EP0858574A1

EP0858574A1 - Device for heat treatment

Info

Publication number: EP0858574A1
Application number: EP96927710A
Authority: EP
Inventors: Peter Witkowski
Original assignee: Individual
Current assignee: Individual
Priority date: 1995-08-16
Filing date: 1996-08-09
Publication date: 1998-08-19
Anticipated expiration: 2016-08-09
Also published as: DE59605069D1; ATA138095A; EP0858574B1; WO1997007362A1; AT402736B

Abstract

A device for the heat treatment of a material, which device has a kiln chamber (2) for the heat treatment material and at least one preferably cylindrical heating furnace (4a, 4b) arranged on the upper surface of the kiln chamber (2) and in which at least one burner (12a, 12b) is provided for producing fuel gas which is fed in a substantially tangential manner into the heating furnace (4a, 4b) with the result that a downwardly directed, whirling fuel gas flow forms inside the heating furnace (4a, 4b), and a fuel gas flow with a slightly frustoconical boundary forms below each heating furnace (4a, 4b) in the kiln chamber (2), wherein respective means (23a, 23b) for determining the temperature of the fuel gas is associated with each heating furnace (4a, 4b), and this means (23a, 23b) is arranged inside the cone (13a, 13b) of fuel gas of only this particular heating furnace (4a, 4b).

Description

DEVICE FOR HEAT TREATMENT

The present invention relates to a device for the heat treatment of a material, which has an oven space for the heat treatment material and at least one, preferably cylindrical boiler arranged on the top of the oven space, in which at least one burner is provided for generating a heating gas which is essentially tangential is introduced into the boiler, so that a downward vortex-shaped heating gas flow is formed inside the heating boiler and a heating gas flow with an approximately frustoconical boundary is formed below each boiler in the furnace chamber.

Heat treatment furnaces are generally constructed in such a way that a plurality of burners are arranged on the lateral edge of the furnace chamber in the floor area, which burners have an open flame in the furnace chamber. However, extremely high temperatures occur in the immediate vicinity of the flame, so that the temperature distribution within the furnace space leaves something to be desired. In order to improve the uniformity of the temperature distribution in such furnaces, a so-called all-round control has been introduced, in which the burners are operated in pulses, not in succession, but in one, two or more groups. As usual, the temperature of the furnace chamber is measured in the immediate vicinity of the material to be treated. In order to obtain precise information about the temperature distribution within the entire furnace space, thermocouples are generally also provided in the ceiling or wall area of such furnaces at regular intervals in order to enable improved control of the individual burner or control groups.

A heat treatment furnace with a special temperature control is described in US-A-2,691,515. In this known heat treatment furnace, a furnace space in the form of a horizontal cylinder is provided, which is divided in the longitudinal direction into three heatable sections A, B, C, through which the material to be treated is transported. In the last section C, a central thermocouple is arranged, which controls the energy supply to the previous sections A and B via a control system, so as to maintain a uniform temperature in section C even when the furnace chamber is loaded irregularly. In contrast to the devices mentioned above, heat treatment furnaces of the type mentioned at the outset are special devices in which one or more boilers with a circular or oval cross section are provided above the furnace chamber, at least one gas or oil burner being provided in each boiler , whose longitudinal axis is arranged tangentially to the inner wall of the boiler, so that the heating gases can reach the cylindrical interior of the boiler tangentially and form a controlled vortex flow around the central axis of the boiler within the boiler. These boilers are therefore also called cyclones. Since the heating gases have the highest temperature immediately after leaving the flame, they will initially rise to the ceiling of the boiler and there will increase the gas pressure significantly. As a result of the vertical pressure gradient now present in the boiler, a resulting, downward spiraling heating gas flow is formed inside the boiler. This flow is slightly expanded laterally when leaving the boiler, i.e. when it flows down into the furnace chamber, and therefore forms a spiral heating gas flow with an approximately frustoconical boundary within this furnace chamber, which for the sake of simplicity is referred to here as a heating gas cone. In the case of such devices, a deduction for the heating gases is accordingly provided in the floor area of the furnace chamber. A cyclone-heated heat treatment furnace of this type is described in detail, for example, in DE-GM 3025 506.7. In practice, it has been shown that, compared to conventional heat treatment furnaces with these cyclone furnaces, a much more uniform and precise temperature distribution can be achieved within the furnace space with a wide variety of temperature specifications.

For the heat treatment of technologically high-quality materials, e.g. Alloys or coatings require extremely precise temperature control over a long period of time, since the specified manufacturing temperatures and times (heating curves) must be adhered to exactly in order to obtain the desired atomic structure and therefore a high-quality product.

