EP2065641A2 - Method for operating a continuous flow steam generator and once-through steam generator - Google Patents

Method for operating a continuous flow steam generator and once-through steam generator Download PDF

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Publication number
EP2065641A2
EP2065641A2 EP07023081A EP07023081A EP2065641A2 EP 2065641 A2 EP2065641 A2 EP 2065641A2 EP 07023081 A EP07023081 A EP 07023081A EP 07023081 A EP07023081 A EP 07023081A EP 2065641 A2 EP2065641 A2 EP 2065641A2
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EP
European Patent Office
Prior art keywords
evaporator
flow
characteristic
mass flow
enthalpy
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP07023081A
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German (de)
French (fr)
Other versions
EP2065641A3 (en
Inventor
Jan BRÜCKNER
Joachim Dr. Franke
Frank Thomas
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
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Siemens AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens AG filed Critical Siemens AG
Priority to EP07023081A priority Critical patent/EP2065641A3/en
Priority to RU2010126182/06A priority patent/RU2010126182A/en
Priority to EP08853664A priority patent/EP2212618B1/en
Priority to PT88536644T priority patent/PT2212618E/en
Priority to PCT/EP2008/065522 priority patent/WO2009068446A2/en
Priority to CA2706794A priority patent/CA2706794C/en
Priority to ES08853664T priority patent/ES2402842T3/en
Priority to MYPI2010002487A priority patent/MY154744A/en
Priority to JP2010535331A priority patent/JP5318880B2/en
Priority to CN200880116657.7A priority patent/CN102216685B/en
Priority to US12/743,881 priority patent/US9482427B2/en
Priority to PL08853664T priority patent/PL2212618T3/en
Priority to AU2008328934A priority patent/AU2008328934B2/en
Priority to BRPI0819844-6A priority patent/BRPI0819844A2/en
Priority to TW097145590A priority patent/TWI465674B/en
Priority to ARP080105181A priority patent/AR069453A1/en
Publication of EP2065641A2 publication Critical patent/EP2065641A2/en
Priority to ZA201001475A priority patent/ZA201001475B/en
Publication of EP2065641A3 publication Critical patent/EP2065641A3/en
Withdrawn legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B37/00—Component parts or details of steam boilers
    • F22B37/02—Component parts or details of steam boilers applicable to more than one kind or type of steam boiler
    • F22B37/38—Determining or indicating operating conditions in steam boilers, e.g. monitoring direction or rate of water flow through water tubes

