RU2488053C2 - Method of annealing fine-grained material - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: proposed method comprises preliminary fluidisation and subsequent annealing in furnace. Said furnace comprises heating chamber with gas-distribution grate provided with feeder and communicated with sanitary cyclone, annealing chamber with fuel burners and overflow device inside cylindrical cavity wherefrom extends hot cyclone, guide baffle to separate material load zone from discharge zone, annular gas-distribution grate with shaped vanes, and cooling chamber with gas-distribution grate furnished with aid duct. Note here that fuel burners are arranged at different height with uniform alternation of their height in the range of fluidised layer thickness. Fuel burners may be provided with tangential inlet for, at least, one of fuel components. Spray maximum diameter of said burners is made approximately equal to fluidised bed layer thickness. Note here that its length makes about fluidised bed layer width.

EFFECT: uniform annealing

3 cl, 5 dwg

Description

The invention relates to the field of firing of fine-grained materials, in particular, to fluidized bed furnaces and methods for firing fluidized materials in them.

A known method of firing fine-grained material using a furnace for firing fine-grained material in a fluidized bed containing a heating chamber, equipped with a feeder and connected to a sanitary cyclone, a firing chamber having fuel burners and a transfer device inside a cylindrical cavity from which a hot cyclone is installed, and a cooling chamber equipped with an air duct. The cooling, firing and heating chambers are equipped with gas distribution grills (Aut. St. USSR No. 469037, IPC: F27B 15/10).

The disadvantages of this method are the uneven firing of the material due to its disordered movement in the annular firing chamber and significant hydraulic resistance of the furnace.

A known furnace for firing fine-grained material in a fluidized bed, comprising a heating chamber with a gas distribution grid, equipped with a feeder and connected to a sanitary cyclone, a calcination chamber with a gas distribution grid, having fuel burners and a transfer device inside a cylindrical cavity from which a hot cyclone is installed, a cooling chamber with gas distribution grill equipped with an air duct, while the annular gas distribution grill of the firing chamber is made with thin profile blades and a guide wall separating the material receipt zone from the unloading zone (RF patent No. 1145228, IPC: F27B 15/10 - prototype).

The specified furnace operates as follows.

The material to be calcined through the feeder enters the heating chamber, from where, after heating and drying, it passes through the transfer device to the burning chamber, into the material supply zone, where it is fluidized, and begins to move along the annular grating with thin profile vanes due to the supply of air from the cooling chamber having vertical and horizontal components of speed. The fuel-air mixture is fed into the firing chamber through the burners and burned in the fluidized bed of the fired material, which moves along the grate along the entire annular section to the discharge guide bar. Since the input and output of the fired material are spaced, its particles have the same residence time in the chamber and are fired, sequentially crossing the zones of action of the burners. Unloading of fine-grained material is carried out not only because of the fluidity of the fluidized bed, but also forcedly, under the influence of inclined jets of gases, providing directional movement of particles. This solution allows firing even with sufficiently thin fluidized beds, which also improves the quality of heat treatment of the material and reduces the hydraulic resistance of the furnace.

The disadvantages of the known device and the firing method used in it are the uneven firing of the material due to its disordered movement in the annular firing chamber and significant hydraulic resistance of the furnace.

The objective of the invention is to remedy these disadvantages and to create a method of firing fine-grained particulate material in a fluidized-bed furnace, the use of which will ensure the required irregularity of firing of dispersed materials while increasing the productivity of the furnace and improving the conditions for burning fuel.

The solution to this problem is achieved by the fact that in the proposed method of firing fine-grained material, which consists in its preliminary fluidization and subsequent firing in a furnace containing a heating chamber with a gas distribution grid, equipped with a feeder and connected to a sanitary cyclone, a calcination chamber with a gas distribution grid having fuel burners and a transfer device inside the cylindrical cavity from which the hot cyclone is mounted, a cooling chamber with a gas distribution grill, equipped with the duct, while the annular gas distribution grid of the firing chamber is performed with thin profile vanes and a guide wall separating the material entry zone from the discharge zone, according to the invention, fuel burners are arranged at different heights with uniform rotation of heights within the thickness of the bed of fluidized material, while the axes are directed at different angles to the longitudinal axis of the furnace.

In an application, the fuel burners are configured to tangentially introduce at least one of the fuel components.

In an application, the maximum diameter of the spray jet of these fuel burners is approximately equal to the thickness of the bed of fluidized material, while its length is approximately equal to the width of the bed of fluidized material.

The maximum diameter of the spray torch of these fuel burners is chosen to be approximately equal to the thickness of the bed of fluidized material, on the assumption that its further increase will lead to ineffective mixing of the layer of fine-grained fluidized material, since the part of the fuel burner flame in which the products of combustion have a maximum linear velocity will extend beyond the bed of the fluidized material. When reducing the diameter of the flame below the specified value, the flame of the combustion products will capture part of the bed of fluidized material, which will lead to a deterioration in the mixing efficiency.

The spray torch length of these fuel burners was chosen to be approximately equal to the width of the bed of fluidized material, based on the fact that with a further increase in it, the flow of combustion products will flow to the central parts of the furnace, which can lead to burnout and require additional cooling, and if it decreases, the torch combustion products will capture only a part of the bed of fluidized material, which will lead to a deterioration in mixing efficiency.

The invention is illustrated by drawings, where figure 1 shows a General view of the furnace; figure 2 is a transverse section of the septum; figure 3 is a top view of the annular lattice; figure 4 is a side view of the annular lattice, figure 5 is a General view of the burner.