It is therefore an object of the present invention to improve the device of the type mentioned at the outset in such a way that, on the one hand, a uniform heating gas temperature is generated within the furnace space, in particular in the area of the material to be treated, and on the other hand a change in this temperature is as rapid as possible and without excessive or falling below the target temperature.

The solution to the above problem is that each boiler is assigned a means for determining the heating gas temperature and that this means within the Heating gas cone of this and only this boiler is arranged. By means of these measures, the influence of each individual boiler on the temperature distribution within the furnace space can advantageously be precisely determined and, if necessary, changed quickly. With this arrangement, the target temperature cannot be exceeded or fallen short of, since the maximum temperature in the furnace chamber is lower than the mean temperature of the hottest heating gas cone and the lowest temperature in the furnace chamber is higher than the mean temperature of the least hot heating gas cone. Since the temperature of each individual heating gas cone can be set and monitored exactly, the arrangement according to the invention therefore makes it possible to maintain extremely small temperature tolerances with little effort and to reliably implement any time-temperature profile. In a preferred embodiment, each means for determining the heating gas temperature is assigned a means for regulating a fuel / air mixture supplied to the burner or burners. This means that the individual boilers can be operated completely independently of one another and continuously within a wide performance range, for example between 15 and 100% of the maximum output

Since the heating gas cones of the individual boilers overlap from a certain vertical distance from the furnace chamber ceiling, it has proven to be advantageous in the construction according to the invention if the means for determining the heating gas temperature is arranged at a vertical distance from the upper edge of the furnace chamber that is smaller than that Average diameter of the assigned boiler is, in particular, it is advantageous to arrange the means for determining the heating gas temperature immediately below the boiler in the furnace chamber. This constructive measure ensures that the measured temperature only records heating gases from the assigned boiler and no heating gases that originate, for example, from neighboring boilers or are reflected by side walls of the furnace chamber. However, the distance to the burner is still sufficient to display a measurement result representative of the temperature distribution in the furnace chamber and not the flame temperature of the burner.

To determine the furnace chamber temperature in the immediate vicinity of the material to be treated, there is at least one further means for determining the furnace temperature which is connected to a control device, each means for regulating the fuel-air mixture of a burner being advantageously connected to this control device for the furnace temperature . This enables a simple interrelation between the individual temperature measurements of the heating gases from the assigned boilers and the actual furnace chamber temperature in the immediate vicinity of the material. In a particularly simple manner, each means for determining the heating gas temperature is made up of at least one thermocouple, this thermocouple being electrically connected to a suitable controller which controls an actuator for the burner. A particularly simple burner control results in this exemplary embodiment in that the actuator determines the amount of air supplied to the burner and that the air supply to the burner is coupled to the fuel supply to the burner via a measuring line.

In an embodiment of the device according to the invention, it is advantageous in practice if the air supply located in front of the actuator has a section flowing around the boiler, which enables the air supplied to the burner to be preheated. By preheating the combustion air, energy is saved on the one hand, and on the other hand it is also ensured that the air supplied to the burner always has the same temperature at a certain burner setting. The air supply of each boiler is also connected to a main air supply line, which is integrated in the ceiling of the furnace chamber.

Further advantages and features of the present invention result from the non-restrictive description of an exemplary embodiment of a device of the type according to the invention, reference being made to FIGS. 1 and 2, which show the following:

FIG. 1 shows a schematic representation of a partial section of a device according to the invention with two boilers in a horizontal section through these boilers,

Figure 2 shows the device of Figure 1 in a vertical longitudinal section through the boiler.

The partial section of the device 1 for the heat treatment of a good shown in FIGS. 1 and 2 has an oven space 2, which is indicated in FIG. 2 and which generally has a closed metal jacket (not shown), on the inside of which there is a theological insulation and / or a fireclay lining 3 are arranged. The dimensions of the furnace chamber and its walls can be chosen as desired and adapted to the requirements of the respective application (desired temperature range, size and quantity of the material to be treated).

In the exemplary embodiment shown, two identical boilers 4a, 4b are placed on the ceiling of the furnace chamber 2, each of which is connected to the furnace chamber 2 via an opening 5a, 5b are. In this exemplary embodiment, each boiler 4a, 4b has an essentially cylindrical chamotte lining 6a, 6b, which is surrounded by an insulating layer 7a, 7b, which is surrounded on all sides by a double metal jacket 8a, 8b. At the top, the boiler 4a, 4b is covered by a flat fireclay ceiling 9a, 9b, an insulating layer 10a, 10b and a simple metal cap 11a, 11b.