Definitions

  • the invention relates to a method for operating a continuous steam generator with a Verdampferlik Structure, wherein a device for adjusting the feedwater mass flow ⁇ a setpoint ⁇ s for the feedwater mass flow ⁇ is supplied. It further relates to a forced once-through steam generator for carrying out the method.
  • the heating of a number of steam generator tubes which together form an evaporator heating surface, leads to a complete evaporation of a flow medium in the steam generator tubes in one pass.
  • the flow medium - usually water - is usually before its evaporation to the Verdampferlik Structure flow medium side upstream preheater, commonly referred to as economizer, fed and preheated there.
  • the feedwater mass flow is regulated in the evaporator heating surface.
  • the evaporator flow should be changed as synchronously as possible to the heat input into the evaporator, because otherwise a deviation of the specific enthalpy of the flow medium at the outlet of the evaporator from the target value can not be reliably avoided.
  • Such an undesirable deviation of the specific enthalpy makes it difficult to regulate the temperature of the live steam emerging from the steam generator and moreover leads to high material loads and thus to a reduced service life of the steam generator.
  • the feedwater flow control can be designed in the manner of a so-called predictive or predictive design.
  • the required feedwater desired values should also be provided during load changes as a function of the current or expected future operating state.
  • a continuous-flow steam generator in which the feedwater flow is controlled by a preliminary calculation of the required feedwater quantity.
  • the basis for the calculation method is the heat flow balance of the evaporator heating surface into which the feedwater mass flow should enter, in particular at the inlet of the evaporator heating surface.
  • the desired value for the feedwater mass flow is determined from the ratio of the heat flow currently transferred to the flow medium by the heating gas in the evaporator heating surface and a desired enthalpy increase of the flow medium in the evaporator heating surface given with respect to the desired live steam state.
  • the measurement of the feedwater mass flow directly at the entrance of the evaporator heating surface proves to be technically complex and not reliably feasible in any operating condition.
  • the feedwater mass flow at the inlet of the preheater is alternatively measured and included in the calculations of the feedwater quantity, which however is not always equal to the feedwater mass flow at the inlet of the evaporator heating surface.
  • Both of these concepts for a predictive mass flow control are based as essential input variable on the setpoint value for the steam generator power, from which the characteristic values flowing into the actual setpoint determination are calculated on the basis of stored correlations and in particular by recourse to previously obtained calibration or reference measurements.
  • this requires sufficiently stable and clearly attributable to a firing capacity overall system properties, as is usually the case with fired steam generators.
  • other systems such as in a design of the continuous steam generator as a waste heat boiler for heat recovery from the flue gas of an upstream gas turbine, such conditions are not available.
  • a firing capacity can not be used to the same extent as a free parameter as in directly fired boilers, as in an interconnection as waste heat boiler usually considered as the primary criterion for controlling the entire system operation of the gas turbine, the system state of the be adapted to other components.
  • the invention is therefore an object of the invention to provide a method for operating a steam generator of the type mentioned above, with a comparatively low cost even when operating the steam generator as a waste heat boiler a particularly well adapted to the current or expected heat input into the evaporator heating adjustment of the feedwater mass flow allowed by the evaporator heating. Furthermore, a particularly suitable for the implementation of the method forced circulation steam generators should be specified.
  • this object is achieved according to the invention by determining the heat flow transferred from the heating gas to the flow medium taking into account a temperature characteristic value characteristic of the actual temperature of the heating gas at the evaporator inlet and a mass flow characteristic characteristic of the current mass flow of the heating gas.
  • the invention is based on the consideration that a useful, sufficiently reliable predictive mass flow control should also be adapted to the particular features of the waste heat boiler as well as for waste heat boiler switched steam generator.
  • the firing capacity is not a suitable parameter that allows a sufficiently reliable conclusion on the underlying heat flow balance.
  • gas turbine internal parameters may occur, so that on the basis of these sizes no acceptable conclusion on the enthalpy when entering the heating gas in the flue gas duct the steam generator is possible.
  • the heat flow balance used to determine the required feedwater flow should therefore be based on other, particularly suitable parameters.
  • the heating gas temperature when entering the evaporator and the mass flow of the heating gas are provided.
  • a pilot-controlled calculation of the required feedwater quantity is made possible on the basis of a heat flow balance of the evaporator, which may optionally also optionally include subsequent superheater heating surfaces.
  • the temperature characteristic characteristic of the actual temperature of the heating gas at the evaporator inlet it is possible in particular to determine a particularly reliable characteristic value for the heating gas enthalpy at the evaporator inlet taking into account the heating gas enthalpy at the evaporator outlet, which in turn can be calculated from the mass flow characteristic characteristic of the current mass flow, and thus a particularly reliable and needs-based determination of the current heat supply. or carry-over from the fuel gas to the feed water.
  • the desired value -Enthalpieerhöhung the flow medium can be determined in the evaporator, wherein from the ratio of these sizes a suitable setpoint for the feedwater mass flow can be calculated.
  • a characteristic value which is particularly representative of the current situation is preferably taken into account.
  • Such characteristic values can be suitably determined on the basis of currently available measurement data and can be made available in a suitable manner, in particular with recourse to stored memory characteristic values.
  • a particularly reliable evaluation of the heat flow balance and thus the determination of a particularly precisely calculated feedwater desired value is made possible by advantageously taking into account in each case a currently measured value as a characteristic temperature characteristic and / or as a characteristic mass flow characteristic.
  • the transferred from the heating gas to the flow medium heat flow is advantageously based on a heat flow balance determined, in which the enthalpy difference of the hot gas between evaporator inlet and evaporator outlet is used as the essential input variable.
  • a particularly reliable characteristic calculation is also considered in a further advantageous embodiment but also that reproduced by this enthalpy difference lowering of the energy content in the flue gas when passing through the Verdampfersammlung description on the one hand to an enthalpy in the flow medium within the Verdampfershirts Chemistry, on the other hand also to Energyein- and / or Aussticher binen in the components of the evaporator, ie in particular in the steam generator tubes and other metallic components, can lead.
  • this aspect of the energy input and / or outflow of heat in the metal masses is suitably taken into account as a characteristic correction value by which the enthalpy difference of the heating gas is suitably modified.
  • the current enthalpy of the hot gas at the evaporator outlet is advantageously taken into account by being determined on the basis of the pressure of the flow medium at the evaporator inlet taking into account the characteristic mass flow characteristic value for the current mass flow of the hot gas.
  • the mass flow characteristic which is preferably present in the form of a measured value, but alternatively can also be calculated indirectly via further parameters by using stored correlation or other characteristic values, is advantageously first in the so-called "pinch point" of the steam generator, ie in the temperature difference converted between the outlet temperature of the flue gas and the boiling temperature of the flow medium at the evaporator inlet, said temperature difference advantageously added to a determined based on the pressure at the evaporator inlet boiling temperature of the flow medium and from this sum the enthalpy of the heating gas at the evaporator outlet is determined.
  • the determination of the desired enthalpy increase of the flow medium in the evaporator heating surface is advantageously based, on the one hand, on the basis of suitable measured values, for example the pressure and the temperature of the flow medium at the evaporator inlet, the determined actual enthalpy.
  • suitable measured values for example the pressure and the temperature of the flow medium at the evaporator inlet
  • the determined actual enthalpy is specified.
  • the continuous steam generator can be operated in a so-called "Benson control mode".
  • the "Benson control mode” at the outlet of the evaporator heating surface overheating of the flow medium is present.
  • the overfeeding of a water storage tank connected downstream of the evaporator heating surface can be accepted, and the subsequent heating surfaces can still be partially supplied with unevaporated flow medium, so that complete evaporation of the flow medium takes place only in the subsequent heating surfaces.
  • the setting of a setpoint temperature for the flow medium at the outlet of the evaporator lying above the saturation temperature of the flow medium by a predetermined temperature difference of, for example, 35 ° C.
  • the saturation temperature of the flow medium can be specified in particular as the desired steam parameter.
  • This is advantageously in the specification of the target value for the enthalpy the flow medium at the outlet of the evaporator heating considered a current cooling demand in the evaporator heating downstream injection coolers.
  • the desired live steam temperature should therefore be achieved in particular as far as possible by a suitable adjustment of the feedwater flow, so that the additional cooling requirement in the injection coolers can be kept particularly low.
  • the enthalpy setpoint of the flow medium at the evaporator outlet are suitably increased, so that a correspondingly small amount of feed water is supplied via the thus changed setpoint for the feedwater mass flow.
  • the steam generator can also be operated in a so-called "level control mode" in which the water level is varied and readjusted in a water storage tank connected downstream of the evaporator heating surface, wherein overflow of the water storage tank should be avoided as far as possible.
  • level control mode in which the water level is varied and readjusted in a water storage tank connected downstream of the evaporator heating surface, wherein overflow of the water storage tank should be avoided as far as possible.
  • the water level within the water reservoir is kept as far as possible in a predetermined desired range, in an advantageous embodiment for the setpoint for the feedwater mass flow, a level correction value is taken into account, which characterizes the deviation of the actual level of the fill in the water storage of an associated setpoint.
  • the stated object is achieved by designing a feedwater flow control system assigned to a device for adjusting the feedwater mass flow for specifying the desired value for the feedwater mass flow on the basis of said method.
  • the forced-circulation steam generator is designed in a particularly advantageous manner as a heat recovery steam generator, which is acted upon the hot gas side with the exhaust gas from an associated gas turbine plant.
  • the advantages achieved by the invention are, in particular, that a predictive or preventive determination of the anticipated need is particularly far-reaching by the specific consideration of a characteristic of the current temperature of the flue gas when entering the Schugaskanal and / or for the current mass flow of the flue gas oriented feedwater mass flow set point is possible, whereby even in the case of use of the steam generator as a waste heat boiler and consequently only a lack of correlation of the corresponding enthalpy characteristics with the power or delivery characteristic of the system a particularly reliable and stable control behavior can be achieved.
  • the once-through steam generator 1, 1 'according to the FIG. 1 . 2 each have a designated as economizer preheater 2 for intended as a flow medium feed water, which is located in a throttle cable, not shown.
  • the preheater 2 is on the flow medium side, a feedwater pump 3 upstream and a Verdampferrois Structure 4 downstream.
  • On the output side the Verdampferrois Chemistry 4 flow medium side via a water reservoir 6, which may be configured in particular as a water separator or Abscheideflasche connected to a number of downstream superheater 8, 10, 12, which in turn may be provided for adjusting the steam temperatures and the like with injection coolers 14, 16.
  • the forced once-through steam generator 1, 1 ' is configured in each case as a waste heat boiler or heat recovery steam generator, wherein the heating surfaces, ie in particular the preheater 2, the evaporator 4 and the superheater 8, 10, 12 are arranged in a hot gas channel acted upon by the gas from an associated gas turbine plant in a hot gas side.
  • the once-through steam generator 1, 1 ' is designed for a regulated admission with feed water.
  • the feedwater pump 3 is followed by a controlled by a servomotor 20 throttle valve 22, so that via suitable control of the throttle valve 22, the funded by the feedwater pump 3 in the direction of the preheater 2 feed water quantity or the feedwater mass flow is adjustable.
  • the throttle valve 22 is followed by a measuring device 24 for determining the feedwater mass flow ⁇ through the feedwater line.
  • the servo motor 20 is controlled via a control element 28, the input side is acted upon by a supplied via a data line 30 setpoint ⁇ s for the feedwater mass flow ⁇ and determined by a measuring device 24 actual value of the feedwater mass flow ⁇ .
  • a tracking requirement is transmitted to the controller 28, so that in the case of a deviation of the actual from the nominal value, a corresponding tracking of the throttle valve 22 takes place via the activation of the motor 20.
  • the input line 30 with an input for setting the set value ⁇ s for the feedwater mass flow Spe feedwater flow control 32, 32 'connected.
  • This is designed to determine the setpoint ⁇ s for the feedwater mass flow ⁇ based on a heat flow balance in the evaporator 4, wherein the setpoint ⁇ s for the feedwater mass flow ⁇ based on the ratio of the currently transferred in the evaporator 4 from the heating gas to the flow medium heat flow on the one hand and a desired enthalpy increase of the flow medium in the evaporator heating surface 4 predetermined with regard to the desired live steam state is predetermined on the other hand.
  • a use of such a concept of providing a target value for the feedwater mass flow on the basis of a heat balance even for a once-through steam generator 1, 1 'in construction as a waste heat boiler is in the embodiments according to FIG. 1 .
  • FIG. 2 in particular achieved in that the transferred from the heating gas to the flow medium heat flow is determined taking into account a characteristic of the current temperature of the heating gas at the evaporator inlet temperature characteristic and a characteristic of the current mass flow of the heating gas mass flow characteristic.
  • the feedwater flow control 32 to a divider 34, the numerator as a suitable characteristic for the currently transmitted in the evaporator 4 from the heating gas to the flow medium heat flow and as a denominator with respect to the desired live steam condition predetermined predetermined characteristic value for the desired desired enthalpy of the Flow medium is supplied in the evaporator 4.
  • the divider 34 is connected on the input side to a function module 36, which is based on a supplied, characteristic of the current temperature of the hot gas at the evaporator inlet temperature characteristic value as output value outputs a value for the enthalpy of the hot gas at the evaporator inlet.
  • the supply of a measured value characteristic of the current temperature of the heating gas at the evaporator inlet is provided as a temperature characteristic value.
  • the characteristic value which is characteristic of the enthalpy of the heating gas at the evaporator inlet is output to a subtractor 38, from which characteristic value a characteristic value for the enthalpy of the gas at the evaporator outlet provided by a function module 40 is subtracted.
  • the sum of two temperature values is formed on the input side of the functional element 40 by a summing element 42.
  • the saturation temperature of the flow medium determined on the basis of the pressure of the flow medium at the evaporator inlet is taken into account via a functional element 44, which is connected on the input side to a pressure sensor 46.
  • a functional element 48 which in turn is fed via a further functional element 50 for the current mass flow of the fuel gas characteristic mass flow characteristic, the so-called "pinch point", namely the determined from the mass flow of the fuel gas temperature difference of the heating gas temperature at the evaporator outlet minus the boiling point the flow medium at the evaporator inlet, considered. From these two temperature contributions added via the summing element 42, the enthalpy of the heating gas at the evaporator outlet, optionally with reference to suitable tables, diagrams or the like, is thus provided by the function module 40.
  • the subtracting element 38 thus supplies the enthalpy difference or balance of the heating gas, that is to say the difference between the heating gas enthalpy at the evaporator inlet and the enthalpy of the heating gas at the evaporator outlet.
  • This enthalpy difference is forwarded to a multiplier 52, which is also supplied with the characteristic mass flow characteristic value, which, incidentally, can be present as a currently measured value.
  • the multiplier 52 thus provides a characteristic value for the output from the flue gas to the evaporator 4 heat output.
  • a correction for heat input and / or accumulation effects in the components of the evaporator heating surface 4, in particular in the metal masses, is initially provided.
  • said characteristic value for the heat output emitted by the heating gas is first supplied to a subtracting element 54, where a correction value characteristic of the heat input or withdrawal into the evaporator components is subtracted.
  • a functional element 56 On the input side, this is in turn subjected to the output value of a further functional element 58, in that a mean temperature value for the metal masses of the evaporator heating surface 4 is determined.
  • the further functional member 58 is connected on the input side to a pressure sensor 60 arranged in the water reservoir 6, so that the further functional member 58, the average temperature of the metal masses based on the pressure of the flow medium, for. B. by equating with the boiling temperature associated with this pressure in the water tank 6 can determine.
  • the subtracting member 54 On the output side, the subtracting member 54 thus transfers a heat output for the heating gas, reduced by the thermal power stored in the metal of the evaporator heating surface 4, and thus a characteristic characteristic of the heat output to be delivered to the flow medium.
  • This characteristic is used in the divider 34 as a counter, which is divided there by a denominator, the one in the With regard to the desired live steam state, the predetermined desired enthalpy increase of the flow medium in the evaporator heating surface 4 corresponds, so that from this division or this ratio the desired value ⁇ s for the feedwater mass flow ⁇ can be formed.
  • the divider 34 is connected on the input side to a subtractor 70. This is acted on the input side with a provided by a functional element 72 characteristic value for the desired setpoint for the enthalpy of the flow medium at the evaporator outlet.
  • the subtracting element 70 is acted upon on the input side by a characteristic value or actual value for the current enthalpy of the flow medium at the evaporator inlet which is subtracted in the subtracter 70 from the characteristic value for the enthalpy at the evaporator outlet.
  • the function module 74 is connected to the pressure sensor 46 and to a temperature sensor 76 in order to form the characteristic value for the actual enthalpy at the evaporator inlet.
  • the once-through steam generator 1 and the once-through steam generator 1 'according to the FIG. 1 or 2 differ with regard to the design of their feedwater flow control 32, 32 'in particular with respect to the formation of the setpoint for the enthalpy at the evaporator outlet and thus with respect to the input-side loading of the functional module 72nd
  • the forced flow steam generator 1 according FIG. 1 is designed for operation in the so-called "Level Control Mode", in which the water level is regulated in the water reservoir 6, wherein the superheater 8, 10, 12 connected downstream of the evaporator heating surface 4 exclusively Steam is passed, and the evaporator outlet side still entrained water in the water reservoir 6 is deposited.
  • the function module 72 is acted on the input side, on the one hand, with a measured value, supplied by the pressure sensor 60, for the pressure in the water reservoir 6.
  • the function module 72 is supplied via an associated input 78 with a parameter characteristic of the desired live steam condition, for example a desired steam content at the evaporator outlet. From this parameter together with the mentioned pressure characteristic value, the desired value for the enthalpy of the flow medium at the evaporator outlet is subsequently formed in the function module 72.
  • the divider 34 supplies, on the output side, a desired value for the feedwater mass flow which is aligned and determined on the basis of the heat balance mentioned.
  • This setpoint value is subsequently corrected in a subsequent adder 80 by a correction value which reproduces a desired change in the water level in the water reservoir 6 via the feedwater inflow.
  • the water level in the water reservoir 6 is detected by a level sensor 82.
  • This actual value for the fill level is subtracted in a subtractor 84 from a stored or otherwise presettable setpoint for the fill level in the water reservoir 6.
  • an effective feedwater mass flow value is determined in a subsequent actuator 86, with which the water reservoir 6 is to be acted upon to correct its fill level.
  • This correction value is added in the adder 80 to the reference value for the feedwater mass flow determined on the basis of the heat flow balance, so that a value composed of the two proportions is output as setpoint value ⁇ s for the feedwater mass flow.
  • the forced once-through steam generator 1 ' according to FIG. 2 designed for operation in the so-called "Benson Control Mode", in which an overfeed of the intended as a water separator 6 and the complete evaporation of the flow medium only in the following superheater 8, 10, 12 is possible.
  • the functional element 72 via which the setpoint value for the enthalpy of the flow medium is to be output at the evaporator outlet, likewise receives on the input side the pressure value in the water separator 6 determined by the pressure sensor 60 on the input side.
  • the function module 72 is preceded on the input side by another functional module 90, which determines a suitable setpoint for the temperature of the flow medium in the water reservoir 6 on the basis of a stored functionality or the desired live steam condition based on the actual pressure in the water reservoir 6 determined by the pressure sensor 60.
  • a temperature value may be stored as the setpoint for the temperature, which corresponds to the saturation temperature of the flow medium at the determined pressure plus a predetermined minimum superheat of, for example, 35 ° C.
  • the function module 72 determines from said setpoint value for the temperature, taking into account the current pressure value, said setpoint value for the enthalpy of the flow medium at the evaporator outlet.
  • This setpoint which is provided by the function module 72 and is essentially oriented on the properties of the flow medium as such, is subsequently changed in a downstream adder 92 by a further correction value.
  • This further correction value supplied by a function module 94 essentially takes into account, in the manner of a trim function, the deviation of the currently detected live steam temperature from the live steam temperature actually desired in view of the desired live steam condition. A Such a deviation can be made noticeable in particular by the fact that, if the live steam temperature is too high, cooling demand arises in the injection coolers 14, 16, and thus the admission of the injection coolers 14, 16 with cooling medium is required.
  • the functional module 94 shifts this cooling demand away from the injection coolers 14, 16 and towards an increased feedwater supply.
  • the desired enthalpy of the flow medium at the evaporator outlet is correspondingly lowered in the function module 94, in order to minimize the cooling requirement.
  • the enthalpy setpoint is increased via the correction value provided by the function module 94 and its addition in the adder module 92.
  • a downstream direct control loop in which a value for the enthalpy of the flow medium at the evaporator outlet is determined in a function module 100 on the basis of the measured values in the water reservoir 6 and compared in a differentiation module 102 with the desired enthalpy, ie with the desired enthalpy value.
  • the setpoint-actual deviation is ascertained, which is superimposed, via a downstream regulator 104 in an adder 106, on the desired value for the feedwater mass flow provided by the divider 34.
  • This superimposition is suitably delayed in time and damped, so that this control intervention only in case of need, so too rough control deviation, intervenes.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Steam Boilers And Waste-Gas Boilers (AREA)
  • Engine Equipment That Uses Special Cycles (AREA)
  • Central Heating Systems (AREA)
  • Air Conditioning Control Device (AREA)

