DE3335283A1 - METHOD FOR HEAT TREATING METALS IN POT OR HOOD OVENS - Google Patents

Abstract

In a process for heating, annealing and cooling charges enclosed in containers, it is possible, during the heat treating of metals by means of pot furnaces or cover furnaces, to save thermal energy and annealing time due to the fact that cold gas from a preheating device (2) surronding a still cold charge to be heated (1) traverses fluidized beds (6) arranged inside the wall (3) of a cooling device (5) surrounding a warm charge (4) to be cooled, beds wherein is provided the aluminium oxide or the like, pulverized and maintained in a floating state by the gas flowing vertically and used as heat-exchanger, the gas being then recycled by isolated conduits of corresponding fans (16) of the preheating device (2) to be used as heating medium.

Description

P 233 ■

Patent application

of the company:

Dr. Werner Herdieckerhoff,

Nachf.

Industrial furnaces and apparatus engineering,

Viktoriastr. 10-12, 4750 Unna

Process for the heat treatment of metals in pot or hood furnaces

The invention relates to a method for heating, annealing and cooling of enclosed in recipients Batches in the heat treatment of metals with the help of pot or hood furnaces, as well as an additional one Cooling device, (DE-PS 22 56 676)

In the metal industry is during machining and the deformation to achieve certain structural conditions between the individual production steps an annealing treatment necessary. For this purpose, the metal products in an annealing furnace with and without annealing protective hoods (recipients) to a state that corresponds to the desired structural condition Temperature heated, and then cooled again outside of the oven. The cooling that occurs during cooling

In most cases, heat is still lost today because it is effectively fed back into the heat treatment process is not yet possible. The applicant has the so-called double vacuum system for glowing in recipients developed. The charge is in a recipient that can be evacuated. This, Recipients made of heat-resistant sheet metal would implode if they were heated to a high temperature and thereby would be exposed to the full vacuum with decreasing strength. That is why in the jacket space between the furnace wall and a so-called supporting vacuum is formed for the recipient, which reduces the external pressure on the recipient wall depending on the strength of the supporting vacuum. (Brochure company Dr. Werner Herdieckerhoff "Hot problems, solved by glowing technology "- double vacuum annealing system -)

The furnace technology for the heat treatment of metals of all kinds has undergone extensive optimization. Only on Individual areas is still a leap forward expected. The energy costs come more and more to the fore., Therefore, considerations have been made how energy savings can be achieved through suitable heat recovery.

The considerations have met with considerable difficulties. So far, only the exchange has been made outside the recipient's heat generated by the fan and heat exchanger, for example for heat storage in the heating system plants or the like, considered.

In order not to let the cooling process take place in the furnace, in which the annealing has taken place, it is customary to store the batch under cooling hoods or the like down to atmospheric temperature to cool down. The cooling hoods are for this purpose with water sprinklers and / or Provide cooling air fans. (DE-PS 22 56 676)

For accelerated, direct heating of workpieces, ovens have already been proposed in which the heating of the material via a heat transfer fluid he follows. This heat transfer fluid is created in so-called fluidized beds. Gas is blown through a porous bottom of the heatable container and thereby a filling of very finely grained aluminum oxide or the like whirled up. The fine particles are created by the turbulence as well as the strong molecular movement of the carrying gas stream is converted into a kind of liquid, so that the heat is much faster than is transmitted to the workpiece by radiation and convection. The heating is always done via the ignition a combustible gas mixture in a fluidized bed. Experiments with this new technique have shown that a can save a large part of the otherwise used amount of heat. This is also due to the fact that the time required is much lower. This new technology has so far only been reluctantly adopted in practice and remained more or less an outsider technique. (British Patent Specification 1 537 486)

The object of the invention is to provide an efficiently working method for hoods or hoods to be used in annealing technology To find pot furnace in which the losses of energy are reduced by suitable heat exchange processes.

The invention solves the problem posed by the teaching of method claim 1, combine its features a cooling hood, which surrounds a hot charge to be cooled, and a preheating hood, which surrounds a charge that is still cool in a heat exchange network.

With in the walls of an annealing hood or a GVI pot or shaft according to the invention, annular chamber fluidized beds are provided for accelerated heat dissipation from the recipient wall to the

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exchange the gas provided. This then transfers the heat to the charge in the preheating hood. The use of fluidized beds used within the method according to the invention in contrast to the prior art essentially an indirect way of working.

The invention can be applied to conventional annealing processes help a considerably increased profitability.

With the aid of the invention, the recipient with the annealing charge can now after the end of the heat treatment process exposed from the annealing furnace and fed to the fluidized bed heat exchanger. This is near a hood furnace designed as a combined cooling and heat exchange hood, or with pot ovens as a combined cooling or heat exchange shaft. The recipient rooms are initially still from the heat exchange system excepted, but can, as later features of the invention show, by suitable measures the recipient rooms are included. Difficulties arise with this direct gas exchange because within the recipient of the preheating hood the cold charge is usually not absolutely certain is pure. As a result, the inert gas is contaminated by drawing fats or the like. It can also

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Desired oxygen or CO may have been added through leaks. This then leads to a depreciation of the still hot, just annealed batch. However, these difficulties can be overcome by known measures which do not belong directly to the invention.

