EP2761241B1 - Monitoring method - Google Patents

Description

The invention relates to a method for monitoring an operating state of an anode furnace, wherein the anode furnace is formed of a plurality of heating channels and furnace chambers, wherein the furnace chambers for receiving anodes and the heating channels for controlling the temperature of the furnace chambers, wherein the anode furnace at least one furnace unit with a heating zone , a fire zone and a cooling zone, wherein in the heating zone, a suction device and in the fire zone, a burner device is arranged, wherein by means of the burner combustion air is heated in the heating channels of the fire zone, and wherein by means of the suction hot air is sucked out of the heating channels of the heating zone.

The present process finds application in the production of anodes needed for fused-salt electrolysis to produce primary aluminum. These anodes are prepared from petroleum coke with the addition of pitch as a binder in a molding process as so-called "green anodes" or "raw aodes", which are subsequently sintered in an anode furnace in the molding process.

This sintering process takes place in a defined heat treatment process in which the anodes pass through three phases, namely a heating phase, a sintering phase and a cooling phase. Here are the Rohanoden in a heating zone of an assembled from the heating zone, a fire zone and a cooling zone, anode furnace formed "fire" and are preheated by the originating from the fire zone waste heat of already finished sintered anodes before the preheated anodes in the fire zone on the Sintering temperature of about 1200 ° Celsius are heated. According to the prior art, as he, for example, from the EP 1 785 685 A1 or the article " Process Control in an anode bake furnace fired with heavy oil ", by Dr. U. Mannweiler, S. Oderbolz and P. Sulzberger, Light Metals 1991 , it is known, while the various aforementioned zones are defined by a variable continuous arrangement of different units above furnace chambers or heating channels that receive the anodes.
By positioning a burner device above selected furnace chambers or heating channels, the fire zone is defined, which is arranged between the heating zone and the cooling zone. In the cooling zone are immediately before burned, ie heated to sintering temperature, anodes. Above the cooling zone, a blower device is arranged, is blown by means of the air in the heating channels of the cooling zone. The air is passed through an above the heating zone arranged suction through the heating channels from the cooling zone through the fire zone into the heating zone and from this as a flue gas through a flue gas cleaning system and discharged into the environment. The suction device and the burner device together with the blower device and the heating channels form a furnace unit.
The aforementioned aggregates are displaced along the heating channels in the direction of the anode arranged in the anode crucible at regular intervals. Thus, it may be provided that an anode furnace comprises a plurality of furnace units, the aggregates of each other Subsequently, above the furnace chambers or heating channels for subsequent heat treatments of the raw anode or anodes are moved. In such Anodenbrennöfen, which may be designed in different types as an open anode furnace or anode ring furnace, there is the problem that a volume flow of the guided through the anode furnace air can be measured only with unreasonable effort. A determination of the volume flow is needed in particular for the regular monitoring of an operating state of the anode furnace. This is to ensure that sufficient oxygen is available for combustion of a fuel of the burner device in the heating channels of the anode furnace. Since a direct volume flow measurement is not possible due to the meandering, rectangular geometry of the heating channels, an attempt is made to determine the volume flow by an indirect measurement, for example a pressure measurement. However, such an estimation of the volumetric flow often leads to unusable results, for example when a heating channel cover is opened or improperly closed, or a heating channel is blocked or blocked. Even a measurement of the volume flow by means of a Venturi tube leads to unsatisfactory results, since the differential pressures necessary for the measurement can not be established. In practice, therefore, a volumetric flow rate evaluation is carried out by trained oven personnel as part of a kiln tour at regular intervals. If a malfunction of the anode furnace is detected, it is then turned off manually by the furnace personnel. However, this can lead to hazardous operating conditions of the anode furnace, which can lead to deflagration, fires or explosions, may not be detected in time.

Object of the present invention is therefore to propose a method for monitoring an operating condition of an anode furnace, which allows continuous monitoring of the operating condition.

This object is achieved by a method having the features of claim 1.