Abstract

The method involves feeding a target value for a supply water mass flow to a device for adjusting the mass flow. The mass flow is predefined by a ratio of heat flow transferred in an evaporator heating surface (4) from a hot gas to a flow medium and a target enthalpy increase predefined with respect to a desired steam condition of the medium. The heat flow transferred from the gas to the medium is determined for specific temperature value characteristic of current temperature of the gas at an evaporator inlet and specific mass flow value characteristic for mass flow of the gas. An independent claim is also included for a forced-flow steam generator comprising an evaporator heating surface.

Description

Die Erfindung betrifft ein Verfahren zum Betreiben eines Durchlaufdampferzeugers mit einer Verdampferheizfläche, bei dem einer Vorrichtung zum Einstellen des Speisewassermassenstroms Ṁ ein Sollwert Ṁ s für den Speisewassermassenstrom Ṁ zugeführt wird. Sie bezieht sich weiterhin auf einen Zwangdurchlaufdampferzeuger zur Durchführung des Verfahrens.The invention relates to a method for operating a continuous steam generator with a Verdampferheizfläche, wherein a device for adjusting the feedwater mass flow Ṁ a setpoint Ṁ s for the feedwater mass flow Ṁ is supplied. It further relates to a forced once-through steam generator for carrying out the method.

In einem Durchlaufdampferzeuger führt die Beheizung einer Anzahl von Dampferzeugerrohren, die zusammen eine Verdampferheizfläche bilden, zu einer vollständigen Verdampfung eines Strömungsmediums in den Dampferzeugerrohren in einem Durchgang. Das Strömungsmedium - üblicherweise Wasser - wird dabei in der Regel vor seiner Verdampfung einem der Verdampferheizfläche strömungsmediumsseitig vorgeschalteten Vorwärmer, üblicherweise auch als Economizer bezeichnet, zugeführt und dort vorgewärmt.In a continuous steam generator, the heating of a number of steam generator tubes, which together form an evaporator heating surface, leads to a complete evaporation of a flow medium in the steam generator tubes in one pass. The flow medium - usually water - is usually before its evaporation to the Verdampferheizfläche flow medium side upstream preheater, commonly referred to as economizer, fed and preheated there.

Abhängig vom Betriebszustand des Durchlaufdampferzeugers und damit zusammenhängend von der aktuellen Dampferzeugerleistung wird der Speisewassermassenstrom in die Verdampferheizfläche geregelt. Bei Laständerungen sollte der Verdampferdurchfluss möglichst synchron zum Wärmeeintrag in die Verdampferheizfläche geändert werden, weil sonst eine Abweichung der spezifischen Enthalpie des Strömungsmediums am Austritt der Verdampferheizfläche vom Sollwert nicht sicher vermieden werden kann. Eine solche unerwünschte Abweichung der spezifischen Enthalpie erschwert die Regelung der Temperatur des aus dem Dampferzeuger austretenden Frischdampfes und führt darüber hinaus zu hohen Materialbelastungen und somit zu einer reduzierten Lebensdauer des Dampferzeugers.Depending on the operating state of the continuous steam generator and, consequently, on the current steam generator capacity, the feedwater mass flow is regulated in the evaporator heating surface. When load changes, the evaporator flow should be changed as synchronously as possible to the heat input into the evaporator, because otherwise a deviation of the specific enthalpy of the flow medium at the outlet of the evaporator from the target value can not be reliably avoided. Such an undesirable deviation of the specific enthalpy makes it difficult to regulate the temperature of the live steam emerging from the steam generator and moreover leads to high material loads and thus to a reduced service life of the steam generator.

