DE102019129192A1 - Process for the regulated operation of a regeneratively heated industrial furnace, control device and industrial furnace - Google Patents

Abstract

A method for the controlled operation of a regeneratively heated industrial furnace with a furnace space, in particular with a melting tank, in particular for glass, comprising the steps: injecting fuel into the furnace space via at least one fuel injector which is used to inject fuel, in particular with practically no combustion air, - Periodically alternating routing of combustion air on the one hand to the furnace chamber in a first period and on the other hand exhaust gas from the furnace chamber in a second period separately from the fuel by means of a left regenerator and a right regenerator assigned to the at least one fuel injector, which are used for the regenerative storage of heat are formed from the exhaust gas and transfer of heat to the combustion air.

Description

The invention relates to a method for the controlled operation of a regeneratively heated industrial furnace, in particular with a melting tank, in particular for glass, according to the preamble of claim 1 and a control device designed to carry out the method according to the preamble of claim 20. The invention also relates to an industrial furnace according to the preamble of claim 22.

State of the art

In principle, an industrial furnace is not restricted to use in glass production. For example, an industrial furnace of the type mentioned at the outset can also be used in metal production or the like. However, a regenerative industrial furnace of the type mentioned at the beginning has proven to be particularly suitable in glass production for melting glass.

So far, the control of regenerative glass melting furnaces - i.e. H. regularly by means of control via the upper furnace in the furnace room as a controlled system - exclusively entrusted to PID controllers, which aim to regulate an upper furnace temperature and the output of which either represents an amount of fuel itself or an amount of combustion air which the amount of fuel then follows in an adjustable ratio.

The problem with this is that such temperature regulators - as in a method of the DD 143 158 A1 - regularly prove to be unsuitable for successfully and stably regulating the temperature of a regenerative glass melting furnace and thus remain unused. The reason for this lies in the draft regulation that has been pursued to date, which has the systematic tendency to keep increasing slight temperature differences between the regenerators. The fuel consumption between the sides of the fire is also increased further and further, without a setpoint value for the furnace temperature ever being attainable; ie the control does not converge on the setpoint of an oven temperature.

Out DE 36 10 365 A1 a method for the technologically controlled regulation of an upper furnace heating of an industrial furnace is known, in which a fuel flow is provided for regulating a vault temperature of the upper furnace and the problem of a regenerative side asymmetry is left to subjective influences. It has been found that temperature differences in the furnace temperatures between the left-hand and right-hand heating are predominantly due to corresponding temperature differences in the associated regenerators. In individual cases, the head temperatures of the left-hand regenerator can be 45 ° C lower than those of the right-hand regenerator and at the same time the temperatures in the furnace chamber, i.e. regularly in the upper furnace, are 20 ° C lower with left-hand heating than the same temperatures with right-hand heating.

So revealed GB 1,188,256 a method for the controlled operation of a regeneratively heated industrial furnace with a temperature control, wherein a control for a cycle of the fire periods of the burners is provided. For example, a controller can specify control signals as a function of the temperatures in the regenerators when a temperature or a temperature difference has reached a predetermined value.

WO 2012/038488 A1 describes a method of the type mentioned at the beginning for the controlled operation of a regeneratively heated industrial furnace, with temperature control taking place in a first control loop and symmetry control for the left and right regenerators in a second control loop.

WO 2012/038488 A1 in this respect follows a technological control concept that essentially converges to a setpoint value for the furnace temperature and eliminates the problem of side asymmetry in terms of control technology. However, a control technology concept that can be implemented in existing controls with comparatively little effort is also desirable. In particular, such a control-technical solution concept should initially manage without a mandatory additional intervention in the actuators for fuel and combustion air regenerators.

task

This is where the invention comes in, the object of which is to provide an improved method for the controlled operation of a regeneratively heated industrial furnace, in particular with a melting tank, especially for glass, as well as a controller designed for this purpose and an improved regeneratively heated industrial furnace and an improved control device.

invention

With regard to the method, the object is achieved by the invention with a method of the type mentioned at the outset, in which, according to the invention, the features of the characterizing part of claim 1 are also provided. The invention leads to the solution of the object on a control device according to claim 20 and an industrial furnace according to claim 22.

Fuel is to be understood in particular as fuel gas. Other fuels such as oil, e.g. B. heating oil, or the like are also possible to operate an industrial furnace. Mixtures of fuel gas and fuel oil are also possible. An injector is to be understood in particular as an injection device which is designed to inject fuel directly in front of a furnace chamber in a feed path or in the furnace chamber, in particular separately from the combustion air. Mixing of combustion air and fuel is only intended in the furnace. The furnace chamber has in particular an upper furnace and a lower furnace. A lower furnace has, in particular, a glass melting tank or the like.

The designations of the regenerators as left and right regenerators are not to be understood as restrictive with regard to the spatial arrangement of the same and follow general technical usage. The names can also be chosen differently, e.g. B. as a first and second regenerator. The regenerators can be arranged in relation to a glass melting tank in the direction of flow or transversely to the direction of flow of the glass.

A single regenerator can be assigned to a number of injectors. A regenerator can also be understood to mean a regenerator section or the like that is assigned to an individual injector.

The first and second control loops can initially be executed independently of one another and can thus act independently on the controlled system. In a further development, the first and second control loops can also be coupled; z. B. via the temperature controller or the balancing controller.

The concept of the invention is initially based on available upper furnace temperature control methods. A first adjustable manipulated variable in the form of a fuel flow and / or a combustion air flow is set via an actuator assigned to the first controller. It goes without saying that, when the setting is regulated, primarily only the fuel flow is entrained, in particular at a sub-stoichiometric level. It goes without saying that, with a regulated setting, a fuel flow is primarily only carried along with the combustion air, in particular at a sub-stoichiometric level. In principle, two manipulated variables in the form of a fuel flow and a combustion air flow can also be set in a controlled manner, in particular by means of two actuators; this if necessary. Under a boundary condition of z. B. substoichiometric operation.

• - Injizieren von Brennstoff in den Ofenraum über wenigstens einen Brennstoff-Injektor, der zur Injektion von Brennstoff, insbesondere praktisch ohne Verbrennungsluft, ausgebildet ist,
• - periodisch abwechselnde Führung von einerseits Verbrennungsluft zum Ofenraum in einer ersten Periodendauer und andererseits Abgas aus dem Ofenraum in einer zweiten Periodendauer separat vom Brennstoff mittels einem dem wenigstens einen Brennstoff-Injektor zugeordneten linken Regenerator und rechten Regenerator, die zur regenerativen Speicherung von Wärme aus dem Abgas und Übertragung von Wärme auf die Verbrennungsluft ausgebildet sind, wobei

in einer ersten Regelschleife für eine Temperaturregelung:

• - über eine Ofenraumtemperatur als Regelgröße, und
• - einen ersten Regler, insbesondere einen PID-Regler, für die Ofenraumtemperatur, sowie
• - über ein dem ersten Regler zugeordnetes Stellglied eine erste stellbare Stellgröße in Form eines Brennstoffstroms und/oder eines Verbrennungsluftstroms eingestellt wird.

The invention is therefore based on a method for the controlled operation of a regeneratively heated industrial furnace with a furnace chamber, in particular with a melting tank, in particular for glass, having the steps:

• - Injecting fuel into the furnace chamber via at least one fuel injector which is designed for injecting fuel, in particular with practically no combustion air,
• - Periodically alternating routing of combustion air to the furnace chamber on the one hand in a first period and on the other hand exhaust gas from the furnace chamber in a second period separately from the fuel by means of a left regenerator and a right regenerator assigned to the at least one fuel injector, which are used for the regenerative storage of heat from the exhaust gas and transferring heat to the combustion air are formed, wherein

in a first control loop for temperature control:

• - via a furnace chamber temperature as a controlled variable, and
• - A first controller, in particular a PID controller, for the furnace chamber temperature, as well
• - A first adjustable manipulated variable in the form of a fuel flow and / or a combustion air flow is set via an actuator assigned to the first controller.

