SU1204589A1 - Method of producing lime - Google Patents

Description

one

The invention relates to the production of lime, mainly the length of the metallurgical processing of iron ore.

The purpose of the invention is to reduce fuel consumption.

The essence of the method is as follows.

For calcining limestone, which is characterized by heat exchange at Re numbers 5–1000, the relationship between the heat transfer coefficient (oi) and the velocity (w) of air entering the layer is expressed by a power law:

y-)

those. Increasing the feed rate of the same air consumption by 2 times due to a corresponding reduction in the feeding period leads to a decrease in heat removal from pieces of material by 1.4 times, and with an increase in speed of 4 times - the heat removal decreases by 2 times, etc. " from the fact that, in the general case, for the periodic supply of atmospheric air to the layer of heat treatable material, the average heat transfer coefficient (“c.) while maintaining the total flow rate and period of the treatment, is equal to

W

W.

1-p

with"

 where, 06 ;,, w, t

w. and

P

At the same time, where - is the heat transfer coefficient, speed and period of uniform treatment of the layer of material with atmospheric air, respectively; P - respectively, the speed and time of the periodic air supply to the layer.

,

the time between the air feeds to the bed. Considering the fact that for this case Wg-Op Wf, T (equality of air flow in both modes),. it turns out ..

  P V „

Since To "cp. intermittent air supply to the layer provides less heat removal from pieces of heat treatable material.

In case of inequality of air flow with a uniform and period of 20458Ч2

It is necessary to observe its feeding into the layer.

.

 where- G, Gp - respectively consumption

air with a uniform and periodic feed it into the calcined layer of material.

However, when G about 1; The proposed method has advantages.

This is due to the fact that TC is always

ten

greater than one and the same cooling effect is achieved in both modes with different air flow rates and that is typical; i.e. according to the proposed method, without changing the heat removal, a larger amount of air can be supplied to the layer, which is necessary to intensify the process of burning solid fuel of the charge. The choice of parameters for the periodic supply of air to the layer makes it possible to optimize the temperature-thermal regime of calcining limestone and to achieve the same conditions throughout the entire volume of the layer. Particularly effective is the application of periodic maintenance during the burning of the proximal part of the layer. The removal of the cooling effect of atmospheric air during this period will lead to a noticeable decrease in the consumption of solid fuel in the charge. The resulting decrease in heat generation in the layer requires, to maintain the temperature level in the middle and distant parts of it, a periodic supply of air throughout the entire firing process. In general, the proposed method can be applied in separate periods and for

. total roasting time.

The peculiarity of the periodic air supply during the layered calcination of limestone is that it allows one to achieve full compliance

between the rate of burning solid

fuel and heat exchange in the layer. When choosing the firing mode, it is necessary to ensure the air filtration rate necessary for the intense burning of solid fuel, as well as the air filtration rate, which allows for a given exposure of limestone at the dissociation temperature zone. For the intense combustion of all grades of fuel, a higher filtration rate is required than for the dissociation of limestone. With the existing technology, the adjustment of the process is usually reduced to the selection of some average value of this speed: the fuel burns relatively low, but a high temperature zone is created in the layer, providing relatively good conditions for limestone burning. In addition, the correspondence between the dissociation of lime and the burning of solid fuels usually tends to be achieved by selecting its size and grade. For firing limestone of a class of 3-12 mm, coke breeze is usually used with a desired grain size of 3-6 mm. However, the screenings of a class less than 3 mm are not produced due to the high initial moisture content, and the supply of cheaper anthracite headquarters to the mine significantly worsens the process performance.

Periodic air supply to the layer can provide a strictly optimal filtration rate for intensive burning of solid fuel and due to the presence of exposure between the air supply — a strictly optimal limestone dissociation time. In this case, practically, the dependence of the indicators of the process of its roasting on the size and grade of solid fuel is completely excluded.

