EP0183990A1 - Method for diagnosing the condition of a heating installation and apparatus therefor - Google Patents

Abstract

For diagnosing the operating condition of a heating installation (1), operating quantities are stored as a function of the degree of loading (ss) (19, 23, 27), with the firing installation operating optimally. In subsequent operation, operating quantities corresponding to the stored quantities and the instantaneous degree of loading (ss) are then measured, and indications (31, 54, 52) of the instantaneous installation operating condition in relation to the optimum operation are then produced from comparisons of stored and measured values. <IMAGE>

Description

The present invention is based on a method according to the preamble of claim 1 and comprises a device for this purpose according to the preamble of claim 10.

Such methods and devices are known. By monitoring current operating parameters, the current operating status of the combustion system is made apparent by means of displays. For example, a loss report on a combustion system is not very meaningful, if not the minimum losses that can be achieved at all, taking into account a goal, such as minimum long-term costs or minimum fuel consumption, and are related to the display. An unrelated display is further disadvantageous in that an operator must have in-depth knowledge of the system and the processes taking place in it in order to interpret the displays generated in this way at all. Furthermore, the interpretation of a displayed current operating state with regard to the possible achievement of an optimal or target operating state places particularly high demands on an operator when the readings have to be combined accordingly in a system determined by several operating sizes in their operation, to be able to draw conclusions from where to intervene in the system in order to achieve the target operating state.

The aim of the invention is to create a method and a device of the type mentioned at the beginning, with the aid of which displays relating to a target operating state of the system are generated, by which an operator is informed of the deviation of the current operating state from a target operating state the system is informed. When solving this task, it must be taken into account that a firing system per se is not an optimal operating state, e.g. with minimal losses, but the respective optimal operating state is an operating function.

In the case of combustion plants, the target operating parameters are preferably determined on the basis of measurements. It is only the target operating variables mentioned that are stored for the load level range that occurs in practice.

The current operating state of the system at the current load level is then diagnosed by relating the current operating variables to the previously stored target operating variables at the current load level.

Since, according to what has been said, it is very important for the correct interpretation of the current operating state of a plant to know how the target operating state has been defined, it is already described here how a possible target operating state is determined in a furnace. The target operating state for the furnace is the minimization of the exhaust gas losses q _A , which is As is well known, it consists of the exhaust gas losses due to sensible heat q _AF and the exhaust gas losses due to unburned q _AU . A first load level value β ₁ is now specified on the furnace with an optimally clean boiler. The oxygen content 0 ₂ in the flue gas and the carbon monoxide CO content in the flue gas are measured, as is the temperature difference Δϑ between fresh air supply and flue gas. With these parameters, the air factor A is initially determined as a function of the oxygen content 0 ₂ and the carbon monoxide content CO, as are the exhaust gas losses due to the unburned. Instead of or in addition to the CO content, the content of CH compounds in the flue gas or the soot number can also be used. The exhaust gas losses due to sensible heat are determined on the other hand from the measured temperature difference and the measured oxygen content, depending on the fuel. The approximate formulas for determination of incineration plants are known, for example, refer to Dubbel's Taschenbuch für den Maschinenbau, Vol. II, section: Steam generation plants ............ It is now known that as a function of the air factor λ, determined as the ratio of the actual combustion air volume to the stoichiometric air volume, the losses due to sensible heat increase approximately linearly, starting at λ = 1 from a minimal, but not disappearing, loss value, and that the exhaust gas losses due to unburned matter, if there is a lack of air (λ <1) are very high, with λ falling steeply and asymptotically approaching the zero loss axis with increasing l. The superimposition of these two function curves results in an increasing λ only a steeply falling curve, which asymptotically approaches the linearly increasing course of the losses due to sensible heat after passing through a minimum point. The minimum losses occur at the air factor value at which the tangent to the sum function is horizontal. The air factor assigned to the minimum value of the losses is always somewhat larger than 1. Taking this situation into account, the combustion system to be measured at a certain load level β ₁ is now changed by changing the air supply and thus the oxygen content O ₂ in the flue gas, hence the air factor A, and under repeated determination - from 0 ₂ -, CO and Δν measurement - the total exhaust gas losses, as the sum of the above-mentioned losses due to sensible heat and unburned material, the minimum value sought for the total losses. The result is now the one hand as to be stored Zielgrösscn the target oxygen content O _2OPT, the target temperature difference Δν _OPT and if call in for further analysis, the optimum whole or divided into components gas losses q _AOpt b ^zw. Q _AFOPT, q _AUOPT. If these values are found in the abovementioned, set β ₁ , the next load level value β _{2 is} passed and the process is repeated, etc. For such a determination of the target operating state, other optimization criteria can also be selected, for example the minimization of the plant operating costs, taking into account maintenance, cleaning and replacement costs. Taking into account that on a firing system, operating sizes in a complex, not easy to understand manner from the position of the intervention depend on medium, it is now proposed that, by relating current and target operating variables, displays, such as instructions, for correcting the setting of the intervention means, such as the air supply, are generated for converting the system from an undesired current operating state to the target -Operating condition.