The proposed method can be implemented, for example, using a furnace containing a heating chamber 1, equipped with a feeder 2 and connected to a sanitary cyclone 3, a firing chamber 4, with fuel burners 5 and a transfer device 6, inside of a cylindrical cavity 7 of which a hot cyclone 8 is installed, a cooling chamber 9 provided with an air duct 10. The heating and cooling chambers 9 are equipped with gas distribution grilles 11. The firing chamber 4 is equipped with an annular grill 12 with thin profile vanes and a guide wall 13. The front profile grill 12 contains inner 14 and outer 15 retaining rims, profile blades located between them 16. To prevent material dips, the grill is covered on top with a metal heat-resistant mesh 17. In the fuel burner 5, one of the fuel components, for example, gas, is supplied to the mixing chamber 18 burners through tangential entry 19.

The proposed method is implemented as follows.

The calcined material through the feeder 2 is fed into the heating chamber 1, from where, after heating and drying, it is fed through the transfer device 6 to the calcining chamber 4, into the material supply zone, where the calcined material is fluidized, and they begin to move along the annular lattice with thin profile vanes by feeding from the cooling chamber 9 of air having both vertical and horizontal velocity components.

The air-fuel mixture is fed into the firing chamber 4 through the burners 5 and burned in a fluidized bed of the fired material, which is moved along the grate along the entire annular section to the guide wall 13, to the discharge zone. Due to the fact that the fuel burners are located at different heights with a uniform alternation of heights within the thickness of the bed of fluidized material, and their axes are directed at different angles to the longitudinal axis of the furnace, there is an additional intensive movement of the particles of the calcined dispersed material over the thickness of the layer, which leads to to improve particle firing conditions and reduce firing unevenness

In an embodiment, the fuel is fed into the mixing chamber 18 of the burner 5 through a tangential inlet 19. The fuel flow is twisted in the specified chamber and enters the firing chamber, into the bed of fluidized calcined material, in the form of a rotating cone. The rotating cone of the fuel burner captures particles of the calcined material located in the bed of fluidized material, tells them the vertical, horizontal velocity components and centripetal acceleration, which leads to the intensification of the movement of particles of the calcined material inside the layer, and, therefore, their more uniform burning. In addition, the use of the tangential input of one of the fuel components will significantly reduce the length of the flame of the burner, and increase the efficiency of the burner, which, in turn, will make it possible to reduce the radial dimensions of the furnace.

Since the input and output of the fired material are spaced, its particles have the same residence time in the chamber 4 and undergo uniform firing, sequentially crossing the zones of action of the burners. Unloading of fine-grained material is carried out not only because of the fluidity of the fluidized bed, but also forcedly, under the influence of inclined jets of gases, providing directional movement of particles, which increases the productivity of the furnace, i.e. the amount of material burned per unit time. This allows firing even with sufficiently thin fluidized beds, which also improves the quality of heat treatment of the material and reduces the hydraulic resistance of the furnace, since, in addition to the possibility of operating the furnace on thin layers, the profile gas distribution grid 12 has a large live section, and, therefore, a small hydraulic resistance.

The productivity of the furnace can be regulated by changing the speed of the blast.

Radial flat jets of air leaving the annular lattice with thin profile vanes at an angle relative to its horizontal plane provide, in addition to moving fine granular material, better combustion of the air-fuel mixture by lengthening the trajectory of the movement of fuel particles in its combustion zone.

Then, through the transfer device 6, the calcined material is fed into the cooling chamber 9 and, after partial cooling, is removed from the furnace. Air is supplied to the cooling chamber 9 through the duct 10, which, by fluidizing the material to be cooled, takes part of its heat and, when heated, flows countercurrently to the solid material through the annular grill 12 into the firing chamber 4, acquiring horizontal blades around the profile blades 16, and vertical components of their speed.

The resulting flue gases with dust are sent to a hot cyclone 8 and, partially freeing them of dust in it, are fed through a gas distribution grid 11 to the heating chamber 1, where the material fed to the firing is heated. Dusty flue gases from the heating chamber D are discharged into the sanitary cyclone 3 and, after partial cleaning, are sent to a fine cleaning system (not shown), or emitted into the atmosphere if the relevant sanitary standards for the degree of flue gas treatment are achieved. Dust from cyclones 8 and 3 is removed from the system or sent for additional firing to firing chamber 4, depending on the technological features of firing of specific materials.

The use of the invention will reduce the unevenness of firing of the material, increase the productivity of the furnace and improve the quality of firing of fine-grained material due to the directional movement of particles of the fluidized bed in all directions along the entire annular section of the firing chamber and exclude re-firing.

Claims (3)

1. A method of firing fine-grained material, including preliminary fluidization and subsequent firing of the material in a furnace containing a heating chamber with a gas distribution grid, equipped with a feeder and connected to a sanitary cyclone, a firing chamber having fuel burners and a transfer device inside a cylindrical cavity from which a hot cyclone is installed , a guide baffle separating the material entry zone from its discharge zone, and an annular gas distribution grill with thin profile vanes and a cooling chamber with a gas distribution grille fitted duct, characterized in that the fuel burner positioned at different heights interleaved with uniform heights within the thickness of the fluidized bed material. 2. The method of firing fine-grained material according to claim 1, characterized in that the fuel burners are performed with the tangential introduction of at least one of the fuel components. 3. The method of firing fine-grained material according to claim 1, characterized in that the fuel burners perform with a maximum diameter of the spray jet, approximately equal to the thickness of the layer of fluidized material, while its length is approximately equal to the width of the layer of fluidized material.

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