Vibration Furnace

Abstract

A vibration furnace for treating loose dusting and poorly transportable materials at a temperature of up to 500.degree.C, made according to the schematic diagram of a vertical vibration conveyor with a chute attached to supports of a vertical bearing pipe with the help of brackets mounted to be movable radially and insulated electrically from the supports of the vertical bearing pipe by means of insulators; said chute is connected in an electric circuit as a heater. The proposed vibration furnace may prove to be most advantageous in the food, drug, chemical and other industries for high-temperature processes of drying, roasting and heat-treating of dispersed loose dusting materials. Moreover, the proposed vibration furnace is suitable for use as a high-temperature chemical reactor for carrying out such processes where strict adherence to prescribed technological parameters is of utmost importance.

Description

BACKGROUND OF THE INVENTION

The present invention relates to the heat treatment of loose materials and more particularly to vertical-type conduction vibration furnaces.

The use of the herein-proposed vibration furnaces is exemplified by their utilization in the food, drug, chemical and other industries for high-temperature drying, roasting and heat-treating of dispersed free-flowing dusting materials.

Another potential application of the proposed vibration furnaces is their use as high-temperature chemical reactors for carrying out such processes wherein strict adherence to prescribed technological parameters is of utmost importance.

In developing the vibration furnaces the problems pertaining to their strength, mode of heat transfer to the material being treated, stable conveyance of materials whose properties are being changed in the course of heat treatment, and to throughput capacities of the furnaces must be solved.

Owing to specific features involved in the technology of heat the treatment of powdered dusting materials, the design of a vibration furnace shall suit additional requirements associated with air-tightness of a working zone and heat transfer to materials by conduction, and a reduction in the speed of gases removed from the furnace working zone.

In heat-treating powdered materials in a vibrating bed process efficiency is to a larger degree dependent on a working temperature and the length of time over which the material is held in the working zone.

In this connection heat treatment of powdered dusting materials is usually performed in vertical-type vibration furnaces based on the principle of vertical vibration conveyors.

Known in the art is a vertical-type vibration furnace made as a vertical bearing pipe with helical chutes fixed rigidly on the pipe and adapted to convey the material to be treated. In the bottom part of the vertical bearing pipe a vibrator of helical oscillations is fastened thereto. The entire oscillating part of the vibration furnace is mounted on springs and enclosed in a heat-insulating casing which is either a stationary cabinet or a shell vibrating together with the oscillating part of the vibration furnace.

As for a heat carrier, use may be made of hot air (see, for example, Author's Certificate of the USSR No. 314,985, Cl.F26 b 17/12, a vibrating drier "Xerotron," Switzerland-FRG, vertical vibrating driers manufactured by "Sinex," France), electrical spirals arranged either outside (see, for example, "Jost" vibrating driers, FRG) or inside of the vertical bearing pipe.

All the aforesaid types of vibration furnaces suffer from such major disadvantages as low concentration of heat energy on the heat-transferring surface of the chute, low efficiency owing to a low heat tranfer factor and the use of a principle of indirect heating for the chute, and a reduction in the stress-rupture strength of the vertical bearing pipe under the effect of high temperature.

In terms of their strength, the main units of the known vibration furnaces exposed in service to vibrations and high temperatures are found under most unfavorable conditions since the bearing and most heavily loaded vertical pipe are always arranged either in close proximity to the heater or in a most heated zone, being often heated to a much higher temperature than the heat-transferring conveying chute.

The above disadvantage results in a substantial decrease in all the strength and technological characteristics of the vibration furnace, such as its throughput capacity, permissible working temperature, furnace height and related limitations to the length of transportation and process duration.

Moreover, peculiar to the prior-art designs of the vibration furnaces is irregular heating of material being dried with all the ensuing serious technological problems involved in high quality treatment of most materials.

This explains various known improvements in design whose object was to reduce the effect of irregular heating, such as reduced width of the chute, the use of appliances for stirring the material being dried, an increase in the length of the chute ensuring adequate time for the drying of material being treated.

In addition, it is known that nichrome heaters used in most cases are unreliable in service and require frequent replacement.

The heating of the entire conveying column to a working temperature brings about considerable thermal stresses in the structural elements of the vibration furnaces with rigid attachment (usually by welding) of the conveying helical chute to the vertical bearing pipe, the stresses being attributable to irregular heat exchange and temperature gradients between the bearing vertical pipe and the helical chute. As shown by calculations, the vibration furnace with the helical chute connected rigidly the vertical bearing pipe is able to operate without failure at a temperature of not more than 200.degree.C.

