SU958824A1 - Cyclone furnace for heat treatment of loose material - Google Patents

Description

(54) CYCLONE FURNACE FOR HEAT TREATMENT OF BULK MATERIAL

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The invention relates to devices for the thermochemical processing of finely divided minerals and can be used in the chemical and metallurgical industries, as well as in the production of building materials.

For heat treatment of bulk materials, rotary rotary kiln has been widely used.

A known installation, consisting of two-stage rotary kilns with independent supply of fuel and, heated air, drum heat-exchangers of the grate and cyclone types, cyclone dust collector. These rotary kilns provide a fairly uniform heat treatment of the material, have a sufficiently high performance, make it possible to apply complex mechanization and automation of the production process 1.

The disadvantage of the installation is a high specific fuel consumption and dust removal material, which necessitates the installation of bulky dust removal systems with cyclone separators.

In order to intensify the process of heat treatment of bulk materials, cyclone-type furnaces are now increasingly used.

5 A known cyclone chamber for heat treatment of a polydisperse material, comprising a cylindrical body with gas-burning devices, a central loading of the material being processed and a bottom outlet from the cyclone chamber of the dyestuff gases and the material being processed. In order to intensify heat transfer, protrusions are arranged on the inner surface of the chamber, arranged in several rows along the height of the body at an angle to the generatrix 5 in the direction of the twist of the gas flow 2.

However, the furnace requires the installation of additional separation equipment due to the fact that the flue gases have direct contact with the bulk material.

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The closest in technical essence and the achieved effect is a furnace for heat treatment of bulk material, containing a conical downwardly expanding working chamber with a central upwardly expanding chimney connected to the combustion chamber surrounding the working chamber. In order to intensify heat exchange and reduce dust removal, the upper part of the furnace chamber is connected to the lower part of the chimney with a channel equipped with a fuel-burning device, and the walls of the working chamber are solid 3. However, this furnace does not use all the possibilities to intensify the working process by increasing the level of convective heat exchange, which opens the application of swirling cyclone flows. In addition, the furnace has a large hydraulic resistance of the gas path, which predetermines a significant energy cost for the blast during its operation. The purpose of the invention is to increase the thermal efficiency of the furnace and reduce its hydraulic resistance. The goal is achieved by the fact that in a cyclone furnace for heat treatment of bulk material, there is a working conical downward-expanding working chamber with a central upward-expanding chimney connected to the combustion chamber surrounding the working chamber, the latter is installed eccentrically to the combustion chamber, in the lower part of the flue vent channels, and on the side surface of the combustion chamber are exhaust windows. FIG. 1 shows a furnace, vertical section; in fig. 2 - 2 sections aa and bb in fig. one; in fig. 3 and 4 are comparative data of the thermal efficiency and hydraulic resistance of the known and proposed furnace. The furnace contains a conical downwardly working chamber 1 with a central chimney 2 expanding upwards, a combustion chamber 3 with burners 4 arranged tangentially to its inner surface 4. The combustion chamber 3 is connected to exhaust chimney 2 by means of exhaust ports 5 and channels 6 and 7. chamber 1 is located eccentrically to the combustion chamber 3, channels 7 are tangential to the inner surface of the chimney 2. Chimney 2 in its lower part is equipped with a fuel-burning device 8. The furnace is equipped with a discharge device 9. The furnace works with eduyuschim way. Bulk material enters the working chamber formed by conical pipes 10 and 11. Pipes 10 and 11 isolate the processed material from the heating flue gas agent. Under the action of its own weight, the material is lowered from top to bottom at a speed determined by the discharge device 9. When the furnace is operating, the fuel and air are supplied in the required quantities to the burners 4. The resulting flue gases heat the material to be processed from the outside through the pipe 10. Through the exhaust ports 5 in the side surface of the chamber 3, they are diverted to the channels b, and then to the tangential channels 7, spinning the flue gases in the central chimney. Due to the eccentric arrangement of the working chamber, conditions are created for cutting off the flow from its outer surface. The tear-off - vortex nature of the flow wrap leads to a significant intensification of the process of heat transfer from the flue gases to the heated material through the external surface. The removal of heating gases from the combustion chamber through the exhaust windows allows a significant reduction in the hydraulic resistance of the combustion chamber. The twisting of the flue gases in the central chimney allows to intensify the heat exchange between the heating gases and the material being processed from the inside of the working chamber. FIG. 3 shows the dependence of heat transfer on the outer surface of the working chamber with its axisymmetric arrangement in the combustion chamber (line 1) and eccentric (line 2) on the device load in gas. The experiments were performed on models of the furnace, known and proposed design, with the same geometric dimensions and other equal conditions. FIG. 3 Nu etd / A is the Nusselt number, Re wd / S is the Reynolds number, where oL is the heat transfer coefficient; d is the average diameter of the working chamber; w is the gas velocity at the burner outlet; L and -, respectively, the coefficients of thermal conductivity and kinematic viscosity of gases at their temperature at the exit of the burners. The dependence of the hydraulic resistance on the gas load for both cases is shown in FIG. 4 (where w is the total coefficient of resistance of the combustion chamber, ARp is the differential pressure of the total pressure in the combustion chamber; the density of the gases at their temperature at the outlet of the burners). The designations are the same as in FIG. 3. The results obtained by the authors on the distribution of local heat transfer coefficients around the perimeter and middle over the side surface of the working chamber at various locations in the combustion chamber suggest that the eccentric location of the working chamber leads to a significant increase in the level of heat transfer due to its tear-off flow. As follows from the presented experimental data (Fig. 3 and Fig. 4). The proposed furnace design allows a 5–30% increase in heat transfer through the outer side surface of the working chamber and a 1.5–3.0-fold reduction in the hydraulic resistance of the combustion chamber due to the location of exhaust windows in its side surface.

Depending on the cross-sectional area of the tangential channels, the heat efficiency of a device with a swirling flow in a pipe is 6–9 times higher than in a pipe with an axial flow of gases. Thus, (even without taking into account the increase in the efficiency of the device due to the intensification of heat transfer along the inner side of the working chamber), the thermal efficiency coefficient is equal to

JNIU2.

T /.

and determining how many times the proposed furnace design is more effective than the known one, in the studied gas load range (Re range) is 1.8-3.5. In the above expression, the subscripts 1 and 2 refer respectively to the known and the furnace of the proposed design.

Claims (1)

1. Tsibin, I.P., et al. Start-up, adjustment, and heat engineering tests of furnaces and fireproof industry. M., Metallugi, 1978, p. 256. 2 USSR Author's Certificate No. 346563, cl. F 27 B 15/00, 1970. 3Awtor's certificate of the USSR No. 381854, cl. F 27 В 1/08, 1971 (prototype).