Um Abweichungen der spezifischen Enthalpie vom Sollwert und daraus resultierende unerwünscht große Temperaturschwankungen in allen Betriebszuständen des Dampferzeugers, also insbesondere auch in transienten Zuständen oder bei Lastwechseln, möglichst gering zu halten, kann die Speisewasserdurchflussregelung in der Art einer so genannten prädiktiven oder vorausschauenden Auslegung ausgestaltet sein. Dabei sollen insbesondere auch bei Lastwechseln die notwendigen Speisewassersollwerte in Abhängigkeit vom aktuellen oder für die nächste Zukunft zu erwartenden Betriebszustand bereitgestellt werden.In order to minimize deviations of the specific enthalpy from the desired value and resulting undesirable large temperature fluctuations in all operating states of the steam generator, that is, in particular in transient states or during load changes, the feedwater flow control can be designed in the manner of a so-called predictive or predictive design. In particular, the required feedwater desired values should also be provided during load changes as a function of the current or expected future operating state.

Aus der EP 0639 253 ist ein Durchlaufdampferzeuger bekannt, bei dem der Speisewasserdurchfluss über eine Vorausberechnung der benötigten Speisewassermenge geregelt wird. Als Grundlage für das Berechnungsverfahren dient dabei die Wärmestrombilanz der Verdampferheizfläche, in die der Speisewassermassenstrom insbesondere am Eintritt der Verdampferheizfläche eingehen sollte. Der Sollwert für den Speisewassermassentrom wird dabei aus dem Verhältnis aus dem aktuell in der Verdampferheizfläche vom Heizgas auf das Strömungsmedium übertragenen Wärmestrom einerseits und einer im Hinblick auf den gewünschten Frischdampfzustand vorgegebenen Soll-Enthalpieerhöhung des Strömungsmediums in der Verdampferheizfläche andererseits vorgegeben.From the EP 0639 253 a continuous-flow steam generator is known, in which the feedwater flow is controlled by a preliminary calculation of the required feedwater quantity. The basis for the calculation method is the heat flow balance of the evaporator heating surface into which the feedwater mass flow should enter, in particular at the inlet of the evaporator heating surface. The desired value for the feedwater mass flow is determined from the ratio of the heat flow currently transferred to the flow medium by the heating gas in the evaporator heating surface and a desired enthalpy increase of the flow medium in the evaporator heating surface given with respect to the desired live steam state.

In der Praxis erweist sich die Messung des Speisewassermassenstroms unmittelbar am Eintritt der Verdampferheizfläche jedoch als technisch aufwendig und nicht in jedem Betriebszustand zuverlässig durchführbar. Statt dessen wird ersatzweise der Speisewassermassenstrom am Eintritt des Vorwärmers gemessen und in die Berechnungen der Speisewassermenge einbezogen, der jedoch nicht in jedem Fall gleich dem Speisewassermassenstrom am Eintritt der Verdampferheizfläche ist.In practice, however, the measurement of the feedwater mass flow directly at the entrance of the evaporator heating surface proves to be technically complex and not reliably feasible in any operating condition. Instead, the feedwater mass flow at the inlet of the preheater is alternatively measured and included in the calculations of the feedwater quantity, which however is not always equal to the feedwater mass flow at the inlet of the evaporator heating surface.

Um den hierdurch bedingten Ungenauigkeiten bei der Vorgabe eines insbesondere bei Lastwechseln besonders bedarfsgerechten Sollwerts für den Speisewassermassenstrom zu begegnen, ist bei einem alternativen Konzept einer prädiktiven Massenstromregelung, wie es aus der WO 2006/005708 A1 bekannt ist, vorgesehen, als eine der Eingangsgrößen für die Speisewasserdurchflussregelung die Speisewasserdichte am Eintritt des Vorwärmers zu berücksichtigen.In order to counteract the resulting inaccuracies in the specification of a particularly needs-based setpoint for the feedwater mass flow, in particular during load changes, is in an alternative concept of predictive mass flow control, as is known from the WO 2006/005708 A1 is known, provided as one of the input variables for the feedwater flow control to take into account the feedwater density at the inlet of the preheater.

Beide genannten Konzepte für eine prädiktive Massenstromregelung basieren als wesentliche Eingangsgröße auf dem Sollwert für die Dampferzeugerleistung, aus dem anhand hinterlegter Korrelationen und insbesondere unter Rückgriff auf zuvor gewonnene Eich- oder Referenzmessungen die in die eigentliche Sollwertbestimmung einfließenden Kennwerte errechnet werden. Dies setzt jedoch ausreichend stabile und eindeutig auf eine Feuerungsleistung zurückführbare Systemeigenschaften insgesamt voraus, wie sie üblicherweise bei gefeuerten Dampferzeugern vorliegen. In anderen Systemen, wie beispielsweise bei einer Auslegung des Durchlaufdampferzeugers als Abhitzekessel zur Wärmerückgewinnung aus dem Rauchgas einer vorgeschalteten Gasturbine, liegen derartige Verhältnisse jedoch nicht vor. Zudem ist bei derartigen, als Abhitzekessel geschalteten Systemen eine Feuerungsleistung nicht im selben Maße als freier Parameter nutzbar wie bei direkt gefeuerten Kesseln, da bei einer Verschaltung als Abhitzekessel üblicherweise als primäres Kriterium zur Steuerung der Gesamtanlage der Betrieb der Gasturbine angesehen wird, an deren Systemzustand die anderen Komponenten angepasst werden.Both of these concepts for a predictive mass flow control are based as essential input variable on the setpoint value for the steam generator power, from which the characteristic values flowing into the actual setpoint determination are calculated on the basis of stored correlations and in particular by recourse to previously obtained calibration or reference measurements. However, this requires sufficiently stable and clearly attributable to a firing capacity overall system properties, as is usually the case with fired steam generators. In other systems, such as in a design of the continuous steam generator as a waste heat boiler for heat recovery from the flue gas of an upstream gas turbine, such conditions are not available. In addition, in such, connected as waste heat boiler systems a firing capacity can not be used to the same extent as a free parameter as in directly fired boilers, as in an interconnection as waste heat boiler usually considered as the primary criterion for controlling the entire system operation of the gas turbine, the system state of the be adapted to other components.

Der Erfindung liegt daher die Aufgabe zugrunde, ein Verfahren zum Betreiben eines Dampferzeugers der oben genannten Art anzugeben, das bei vergleichsweise gering gehaltenem Aufwand auch bei einem Betrieb des Dampferzeugers als Abhitzekessel eine besonders gut an den aktuellen oder erwarteten Wärmeeintrag in die Verdampferheizfläche angepasste Einstellung des Speisewassermassenstroms durch die Verdampferheizfläche ermöglicht. Des Weiteren soll ein für die Durchführung des Verfahrens besonders geeigneter Zwangdurchlaufdampferzeuger angegeben werden.The invention is therefore an object of the invention to provide a method for operating a steam generator of the type mentioned above, with a comparatively low cost even when operating the steam generator as a waste heat boiler a particularly well adapted to the current or expected heat input into the evaporator heating adjustment of the feedwater mass flow allowed by the evaporator heating. Furthermore, a particularly suitable for the implementation of the method forced circulation steam generators should be specified.

Bezüglich des Verfahrens wird diese Aufgabe erfindungsgemäß gelöst, indem der vom Heizgas auf das Strömungsmedium übertragene Wärmestrom unter Berücksichtigung eines für die aktuelle Temperatur des Heizgases am Verdampfereintritt charakteristischen Temperaturkennwerts und eines für den aktuellen Massenstrom des Heizgases charakteristischen Massenstromkennwerts ermittelt wird.With regard to the method, this object is achieved according to the invention by determining the heat flow transferred from the heating gas to the flow medium taking into account a temperature characteristic value characteristic of the actual temperature of the heating gas at the evaporator inlet and a mass flow characteristic characteristic of the current mass flow of the heating gas.