• - eine Regenerator-Temperatur, insbesondere eine Regeneratorkopf-Temperatur, des linken Regenerators und rechten Regenerators bestimmt wird, und mittels einer Abweichung in den Regenerator-Temperaturen eine Störgröße ermittelt wird, wobei
• - die Störgröße mittels der, insbesondere parallelen und/oder verstärkenden, Regelschleife zur Regelung der Ofenraumtemperatur genutzt wird.

According to the invention, it is provided that in a control loop which extends the first control loop, in particular a parallel control loop for temperature control:

• a regenerator temperature, in particular a regenerator head temperature, of the left regenerator and right regenerator is determined, and a disturbance variable is determined by means of a deviation in the regenerator temperatures, wherein
• the disturbance variable is used by means of the, in particular parallel and / or amplifying, control loop to control the furnace chamber temperature.

In simple terms, a method and devices for regulating the upper furnace temperature of regeneratively heated glass melting furnaces are provided here, with at least partially eliminating the problem of thermally asymmetrical firing (thermal lateral asymmetry) in terms of control technology rather than in addition to temperature control, but rather in a modified temperature control.

The concept of the invention proposes a method and a technological control concept that address the above-mentioned problem of thermal side asymmetry remedies in a control engineering solution; However, this is initially done solely by means of temperature control; nevertheless, based on an extended temperature sensor system, which is no longer restricted to the furnace chamber, is preferably based on an extended temperature sensor system which takes the regenerator head temperatures into account. In particular, the concept of the invention manages within the scope of the extended temperature sensor system with actuator updates provided on the basis of the temperature control.

The invention is based on the consideration that there is usually a destabilizing interrelationship between the left and right regenerators. This can be exemplified as follows: A z. B. by chance a slightly colder left-hand regenerator supplies the stove with slightly less heat from the preheated combustion air - a simple PID controller responds to this by increasing the left-hand fuel and combustion air volume, with the result that a larger amount of exhaust gas enters the right-hand regenerator and heats it up more than before. After an exchange of fire, d. H. With the alternate firing for the industrial furnace from the right regenerator, the right now hotter regenerator delivers more heat with the preheated combustion air into the furnace. The PID furnace temperature controller then reduces the amount of fuel for the right-hand firing and the associated amount of combustion air, and thus less exhaust gas is sent to the left-hand regenerator, which consequently continues to lose temperature. The continuation of the control loop with renewed firing for the industrial furnace from the left regenerator leads to a destabilizing cycle that is only stopped by setting upper or lower limits for the amount of fuel on the fire sides. This is inadequate because it ultimately leads to permanently asymmetrical firing of an industrial furnace.

In addition, the invention has recognized that an additional actuator intervention in the context of an additional symmetry control makes a dominant contribution to eliminating the problem. In particular, can also be a WO 2012/038488 A1 known automatic control of the thermal symmetry of the regenerators can be provided. Their output can, in a particularly preferred development, for. B. actively influence the period times between left-hand and right-hand heating. On the one hand, however, some time is required for implementation of the same and a comparatively high level of effort is required for implementation.

In the context of the considerations explained for the task, the invention is therefore based on the assumption that good progress can already be achieved for a symmetrization of a firing of the furnace chamber with a modified and thereby improved temperature control based on a regenerator head temperature.

Based on this consideration, the invention has recognized that at least the aspects of an efficient approach to a possibly approximately symmetrical firing state, in particular also an acceleration and / or increase in effectiveness, can already be achieved with a modified and thus improved temperature control.

Based on this knowledge, the invention proposes the features of the characterizing part of claim 1, namely, as explained in claim 1, an additional temperature control element which ultimately starts with a manipulation of the temperature control difference, namely based on a regenerator head temperature, which most closely reflects the asymmetry .

A temperature control difference is usually given as the difference between a target temperature value and an actual temperature value - the additional temperature control element sees a temperature difference between the left and right regenerator (or right and left regenerator) based on a regenerator head temperature - in short, an additional addition to the temperature control difference provided on the temperature difference between the target side and the output side; d. H. The concept of the invention adds the temperature difference between the regenerator head temperatures on the opposite side and the origin to the common temperature control difference, which ultimately makes the asymmetry measurable.

Advanced training

Further advantageous developments of the invention can be found in the subclaims and indicate in detail advantageous options for realizing the concept explained above within the scope of the task and with regard to further advantages.

In order to regulate the furnace chamber temperature, it is preferably provided that - a control deviation (dT) of the furnace chamber temperature is determined and the disturbance variable of the furnace chamber temperature is added to the control deviation as the deviation between the regenerator temperatures, and - the first adjustable control variable is set based on the added control deviation Deviation between the regenerator temperatures.

It is preferably provided that the deviation between the regenerator temperatures is determined as an increase in amount relative to the control deviation of the furnace chamber temperature, and / or as a deviation in the regenerator temperatures between the target side and the output side of the left-hand regenerator and right-hand regenerator in relation to the side of the respective fuel Injector is determined.

It is preferably provided that the control deviation of the furnace temperature is determined as the target temperature minus the actual temperature in the furnace and / or the deviation between the regenerator temperatures for the disturbance variable by means of a difference between the regenerator temperature of the target side and the regenerator -Temperature of the outlet side.

It is preferably provided that the disturbance variable is _{amplified to a predetermined power by means of the deviation “ΔT LR} ” or “ΔT _RL ” between the regenerator temperatures and / or is weighted with a predetermined multiplier. In other words, this basis of an additional temperature difference based on preferably a regenerator head temperature is provided with two gain factors within the scope of a particularly preferred development, namely on the one hand a multiplicative weighting and a power weighting, which _{provides the additional temperature control difference "ΔT LR} " or "ΔT _RL ".

It is preferably provided that the regenerator temperature, in particular a regenerator head temperature, is determined as a mean between an upper regenerator temperature and a lower regenerator temperature, in particular the deviation between the regenerator temperatures is determined with the means, in particular by means of a Difference between the regenerator temperature mean of the target side and the regenerator temperature mean of the output side.

The additional temperature control difference can on the one hand be switched on in the event that the asymmetry can be switched on, for example due to an excessively large difference in the preheat supplies, for example above a threshold value. It also has the advantage that due to the additional measurement component "ΔT _LR " or "ΔT _RL " for the case that Δ = 0, this additional temperature control difference in the background becomes more effective or becomes ineffective, depending on the size of " Δ ".

A further training according to WO 2012/038488 A1 has recognized that, in the end, without establishing the thermal symmetry of the regenerators, stable and symmetrical control of the upper furnace temperatures is not possible. In particular, the further development for solving the problem has recognized that the temperature control of the upper furnace according to the first control loop is to be supplemented by an automatic symmetry control, which is set up in the present case by means of the second control loop. A suitable criterion for evaluating the thermal symmetry of the regenerators, which can be defined in the process as the difference between the first and second preheating parameter, is used as the setpoint. A heat transfer between the first and second regenerator is set as the output of the second control loop. The concept of the development according to claim 1 provides as a result an energy balance between the regenerators, which can be readjusted at any time in the second control loop. In principle, this can be done without influencing the fuel and combustion air quantities of the furnace heating according to the first control loop. In particular, it has proven to be advantageous for the operation of the second control loop to continue the first control loop independently or to initially record values achieved there for a run through the second control loop.

The heat content of the combustion air is usually not immediately known. The heat content can, however, be measured indirectly or derived from suitable parameters of a regenerator and / or furnace chamber; parameters such as temperatures or air volumes can be used for this purpose. The parameters can be measured, simulated or calculated; they can also be based on empirical values or taken from characteristic curves. A preheating parameter according to the concept of the further development is basically to be understood as any parameter by means of which a measure for the heat content of the combustion air can be specified; In any case, it can be specified insofar as a comparison variable can be specified for a heat content of the combustion air in the first regenerator and for a heat content of the combustion air in the second regenerator. According to the concept of the development, a suitable criterion for evaluating the thermal symmetry of the regenerators is used as the setpoint value, which can be defined in the process as the difference between the first and second preheating parameters. The criterion is suitable for evaluating how much heat is to be transferred from a first regenerator to a second regenerator in order to establish symmetry between them. As part of a further development, it can be provided, for example, that the actual temperature of the preheated combustion air is continuously determined as a criterion for the symmetry of the regenerators by means of continuous suction measurement and the heat from the preheated air is determined from the product of the result of this measurement with the actual amount of combustion air Combustion air is currently calculated, which is supplied to the furnace chamber with left-hand and right-hand firing.

