WO1985001519A1

WO1985001519A1 - Process for heat treating metals in pot furnaces and cover furnaces

Info

Publication number: WO1985001519A1
Application number: PCT/DE1984/000198
Authority: WO
Inventors: Rainer Herdieckerhoff; Herbert Rediger
Original assignee: Firma Dr. Werner Herdieckerhoff, Nachf.
Priority date: 1983-09-29
Filing date: 1984-09-27
Publication date: 1985-04-11
Also published as: EP0156888A1; DE3335283A1

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

DESCRIPTION

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

The invention relates to a method for heating, annealing and cooling metal batches with the aid of pot or hood furnaces, at least two of which are connected directly or indirectly via heat exchangers (US Pat. No. 3,184,225).

In the metal industry, an annealing treatment is required during processing and deformation in order to achieve certain structural states between the individual production steps. For this purpose, the metal products are heated in annealing furnaces with and without glow protection hoods (recipients) to a temperature corresponding to the desired structural condition and then cooled again outside the furnace. The on cooling anfallen¬ de waste heat is here today, in most cases ver¬ lost because an effective return to the Wärmebehandlungspro _¬ process appeared so far difficult. The applicant has developed the so-called double vacuum system for glowing in recipients. The batch is in a recipient which can be evacuated. This is made of heat-resistant sheet metal

for

Replacement, e.g. OMPI fa WIPO _R ezipient would implode if it were exposed to high heat, thereby decreasing strength to the full vacuum. For this reason, a so-called support vacuum is formed in the jacket space between the furnace wall and the recipient, which reduces the external pressure on the recipient wall depending on the strength of the support vacuum. (Brochure company Dr. Werner Herdieckerhoff "Hot problems solved by glowing technology" - double vacuum glow system -)

The furnace technology for heat treatment of metals of all kinds has been extensively optimized. A leap forward development can only be expected in individual areas. Energy costs are increasingly coming to the fore. Therefore, considerations have also been made as to how energy can be saved by suitable heat recovery.

In a proposal according to U.S. Pat. 3,184,225, two furnace rooms are connected to one another via connecting lines and a fan, and are separable via valves, in such a way that heat is exchanged.

In order not to let the cooling process take place in the furnace in which the annealing took place, it is customary to cool the batch down to atmospheric temperature under cooling hoods or the like. For this purpose, the cooling hoods are provided with water sprinkling systems and / or cooling air fans. (DE-PS 22 56 676) -

Irrespective of what has been said, for accelerated, direct heating of workpieces, it has been proposed that a material be heated using a heat transfer fluid. This heat transfer fluid is created in so-called fluidized beds. In the process, gas is blown through a porous bottom of the heatable container, thereby whirling up a filling of very fine-grained aluminum oxide or the like. The turbulence and the strong molecular movement of the supporting gas stream convert the fine particles into a kind of liquid in such a way that the heat is much faster

Replacement sheet OMPI than is transmitted to the workpiece by radiation and convection. The heating is usually carried out by igniting a combustible gas mixture in the fluidized bed. Experiments with this new technology have shown that a large part of the amount of heat otherwise used can be saved. This is also due to the fact that the time required is considerably less. This new technology has so far only been taken up reluctantly by practice and more or less has remained an outsider technology. (GB-1537486)

The object of the invention is to find a rationally operating method for hood or pot furnaces to be used in annealing technology, in which the losses in energy are reduced by suitable heat exchange methods.

The invention solves the stated problem by teaching teaching method claim 1. Its features combine a cold store which surrounds a hot batch to be cooled, and a preheating device which surrounds a still cool batch in a heat network.

In the walls of a glow hood or a glow pot or shaft according to the invention, annular chamber fluidized beds are provided, which ensure accelerated heat transfer from the recipient wall to the gas intended for heat exchange. This then transfers the heat to the charge in the preheating hood . The use of fluidized beds optimizes heat exchange, even with an indirect mode of operation, without excluding direct heat or gas exchange.

The invention can help conventional annealing processes to a significantly increased economic efficiency.

With the aid of the invention, after the heat treatment process has ended, the recipient with the annealing batch can be suspended from the annealing furnace and fed to the fluidized bed heat exchanger. This can be designed as a combined cooling and heat exchange hood in hood furnaces, or as a combined cooling or heating - A -

be designed as a metal shaft. The recipient spaces are initially excluded from the heat exchange system, but, as later features of the invention show, suitable measures can also include the recipient spaces. Difficulties arise with direct gas exchange because the cold batch inside the preheating hood recipient is not absolutely absolutely certain. This has the consequence that the inert gas is contaminated by drawing greases or the like. It can also cause unwanted oxygen or CO 2 emissions

Leaks have been added. This then leads to a

Impairment of the still hot, just annealed batch. This

Difficulties, however, cannot be directly addressed

Overcoming known measures belonging to the invention.

