CS261231B2 - Industrial furnace for thermal treatment of passing workpieces - Google Patents

Abstract

The furnace (1) includes a furnace chamber (2) which at one end has a charging opening (5) and at the other end a chute (11). Between charging opening (5) and chute (11), there extends an endless conveyor belt (12) which, above the chute (11), is deflected in the direction of the charging opening (5). In order to avoid a constant heat loss through the empty section (17) of the conveyor belt (12) emerging from the furnace chamber, a heat transfer device (15) is provided in the region of the charging opening (5) between the cold working section (14) running in and the hot empty section (17) running out. <IMAGE>

Description

BACKGROUND OF THE INVENTION The present invention relates to an industrial furnace for heat treatment of passing workpieces with a furnace chamber having a charging hole at one end and a drop shaft at the other end with an endless conveyor belt deflected in the drop shaft region. and the empty branch pass through the charging chamber of the furnace chamber and pass through the furnace chamber from the charging hole to the drop shaft, with the conveyor belt drive mechanism as well as the other outside the furnace chamber and with the charging hole adjacent the deflector. the branches extending from the charging opening to the working branch entering the charging opening, the two branches outside the furnace chamber are guided one above the other.

Said industrial furnace is described and illustrated in the article Criteria for Optimal Design of Industrial Furnaces for Thermal Treatment of Small Parts in Warmme, Gas International, Volume 33, Workbook 9 in Fig. 14. which is exited from the furnace chamber, can be transferred to a work belt on which cold workpieces are deposited and therefore the work belt is fairly cool, thereby saving the cost of heating the work belt after entering the furnace chamber. As can be seen, in this embodiment, the working belt, i.e. the working branch of the belt, and the empty branch are guided in the region of the charging opening of the furnace chamber just one above the other.

Such an industrial furnace has significant advantages in terms of thermal energy balance as compared to industrial furnaces in which an empty branch protrudes from the trap shaft space. Since the empty branch inside the furnace chamber is led back to the inlet opening, the temperature of the empty branch remains at the process execution temperature, and the thermal energy that is in the empty branch is used specifically to heat the working branch, while the empty branch itself cools temperatures that preclude premature wear of the drive device. The heat released during cooling is immediately absorbed by the workbench and does not ineffectively radiate into the environment. Thus, without additional external energy supply, the temperature of the working branch is increased and is much closer to the temperature of the execution process.

However, such a known industrial furnace makes it possible to transfer from the empty branch to the working branch only as much thermal energy as the radiation and heat conduction through the surrounding conveyor belt guiding devices.

Based on the prior art, it is an object of the invention to improve the industrial furnace described so that more heat energy can be transferred from an empty to a working branch with the same heat transfer path.

The object is achieved by an industrial furnace according to the invention, characterized in that a heat transfer device is provided between the empty strand and the conveyor belt of the conveyor belt in the heat transfer area, or rollers for heat transfer of thermally conductive and refractory material which are rotatably and perpendicular to the direction of travel of the workbench and on which the workbench of the conveyor belt is supported, the empty conveyor belt being held in contact with the peripheral surface of the heat transfer rollers via the thrust device. _t

The heat transfer device formed by the roller pulleys, which is arranged between the empty strand and the working strand, forms a thermal bridge between the strands, so that the strands are thermally conductively connected to one another throughout their width. Furthermore, the use of pulleys produces virtually no additional friction, which the conveyor belt would have to overcome, since only a rolling movement occurs between the heat transfer pulleys and the back sides of the working and empty branches.

The empty strand thrust device may be formed either by a substantially straight sliding track or by a plurality of thrust rollers, which are axially parallel to the heat transfer rollers. The first embodiment has the advantage of being somewhat simpler to manufacture, while the second embodiment requires less drive forces for the conveyor belt. According to an embodiment, they are

251231 in each case either the pressure rollers or the heat transfer rollers are mounted in a respective sliding guide in which the roller is longitudinally displaceable in the direction of the sliding track.

The heat loss caused by the operation of the conveyor belt can be further reduced if a pre-chamber connected to the furnace chamber through which the conveyor belt passes and in which at least a part of the heat transfer device is provided, is connected to the furnace chamber. workpieces.