When determining the parameters of the periodic process management, it is necessary to proceed from the fact that during the supply of air in the layer, heat accumulates due to the burning of solid fuel, and during exposure it is consumed for dissociating lime with a decrease in the temperature level. With an air supply time of 90 seconds, complete accumulation of heat in it, i.e. subsequently, the temperature level of the process remains practically unchanged, and the lag time of the limestone pieces, due to the shortening of the period between air feeds, is unnecessarily reduced and the process performance deteriorates. In addition, an increase in the air supply period of more than 90 s, regardless of other parameters, including the delivery time, leads to the appearance of separate layers in the layer.

2045894

The sections fired according to standard technology and the process indices approach their values characteristic of a uniform air supply from the bed. At the indicated sites, during the period of air supply to the layer, after it reaches the maximum values, the temperature decreases below the temperature of dissociation of lime. With the correct selection of the firing mode, any decrease in the period of air supply to the layer less than 90 s intensifies the process. Depending on the complete accumulation of heat 15 in the combustion of solid fuel in the layer, the period of the delay between the atmospheric air supply is selected. A decrease in the ratio of the time of air supply and vyderzhki less than 0.8 at 2Q leads to a decrease in the temperature level in the layer to values that worsen the process performance. An increase in this ratio of more than 5 is characterized by an approximation of 25 liters of standard technology.

In general, intermittently supplying air to the calcining layer can reduce fuel consumption to the charge as well as increase the degree of calcination and lime production.

Improving the quality and consumption of lime in the sintering mixture provides for the intensification of its sintering. and allows to increase production and improve sinter quality, reduce raw material losses, fuel consumption, and increase equipment durability in sinter conversion.

Conducted laboratory tests

the proposed method. 40

The experiments were carried out with a uniform and periodic supply of atmospheric air into the lighted layer. The lime was burned in all the experiments in a layer 200 mm high. When the ratio of the time of supply of atmospheric air to the time of delivery by the proposed method is equal to and greater than 1.0, the rate of air filtration in

The 50 layer was chosen such that during each burning period the air flow rate of the typical technology was maintained. When this ratio is less than 1.0, the experiments were carried out at

The average value of the optimal rate of air filtration in the layer is independent of the absolute values of the periods of its supply and delivery.

thirty

35

45

In the course of the experiments, the rate of air filtration into the layer was measured using an anemometer and the consumption of solid fuel into the mixture was determined, as well as the degree of calcination of lime and the capacity of the installation.

The results of the experiments are given in the table.

From the data presented in the table, it follows that in order to achieve the purpose of the invention, the calcination of lime should be carried out with periodic supply of atmospheric air to the layer with an interval of not more than 90 seconds and the ratio of the time of air supply and the suspension between them equal to 0.8-5.

Enter lime, taking into account changes in its production and quality of the proposed method, in the sintering mixture, as shown by experienced spbka Order of 8581 Circulation 604 Subscription

VSH-SPI of the USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Branch PPP Patent, Uzhgorod, st. Project, 4

204589

nor, provides reduced consumption

fuel by 0.8-1.2 kg / ton of sinter, reduction of fines content less than 5 mm in the finished product by 5 0.9-1.4%, reduction of variability

the chemical composition of the sinter is 1.4-1.7 times and the loss of raw materials by 0.4-0.6%, an increase in the productivity of the installation by 12-15% and due to a decrease in

10 dust content of waste gases increases the equipment durability, in particular, the grate and the rotor of the exhauster.

The use of the proposed method of obtaining lime in comparison with the known method allows reducing fuel consumption in the production of lime by 1.99-3.41%; to increase the lime burning rate by 4.9-13.4%;

20 to improve the performance of roasting plants by 4-19%,

Claims (1)

- METHOD FOR PRODUCING LIME by igniting a mixture and calcining limestone with a supply to the atmospheric air layer, characterized in that, in order to reduce fuel consumption, the supply to the atmospheric air layer is carried out periodically with an interval of not more than 90 s with a ratio of the air supply time and the exposure time between them 0.8-5.