EP0858574B1 - Device for heat treatment - Google Patents

Description

The present invention relates to an apparatus for heat treatment of a Good things that have an oven space for the heat treatment goods and at least two at the Has the top of the furnace chamber arranged, preferably cylindrical, in which is provided at least one burner for generating a heating gas, which in the is introduced substantially tangentially into the boiler, so that within the Boiler a downward vortex-shaped flow of heating gas and below each Boiler in the furnace room a hot gas flow with an approximately frustoconical Limitation forms. Such a device is from document DE-A-3 035 906 known.

Heat treatment furnaces are generally built so that on the side edge of the Furnace space in the bottom area a plurality of burners are arranged in the furnace space to lead an open flame. However, extremely high levels occur in the immediate vicinity of the flame Temperatures on, so that the temperature distribution within the furnace space to be desired leaves. To improve the uniformity of the temperature distribution in such furnaces, So-called all-round control has been introduced, in which the burners are not at the same time, but in one, two or more groups alternately in succession in pulse form operate. The temperature of the furnace room is, as usual, in the immediate vicinity of the measured good to be treated. For precise information about the temperature distribution to get within the entire furnace space are generally also in the ceiling or Wall area of such ovens provided periodic thermocouples to a to enable improved control of the individual burner or control groups.

A heat treatment furnace with a special temperature control is in the US-A-2,691,515. In this known heat treatment furnace there is a furnace space provided in the form of a lying cylinder, which in the longitudinal direction in three heatable Sections A, B, C is divided, through which the material to be treated is transported. in the last section C is a central thermocouple, which is controlled controls the energy supply to the previous sections A and B, and so does one irregular loading of the furnace space in section C a uniform temperature to obtain.

In contrast to the facilities mentioned above, it is about Heat treatment furnaces of the type mentioned above around special devices in which one or more boilers with a circular or oval one above the furnace chamber Cross section are provided, with at least one gas or oil burner in each boiler is provided, the longitudinal axis of which is arranged tangentially to the inner wall of the boiler, so that the heating gases can get tangentially into the cylindrical interior of the boiler and within the boiler a controlled vortex flow around the central axis of the Train the boiler. These boilers are therefore also called cyclones. Since the Heating gases are at the highest temperature immediately after leaving the flame they first climb to the ceiling of the boiler and there the gas pressure significantly increase. The vertical pressure gradient now present in the boiler forms inside the boiler a resulting downward spiral Heating gas flow off. This flow is when leaving the boiler, that is, when it flows down into the furnace chamber, slightly expanded laterally and therefore forms inside this furnace chamber a spiral heating gas flow with an approximately frustoconical Boundary, which for the sake of simplicity is referred to here as a heating gas cone. in the The floor area of the furnace space is therefore a deduction for such devices Heating gases provided. A cyclone heated heat treatment furnace of this type is for example described in detail in DE-GM 30 25 506.7. In practice it has been shown that in Compared to conventional heat treatment furnaces with these cyclone furnaces within the Furnace room a much more uniform and precise without much effort Temperature distribution with a wide variety of temperature specifications can be realized can.

For the heat treatment of technologically high-quality materials, e.g. Alloys or Coatings, is an extremely precise temperature control over a long period of time necessary because the given manufacturing temperatures and times (heating curves) must be adhered to exactly in order to achieve the desired atomic structure and accordingly to get high quality product.

It is therefore an object of the present invention, the device of the aforementioned Kind to improve in such a way that within the furnace space, especially in the area of treating good produces a uniform heating gas temperature on the one hand, on the other hand Change this temperature as quickly as possible and without exceeding or falling below the Target temperature can be made.

The above object is achieved by the characterizing features of claim 1.

Since the heating gas cones of the individual boilers from a certain vertical distance of overlap the furnace ceiling is in the construction according to the invention the means for determining the heating gas temperature in one Vertical distance from the upper edge of the furnace space, which is smaller than that average diameter of the assigned boiler. Because the temperature of each individual heating gas cone can be set and monitored exactly, allows the arrangement according to the invention therefore, to maintain extremely small temperature tolerances with little effort and reliably to implement any time-temperature curve. In a preferred one Embodiment is each means for determining the heating gas temperature each a means for Control of a fuel-air mixture supplied to the burner or burners assigned. This allows the individual boilers to be within a wide range Power range, e.g. between 15 and 100% of the maximum output, completely independent from each other and continuously operated.

In particular, it is advantageous that Means for determining the heating gas temperature immediately below the boiler in Arrange the furnace space. This constructive measure ensures that the measured temperature recorded only the heating gases of the assigned boiler and none Heating gases that come from neighboring boilers, for example, or through side walls of the furnace space are reflected. However, the distance to the burner is still sufficient to give a measurement result representative of the temperature distribution in the furnace chamber display and not the flame temperature of the burner.