The vertical-type vibration furnaces known in world practice operate at working temperatures not in excess of 250.degree.C.

Hence, the conceptual design of the vibration furnaces developed so far does not enable efficient utilization of the advantages concerned in the use of a vibrating bed for high-temperature processes involved in heat treatment of powdered dusting materials.

It is commonly known that conveying-technological setups are suitable only for transportation of materials not prone to sticking.

However in chemical technology the properties of materials to be treated in vibration furnaces are far from being ideal in terms of their vibrotransportability. Usually they constitute damp materials poorly transportable in their original state, with the material properties liable to vary in a permissible deviation range. Under these conditions the througput capacity of a vibration furnace depends in the first place on stability and the degree of filling the chute with materials.

Vertical vibration conveyors of the known designs intended for carrying material upwards along in a helical chute are usually fitted with loading devices made as an overhang branch pipe connected to the helical chute with the help of a pan with parallel walls and a radial axis of symmetry (see, for example, vertical vibration conveyors manufactured by "Schenk") or tangential to the chute (see, for example, vertical vibration conveyors of the "Jost" firm, FRG). Upon entering the loading device of a vertical screw conveyor, the material commences to circle under the effect of helical oscillations, i.e, each particle of the above material moves in a direction at right angles to the radius connecting it to a vertical conveyor axis. In this case the material loaded radially and tangentially upon coming into contact with the walls of the loading device is decelerated and collects impeding full and uniform charging of the conveying chute. This diminishes materially the throughput capacity of the vertical-type vibration furnaces, particularly in conveying materials with low free-flowing properties. In this case to avoid accumulation of material the loading device of a vertical vibration conveyor, whose layout is taken as the basis in designing a vibration furnace, is made as a tapered pan mated with the first coil of the helical chute and protruding beyond the limits of the conveying chute (see, for example, the "Sinex" catalogues, France, or a book by Slivakovsky A.O., Goncharevich I.E. "Vibration conveyors, feeders and auxiliary equipment" 1972, 223 pp.). The material circling along the tapered porting of the loading device pours gradually to an inside diameter to enter the helical chute.

A disadvantage of the above loading device lies in a limited possible range of application, i.e. only in conveyors with an internal bearing pipe, this being attributable to its large overall dimensions and to the arrangement of a tapered loading device in the zone of maximum stresses.

An attempt to reduce accumulation of material in the loading device resulted in the provision of a loading means with walls made as evolvent cylinder-shaped surfaces combining specific features of all the three known loading devices disclosed hereinbefore (see, for example, the device of the type disclosed in Author's Certificate of the USSR No. 194,631, Cl.81e 51, 49c, 30/01, 1967).

The above-described major types of the loading devices as well as other known designs do not meet completely contradictory requirements which, if satisfied, can ensure enhanced throughput capacities and more reliable design of vibration furnaces, i.e., preclude accumulation of material and provide a reduction in the passage of the loading device.

It is known that a vibrating bed featuring principal advantages of a gas fluidized bed resulting from an intense heat mass exchange is free from the main disadvantage-- dust carryover, a feature which enables its efficient use in many cases in treating dusting powdered materials. However, successful heat treatment of powdered materials in a vibrating bed with minimum dust carryover is possible only with properly organized ventilation. Usually heat treatment of powdered materials is accompanied by intense evolution of gaseous products removed by drawing ambient air through the working space of a vibration furnace, the carryover being in this case dependent on gas velocities in the furnace working space. A reduction in gas velocities is obtained by increasing the total passage of gas flues.

Known in the prior art are vibrating driers wherein a gaseous heat carrier is admitted into a working zone through a perforated vertical bearing pipe (see, for example, the "Xerotron" vibrating drier, Switzerland-FRG).

Gas flows moving with low speeds do not prevent the dust from being entrained and settled in gas flues, which hinders stable operation of the vibration furnace.

Also known is a method of vibrotransportation of damp sticky materials adhering in a damp state and losing this property in a dry state, said method being based on that prior to loading the starting damp sticky material onto a conveying chute, it is loaded with same material but slightly dried up to a degree when it stops adhering (see, for example, Author's Certificate of the USSR No. 299,426, 1971).