Die Erfindung geht dabei von der Überlegung aus, dass eine auch für als Abhitzekessel geschaltete Dampferzeuger nutzbare, ausreichend zuverlässige prädiktive Massenstromregelung weit gehend an die Besonderheiten des Abhitzekessels angepasst werden sollte. Dabei sollte insbesondere berücksichtigt werden, dass anders als bei gefeuerten Kesseln in diesem Fall die Feuerungsleistung kein geeigneter Parameter ist, der einen ausreichend zuverlässigen Rückschluss auf die zugrunde liegende Wärmestrombilanz zulässt. Insbesondere sollte dabei berücksichtigt werden, dass bei einer für Abhitzekessel äquivalenten Größe, nämlich der aktuellen Gasturbinenleistung oder mit dieser korrelierender Parameter, noch weitere, gasturbineninterne Parameter hinzutreten können, so dass anhand dieser Größen kein akzeptabler Rückschluss auf die Enthalpieverhältnisse beim Eintritt des Heizgases in den Rauchgaskanal des Dampferzeugers möglich ist. Bei der zur Ermittlung des benötigten Speisewasserstroms zugrunde gelegten Wärmestrombilanz sollte daher auf andere, besonders geeignete Parameter zurückgegriffen werden. Hierzu sind vorliegend die Heizgastemperatur beim Eintritt in den Verdampfer sowie der Massenstrom des Heizgases vorgesehen.The invention is based on the consideration that a useful, sufficiently reliable predictive mass flow control should also be adapted to the particular features of the waste heat boiler as well as for waste heat boiler switched steam generator. Particular attention should be paid to the fact that unlike fired boilers in this case, the firing capacity is not a suitable parameter that allows a sufficiently reliable conclusion on the underlying heat flow balance. In particular, it should be taken into account that with an equivalent size for waste heat boilers, namely the current gas turbine performance or with this correlating parameters, further, gas turbine internal parameters may occur, so that on the basis of these sizes no acceptable conclusion on the enthalpy when entering the heating gas in the flue gas duct the steam generator is possible. The heat flow balance used to determine the required feedwater flow should therefore be based on other, particularly suitable parameters. For this purpose, in the present case, the heating gas temperature when entering the evaporator and the mass flow of the heating gas are provided.

Auf diese Weise ist eine vorgesteuerte Berechnung der erforderlichen Speisewassermenge auf der Grundlage einer Wärmestrombilanzierung des Verdampfers, die gegebenenfalls optional auch nachfolgende Überhitzerheizflächen miteinbeziehen kann, ermöglicht. Der für die aktuelle Temperatur des Heizgases am Verdampfereintritt charakteristische Temperaturkennwert ermöglicht dabei insbesondere die Ermittlung eines besonders zuverlässigen und somit bedarfsgerechten Kennwerts für die Heizgasenthalpie am Verdampfereintritt unter Berücksichtigung der Heizgasenthalpie am Verdampferauslass, die ihrerseits anhand des für den aktuellen Massenstrom charakteristischen Massenstromkennwerts berechnet werden kann, und damit eine besonders zuverlässige und bedarfsgerechte Ermittlung des aktuellen Wärmeangebots- oder -übertrags vom Heizgas auf das Speisewasser. Aus dieser kann unter Berücksichtigung der vorgegebenen Soll-Enthalpieerhöhung, also insbesondere der Differenz zwischen der unter Berücksichtigung der gewünschten Frischdampfparameter ermittelten Soll-Enthalpie des Strömungsmediums am Verdampferaustritt und der aus geeigneten Messwerten wie beispielsweise Druck und Temperatur ermittelten Ist-Enthalpie am Verdampfereintritt, die gewünschte Soll-Enthalpieerhöhung des Strömungsmediums in der Verdampferheizfläche ermittelt werden, wobei aus dem Verhältnis dieser Größen ein hierzu geeigneter Sollwert für den Speisewassermassenstrom errechnet werden kann.In this way, a pilot-controlled calculation of the required feedwater quantity is made possible on the basis of a heat flow balance of the evaporator, which may optionally also optionally include subsequent superheater heating surfaces. The temperature characteristic characteristic of the actual temperature of the heating gas at the evaporator inlet In this case, it is possible in particular to determine a particularly reliable characteristic value for the heating gas enthalpy at the evaporator inlet taking into account the heating gas enthalpy at the evaporator outlet, which in turn can be calculated from the mass flow characteristic characteristic of the current mass flow, and thus a particularly reliable and needs-based determination of the current heat supply. or carry-over from the fuel gas to the feed water. From this, taking into account the predetermined desired enthalpy increase, that is to say in particular the difference between the desired enthalpy of the flow medium at the evaporator outlet determined taking into account the desired live steam parameters and the actual enthalpy at the evaporator inlet determined from suitable measured values such as, for example, pressure and temperature, the desired value -Enthalpieerhöhung the flow medium can be determined in the evaporator, wherein from the ratio of these sizes a suitable setpoint for the feedwater mass flow can be calculated.

Als charakteristischer Temperaturkennwert und/oder als charakteristischer Massenstromkennwert zur geeigneten quantitativen Beschreibung des in den Verdampfer eintretenden Heizgases wird vorzugsweise ein für die aktuelle Situation besonders repräsentativer Kennwert berücksichtigt. Derartige Kennwerte können anhand aktuell vorliegender Messdaten geeignet ermittelt und insbesondere unter Rückgriff auf hinterlegte Speicherkennwerte geeignet bereitgestellt werden. Eine besonders zuverlässige Auswertung der Wärmestrombilanz und somit die Ermittlung eines besonders genau vorausberechneten Speisewasser-Sollwerts ist aber ermöglicht, indem vorteilhafterweise als charakteristischer Temperaturkennwert und/oder als charakteristischer Massenstromkennwert jeweils ein aktuell erfasster Messwert berücksichtigt wird.As a characteristic temperature characteristic and / or as a characteristic mass flow characteristic value for a suitable quantitative description of the hot gas entering the evaporator, a characteristic value which is particularly representative of the current situation is preferably taken into account. Such characteristic values can be suitably determined on the basis of currently available measurement data and can be made available in a suitable manner, in particular with recourse to stored memory characteristic values. However, a particularly reliable evaluation of the heat flow balance and thus the determination of a particularly precisely calculated feedwater desired value is made possible by advantageously taking into account in each case a currently measured value as a characteristic temperature characteristic and / or as a characteristic mass flow characteristic.

Der vom Heizgas auf das Strömungsmedium übertragene Wärmestrom wird vorteilhafterweise anhand einer Wärmestrombilanz ermittelt, bei der als wesentliche Eingangsgröße die Enthalpiedifferenz des Heizgases zwischen Verdampfereintritt und Verdampferaustritt zugrunde gelegt wird. Für eine besonders zuverlässige Kennwertberechnung wird dabei in weiterer vorteilhafter Ausgestaltung aber auch noch berücksichtigt, dass die durch diese Enthalpiedifferenz wiedergegebene Senkung des Energieinhalts im Rauchgas beim Durchtritt durch die Verdampferheizfläche zwar einerseits zu einer Enthalpieerhöhung im Strömungsmedium innerhalb der Verdampferheizfläche, andererseits aber auch zu Energieein- und/oder Ausspeichereffekten in den Bauteilen des Verdampfers, also insbesondere in den Dampferzeugerrohren und sonstigen metallischen Komponenten, führen kann. Für eine besonders zuverlässige Ermittlung der tatsächlich auf das Strömungsmedium innerhalb der Verdampferheizfläche übertragenen Enthalpiedifferenz wird dieser Aspekt der Energieein- und/oder Ausspeicherung von Wärme in den Metallmassen geeignet als charakteristischer Korrekturwert berücksichtigt, um den die Enthalpiedifferenz des Heizgases geeignet modifiziert wird.The transferred from the heating gas to the flow medium heat flow is advantageously based on a heat flow balance determined, in which the enthalpy difference of the hot gas between evaporator inlet and evaporator outlet is used as the essential input variable. For a particularly reliable characteristic calculation is also considered in a further advantageous embodiment but also that reproduced by this enthalpy difference lowering of the energy content in the flue gas when passing through the Verdampferheizfläche on the one hand to an enthalpy in the flow medium within the Verdampferheizfläche, on the other hand also to Energieein- and / or Ausstichereffekten in the components of the evaporator, ie in particular in the steam generator tubes and other metallic components, can lead. For a particularly reliable determination of the enthalpy difference actually transferred to the flow medium within the evaporator heating surface, this aspect of the energy input and / or outflow of heat in the metal masses is suitably taken into account as a characteristic correction value by which the enthalpy difference of the heating gas is suitably modified.

