SU1032021A1 - Method for reducing iron ores in stepped-fluidized bed furnaces - Google Patents

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L; This invention relates to the preparation of iron ore in ferrous metallurgy.

There is a known method of using solid fuels in furnaces of a step-weighted layer for reducing iron ores, including controlling its size and feeding into the unit together with the material flow. Solid fuel is fed into the furnace volume to create a C 13 reducing atmosphere in it.

However, the disadvantages of the method are: a) the burning of volatile fuels in areas of the furnace with a significant oxygen content. As a result, such active reducing agents, such as hydrogen and carbon monoxide, burn and do not participate in the process of reducing heat treatment of iron ores, b) the fuel enters the re-reduction chamber with a reduced (due to volatile) content of the reducing agent. As a result, the specific productivity of the process is reduced;

c) insufficient, high recovery rates, especially in the suspended layer, which leads to a deterioration in the quality of the finished product (reduction in the recovery rate); g) the use of solid fuel without regard to it

physico-chemical properties, i.e., the lack of integrated fuel utilization. These deficiencies are partially eliminated when the fuel is supplied through gas-air transportation of the tuyere directly to the zone of partial recovery of the furnace.

The closest to the proposed technical essence and the achieved result is a method of reducing iron ores in furnaces of a step-weighted layer, including the supply of dispersed ores and solid fuel, drying, magnetizing roasting and subsequent recovery, regulation of the size of pieces of solid fuel burned in the furnace heating and creating a reducing atmosphere and supplying it to the redevelopment chamber for direct reduction of C2j.

However, the method includes the regulation of fuel krudnosti and flow into the unit together with the gas-air flow. By this method, the fuel

O, 1-1.0 mm, fully burned in a furnace, and fuel, 1.5-3.0 mm, 10-20% of the size and sent to the re-recovery chamber as burning.

The disadvantages of this method are: a) the burning of volatile, even from the fuel of large fractions in areas of the furnace with a significant oxygen content, as a result of the active fuel (hydrogen, carbon monoxide)

sorts) with a high content of volatile and insufficient size of the piece burned in the furnace and are not involved in the recovery process, and the intensity of the recovery process decreases; b) the lack of relationship between the physico-chemical characteristics of the fuel and its size, which reduces the efficiency of fuel use and leads to an increase in heat consumption in the process; c) accidental combustion; combustible elements of solid fuel at individual stages of the process — as a result, either insufficient (if excessive fuel crushing) or excessive carbon gets into the re-reduction chamber, and the final degree of ore reduction (i.e., the quality of the finished product), or part of the fuel is irrevocably lost with the flow of the ore being unloaded; d) insufficiently high rates of ore reduction in the suspended layer.

The purpose of the invention is to improve the quality of the finished product and increase productivity.

The goal is achieved by the fact that in the method of reducing iron ores in furnaces of a step-weighted layer, including the supply of dispersed ore and solid fuel, drying, magnetically burning and subsequent re-recovery, adjusting the size of the pieces of fuel burned into the furnace volume and feeding it into the removal chamber , the size of the lumps of the feed together with the material of the fuel with a content of 1.5-2.5% of volatile, is set equal to 0.5-2.0 mm, and with an increase in the scientific research institute of volatile by 10% over 2.5%, the size of the lumps is increased by 4060 % .