With the above method an up to 40-fold increase in the rate of material being conveyed can be obtained; it also makes it possible to reduce the dimensions of a vibration conveyor, to increase its throughput capacity and ensure stable operation.

The list of materials capable of adhering in a damp (initial) state and non-sticky in a dry (final) state is rather long, the use of the above described method in the vibration furnaces being therefore very efficient in terms of their versatility and an expansion in their range of application.

The vibration furnaces of the known design do not comprise appliances ensuring partial recycling, i.e., return of a fraction of the treated material into a zone proceeding to a material loading station.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome the above disadvantages.

Another object of the invention is the provision of a high-production vertical-type furnace for heat-treating at a temperature of up to 500.degree.C of powdered dusting materials poorly transportable along a vibrating surface in their initial state with the evolution of a large amount of gases.

Said objects are accomplished by a chute of a vibration furnace attached to supports of a vertical bearing pipe with the help of brackets movable radially, and insulated electrically from the supports of the vertical bearing pipe by means of insulators with the chute being connected in an electric circuit as a heater.

It is expedient that the brackets be secured to the supports of the vertical bearing pipe with the aid of spring-biased bolts displacing in conjunction with the brackets and the chute, which is made annular, along radial slots provided in the supports of the vertical bearing pipe.

It is desirable that at the place of arrangement of a loading device made as a pan with an oblique bottom and a cylinder-shaped loading branch pipe that the chute should mate with said cylinder-shaped loading branch pipe along annular cylindrical surfaces cambered inwardly to a working volume so that their junction line runs along an external with respect to the chute surface of the loading branch pipe.

On certain occasions it is expedient that the vertical bearing pipe accommodating the chute be fitted with double walls with a space therebetween being utilized as a gas conduit, and a bottom bounded by an internal wall of the vertical bearing pipe and communicating with the beginning of the chute with the aid of a pan arranged in the direction of material flow, the bottom of the gas flue contained between the double walls of the vertical bearing pipe and arranged above the beginning of the chute being open to the chute through an opening in the internal wall of the vertical bearing pipe, which is perforated to blast the chute with gases.

Moreover, it is sound practice that the end of the chute be provided with the pan connected to an unloading device and be fitted with a calibrated opening for proportioned return of a fraction of the treated material into the chute intake.

Since the chute is secured to the support of the vertical bearing pipe through the brackets which are movable radially and fastened by the spring-biased bolts, the design of the herein-proposed vibration furnace allows reducing temperature stresses and enhancing furnace efficiency at high temperatures. This will augment substantially the effectiveness of vibration furnaces by extending their life and by affording the possibility of utilizing them for the drying-roasting operations at temperatures of up to 500.degree.C.

The design of the loading elements of the vibration furnace makes it possible not only to reduce the passages of the loading device but to obviate accumulation of material therein.

A reduction in the passages of the furnace loading device and, hence, in its overall dimensions and weight decreases inertial loads on most stressed portion of the vertical bearing pipe of the vibration furance. This is assisted by the elimination of stress concentrators through the use of radially conjugated constructional members and due to a reduction in the area of ports in the vertical bearing pipe. All these factors enhance considerably functional reliability of the vibration furnace.

At the same time with the herein-proposed design of the vibration furnace accumulation of material in the loading device is practically avoided, insofar as the material upon striking against the wall cambered to the chute and flowing concurrently along the oblique bottom is directed tangentially to the wall and, hence, does not meet any resistance being therefore uniformly admitted into an intake coil of the conveying chute. This increases both the height of the layer of material being loaded and the throughput capacity of the vibration furnace.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood from a consideration of a detailed description of exemplary embodiments thereof, to be had in conjunction with the accompanying drawings, wherein:

FIG. 1 is a general view of the periodic vibration furnace with the annular chute;

FIG. 2 - is a sectional view taken along line II--II of FIG. 1;

FIG. 3 - is a sectional view taken along line III--III of FIG. 1;

FIG. 4 is an axonometric projection of the layout of the vibration furnace elements;

FIG. 5 - is a sectional view taken along line V--V of FIG. 2;

FIG. 6 - is a sectional view taken along line VI--VI of FIG. 5;

FIG. 7 depicts operating cycles of the unloading device of the vibration furnace;

FIG. 8 illustrates the operation of the unloading device during the discharge of material;

FIG. 9 is an attachment unit of the annular chute secured to the support of the vertical bearing pipe;