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

A much more efficient way of working results from the use of the method according to claim 3. Here it is proposed to use two approximately identical hoods or manholes and the two recipients, both the cooling device and the preheating hood, to be used directly in the heat exchange to connect one another, in which case, of course, inertization must take place beforehand in the two recipient interiors and in the lines.

Claims 4 to 11 supplement the teachings of the preceding method claims. They contain essential configurations according to the invention, the advantageous effects of which result from the drawing and description.

OMPI The drawing shows with

1 shows the combination of a cooling device and a preheating device with a heat exchange system,

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

A cooling device 5 on the left and a preheating device 2 on the right are shown as hoods. These hoods are inside out with their walls 3 about the recipients 11 and 12 ge, under which the right the cool Charge 1 and left the hot, ^'4 is to be cooled batch.

In the manner of known double vacuum annealing furnaces, the recipients 11 and 12 are connected in a vacuum-tight manner to a base construction 25, in which vacuum-tight circulation fans 23 ensure the gas circulation within the interior of the recipient 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 cooling device 5 can additionally have water sprinkling devices, which are not shown.

To carry out various variations of the method according to the invention, it is expedient to make the passages of the cover fans 24 closable to the atmosphere in a vacuum-tight manner and at least the jacket space 7 of the cooling device 5 and preferably also the jacket space 8 of the preheating device 2 in the heat include the metal cycle.

In the wall 3 of the cooling device 5, fluidized beds 6 are provided on the inner wall 9, which are designed as ring chambers 18 arranged several times one above the other, the porous injection openings 21 in the upper wall 20 of the ring channels 19 or in the bottom of the ring chambers 18 are arranged. The same

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OMPI

Λ. WIPO ^"• may also apply between the wall 3 of the preheating device 2 and its inner wall 10.

The blowing speed within the fluidized beds 6 is set such that the solids (powdered aluminum oxide) cannot get into the line system 27 or the fan 16 via the outputs of the fluidized beds 6. The regulation of the vertical air or gas flow velocity is therefore of crucial importance.

The insulated line system 27 is provided between the cooling device 5 and the preheating device 2. The drawing does not show all the necessary routing variants. It is only intended to show that, depending on the process variant used, different arrangements are expedient.

The line layout shown in solid lines in FIG. 1 runs via the insulated line 13 and the circular line 17 from the area of the fluidized beds 6 of the cooling device 5 directly into the interior 14 of the recipient 12 for the preheating device 2. There the gas is transferred a circulating fan 23 is circulated and, with simultaneous heating of the batch 1, is passed back to the fluidized beds 6 of the cooling device 5 via the fans 16. The gas again absorbs heat removed from the hot charge 4 in these. Then the cycle repeats itself.

Such a connection without the use of inert gas is only possible if the temperature indicated in batch 1 is still comparatively low. For example, drawing fats can be evaporated before the heating of batch 1 has progressed to such an extent that a harmful effect occurs.

However, the interior 14 of the recipient 12 can be given an inert gas filling after alternating vacuum pulling and subsequent flushing and the line circuit can be selected such that an exchange circuit between the recipient interior 14 and 15 is done.

_A lso, it is conceivable that recipient interior 14 then uses to Wärmetausch¬ with the jacket spaces 8 to connect the preheating device 2 when this and the lines are also rendered inert.

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

The accelerated, internal heating within the preheating device 2 can also take place by means of combustion heating. In this case, 6 combustible gas is introduced into their fluidized beds and ignited in a controlled manner. The preheating processes can thus be considerably accelerated. Then the inclusion of the recipient interior 14, 15 is not useful.

It is obvious that the interiors 14, 15 of the recipients 11 and 12 could also be designed in the manner of known fluidized bed furnaces in such a way that the heat transfer fluid formed there both for heat dissipation and for heat supply can. It is particularly advantageous that the aluminum oxide used or other suitable chemically neutral solid particles cannot undergo chemical reactions with the batches, so that only the purity of the carrier gas or heat exchange gas used must be taken into account.

The line system 27, indicated by dash-dotted lines, with the flanges 28 is intended to indicate that the individual lines can be uncoupled for producing variable functional sequences. It is not necessary to describe further possible circuits because they result from the process sequences according to the invention or the

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Replacement sheet $ b w_ ^p o ^~ struck devices easily result.

