RU198165U1 - RECTOR INDUCTION FURNACE - Google Patents

Abstract

The invention relates to continuous furnaces for the thermal treatment of finely dispersed materials or suspensions, viscous liquids under a controlled gas atmosphere and heating temperature in continuous operation and constant mixing of the material. The continuous translational movement and mixing of the working material is carried out using rotating components in the furnace. Loading and unloading mechanisms ensure constant maintenance of the internal atmosphere and the thickness of the calcined material layer. Optimization of the retort geometry together with the induction heating method can significantly reduce weight and dimensions, ensure the continuity of the process while maintaining the given performance, provide high automation of the process, improve and expand the conditions of production, operation and maintenance. Also, modifications are disclosed when there is no need to maintain the internal atmosphere and when necessary the inclination of the axes of rotation of the retort with respect to the horizon.

Description

The utility model relates to continuous furnaces for the thermal treatment of finely dispersed materials or suspensions, viscous liquids under a controlled gas atmosphere and heating temperature in continuous operation and constant mixing of the material.

The implementation of continuous translational motion and mixing of the working material is carried out using rotating components in furnaces.

Rotary kilns are known in which the incoming movement and mixing is realized using screws arranged coaxially with the main pipe (RU 132073 U1 publ. 09/10/2013). The main disadvantage of large screws is the sticking of the material and high thermal deformation, which results in biting and frequent stops for maintenance of the unit. These shortcomings are deprived of a system with an misaligned arrangement of screws (RU 2608155 C1 publ. January 16, 2017) and a unit with a rotating drum-type tube with direct heating of a gas burner (RU 2657251 C2 publ. 06/09/2018).

Also known installation of indirect heating with a solid heat carrier, pre-heated by a gas heater with a rotating pipe (RU 2618585 C2 publ. 05/04/2017). The main disadvantage of this design is the complexity and high cost of maintenance.

In the above systems, the material is heated by gas burners directly inside the pipe, or by external resistance electric heaters, which have a limited heating rate and are prone to intense oxidation at high temperatures and aggressive environments.

At the same time, convective and radiation heating methods are characterized by inertness and relatively low productivity. This disadvantage is deprived of the induction heating method presented in RU 2070308 C1 publ. 12/10/1996 g, while this device has the above disadvantages inherent in large screws.

Closest to the proposed utility model in technical essence is a device for heating bulk metal particles (RU 33118 U1 publ. 10.10.2003), comprising a heating device in the form of a multi-turn cylindrical inductor, a smooth-walled drum mounted coaxially inside the heating device and resting on rollers, drum rotation drive, loading and unloading mechanisms.

A disadvantage of the known device is the lack of tightness and a controlled gas outlet, as well as the uneven distribution of the working material in the pipe in height. Also, the proposed direct method of heating a metal backfill with an electromagnetic field limits the use of the installation for heating non-conductive materials.

The problem solved by the utility model is to increase the heating productivity, increase the period of continuous operation of the furnace and provide an internal isolated atmosphere in a retort with a controlled gas flow.

The problem is achieved in that in an induction furnace with a retort containing a heating device made in the form of a multi-turn cylindrical inductor, a smooth-walled drum (pipe) mounted coaxially inside the heating device, supported by rollers mounted on a frame, a drum rotation drive, loading mechanisms and unloading, characterized in that coaxially to the inductor on the retort (pipe), thermal insulation is fixed throughout the hot zone, the loading mechanism is made in the form of a screw, the end flanges have thresholds and a gas exhaust system.

In FIG. 1 schematically shows the proposed electric rotary kiln with a retort tube. In FIG. Figure 2 shows the dependence of the pipe length L on the inner radius of the pipe R at various capacities ( a ) and the dependence of the external surface area (heat loss) on R, subject to the R / L ratio (b). In FIG. 3 schematically shows the proposed induction furnace with a retort without unloading mechanism with the possibility of rotation.

An induction furnace with a retort includes a retort (tube) 1 mounted coaxially with a multi-turn cylindrical inductor 2, which in combination are a heating device. The pipe is insulated from the inductor by thermal insulation 3 throughout the hot zone. The end flanges 4 have openings for connecting the gas outlet pipe 5, a mechanical transmission 6 for connecting the rotational drive of the furnace and a support disk 7 for mounting on rollers 8 mounted on the frame 9. The loading mechanism 10 has a screw 11 inside, on which a separate gear 12 is installed for independent connection auger drive. The unloading mechanism 13 consists of a threshold 14, a discharge opening 15 and a hatch 16 with a closing spring 17. Also, the unloading mechanism can be made in the form of a pipe 18. The frame can be additionally equipped with hinges 19 for connection with the supporting frame 20.