Notwithstanding the improvement of the thermal insulation, the pre-chamber largely prevents the introduction of air into the furnace atmosphere and hence unacceptable changes in its composition. The empty branch of the conveyor belt, which exits the furnace chamber, continuously transports the furnace atmosphere to the pre-chamber, which is purged in the furnace atmosphere in this way. The foreign air possibly entering with the workpieces can thus be forced out by the entrained furnace gases. A water siphon to be used according to the prior art is therefore not necessary.

Since the working branch and the empty branch pass through the filling opening one above the other, the loss of the furnace atmosphere is also generally less than in the prior art.

It is particularly advantageous if the filling opening is provided above the conveyor belt and viewed in the conveying direction in front of the heat transfer device. In this way, the entire length of the heat transfer device, the transfer of heat from the empty branch to the working branch and to the workpieces is utilized.

The invention is explained in more detail below by way of example with reference to the drawing. .

Fig. 1 shows a longitudinal section through an industrial furnace according to the invention. Giant. 2 is also a longitudinal sectional view of the pre-chamber of the industrial furnace of FIG. 1, but on a larger scale and without the conveyor belt passing therethrough. Giant. 3 is a cross-sectional view taken along the line III-III of FIG. 1. FIG. 4 shows the furnace chamber of the industrial furnace of FIG. 1 in a section along the line IV-IV of FIG. Fig. 5 is a sectional view of the conveyor belt of the industrial furnace of Fig. 1 in a perspective view.

FIG. 1 shows an industrial furnace 6 which serves for the continuous heat treatment of workpieces, for example for cementation, nitration, nitrocementation, etc. The industrial furnace 6 has a furnace chamber 6 which is provided with a thermal insulation lining along its length and extending from one side wall. to the second side wall of the heat pipe 6, in which burners are provided for heating the furnace atmosphere. The furnace chamber 2 has a charging opening 5 in one end wall 5, to which is connected an outwardly extending oven chamber 6 which is in the form of an oven and which is also thermally insulated. In cross-section, the approximately rectangular interior space 7 of the antechamber 6 is flush with the charging aperture 6 and terminates in the filling aperture 6, which is arranged opposite the charging aperture 5.

At that end of the furnace chamber 2, which is opposite to the partition wall 6, a drop shaft 64 is provided in the bottom 4 of the furnace chamber 2, leaving workpieces passing through the furnace chamber 2, an industrial furnace 4.

For conveying the workpieces from the filling opening 4 through the chamber 6 and the furnace chamber 2 up to the drop shaft 11, an endless refractory conveyor belt 12 is provided in the industrial furnace 4, which is actuated by a drive device 3 arranged in front of the chamber. The upstream branch of the conveyor belt 12 forms upwardly from the drive means 13, forming a working branch 8 which passes through the filling opening 4 into the interior 7 of the antechamber 7, passes through the heat transfer device 15 described in more detail below and finally enters the charging opening 6 into the interior of the furnace. inside the furnace chamber 2, there is a working branch 60 which extends from the driving device 13 and is guided horizontally, supported by the hearths 60, which is shown in more detail in FIG. 4 in cross-section. At the end of the hearth 10 adjacent to the drop shaft 11, there is provided a return device 16 for the conveyor belt 12, which is formed by a roller roller freely rotatable within the furnace chamber 2. The width of the roller corresponds to the width of the conveyor belt used. above the opening of the drop shaft 11 arranged within the furnace chamber 2 approximately 180 ° back in the direction of the drive device 13. The objects supplied by the working branch 14 fall here into the drop shaft 11 and thus leave the furnace chamber 2. That section of conveyor belt 12 moving back under the working branch 14 and referred to as the empty branch 17, passes through the interior of the furnace chamber 2 back to the charging opening 5, wherein another deflection pulley 18 pivotally arranged adjacent the charging opening 5 lifts the empty branch 17 freely passing inside the furnace chamber 2. close ^to the underside of the branches 14 and e feed opening 5 through which the branch 17 is empty again, exits the furnace chamber 2 shall have only slight headroom. The empty branch 17 coming from the charging aperture 5 then passes through the heat transfer device 15 provided in the antechamber 6, then exits through the filling aperture 8 ^{from the} interior space 2 of the antechamber 6 and enters the driving device 13.