The method according to claim 1 can be improved by claim 2 if the indirectly operating heat exchange gases in addition, the jacket space between the recipient, which is closed at least in the case of double vacuum ovens and flow through the furnace interior wall.

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A much more rational way of working results by using the method according to claim 3. It is proposed here to have two approximately identical designs To use hoods or shafts and the two recipients, both the cooling device and the Preheating hood to be connected to each other directly in the heat exchange, with the two recipient interiors and in the lines, of course, an inertization must take place beforehand, as claim 3 teaches in detail.

While claim 4 complements the teachings of the preceding device in terms of device, claim 5 gives the constructive Teaching how the fluidized bed process is used in the hood, shaft or pot furnaces in question can be classified constructively. The claims 6 to 11 are essential embodiments of the invention, their advantageous effects result from the drawing and description.

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The drawing shows with

Figure 1 the combination of a cooling hood with a preheating hood and heat exchange system,

FIG. 2 shows a partial section through one of the hoods with fluidized beds for the heat exchange system.

In the form of a hood, a cooling device 5 is shown on the left and a preheating device 2 is shown on the right. These Hoods are placed with their insulated walls 3 over the recipients 11 and 12, under which are on the right the cool batch 1 and on the left the batch 4 to be cooled is located.

The recipients are like known double vacuum annealing furnaces 11 and 12 are connected in a vacuum-tight manner to a base construction 25 in each case, in which the vacuum-tight circulation is made up of fans 23 ensure the gas circulation within the recipient interior 14 and 15.

Both hoods for the cooling device 5 and for the preheating device 2 can be provided with additional cover fans 24 arranged on the cover side. The cooler may additionally have water sprinkler devices that are not shown.

For making various variations of the invention According to the method, it is expedient to close the passages of the cover fan 24 to the atmosphere in a vacuum-tight manner to make, and at least the jacket space 7 of the cooling device 5 and preferably also the jacket space 8 the preheating device 2 to be included in the heat exchange circuit.

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In the insulated walls 3 of the cooling device 5 are provided on the inner wall 9 fluidized beds 6 as multiple superposed annular chambers are formed, the porous injection openings in the upper wall 20 of the annular channels. 19, or in the bottom of the annular chambers 18 are arranged. The same applies, if necessary, between the insulated walls 3 of the Preheating device 2 and its inner wall 10.

The blowing speed within the fluidized beds 6 is set in such a way that the solids do not enter the line system 27 via the outlets of the fluidized beds 6 as well as the fan 16 can come. The regulation of the vertical air flow or the gas flow velocity is therefore of crucial importance.

Between the cooling device 5 and the preheating device insulated line systems 27 are provided. The drawing does not show all cable routing variants that may be required. It is only intended to show that, depending on the variant of the method used, different ones Arrangements are appropriate.

Shown in Figure 1 is a line routing with strongly drawn lines, which over the isolated Line 13 from the fluidized bed area of the cooling device 5 directly into the interior 15 of the recipient 12 for the preheater 2 leads. There the gas is circulated and cooled by means of the circulation fan 23 The fluidized beds 6 of the cooling device 5 are fed via fans 16, in which they again generate heat then repeat the cycle.

Such a connection without the use of inert gas is only possible if the indicated in batch 1 Temperature is still comparatively low. So can

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333S283

For example, drawing fats are evaporated before the heating of charge 1 has progressed so far that a harmful effect occurs.

But it can also be the interior 15 of the recipient after alternating vacuum drawing and subsequent rinsing received an inert gas filling and the line circuit be chosen so that an exchange cycle takes place between the recipient interiors 14 and 15.

It is also conceivable to then combine the recipient interior 15 with the jacket spaces 8 of the preheating device for heat exchange purposes 2 to be connected if this and the lines are also inerted.

The gas cycle can also be used in certain applications be subjected to heating; this is done by an external heating device 26. However, it is also possible within the fluidized beds 6, preferably at the preheating device 2 external heating devices 22 to be arranged. Such additional heating is less important in the case of the cooling device 5, although this may also be useful for procedural reasons.

The accelerated heating within the preheating device 2 can also take place by combustion heating. In this case, combustible gas is introduced into the fluidized beds 6 of the preheater 2 and into the fluidized beds ignited in a controlled manner. It can be used to generate significantly accelerated preheating processes. then the inclusion of recipient interiors is not sensible.

It is obvious that the interiors 14, the recipients 11 and 12 are similar to known fluidized bed ovens could be designed so that each there.

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formed heat transfer fluid both the heat dissipation, as well as that can serve to supply heat. It is of particular advantage that the aluminum oxide used or other suitable chemically neutral solid particles no chemical reactions with the batches can enter into, so that only on the purity of the used Carrier gas or heat exchange gas must be taken into account.

Line systems 27 indicated by dash-dotted lines, on which flanges 28 are indicated, are intended to facilitate the uncoupling of the individual lines for the production of variable functional processes. It is not necessary in detail on the basis of the example to describe the various possible circuits, because this is out of the inventive Process sequences or the proposed devices is readily apparent.