A heat transfer variable is to be understood as a parameter by means of which an amount of heat can be transferred from a first to a second regenerator. In particular, this is a parameter that influences a heat transport mechanism between the first and second regenerator - via the furnace chamber but (in the balance sheet) without directly influencing it, i.e. H. which only influences a heat transport mechanism between two regenerators spaced apart over the furnace space, without directly influencing the heat content of the furnace space itself. In addition to the heat transfer variables mentioned as preferred in the further developments, which can be implemented alone or in combination, another heat transfer variable can in principle also be used, by means of which an amount of heat can be transferred from a first to a second regenerator. If possible, the transfer should take place directly and with as few losses as possible and while maintaining process stability.

In a particularly preferred development of the method, a first time period is set as the heat transfer variable by which the first period duration (i.e. the period duration of a heat input into the furnace chamber from a regenerator via preheated combustion air) is extended for the hotter of the first and second regenerators and / or for the The first period is shortened when the first and second regenerators are colder. A second period of time can preferably also be set as the heat transfer variable, by which the second period duration (i.e. the period duration of a heat discharge from the furnace chamber into a regenerator via hot exhaust gas) is extended for the colder one of the first and second regenerators and / or for the hotter one of the first and second regenerators second regenerator, the second period is shortened. Preferably the first and second time periods are of the same amount, i. H. even for a shortened or lengthened period, a heat dissipation time on a left regenerator is equal to a heat input time on a right regenerator and vice versa. In principle, however, a first and a second time span can also be different if necessary. In other words, a heat transfer variable is advantageously provided as the manipulated variable, which in a particularly preferred embodiment is formed as a first time span by which the period of regenerative heating on the side of the hotter regenerator is extended in order to transport more heat from this to the colder regenerator, conversely, the period of the colder regenerator is reduced by a first period of time, preferably by the same amount, in order to support its accumulation of stored heat. Particularly preferably, the output of the balancing regulator is formed as a period of time by which the period of heating on the side of the colder regenerator is shortened and / or by which the period of time on the side of the hotter regenerator is lengthened. The aim here is to ensure that heat is transported from the hotter regenerator into the colder regenerator, while as far as possible it is avoided that a colder regenerator heats up at the expense of the furnace chamber.

In other words, the concept of the development leads in a preferred development to a method for regulating the upper furnace temperature of regeneratively heated glass melting furnaces in which a temperature controller known per se, e.g. B. PID controller, for controlling a representative upper furnace temperature, has an output for a fuel energy and is linked to a second controller that actively corrects the thermal symmetry between the regenerators so that both regenerators deliver the same heat from preheated combustion air into the furnace chamber . Only with a thermal symmetry of the regenerators produced in this way is the temperature control of the upper furnace even possible, which was recognized by the further development.

The second adjustable manipulated variable is preferably set in the form of a heat transfer variable influencing the heat transfer between the first and second regenerator in order to limit the difference between the first and second preheating parameter to a threshold value close to zero. Advantageously, the amounts of time at the output of the symmetry control are tightly limited in order to enable a gradual transport of the heat, if possible without any significant influence on the entire furnace process. Is z. If, for example, the permissible time shift is limited to 30 seconds over the above-mentioned time period at the output of the symmetry controller, the temperature equalization between the regenerators can take several days up to a week when the regenerators are activated for the first time and if there is an unbalance, it then occurs again if the conditions are otherwise symmetrical Values back around zero.

The difference between the first and second preheating parameters can advantageously be used as the control result of the second control loop for evaluating the state of the regenerator and / or for evaluating a further influencing variable, in particular for evaluating an uncontrolled ingress of air in the furnace chamber and / or regenerator. It is thus advantageously possible to use the control result of the symmetry controller for the technological evaluation of the state of the regenerator or to use to evaluate any asymmetry of further external influencing variables, e.g. B. to evaluate and decide whether uncontrolled air ingress into the furnace chamber or into the regenerator has taken place. If, according to the knowledge of the further training with regenerator temperatures regulated for symmetry, a permanent imbalance of the period times is necessary to maintain the symmetry, an indirect measurement is obtained in this way, which gives an indication of another one-sided influence, e.g. . B. a one-sided infiltration of uncontrolled air in the furnace or in the regenerator or an asymmetrical state of wear of the regenerators.

In a particularly preferred development, the preheating parameter is formed as heat from preheated combustion air, the heat from preheated combustion air being advantageously obtained from a model calculation of the regenerator. The ideal criterion for evaluating the thermal symmetry of the regenerators is therefore the heat of the preheated combustion air, expressed as the energy flow in (MW) that enters the furnace chamber from the regenerator. This energy flow is regularly not available as a measured value. In the present case, this can advantageously be supplied by a mathematical model of the regenerator. For example, a mathematical model in the furnace control can be used as a criterion for the symmetry of the regenerators, which currently calculates the heat from preheated combustion air as a process variable that is fed to the furnace chamber with left-hand and right-hand firing. This mathematical model can e.g. B. be embedded in a software of the control device for the furnace control and approximate and remain approximated by a one-time basic adjustment and self-learning adjustment to specifications through real measured values from existing thermocouples at the regenerator head and at the regenerator foot. Such a model advantageously supplies the input and output flows of thermal energy into and out of a first and second regenerator, as well as the heat made available to the furnace in each case. The model calculation can advantageously be carried out in real time in a control device. This can preferably - in view of the comparatively slow temperature dynamics of the industrial furnace - also be used to calculate the dynamic behavior of air and / or exhaust gas flows and the associated temperature behavior as well as heat input and output in advance.

In an additional or alternative measure, the preheating parameter can be formed as the product of an amount of combustion air and a regenerator head temperature, the amount of combustion air and / or regenerator head temperature being advantageously measured. In particular, a lowest regenerator head temperature is used as the regenerator head temperature. In other words, the product of the amount of combustion air and the lowest chamber head temperature at the end of a respective air and firing period can be used as a criterion for the symmetry of the regenerators. This can be more inaccurate compared to a model calculation, since experience has shown that the real temperature of the preheated combustion air temperature is typically around 50 ... 100 ° C below the lowest thermocouple temperature in the regenerator head, because the thermocouple always shows a mixed temperature of the stone temperature and the air temperature. On the one hand, however, this can be taken into account as a correction and, on the other hand, the mentioned development has proven to be advantageous if the above-mentioned model is not available or the computing capacity of a furnace control is insufficient. The product of the amount of combustion air and the lowest regenerator head temperature at the end of the respective air and firing period can then be used as a simplified criterion for the thermal symmetry of the regenerators.

The preheating parameter is advantageously formed as an average of at least one regenerator head temperature and / or furnace chamber temperature, in particular at the end of a first period and / or a second period, in particular as a weighted average of a highest and a lowest value thereof. In particular, a weighted average of the highest and lowest regenerator head temperatures and the associated upper furnace temperatures at the end of the exhaust gas period and the air period can be used as a criterion for the symmetry of the regenerators. This advantageously increases the reliability of the measured values in relation to the actual temperature values. The furnace chamber and / or a regenerator is preferably provided with a number of temperature sensors, in particular thermocouples, in order to detect, in particular, an upper furnace temperature and / or regenerator head temperature.

To assess the thermal symmetry of the regenerators, a weighted average of the upper and lower temperature peaks of thermocouples of all other temperature sensors on the regenerator head can be used as the simplest criterion, in particular recorded at the end of the period and / or advantageously smoothed by averaging over several periods. Although this may be inaccurate compared to a model calculation, it is mainly for the case different amounts of combustion air on the fire sides, even with this simplified method, a significant improvement over an unregulated state is achieved. In particular, the controllability of the upper furnace for temperature control can be achieved at all.

In particular, a representative furnace chamber or upper furnace temperature can be formed as a weighted average of various temperature measurements. A furnace chamber temperature is particularly advantageously formed as a weighted average of a number of temperature measurements at different locations. The agent is advantageously used as the basis for an advantageous extrapolation of a furnace chamber or upper furnace temperature.