The drive device 13 comprises essentially two axially parallel rotatable pulleys 19, 20, of which the pulley 19 serves as a conveyor belt tensioner pulley 12, while the pulley 20 is driven at low speed by the drive motor 21 to drive the conveyor belt 12.

For the sake of completeness, motor-driven fan blades 22 are provided below the ceiling of the furnace chamber 2 to agitate the atmosphere of the furnace chamber, the composition and temperature of which are controlled by a partial pressure probe 23 and a thermometer 24.

The aforesaid hearth 10 disposed within the furnace chamber 2 essentially consists, as can be seen from FIG. 4, of two rails 25, 26 arranged parallel to one another, which are fixedly fixed to a total of four transverse chamber 2 in the illustrated embodiment. The beams 27 are, as can also be seen from FIG. 4, freely engaged in corresponding recesses 28, 29 in the lining 31 of the furnace chamber 2.

Since the angle rails 25, 26 are intended to support the working branch 14 of the conveyor belt 12, their spacing relative to each other corresponds to the width of the conveyor belt 12 which is provided with edge guides 32, 33 to prevent workpieces from falling.

In conjunction with FIGS. 2 and 3, a heat transfer device 15, which is provided in the antechamber 6 between the working branch 14 and the empty branch 17 of the conveyor belt 12, is explained in more detail below. The furnace chamber 2 continuously transferred the heat transferred to the working branch 14 moving from the pre-chamber 6 to the furnace chamber 2, thereby achieving two effects. The empty branch 17 is cooled to an acceptable temperature upon leaving the furnace chamber 2, so that no refractory devices need to be formed in the drive device 13. Furthermore continuously transfers heat discharged empty branch 17 ^to work branch 14, which allows to maintain the heat loss from the furnace chamber 2 ^{at a} low value.

In a practical embodiment of an industrial furnace 2 according to the invention, the following values could be measured on the conveyor belt 12. The empty branch 1 'emerging from the charging opening 5 exhibited a furnace atmosphere temperature of about 800 ° C. On the heat transfer device 15, i.e., adjacent the feed opening 8, the empty branch 17 has been cooled from the aforementioned 800 ° C to about 60 ° C. The heat released was transferred to the workbench 21 / provided with the workpieces, which had a temperature of 40 ° C in the feed opening 2 and was already heated to 600 ° C by the feed opening 2.

As can be clearly seen, the heat transfer device 15 allows a marked improvement in the heat balance, since the heat delivered by the empty strand 17 does not go to the surroundings without any benefit, but can be used to heat the workbench 14 and workpieces.

In the illustrated embodiment, the interior space 2 of the antechamber 6 is delimited by a steel tube 41 of rectangular cross section extending from the filling opening 8 to the outside of the front wall 4 of the furnace chamber 2, forming a bottom 42, two side walls 43, 44 spaced apart. as well as the ceiling 45 of the inner space T. The thermal insulation of the pre-chamber 6 is provided outside the steel pipe 41, the clear width of which corresponds to the width of the conveyor belt 12.

