RU2327936C2 - Mine counterflow kiln for roasting limestone and dolomite (options) - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: mine for roasting a limestone and dolomite includes the heating, roasting and cooling zones, furnace extensions, lined mine and gas-distributing cruciform ceramic core with the roasting channels inside which have the holes for gas exit to the layer consisting of four arch-form piers which rest with one wing at the kiln mine lining and with another wing - at the central ceramic support. At that, two piers comprise the solid crossbar. In another option, the gas-distributing cruciform ceramic core consists of two crossbars one of which is solid and bears at the air-cooled bar, and another one bears at the first crossbar which has the grooves for piers.

EFFECT: mechanical durability and operating life of core are increased; capital and operating costs are reduced.

2 cl, 5 dwg

Description

The invention relates to shaft furnaces for calcining limestone and dolomite and can be used in metallurgy, soda and sugar industries, building materials industry.

Known shaft kilns for calcining limestone and dolomite (lump materials) of various capacities, operating on liquid and gaseous fuels, having a heating, firing and cooling zone, a metal casing, a lined shaft, peripheral, central, beam burners, gas distribution ceramic core.

By its principle, a counterflow shaft furnace is an almost ideal heat exchange unit - it has three technological zones: a calcination zone, where limestone decarbonization takes place in the temperature range of 870-1250 ° С and two utilization zones. In the cooling zone, the physical heat of the finished product is completely transferred to the air entering the combustion in the firing zone, and thus the process is completely returned. The heat of the gases leaving the firing zone is transferred to the cold limestone in the heating zone in the maximum possible amount. The inevitable heat loss in this process is the heat of the exhaust gases having a temperature of 150-300 ° C.

The gas-dynamic mode of operation of shaft furnaces is one of the most important factors of the firing technology that determines the design of the unit, burner devices and the development of heat and mass transfer processes in height and radius. The uniformity of gas distribution determines the quality of the physicothermal treatment of the charge layer and, ultimately, the uniformity of the composition and quality of the resulting product. The complexity of solving this problem is due to the high hydraulic resistance of the dense layer of the charge. It is known from practice that the distribution of gases over the furnace cross section is uneven. There are less gases in the center of the furnaces, which leads to a radial non-uniformity of the temperature field (in the middle of the firing zone, the temperature in the center can be lower than the temperature at the periphery by 400-500 ° C). Hence the burning of lime that passed through the central zones of such furnaces.

These drawbacks were avoided by constructing a cruciform ceramic core in the firing zone, inside which there are made fire channels with windows for the exit of gases into the limestone layer.

Closest to the invention in terms of technical nature and the achievement of a technical result is a shaft kiln for calcining limestone (patent of the Russian Federation No. 2194931, IPC 7 F27В 1/02, 2001) containing a ceramic core consisting of piers and a central column equipped with metal gas-cooled fixing beams. This furnace has a casing, a mine lining, remote furnaces, water-cooled support beams under the core, a central pillar, gas-cooled fixing beams resting on the furnace casing, walls, grooves in the shaft lining and the central column, into which walls are provided with gaps for thermal expansion.

The known device has several disadvantages.

- The presence of metal gas-cooled fixing beams that enter the core body (and piers and the central pillar) and weaken it due to various temperature expansions of the metal and ceramics.

- The presence of a central core pillar, complicating the entire structure, reducing its mechanical strength (piers by themselves, the central pillar by itself).

- The presence in the firing zone of water-cooled support beams under the core and, as a result, the loss of part of the heat in the firing zone of the furnace with cooling water, the need for a water cycle with chemical water treatment.

The task to which the technical solution is directed is to ensure the mechanical strength and durability of the core, and to reduce the capital and operating costs of the furnace.

The stated technical problem is achieved in that the cross-shaped ceramic gas distribution core (4), inside which the flame channels (6) are made with openings for the exit of gases into the layer (7), consists of four piers (5) made in the form of arches and supported by one wing to the lining of the furnace shaft (3), and another to the central ceramic support (10), which in turn stands on a metal air-cooled beam (8) located in the cooling zone and having windows (9) through which cooling air is supplied to space your stove. The two opposite walls are a monolithic cross, having grooves on each side, which include two other walls, each on its own side.

This design is easier to install, improves mechanical strength and ensures core longevity.

In addition, in the furnace cooling zone, the temperature field is stabilized by the use of a central fan air supply unit at a height of 2.5 m above the level of the unloading mechanism in combination with the introduction of air through the lime receiving hopper under the discharge grate.