Bei der Ermittlung der Enthalpiedifferenz des Heizgases wird vorteilhafterweise die aktuelle Enthalpie des Heizgases am Verdampferaustritt berücksichtigt, indem sie anhand des Drucks des Strömungsmediums am Verdampfereintritt unter Berücksichtigung für den aktuellen Massenstrom des Heizgases charakteristischen Massenstromkennwerts ermittelt wird. Der Massenstromkennwert, der dabei vorzugsweise in Form eines Messwerts vorliegt, alternativ aber auch mittelbar über weitere Parameter unter Rückgriff auf hinterlegte Korrelations- oder sonstige Kennwerte errechnet werden kann, wird dabei vorteilhafterweise zunächst in den so genannten "Pinchpoint" des Dampferzeugers, also in die Temperaturdifferenz zwischen der Austrittstemperatur des Rauchgases und der Siedetemperatur des Strömungsmediums am Verdampfereintritt umgerechnet, wobei diese Temperaturdifferenz zweckmäßigerweise zu einer anhand des Drucks am Verdampfereintritt ermittelten Siedetemperatur des Strömungsmediums hinzuaddiert und aus dieser Summe die Enthalpie des Heizgases am Verdampferaustritt ermittelt wird.When determining the enthalpy difference of the hot gas, the current enthalpy of the hot gas at the evaporator outlet is advantageously taken into account by being determined on the basis of the pressure of the flow medium at the evaporator inlet taking into account the characteristic mass flow characteristic value for the current mass flow of the hot gas. The mass flow characteristic, which is preferably present in the form of a measured value, but alternatively can also be calculated indirectly via further parameters by using stored correlation or other characteristic values, is advantageously first in the so-called "pinch point" of the steam generator, ie in the temperature difference converted between the outlet temperature of the flue gas and the boiling temperature of the flow medium at the evaporator inlet, said temperature difference advantageously added to a determined based on the pressure at the evaporator inlet boiling temperature of the flow medium and from this sum the enthalpy of the heating gas at the evaporator outlet is determined.

Der Ermittlung der Soll-Enthalpieerhöhung des Strömungsmediums in der Verdampferheizfläche wird vorteilhafterweise einerseits anhand geeigneter Messwerte wie beispielsweise des Drucks und der Temperatur des Strömungsmediums beim Verdampfereintritt die ermittelte Ist-Enthalpie zugrunde gelegt. Zusätzlich wird in Abhängigkeit oder unter Berücksichtigung des gewünschten Dampfzustands, beispielsweise der spezifizierten Dampfparameter oder auch des Dampfgehalts am Verdampferaustritt, unter Berücksichtigung des aktuellen Drucks des Strömungsmediums am Austritt der Verdampferheizfläche ein Sollwert für dessen Enthalpie am Verdampferaustritt vorgegeben.The determination of the desired enthalpy increase of the flow medium in the evaporator heating surface is advantageously based, on the one hand, on the basis of suitable measured values, for example the pressure and the temperature of the flow medium at the evaporator inlet, the determined actual enthalpy. In addition, depending on or taking into account the desired steam state, for example the specified steam parameter or the vapor content at the evaporator outlet, taking into account the actual pressure of the flow medium at the outlet of the evaporator heating a setpoint for its enthalpy at the evaporator outlet is specified.

Der Durchlaufdampferzeuger kann dabei in einem so genannten "Benson-Kontroll-Modus" betrieben werden. Dabei liegt zwar im Regelfall im "Benson-Kontroll-Modus" am Austritt der Verdampferheizfläche Überhitzung des Strömungsmediums vor. Es kann jedoch in diesem Modus die Überspeisung eines der Verdampferheizfläche nachgeschalteten Wasserspeichers in Kauf genommen und den nachfolgenden Heizflächen teilweise noch unverdampftes Strömungsmedium zugeführt werden, so dass erst in den nachfolgenden Heizflächen die vollständige Verdampfung des Strömungsmediums erfolgt. In einem derartigen Modus kann insbesondere als gewünschter Dampfparameter die Einstellung einer um eine vorgegebene Temperaturdifferenz von beispielsweise 35 °C oberhalb der Sättigungstemperatur des Strömungsmediums liegenden Solltemperatur für das Strömungsmedium am Austritt des Verdampfers vorgegeben werden. Gerade bei einer derartigen Betriebsweise des Dampferzeugers kann es wünschenswert sein, den aktuellen Betriebszustand von der Verdampferheizfläche nachgeschalteten Überhitzerheizflächen zugeordneten Einspritzkühlern geeignet zu berücksichtigen, indem deren Kühlbedarf auf eine geeignete Mehrbespeisung des Systems mit Speisewasser verlagert wird. Dazu wird vorteilhafterweise bei der Vorgabe des Sollwerts für die Enthalpie des Strömungsmediums am Austritt der Verdampferheizfläche ein aktueller Kühlbedarf bei der Verdampferheizfläche nachgeschalteten Einspritzkühlern berücksichtigt. Die Soll-Frischdampf-Temperatur soll somit insbesondere so weit wie möglich durch eine geeignete Einstellung des Speisewasserstroms erreicht werden, so dass der zusätzliche Kühlbedarf bei den Einspritzkühlern besonders gering gehalten werden kann. Umgekehrt kann auch für den Fall, dass eine zu geringe Frischdampf-Temperatur festgestellt wird, der Enthalpie-Sollwert des Strömungsmediums am Verdampferaustritt geeignet erhöht werden, so dass eine entsprechend gering bemessene Speisewassermenge über den solchermaßen geänderten Sollwert für den Speisewassermassenstrom zugeführt wird.The continuous steam generator can be operated in a so-called "Benson control mode". As a rule, in the "Benson control mode" at the outlet of the evaporator heating surface, overheating of the flow medium is present. However, in this mode, the overfeeding of a water storage tank connected downstream of the evaporator heating surface can be accepted, and the subsequent heating surfaces can still be partially supplied with unevaporated flow medium, so that complete evaporation of the flow medium takes place only in the subsequent heating surfaces. In such a mode, the setting of a setpoint temperature for the flow medium at the outlet of the evaporator lying above the saturation temperature of the flow medium by a predetermined temperature difference of, for example, 35 ° C. above the saturation temperature of the flow medium can be specified in particular as the desired steam parameter. Especially with such an operation of the steam generator, it may be desirable to take into account the current operating condition of the evaporator heating surface downstream superheater heating associated injectors suitable by the cooling demand is shifted to a suitable Mehrbespeisung the system with feed water. This is advantageously in the specification of the target value for the enthalpy the flow medium at the outlet of the evaporator heating considered a current cooling demand in the evaporator heating downstream injection coolers. The desired live steam temperature should therefore be achieved in particular as far as possible by a suitable adjustment of the feedwater flow, so that the additional cooling requirement in the injection coolers can be kept particularly low. Conversely, even in the event that a too low steam temperature is detected, the enthalpy setpoint of the flow medium at the evaporator outlet are suitably increased, so that a correspondingly small amount of feed water is supplied via the thus changed setpoint for the feedwater mass flow.

Alternativ kann der Dampferzeuger auch in einem so genannten "Level Control Mode" betrieben werden, bei dem der Wasserstand in einem der Verdampferheizfläche nachgeschalteten Wasserspeicher variiert und nachgeregelt wird, wobei ein Überspeisen des Wasserspeichers möglichst vermieden werden sollte. Dabei wird der Wasserstand innerhalb des Wasserspeichers soweit möglich in einem vorgegebenen Sollbereich gehalten, wobei in vorteilhafter Ausgestaltung für den Sollwert für den Speisewassermassenstrom ein Füllstands-Korrekturwert berücksichtigt wird, der die Abweichung des Iststands des Füllstands im Wasserspeicher von einem zugeordneten Sollwert charakterisiert.Alternatively, the steam generator can also be operated in a so-called "level control mode" in which the water level is varied and readjusted in a water storage tank connected downstream of the evaporator heating surface, wherein overflow of the water storage tank should be avoided as far as possible. In this case, the water level within the water reservoir is kept as far as possible in a predetermined desired range, in an advantageous embodiment for the setpoint for the feedwater mass flow, a level correction value is taken into account, which characterizes the deviation of the actual level of the fill in the water storage of an associated setpoint.

Bezüglich des Zwangdurchlaufdampferzeugers wird die genannte Aufgabe gelöst, indem eine einer Vorrichtung zum Einstellen des Speisewassermassenstroms zugeordnete Speisewasserdurchflussregelung zur Vorgabe des Sollwerts für den Speisewassermassenstrom anhand des genannten Verfahrens ausgelegt ist. Der Zwangdurchlaufdampferzeuger ist dabei in besonders vorteilhafter Weise als Abhitzedampferzeuger ausgestaltet, der heizgasseitig mit dem Abgas aus einer zugeordneten Gasturbinenanlage beaufschlagt ist.With regard to the once-through steam generator, the stated object is achieved by designing a feedwater flow control system assigned to a device for adjusting the feedwater mass flow for specifying the desired value for the feedwater mass flow on the basis of said method. The forced-circulation steam generator is designed in a particularly advantageous manner as a heat recovery steam generator, which is acted upon the hot gas side with the exhaust gas from an associated gas turbine plant.