FIG. 10 is a version of attachment of insulators;

FIG. 11 illustrates the design of the insulators;

FIG. 12 is an axonometric projection of a layout of the elements of the vibration furnace as they are assembled;

FIG. 13 is a general view of a continuous vibration furnace with a helical chute;

FIG. 14 is a schematic diagram of a vibration furnace;

FIG. 15 - is a sectional view taken along line XV--XV of FIG. 14;

FIG. 16 is an axonometric projection showing the design of supporting flanges for securing radial brackets of the helical chute;

FIG. 17 is an attachment unit of the helical chute;

FIG. 18 is an axonometric projection of the loading device;

FIG. 19 is a top view of the loading device;

FIG. 20 - is a sectional view taken along line XX--XX of FIG. 19;

FIG. 21 is an axonometric projection of the gas conduit layout;

FIG. 22 is a general view of the continuous vibration furnace with an open box-type helical chute;

FIG. 23 is an axonometric projection showing the layout of the elements of a compartment-type furnace as they are assembled;

FIG. 24 is a schematic diagram of the compartment-type vibration furnace;

FIG. 25 is an axonometric projection of the gas conduit layout;

FIG. 26 depicts an attachment unit of the open chute;

FIG. 27 - is a sectional view taken along line XXVII--XXVII of FIG. 26;

FIG. 28 illustrates the layout of chute fastening elements (an axonometric projection) and

FIG. 29 is a layout of the partial recycling of the treated material being returned into the loading zone.

In terms of their design the vibration furnaces may be continuous and periodic.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

An annular periodic vibration furnace with a working volume of 0.07 m.sup.3 is intended for heat-treating loose dusting materials at a temperature of up to 550.degree.C over an unlimited period of time. The design of the vibration furnace permits the material to be treated in inert gases, if required by the technique. The working volume of the vibration furnace is dust-tight and may be equipped with additional facilities, if necessary, for operation under a vacuum. The adopted mode of conveying materials along a closed ring ensures periodic recycling of the pre-heated materials to a loading point, a feature contributing to better transportation of materials prone to sticking in their initial state. This is of prime importance for the materials which are pasty in their initial state and for the processes necessitating, according to the techniques adopted, the supply of liquid reagents onto a loose material being treated in the vibration furnace. A part of the crust of the adhered material is dried up and disintegrates under the effect of vibrations. Electric heating used in vibration furnaces ensures high reliability of the heated material along with a low thermal time lag which makes it possible to abruptly change, if required, temperature conditions in the vibration furnace.

A periodic vibration furnace comprises an annular chute 1 (FIGS. 1 and 2) rectangular in cross section with rounded corners, said chute being mounted with the help of a bracket 2 encompassing the annular chute 1 on supports 3 of a vertical bearing pipe 4. Mounted in the bottom part of the vertical bearing pipe 4 are four motors-vibrators 5 (FIGS. 1 and 3) energized in pairs. Two of them generate helical oscillations under whose effect the material being treated moves along the annular chute 1 (FIGS. 1 and 2) in a clockwise direction, in a plan view, whereas the other two motors-vibrators 5 (FIGS. 1, 3) rotate counterclockwise. The motors-vibrators 5 are mounted with their shafts inclined to the horizontal plane. The angle of inclination of each motor-vibrator 5 to the horizontal plane is a function of the ratio of horizontal and vertical amplitudes of oscillations which in turn determines the degree of thrawup and slippage of the material being treated as well as its stirring and intensity of vibrofluidization. The above characteristics are of prime importance in the selection of an optimum technological duty. The motors-vibrators 5 are fastened with bolts 6 to a plate 7 (FIGS. 1, 3, 4) of the vertical bearing pipe 4 which affords the possibility of changing the angle of inclination of the shafts of the motors-vibrators 5 to the horizontal plane stepwisely in the range of from 0 to 90.degree.. To this end the plate 7 is fitted with openings 8 (FIG. 4) arranged uniformly around the circumference and corresponding in size to those for the bolts 6 (FIG. 1). The plate 7 (FIGS. 1, 3, 4) is welded to the bottom portion of the vertical bearing pipe 4 as a chord plane and is reinforced from the interior with stiffening ribs 9. This ensures adequate strength of an attachment unit for securing the motors-vibrators 5 along with a minimum weight.

The annular chute 1 (FIG. 1) is enclosed in a detachable casing 10, the space therebetween being filled with heat-insulating mineral wool 11.