The interior 4a ', 4b' of the boiler 4a, 4b is shown in the exemplary embodiment shown as a standing circular cylinder. In the context of the present invention, however, this interior can also have a different shape, e.g. that of a cylinder with an elliptical or oval cross-section or the shape of a polygonal standing prism. The ceiling of the boiler does not necessarily have to be flat, as shown, but can also be curved upwards, for example. It is also possible not to make the boiler cylindrical or prismatic, but rather conical or pyramid-shaped. It would also be conceivable to manufacture the boiler hemispherical or by a combination of the geometric elements mentioned above. Only a section with a circular cross-section is essential for the boiler to function properly. For practical reasons, however, the production of boilers with a cylindrical inner surface is currently preferred.

At a distance above the openings 5a, 5b, which is approximately 2/3 of the height of the respective boiler 4a, 4b, in the exemplary embodiment shown, a horizontally arranged burner 12a, 12b is provided on each boiler 4a, 4b, the longitudinal axis of which in is oriented substantially tangential to the inner surface of the boiler 4a, 4b. Depending on the available resources and application, the burners can be operated with either oil or any type of gas. In other exemplary embodiments, not shown here, 2, 3, 4 or more burners can also be provided, but all of them are arranged tangentially.

As has already been explained in detail at the beginning, the tangential arrangement of the burners causes an essentially tangential inflow of the heating gas into the round boiler and subsequently a vortex flow around the vertical central axis of the boiler within the boiler. The hot heating gases rising from the burner 12a, 12b in a helical manner cause a high gas pressure in the area of the ceiling 9a, 9b of the boiler 4a, 4b, which generates a pressure gradient oriented in the vertical direction inside the boiler. This pressure gradient, on the other hand, forms a resulting, helically downward heating gas flow, which presses the heating gases from the boiler down into the furnace chamber. For this reason, this construction is also called cyclone heating and the boilers are also called cyclones. After passing through the opening 5a, 5b, the heating gas flow widens, the envelope of this heating gas flow approximately takes the form of a truncated cone 13a, 13b and is referred to below as a heating gas cone. From a certain vertical distance from the opening 5a, 5b, which corresponds approximately to the average diameter of the cyclone boiler, the heating gas cones 13a, 13b of adjacent cyclones 4a, 4b mix with one another and form a homogeneous heating gas layer with a uniform temperature distribution within the whole, approximately sub-section of the furnace chamber 2 lying below the dash-dotted line of FIG. 2.

The precise design of a suitable burner 12a, 12b is known to the person skilled in the field of heat treatment furnaces and is not explained in more detail below. Immediately before the inflow opening 14a of the heating gases into the interior 4a 'of the boiler 4a, a so-called pulse combustion chamber 15a is provided in the cylindrical chamotte 6a, the average diameter of which is larger than that of the inflow opening 14a, so that a particularly high heating gas speed can be achieved.

Each burner 12a, 12b has an air supply 16a and a fuel supply 17a (gas or oil) in a known manner. The air supplied to the burner is supplied via a main air line 18 integrated in the ceiling of the furnace chamber 2, from which a partial air flow is conducted between the walls of the double jacket 8a by means of a pipe 19a connected thereto, so that the air quantity supplied to the burner 12a flows around the boiler 4a laterally while preheating to a certain temperature to enable better combustion. A pipe 20a arranged essentially diametrically opposite the pipe 19a finally leads the preheated air from the double jacket 8a to the burner 12a. The tube 20a is provided with a throttle valve which can be actuated by means of a servomotor 21a (or a pneumatic or hydraulic drive) which is controlled by a controller 22a which is connected to a thermocouple 23a which is located directly below the boiler 4a, namely within the heating gas cone 13a of this boiler 4a in the furnace chamber 2. As can be seen in Figure 2, the thermocouple 23 a is arranged so that it can only be reached by the heating gas flow of the boiler 4 a, so that the temperature measurement recorded by the controller 22 a is influenced only by the cyclone heating boiler 4 a. The thermocouple 23b, however, is arranged according to the invention within the heating gas cone 13b of the boiler 4b, but outside the cone 13a of the boiler 4a. Figure 1 can also be seen that the sensor of the thermocouple 23 a is arranged at a distance from the central axis of the cyclone 4 a.