Induction furnace with a retort works as follows. The working material is fed into the loading mechanism 10 with a rotating screw 11. In the retort (pipe) 1, made of smooth-walled heat-resistant steel, heat is generated by the current induced from it from the alternating electromagnetic field of the multi-turn cylindrical inductor 2. Rotating, the retort distributes the material uniformly along the length. With the passage of the hot zone provided by thermal insulation 3, the material is uniformly heated and releases combustion products that fill the atmosphere of the retort. After threshold 14, the material enters the unloading chamber 13, which contains an opening in the center of the flange with a gas outlet pipe 5 installed in it. The waste material is discharged every pipe circulation period when the discharge opening 15 is in the lower position and the hatch 16 opens. Periodically discharged part of the material corresponds to the continuously flowing flow from the auger side.

The auger of the loading mechanism ensures a tight loading of the material, and a variable-opening hatch ensures its tight discharge. Thus, an isolated atmosphere is created inside the pipe, the flow rate of which is regulated by an external gas control system (not shown in the figure).

The threshold 14, installed inside the unloading mechanism 13 and which is the flange of the pipe 1, provides constant maintenance of the thickness of the layer of calcined material. What is necessary for the reproduction of reactions requiring heating and accompanied by the release of volatile products. These reactions require certain technological parameters for their progress, such as the thickness of the layer of the calcined material, the time spent in the calcination zone, the productivity of the installation.

To determine the optimal geometry of the retort pipe, providing the required performance, the relationship of technological parameters with the dimensions of the pipe was established. The trajectory of a unit of mass (particle) in a rotating pipe has a complex shape (truncated screw). However, the axial component of the particle velocity can be easily determined on the basis of a given material consumption (productivity) and the cross-sectional area of this stream. With sufficient accuracy, the shape of the flow cross section can be taken as a circle segment and its area can be calculated depending on the height h (layer thickness) and segment radius R (pipe inner radius):

where S _flow is the cross-sectional area of the working material stream;

R is the inner radius of the pipe (retort);

h - threshold height (layer thickness of the working material).

The ratio of the volumetric flow rate to the cross-sectional area determines the axial component of the velocity, and with the known axial velocity and the required time, the required pipe length can be determined. Using these ratios allows us to establish an unambiguous relationship between three parameters: productivity, internal radius and pipe length L. The criterion of optimality, for a given performance and technological parameters, is to achieve minimal heat loss in the system. The heat loss in the system is directly proportional to the external surface area of the pipe. Thus, the optimization task is:

where S of the _{surface of the cylinder} is the surface area of the pipe;

R is the inner radius of the pipe;

L is the length of the pipe.

For example, with the following technological requirements for calcining the material: the level of material (h) is 20 mm and the residence time in the hot zone is 20 minutes. From the above dependencies, the optimal retort geometry can be determined (FIG. 2). Graph a establishes the dependence of the R / L ratio and at a given flow rate allows you to select these sizes. From the point of view of reducing heat loss, it is necessary to set the minimum possible radius R due to an increase in L (traffic b).

The optimization of the retort geometry together with the induction heating method can significantly reduce the overall dimensions, ensure the continuity of the process while maintaining the given performance, provide high automation of the process, improve and expand the conditions of production, operation and maintenance.

In the absence of the need to maintain the internal atmosphere in the retort pipe, the unloading mechanism is performed in the form of a side pipe flange with a threshold 13 and a pipe of a smaller diameter welded onto it to unload the material 18.

It is also possible to tilt the frame 9 and the axes of rotation of the retort to an arbitrary angle from -14 to +14 degrees with respect to the horizon, due to the installation of hinges 19 on the frame, connected to an additional supporting frame 20.

Claims (1)

An induction furnace for processing finely dispersed materials, comprising a heating device made in the form of a multi-turn cylindrical inductor mounted coaxially inside a retort heating device with thermal insulation and a mechanical transmission for connecting a furnace rotation drive, furnace end flanges and support disks supported on rollers mounted on a frame, the loading mechanism and the unloading mechanism installed in the end flange of the furnace, characterized in that the thermal insulation is mounted on the retort so that it is isolated from the inductor throughout the hot zone, while the loading mechanism is made in the form of a screw, the unloading mechanism is made with an additional threshold and located behind it an unloading chamber with a hatch for discharging a part of the spent material, made with the possibility of connection with the exhaust pipe.

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