As part of a particularly preferred development, an extrapolation of a furnace chamber temperature, in particular an upper furnace temperature, is carried out to a corresponding furnace temperature at the end of the first and / or second period, in particular on the basis of a modeled time curve of a representative furnace chamber temperature, especially an upper furnace temperature. An extrapolation of a furnace space temperature to a furnace space temperature is particularly preferably carried out at the end of each period. When combustion air is extracted from a regenerator within a first period, its temperature should indeed fall while that in the furnace chamber should rise; then, when exhaust gas is taken up in the same regenerator within a second period, its temperature should rise while that in the furnace chamber should continue to rise. A course of the furnace chamber temperature during each of the periods mentioned can be extrapolated at the end of the period duration. So z. B. from the analysis of the typical temporal course of the representative upper furnace temperature, a prediction of the setpoint of this temperature at the respective end of a fire period of the regenerative heating - each from the left and right side - is formed, which instead of the current temperature value, the prediction temperature Forms the setpoint of the temperature controller. Advantageously, the furnace control records the upper and lower peak temperatures at the beginning and end of each temperature drop caused by changes and, based on this simple model of the temperature profile, provides a prediction of the end-of-period temperature at any time.

The further development has recognized that a temperature drop after changing the regenerator cannot be compensated for by the temperature controller, since this temperature drop, on the contrary, would only have the effect of disrupting the recording of measured values; consequently it is filtered out of the controller by the development. In order to prevent an undesired reaction of the temperature controller to the temperature drop after reversing, the temperature prediction for the end of the period is used as the controller input for the temperature controller instead of the current setpoint of the furnace temperature. Long before the real temperature actually reaches the end of the period, the temperature controller can use the prediction for the end of the period to recognize whether the temperature is rising too quickly or too slowly and can begin to intervene in terms of control technology much earlier.

Preferably, after a temperature drop in the first control loop caused by the periodically alternating guidance, a first adjustable manipulated variable in the form of a fuel flow and / or a combustion air flow is set via an actuator assigned to the first controller, and an additional charge of the same is supplied to the furnace. In particular, the surcharge is formed from the amount of the fuel failure caused by the change and / or from a rate of temperature increase after alternating guidance. This leads to an accelerated increase in the furnace temperature after the drop in temperature caused by changes. Preferably, an additional surcharge on the fuel energy of the furnace is added specifically to the fuel energy as the controller output of the temperature controller, whereby this surcharge itself was not previously the result of the temperature control, but is formed from the amount of the alternating fuel failure and the speed of the temperature increase after reversal.

In the context of a particularly preferred alternative or additional development, it is provided that the heat transfer variable is an increase in the combustion air flow or another fluid caused by the hotter regenerator, in particular independently of a change in the fuel flow. For this purpose, the output of the balancing regulator preferably causes an increase in the flow of combustion air or another fluid through the hotter regenerator with the aim of extracting additional heat from this hotter regenerator, regardless of whether the amount of fuel is changed in the same way or not. As a result, an increase in the heat transport medium is advantageously achieved. The preferred use of the other fluid includes, in particular, an increase in the flow of another inert gas, ie a gas that does not promote the combustion of the fuel. This can for example be a gas such as N ₂ or CO ₂ . An inert gas has the advantage that it supports the heat transport from a left to a right regenerator, but leaves the combustion process and thus the heat content in the furnace interior largely unaffected.

As part of a particularly preferred alternative or additional development, it is provided that a reduction in the combustion air flow or another fluid is caused by the colder regenerator as the heat transfer variable, in particular independently of a change in the fuel flow, preferably the output of the balancing regulator causes a reduction in the flow of combustion air or another fluid through the colder regenerator, with the aim of removing less heat from this colder regenerator, regardless of whether the amount of fuel is changed in the same sense or not. As a result, a reduction in the heat transport medium is advantageously achieved.

The heat transport medium is to be understood in particular as the combustion air or exhaust gas, e.g. B. in a recirculation circuit. A third medium can also be used as a heat transport medium, e.g. B. an additionally added amount of oxygen, nitrogen or other inert gas.

Embodiments of the invention will now be described below with reference to the drawing. This should not only necessarily represent the exemplary embodiments true to scale; rather, the drawing, where useful for explanation, is in a schematic and / or slightly distorted form. With regard to additions to the teachings that can be seen directly from the drawing, reference is made to the relevant prior art. It must be taken into account that various modifications and changes relating to the shape and detail of an embodiment can be made without deviating from the general idea of the invention. The features of the invention disclosed in the description, in the drawing and in the claims can be essential for the development of the invention both individually and in any combination. In addition, all combinations of at least two of the features disclosed in the description, the drawing and / or the claims fall within the scope of the invention. The general idea of the invention is not restricted to the exact form or the detail of the preferred embodiment shown and described below or restricted to an object which would be restricted in comparison to the object claimed in the claims. In the case of specified measurement ranges, values lying within the stated limits should also be disclosed as limit values and be able to be used and claimed as required.

• 1 eine schematische Darstellung eines regenerativ beheizten Industrieofens mit einem linken und einem rechten Regenerator gemäß einer besonders bevorzugten Ausführungsform, bei der eine Steuereinrichtung mit einer Regelschleife IA eines Temperaturregelmodul und einem Symmetrieregelmodul gemäß dem Konzept der Erfindung vorgesehen ist, wobei die Regelschleife IA als eine erweiterte Regelschleife IB eines Temperaturregelmoduls 200 in der Lage ist, die Unsymmetrie einer unsymmetrischen Ofenbefeuerung jedenfalls erkennbar macht;
• 2 zeigt eine besondere Ausführung eines Regelschemas, das allein aufgrund einer erweiterten Regelschleife IB eines Temperaturregelmoduls 200 in der Lage ist, die Unsymmetrie einer unsymmetrischen Ofenbefeuerung --erkennbar durch Δq bzw. ΔT_LR -aufzuheben. Dazu ist ein zusätzliches Temperaturregelmodul R_T+ vorgesehen, dass zu der üblichen Temperaturregeldifferenz ΔT=TSoll-T ist, eine mit Verstärkungsfaktoren versehene zusätzliche Temperaturregeldifferenz „+/-k*ΔT_LR“ hinzuaddiert zur Bestimmung eines Heizwertes. Der Faktor ΔT_LR bzw. ΔT_RL kann zusätzlich potenziert werden mit einem Potenzglied N, das als Beschleunigungsglied gesehen werden kann, um den Effekt einer schnellen Heranführung an einen symmetrischen Zustand zu beschleunigen.
• 3 eine schematische Darstellung einer ersten Regelschleife IA für eine Temperaturregelung des Temperaturregelmoduls und einer zweiten Regelschleife für eine Symmetrieregelung des Symmetrieregelmoduls bei der Steuereinrichtung der 1 gemäß dem Konzept der Weiterbildung nach WO2012/038488 A1 - gemäß dem Konzept der Erfindung kann die erste Regelschleife IA durch die erweiterte Regelschleife IB für das Temperaturregelmodul 200 ergänzt werden und damit die erste Regelschleife IA mit der erweiterten Regelschleife IB und eine zweite Regelschleife für eine Symmetrieregelung des Symmetrieregelmoduls zur Verfügung stehen;
• 4 eine beispielhafte Darstellung eines zeitlichen Verlaufs einer gemessenen Temperatur in einem Regeneratorkopf bei einem Industrieofen der 3 zusammen mit einem modulierten zeitlichen Verlauf einer repräsentativen niedrigsten Regeneratorkopf-temperatur und dazu gehöriger extrapolierter Regeneratorkopftemperatur am Ende einer Periodendauer - dies in Darstellung zusammen mit einem Ofendruck, einer Klappenstellung für Verbrennungsluft sowie einem Sauerstoffanteil des Abgases und einer den symmetrisch eingeschwungenen Zustand des Systems darstellenden ausnivellierten Höhe eines Energieeintrags aus linkem und rechtem Regenerator am Ausgang des Temperaturreglers wie dies gemäß dem Konzept der Weiterbildung in WO 2012/038488 A1 beschrieben ist - mit der erweiterten Regelschleife IB gemäß dem Konzept der Erfindung ist die Temperaturregelung noch effizienter;
• 5 den zeitlichen Verlauf eines Unterschieds der ersten und zweiten Vorwärmekenngröße in Form jeweils einer Wärme aus vorgewärmter Verbrennungsluft im weitgehend eingeschwungenen symmetrischen Zustand des Systems aus linkem und rechtem Regenerator zusammen mit einer eingestellten Zeitspanne als Wärmeübertragungsgröße gemäß der für den kälteren Regenerator eine Periodendauer zur Abführung von Abgas aus dem Ofenraum verlängert und/oder für den heißeren Regenerator eine Periodendauer zur Abführung von Abgas aus dem Ofenraum verkürzt ist gemäß dem Konzept der Weiterbildung nach WO 2012/038488 A1 - mit der erweiterten Regelschleife IB gemäß dem Konzept der Erfindung ist die Temperaturregelung noch effizienter.