In the method according to the invention for monitoring an operating state of an anode furnace, the anode furnace is formed from a plurality of heating channels and furnace chambers, wherein the furnace chambers for receiving anodes and the heating channels for controlling the temperature of the furnace chambers, wherein the anode furnace at least one furnace unit with a heating zone, a fire zone and a cooling zone, wherein in the heating zone, a suction device and in the fire zone, a burner means is arranged, wherein by means of the burner means combustion air is heated in the heating channels of the fire zone, being sucked by the suction hot air from the heating channels of the heating zone, wherein a suction of the Suction is determined, and wherein a pressure in the heating channel is measured, wherein from a ratio of suction and pressure, a volume flow in the heating channel is determined.

The suction power of the suction device can be determined relatively reliably, since the suction device indeed causes a volume flow in the heating channels, but is not regulated in direct dependence of the volume flow. Therefore, a suction power of the suction device is set on the assumption that the desired volume flow results therefrom. So it is also possible to determine the suction of the suction easily and accurately. Furthermore, a pressure or a vacuum caused by the suction device is measured in the heating channel. From the ratio of suction power to pressure comparatively accurately the volume flow in the heating channel can be determined. For example, if a Heizkanalabdeckung open or improperly closed or the heating channel is clogged, there is a change in pressure in the heating channel relative to the suction of the suction. The measured pressure in the heating channel thus deviates from a presumed pressure at the same suction power from. From this, a reduced or increased volume flow in the heating channel can be derived. The respectively corresponding size of the volume flow results from a deviation from the presumed volume flow at known suction power and measured pressure. Since the determination of the suction power and the measurement of the pressure in the heating channel can be carried out continuously, via transducers and thus without furnace personnel, it is thus possible to perform a similar monitoring of the operating state of the anode furnace by the continuous determination of the volume flow.

Due to the various embodiments of the method, a pressure or negative pressure in the heating channel in the heating zone and / or the fire zone can be measured. Thus, it is conceivable to carry out a plurality of pressure measurements in the relevant zone or the respective zones in order to quickly determine the position of a malfunction.

It is also possible for a more detailed determination of an operating state, to measure a pressure or negative pressure in, for example, a collecting duct of the suction device. If the suction device is designed such that it spans and is connected to a plurality of heating channels in the transverse direction, the pressure measured in this collecting channel of the suction device can also be used to determine the volume flow. Furthermore, it can also be ensured that there is no malfunction when the suction power and the measured pressure in the suction device is in an expected relationship to each other.

The volume flow can be determined even more accurately if this is determined from a ratio of suction power and pressure in the suction device and the ratio of suction power and pressure in the heating duct. The respective conditions can each be formed separately from each other and the volume flow can be derived therefrom.

Also, a volume flow can be determined individually for individual heating channels, for example, by setting a respective pressure in a plurality of heating channels in relation to the pressure in the suction device. A particularly high or low pressure in a heating channel compared to the other heating channels can already indicate a possible malfunction in the relevant heating channel. Furthermore, a pressure deviation in a heating channel has an effect on the pressures in the other heating channels, so that a correspondingly changed volume flow can also be determined or calculated here with relative reference to the pressure measured in the suction device.

A determination of the suction power of the suction device can be made by determining a flap position of a throttle valve of the suction device. A cross-section of a suction channel can be varied by adjusting the throttle, so that the suction power of the suction device depends inter alia on the set cross-section of the suction channel. Therefore, when using a butterfly valve or similar such device, an exhaust performance may be deduced from a flap position, for example given in degrees of angularity relative to the suction channel. A flap position can be determined particularly simply and accurately, for example by means of a rotary potentiometer.

It is particularly advantageous if the volume flow in the heating channel of the heating zone and / or the fire zone is determined. Since this may result from the combustion process caused flow differences, they can be considered so. Thus, a volume flow in the heating channel of the aforementioned zones can be determined separately from each other. Thus, a more differentiated consideration of the operating state in the respective zones of the anode furnace is possible.

Overall, an operating state can be derived from the ratio of suction power and pressure and / or the specific volume flow. Thus, it is possible to determine, based on the measured data or the volume flow, in which phase of the anode production of the anode furnace or the relevant furnace unit is currently located. For example, the determination of the operating state can be used to determine a point in time for a conversion of the suction device and the burner device and a blower device in more detail.

