EP0368033A1 - Device for the control of the gas pulse burners in a tunnel furnace - Google Patents

Abstract

The invention relates to a device (control device) for controlling the gas pulse burners (2) of a tunnel furnace (1), which serves to fire ceramic products (blanks) and has a plurality of burner groups in the firing zone, each burner group having a plurality of gas pulse burners, i.e. gas burners with a gas feed (connection) connected electrically in intervals (cycles), that are to be connected sequentially, and the control device switching the individual gas pulse burners functionally in a prescribed cycle, and the pulse length of the respective gas feed (burner connection) and the gas pressure being adjustable. The inventive step is to be seen in a microprocessor control of the gas pulse burners which enables adjustment of burner power, in which control the connection period of any gas pulse burner (2) is switched as an interval fraction and is controlable (adjustable). In this arrangement, a switching arrangement is advantageously present in accordance with which each gas pulse burner (2) remains (is) connected for a time computed from the preselected pulse number and burner connection period. At least a few of the gas pulse burners (2) can be operated with at least two pressure stages - in which case the gas pulse burner connection time and/or frequency of the gas feed can be regulated separately. <IMAGE>

Description

The invention relates to a device for controlling gas pulse burners of a tunnel furnace, according to the preamble of claim 1.

As is well known, the kiln car stock requires, i.e. the material to be burned (kiln) stacked on a kiln car, which can be moved in cycles through a tunnel kiln, viewed in the kiln cross-section, partially different heat input in order ultimately to ensure uniform heating of all the ceramic moldings to be fired.

A device of the generic type has become known several times in practice - namely by a gas pulse burner control system with the switching unit of the "GI-12" type from the KELLER group of companies from D-4530 Ibbenbüren-Laggenbeck.

This known control device is designed in such a way that the gas is supplied in pulses to the combustion zone areas in which gas auto-ignition is ensured, and that the furnace cross section corresponds to that a "flame profile" (or "firing profile") for each burner group as well as the burning duration, ie the time when the gas supply is switched on, can be set within each interval of the individual gas pulse burners. "Flame profile" is understood to mean the curve in the furnace cross section on which the flames of all gas pulse burners used are during the burner group activation. To determine the height of the flames within the furnace cross-section, ie ultimately the so-called. To determine "flame penetration depth" in the cross-sectional outline of the kiln car stock, the gas pressure is adjustable. A gas supply with low and high pressure can take place alternately, in which case (each) the gas pulse burner acts one time in the upper area of the trim and the other time in the lower area of the trim and thus a better temperature distribution over the cross-sectional height of the trim (the so-called . "Stocking height") is achieved.

Since the pulse time and interval time (cycle time) can be set independently of one another in the known gas pulse burner control, a correction of the pulse time is necessary when changing the interval time in order to obtain a certain "burner output". With a pulse count of 60 pulses per minute, the pulse time (gas burner pulse time) is 0.5 seconds. The gas pulse burner is thus switched on 60 x 0.5 seconds per minute (i.e. in operation). If the interval / cycle time is set to 2 seconds, this results in 30 pulses per minute. 30 The or each gas pulse burner would then be switched on without changing the pulse time 30 x 0.5 sec., Which means a total of 15 sec.

The disadvantage of the previous gas pulse burner control is therefore a cumbersome and / or time-consuming Setting to obtain a certain burner output. One reason for this is that changing one parameter also requires another parameter to be changed.

The invention is therefore based on the object of providing an improved gas pulse burner control for tunnel furnaces which enables the required temperatures in the individual regions of the furnace cross section to be set in a simple and rapid manner and thereby ensures a non-reactive setting.

According to the invention, this is achieved by a gas pulse burner control with a microprocessor that enables a burner output setting, in which the on-time of each gas pulse burner can be regulated (set) as a fraction of an interval.

With such a device, simple and time-saving adjustment of the power required in each case on the individual gas pulse burners of a burner group is possible. It is particularly advantageous that the setting of the output results in largely non-reactive setting work - as is known, only a certain burner output is required for a specific firing result. Since in the device according to the invention on the one hand the burner output per burner is adjusted as a fraction of the interval (ie percentage of the duty cycle) and on the other hand the pulses per minute are adjusted jointly (ie centrally) for all pulse burners, an automatic correction of the pulse time results when the number of pulses changes individual gas pulse burner, because the burner output is specified and maintained. If - in comparison to the aforementioned example relating to the prior art - a burner output is set at a pulse number of 60 pulses per minute, at which the If, for example, a fraction of the interval is 50% of the cycle time, the gas pulse burner has a pulse time of 0.5 seconds and the switch-on time (so-called intervention time) of this gas pulse burner is therefore 60 x 0.5 seconds = 30 seconds Pulse number to 30 pulses per minute - due to the "burner output" parameter - the pulse length is automatically changed, which ultimately means that the pulse of the gas pulse burner is extended to 1 sec. And the intervention time / switch-on time of the same gas pulse burner remains at 30 seconds.