Further advantages, features and details of the invention emerge from the following description of the preferred exemplary embodiments and with reference to the drawing; this shows in:

• 1 a schematic representation of a regeneratively heated industrial furnace with a left and a right regenerator according to a particularly preferred embodiment, in which a control device is provided with a control loop IA of a temperature control module and a symmetry control module according to the concept of the invention, the control loop IA as an extended control loop IB a temperature control module 200 is able to make the asymmetry of an asymmetrical furnace firing recognizable;
• 2 shows a special embodiment of a control scheme that is based solely on an extended control loop IB of a temperature control module 200 is able to eliminate the asymmetry of an asymmetrical furnace firing - recognizable by Δq resp. ΔT _LR -to be repealed. For this purpose, an additional temperature control _{module R T} + is provided that, in addition to the usual temperature control difference ΔT = Tset-T, an additional temperature control difference provided with gain factors “+/- k * ΔT _LR ” is added to determine a calorific value. The factor ΔT _LR or ΔT _RL can also be raised to the power with a power term N , which can be seen as an accelerator to accelerate the effect of a rapid approach to a symmetrical state.
• 3 a schematic representation of a first control loop IA for temperature control of the temperature control module and a second control loop for symmetry control of the symmetry control module in the control device of FIG 1 according to the concept of continuing education WO2012 / 038488 A1 - According to the concept of the invention, the first control loop IA can be replaced by the extended control loop IB for the temperature control module 200 are supplemented and thus the first control loop IA with the extended control loop IB and a second control loop for a symmetry control of the symmetry control module are available;
• 4th an exemplary representation of a time profile of a measured temperature in a regenerator head in an industrial furnace of FIG 3 together with a modulated temporal course of a representative lowest regenerator head temperature and the associated extrapolated regenerator head temperature at the end of a period - this in the representation together with a furnace pressure, a flap position for combustion air as well as an oxygen content of the exhaust gas and a leveled height representing the symmetrical steady state of the system an energy input from the left and right regenerator at the output of the Temperature controller like this according to the concept of training in WO 2012/038488 A1 is described - with the extended control loop IB according to the concept of the invention, the temperature control is even more efficient;
• 5 the temporal progression of a difference between the first and second preheating parameters in the form of heat from preheated combustion air in the largely steady symmetrical state of the system of left and right regenerators together with a set period of time as the heat transfer variable according to the period for exhaust gas removal for the colder regenerator the furnace chamber is extended and / or for the hotter regenerator a period for discharging exhaust gas from the furnace chamber is shortened according to the concept of the development according to WO 2012/038488 A1 - With the extended control loop IB according to the concept of the invention, the temperature control is even more efficient.

1 shows a simplified representation of a regeneratively heated industrial furnace 100 with an oven room 10 , its upper furnace room 1 is regulated as a controlled system and in which the lower furnace space 2 has a glass melting tank not shown in detail. Glass contained in the glass melting tank is poured over the furnace chamber 10 heated above the melting temperature and melted and suitably treated for the production of flat glass or the like. The industrial furnace 100 is presently heated by several laterally attached fuel injectors 20th Fuel, present in the form of fuel gas, into the upper furnace 1 is injected. From the fuel injectors 20th in the present case is a left injector 20th shown. From further fuel injectors 20 ' is in the present case a right injector 20 ' shown. For the sake of simplicity, the same reference symbols are used below for the same or similar parts or those with the same or similar function. For example, there can be a number of six injectors on the left or on the right 20th , 20 ' be provided. In the in 1 The firing period shown is via a fuel injector 20th Fuel gas in the upper furnace 1 injected practically without combustion air. Above the fuel injector 20th becomes preheated combustion air VB via an opening on the left 30th the upper furnace 1 fed. The combustion air from the opening 30th mixes in the upper oven 1 with the one from the fuel injector 20th injected fuel gas and leads to the formation of a flame covering the lower furnace 40 , which is shown symbolically in the present case. The picture of 1 shows the industrial furnace 100 in the state of regenerative lighting via the left regenerator 50 and the left injectors 20th . This and the opening 30th is designed in such a way that this is done via the injectors 20th Fuel gas supplied in a sufficiently close or below stoichiometric range with combustion air from the left-hand regenerator in the upper furnace 1 is mixed. The in 1 The operating status shown of a left-side lighting of the upper furnace 1 while injecting fuel gas via the injectors on the left 20th and supply of combustion air VB via the left regenerator 50 lasts for a first period of z. B. 20 to 40 minutes. Combustion air is used during this first period VB to the upper furnace 1 in the furnace room 10 separate from the fuel gas 20th fed. During the first period, exhaust gas AG is released from the upper furnace 1 via openings on the right-hand side 30 ' the right regenerator 50 ' and heats it up.

In a second operating state, the upper furnace is lit for a second period of a similar length 1 vice versa. Combustion air is then used for this purpose VB via the right regenerator 50 ' the upper furnace 1 together with fuel gas from the right injectors 20 ' supplied, with the combustion air VB then that of the exhaust gas AG in the first period in the regenerator 50 ' absorbs deposited heat.

The regulation of a fuel flow and / or a combustion air flow takes place in principle via a temperature control module 200 a control device 1000 for the industrial furnace 100 . Basically, a PID controller in the temperature control module can be used for this 200 are used, according to which a furnace chamber temperature is increased with an increase in the fuel flow and / or the combustion air flow or a furnace chamber temperature is decreased with a decrease in a fuel flow and / or a combustion air flow. The temperature control module 200 are temperature values of the regenerator head 51 or. 51 ' or the upper furnace room 1 using suitable temperature probes 52 , 52 ' , 53 which in the present case are in any case partly also combined with a suitable lambda probe for measuring a fuel-air ratio. In particular the one via the temperature probe 53 The measured temperature in the upper furnace serves as the input of the temperature control module 200 , e.g. B. to make a temperature averaging based thereon and an extrapolation of the temperature behavior to the end of a period.

In particular, the in 1 temperature probes shown 52 , 52 ' and in this case also the temperature probe 53 also deliver measured temperatures to the input of a symmetry control module 300 the 1 - This becomes in the context of an embodiment of this preferred development relating to a symmetry control module in relation to 3 explained in more detail. In particular, the temperatures at a regenerator head such as from the temperature probes 52 , 52 ' measured, can be used as the basis of a claimed simplified determination of a Serve preheating parameter. The lambda probes or other measuring sensors, which may be arranged in the same place, can also record measured values, e.g. B. on air or exhaust gas quantities, provide for such a simplified determination.

2 schematically illustrates the structure of a first rain loop IA for temperature control of a temperature control module 200 . This is done using a preferred embodiment of a method for the regulated operation of the in 1 exemplary shown regeneratively heated industrial furnace 100 explained. With IA The designated first control loop represents the temperature control.

For the control loops I. The upper furnace is used first 1 in the furnace room 10 of the furnace 100 as part of the controlled system R denoted by R. The controlled system R also includes the left regenerator 50 and the right regenerator 50 ' as well as the locations of the regenerators 50 , 50 ' provided heat Q _Li and Q _Re from preheated combustion air VB that the upper furnace 1 are fed. In the real sense, it is a matter of heat flows that occur in the 2 are shown with appropriate symbols.