Ore loaded into an aggregate of cheese with an average particle size of 0.1-0.6 mm and solid fuel enters the kiln with a step-weighted layer in which moisture is removed from it, it is heated to 900-1000 ° C and is partially restored (up to 20-30%). Then the mixture (a mixture of ore and solid fuel) is fed into the recovery chamber. In this case, the charge in the furnace is transferred from stage to stage in a suspended state towards KciMepe after-treatment under the influence of high-speed air flows through the tuyeres. High-speed streams after damping, the speed moves under the furnace roof towards the recovery chamber, down and move, as shown experiments, with a height of 1.52, 0 m from the level of tuyeres towards the discharge pipe. In the region of the 1st row of the tuyeres, the air flow rises upward through the fluidized bed of the rims and is withdrawn from the furnace. The solid fuel transported with the material stream is heated, combusted at C, partially burns in the preheat zone and in an oxidizing medium (giving its heat to the intensification of heat and mass transfer processes) and forms reducing components (H, j, CO) of gas phases in the partial recovery zone of the furnace. In order to transfer enough heat to develop heat and mass transfer in an oxidizing environment, it is necessary to burn 30-40% (absolute) of combustible elements of solid fuel. When burning less than 30% of combustible elements. Solid fuel, the consumption of natural gas increases excessively and the proportion of relatively cheap and non-deficient solid fuels (brown coal, anthracite, etc.) decreases. When more than 40% of combustible elements of solid fuel are burned, solid fuel with an excessively low reactivity and the intensity of the reduction process drops noticeably. In the partial reduction zone, 10–20% (absolute) of combustible solid fuel elements should be used. At a flow rate of less than 10% solid fuel cell. In the gaseous environment of this zone, the amount of reducing components is insufficient. iron ore charge of the required value. With consumption of more than 20% of combustible solid elements, the recovery process in the furnace is no longer intensified, and the chemical value of the fuel, uzhaemogo in dovosstanovleni camera, an existing member-venno falls. . In the re-reduction chamber, the restorative heat treatment of the ore is completed due to unspent 4060% of combustible solid fuel elements. This mode of fuel use is provided by adjusting its size depending on the content of volatile fuel. So, when the content of volatile in the fuel of 1.5-2.5% of the size of a piece of fuel is set equal to 0.5-2.0 mm. Solid fuels with a volatile content of less than 1.5% are now virtually non-existent. When the content is volatile in the fuel is more than 4.0%, its average particle size must be increased over 2.0 mm. The use of fuels with a volatile content of 1.5 to 2, 5% and an average particle size below 0.5 mm leads to the complete combustion of combustible components directly in the furnace volume and the lack of a solid reducing agent fed into the re-treatment chamber. When the size of the piece is more than 2.0 mm, a sufficient supply of chemical energy of the fuel to the zones of oxidative heating and partial reduction is not provided at the required level. An increase in the volatile content in fuel of 2.5% for every 10% should be accompanied by an increase in the particle size from 2.0 to 0.8-1.2 mm. With a smaller increase in the size of the piece (less than 40% (0.8 mm) for every 10% increase in the volatile content of the fuel), there is a complete combustion of combustible components directly in the furnace volume and a lack of solid reductant in the recovery chamber. With a larger increase in the particle size (more than 60% of 1.2 mm) for every 10% increase in the volatile content of the fuel, a significant portion of the unreacted fuel is lost with the ore being shipped. The essence of the method consists in determining the optimal size of solid fuel depending on its volatile and metered use of chemical energy of fuel at the stages of oxidative heating, partially and completing the reduction. Example. According to the characteristics of certain types and varieties of fuels entering the furnace of a step-weighted layer, namely, the content in nmx volatile establish the average particle size of solid fuel. For example, when using lean coals of the Krasnogorsky mine with a volatile content of 2.0%, it is pre-ground to an average size 1.5 mm. Below ± 1, coal is included in the material flow and fed through a charging device into the furnace of a step-weighted layer. Under the influence of directional air currents supplied through furNl located between adjacent steps and having a speed exceeding the soaring speed of a separately taken piece, the material is transferred in a suspended state from step to step along. direction in the re-recovery chamber. The gas-air mixture is formed from natural gas and air, prepared through transporting tuyeres (if necessary, coal with the specified fineness can be included in this mixture) and burn directly in the furnace volume. Processing of the charge after the drying zone enters the heated zone of the furnace. In the zone of oxidative heating, natural gas and 30% of combustible solid fuel elements are combusted. Due to the physical heat of the combustion products, the mixture is heated to 95 ° C and transferred at this temperature to the partial reduction zone. Natural gas and 15% solid fuel are burned in this zone, with an air flow rate of 0.85 forming a reducing atmosphere with a l. her Hj, CO and CH. Due to these components, partial reduction of iron ore occurs in the furnace.

Unreacted coal (55% of the fuel was made) together with the ore enters the recovery chamber and ensures the completion of recovery processes in it. The recovered charge from the after-treatment chamber is discharged and fed to the final product storage.

The volatile content of solid fuels is contrasted by his chemanapysis and is regulated by changing the type of fuel used.

The average size of solid fuels is controlled by rassevkanu on standard sieves and regulate the change in mode of operation of the equipment for grinding COAL.

The amount of burning combustible elements of solid fuel in the zones of oxidation heating and partial reduction is controlled by chemical analysis of samples of gas and material taken (gas continuously, material periodically) from the furnace and controlled in the zone of oxidative heating by changing the speed of heating and the level of maximum temperatures, in the partial recovery zone - by changing the air flow rate.

When used as a solid fuel brown coal Chep. Binskoe field with a volatile content of 43% in the method should be made following adjustments. The average size of the coal is calculated by a ratio of 43 - 2.5

2.0

rljO 6.2

100

where 1.0 mm is the increment value of the fuel size for every 10%, starting with 2.5%, the volatile content in the coal settlement is 50%. The remaining stages of the process are left unchanged.

The application of the proposed method provides an increase in the output of the aggregate by 13–15% and an increase in the final degree of reduction of the gross supply by 17–20%. The degree of iron failure increases from 75-80 to 90-92%.

Claims (1)

METHOD FOR RESTORING IRON ORES IN STOVES OF A STAGE-WEIGHED LAYER, including the supply of dispersed ore and solid ι. fuel, drying, magnetizing roasting · subsequent re-restoration, regulation of the size of the pieces of solid fuel burned in the volume of the furnace and its supply to the re-recovery chamber, which is due to the fact that. in order to improve the quality of the finished: products and increase productivity, the size of the pieces supplied together with the fuel material at a content of 1.5-2.5%. volatile, set equal to 0.5-2.0 mm ,, and, with an increase in volatility for every 10% in excess of 2.5 * "the size of the pieces is increased by 40-60%. in m>>