Air supplied through the windows of the support beam (central fan air supply unit):

- firstly, it cools the support beam and allows you to abandon the water cycle with chemical water treatment;

- retains heat in the firing zone, carried away with cooling water;

- increases the life of the core, since the air supplied through the windows of the support beam reaches the core colder than the air entering through the lime receiving hopper, and in accordance with the so-called wall effect it washes the core and cools it, which reduces the temperature at which it is operated core, up to 1250 ° С. A comparative analysis of the proposed technical solution with the prototype shows that the claimed technical solution differs from the known for its structural implementation. Thus, the claimed technical solution meets the criterion of "novelty."

A comparative analysis of the proposed solution, not only with the prototype, but also with other technical solutions, did not reveal the essential features inherent in the proposed solution.

It follows that the claimed combination of significant differences provides the above technical result, which meets the criteria of the invention of "inventive step".

The proposed technical solution is illustrated by the attached drawings:

figure 1 shows the firing zone, section aa;

figure 2 shows the firing zone, section BB;

figure 3 shows the firing zone, section bb.

The shaft furnace has: a furnace cover 1, a furnace shaft 2, a furnace shaft lining 3, a gas distribution core 4, core walls 5, fire channels of the core 6, openings in the core for the exit of combustion products into the material layer 7, an air-cooled support beam with a central air supply unit for cooling 8, windows through which cooling air is supplied to the space of the furnace 9, the central ceramic support 10, remote furnaces 11, peripheral diffusion burners 12, air inlet fittings to the lime receiving hopper 13, unloading device 14.

Figure 4 and figure 5 shows a variant of a shaft furnace for calcining limestone and dolomite, characterized in that the furnace does not have a central ceramic support 10.

A shaft furnace equipped with a ceramic core operates as follows. Lime coming from the furnace heating zone is distributed by core into four sectors, where it is burned by the combustion products coming from the holes 7, walls 5 and peripheral burners 12. The temperature difference in the burning zone along the furnace section is 50-60 ° C, according to experimental data, which allows to achieve a degree of firing of 94-96%.

Technical and economic advantages of the proposed technical solutions are as follows:

- simplified core design;

- increased mechanical strength and durability of the core;

- reduced production costs of lime due to the refusal of water cooling of the support beam and the lack of a water cycle and a chemical water treatment section, as well as the conservation of heat in the firing zone carried away with cooling water.

From this we can conclude that the task to which the technical solution is directed is fulfilled, and the above result is obtained.

Information sources

1. Robert S. Boynton. Chemistry and technology of lime. M., Stroyizdat, 1972, pp. 90-102.

2. A.V. Monastyrev. Lime production. M., Higher School, 1975, p.132-158.

3. V.A. Krivandin, A.V. Egorov. Thermal work and design of iron and steel furnaces. M., Metallurgy, 1989, p. 48-49.

4. AT 401301 V, 08/26/1996.

5. RU No. 2194931 C2, 02/07/2001.

Claims (2)

1. A shaft kiln for calcining limestone, including heating, calcining and cooling zones, remote furnaces containing a lined shaft and a gas distribution ceramic core, characterized in that the gas distribution core is cross-shaped, inside which there are fire channels with holes for the exit of gases into the layers, of four piers made in the form of arches, one wing resting on the lining of the furnace shaft, and the other on the central ceramic support, which, in turn, stands on an air-cooled support bar a ke located in the cooling zone and having windows through which cooling air is supplied into the furnace space, the two walls being a monolithic spider having grooves, which include two other walls, each on its own side, and at the joints of the walls other and with the lining of the shaft of the furnace there are gaps for the possibility of free temperature deformation. 2. A shaft kiln for calcining limestone, including heating, calcining and cooling zones, remote furnaces containing a lined shaft and a gas distribution ceramic core, characterized in that the gas distribution ceramic core is cross-shaped, inside which there are fire channels with openings for the exit of gases into the layer, consists of two crosses, one of which is solid and rests on its base on an air-cooled beam located in the cooling zone and having windows through which cooling air is supplied to the space of the furnace, and the second consists of two piers made in the form of arches, one wing resting on the lining of the shaft of the furnace, and the other on the first cross, which has grooves, which include walls, each for its own part, and at the joints of the crosses with the lining the shaft of the furnace and in the joints of the piers with the first crosspiece there are gaps for possible temperature deformations.

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