The aim of furnace temperature control is to determine the amount of fuel that will ensure the technologically desired furnace temperature as predictively as possible - and this with changing loads and changing disturbance variables.

In the present case, the process value is the prediction of the temperature at the end of the period, which is provided by a model of the temperature profile and enables control intervention even if the temperature has not yet reached the end temperature, but falls short of the planned temperature rise or unexpectedly leads it. This is applied accordingly to a weighted average of several oven temperatures.

For the first control loop IA and the expanded control loop IB, which is yet to be explained, initially uses a furnace chamber temperature T as a control variable. For this purpose, several representative upper furnace temperatures T ₁ , T ₂ ... T _N z. B. with suitable temperature sensors 52 , 52 ' , 53 measured with appropriate correction if necessary. The temperature sensor is used in particular 53 for recording the furnace chamber temperature T. The temperature values from the various temperatures T ₁ , T ₂ .. T _N, which are adapted to an upper furnace temperature, are stored in an averaging unit 201 for the formation of a weighted temperature mean T _x averaged. Then the value of the temperature mean T _x an extrapolation unit 202 supplied, which is able to predict the actual value of the temperature in accordance with a typical time course of the representative upper furnace temperature T _IS at the end of a fire period of regenerative heating. Instead of the current temperature value T _x forms this predicted temperature T _IS the actual value of the temperature controller R _T. The temperature _{controller R T} is in the present case in the form of a PID controller, which also has a setpoint value for the temperature T _SHOULD is supplied and determines a fuel energy requirement E from the difference between them.

wobei

T(t)

der angenäherte Temperaturverlauf

T0

der Temperaturtiefpunkt nach Umsteuerung

Tunendlich

die Temperatur nach sehr langer Zeit

t

die Zeit und

t0

eine Zeitkonstante, hier als Formfaktor bezeichnet.

Regarding the extrapolation unit 202 it is considered here that, depending on the installation position, the temperature sensor 52 , 52 ' , 53 in the upper furnace 1 or regenerator head 51 , 51 ' and depending on the duration of a reversal process, the upper furnace temperatures T drop. This applies in particular to the temperature sensor 53 in the context of the following explanation. This means that the real value of the temperature T for the temperature _{controller R T of} the upper furnace temperature falls by 3 - 20K during the reversal and is then built up with continuous heating. The temperature T mostly follows a time curve that can be described by a function: $$\text{T}\left(\text{t}\right)={\text{<figure-callout id="0" label="T" filenames="DE102019129192A1\_0004.png,DE102019129192A1\_0006.png" state="{{state}}">T</figure-callout>}}_0+\left({\text{T}}_{\text{infinite}}-{\text{T}}_0\right)*\left(1-\text{exp}\left[{\text{t / t}}_0\right]\right)$$

in which

T (t)

the approximate temperature curve

T0

the temperature low point after reversing

At least

the temperature after a very long time

t

the time and

t0

a time constant, referred to here as a form factor.

From the temperature extrapolated in this way T _IS At the end of a firing period of the regenerative heating, a fuel energy E is determined that is to be fed to the furnace.

Taking into account a calorific value of the fuel gas used, this becomes a fuel quantity B in a fuel unit 203 certainly. The fuel unit 203 sets an _{actuator assigned to the temperature controller R T} - for example in the form of a fuel throttle for an injector 20th , 20 ' - To set a fuel flow as the first adjustable manipulated variable for an upper furnace so that a desired target temperature TSOLL in contrast to the aforementioned actual temperature T _IS is achieved.

For clarification, reference is made in the following to 4th , in which, in addition to the furnace pressure P, the flap position K for setting the combustion air supply to the left and right regenerators 50 , 50 ' and the oxygen content O of the exhaust gas AG with the temperature sensor 53 measured and obtained temperature means T _x compared to that from the forecast model of the extrapolation unit 202 resulting temperature signal for the actual temperature T _IS is shown. From the forecast unit 202 is at the beginning according to the formula shown above t _B and end t _E every alternating temperature drop in temperature T detects the upper and lower peak temperatures. From this, on the basis of the above-mentioned formula of the temperature profile, a prediction of the period end temperature is provided at any time, which is the actual temperature T _IS for the control loop IA is used. The period duration t is between the beginning t _B and end t _E denotes any temperature drop caused by fluctuations. The described temperature drop after a change at the beginning t _B and at the end t _E the period t can through a temperature controller R _T in any case, cannot be fully offset.

This temperature drop that occurs in 4th With ΔT on the contrary, it would only act like a disturbance in the measured value acquisition and in the present case is logically derived from the temperature controller R _T filtered out to an undesirable reaction of the temperature controller R _T on the temperature drop ΔT after changing the lighting from the left regenerator 50 to the right regenerator 50 ' and vice versa to prevent. Instead of the current real value of the temperature mean T _x consequently becomes the predicted temperature T _IS to the end of the period as a controller input for the temperature controller R _T used. Long before the real temperature T _x actually reaches the period end value, the temperature controller can R _T recognize from the prediction for the end of the period whether the temperature is rising too quickly or too slowly and can begin to intervene in terms of control technology much earlier.

Based on this consideration, it was recognized that in any case the aspects of an efficient approach to a possibly approximately symmetrical firing state, in particular also an acceleration and / or increase in effectiveness, can already be achieved with a modified and thus improved temperature control.

On the basis of this knowledge, it has been proposed in the present case to provide an additional temperature control element which ultimately starts with a manipulation of the temperature control difference, namely based on a regenerator head temperature which most closely reflects the asymmetry.

A temperature control difference is usually given as the difference between a target temperature value and an actual temperature value - the additional temperature control element sees a temperature difference between the left and right regenerator (or right and left regenerator) based on a regenerator head temperature - in short an additional addition to the temperature control difference provided on the temperature difference between the target side and the output side; d. H. The concept of the invention adds the temperature difference between the opposite side and the origin to the common temperature control difference, which ultimately makes the asymmetry measurable.

FIG. 2 shows a special embodiment of a control scheme that is based solely on an extended control loop IB of a temperature control module 200 is able to detect the asymmetry of an asymmetrical furnace firing - recognizable by ΔQ or. ΔT _LR - in any case to be largely canceled. Provision is made for a control deviation ΔT = Tset-Tact of the furnace chamber temperature and the disturbance variable to be determined in order to regulate the furnace chamber temperature ΔT _LR the furnace chamber temperature is added as the deviation between the regenerator temperatures to the control deviation, and the first adjustable manipulated variable is set on the basis of the deviation between the regenerator temperatures T _LR added to the control deviation.

In the present case, the deviation between the regenerator temperatures is determined as increasing in magnitude to the control deviation ΔT = Tset-Tact of the furnace chamber temperature, namely here as the deviation of the regenerator temperatures between the target side and the output side of the left-hand regenerator 50 and right regenerators 50 ' in relation to the side of the respective fuel injector 20th , 20 ' . For this purpose it is provided that the control deviation ΔT the furnace chamber temperature as the setpoint temperature minus the actual value temperature in the furnace chamber and for the disturbance variable the deviation between the regenerator temperatures is determined by means of a difference between the regenerator temperature of the target side and the regenerator temperature of the output side.

For this purpose, an additional temperature control _{module R T} + is provided that, to the usual temperature control difference ΔT = Tset-Tist, adds an additional temperature control difference “+/- k * ΔT _LR ” provided with gain factors to determine a calorific value.

The factor ΔT _LR or ΔT _RL can also be raised to the power with a power term N , which can be seen as an accelerator, to achieve the effect of a rapid approach to a accelerate symmetrical state. It is provided here that the disturbance variable by means of the deviation ΔT _LR , ΔT _RL between the regenerator temperatures to a predetermined power N is amplified and / or weighted with a predetermined multiplier k. In other words, this basis of an additional temperature difference based on preferably a regenerator head temperature is provided with two gain factors within the scope of a particularly preferred development, namely on the one hand a multiplicative weighting, which is designated here with “k”, and a power weighting, which determines the additional temperature control difference “ΔT _LR "or" ΔT _RL "provides.

