Patent Grant
8465603
1. Field of the Invention
The invention relates to a method and a device for regulating process gases for heat treatments of metal materials/workpieces in industrial furnaces, which have at least one treatment chamber, at least one burnoff point having gastight closable valve, and a pressure regulator, at least one component of the respective process gas being prepared in at least one process-relevant range of dimensions.
2. Description of the Related Art
In general, it is known in industrial furnaces that, for example, in the case of typical carburization gassing, the flushing method is applied. I.e., an established quantity of protective gas is permanently supplied to the furnace continuously and is exhausted from the furnace while being burned off (flared off) at a burnoff point. This flushing is necessary in order to achieve a quasi-stationary equilibrium state in the atmosphere through mixing of continuously newly supplied protective gas and/or natural gas-air mixtures and thus be able to regulate the carbon (C) potential.
On the one hand, the thermal loss during flare off of the protective gas at the burnoff and, on the other hand, the actual gas loss, which must be compensated for by new components of the process gas, are disadvantageous in this continuous furnace flushing technique. In addition, the burnoff gas has a C potential previously defined by the regulator, which is also no longer usable and is simply burned off.
According to DE 10 2008 029 001.7 B1, the processing effect of the gas control in industrial furnaces was improved in that, to save protective gas and reduce heating energy losses, a hydrocarbon was supplied on demand for the carburization and the C potential in the protective gas was regulated and reactions which cannot be regulated and/or are undesired were prevented. A novel protective gas recirculation system was thus provided for gas carburization. The components carbon dioxide, oxygen, and water vapor react therein in a preparation chamber of an industrial furnace with a supplied hydrocarbon to in turn form carbon monoxide and hydrogen, in a catalytically supported manner. The regeneration of already “consumed” protective gas, i.e., a protective gas having a low C potential, is advantageously thus achieved. The C potential regulation occurs in the preparation chamber of the treatment chamber. The “prepared” protective gas can then be fed back into the treatment chamber at one or more points, so that a real cycle results for the gas carburization.
The protective gas is regularly no longer burned off, but rather supplied by recirculation back to the heating chamber, after it has passed through an intermediate step, the preparation, in an internal or external preparation chamber. It is thus no longer flushed as previously, but rather reused.
Through the carburization inside the heating chamber, the concentrations of CO2, H2O, and O2 rise and the C level drops. This depleted gas is not combusted, but rather conducted using a circulator into the mentioned preparation chamber, which is locally separated from the heating chamber. A C level enrichment occurs here through the finely-dosed addition of natural gas, the following reactions occurring and the concentrations dropping again.
The gasification method cited according to DE 10 2008 029 001.7 B1 was refined according to DE 10 2009 038 598.3 in that the generation and enrichment of the protective gas can be performed in this case as a separate preparation and separated from the batch. The batch can thus always have a homogeneous gas atmosphere applied thereto.
However, for process-related and also safety-technical reasons, industrial furnaces still require a burnoff point having gastight closable valve and a pressure regulator, which is not predominantly used for permanent flare-off, but must also include the function of explosion safety, during the performance of heat treatments using the process gases described, for example. Known burnoff points in this context are functionally characterized by a permanent gas flow and thus by disadvantageously high gas losses according to internally known prior art. This is mechanically solely solved in that an overpressure flap, which is not terminated completely gastight, is provided for dissipating overpressure occurring in the furnace chamber, this flap not being regulated in the normal case, but rather at best being opened according to rigidly set experiential values.
The invention is based on the object of providing a method and a device for regulating process gases for heat treatments of metal materials/workpieces in industrial furnaces of the type mentioned at the beginning, in which the burnoff point is also only opened as a function of requirements related to process gases, while maintaining both the safety-technical conditions and also conditions which save process gas, this being achieved by a configuration made of valves and slides, which release different process-related burnoff quantities.
This object is achieved in a method for regulating process gases for heat treatments of metal materials/workpieces in industrial furnaces, which has at least one treatment chamber, at least one burnoff point having at least one first valve, and a pressure regulator having pressure meter, the process gas being prepared in at least one component of a respective gas mixture in a range which can be limited and/or being used as a flushing gas in a step of a flushing gasification, in that
In a fourth step, the flushing gasification (cf. step one) can advantageously be activated and adjusted.
The method is further implemented in that in the event of a large pressure rise, in a fifth step, an overpressure flap of the burnoff point for pressure dissipation is opened in a controlled manner via a fixed limiting value.
If the setting of a C level is required for the process, it can be regulated independently of the pressure regulation of the furnace controller by at least one C potential regulator and set via a gas and air supply.