To determine the furnace chamber temperature in the immediate vicinity of the material to be treated is there at least one further means for determining the furnace temperature is provided, which on a control device is connected, advantageously each means for Regulating the fuel-air mixture of a burner to this control device for the Oven temperature is connected. This is a simple correlation between the individual temperature measurements of the heating gases from the assigned boilers and the actual furnace chamber temperature can be produced in the immediate vicinity of the material.

Each means for determining the heating gas temperature is particularly simple constructed at least one thermocouple, this thermocouple electrically with a suitable controller is connected, which controls an actuator for the burner. A special one simple burner control results in this 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 of the burner via a measuring line.

In one embodiment of the device according to the invention, it is in practice advantageous if the air supply located in front of the actuator hits the boiler flowing around portion, which preheats the air supplied to the burner enables. Preheating the combustion air saves energy on the one hand, on the other hand, it also ensures that the air supplied to the burner at a certain burner setting always has the same temperature. The air supply each boiler is also connected to a main air supply line, which is in the ceiling the furnace chamber is integrated.

Figur 1 eine schematische Darstellung eines Teilabschnittes einer erfindungsgemäßen Vorrichtung mit zwei Heizkesseln in einem Horizontalschnitt durch diese Heizkessel,

Figur 2 die Vorrichtung gemäß Figur 1 in einem vertikalen Längsschnitt durch die Heizkessel.

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

1 shows a schematic illustration 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 heat treatment shown in FIGS. 1 and 2 of a good has a furnace space 2, which is indicated in FIG generally has a closed metal jacket (not shown) on the Thermal insulation and / or a fireclay lining 3 are arranged on the inside. The dimensions of the furnace chamber and its walls can be chosen arbitrarily and to the Requirements of the respective application (desired temperature range, size and quantity of the material to be treated).

In the embodiment shown, two identical ones are on the ceiling of the furnace space 2 Boiler 4a, 4b placed, each connected to the furnace chamber 2 via an opening 5a, 5b are. Each boiler 4a, 4b essentially has one in this embodiment cylindrical chamotte 6a, 6b, which is surrounded by an insulating layer 7a, 7b, which is enclosed laterally all around by a double metal jacket 8a, 8b. Is upwards the boiler 4a, 4b through a flat fireclay ceiling 9a, 9b, an insulating layer 10a, 10b and a simple metal cap 11a, 11b covered.

The interior 4a ', 4b' of the boiler 4a, 4b is in the embodiment shown as a standing circular cylinder shown. In the context of the present invention, this But also have a different shape, e.g. that of a cylinder with a elliptical or oval cross-section or the shape of a polygonal standing prism. The The boiler ceiling does not necessarily have to be flat, as shown, but can also be curved upwards, for example. It is also possible to Boilers are not cylindrical or prismatic, but conical or pyramid-shaped to train. It would also be conceivable to make the boiler hemispherical or through a To produce a combination of the aforementioned geometric elements. Essential for one proper functioning of the boiler is only a section with one circular cross section. For practical reasons, however, the production of Boilers with a cylindrical inner surface are preferred.

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

As already explained in detail at the beginning, the tangential arrangement of the Burner an essentially tangential inflow of the heating gas into the round boiler and subsequently a vortex flow around the vertical central axis within the boiler of the boiler. The hot heating gases rising helically from the burner 12a, 12b cause a high gas pressure in the area of the ceiling 9a, 9b of the boiler 4a, 4b, which generates a vertical pressure gradient within the boiler. This pressure gradient, on the other hand, forms a resulting downward helical shape directed heating gas flow, which the heating gases from the boiler down into the Oven chamber presses. For this reason, this construction is also called cyclone heating and the boilers also called cyclones. After passing through the opening 5a, 5b the heating gas flow widens, the envelope of this heating gas flow approximates a frustoconical shape 13a, 13b and in the following as Heating gas cone is called. From a certain vertical distance from the opening 5a, 5b, which corresponds approximately to the average diameter of the cyclone boiler, the mix Heating gas cones 13a, 13b of adjacent cyclones 4a, 4b with each other and form a homogeneous Heating gas layer with a uniform temperature distribution throughout, 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 art Known field of heat treatment furnaces and will not be explained in more detail below. Immediately in front of the inflow opening 14a of the heating gases into the interior 4a 'of the boiler 4a is a so-called pulse combustion chamber 15a in the cylindrical chamotte 6a provided, whose average diameter is larger than that of the inflow opening 14a is, so that a particularly high heating gas speed can be achieved.

