SU1481261A1 - Method of thermal treatment of iron ore pellets - Google Patents

Abstract

The invention relates to the field of ferrous metallurgy and is intended for heat treatment of iron ore pellets on conveyor-type kiln machines. The aim of the invention is to reduce fuel and energy costs and improve the quality of finished products. The method involves laying a layer of pellets, drying, strengthening firing and cooling, and after completion of drying the upper part of the layer of pellets to a depth of 0.2-0.4 of its total height, a non-emitting flow of heat carrier temperature of 650-750 ° C is passed through it for 2- 7 min 1 tab.

Description

The invention relates to ferrous metallurgy and can be used to obtain an agaric iron ore material.

The purpose of the invention is to reduce fuel and energy costs and improve the quality of the finished product.

The essence of the method lies in the heat treatment of the pellets with their preliminary exposure to a stationary temperature potential non-radiant field and subsequent abrupt heating to temperatures close to the material softening temperature.

The method of heat treatment of the pellets includes an intermediate zone between the drying and strengthening firing of the preheating zone. Heating of the pellets can be either smoothly limited to 100 ° C (heating value),

or intermittent (transfer of pellets from the drying zone with a temperature of up to 400 ° C to the burning zone with a temperature of 1200-1400 ° D). Smooth heating of the pellets leads to the production of pellets with a pronounced zonal structure, which leads to a decrease in strength during recovery. In the case of a jump-like heating of the layer, insufficiently prepared dry granules are transferred under the influence of high-temperature glowing natural gas flames (fuel oil, etc.). These granules in their mass are heated unevenly, often moisture is retained in their center. When they are exposed to high-temperature carbides, they lose their strength, are partially destroyed, and require an increase in the duration of their heat treatment. Suschest400

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The specific heat consumption of the pa process increases. Therefore, heat treatment of the pellets is intense heating should be combined with preliminary preparation of the pellets — they are held at sufficiently high temperatures (until the center and the periphery of the piece are equal), but under conditions that exclude the effect of radiant heat on the pellets. vodopotoka.

Heat treatment of pellets with an abrupt change in temperature potential (heat shock one or more) requires the necessary preliminary preparation of the granules — equalizing the temperature between the center and the surface of the piece to at least 80-100 ° C. In this case, the pellets withstand thermal shock of up to 800-90P ° C (for example, 400-1300 ° C) without a noticeable decrease in their strength. The organization of a sufficiently effective heating of the piece is carried out by holding the pellets in a stationary temperature non-emitting field. Moreover, in this field, there should be no such radiation sources as burning torch burning fuels. Otherwise, the heat supply to the granule from different sides of its surface will be different, the unevenness of temperature in the mass of the piece increases and the quality of the finished product deteriorates,

After the completion of drying of the layer to a depth of 0.2-0.4 of its total height, the pellets are aged in a stationary non-irradiated flow of heat-transfer agent.

A stationary non-radiant temperature field is formed either by burning fuel in external fire chambers — chambers, or by using recirculating collector air, or by the equipment of the firing machines with shielding surfaces in the path of radiant heat fluxes.

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PRI im p Raw iron ore pellets laid on ranged tellys are directed to the drying zone and to the end of the zone moisture from them is removed to a depth of 0.2-0.4 from the total height of the layer. After drying to the specified

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the value of the pellets is maintained in a non-radiant flux coolant with a temperature of 650-750 ° C. This coolant receives from the overflow collector and is transferred to the sections of the furnace hearth of the burning machine that follow the drying zone (burning of external fuel in the furnace in this section is excluded). Exposure of pellets in a stationary non-radiant temperature field ensures the preparation of pellets for thermal shock and the subsequent intensification of the process to the limit values when obtaining finished products of sufficiently high quality. In a stationary temperature field the pellet is kept for 2-7 minutes, which ensures a decrease in temperature difference between the center and the periphery of the piece to 80 ° C and below. Upon completion of this process, the temperature in the furnace rises abruptly to the limiting values, the pellets are subjected to strengthening firing and cooled.

The depth of layer drying is periodically determined by sampling the height of the layer, the time required for the process to heat the layer is determined and the process is monitored. The process is controlled by varying the speed of the kiln carts.

The temperature of the coolant is controlled by standard thermocouples and controlled by changing the coefficient of excess air drawn into the system.

The duration of the layer exposure in a stationary temperature field is controlled by the speed of movement of the conveyor machine and controlled by changing this speed.

The table shows the indicators of the process of firing pellets on conveyor machines of the type OK-ZOb with aging before firing in a stationary temperature field and in the absence of such exposure.

The application of the method ensures a reduction in the specific gas consumption per process by a 5-9% increase in the strength of pellets by 15-30 kg / ok, a decrease in the fines content in the finished product by 0.4-0.5 abs.%.

Claims (1)

Invention Formula The method of heat treatment of iron ore pellets mainly on conveyor-type kiln machines, including laying a layer of pellets, drying, strengthening obdig and cooling, in order to reduce fuel and energy costs and increase the quality of the finished product, after the drying of the upper part of the pellet layer to a depth of 0.2-0, the total height of it, passes through the flow of the heat carrier with a temperature of 650-750 ° C for 2-7 minutes. Known method 0.87 Years old The proposed method Not 24.7 204 2.60