In a further embodiment of the method, a temperature in the heating channel can be measured. An evaluation of an operating condition is thereby further simplified, since such a required firing temperature can be monitored.

Furthermore, a temperature gradient in the heating channel can also be measured. Accordingly, a temperature profile can be monitored over a period of time, with a falling or rising temperature or a negative or positive temperature gradient allowing conclusions to be drawn on an operating state change.

The temperature gradient and / or the temperature can or can be measured in a collecting channel of the suction device and / or the heating zone and / or the fire zone. The collecting channel or the aforementioned zones each require a specific temperature gradient or temperature range for proper operation of the furnace unit, so that a more precise determination of an operating state becomes possible with metrological monitoring of these plant sections.

Also, the volumetric flow can be determined even more accurately if a change in density of air in the heating channel is calculated from the temperature gradient and the temperature, and this density change is taken into account in the determination of the volumetric flow. Which is through an increase or decrease in a temperature in the heating channel resulting volume change of the air located in the heating channel can significantly affect a flow in the heating channel. A calculation of the volumetric flow can therefore be corrected by a correction factor that can be derived from a calculation of the density change on the basis of temperature gradient and temperature.

From a ratio of temperature gradient and flow rate can also be derived an operating condition. Depending on the volume flow in the heating channel, there is a progressive heating in the heating zone. Consequently, a relationship between temperature gradient and volume flow can be established. For example, a negative or very high temperature gradient in the heating zone at a low flow rate may indicate a blockage of the relevant heating channel. By the ratio formation of temperature gradient and flow rate, therefore, even a possible cause of a malfunction can be determined.

In this context, it is advantageous if the operating state is evaluated, wherein in case of deviation from a presumed operating state, a shutdown of the burner device takes place. Thus it can be avoided that a malfunction of the furnace unit has a possible damage to the same result. The shutdown of the burner device or the entire furnace unit can also be done automatically without furnace personnel must be on site. In this respect, provision may be made for processing of the measured values and operating state variables detected in the context of the monitoring method to take place by means of a data processing device or a corresponding control and regulating device. Thus, the operating state can also be influenced or corrected automatically by an influencing control of the respective units of the furnace unit.

It is also possible to store operating state parameters describing the operating state, wherein an evaluation of the current operating state can be carried out by comparing the stored with the current operating state parameters. In particular, when a device for data processing is used, a continuous comparison of the current operating state parameters with the stored operating state parameters can be performed. In this case, it is possible to define threshold values for the various operating state parameters which trigger a shutdown or corrective control of units.

Advantageously, a plausibility check of transducers can also be carried out before each start or startup or recommissioning of the furnace unit. Thus it can be ensured that after a conversion of the units of the furnace unit, the transducers of the furnace unit are connected to each other in the intended manner. Among other things, it can thus be ensured that, in the event of a malfunction of a measuring transducer, there is no undesirable operating state influencing.

Hereinafter, a preferred embodiment of the invention will be explained in more detail with reference to the accompanying drawings.

Fig. 1:

Eine schematische Darstellung eines Anodenbrennofens in einer perspektivischen Ansicht;

Fig. 2:

eine schematische Darstellung einer Ofeneinheit des Anodenbrennofens in einer Längsschnittansicht;

Fig. 3:

eine Temperaturverteilung in der Ofeneinheit;

Fig. 4:

eine grafische Darstellung des Verhältnisses von Volumenstrom zu Betriebszustandsparametern;

Fig. 5:

eine grafische Verhältnisdarstellung von Volumenstrom zu Temperaturgradient;

Fig. 6:

ein Ablaufdiagramm für eine Ausführungsform des Verfahrens zur Überwachung eines Betriebszustandes.

Show it:

Fig. 1:

A schematic representation of an anode furnace in a perspective view;

Fig. 2:

a schematic representation of a furnace unit of the anode furnace in a longitudinal sectional view;

3:

a temperature distribution in the furnace unit;

4:

a graphical representation of the ratio of flow rate to operating state parameters;

Fig. 5:

a graphical representation of volume flow to temperature gradient;

Fig. 6:

a flowchart for an embodiment of the method for monitoring an operating condition.