• - der Sauerstoffgehalt im Rauchgas O₂,
• - die Differenz von Lufteintritts- und Rauchgas-Tem- peratu^r Δν_A,
• - der Abgasverlust durch fühlbare Wärme im Rauchgas qAF.

In the minimal configuration of the method according to the invention, at least the following variables are determined both once as target operating variables and subsequently during ongoing operation as instantaneous operating variables as a function of the degree of load:

• - the oxygen content in the flue gas O ₂ ,
• - the difference between the air inlet and flue gas tem- peratu ^r Δν _A,
• - the exhaust gas loss due to sensible heat in the flue gas qAF.

The target farm sizes are saved.

A device zurapparativen diagnosis of the operating state of a Feuerungs _- conditioning, are at the sensors for measuring instantaneous operating parameters are provided as well as with an evaluation unit for generating indications of the operating state of the plant, such as for carrying out the procedure referred to is characterized according to the wording of claim 10 out.

Advantageous further developments are experienced regarding the _V, in the claims 2 to 9, and on the device specified in claims 11 and 12. FIG.

An embodiment of the invention is then explained with reference to Figures la to 2.

• Fig. la ein Blockdiagramm einer Anlage, hier einer Feuerungsanlage, mit einem ersten Teil des erfindungsgemässen Gerätes, insbesondere zur Abspeicherung von Ziel-Betriebsgrössen,
• Fig. lb als Fortsetzung von Fig. la einen zweiten Teil des erfindungsgemässen Gerätes mit der Auswertung vorgängig erfasster Ziel-Betriebsgrössen und momentan erfasster Betriebsgrössen undmit der entsprechenden Erzeugung von interpretierten und bezogenen Anzeigen,
• Fig. 2 das Blockschema eines analogen Funktionsgenerators, wie er allgemein bei einer Analog-Realisierung des Gerätes nach Fig. la eingesetzt werden kann.

Show it:

• La is a block diagram of a system, here a furnace, with a first part of the device according to the invention, in particular for storing target operating variables,
• Fig. Lb as a continuation of Fig. La a second part of the device according to the invention with the evaluation of previously recorded target operating variables and currently recorded operating variables and with the corresponding generation of interpreted and related displays,
• Fig. 2 shows the block diagram of an analog function generator, as it can generally be used in an analog implementation of the device according to Fig. La.

In Fig. La and lb are, as this introductory note, signals corresponding to physical quantities and their signal paths equally denoted by symbolic abbreviations for the appropriate physical quantities, ^g from Clarity ründen. It is in Fi ^g . la a furnace, not the subject of the present invention, designated 1. On an actuator 3, the fuel supply B, on an actuator 5, the air supply is adjusted on the one hand depending on the load degree β setting on a signal transmitter 7 via a controller 6, and on the other hand also independently of one another, as shown in FIGS. 3a and 5a. The actuators 3, 5, 7 are each designed according to the size to be set, so the actuator 3 as a fuel valve, the actuator 5 as an air flap. With a signal converter 9, the momentary load degree β entered, for example, as the angle of rotation of a steering wheel, is converted into a corresponding electrical signal, with a sensor 11 the temperature of the inlet air ν _U , with a sensor 13 the temperature ν _{A of} the flue gases, with a sensor 15 the oxygen content 0 ₂ in the flue gas, with a sensor 16 the CO content in the flue gas. In a first process step, the system is generally operated optimally under optimal conditions. In the case of a furnace, this means that the system is operated with a variation of the load grade ß in the load grade range that occurs in practice with freshly cleaned heating surfaces and under nominal conditions (fuel type, boiler pressure, etc.) and the desired target operating conditions are set on the furnace.