Further features of the invention emerge from the subclaims.

In the drawing, an embodiment of the invention is shown and will be explained in more detail below.

• Figur 1
  eine schematische Draufsicht auf einen Ausschnitt der Brennzone eines Tunnelofens, mit gruppenweise zusammen­gefaßten Gasimpulsbrennern, die jeweils mit einem Elektro­magnetventil ausgestattet sind, und
• Figur 2
  eine schematische Übersicht der Schaltglieder-Anordnung einer jeden Brennergruppe.

Show it:

• Figure 1
  a schematic plan view of a section of the combustion zone of a tunnel kiln, with grouped gas pulse burners, each of which is equipped with an electromagnetic valve, and
• Figure 2
  a schematic overview of the switching element arrangement of each burner group.

A tunnel furnace 1 according to the invention is provided in particular for firing ceramic products and is equipped with a plurality of burner groups in the firing zone.

Each burner group comprises a large number, for example max. 15, gas pulse burner 2.

These gas pulse burners 2 of each burner group are preferably arranged on the tunnel furnace 1, acting from above.

Preferably, the gas pulse burners 2 are designed in accordance with DE-PS 35 13 820, i.e. equipped with a gas supply and an air supply, so that air can be pressed through the lance body between the gas impulses.

The burner system can be provided for reducing burning.

As can be seen from FIG. 1, a gas supply main valve 4 can be connected by a gas line 3 with the interposition of each branch off a main gas line, numbered 5, for each burner group.

The individual gas pulse burners 2 of each burner group preferably extend on both sides of this main gas line 5. In addition, viewed in the width direction of the tunnel furnace 1, they can be offset with respect to one another, i.e. lie on a zigzag line (see FIG. 1). In the gas pulse burner arrangement shown, each burner group has an odd number of gas pulse burners 2 - the side gas pulse burners lie one behind the other in the longitudinal direction of the tunnel furnace, and the rest are arranged in a gap in the width of the tunnel furnace.

As can be seen from FIG. 2, all function control elements of a gas pulse burner group are connected to a connection and setting device 6, from which a multi-core, preferably 10-core cable 7 leads to a controller unit 8. The connection and setting device 6 is equipped with a microprocessor, not shown. This microprocessor is used to calculate and comply with the values to be observed for optimal firing of the ceramic moldings - it is able to switch / control the respective preselected burner output regardless of the set number of pulses (number of pulses per minute).

While the controller unit 8 can be arranged at a large distance (possibly 100 m and more) from the tunnel furnace 1, the connection and setting device 6 is advantageously in the vicinity of the respective burner group, so that only short distances from this connection and setting device to the individual gas pulse burners are available. The connection and setting device 6 can be arranged at a short distance next to the tunnel furnace 1 or even above the same.

The individual gas valves of the gas pulse burner 2 can be switched electrically, in particular by means of an electromagnetic valve.

At least some, preferably all, gas pulse burners 2 of the tunnel furnace firing zone can be operated with at least two pressure stages, so that the gas which is supplied periodically and in pulses is one time (ie at low gas pressure) in the upper region of the stocking and the other time (ie at high pressure) Gas pressure) ignites in the lower area of the firing flame - due to self-ignition due to sufficiently high temperature.

According to Figure 2, the solenoid valves of a main valve 4, a valve 9 for switching the second pressure stage of the gas pulse burner 2, possibly a purge air valve 10 and possibly a reduction valve 11 are connected to the connection and setting device. In addition, a pressure switch 12 is connected to the connection and setting device 6.

Each connection and setting device 6 is installed in a stable housing with a separately accessible connection space. All setting and signaling elements required for operation are clearly arranged and advantageously user-friendly on the front panel behind a viewing window.

• (a) Brennerleistung-Einstellelemente für jeden Gasimpuls­brenner 2 einer Brennergruppe, mit denen die gewünschte Brennleistung als ein Intervall-Bruchteil (beispielswei­se etwa 10 - 70 % von einem Zyklus/Intervall der zyklischen Gaszufuhr-Einschaltung) einstellbar ist,
• (b) Impulslänge-Einstellelement für jede Druckstufe, vorzugs­weise für zwei Druckstufen P1 und P2, wobei insbesondere Zeiten für die Gaszufuhr (beispielsweise etwa 10 - 300 Millisekunden) einstellbar sind,
• (c) Druckstufen-Einstellelemente, mit denen die Gaszufuhrmenge pro Zeit (beispielsweise etwa 8 - 120 Liter pro Minute) einstellbar ist,
• (d) Faktor-Einstellelement, mit welchem die Einschaltdauer in der niedrigen Druckstufe P1 verlängerbar ist (beispiels­weise um den Multiplikator 1 - 2).