The drawing according to FIG. 2 only supplements FIG. 1. The arrangement of the fluidized beds 6, the internal heating devices 22, the porous injection openings 21, the annular chambers 18 and the annular channels 19 and, marked by corresponding arrows, the possible circulation paths of the heat exchange gas are made clearer in the enlarged view. The jacket space 7 is closed, but connected to the drainage channels 29 of the fluidized beds 6. It can be very advantageous if, unlike in FIG. 1, the cooled gas stream coming from the preheating device 2, without first flowing through the fluidized beds 6, flows through the jacket space lying between the recipient wall 30 and the inner wall 9 before the gas can flow into the annular channels 19 and from there via the porous inlet openings 21 into the annular chambers 18 of the fluidized beds 6.

Which of the possibilities which result from the arrangement according to the invention and the methods according to the invention, or which are used in each case, is a question of economy for the intended use of the devices in each case. It will have to be considered whether both oven hoods or only one of the two must be provided with fluidized beds 6. If the two devices are designed identically, a cost advantage may arise despite the apparent additional effort, taking into account the increase in performance. For the person skilled in the art there are a variety of possible uses which did not have to be illustrated.

Claims

1. A method for heating, annealing and cooling metal batches with the aid of pot or hood furnaces, of which at least two are directly or indirectly connected to one another via heat exchangers, characterized in that one, a preheated, is still cool Batch (1) surrounding preheating device (2) (hood or pot), coming, cool gas inside the wall (3) of a hot, cooling batch (4) surrounding cooling device (5) flows through fluidized beds (6) in which there is pulverized aluminum oxide or the like held by the vertically flowing gas serving as a heat exchanger and then the gas is recirculated as a heating medium via insulated lines from corresponding fans (16) of the preheating device (2) as heating medium is supplied.

2. The method according to claim 1, characterized in that the

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) and (10) of the preheating device (2) and flow through the recipient (11) of the cooling device (5) or (12) of the preheating device (2).

3. The method according to any one of the method claims 1 and / or 2, characterized in that in the recipient (12) of the preheating device (2) in addition to the inertization in the recipient (11) of the cooling device (5), an inerting takes place, such that alternatingly by vacuum drawing and subsequent inert gas flooding, glow-damaging constituents are removed, in order then the recipient (12) filled in this way via insulated lines (13) through a corresponding flap control for direct gas exchange with the interior (15) of the recipient (11) to connect.

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 (2) can be uncoupled, guided via one or more ventilators (16) Circular lines (17) are arranged in such a way that the gas flow in the circuit between the two devices (2 and 5) flows through at least once 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 stacked ring chambers (18), wherein under each ring chamber (18) there is an annular channel (19), the upper wall (20) po¬ has red injection openings (21) to the fluidized beds (6) lying above.

6. The device according to claim 5, characterized in that cooled gas through the jacket space (7) of the cooling device (5). is passed and only then flows into the fluidized beds (6), as soon as this jacket space (7) 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) with ver as fluidized beds (6) designed heat exchangers is seen.

8. The device according to one or more of claims 4 to 7, characterized in that the one or more interiors (14, 15) of the recipients (11, 12) in the line circuit with the fluidized beds (6) are interconnected, and in the circuit thus formed only circulates inert gas.

9. The device according to one or more of claims 4 to 8, characterized in that the cooling device (5) and / or the preheating device (2) with heating devices (22) are preferably provided within the fluidized beds (6).

10. The device according to one or more of claims 4 to 9, characterized in that the recipients (8, 9) with vacuum-tight circulation fans (23) are provided.

11. The device according to one or more of claims 4 to 10, characterized in that the fluidized beds (6) vor¬ preferably the preheating device (2) are provided with a Combustions- heating.

O PI ^? - ^ ^WIP0 . Reference list

1 cool batch

2 preheater

3 wall

4 hot batches to be cooled

5 cooling device

6 fluid beds

7 jacket space of the cooling device 5

8 jacket space of the preheating device 2

9 Inner wall of the cooling device 5 0 Inner wall of the preheating device 2 1 recipient of the cooling device 5 2 recipient of the preheating device 2 3 insulated line 4 interior of the recipient 12 5 interior of the recipient 11 6 fans 7 circular line 8 annular chambers 9 annular channels 0 upper wall 1 porous injection openings 2 internal heating device 3 circulation fans 4 cover fans 5 base constructions 6 external heating device 7 pipe system 8 flanges 9 drainage channel 0 recipient wall