As already explained in the introduction, the target operating conditions are now recorded as follows.

die Abgasverluste durch Unverbranntes, nach

die Abgasverluste durch fühlbare Wärme und durch Addition die gesamten Abgasverluste q_A(0₂, Δν, CO). Diese Ausdrücke mit Einführung entsprechender Proportionalitätskonstanter werden entweder im Sinne der analogen Programmierung analog oder aber digital berechnet Die Auswertung von (1) für die Optimum-Bestimmung kann, falls nachmals nur q_AF ausgewertet wird, manuell erfolgen.First, the input switches S are closed. A fixed load level β _{1 is} set and recorded on the signal converter 9. The temperature measured values ν _U for the fresh air and ν _A for the flue gas are calculated in a subtraction unit 21 to form the temperature difference Δν. The measurement signal for the O ₂ content appears at the output of the sensor 15, and for the flue gas CO content at the output of the sensor 16. The oxygen content measured value and the temperature difference measured value, as well as the CO measured value, are fed to a computing unit 25. In the arithmetic unit 25, the exhaust gas loss q is determined, taking into account both the exhaust gas losses due to sensible heat ^q _{AF '} and the exhaust gas losses due to unburned q _AU , because a minimum can only be determined when both components are taken into account, and what if, as the target operation operation with minimal exhaust gas losses is essential. In this case, the CO content must be taken into account. The computing unit 25 determines the shape according to a known expression

the exhaust gas losses due to unburned, after

the exhaust gas losses through sensible heat and through addition the total exhaust gas losses q _A (0 ₂ , Δν, CO). These expressions with the introduction of corresponding proportionality constants are calculated either analogously or digitally in the sense of analog programming. The evaluation of (1) for the optimum determination can, if only q _AF is subsequently evaluated, be carried out manually.

• Beim jeweils eingestellten momentanen Lastgrad ß erscheinen an den Speicherausgängen::
  • - am Speicher 27 der Ziel-Abgasverlustwert q_AOPT (β)
  • - am Ausgang des Speichers 23 die Ziel-Temperatur-Differenz in Funktion des Lastgrades, Δν_OPT(β) und
  • - am Ausgang des Speichers 19 der Ziel-Sauerstoffgehalt O_2OPT(β),

The total exhaust gas loss values q _A determined are preferably minimized by adjusting the air supply at the actuator 5a. The corresponding electrical signal value appears at the output of the computing unit 25 and is monitored. If its minimum is found, which is possible automatically or by reading through a minimum detection network 17, then a charging signal L is triggered. This charging signal L is fed to a first memory 19, to which the oxygen content 0 ₂ and the load degree β _{1 are} fed on the input side. When the charging signal L appears, the value of the load level β ₁ and the optimal oxygen content _{value 020PT} ( _ßl ) are saved. The charging signal is simultaneously fed to a memory 23, which in turn is fed the load level signal β ₁ and the temperature difference signal Δν. Here too, when the charging signal L appears, the load degree value β ₁ and the corresponding differential temperature value Δν _OPT (β ₁ ) are stored. The output of the computing unit 25 observed for finding the exhaust gas loss minimum becomes when the charging signal L appears, it is also stored in a further memory 27 together with the load degree value β ₁ . This determination procedure for the target operating variables is repeated for further load degree values within the operating load degree range of the furnace 1 until the load degree-dependent functions of the operating variables recorded there are stored as optimal values or target values in the memories 19, 23, 27. The switches S are then opened, the memory contents are not changed further and are available for subsequent evaluation at the corresponding outputs. The following information is available for the following operation of the system:

• With the currently set load level ß, the following appear at the memory outputs:
  • the target exhaust gas loss _value q _AOPT (β) at the memory 27
  • - At the output of the memory 23, the target temperature difference as a function of the degree of load, Δν _OPT (β) and
  • the target oxygen content O _2OPT (β) at the outlet of the store 19,

• - Lastgrad ß für den Speicherabruf
• - die momentane Temperaturdifferenz
• - der momentane Rauchgas-Sauerstoffgehalt 02
• - allenfalls der Momentan-CO-Gehalt der Rauchgase (gestrichelt).

as well as the measured values as the current operating parameters:

• - Load level ß for the memory request
• - the current temperature difference
• - the current flue gas oxygen content 02
• - at most the instantaneous CO content of the flue gases (dashed).