In the exemplary embodiment shown, the fuel supply is controlled synchronously with the control of the air supply 16a via a measuring line 24, which connects the pipe 20a to a regulator 25 of the fuel supply 17a. The regulator 25 can either be a constant pressure regulator (eg a gas actuator or another gas regulator) or a suitable one Be an oil regulator. Furthermore, a gate valve 26, a filter 27 and a solenoid valve 28 are provided in the fuel supply 17a. The slide 26 and the valve 28 are arranged on both sides of the filter 27 and the regulator 25 adjacent to the filter 27, in order to make it easy to change or maintain the filter 27 or the regulator 25. The burner 12a also has schematically indicated ignition electrodes and a flame monitor 29.

In order to obtain an exact value for the oven temperature in the immediate vicinity of the material to be treated, an additional one or more thermocouples (not shown) can be arranged at this point, which are connected to a control device 30, which in turn is connected to each controller 22a in Connection is established. This can be done via a data bus or suitable electronic control lines. This enables simple central control of several boilers 4a, 4b. However, the controllers 22a do not have to be physically separated from the control device as in the exemplary embodiment shown, but can also be in the control device 30 in another exemplary embodiment not shown here, e.g. be integrated on a Leiteφlatte or in a chip.

With the device according to the invention, it is not only possible to keep the entire furnace space at a certain temperature, but there is also the possibility of generating a temperature gradient within the furnace space 2 in which the individual heating gas cones 13a, 13b each heat to a different temperature become. These temperatures are predefined for the individual controllers 22a and monitored by the thermocouples 23a, 23b.

The cyclone heating of the type according to the invention makes it possible, for example, to operate an oven chamber at temperatures of approximately 100.degree. C. to 1400.degree. C. or higher without using forced heating gas converters at low temperatures, as is customary in previously known ovens must, which in turn are a hindrance at high temperatures and often no longer withstand these temperatures. So far, it has been common to operate separate furnaces for low and high temperatures, which has resulted in high manufacturing and running costs. These disadvantages can thus be avoided in a simple manner by the present invention.

Claims

EXPECTATIONS

1. Device for the heat treatment of a product, which has an oven chamber (2) for the heat treatment product and at least one, preferably cylindrical, boiler (4a, 4b) arranged on the top of the oven chamber (2), in which at least one burner (12a, 12b) For generating a heating gas is provided, which is introduced essentially tangentially into the boiler (4a, 4b), so that a downward eddy-shaped heating gas flow is directed inside the boiler (4a, 4b) and below each boiler (4a, 4b) in the furnace chamber ( 2) forms a heating gas flow with an approximately frustoconical boundary, characterized in that each boiler (4a, 4b) is assigned a means (23 a, 23b) for determining the heating gas temperature and that this means (23a, 23b) within the heating gas cone ( 13a, 13b) this and only this boiler (4a, 4b) is arranged.

2. Device according to claim 1, characterized in that each means (23a) for determining the heating gas temperature is assigned a means (21a, 22a) for regulating a fuel-air mixture supplied to the burner (12a).

3. Apparatus according to claim 1 or 2, characterized in that the means (23a, 23b) for determining the heating gas temperature below the associated boiler (4a, 4b) is arranged at a vertical distance from the upper edge of the furnace chamber (2), which is smaller than the average diameter of this boiler (4a, 4b).

4. The device according to claim 3, characterized in that the means (23a, 23b) for determining the heating gas temperature is arranged immediately below the boiler (4a, 4b) in the furnace chamber (2).

5. Device according to one of claims 1 to 4, characterized in that in the immediate vicinity of the material to be treated at least one further means for determining the furnace temperature is arranged, which is connected to a control device (30).

6. Device according to claims 2 and 5, characterized in that each means (21a, 22a) for controlling the fuel-air mixture of a burner (12a) is connected to the control device (30) for the furnace temperature.

7. Device according to one of claims 1 to 6, characterized in that each means for determining the heating gas temperature has at least one thermocouple (23a, 23b).

8. Device according to claims 2 and 7, characterized in that the thermocouple (23 a) is electrically connected to a controller (22a) which controls an actuator (21a) for the burner (12a).

9. The device according to claim 8, characterized in that the actuator (21a) determines the amount of air supplied to the burner (12a) and that the air supply to the burner (12a) is coupled via a measuring line (24) to the fuel supply (17a) of the burner .

10. Device according to one of claims 1 to 9, characterized in that the air supply (16a) located in front of the actuator (21a) has a section (8a) which at least partially flows around the boiler (4a) and which preheats the air supplied to the burner enables.

11. The device according to claim 10, characterized in that the section of the air supply (16a) flowing around the boiler (4a) is formed by a double metal jacket (8a) of the boiler (4a).

12. The apparatus of claim 10 or 11, characterized in that the air supply (16a) of each boiler (4a) is connected to a main air supply line (18) which is integrated in the ceiling of the furnace chamber (2).