It is preferably provided in the present case that the regenerator temperature, in particular a regenerator head temperature T _L , T _R , is determined as the mean (T_Max + T_Min) / 2 between an upper regenerator temperature and a lower regenerator temperature, in particular the deviation between the regenerator temperatures is determined with the mean, in particular by means of a difference between the regenerator temperature mean the target side and the regenerator temperature mean of the output side.

The additional temperature control difference can on the one hand be switched on in the event that the asymmetry can be switched on, for example due to an excessively large difference in the preheat supplies, for example above a threshold value. It also has the advantage that due to the additional measurement component "ΔT _LR " or "ΔT _RL " for the case that Δ = 0, this additional temperature control difference in the background becomes more effective or becomes ineffective, depending on the size of " Δ ".

In the 1 control device shown 1000 also has the aforementioned symmetry control module 300 on, which is formed in the present case, the heat transfer between the first and second regenerator 50 , 50 ' to influence. In the present case, this takes place via a heat transfer variable in the form of a time span ± Δt by which for the colder one of the first and second regenerators 50 , 50 ' the second period t extended and / or for the hotter of the first and second regenerators 50 , 50 ' the second period t is shortened or for the colder of the first and second regenerators 50 , 50 ' the first period t shortened and / or for the hotter of the first and second regenerators 50 , 50 ' the first period t is extended. A suitable actuator in the form of a timer 60 is present with the symmetry control module 300 coupled and able to set the first and second period duration t depending on the requirements of the symmetry control module 300 to shorten or lengthen - the latter is due to the period duration by the time span ± Δt for the left regenerator 50 or right regenerator 50 ' moving arrows 61 is represented symbolically.

In relation to 3 now becomes the first control loop I. of the temperature control module 200 and the second control loop II of the symmetry rule module 300 described in more detail as well as the structure of a second control loop II for a symmetry control for a symmetry control module 300 concerning the left and right regenerators 50 , 50 ' . 3 thus schematically illustrates the structure of a first rain loop I. for temperature control of a temperature control module 200 as well as the construction of a second control loop II for a symmetry control for a symmetry control module 300 concerning the left and right regenerators 50 , 50 ' .

This is done using a preferred embodiment of a method for the regulated operation of the in 1 exemplary shown regeneratively heated industrial furnace 100 explained. With I. The designated first control loop represents the temperature control.

With II The designated second control loop provides the symmetry control for the left and right regenerators 50 , 50 ' represent.

For both control loops I. , II The upper furnace is used first 1 in the furnace room 10 of the furnace 100 as part of the controlled system R denoted by R. The controlled system R also includes the left regenerator 50 and the right regenerator 50 ' as well as the locations of the regenerators 50 , 50 ' provided heat Q _Li and Q _Re from preheated combustion air VB that the upper furnace 1 are fed. In the real sense, it is a matter of heat flows that occur in the 3 are shown with appropriate symbols.

The aim of furnace temperature control is to determine the amount of fuel that will ensure the technologically desired furnace temperature as predictively as possible - and this with changing loads and changing disturbance variables.

The prerequisite for controllability is the active maintenance of thermal symmetry, which is achieved by means of the second control loop II is achieved, which is explained below.

A stable, even flow of fuel without unnecessary fluctuations is another prerequisite for efficient heating. It should therefore not be the task of the temperature controller to prevent the inevitable drop in temperature of the vault during about 35 .. 40 seconds of fire-free time of reversal through increased use of fuel wanting to compensate - another reason why a simple PID controller cannot completely solve the task in any case

Asymmetrical furnace temperatures between the left and right firing of regenerative glass melting furnaces are mainly caused by the thermal asymmetry of the regenerators.

The use of a simple PID controller to manage fuel quantities in such a way that the same vault temperatures arise for the left and right fires is the unsuitable control structure. The attempt to compensate for such asymmetries by left / right different amounts of fuel regularly leads to the existing asymmetries systematically increasing. Any increase in the amount of fuel on the colder regenerator side - to compensate for the colder air - tends to make the hotter regenerator hotter and hotter. Any reduction in the amount of fuel on the side of the hotter regenerator - to compensate for the hotter air - leads to the already colder regenerator becoming colder and colder.

A "model" of the physical relationships allows the establishment of a symmetry control of the regenerators as preconditions for symmetrical furnace temperatures. The heat content of the left and right regenerators and the amount of heat they provide for preheated combustion air should be matched for the right and left fires in order to ensure the symmetrical heating of the furnace chamber. At least the left and right vault temperatures should be adjusted to one another.

Depending on the initial situation, 500 to 4000 MJ of heat must be transported from the hotter to the colder regenerator without allowing any differences in the amount of fuel between the left and right fire. This can be done by slightly different period times or by different air conditions. If the extension or shortening of the period times z. B. limited to 60 seconds, the symmetry compensation between the regenerators can take up to 3 days in a typically asymmetrical starting position. The vault temperature of the furnace can only be regulated at all by means of such a symmetry control.

Coming back on again 3 is in the second control loop II recognizable that this is the case for evaluating the thermal symmetry of the regenerators 50 , 50 ' the heat Q _Li , Q _Re the preheated combustion air VB from the regenerators 50 , 50 ' is used. The individual amounts of heat Q _Li , Q _Re are made by a mathematical model of the regenerators 50 , 50 ' delivered in the unit of difference 204 is implemented as a software module and then the difference between the individual amounts of heat Q _Li , Q _Re supplies. The difference between them is determined by the unit of difference 204 as an energy flow of asymmetry ΔQ made available to the symmetry regulator Rs in megawatts. After a one-time basic adjustment and self-learning adjustment, the mathematical model is able to deliver the corresponding amounts of heat such as real measured values from thermocouples. The symmetry regulator Rs regulates the in 5 difference shown in more detail ΔQ the amount of heat to zero. For this purpose, the symmetry regulator provides Rs for the regenerators 50 , 50 ' a time span ± Δt is available with which the period duration t for the firing of the upper furnace 1 about the regenerators 50 , 50 ' is changed.

The example of a small U-flame melting tank should be mentioned, which in the starting position had regenerators 45 K hotter with a left-hand fire and consequently 20 K hotter vault temperatures. After the symmetry has been established, the chamber temperatures only differ by 0 .. 3 K, the vault temperatures in the furnace are almost the same for the left and right fire - a prerequisite for their controllability.

If both sides of the fire are operated with the same lambda values and both regenerators are in approximately the same state, the symmetry controller will find the same period times for the left and right fire again after the heat balance has been established between the regenerator sides without any action on the part of the operator.

Conversely: A permanent imbalance that then occurs - e.g. B. the left period must be permanently 20 seconds longer in order to maintain the symmetry - such a permanent misalignment provides additional information after establishing the symmetry, e.g. B. via air leakage on the exhaust side of the affected regenerator or regenerator wear. The same applies to visible temperature differences at the chamber foot, provided that they can be recorded and interpreted correctly from a technological point of view.

If the quantities of combustion air and / or exhaust gas from the regenerators are different on the left and right, then the symmetry of the temperatures alone is no longer sufficient. The energy inputs must then be balanced out on the right and left by preheated combustion air. There is also a PLC-based model of the regenerator in the controller, which provides the corresponding - no longer directly measurable variables.