Die mit der Erfindung erzielten Vorteile bestehen insbesondere darin, dass durch die gezielte Berücksichtigung eines für die aktuelle Temperatur des Rauchgases beim Eintritt in den Heizgaskanal und/oder für den aktuellen Massenstrom des Rauchgases charakteristischen Kennwerts eine prädiktive oder vorbeugende Bestimmung eines am erwarteten Bedarf besonders weit gehend orientierten Speisewasser-Massenstromsollwerts ermöglicht ist, wobei selbst für den Fall einer Nutzung des Dampferzeugers als Abhitzekessel und einer demzufolge nur mangelnden Korrelation der entsprechenden Enthalpiekennwerte mit dem Leistungs- oder Förderungskennwert der Anlage ein besonders zuverlässiges und stabiles Regelverhalten erreichbar ist. Damit ist eine besonders zuverlässige prädiktive Anpassung des Speisewasserdurchflusses durch die Verdampferheizfläche an den aktuellen oder erwarteten Wärmeeintrag der Dampferheizfläche auf besonders einfache und zuverlässige Weise in allen möglichen Betriebszuständen des Durchlaufdampferzeugers ermöglicht, wobei insbesondere die Abweichung der spezifischen Enthalpie des Strömungsmediums am Austritt der Verdampferheizfläche vom Sollwert besonders gering gehalten werden kann.The advantages achieved by the invention are, in particular, that a predictive or preventive determination of the anticipated need is particularly far-reaching by the specific consideration of a characteristic of the current temperature of the flue gas when entering the Heizgaskanal and / or for the current mass flow of the flue gas oriented feedwater mass flow set point is possible, whereby even in the case of use of the steam generator as a waste heat boiler and consequently only a lack of correlation of the corresponding enthalpy characteristics with the power or delivery characteristic of the system a particularly reliable and stable control behavior can be achieved. Thus, a particularly reliable predictive adjustment of the feedwater flow through the evaporator to the current or expected heat input of Dampferheizfläche in a particularly simple and reliable manner in all possible operating conditions of the continuous steam generator allows, in particular the deviation of the specific enthalpy of the flow medium at the outlet of the evaporator heating surface from the setpoint especially can be kept low.

Ein Ausführungsbeispiel der Erfindung wird anhand einer Zeichnung näher erläutert. Darin zeigen:

FIG 1 und 2
jeweils einen Zwangdurchlaufdampferzeuger mit zugeordneter Speisewasserdurchflussregelung.
Gleiche Teile sind in beiden Figuren mit denselben Bezugszeichen versehen.An embodiment of the invention will be explained in more detail with reference to a drawing. Show:
1 and 2
each one forced flow steam generator with associated feedwater flow control.
Identical parts are provided in both figures with the same reference numerals.

Die Zwangdurchlaufdampferzeuger 1, 1' gemäß den FIG 1, 2 weisen jeweils einen auch als Economizer bezeichneten Vorwärmer 2 für als Strömungsmedium vorgesehenes Speisewasser auf, der sich in einem nicht näher dargestellten Gaszug befindet. Dem Vorwärmer 2 ist strömungsmediumsseitig eine Speisewasserpumpe 3 vor- und eine Verdampferheizfläche 4 nachgeschaltet. Ausgangsseitig ist die Verdampferheizfläche 4 strömungsmediumsseitig über einen Wasserspeicher 6, der insbesondere auch als Wasserabscheider oder Abscheideflasche ausgestaltet sein kann, mit einer Anzahl nachgeschalteter Überhitzerheizflächen 8, 10, 12 verbunden, die ihrerseits zur Anpassung der Dampftemperaturen und dergleichen mit Einspritzkühlern 14, 16 versehen sein können. Der Zwangdurchlaufdampferzeuger 1, 1' ist jeweils als Abhitzekessel oder Abhitzedampferzeuger ausgestaltet, wobei die Heizflächen, also insbesondere der Vorwärmer 2, die Verdampferheizfläche 4 sowie die Überhitzerheizflächen 8, 10, 12 in einem heizgasseitig mit dem Abgas aus einer zugeordneten Gasturbinenanlage beaufschlagten Heizgaskanal angeordnet sind.The once-through steam generator 1, 1 'according to the FIG. 1 . 2 each have a designated as economizer preheater 2 for intended as a flow medium feed water, which is located in a throttle cable, not shown. The preheater 2 is on the flow medium side, a feedwater pump 3 upstream and a Verdampferheizfläche 4 downstream. On the output side the Verdampferheizfläche 4 flow medium side via a water reservoir 6, which may be configured in particular as a water separator or Abscheideflasche connected to a number of downstream superheater 8, 10, 12, which in turn may be provided for adjusting the steam temperatures and the like with injection coolers 14, 16. The forced once-through steam generator 1, 1 'is configured in each case as a waste heat boiler or heat recovery steam generator, wherein the heating surfaces, ie in particular the preheater 2, the evaporator 4 and the superheater 8, 10, 12 are arranged in a hot gas channel acted upon by the gas from an associated gas turbine plant in a hot gas side.

Der Zwangdurchlaufdampferzeuger 1, 1' ist für eine geregelte Beaufschlagung mit Speisewasser ausgelegt. Dazu ist der Speisewasserpumpe 3 ein von einem Stellmotor 20 angesteuertes Drosselventil 22 nachgeschaltet, so dass über geeignete Ansteuerung des Drosselventils 22 die von der Speisewasserpumpe 3 in Richtung des Vorwärmers 2 geförderte Speisewassermenge oder der Speisewasser-Massenstrom einstellbar ist. Zur Ermittlung eines aktuellen Kennwerts für den zugeführten Speisewasser-Massenstrom ist dem Drosselventil 22 eine Messeinrichtung 24 zur Ermittlung des Speisewasser-Massenstroms Ṁ durch die Speisewasserleitung nachgeschaltet. Der Stellmotor 20 ist über ein Regelelement 28 angesteuert, das eingangsseitig mit einem über eine Datenleitung 30 zugeführten Sollwert Ṁ s für den Speisewasser-Massenstrom Ṁ und mit dem über eine Messeinrichtung 24 ermittelten aktuellen Istwert des Speisewasser-Massenstroms Ṁ beaufschlagt ist. Durch Differenzbildung zwischen diesen beiden Signalen wird an den Regler 28 ein Nachführungsbedarf übermittelt, so dass bei einer Abweichung des Ist- vom Sollwert eine entsprechende Nachführung des Drosselventils 22 über die Ansteuerung des Motors 20 erfolgt.The once-through steam generator 1, 1 'is designed for a regulated admission with feed water. For this purpose, the feedwater pump 3 is followed by a controlled by a servomotor 20 throttle valve 22, so that via suitable control of the throttle valve 22, the funded by the feedwater pump 3 in the direction of the preheater 2 feed water quantity or the feedwater mass flow is adjustable. To determine a current characteristic value for the supplied feedwater mass flow, the throttle valve 22 is followed by a measuring device 24 for determining the feedwater mass flow Ṁ through the feedwater line. The servo motor 20 is controlled via a control element 28, the input side is acted upon by a supplied via a data line 30 setpoint Ṁ s for the feedwater mass flow Ṁ and determined by a measuring device 24 actual value of the feedwater mass flow Ṁ . By forming the difference between these two signals, a tracking requirement is transmitted to the controller 28, so that in the case of a deviation of the actual from the nominal value, a corresponding tracking of the throttle valve 22 takes place via the activation of the motor 20.

Zur Ermittlung eines besonders bedarfsgerechten Sollwerts Ṁ s für den Speisewassermassenstrom Ṁ in der Art einer prädiktiven, vorausschauenden oder am zukünftigen oder aktuellen Bedarf orientierten Einstellung des Speisewassermassenstroms ist die Datenleitung 30 eingangsseitig mit einer zur Vorgabe des Sollwerts Ṁ s für den Speisewassermassenstrom Ṁ ausgelegten Speisewasserdurchflussregelung 32, 32' verbunden. Diese ist dafür ausgelegt, den Sollwert Ṁ s für den Speisewassermassenstrom Ṁ anhand einer Wärmestrombilanz in der Verdampferheizfläche 4 zu ermitteln, wobei der Sollwert Ṁ s für den Speisewassermassenstrom Ṁ anhand des Verhältnisses aus dem aktuell in der Verdampferheizfläche 4 vom Heizgas auf das Strömungsmedium übertragenen Wärmestrom einerseits und einer im Hinblick auf den gewünschten Frischdampfzustand vorgegebenen Soll-Enthalpieerhöhung des Strömungsmediums in der Verdampferheizfläche 4 andererseits vorgegeben wird. Eine Nutzung eines derartigen Konzepts der Bereitstellung eines Sollwerts für den Speisewassermassenstrom auf der Grundlage einer Wärmebilanz selbst für einen Zwangdurchlaufdampferzeuger 1, 1' in Bauweise als Abhitzekessel ist in den Ausführungsbeispielen gemäß FIG 1, FIG 2 insbesondere dadurch erreicht, dass der vom Heizgas auf das Strömungsmedium übertragene Wärmestrom unter Berücksichtigung eines für die aktuelle Temperatur des Heizgases am Verdampfereintritt charakteristischen Temperaturkennwerts und eines für den aktuellen Massenstrom des Heizgases charakteristischen Massenstromkennwerts ermittelt wird.To determine a particularly needs-based setpoint Ṁ s for the feedwater mass flow Ṁ in the form of a predictive, anticipatory or future or current need oriented adjustment of the feedwater mass flow the input line 30 with an input for setting the set value Ṁ s for the feedwater mass flow Spe feedwater flow control 32, 32 'connected. This is designed to determine the setpoint Ṁ s for the feedwater mass flow Ṁ based on a heat flow balance in the evaporator 4, wherein the setpoint Ṁ s for the feedwater mass flow Ṁ based on the ratio of the currently transferred in the evaporator 4 from the heating gas to the flow medium heat flow on the one hand and a desired enthalpy increase of the flow medium in the evaporator heating surface 4 predetermined with regard to the desired live steam state is predetermined on the other hand. A use of such a concept of providing a target value for the feedwater mass flow on the basis of a heat balance even for a once-through steam generator 1, 1 'in construction as a waste heat boiler is in the embodiments according to FIG. 1 . FIG. 2 in particular achieved in that the transferred from the heating gas to the flow medium heat flow is determined taking into account a characteristic of the current temperature of the heating gas at the evaporator inlet temperature characteristic and a characteristic of the current mass flow of the heating gas mass flow characteristic.

