RU2677724C1 - Method of obtaining lime - Google Patents

Abstract

FIELD: construction.SUBSTANCE: invention relates to the construction industry and can be used in the production of lime by burning limestone in special kilns. Prepared and selected limestone from the bunker is fed to the chute of the vibrating conveyor, located horizontally inside the lined kiln, and is subjected to roasting. Limestone is moved in the burning zone at a speed of 400–800 mm/min. In the process of moving vibrating conveyor give oscillatory motion with an amplitude of 2–4 mm and a vibration frequency of 1,000–1,500 1/min. Heating and burning of limestone is carried out by a combined coolant: a catalytic heat generator and an infrared radiation source. Modes of movement of limestone are regulated depending on the size of the pieces of limestone. Gases released during the firing process are removed through the windows made in the lined kiln. Finished lime after firing is collected in a hopper.EFFECT: regulation of limestone burning processes and the use of an efficient source of thermal energy make it possible to produce high-quality lime using simple and economical methods using small-sized equipment.1 cl, 1 dwg

Description

The invention relates to the construction industry, and can be used in the production of lime by calcining limestone in special furnaces.

Known methods of calcining limestone are carried out due to heat during the combustion of fuel in rotary and shaft furnaces. The advantages of rotary kilns are the production of high-quality lime, the use of any type of fuel, high productivity, but, as a disadvantage, with large overall dimensions of the kilns. A known method of producing lime according to the patent for the invention RU 2348587, IPC С04В 2/12, publ. 03/10/2009, according to which the limestone is crushed and through coaxially located holes along the axis of rotation of the rotary drum of the mill, pulverized particles of crushed material are fed into the dust collector. Limestone and solid fuel are dosed by weight, screening out fuel fractions of less than 20 mm. The charge is loaded into a rotary kiln, where it is mixed with CO ₂ and calcined at 450-1000 ° C for 4-5 minutes. The main disadvantage of the methods for producing lime in rotary kilns is the large specific level of fuel consumption per ton of output. So, according to V. Buldikevich (“Energy-saving technologies for the production of lime from wet and loose chalk,” Building Materials magazine, No. 5 - 2012, pp. 11-13), 280-320 kg are spent on the production of 1 ton of lime in rotary kilns fuel equivalent. This is significantly more than when calcining limestone in shaft furnaces. For domestic raw materials with a moisture content of 25 to 30 percent, the average specific consumption of equivalent fuel is 180-200 kg per ton of lime.

In the production of lime in shaft kilns, limestone is loaded into a shaft kiln periodically or continuously from above. As the lime is unloaded, the material lowers down, and hot flue gases leak towards the material to be burned. By the nature of the processes occurring in the shaft furnace, there are zones of heating, firing and cooling. A known method of firing lump of limestone in a shaft furnace according to the patent for invention RU 2213918, IPC F27B 1/00, publ. 10/10/2003. Calcined limestone calcining in a shaft furnace includes heating, calcining limestone and cooling the resulting lime, carried out in countercurrent flow with the products of fuel combustion and air. At the lower and upper level of the fuel burning devices, gaseous fuel and an oxidizing gas are supplied for burning fuel, which use air at the upper level of the fuel burning devices. As an oxidizing gas for burning fuel at the lower level of fuel combustion devices located at a distance of 1.4-2.0 m from fuel combustion devices of the upper level, atmospheric air is used, and it is supplied in an amount corresponding to the value of the air flow coefficient α _lower equal to 0.2-0.15. The method provides a reduction in the specific consumption of equivalent fuel to 131-133 kg / t. However, the production of small amounts of lime or small stocks of raw materials at the construction site is not economically feasible in shaft kilns. Moreover, when calcining limestone in shaft furnaces, it is difficult to change the mode of its calcination.

Closest to the claimed method is a method of calcining bulk materials in a furnace according to the invention patent RU 2247288, IPC F27B 1/00, publ. 02/27/2005. The prepared raw material is fed through a loading device from above to the firing zone of a cylindrical lined body (lined furnace) and it is moved vertically from top to bottom along a hollow screw-shaped surface fixed to an axial tube inside the lined furnace.

