of blast furnace coke and

An increase in the productivity of blast furnaces is provided by using in the blast furnace charge, obtained agglomerated materials with a solid reducing agent and iron oxides in one granule (piece, druse). Direct contact of carbon with iron oxides under conditions of sufficient, besides the traditional level, temperature potential provides an increase in the flow rate

reduction processes 2.5-3.0 times and replacement of blast-furnace coke with cheaper fuels contained in the smelted granules. The inclusion of solid fuel directly into the material being melted ensures a uniform distribution of the reducing agent throughout the entire mass of material and, consequently, an increase in the productivity of blast furnaces.

The application of the invention provides

lowering the specific consumption of blast furnace coke and reducing the removal of flue dust.

Claims (1)

The invention The method of heat treatment of coal single-layer pellets of 4-20 mm size on conveyor machines, including drying, ignition of pellet fuel from external heat flux with a capacity of (0.25-0.40) -106 kJ / t pellets, sintering and cooling, in order to improve the quality of the finished product, with a pellet size of 4-6 mm, the total thermal capacity of internal sources and heat sinks in the pellets is set to 6.0-6.5 of the external heat flux, and when the average pellets size for every 2 mm total thermal capacity of internal sources and heat sinks increase by 0.4-0.6 external heat flow capacity.