The instantaneous exhaust gas losses q _{A also} appear in system operation at the output of the computing unit 25, which, however, is then separated from the memory 27. In a less complex configuration, only the losses due to sensible heat q _{AF are determined} from the instantaneous O ₂ and Δν measured values as instantaneous losses, with a more complex q _A as the sum of the components q _AF , q _AU , as shown in dashed lines Instantaneous measurement of CO. According to FIG. 1b, the current exhaust gas loss value q _AF (β) or q _A (β) is continuously compared in a first comparison unit 29 with the loss _value q _AOPT (β _m ) corresponding to the then current load level β _m at the output of the memory 27. The comparison result Ab is used to control a display 31 which indicates a possible fuel saving and, if need be, an associated instruction display 32 which instructs to change the fuel air ratio. The instantaneous exhaust gas losses corresponding to q _AF (βm) or q _A (βm) are shown on a display 33. At comparison units 34, 36, 38, to which, on the one hand, the target temperature difference values Δν _OPT (β _m ) are fed from the output of the memory 23, on the other hand the instantaneous ― temperature difference values Δν (β _m ), the instantaneous temperature difference values are compared with the target difference values and determined whether the deviations in the temperature differences are within predetermined ranges or not. Analogously, comparison units 40 to 46, to which the target oxygen content is stored by the storage 19 during the

are fed mentan prevailing load degree β _m as well as the current oxygen content values O ₂ (β _m), checks whether the instantaneous oxygen values O ₂ (β _m) are related to the target oxygen content values O _2OPT (β _m) in predetermined areas.

From the logical combination of the outputs of the comparison units 34 to 38 on the one hand and 40 to 46 on the other hand, the boiler contamination is shown on a display 54, if necessary with instruction 56 to clean the boiler, on a display 52 that incorrect air is supplied, on a display 48 that there is an excessive excess of air and at most on a display 50 that the air supply is to be restricted. Checking the instantaneous oxygen content 0 ₂ (ßm) with reference to the target oxygen content O _2OPT (βm) alone gives an indication 58 on a display 58 that there is a lack of air, which can trigger a hazard or alarm signal. Accordingly, a display 60 can be activated which gives the instruction to increase the air supply.

If only the total flue gas _loss q _{AOPT is} saved when storing the target operating parameters, but instead (not shown) according to expressions (1), (2), whose individual components q _AFOPT , q _AUOPT due to unburned or sensible heat, is so given the possibility of outputting both components separately, also in system operation, as a function of the current load level at the output of the computing unit 25 and comparing them with the loss components ^q _AF (β ^m ), q _AU (βm), which are then individually determined at the time. This gives information about deviations from the current exhaust gas losses, separated by losses through sensible warmth and losses through unburned, with reference to the optimal values. If, as mentioned, the CO sensor 16 is dispensed with in the detection of the instantaneous values, then the computing unit 25 will determine the instantaneous loss of flue gas, neglecting the losses due to the unburned, which is sufficient in many cases. It must be repeated that in this case the CO measurement is only necessary to find the minimum loss. If the CO measured values are also saved as COOPT values as the target values, the possibility arises from a comparison of these target CO values CO _OPT (ßm) with the instantaneous CO values CO (ßm) measured during operation for uneven air distribution close, and to make the lack of air diagnosis more reliable.