The annular chute 1 is heated owing to its ohmic resistance when connected in an electric heating circuit through flexible bars 12 (FIG. 4). At the point of attachment of the flexible bars 12 the annular chute 1 is provided with an electroinsulating connection 13 (FIGS. 2, 4, 5) made as two flanges 14 and 15 (FIG. 6) separated by an insulating plate 16. The insulatin plate 16 is fitted with holes for coupling bolts 17 (FIGS. 5, 6) located at its periphery; at the center it has a rectangular port 18 similar in shape to the passage of the annular chute 1. The holes for the coupling bolts 17 provided in the flanges 14 and 15 are made of two sizes, that of the small holes being slightly in excess of a thread diameter and that of the large ones slightly in excess of a head diameter of the coupling bolts 17. The holes of a small diameter in the flange 14 are located opposite to those of a large diameter in the flange 15 with those of large and small diameters being arranged alternately in the flanges 14 and 15. The use of the coupling bolts 17 provides an air-tight, vibration-proof, reliable, small-size, heat-resistant and electroinsulating connection of the ends of the annular chute 1.

For the sake of safety a branch pipe 19 (FIGS. 1, 4) for loading the material being treated, a branch pipe 20 for unloading the treated material, a branch pipe 21 for the removal of gaseous products and a sampling branch pipe 22 are provided with similar insulation. The treated material is discharged by means of an unloading device (FIGS. 1, 4, 7, 8) which constitutes a split section 23 in the bottom of the annular chute, whose edges overlap each other so that the right-hand edge is beaded upwards and the lefthand edge downwards. A slit formed between the beaded edges of the bottom of the annular chute 1 terminates with the unloading branch pipe 20.

The annular chute 1 (FIGS. 9, 10) with the brackets 2 is secured to the supports 3 with bolts 24 with helical springs 25 (FIG. 9) or disc springs 26 (FIG. 10).

The tightening force of the bolts 24 (FIGS. 9, 10) is adjustable and is set up during erection to ensure radial displacement of the annular chute 1 together with the bracket 2 along radial slots 27 for the bolts 24 provided in the horizontal plate of the support 3 during thermal expansion of the annular chute 1.

At the points where the bolts 24 are set up, the annular chute 1 with the bracket 2 is electrically insulated with the aid of insulators 28 from the supports 3 and from the rest of the supporting structure.

The insulator 28 (FIG. 11) is a ceramic collar 29 rolled out with the help of a bead 30 along its outside and inside diameters into metal sockets 31 and 32.

Flat annular supporting surfaces of both the outer and inner metal sockets 31 and 32 are concentric and overlap each other in a plan view. The external supporting surface of the outer metal socket 31 is fitted with an annular fillet 33 to fix the insulator 28 in the opening 34 of the bracket 2 of the annular chute 1.

The periodic vibration furnace operates in the following manner.

A batch of material to be treated is charged through the loading branch pipe 19 (FIGS. 1, 4) into the annular chute 1 which is resistance heated. When two motors-vibrators 5 are switched on the material being treated is conveyed clockwise along the bottom of the annular chute 1. Simultaneously it undergoes heat treatment lasting over the required time period. Gaseous products evolved are removed along the branch pipe 21 mated through a flexible metal pipe 35 with an exhaust ventilation system.

During the operating cycle the material being treated is conveyed from the right- to the left-hand side (FIG. 7), passes a split section 23 in the bottom of the annular chute 1, is poured over and under the effect of directed vibrations and proceeds further without entering the branch pipe 20 for unloading of the treated material.

When the treated material is unloaded, its motional direction is reversed from the left- to the right-hand side with the material which has been admitted into the unloading slit being discharged from the furnace.

A reversal in the motional direction of the material during unloading is effected by reversing switching over of the sets of the motors-vibrators 5 (FIGS. 1 and 3).

The herein-proposed design of the unloading device ensures its reliability in service and excludes the spilling of material being treated. If required the branch pipe 20 for unloading the treated material is utilized for drawing in ambient air.

According to another embodiment based on the use of the herein-proposed improvements is a continuous vibration furnace with a working volume of 0.8 m.sup.3 intended for heat treatment of loose materials not liable to stick at a temperature of up to 300.degree.C for 20-25 min. The conceptual design of the vibration furnace is determined by a continuous nature of loading and unloading operations.