A synopsis of Fig. 1 and 2 shows a schematic representation of an anode furnace 10 with a furnace unit 11. The anode furnace 10 has a plurality of heating channels 12 which extend parallel along intermediate furnace chambers 13. The oven chambers 13 serve to receive anodes not shown here. The heating channels 12 are meandering in the longitudinal direction of the anode furnace 10 and have at regular intervals Heizkanalöffnungen 14, which are each covered with a Heizkanalabdeckung not shown here.

The oven unit 11 further comprises a suction device 15, a burner device 16 and a blower device 17. Their position on the anode baking oven 10 defines functionally a heating zone 18, a fire zone 19 and a cooling zone 20. In the course of the production process of the anodes, the oven unit 11 is relative to the Furnace chambers 13 and the anodes shifted by moving the devices 15 to 17 in the longitudinal direction of the anode furnace 10, so that all located in the anode furnace 10 anodes pass through the zones 18 to 20.

The suction device 15 is essentially formed from a collecting channel 21, which is connected via an annular channel 22 to an exhaust gas cleaning system, not shown here. The collecting channel 21 is in turn connected in each case via a connecting channel 23 to a heating channel opening 14, in which case a throttle valve 24 is arranged on the connecting channel 23. Next is a not shown here transducer for pressure measurement within the collection channel 21 and another sensor 25 for measuring temperature in each heating channel 12 arranged immediately in front of the collecting channel 21 and connected via a data line 26 with this. In addition, a measuring ramp 27 with measuring sensors 28 for each heating channel 12 is arranged in the heating zone 18. By means of the measuring ramp 27, a pressure and a temperature in the relevant section of the heating channel 12 can be determined.

The burner device 16 comprises three burner ramps 29 with burners 30 and transducers 31 for each heating channel 12. The burners 30 each burn a flammable fuel in the heating channel 12, wherein a burner temperature is measured by means of the transducers 31. This makes it possible to set a desired burner temperature in the area of the fire zone 19.

The cooling zone 20 comprises the blower device 17, which is formed from a feed channel 32 with respective connection channels 33 and throttle valves 34 for connection to the heating channels 12. Fresh air is blown into the heating channels 12 via the feed channel 32. The fresh air cools the heating channels 12 and the anodes located in the furnace chambers 13 in the region of the cooling zone 20, wherein the fresh air is continuously heated until it reaches the fire zone 19. Of the Fig. 3 For this purpose, a diagram of the temperature distribution based on the length of a heating channel 12 and the zones 18 to 20 can be seen. Furthermore, a measuring ramp 35 with transducers 36 is arranged in the cooling zone 20. The transducers 36 serve to detect a pressure in the respective heating channels 12. In the region of the transducers 36, the pressure in the heating channel 12 essentially assumes the value zero, wherein between the transducers 36 and the fan 17 an overpressure and between the transducers 36 and the Absauginrichtung 15 a negative pressure in the heating channels 12 is formed. Consequently, the fresh air flows from the fan 17 through the heating channels 12 to the suction device 15th

With the example in Fig. 6 the process sequence shown is now a determination of a volume flow of the air and thus an operating condition possible. With reference to the anode furnace after the Fig. 1 and 2 An initial check is made of all transducers 25, 28, 31, 36 as well as of the transducers, not shown here, for determining the position of the throttle flap 24 of the suction device 15. Thus, it can be ensured that no measured values of possibly defective transducers are read out. This test is carried out immediately after the furnace unit 11 has been moved and the devices 15 to 17 have been put into operation again. During operation of the furnace unit 11, a temperature in the heating channel 12 and a temperature gradient are detected by means of the measuring sensor 25 and 28, respectively, these density correction measurements in the heating channel 12 located air or hot air is used. In parallel, a measurement of a position of the respective throttle valves 24, a pressure measurement in the collecting channel 21 and a pressure measurement in the heating channels 12 by means of the transducer 28. From the measured values for the throttle position and the respective measured values for a negative pressure in the collecting channel 21 and in the heating channel 12 in each case formed ratios from which, together with the above-described density correction, a volume flow in the heating channel 12 can be derived. From a ratio of volume flow and temperature gradient in the heating channel 12, an operating state for the volume flow is again determined. Here it is intended to store the corresponding measured values or operating state parameters and thus to calibrate an operating state or to describe a proper operating state. During repetitive operating phases, it is then possible to make a comparison between the calibrated or presumed proper operating state and the current operating state.