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

The fuel supply is controlled synchronously in the exemplary embodiment shown with the control of the air supply 16a via a measuring line 24 which connects the tube 20a with a Controller 25 of the fuel supply 17a connects. The controller 25 can either be a Equal pressure regulator (e.g. a gas actuator or another gas regulator) or a suitable one Be an oil regulator. Furthermore, a gate valve 26, a filter are in the fuel supply 17a 27 and a solenoid valve 28 are provided. The slide 26 and the valve 28 are both Sides of the filter 27 and the regulator 25 adjacent to the filter 27 are arranged around a to allow easy replacement or maintenance of the filter 27 or the controller 25. The Burner 12a furthermore has schematically indicated ignition electrodes and one Flame monitoring 29 on.

To get an exact value for the furnace temperature in the immediate vicinity of the to be treated To receive good things, another or more (not Thermocouples can be arranged, which are connected to a control device 30 are connected, which in turn is connected to each controller 22a. This can be done through a Data bus or suitable electronic control lines. This will make it easy Central control of several boilers 4a, 4b possible. However, the regulators 22a do not have to as in the illustrated embodiment, physically from the control device be separated, but can be in another embodiment, not shown here also in the control device 30, e.g. integrated on a circuit board or in a chip his.

With the device according to the invention it is not only possible to open the entire furnace space to maintain a certain temperature, but there is also the possibility within the Furnace chamber 2 to generate a temperature gradient in which the individual heating gas cones 13a, 13b are each heated to a different temperature. These temperatures are given to the individual controllers 22a and by the thermocouples 23a, 23b supervised.

The cyclone heating of the type described makes it possible, for example, to have one Operating the furnace chamber at temperatures of approx. 100 ° C to 1400 ° C or higher without as usual with previously known furnaces, at low temperatures forced heating gas converters must be used, which in turn are a hindrance at high temperatures and often no longer withstand these temperatures. So far, it has been common for low and High temperatures operate separate ovens, causing high manufacturing and ongoing Operating costs incurred.

Claims (12)

1. Device for the thermal treatment of an item, disposing of a furnace space (2) for the items to be thermally treated and at least two, preferably cylindrical boilers (4a, 4b) positioned at the upper end of the furnace space (2), in which at least one burner (12a, 12b) is provided to generate heating gas, which gas is introduced largely tangentially into the boilers (4a, 4b), so that a vortex-shaped heating gas flow facing downward is formed inside the boilers (4a, 4b), while another, roughly conically delimited heating gas flow is formed below either boiler (4a, 4b) in the furnace space (2), characterized in that one means (23a, 23b) is assigned to either boiler (4a, 4b) to ascertain the heating gas temperature, with this means (23a, 24b) being located below the boiler (4a, 4b) assigned to it, and at a vertical distance which extends from the upper edge of the furnace space (2) and is smaller than the mean diameter of this boiler (4a, 4b), and within the heating gas cone (13a, 13b) of this and only this boiler (4a, 4b).
2. Device according to Claim 1, characterized in that one means (21a, 22a) for regulating the fuel-air mixture introduced into the burner (12a) is assigned to either means (23a) for determining the heating gas temperature.
3. Device according to Claim 2, characterized in that the burner (12a, 12b) disposes of an impulse combustion chamber (15a, 15b) linked to the interior (4a', 4b') of the boiler (4a, 4b) via an admission port (14a), with the mean diameter of the impulse combustion chamber (15a, 15b) being wider than that of the admission port (14a).
4. Device according to Claim 3, characterized in that the means (23a, 23b) for determining the heating gas temperature is located immediately below the boiler (4a, 4b) inside the furnace space (2).
5. Device according to one of Claims 1 to 4, characterized in that at least one further means to determine the furnace temperature is located in the immediate vicinity of the items to be treated and connected to a control device (30).
6. Device according to Claims 2 and 5, characterized in that either means (21a, 22a) for regulating 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 either means for determining the heating gas temperature disposes of at least one thermocouple (23a, 23b).
8. Device according to Claims 2 and 7, characterized in that the thermocouple (23a) is electrically connected to a control unit (22a) controlling a servo component (21a) for the burner (12a).
9. Device according to Claim 8, characterized in that the servo element (21 a) determines the quantity of air introduced into the burner (12a) and that the air introduced into the burner (12a) is coupled to the fuel supply (17a) of the burner via a measuring section (24).
10. Device according to one of Claims 1 to 9, characterized in that the air supply (16a) situated upstream of the servo component (21a) disposes of a section (8a) that generates an at least partial flow around the boiler (4a) and enables the pre-heating of the air introduced into the burner.
11. Device according to Claim 10, characterized in that the air supply (16a) section generating a flow around the boiler (4a) is formed by a double metal casing (8a) of the boiler (4a).
12. Device according to Claim 10 or 11, characterized in that the air supply (16a) of either boiler (4a) is connected to a main air supply conduit (18) integrated into the ceiling of the furnace space (2).

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