An oscillating part of the vibration furnace is made as a helical chute 36 (FIG. 12) of a rectangular cross section and rounded off corners, fastened to a vertical bearing pipe 37 in whose bottom portion are mounted two vibrators 38 imparting helical vibrations to the oscillating portion of the vibration furnace. Under the effect of vibrations the material to be treated is conveyed along the helical chute 36 upwards from a loading branch pipe 39 (FIGS. 12, 13) to an unloading branch pipe 40.

The oscillating section of the vibration furnace rests at the bottom on springs 41 (FIGS. 12, 14) being held at the top with the aid of tension members 42 with springs 43. The tension members 42 are fastened to an outer frame 44 (FIGS. 13, 14) made as a three-dimensional structure formed by the sides of a parallelepiped. Suspended from the outer frame 44 are heat-insulating panels 45 made as folding flaps.

The vertical bearing pipe 37 (FIG. 15) has on its generatrices three slots 46 arranged, for instance, at an angle of 120.degree. to each other in a plan view. The slots 46 accommodate vertical straps 47 welded-in in pairs (FIG. 16) and connected by transverse horizontal supports 48. Attached to the horizontal supports 48 by bolts 49 (FIG. 17) and springs 50 are radial brackets 51 (FIGS. 15, 17) welded to the helical chute 36. Because the radial brackets 51 are bolted to the horizontal supports 48 (FIG. 17) of the vertical bearing pipe 37 with the aid of the bolts 49 spring-biased with the springs 50, the radial brackets 51 can be displaced radially with respect to the vertical bearing pipe 37 along a groove 52 (FIG. 16) during thermal expansion of the helical chute 36 (FIGS. 15, 17). The latter is heated owing to its ohmic resistance when connected in an electric heating circuit through flexible bars 53 (FIG. 12).

In this connection the radial brackets 51 (FIGS. 15, 17) of the helical chute 36 are insulated from the vertical bearing pipe 37 by the electric insulators 28 (FIGS. 10, 17). The loading branch pipe 39 (FIGS. 18, 19, 20) is connected to an intake coil of the helical chute 36 with the help of a pan with an oblique bottom 54. Pan side walls 55 (FIG. 19) are made arcuate and cambered inwardly to the working volume of the vibration furnace so that their line of junction A with the loading branch pipe 39 runs on an external with respect to the helical chute 36 surface of the loading branch pipe 39. This makes it possible to avoid accumulation of damp material in the loading device, to eliminate hazardous stress concentrators in the intake of the helical chute 36 and to enhance the degree of filling of the helical chute 36 with the material to be treated. From technological aspects the junction elements of the loading branch pipe 39 and helical chute 36 are made from stampings 56 of a helical chute 36 one of which is cross-hatched in FIG. 19.

The design of both the unloading branch pipe 40 and connecting pipes 57 (FIG. 21) for the removal of a gaseous phase are similar to that of the branch pipe 39. Ventilation of the working space of the helical chute 36 is effected by drawing air through it. The air is supplied through air intakes 58 located on one side of the helical chute 36 and drawn off through the connecting pipes 57 for the removal of a gas phase positioned diametrically and through flexible pipes 59 and a vent header 60 coupled with an exhaust ventilation system.

For heat-treating loose non-sticky materials with a large gas evolution a vibration furnace with a working volume of 6 m.sup.3 is available.

The design of the above vibration furnace made on the principle of the herein-proposed improvements enables continuous heat treatment of loose material at a temperature of up to 500.degree.C for 25-30 min., with the volume of gases drawn off into the ventilation system amounting to not more than 2,000m.sup.3 /hr. The volume of the gases being discharged is limited by the gas rate in the working volume of a vibration furnace at which dust carryover does not exceed the value permissible from technological aspects and is adjusted by varying the parameters of the exhaust ventilation system.

The vibration furnace comprises a casing 61 (FIGS. 22, 25) accommodating an open helical chute 62 (FIGS. 24, 25). In the bottom portion of the casing 61 two vibrators 38 are attached to a bracket 63 (FIGS. 23, 24), the vibrators 38 imparting helical oscillations to the vibrating system. The bracket 63 is bolted to the casing 61 through a terminal belt 64. The entire oscillating system rests through springs 65 (FIGS. 23, 24) on a frame 66 mounting a busbar panel 67 for supplying power through flexible bars 68 to the resistance-heated open helical chute 62.