This comparison may, for example, as in Fig. 4 represented by comparing a current operating pressure to a throttle valve with a presumed operating pressure. Likewise, it is possible to have a ratio of volume flow and temperature gradient, as in Fig. 5 presented to evaluate. In the example shown, the ratio in a region 37 of the graph could be considered to be proper for the operating state, critical for a region 38, and unsatisfactory for a region 39. These operating states can be signaled, for example, as a graphic representation in the manner of a traffic light or acoustically to an operator.

Claims (16)

1. A method for monitoring an operating status of an anode furnace (10), wherein the anode furnace is formed from a plurality of heating ducts (12) and furnace chambers (13), wherein the furnace chambers serve for receiving anodes and the heating ducts serve for controlling the temperature of the furnace chambers, wherein the anode furnace comprises at least one furnace unit (11) having a heating zone (18), a firing zone (19) and a cooling zone (20), wherein a suction device (15) is arranged in the heating zone and a burner device (16) is arranged in the firing zone, wherein, by means of the burner device, combustion air is heated up in the heating ducts of the firing zone, wherein, by means of the suction device, hot air is sucked out of the heating ducts of the heating zone, wherein a suction output of the suction device is determined, and wherein a pressure is measured in the heating duct,
   characterized in that
   a volumetric flow is determined in the heating duct from a ratio of suction output and pressure.
2. The method according to claim 1,
   characterized in that
   a pressure in the heating duct (12) of the heating zone (18) and/or of the firing zone (19) is measured.
3. The method according to claim 2,
   characterized in that
   a pressure in the suction device (15) is measured.
4. The method according to claim 3,
   characterized in that
   the volumetric flow in the heating duct is determined from a ratio of the suction output and pressure in the suction device (15) and from the ratio of the suction output and pressure in the heating duct (12).
5. The method according to claim 3 or 4,
   characterized in that
   a respective pressure in a plurality of heating ducts (12) is related to the pressure in the suction device (15).
6. The method according to any one of the preceding claims,
   characterized in that
   the suction output of the suction device (15) is determined by determining a throttle position of a throttle (24) of the suction device (15).
7. The method according to any one of the preceding claims,
   characterized in that
   the volumetric flow in the heating duct (12) of the heating zone (18) and/or of the firing zone (19) is determined.
8. The method according to any one of the preceding claims,
   characterized in that
   an operating status is derived from the ratio and/or from the volumetric flow.
9. The method according to any one of the preceding claims,
   characterized in that
   a temperature in the heating duct (12) is measured.
10. The method according to claim 9,
    characterized in that
    a temperature gradient in the heating duct (12) is measured.
11. The method according to claim 10,
    characterized in that
    the temperature gradient and/or the temperature in a collecting duct (21) of the suction device (15) and/or in the heating zone (18) and/or in the firing zone (19) is measured.
12. The method according to claim 10 or 11,
    characterized in that
    a density change of the air in the heating duct (12) is calculated from the temperature gradient and from the temperature, wherein the density change is used for determining the volumetric flow.
13. The method according to any one of the claims 10 to 12,
    characterized in that
    an operating status is derived from a ratio of temperature gradient and volumetric flow.
14. The method according to claim 8 or 13,
    characterized in that
    the operating status is evaluated, wherein, in case of a deviation from a presupposed operating status, the burner device (16) is switched off.
15. The method according to claim 14,
    characterized in that
    operating status parameters that describe the operating status are stored, wherein the current operating status is evaluated by comparing the stored operating status parameters to the current ones.
16. The method according to any one of the preceding claims,
    characterized in that
    before the initiation of operation of the furnace unit (11), a plausibility check of measuring sensors (25, 28, 31, 36) is performed.

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