From the 5 it can be seen by way of example that for a comparatively long period of time for the left regenerator 50 a positive value of + Δt predominates. This can be used as part of a particularly preferred evaluation module for the technological evaluation of the state of the left regenerator. In the present case, it can be established that there is an asymmetry despite the second control loop II exists. I. E. during the positive control value of the period + Δt obviously the period of the lighting with the left regenerator had to be 50 to fire the upper furnace 1 be extended regularly - this can lead to an uncontrolled ingress of air in the furnace chamber 1 or in the regenerator 50 shut down.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DD 143158 A1 [0004]
• DE 3610365 A1 [0005]
• GB 1188256 [0006]
• WO 2012/038488 A1 [0007, 0008, 0021, 0033, 0052]

Claims (22)

Method for the controlled operation of a regeneratively heated industrial furnace (100) with a furnace space (10), in particular with a melting tank, especially for glass, comprising the steps: - Injecting fuel into the furnace space (10) via at least one fuel injector (20, 20 '), which is designed to inject fuel, in particular with practically no combustion air, - periodically alternating supply of combustion air to the furnace chamber (10) on the one hand in a first period and on the other hand exhaust gas (AG) from the furnace chamber (10) in a second period separately from the fuel by means of a left-hand regenerator (50) and right-hand regenerator (50 ') assigned to the at least one fuel injector (20, 20'), which are designed for the regenerative storage of heat from the exhaust gas and the transfer of heat to the combustion air, wherein in a first control loop (IA) for temperature control (200): - via a furnace chamber temperature as a controlled variable, and - ei NEN first controller (R _T ), in particular a PID controller, for the furnace chamber temperature (T), as well as - a first adjustable manipulated variable in the form of a fuel flow and / or a combustion air flow is set _{via an actuator assigned to the first controller (R T),} characterized in that in a control loop (IB) which extends, in particular parallel, the first control loop (IA) for the temperature control (200): a regenerator temperature, in particular a regenerator head temperature (T _L , T _R ), of the left regenerator (50) and right regenerator (50 ') is determined, and a disturbance variable is determined by means of a deviation in the regenerator temperatures, wherein - the disturbance variable by means of the, in particular parallel and / or amplifying, control loop (IB) for regulating the furnace chamber temperature ( T) is used. Procedure according to Claim 1 characterized in that a control deviation (dT) of the furnace chamber temperature is determined to regulate the furnace chamber temperature and the disturbance variable of the furnace chamber temperature is added as the deviation between the regenerator temperatures to the control deviation, and the first adjustable manipulated variable is set on the basis of the deviation between the added to the control deviation Regenerator temperatures of the left regenerator (50) and the right regenerator (50 '). Procedure according to Claim 1 or 2 characterized in that the deviation between the regenerator temperatures is determined as an amount increasing to the control deviation (dT) of the furnace chamber temperature, and / or as a deviation in the regenerator temperatures between the target side and the output side of the left regenerator (50) and right regenerator (50 ') ) is determined in relation to the side of the respective fuel injector (20, 20 '). Method according to one of the Claims 1 to 3 characterized in that the control deviation (dT) of the furnace chamber temperature is determined as the setpoint temperature minus the actual value_temperature in the furnace chamber and / or for the disturbance variable the deviation between the regenerator temperatures is determined by means of a difference between the regenerator temperature of the target side and the regenerator temperature of the Exit page. Method according to one of the Claims 1 to 4th characterized in that the disturbance variable is amplified to a predetermined power (N) by means of the deviation (ΔT _LR , ΔT _RL ) between the regenerator temperatures and / or is weighted with a predetermined multiplier (k). Method according to one of the Claims 1 to 5 characterized in that the regenerator temperature, in particular a regenerator head temperature (T _L , T _R ), is determined as the mean ((T_Max + T_Min) / 2) between an upper regenerator temperature and a lower regenerator temperature, in particular the Deviation between the regenerator temperatures is determined with the means, in particular by means of a difference between the regenerator temperature mean of the target side and the regenerator temperature mean of the output side. Method according to one of the Claims 1 to 6th characterized in that in a second control loop for a symmetry control regarding the left and right regenerators: - via a first preheating parameter that is significant for the heat content of the combustion air of the first regenerator and a second preheating parameter that is significant for the heat content of the combustion air of the second regenerator, and - a second Controller for the difference between the first and second preheating parameters, as well as - a second adjustable manipulated variable in the form of a heat transfer variable influencing the heat transfer between the first and second regenerator is set via an actuator assigned to the second controller. Method according to one of the Claims 1 to 7th characterized in that the second adjustable manipulated variable is set in the form of a heat transfer variable influencing the heat transfer between the first and second regenerator, by the amount of the difference between the to keep the first and second preheating parameters below a threshold value close to zero. Method according to one of the Claims 1 to 8th characterized in that a period of time is set as the heat transfer variable by which the first period is extended for the hotter one of the first and second regenerators and / or the first period is shortened for the colder one of the first and second regenerators. Method according to one of the Claims 1 to 9 characterized in that a period of time is set as the heat transfer variable by which the second period is lengthened for the colder one of the first and second regenerators and / or the second period is shortened for the hotter one of the first and second regenerators. Method according to one of the Claims 1 to 10 characterized in that the preheating parameter is formed as heat from preheated combustion air, the heat from preheated combustion air being obtained from a model calculation of the regenerator. Method according to one of the Claims 1 to 11 characterized in that the preheating parameter is formed as the product of an amount of combustion air and a regenerator head temperature, the amount of combustion air and / or regenerator head temperature being measured, in particular the regenerator head temperature being a lowest regenerator head temperature. Method according to one of the Claims 1 to 12th characterized in that the preheating parameter is formed as an average of at least one regenerator head temperature and / or furnace chamber temperature, in particular is formed at the end of a first period and / or a second period, in particular as a weighted average of a highest and a lowest value thereof. Method according to one of the Claims 1 to 13th characterized in that a furnace chamber temperature is formed as a weighted average of a number of different, in particular spatially different, temperature measurements, in particular in the upper furnace and / or regenerator head. Method according to one of the Claims 1 to 14th characterized in that an extrapolation of a furnace chamber temperature to a furnace chamber temperature at the end of the first and the second, in particular of each, period duration is carried out, in particular on the basis of a modeled time profile of a representative furnace chamber temperature. Method according to one of the Claims 1 to 15th characterized in that, after a temperature drop in the first control loop caused by the periodically alternating guidance, a first adjustable manipulated variable in the form of a fuel flow and / or a combustion air flow is set via an actuator assigned to the first controller, and an additional charge of the same is supplied to the furnace for this purpose, in particular, the surcharge is formed from the amount of the fuel failure due to the change and / or from a rate of temperature increase after alternating guidance. Method according to one of the Claims 1 to 16 characterized in that the difference between the first and second preheating parameter is used as the control result of the second control loop for evaluating the state of the regenerator and / or for evaluating a further influencing variable, in particular for evaluating an uncontrolled ingress of air in the furnace chamber and / or regenerator. Method according to one of the Claims 1 to 17th characterized in that an increase in the combustion air flow or another fluid is brought about by the hotter regenerator as the heat transfer variable, in particular independently of a change in the fuel flow. Method according to one of the Claims 1 to 18th characterized in that a reduction in the combustion air flow or another fluid is brought about by the colder regenerator as the heat transfer variable, in particular independently of a change in the fuel flow. Control device, in particular for carrying out a method according to one of the Claims 1 to 19th , having an industrial furnace control: a temperature control module for a first control loop by means of: - via an oven temperature as a control variable, and - a first controller, in particular a PID controller, for the oven temperature, and - via an actuator assigned to the first controller The first adjustable manipulated variable can be set in the form of a fuel flow and / or a combustion air flow, characterized in that in a control loop (IB) for the temperature control (200) that extends, in particular parallel, the first control loop (IA): a regenerator temperature, in particular a regenerator head temperature (T _L , T _R ) of the left regenerator (50) and right regenerator (50 ') is determined, and a disturbance variable is determined by means of a deviation in the regenerator temperatures, wherein - the disturbance variable is used by means of the, in particular parallel and / or amplifying, control loop (IB) to regulate the furnace temperature (T). Control device according to Claim 20 characterized in that - a symmetry control module relating to the left and right regenerators for a second control loop by means of: - via a first preheating parameter that is significant for the heat content of the combustion air of the first regenerator and a second preheating parameter that is significant for the heat content of the combustion air of the second regenerator, and - a second controller for the difference between the first and second preheating parameters, and a second adjustable manipulated variable in the form of a heat transfer variable influencing the heat transfer between the first and second regenerator can be set via an actuator assigned to the second controller. Regeneratively heated industrial furnace with a furnace space, in particular with a melting tank, in particular for glass, further comprising: - at least one fuel injector for injecting fuel into the furnace space, which is designed for injecting fuel, in particular with practically no combustion air, - a dem at least one fuel injector associated left regenerator and right regenerator, which are designed for the regenerative storage of heat from the exhaust gas and transfer of heat to the combustion air for the periodically alternating guidance of combustion air to the furnace chamber in a first period and exhaust gas from the furnace chamber in a second period separately from the fuel, and a control device after Claim 20 or 21 .

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