The gases being evolved are removed through diffuser D, and a metal pipe 69 mounted axially in the top portion of the casing 61. The ambient air upon entering the working volume of the vibration furnace is heated in a heating apparatus 70 (FIG. 23) communicating with the vibration furnace through a flexible air pipe 71. The material admitted into a loading branch pipe 72 of the type shown in FIG. 18 is conveyed from below upwards to an unloading branch pipe 73 under the effect of helical oscillations. The unloading branch pipe 73 is mated with other technological equipment with the help of a flexible metal pipe 74 of a small cross section.

The vibration furnace assembly includes thermocouples 75 mounted on the casing 61 at the points of control of technological parameters.

The casing 61 is a vertical bearing pipe fitted with double cylinder-shaped walls 76 and 77 (FIGS. 24, 25). The internal cylindrical wall 76 is perforated to blast the chute 62 with gases with openings 78 being located along the top edge of each coil of the open helical chute 62. The space limited by the internal cylindrical wall 76 of the vertical bearing pipe has a bottom 79 in communication with the lower coil of the open helical chute 62 through an oblique pan 80. The space between the cylindrical walls 76 and 77 acts as a gas conduit for supplying ambient air through the heating apparatus 70 (FIG. 23), flexible air pipe 71 and a space between tapered surfaces 81 and 82 (FIG. 25) limited by the external wall 77 and a throat 83 through vertical shafts 84 of a small cross section and the openings 78 in the working volume of the vibration furnace.

Increased gas rates in the vertical shafts 84 preclude dust ejection from the working volume of the vibration furnace into the surroundings. The vertical shafts 84 are located intermediate of the cylindrical walls 76 and 77. The bottom 85 of the gas conduit enclosed in the space between the cylindrical walls 76 and 77 is arranged above the lower coil of the helical chute 2 and communicates with the latter through a hole 86 (FIG. 24) in the internal cylindrical wall 76 with the help of an oblique pan 87.

Material spilled from the bottoms 79 and 85 is returned along the pans 80 and 87 onto the lower coil of the open helical chute 62 into a zone proceeding to the loading station from which starting material is charged through the loading branch pipe 72.

The open helical chute 62 (FIGS. 26, 27, 28) is secured to the supporting internal cylindrical wall 76 with the aid of radial brackets 88 attached to the internal cylindrical wall 76 and interconnected by cone visors 89 (FIGS. 24, 28). In the zone of the radial brackets 88 the open helical chute 62 is furnished with radial crosspieces 90 (FIGS. 26, 28) through which the open helical chute 62 is suspended with the help of bolts 91 and springs 92 from the radial brackets 88 (FIGS. 26, 27). Owing to the bolted connection of the radial cross pieces 90 to the radial bracket 88 (with the bolts 91) the crosspieces 90 can be displaced radially along a groove 93 (FIG. 27) simultaneously with the helical chute 62 with respect to the radial bracket 88 in case of thermal expansion of the helical chute 62. The latter is heated owing to its ohmic resistance on being connected in an electric heating circuit through the flexible bars 68 (FIG. 23).

In this connection the radial crosspieces 90 (FIGS. 26, 28) of the helical chute 62 are insulated from the radial bracket 88 by the electric insulators 28 (FIGS. 26, 9).

The loading branch pipe 72 is mated with the intake coil of the helical chute 62 with the help of a pan with an oblique bottom. Pan walls are made arcuate and cambered inwardly to the working volume of the vibration furnace so that their junction line with the loading branch pipe 72 (FIG. 23) is arranged on the external with respect to the helical chute 62 surface of the loading branch pipe 72 (see the description of the preceding vibration furnace (FIG. 20).

A discharge pan 94 (FIG. 29) is equipped with appliances for recycling a fraction of the dried material to the lower intake coil of the helical chute 62 to enhance thereby transportability of the starting materials which are liable to stick when damp. In this case the dried material passes from the discharge pan 94 through an opening 95 (with a passage adjustable by a cone needle 96) onto an oblique pan 97. Then it proceeds along a vertical passage 98 onto the bottom 85 of the gas conduit enclosed between the cylindrical walls 76 and 77. After that the returned dried material pours through the hole 86 in the internal cylindrical wall 76 along the pan 87 onto the lower coil of the helical chute 62 in the zone proceeding to the loading station for the damp material. Spreading along the helical chute 62, the dried material forms a non-sticky interlayer between the surface of the helical chute 62 and sticky damp material which is being loaded. When the layers intermix under the effect of vibrations, aggregated lumps of the damp materials are coated (wrapped) with the dried material and do not grip the surface of the helical chute 62 which improves operational stability of the vibration furnace and enhances its throughput capacity.