Furthermore, it can be advantageous in some cases to continuously determine suitably defined temporal averages of company variables. This generally assumes that the system for executing the process is digital. A clock generator 64 is then provided in the usual manner, which clocks the memory and sensor output during evaluation, as on a microprocessor-based unit. If averaging is dispensed with, it is sufficient in some cases to set up such an arrangement on an analog basis. The memories corresponding to 19, 23 and 27 of FIG. 1 a are then implemented, for example, by function generators, as shown in FIG. 2. Function generators emit an output signal as a specific function of an input signal. Function generator 66 shows a possible form of implementation with a diode resistor network. When the target operating variables / load degree function is stored, the latter is first determined graphically, for example, then by adjusting potentiometers R ₁₁ to R _32, at most from bias sources V _I to V ₃ , by piecewise linearization, the function curve determined, for example set for the temperature difference Δν (β), as a function of the load-level-corresponding signal U (ß) at the input of the function generator.

Claims (12)

1.Procedure for the apparatus-related diagnosis of the operating state of a furnace, in which current operating variables of the system are recorded and indications for the operating state are generated, characterized in that target operating variables (Δϑ _OPT , O _2OPT ) of the system _beforehand in function of the load level ( ß) determined and, if necessary with the target operating parameters derived from it (q _AOPT ), stored as a function of the load level (ß) and, by relating current and target operating parameters, displays (31, 48, 52, 54, 58) about deviations of the Current operating state generated by the respective target operating state. 2. The method according to claim 1, wherein on the system engaging means (3 _a , 5 _a ) are provided for influencing the operating state, characterized in that by relating the instantaneous to the target operating variables (Δν, O ₂ ) Displays (50, 56, 60), such as instructions for correcting the setting of the engagement means (3 _a , 5 _a ), are used to transfer the system from an undesired current operating state to the target operating state. 3. The method according to claim 1 or 2, characterized in that one determines at least as the target operating variables and stores them as a function of the degree of load (β): - the oxygen content (020PT) in the flue gas, - the difference between air inlet and flue gas temperature (Δν _OPT ), - the loss due to sensible heat (q _AFOPT ) in the flue gas,
and the instantaneous operating variables are the instantaneous oxygen content (0 ₂ ) in the flue gas, the instantaneous difference (Δν) of said temperatures, and the instantaneous loss due to sensible heat (q _AF ). 4. The method according to claim 3, characterized in that at least one further variable, such as the carbon monoxide (CO) -, the content of CH compounds or the number of soot in the flue gas is taken into account and stored when determining the target operating variables. 5. The method according to any one of claims 1 to 4, characterized in that one derives the total exhaust gas losses (q _A ) from the specific target operating variables and the detected instantaneous operating variables and stores them as a further target operating variable. 6. The method according to any one of claims 1 to 5, characterized in that the instantaneous value of possible relative fuel _savings (Ab) is determined from the difference between the instantaneous (q _AF ; q _A ) and the target loss value (qAFOPT; q _AOPT ) . 7. The method according to any one of claims 1 to 6, characterized in that mean values of certain instantaneous operating variables ^(q _AF continuously suitably defined _'qA) forms with the corresponding averaged, stored target operation ^g r ^{össen (q} _AFOPT' ^q _aopt) in Relationship brings. 8. The method according to any one of claims 1 to 7, characterized in that target operating variables in function of the load level (ß) with the aid of at least one adjustable function generator with a load level-dependent input signal and a target operating variables proportional output signal analog stored. 9. The method according to any one of claims 1 to 8, characterized in that target operating variables are stored digitally as a function of the load level and the stored operating variable values are retrieved as a function of the current load level according to assigned load level values for further processing. 10. An apparatus for performing the method according to one of claims 1 to 9, for a furnace, in which sensors for measuring instantaneous operating variables are provided, with an evaluation unit for generating displays about the operating state of the system, characterized in that Storage means (19, 23, 27, 66) for storing target operating _variables q _AOPT , Δν _2OPT ) of the system as a function of an _independent operating _variable (ß) and the evaluation unit (29, 34 - 38, 40 - 46 ) on the input side is connected to inputs for the sensors and to the output side of the storage means and acts on the output side on displays. ll. Apparatus according to claim 10, characterized in that the memory means comprise adjustable function generators (66) and / or digital memories. 12. Apparatus according to claim 10 or 11, characterized in that an input for a signal proportional to the load level is provided as an independent operating variable and at least one input for at least one dependent operating variable on the storage means, and that dependent operating variable values assigned to these can be stored and by load level values Creation of corresponding, load-level-dependent signals, the corresponding dependent operating quantity values can be called up.

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