The cavity of the helical surface performs the function of the heat channel, therefore, when moving the raw material on the helical surface, it simultaneously fires with the indicated helical surface. To prevent freezing of the material, it is subjected to vibration due to the vibration of the furnace, the base of which is mounted on vibrators. The material obtained during the firing process is discharged through a window made in the lower part of the lined furnace. The blasting of hot air with this method of firing the material occurs in a closed heat channel, the gases exit from the heat channel in the upper part of the furnace. This method of firing improves the quality of the calcined material, environmental performance, reduces specific fuel consumption. Compared with previous analogues, the dimensions of the furnace are also reduced. The disadvantage of the prototype is the low efficiency of heat transfer of a gas burner when heating bulk material. In addition, for the implementation of the method, a furnace of complex construction is required, which provides for the manufacture of a welded hollow helical surface, and for the vibration of an axial pipe with a helical surface and bulk material, the presence of powerful vibrators.

The technical problem solved by the invention is aimed at creating a simpler and more economical method that does not require bulky and complex equipment, which allows producing small amounts of lime and regulating the firing process to improve the quality of lime obtained.

To solve this problem, as in the prototype, the prepared raw material is fed into the firing zone of the lined furnace, it is subjected to vibration during the movement of the raw material in the firing zone, and lime obtained during the firing process is unloaded through a window made in the lower part of the lined furnace.

In contrast to the prototype according to the claimed method, the raw materials are fed and moved in the firing zone along a vibration conveyor located horizontally in the lower part of the lined furnace. Raw materials are moved to the firing zone at a speed of 400-800 mm / min with a vibration amplitude of 2-4 mm and a vibration frequency of 1000-1500 1 / min. The difference is also that the firing of raw materials is carried out by combined heating. For heating, a variable-power catalytic heat generator is used, which is fixed in the upper part of the lined furnace above the vibration conveyor, and an infrared radiation source fixed inside the lined furnace. Gases released during the firing process are removed through windows made in a lined furnace.

The drawing shows a device for implementing the proposed method. In the lower part of the lined furnace 1, a vibrating conveyor 2 is installed, onto which raw materials (limestone) are fed from the hopper 3. In the upper part of the lined furnace 1, a catalytic heat generator 4 with a mirror heat reflector 5 is fixed. The source of infrared radiation is not shown in the drawing. It can be fixed in any convenient place: side, top or bottom of the lined furnace. To remove the gases emitted during the firing process in the lined furnace 1, windows 6 and 7 are made. To collect the finished lime, a receiving hopper 8 is used.

The method is as follows.

Pre-prepared and selected limestone with a size of 20 to 50 mm from the hopper 3 is fed to the gutter of the vibration conveyor 2. A vibrating drive creates a disturbing force and transfers oscillating movements with an amplitude of 2-4 mm and a vibration frequency of 1000-1500 1 / min to the load-carrying organ (gutter) of the vibration conveyor. . In the firing zone, a catalytic heat generator 4 together with an infrared radiation source provide heating of limestone to a temperature of 980 ° -1200 ° C. The choice of grades of these coolants is carried out according to the condition of providing them with a total firing temperature of 980 ° -1200 ° C. Limestone is moved in the firing zone along the vibration conveyor 2 at a speed of 400-800 mm / min. The modes of movement of limestone, the amplitude and frequency of vibration, the firing temperature is regulated depending on the size of the pieces of limestone. The indicated values of the speed of the vibrating conveyor and vibration parameters were established experimentally. Experiments have shown that it is within these limits that the regulation of the lime burning mode ensures that it is fired sufficiently to produce high-quality lime. Gases emitted during limestone calcination are removed through windows 6, 7 made in the lined furnace 1. Finished lime, after calcination through the window made in the lower part of the lined furnace 1, is collected in a receiving hopper 8. Regulation of limestone calcining processes by changing oscillations and speed vibration conveyor and the use of an effective combined heat carrier (catalytic heat generator and infrared radiation source) can simplify the device itself to implement the inventive method in Wed knowledge of the prototype, and the very method of producing lime is made easier and more economical.

Claims (1)

A method of producing lime, according to which the prepared raw material is fed into the firing zone of the lined furnace, it is subjected to vibration during the movement of the raw material in the firing zone, and the lime obtained during the firing process is unloaded through a window made in the lower part of the lined furnace, characterized in that the raw material is fed to vibration conveyor located horizontally in the lower part of the lined furnace and move it in the firing zone along the vibration conveyor at a speed of 400-800 mm / min, with a vibration amplitude of 2-4 mm and a vibration frequency of 1000-1500 1 / m in, and the firing of raw materials is carried out by combined heating using a variable-power catalytic heat generator, which is fixed in the upper part of the lined furnace above the vibrating conveyor, and an infrared radiation source fixed inside the lined furnace, while the gases released during the firing process are removed through windows made in the lined ovens.

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