The drawing according to FIG. 2 merely supplements FIG. 1, the arrangement of the fluidized beds 6 in relation to one of the recipients 11, 12 the internal heating devices 22, the porous injection openings 21, the annular chambers 18 and the ring channels 19 and the possible circulation paths of the heat exchange gas are shown in FIG the enlarged representation more clearly. The shell space is closed, but with the drainage channels 29 of the Fluidized beds 6 connected. It can be very advantageous if, for example, different from what is shown in the drawing FIG. 2 shows the cooled gas stream coming from the preheating device 2 without the fluidized beds beforehand to flow through, the jacket space between the recipient wall and the inner wall 9 of the cooling device 5 flows through before the gas flows into the annular channels 19 and from there via the porous inlet openings 21 in the annular chambers 18 of the fluidized beds 6 can flow in.

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Which of the many possibilities that result from the arrangement according to the invention and the method according to the invention are used in each case is a question of economic efficiency for the intended use of the devices in each case. It will have to be weighed up in each case whether both hoods have to be provided with fluidized beds, or whether, if the two devices are of identical design, the apparent additional expense tends to lead to cheaper prices.

Obviously, there is a variety for the person skilled in the art of the possible applications, which are not described in the context of the graphic representations make necessary.

P.

09/27/1983 P ο si 11 ο η s ζ ah 1 en 1 is te - / »V '

1 cool batch

2 preheater 3335283

3 insulated wall

4 batch to be cooled

5 cooling device

6 fluidized beds

7 Shell space to the cooling device

B Shell space for preheating device

9 Inner wall of the cooling device

10 Inner wall of the preheating device

11 Recipient of the cooling device

12 recipient aer preheater

13 insulated line

14 Interior of the recipient

15 Interior of the recipient

16 fan

17 circuit lines

18 annular chamber

19 ring channel

20 upper wall

21 porous air blow openings

22 heating equipment

23 circulation fan

24 lid fans

25 base construction

26 external heater

27 piping systems

28 flanges

29 drainage channel

30 Recipient wall

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Claims (11)

p 233 333S283 09/26/1983 claims 1. A method for heating, annealing and cooling batches enclosed in recipients in the heat treatment of metals with the aid of pot or hood furnaces and an additional cooling device, characterized in that a preheating device (2) surrounding a still cool batch (1) to be preheated (Hood or pot) coming cool gas flows through the wall (3) of a cooling device (5) which surrounds a hot batch (4) to be cooled down and in which fluidized beds (6) are kept in suspension by the flowing gas serving as a heat exchanger, pulverized aluminum oxide or the like is located, which gas is then fed back as a heating medium via insulated lines and corresponding fans within the circuit of the preheating device (Z). 2. The method according to claim 1, characterized. that heat exchange gases additionally the jacket space (7) of the cooling device (5) and / or (8) of the preheating device (2) between the inner wall (9) of the cooling device (5) or (10) of the preheating device (2) and the recipient (11 ) the cooling device Flow through (5) or (12) of the preheating device (2). 3. The method according to one of the method claims 1 and / or 2, characterized in that in .dem recipient (12) of the preheating device (2) in addition to the inertization in the recipient (11) of the cooling device (5), an inertization takes place, such that alternately removes glowing components by vacuum drawing and subsequent inert gas flooding ₂ _ 3335263 in order to then use insulated lines (13) by means of a corresponding flap control to control the filled Recipients (12) for direct gas exchange with the recipient interior (14) of the recipient (11) connect to. 4. Device for carrying out one or more of the methods according to claims 1 to 3, characterized in that between the cooling device (5) and the preheating device (H) disconnectable circuit lines (17) guided by one or more fans (16) are arranged in such a way that are that the gas flow in the circuit between the two devices (2 and 5) flows at least once through a heat exchange system consisting of several fluidized beds (6). 5. The device according to claim 4, characterized in that the fluidized beds (6) consist of annular chambers (18) which are arranged one above the other, wherein under each annular chamber (18) there is an annular channel (19) whose upper wall (20) porous injection openings (21) to the overlying fluidized beds (6). 6. Apparatus according to claim 5, characterized in that cooled gas is passed through the jacket space (7) in the cooling device and only then flows into the fluidized beds (6), and the jacket space can be sealed off from the atmosphere and / or the fluidized bed area . 7. The device according to one or more of claims 4 to 6, characterized in that the preheating device (2) is provided with heat exchangers designed as fluidized beds (6). 8. The device according to one or more of claims 4 to 7, characterized in that the interior space or spaces of the recipients are interconnected in the line circuit with the fluidized beds (6), and only inert gas circulates in this circuit formed. 9. The device or more of claims 4 to 8, characterized cjekennzeichent _t that the cooling device (5) and / or the preheater (2) are provided with heating devices (22) preferably within the fluidized bed (6) according to one. 10. Device according to one or more of the claims 4 to 9, characterized in that the recipients (8) are provided with vacuum-tight circulating fans (23). 11. The device according to one or more of claims 4 to 10, - characterized in that the fluidized beds (6) are preferably provided with a combustion heater of the preheating device.