The heat transfer device 15 within the steel tube 41 is formed by a total of five heat transfer rollers 46a, 46b, 46c, 46d, 46e, which are formed of a steel tube of appropriate width and rotatable perpendicular to the direction of travel of the conveyor belt 12 On these pulleys 46a, 46b, 46c, 46d, 46e, the rear sides of the ram 14 and the empty branch 17 are retained. This creates thermal contact or a thermal bridge between the opposing working branch 14 and the empty branch 17. The empty branch 17 it is moved over the bottom 42 and fixed flat horizontal slide track 47 whose width is slightly smaller than the spacing of the two guide rails 32, 33 of the conveyor belt 12, as shown in Fig. 3. this achieves a flat bracket blank 17 branches, ^{and on the} surface of the conveyor belt 12 of the receiving workpieces, thereby preventing the conveyor belt 12 with its guide He lifted himself on the slideway 47 and remained lying with cavities. The sliding track 47 extends from the feed opening 8 to the charging opening 2 # where it passes into an inclined ramp 48 which extends into the furnace chamber 2. Five rollers 46a abut on the upwardly facing rear side of the empty branch 17, supported by the sliding track 47. 46b, 46c, 46d, 46e for heat transfer, which can move freely in height. The workbench 14 moves in the anterior chamber 2 with its rear side along the outer peripheral surfaces of the heat transfer rollers 46a, 46b, 46c, 46d, 46e and, under the force of gravity, is on the outer peripheral surface of the heat transfer rollers 46a, 46b, 46c held. These heat transfer pulleys 46a, 46b, 46c, 46d, 46e are made of a thermally conductive and refractory material and have an outer diameter of 10 to 80 mm, preferably of 10 to 50 mm, and a mean distance of approximately 100 mm to each other, thereby The slack of the conveyor belt 12 between two adjacent heat transfer rollers 46a, 46b, 46c, 46d, 46e is avoided.

For each of the heat transfer pulleys 46a, 46b, 46c, 46d, 46e each of the side walls 43, 44 has a rectangular pocket 49a, 49b, 49c, 49d, 49e through which the pulleys 46a, 46b, 46c, 46d, 46e pass through their end side. with a relatively large radial clearance, since their axial length is greater than the clearance between the two side walls 43, 44. To prevent the successive displacement of the heat transfer rollers 46a, 46b, 46c, 46d, 46e, it is outside the interior space 7. attached ^to each of the two side walls 43, 44 is a curved flange 51, 52 which serves merely as a leading surface for the two adjacent faces of the heat transfer rollers 46a, 46b, 46c, 46d, 46e.

If, as will be explained below, the guide rails 32, 33 extends over the back side of the conveyor belt 12 J ^e must rollers 46a, 46b, 46c, 46d, 46e of the heat transfer at the end side to fit in the manner shown in FIG. 3, to prevent the conveyor belt 12 with its guide rails 32, 33 from erecting on the heat transfer rollers 46a, 46b, 46d, 46e, whereby the rear side of the conveyor belt 12 abuts the cavity. If cylindrical tubes are used for the heat transfer rollers 46 as shown, it will suffice for the cylindrical tubes 53 of correspondingly smaller diameter to be slid into the cylindrical tubes at the end sides and fixed thereto.

In order to largely prevent outside air from entering the furnace chamber 2, a free-swinging flap 54 is suspended above the filling opening 2, which slides on the workbench 14 and lifts the workpieces moving up the conveyor belt 12 into the antechamber 2. a flame curtain can be formed between the working branch 14 and the empty branch 17 of the conveyor belt 12 by means of the burner nozzles 55, which further seals the interior of the furnace chamber 2 against the ambient air. If still penetrate the external air into the prechamber 2 »is flushed furnace atmosphere emerging from the prechamber 2 ^and its filling opening 2» ^C ° F can be performed easily especially when the conveyor belt 12 is designed gas-permeable, as shown in FIG. 5 Thereafter, a continuous slight flushing of the pre-chamber 6 through the furnace atmosphere takes place over the entire cross-section of the interior 7, effectively preventing air from entering the furnace chamber 2.

In the cut-out of FIG. 5, the axonometrically illustrated conveyor belt 12 is formed by a plurality of flattened wire spirals 56a, 56b, 56c extending transversely to the longitudinal direction of the conveyor belt 12, respectively two adjacent wire spirals 56a and 56b and 56b and 56c respectively. they are connected to each other by a common, also transversely arranged circular rod 57a, 57b, 57c, 57d. At each end of the wire spirals 56a, 56b, 56c, two plates 58a, 58b, 58c, 58d each slide on each of the two circular bars 57a, 57b, 57c, 57d, forming the two guide rails 32,33. In this case, each of the plates 58a, 58b, 58c, 58d is slid onto two adjacent circular bars 57a, 57b, 57c, 57d, respectively, thereby forming a scaled overlap of the plates 58a, 58b, 58c, 58d in the longitudinal direction of the conveyor belt 12 as this can be seen in FIG. 5.