The following setting elements, in particular rotary knobs, are available on the front of the device:

• (a) burner output setting elements for each gas pulse burner 2 of a burner group, with which the desired combustion output can be set as an interval fraction (for example approximately 10-70% of a cycle / interval of the cyclical gas supply activation),
• (b) Pulse length adjusting element for each pressure level, preferably for two pressure levels P1 and P2, in particular Times for the gas supply (for example about 10-300 milliseconds) can be set,
• (c) pressure setting elements with which the gas supply quantity per time (for example approximately 8-120 liters per minute) can be adjusted,
• (d) Factor setting element with which the duty cycle can be extended in the low pressure stage P1 (for example by the multiplier 1 - 2).

Furthermore, in the case of training for reducing firing, the participation time (reduction time) per pressure level can be set separately (for example 10-300 milliseconds).

The configuration switches, which can only be set when a burner group is started up, are preferably located inside the device 6. A clear arrangement and good adjustability is also provided here. Specifically, the number of burners in the group is set and each gas pulse burner 2 involved in the reduction is released.

• 1. Bedieneinheit für Zeiten, Impulse und Anzeigen,
• 2. Zentraleinheit mit Mikroprozessor und
• 3. die Ein- und Ausgabeeinheit mit Klemmenleiste.

The required electronics are preferably housed on 3 boards:

• 1. control unit for times, impulses and displays,
• 2. Central unit with microprocessor and
• 3. the input and output unit with terminal strip.

The burner control of each gas pulse burner group is housed as a compact control unit in the connection and setting device, numbered 6. This control unit switches on up to 15 gas pulse burners 2 in succession. Each gas pulse burner 2 remains switched on for a time calculated from the preselected number of pulses and the burner on time.

This power is maintained at all times and always corresponds to the preselected duty cycle (for example 0 - 70% of 1 cycle / interval), even if the pulse frequency changes due to automatic (in particular initiated by the microprocessor) change in the pulse length.

The pulse length results from the following calculation:

All gas pulse burners 2 are started in succession and remain switched on for the calculated time. The time offset between switching on the individual gas pulse burners 2 depends on the number of gas pulse burners 2 used and is calculated as follows:

Any flame profile can be set using the furnace cross-section.

The burner output is independent of the set number of pulses per minute.

With a pre-selected burner output, the number of pulses per minute can be used to set the flame depending on the height of the stock (i.e. according to the requirements which depend on the height of the fired goods / stock stacked on the kiln car).

The dependence of the burner output on the pressure (flame above or below) is determined in a particularly preferred embodiment by a factor (multiplier 1-2) for the low balanced pressure. The height of the flame profile is shifted as a whole (almost a parallel shift of the flame or firing profile over the furnace cross-section height). However, it is also possible (ie in another embodiment) to operate the gas pulse burners 2 with two (or more) pressure levels and to carry out the gas supply on-time for each pressure level individually.

The setting of the burner group is very simple because the individual settings can be carried out largely without reaction. With the control unit according to the invention, an optimal equalization of the fire in the tunnel furnace firing zone can be achieved.

In each burner group there is a temperature sensor (thermocouple or optical pyrometer) for a two-point controller. This switches the control unit of the device numbered 6 with a slow pulse-pause ratio on and off. This controls the desired temperature in the firing zone.

In the off period, all gas pulse burners 2 of a burner group are switched off. In the on-period, the burners are switched optimally in terms of pulses.

A special feature of the control device is that the duty cycle of each gas pulse burner 2 is switched as a fraction of an interval / cycle and can be regulated.

Another special feature is that at least some of the gas pulse burners 2 can be operated with at least 2 stages and the switching time and / or frequency of the gas supply can be regulated separately.

Another distinguishing feature of the control circuit (not shown, but can be understood by the person skilled in the art on the basis of the functional description) is that at least some, preferably all, gas pulse burners 2 of a burner group can be operated with at least two pressure stages and the duty cycle of the same in one pressure stage by means of a factor - i.e. a percentage change - is changeable; in a particularly preferred manner there is a circuit arrangement according to which the duty cycle can be extended in the low pressure stage. A time setting for pressure level 1 and pressure level 2 can be provided so that the burning time can be set separately in the upper and lower firing range.