The opening 95 of a variable section provided in the bottom of the discharge pan 94 is fitted with a deflector 99 for accumulation of a fraction of the material near the opening 95. The latter is located above the oblique pan 97 at a distance of at least a maximum height of the layer of material on the oblique pan 97.

The passage of the opening 95 is adjusted with the aid of the cone needle 96 set up axially of the opening 95 in accordance with the amount of material which is required to form the interlayer.

With the vibration furnace in operation the material to be trated upon being admitted through the loading branch pipe 72 (FIGS. 23, 24) to the lower coil of the resistance-heated helical chute 62 is conveyed under the effect of helical oscillations along the helical chute 62 upwards of the unloading station. (The transfer of the material being treated is shown in FIGS. 24, 25 by thick arrows, gas flow by thin arrows and that of the dust and spilled material by dotted arrows). In terms of an electric circuit, the helical chute 62 is subdivided into three self-contained sections with individual temperature control systems. This permits a requisite preset distribution of temperatures in the helical chute 62 to be obtained during the heat-treating operation. As to vibration conditions, they may be chosen in accordance with the process technological requirements by varying both the vibration amplitude and angle whose adjustment is envisaged by the design of the vibration furnace.

Gaseous products of the heat-treating process are removed from the furnace working volume by drawing them off into the exhaust ventilation system through diffuser D and the sealing flexible metal pipe 69. The vibration furnace can be ventilated either partially by removing only an excess volume of the gases evolved (in this case the opening for the flexible air pipe 71 is sealed) or completely with a full removal of the gases liberated from the vibration furnace by drawing ambient air through the furnace working volume. If that is the case, the air heated in the heating apparatus 70 flows along the flexible air pipe 71 into the space between the two tapered surfaces 81 and 82 to be admitted through four narrow shafts 84 into the bottom portion of the space enclosed between the cylindrical walls 76 and 77. Next the air enters the working area of the vibration furnace through the openings 78 in the cylindrical wall 76 and on being directed by the cone visors 89 passes along the helical chute 62 to be further discharged under the effect of rarefaction through diffuser D, into the exhaust ventilation system.

Claims

What we claim is:

1. A vibration furnace for loose materials, comprising: a vertical bearing pipe with supports; a chute concentric with the vertical bearing pipe and attached to said supports of the vertical bearing pipe by means of brackets radially movable under thermal expansion of said chute; said chute being electrically insulated from said supports of the vertical bearing pipe by means of insulators and resistance heated upon connecting the chute in an electric circuit a loading device communicating with the chute for ensuring the supply of loose materials onto said chute; an unloading device communicating with the chute for providing the discharge of treated loose materials from the chute; and a plurality of vibrators mounted in the lower section of the vertical bearing pipe and imparting helical oscillations to the chute.

2. The vibration furnace of claim 1, wherein the brackets are attached to said supports of the vertical bearing pipe by means of spring-biased bolts displacing in conjunction with the brackets and the chute along radial slots provided in the supports of the vertical bearing pipe.

3. The vibration furnace of claim 1, wherein the loading device comprises a pan having an oblique bottom and a loading branch pipe and the chute, which is made helical, is connected to said loading branch pipe along annular cylindrical surfaces cambered inwardly to the furnace working volume so that their junction extends along a surface of the loading branch pipe disposed externally with respect to said chute.

4. The vibration furnace of claim 1, wherein the vertical bearing pipe accommodating the chute, which is made helical, comprises an external cylindrical wall and an internal cylindrical wall with the space therebetween comprising a gas conduit, and with a bottom bounded by the internal cylindrical wall, said bottom being connected to the intake of the chute by means of a pan in the direction of motion of loose materials, and the bottom of the gas conduit between the cylindrical walls of the vertical bearing pipe located above the intake of the chute communicates with the chute through a hole in the internal cylindrical wall, said internal cylindrical wall being perforated to admit gases into the chute.

5. The vibration furnace of claim 4, further comprising a discharge pan connected to the unloading device at the end of the chute and fitted with a calibrated opening to enable a proportioned return of a fraction of the treated material into the intake of the chute for recycling.