The method can be applied for batch-by-batch heat treatments or in the case of heat treatments of metal materials/workpieces in a pusher furnace.
The flushing gasification which is activated in the fourth step can be adjusted before a batch movement, a batch change, or the charging of a batch.
The controlled flushing gasification can be activated until a flushing time has passed or a selected carbon monoxide content is reached.
The request for the flushing gasification can be initiated from the furnace controller, in order to free the furnace chamber from residues of foreign gases.
The method is particularly suitable for application in protective gas recirculation systems, in which the components carbon dioxide, oxygen, and water vapor are reacted with a supplied hydrocarbon to form carbon monoxide and hydrogen again in a recirculating manner for a gas carburization in an internal or external preparation chamber of the industrial furnace.
In the event of a large pressure rise, in the fifth step, an overpressure flap of the burnoff point is opened, which is ideally closed gastight per se during steps 1 to 4.
The use of a hand slide in the burnoff also makes the method applicable in the special case in which depletion of the furnace atmosphere occurs because of very small leakage gas quantities and thus a defined small quantity of gas must be permanently burned off, which is normally less than the typical burnoff quantities.
The method can particularly unfold its advantages through the combination of a sequence of the method steps one to five if
In terms of the invention, the above-mentioned range, which can be limited, for the preparation of the process gas can have the following dimensions
Furthermore, the mentioned preparation chamber of the industrial furnace can be implemented both internally according to DE 10 2008 029 001.7 B1 or also externally according to DE 10 2009 038 598.3, in the last mentioned case, generation and enrichment of a protective gas being performed as a separate preparation and separately from the batch.
The device for performing the method comprises
The gastight closable overpressure flap of the burnoff point for the controlled pressure dissipation completes the device.
The regulated setting of the gas and air supply is performed by the C potential regulator, which acts independently of the pressure regulation of the furnace controller.
For the special cases, such as small leakage gas quantities of the furnace, a hand slide is provided, in order to generate a leakage gas quantity, which is at least required for maintaining the atmospheric composition, by gas burnoff.
The device comprises solenoid valves or adjustable valves as valves, which are activated depending on the processing state in the furnace and release the flow through the burnoff point. Various gas quantities may thus be burned off in various burnoff trains. As a function of the program step, furnace pressure, and the atmospheric composition, different valves are activated and only the minimal required quantity of gas is thus burned off. In the case of a disturbance, all valves release the passage and thus allow a rapid flushing out procedure of the furnace chamber. An overpressure flap, which was also typical up to this point, is now implemented according to the invention, however, so that it is regulated closed tight up to an established furnace pressure and is regulated to open upon exceeding this pressure and thus—also essentially regulated—ensures a rapid pressure dissipation.
The furnace pressure regulation is performed via the controlled feed of a gas mixture. In the normal case, the burnoff point is closed using the overpressure flap. For the pressure regulation, the furnace pressure is permanently detected and the mixture quantity required for maintaining the pressure is supplied.
During the pressure rise gasification, if the pressure falls below a minimum furnace pressure, the maximum possible gas mixture quantity is supplied until a set opening time of the valves has passed or a preset furnace pressure is reached. The control of the burnoff valves is performed similarly to the furnace pressure regulation in this case.
In the figures:
An industrial furnace 1 having a treatment chamber 2 is schematically shown in an exemplary embodiment in
The regulator outputs signals for the opening or closing of a burnoff valve 4.1, implemented as a solenoid valve, for example, a burnoff point 4, and signals of a fresh gas valve 7, implemented as a solenoid valve, for example.
According to the method
The fundamental principle of the method is thus established.
In this example, in a fourth step the flushing gasification (cf. step 1) is activated and adjusted before a door and batch movement, for example.
Finally, in a fifth step, in the event of large pressure rise, an overpressure flap 4.3 can also be opened for pressure dissipation in a controlled manner via a fixed limiting value.
For this purpose, the device for performing the method essentially comprises
An assigned hand slide 4.2 having shutoff valve 4.4 allows the continuous burnoff of a small exhaust gas quantity through corresponding slide settings.
The invention allows the burnoff point 4 to only be opened as a function of requirements related to the process gas, and while maintaining both the safety-technical conditions and also the environmentally-protective saving of process gases.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2009 058 642 | Dec 2009 | DE | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 1961766 | Jennings | Jun 1934 | A |
| 8313586 | Edenhofer et al. | Nov 2012 | B2 |
| 8333852 | Grobler et al. | Dec 2012 | B2 |
| Number | Date | Country | |
|---|---|---|---|
| 20110139265 A1 | Jun 2011 | US |