Outside the plates 58a, 58b, 58c, 58d, the annular bars 57a, 57b, 57c, 57d are bent in the same direction to the adjacent annular bar 57a, 57b, 57c, 57d and are connected thereto by a hooked end.

If the frictional forces exerted by the sliding track 47 are too great, it is also possible to place other pulleys rotatably under each of the heat transfer rollers 46a, 46b, 46c, 46d, 46e instead of the continuous sliding track 47, whereby between the conveyor belt 12 and the parts in the antechamber 8 which comes into contact with the conveyor belt 12, it only provides a rolling movement.

Claims (10)

SUBJECT OF THE INVENTION An industrial furnace for heat treatment of passing workpieces with a furnace chamber having a charging opening at one end at the other end of a drop shaft, with an endless conveyor belt deflected in the area of the drop shaft upstream of the workpieces. the empty branch passes through the charging opening of the furnace chamber and passes through the furnace chamber from the charging opening to the drop shaft, with the conveyor belt drive mechanism as well as the other outside the furnace chamber arranged and with the charging opening adjacent the deflector. extending from the charging opening to the working branch entering the charging opening, the two branches outside the furnace chamber are guided one above the other, characterized in that between the empty branch (17) and the working branch (14) of the conveyor belt (12) is heat treatment equipment / 15) for heat transfer, said heat transfer device (15) being formed more of the width of the conveyor belt (12) by means of cylindrical or cylindrical rollers (46, 46a, 46b, 46c, 46d, 46e) for heat transfer from thermally conductive and refractory material, which are mounted rotatably and perpendicular to the direction of travel of the working branch (14) and on which the working branch (14) of the conveyor belt (12) is supported, and that the empty branch (17) of the conveyor belt (12) is kept in contact with the peripheral a flat pulley (46, 46a, 46b, 46c, 46d, 46e) for heat transfer by a thrust device. Industrial furnace according to claim 1, characterized in that the pressing device is formed by a substantially straight sliding track (47) on which the empty branch (17) of the conveyor belt (12) slides and which supports the empty branch (17) and each of the heat transfer rollers (46, 46a, 46b, 46c, 46d, 46e) is freely movable in a perpendicular direction with respect to the surface formed by the slide (47). Industrial furnace according to claim 1, characterized in that the thrust device comprises thrust rollers arranged axially parallel to the heat transfer rollers (46, 46a, 46b, 46c, 46d, 46e) and either: each heat transfer roller (46, 46a, 46b, 46c, 46d, 46e) is provided with a sliding guide in which each roller is guided vertically longitudinally in the direction of the second roller. An industrial furnace according to claim 1, characterized in that a pre-chamber (6) connected to the furnace chamber (2) is connected to the furnace chamber (5) through which a conveyor belt (12) passes and in which at least a part of the device is provided. 15) for heat transfer, and that the antechamber (6) is provided with a feed opening (8) for inserting workpieces. Industrial furnace according to claim 4, characterized in that the filling opening (8) is arranged above the conveyor belt (12) and viewed in the conveying direction in front of the heat transfer device (15). 6. Industrial furnace according to claim 1, characterized in that the heat transfer pulleys (46, 46a, 46b, 46c, 46d, 46e) are in the form of cylindrical tubes having a diameter of 10 mm to 80 mm, preferably 10 mm to 50 mm. Industrial furnace according to claim 1, characterized in that, viewed parallel to the movement of the conveyor belt (12), the length of the heat transfer device (15) is 0.5 m to 2 m. Industrial furnace according to claim 1, characterized in that at least five equidistantly arranged pulleys (46, 46a, 46b, 46c, 46d, 46e) are provided as heat transfer devices (15). Industrial furnace according to claim 1, characterized in that the conveyor belt (12) is gas-permeable. Industrial furnace according to claim 9, characterized in that the conveyor belt (12) is formed by a plurality of spirals (56a, 56b, 56c) arranged parallel to each other, two adjacent ones being connected to each other by a rod (57a, 57b, 57c). , 57d /.