SU837953A1 - Method of limestone calcining - Google Patents

Description

(54) METHOD OF FIRE LIMESTONE

The invention relates to the production of lime and can be used in the metallurgical, chemical industry / industry x and the building materials industry. A method of calcining limestone by preheating, unburnt material in an isometric tank and cooling the finished product 1 is known. The disadvantage of the method lies in the fact that from the burning zone the material enters an isometric bunker, where it is kept for 30-60 minutes. Due to the physical heat of lime during this time, the process of dissociation of the unfired part of the material takes place. The released carbon dioxide gas fills the interparticle volume and creates a partial pressure of carbon dioxide in the gas atmosphere of the bunker, approximately equal to 0.1 MPa. The dissociation temperature of lime in these conditions is 900–925 s. In the burning zone, the gas atmosphere contains 30–40% carbon dioxide, which ensures a dissociation temperature of 820–840 s. This leads to an additional expenditure of heat to heat the unburned limestone in an amount proportional to the difference in dissociation temperatures in the isothermal bunker in the burning zone, which reduces the efficiency of isothermal holding. The purpose of the invention is to reduce heat consumption. This goal is achieved in that according to the method of calcining limestone by heating, holding the underburned material in an isothermal bunker and cooling the finished product, the air selected after cooling the finished product is cooled. The supply to the isometric air bin heated with lime in the cooling zone reduces the partial pressure of the carbon dioxide, and in the isothermal bunker it reduces the dissociation temperature of lime contained in lime, which prevents the heat from being spent on additional heating of lime and, therefore, increases the proportion of heat going to decomposition limestone. The amount of air.

which is required to enter into the isometric bunker, is determined by the degree of roasting of the glaterial in the roasting zone of the kiln and the average temperature of the lime. These two values determine the amount of limestone decomposing in the bunker and, therefore, the volume of carbon dioxide emitted. Further calculation to determine the amount of injected air is reduced to solving a balance, a clear equation of the gaseous medium. The flow of air into the isometric bunker, taken after cooling the finished product, reduces the cost of heat to heat it up to the average temperature of lime and increases the thermal efficiency of the process.

The proposed method can be carried out in known lime kilns, for example, in rotary kilns, the schematic diagram of which is shown in the drawing.

The kiln complex includes a limestone preheater 1, an isothermal bunker kiln 3, and a lime cooler 4. Isothermal hopper 3 is connected to lime cooler 4 by pipeline 5, on which the regulator and air flow meter are installed (not shown in the drawing).

The method is carried out as follows.

The chemical composition,% CaCO3 96, MdSOz 2, others-2, is known to be loaded into heater 1, where it is heated and partially dissociated due to the physical heat of the combustion products coming from furnace 2. Heated and partially decarbonated lime are fed to furnace 2, where it dissociates, for example, by 92%. To carry out the process, the fuel and air, preheated by the physical heat of lime in the cooler 4, are supplied to the furnace. The product discharged from the furnace containing 0.1274 kg of lime in 1 kg of products enters the isothermal bunker 3,

where it is kept for 45 minutes. During this period of time, heat is transferred from superheated lime dissociation temperature to lime. In order to reduce the dissociation temperature of lime in an isothermal hopper 3, air is supplied in an amount of 0.08233 kg per 1 product selected after cooling the finished product. This ensures a reduction in the partial pressure of carbon dioxide in the isothermal bunker 3 to 0.02 MPL. and dissociation temperature up to. Under these conditions, in the bunker it decomposes, taking into account the cost of heat for heating the air to the temperature of incoming lime and heat loss to the environment, 0.1293 kg of lime per 1 kg of product, i.e. the limestone present in the product will be 100% pure. In the implementation of the method without introducing air, it will dissociate 65% of I have, right. in limestone product. Improving the quality of lime as a result of implementing the proposed method will ensure fuel economy in the firing process by 3-4% and improve the technical and economic indicators of the process in which this lime is used, for example, a reduction in lime consumption in converter production.

Forg / 1ula inventions

The method of calcining limestone by heating, holding the underexposed material in an isothermal bunker and cooling the finished product, characterized in that, in order to reduce heat consumption, the air selected after cooling the finished product is reduced.

Sources of information taken into account in the examination

l, Pi t and Bigagu 1975, C 7, 5Q No. 11, p 90-92.

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Claims (1)

Claim The method of burning limestone by heating, holding the unfinished material in an isothermal bunker and cooling the finished product, characterized in that, in order to reduce heat consumption, the air selected after cooling the finished product is fed to the bunker.