• 1. Nach Einschalten des Gasimpulsbrenner-Magnetventils strömt das Gas mit hoher Geschwindigkeit in den Ofen­raum und zündet selbsttätig. Vom Brennermundstück aus ent­wickelt sich die Flamme bis zu einer bestimmten Tiefe in den Besatz hinein. Diese Tiefe ist durch den Gasdruck P1 oder P2 einstellbar.
• 2. Mit der Impulszahl pro Minute wird die Charakteristik der Flamme über die Tiefe in den Besatz hinein (sogenannte Brenntiefe) eingestellt. Sobald die Flamme die Brenntiefe erreicht hat, stellt sich ein stationärer Zustand ein. Wenn in diesem Moment die Gaszufuhr unterbrochen wird, fällt die Flamme in sich zusammen. Der zeitliche Verlauf der Auf- und Abklingphase erfolgt nach einer e-Funktion. Bei herkömmlichen Öfen ist bei ca. 120 Impulsen pro Mi­nute dieser Grenzwert erreicht. Geringe Impulszahlen be­ deuten eine längere Verweildauer im stationären Flammenzustand und dadurch eine längere Energiezufuhr im unteren Bereich der Flamme.
• 3. Die Einstellung gemäß Punkt 2 ist für beide Druckstu­fen getrennt einstellbar.
• 4. Da bei geringem Druck (Flamme oben) weniger Gas aus­strömt, kann über den erwähnten "Faktor" die Ener­gie angepaßt werden - hierzu muß lediglich der Faktor-­Regler betätigt, insbesondere verdreht werden.
• 5. Die Brenndauer im oberen und im unteren Brennbereich ist getrennt einstellbar.

The control circuit is constructed in such a way that various setting parameters are provided for the optimal setting of the geometric flame pattern:

• 1. After switching on the gas pulse burner solenoid valve, the gas flows into the furnace chamber at high speed and ignites automatically. The flame develops from the burner mouthpiece to a certain depth into the trim. This depth can be set using the gas pressure P1 or P2.
• 2. The number of pulses per minute is used to set the characteristic of the flame over the depth into the trim (so-called burning depth). As soon as the flame has reached the burning depth, a steady state is established. If the gas supply is interrupted at this moment, the flame collapses. The temporal course of the rise and decay phase follows an e-function. In conventional ovens, this limit is reached at approximately 120 pulses per minute. Low pulse numbers indicate a longer residence time in the steady state of the flame and therefore a longer energy supply in the lower area of the flame.
• 3. The setting according to point 2 can be set separately for both pressure levels.
• 4. Since less gas flows out at low pressure (flame up), the energy can be adjusted via the "factor" mentioned - for this purpose, only the factor controller has to be actuated, in particular rotated.
• 5. The burning time in the upper and lower burning area can be set separately.

Claims (11)

1.Device (control device) for controlling gas pulse burners of a tunnel furnace used for firing ceramic products (moldings) with a plurality of burner groups in the firing zone, each burner group having a plurality of gas pulse burners to be switched on in succession, i.e. Gas burner with gas supply switched on at intervals (cycles) and the control device switches the individual gas pulse burners into operation in a predeterminable cycle and the pulse length of the respective gas supply (burner activation) and the gas pressure are adjustable, characterized by a burner output setting enabling Gas pulse burner control with microprocessor, in which the duty cycle of each gas pulse burner (2) is switched as an inversion fraction and is adjustable (adjustable). 2. Device according to claim 1, characterized in that a circuit arrangement is present, according to which each gas pulse burner (2) remains on for a time calculated from the preselected number of pulses and the burner on time. 3. Device in particular according to claim 1, characterized in that at least some of the gas pulse burners (2) can be operated with at least two pressure stages (P1, P2) and the switching time and / or frequency of the gas supply can be regulated separately. 4. Apparatus according to claim 3, characterized in that the burning time in the upper firing range, i.e. with low pressure level (P1), and in the lower combustion range, i.e. with high pressure level (P2), can be set separately. 5. The device in particular according to claim 1, characterized in that (a) the gas pulse burner (2) can be operated with two pressure stages (P1, P2) and the switching time and the frequency of the gas supply can be regulated separately and (b) the burning time in the upper firing range, ie with low pressure level (p1), and in the lower firing range, ie with high pressure level (P2), can be set separately. 6. The device in particular according to claim 1, characterized in that at least some gas pulse burners (2) with at least two pressure stages (P1, P2) can be operated, the duty cycle of the gas pulse burner (2) in one pressure stage by means of an adjustable factor - i.e. a percentage change - is changeable. 7. The device according to claim 6, characterized by a circuit arrangement, according to which the duty cycle of the gas operable with at least two pressure stages (P1, P2) pulse burner (2) in the low pressure level (P1) can be extended. 8. The device according to at least one of claims 1 to 7, characterized in that each burner group is connected to a connection and setting device (6), from which a multi-core cable (7) leads to a controller unit (8). 9.The device according to claim 8, characterized in that the connection and setting device (6) comprises all function control elements for a gas pulse burner group. 10.The device according to at least one of the preceding claims, characterized in that the connection and setting device (6) of each burner group is arranged in the vicinity of this burner group. 11.The device according to at least one of the preceding claims, characterized in that the same is designed for reducing firing.

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