SU1184832A1 - Method of producing lime - Google Patents

Abstract

A METHOD FOR OBTAINING LIME by igniting the charge and calcining limestone with a gas stream suction through a layer of material, characterized in that, in order to improve the quality of lime, reduce fuel consumption and loss of raw materials, first 40-80% of the required heat is supplied to the layer, and then, for a time equal to 0.05-0.35 of the total firing time, air is introduced into the layer, after which the remaining 20-60% of heat is supplied.

Description

The invention relates to the production of lime, mainly for the metallurgical limit of iron ore.

The purpose of the invention is to improve the quality of lime, reducing fuel consumption and loss of raw materials.

The essence of the method is as follows.

The two-stage ignition of the charge, in contrast to the additional heating, is not intended for supplying from outside to the near part of the layer of additional heat, but for optimizing the ignition mode. In this case, with the furnace gases, the amount of heat that can be supplied to the layer is not greater than with the usual one-stage ignition. The absence of a zone of CO formation due to the reaction of the interaction of the COj of the mountain gases with the charge carbon and its slow burnout with a reduced content of free oxygen makes it possible to effectively use carbon in the near part of the layer for calcining limestone. Intensive burnout occurs when air flows between stages into the layer of atmospheric air. The second stage of ignition is carried out purposefully during the period when the air begins to exert a cooling effect. The effect on the layer and a decrease in the temperature of the heat wave in the middle part is planned. In addition, due to the second stage of ignition without additional external heat supply, the period of burning of solid fuel in the near part of the bed is increased. Improving the temperature-firing mode of firing and eliminating the decrease in temperature in the middle part of the layer reduces the consumption of solid fuel into the charge, which has a positive effect on the firing of the furthest part. No accumulation of heat is observed in it. The proposed ignition technology provides almost the same calcining conditions for limestone in the entire volume of the layer. In all its parts, the maximum temperature is

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1100-1150 seconds, and their residence time at dissociation temperatures limestone 4-A, 5 min. In addition, with this technology, all 5 drawbacks that are present with additional heating of the layer are eliminated, including the formation of a carbonate film on lime pieces.

To ignite solid fuels

 In the near part of the course of the gas flow, the layer must be fed at least 40% of the total heat consumption of the charge ignition. Then it turns out that the maximum consumption

5, the heat to the second ignition stage is 60%. The increase in heat consumption for the first ignition stage by more than 80% leads to the fact that, according to the indicators, the lime burning process approaches the typical one-stage ignition. From this it follows that the minimum heat consumption for the second ignition stage is 20%. For the sake of

5, the efficiency of using solid fuel in the near part of the layer, the gap with the supply of atmospheric air between the stages should not be less than 0.05 of the total firing time. An increase of more than 0.35 leads to separation of the main heat wave, and the second ignition stage has almost no effect on the value of the maximum temperatures in the bed.

5 In general, the proposed method provides for improving the quality of lime, reducing fuel consumption and loss of raw materials, as well as increasing the productivity of the aggregates.

In ferrous metallurgy, the efficiency, including the economic, of the use of lime is determined by the improvement of the indices of the main technological processes. Entering active lime instead of lime to the agglomerate ensures a reduction in fuel consumption and loss of raw materials, increasing the productivity of sintering machines and sinter quality. Reducing the dust content of the exhaust gases reduces the abrasive wear of equipment, such as the rotor of the exhauster and the grate. Uniformity of quality

5 lime and increased content

CaOflKT in the charge leads to a decrease in the variation of the chemical composition of the agglomerate.

Conducted laboratory tests of the proposed method.

Limestone calcination indicators were compared with one-stage ignition, additional heating (known methods) and two-stage ignition (proposed method),

During the experiments, the optimal consumption of gaseous and solid fuels for lime burning, the degree of lime burning, the loss of raw materials and the capacity of the installation were determined. Limestone is burned at a layer height of 00 mm and a vacuum under the grate of 1000 Pa.

The results of the experiments are given in table. one.

As follows from the data table. 1, in comparison with the known methods, proposed at the two-stage ignition of the layer provides an improvement in the calcination of limestone within the claimed limits of the process parameters. Optimization of ignition of the charge has a positive effect on temperature and thermal conditions. Calcification of limestone in the volume of the layer practically takes place under the same more favorable conditions. The shortage of heat in the near and its excess in the distant part of the layer is excluded. Due to a significant increase in the efficiency of use of solid fuels, it is possible to reduce the consumption of not only its fuel, but also of a fuel like fuel. Stabilization of the process at the same time allows to increase the degree of calcination of lime, reduce the loss of raw materials and increase plant productivity.

The economic efficiency of using the proposed method under the conditions of the sintering plant is determined by the improvement of sinter production. Therefore, laboratory sintering of agglomeration

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when the lime was introduced into it, the flow rate and degree of burning corresponded to the ignition technologies of the layer indicated in Table. 1. Experiments 5 were carried out at a height of the sintered batch of the charge equal to 300 mm and a vacuum under the installation unit of 8000 Pa. In the course of the experiments, the specific fuel consumption to the charge, 10 the plant capacity and the variability of the chemical composition of the agglomerate were determined. His sample was taken for testing in a drum according to GOST 15137-77. A class of more than 5 mm 15 in this sample was judged on the content of fines in a suitable sinter, and on a class less than 0.5 mm - based on the loss of raw materials and equipment durability. The results of the experiments are given in Table 20. 2

From the data table. 2 it follows that the replacement of lime with lime in the sintering mixture ensures an improvement in the sintering of its sintering: 25 the fuel consumption and raw material losses are reduced, the specific productivity of the plant and the quality of the sinter are affected. Reducing the dust content of waste gases reduces abrasive equipment wear, including the grate and the rotor of the exhauster.

The use of the proposed method for obtaining lime, taking into account the sintering conversion, ensures a reduction in fuel consumption per

1.3-5.0%; Increase plant productivity by 3–9% J Reduce raw material losses by 0.2–0.7%; reduction of fines content in the sinter on

1.2-2.1%; reduction of variability

chemical composition of agglomerate: by iron content by 0.04-0.09%, by basicity by 0.01-0.03 abs. units; increase equipment durability,

including grates and rotor of the exhauster.

Table 1

Table 2

Claims (1)

METHOD FOR PRODUCING LIME by igniting a mixture and calcining limestone with a suction of a gas stream through a layer of material, characterized in that, in order to improve lime quality, reduce fuel consumption and loss of raw materials, 40-80% of the required heat is first supplied to the layer, and then during time equal to 0.05-0.35 of the total firing time, air is supplied to the layer, after which the remaining 20-60% of heat is supplied. 00. KZ