Dazu weist die Speisewasserdurchflussregelung 32 ein Dividierglied 34 auf, dem als Zähler ein geeigneter Kennwert für den aktuell in der Verdampferheizfläche 4 vom Heizgas auf das Strömungsmedium übertragenen Wärmestrom und als Nenner ein im Hinblick auf den gewünschten Frischdampfzustand geeignet vorgegebener Kennwert für die gewünschte Soll-Enthalpieerhöhung des Strömungsmediums in der Verdampferheizfläche 4 zugeführt wird. Zählerseitig ist das Dividierglied 34 dabei eingangsseitig mit einem Funktionsmodul 36 verbunden, das anhand eines zugeführten, für die aktuelle Temperatur des Heizgases am Verdampfereintritt charakteristischen Temperaturkennwerts als Ausgangswert einen Wert für die Enthalpie des Heizgases am Verdampfereintritt ausgibt. Im Ausführungsbeispiel ist dabei die Zuführung eines für die aktuelle Temperatur des Heizgases am Verdampfereintritt charakteristischen Messwerts als Temperaturkennwert vorgesehen. Der für die Enthalpie des Heizgases am Verdampfereinlass charakteristische Kennwert wird auf ein Subtrahierglied 38 ausgegeben, wo von diesem Kennwert ein von einem Funktionsmodul 40 gelieferter Kennwert für die Enthalpie des Gases am Verdampferauslass abgezogen wird.For this purpose, the feedwater flow control 32 to a divider 34, the numerator as a suitable characteristic for the currently transmitted in the evaporator 4 from the heating gas to the flow medium heat flow and as a denominator with respect to the desired live steam condition predetermined predetermined characteristic value for the desired desired enthalpy of the Flow medium is supplied in the evaporator 4. On the meter side, the divider 34 is connected on the input side to a function module 36, which is based on a supplied, characteristic of the current temperature of the hot gas at the evaporator inlet temperature characteristic value as output value outputs a value for the enthalpy of the hot gas at the evaporator inlet. In the exemplary embodiment, the supply of a measured value characteristic of the current temperature of the heating gas at the evaporator inlet is provided as a temperature characteristic value. The characteristic value which is characteristic of the enthalpy of the heating gas at the evaporator inlet is output to a subtractor 38, from which characteristic value a characteristic value for the enthalpy of the gas at the evaporator outlet provided by a function module 40 is subtracted.

Zur Ermittlung der Enthalpie des Heizgases am Verdampferauslass wird dem Funktionsglied 40 eingangsseitig von einem Summierglied 42 die Summe zweier Temperaturwerte gebildet. Dabei wird einerseits die über ein Funktionsglied 44, das eingangsseitig mit einem Drucksensor 46 verbunden ist, anhand des Drucks des Strömungsmediums beim Verdampfereintritt ermittelte Sättigungstemperatur des Strömungsmediums berücksichtigt. Andererseits wird über ein Funktionsglied 48, dem seinerseits eingangsseitig über ein weiteres Funktionsglied 50 ein für den aktuellen Massenstrom des Heizgases charakteristischer Massenstromkennwert zugeführt wird, der so genannte "Pinchpoint", nämlich die aus dem Massenstrom des Heizgases ermittelte Temperaturdifferenz der Heizgastemperatur am Verdampferaustritt minus der Siedetemperatur des Strömungsmediums am Verdampfereintritt, berücksichtigt. Aus diesen beiden über das Summierglied 42 addierten Temperaturbeiträgen wird vom Funktionsbaustein 40 somit die Enthalpie des Heizgases am Verdampferaustritt, gegebenenfalls unter Rückgriff auf geeignete Tabellen, Diagramme oder dergleichen, bereitgestellt. Ausgangsseitig liefert das Subtrahierglied 38 somit die Enthalpiedifferenz oder -bilanz des Heizgases, also die Differenz aus Heizgasenthalpie am Verdampfereintritt und Heizgasenthalpie am Verdampferaustritt.In order to determine the enthalpy of the heating gas at the evaporator outlet, the sum of two temperature values is formed on the input side of the functional element 40 by a summing element 42. On the one hand, the saturation temperature of the flow medium determined on the basis of the pressure of the flow medium at the evaporator inlet is taken into account via a functional element 44, which is connected on the input side to a pressure sensor 46. On the other hand, via a functional element 48, which in turn is fed via a further functional element 50 for the current mass flow of the fuel gas characteristic mass flow characteristic, the so-called "pinch point", namely the determined from the mass flow of the fuel gas temperature difference of the heating gas temperature at the evaporator outlet minus the boiling point the flow medium at the evaporator inlet, considered. From these two temperature contributions added via the summing element 42, the enthalpy of the heating gas at the evaporator outlet, optionally with reference to suitable tables, diagrams or the like, is thus provided by the function module 40. On the output side, the subtracting element 38 thus supplies the enthalpy difference or balance of the heating gas, that is to say the difference between the heating gas enthalpy at the evaporator inlet and the enthalpy of the heating gas at the evaporator outlet.

Diese Enthalpiedifferenz wird an ein Multiplizierglied 52 weitergegeben, dem ebenfalls der charakteristische Massenstromkennwert, der im Übrigen als aktuell erfasster Messwert vorliegen kann, ebenfalls zugeführt wird. Ausgangsseitig liefert das Multiplizierglied 52 somit einen Kennwert für die vom Rauchgas an die Verdampferheizfläche 4 abgegebene Wärmeleistung.This enthalpy difference is forwarded to a multiplier 52, which is also supplied with the characteristic mass flow characteristic value, which, incidentally, can be present as a currently measured value. On the output side, the multiplier 52 thus provides a characteristic value for the output from the flue gas to the evaporator 4 heat output.

Um anhand dieser vom Heizgas abgegebenen Wärmeleistung den tatsächlich auf das Strömungsmedium übertragenen Wärmestrom ermitteln zu können, ist zunächst noch eine Korrektur um Wärmeein- und/oder -ausspeichereffekte in die Komponenten der Verdampferheizfläche 4, insbesondere in die Metallmassen, vorgesehen. Dazu wird der genannte Kennwert für die vom Heizgas abgegebene Wärmeleistung zunächst einem Subtrahierglied 54 zugeführt, wo ein für die Wärmeein- oder -ausspeicherung in die Verdampferbauteile charakteristischer Korrekturwert abgezogen wird. Dieser wird von einem Funktionsglied 56 bereitgestellt. Dieses ist eingangsseitig seinerseits mit dem Ausgangswert eines weiteren Funktionsgliedes 58 beaufschlagt, indem ein mittlerer Temperaturwert für die Metallmassen der Verdampferheizfläche 4 ermittelt wird. Dazu ist das weitere Funktionsglied 58 eingangsseitig mit einem im Wasserspeicher 6 angeordneten Druckgeber 60 verbunden, so dass das weitere Funktionsglied 58 die mittlere Temperatur der Metallmassen anhand des Drucks des Strömungsmediums, z. B. durch Gleichsetzung mit der zu diesem Druck gehörigen Siedetemperatur, im Wasserspeicher 6 ermitteln kann.In order to be able to determine the actual heat flow transferred to the flow medium on the basis of this heat output from the heating gas, a correction for heat input and / or accumulation effects in the components of the evaporator heating surface 4, in particular in the metal masses, is initially provided. For this purpose, said characteristic value for the heat output emitted by the heating gas is first supplied to a subtracting element 54, where a correction value characteristic of the heat input or withdrawal into the evaporator components is subtracted. This is provided by a functional element 56. On the input side, this is in turn subjected to the output value of a further functional element 58, in that a mean temperature value for the metal masses of the evaporator heating surface 4 is determined. For this purpose, the further functional member 58 is connected on the input side to a pressure sensor 60 arranged in the water reservoir 6, so that the further functional member 58, the average temperature of the metal masses based on the pressure of the flow medium, for. B. by equating with the boiling temperature associated with this pressure in the water tank 6 can determine.

Ausgangsseitig übergibt das Subtrahierglied 54 somit einen für die vom Heizgas abgegebene Wärmeleistung, vermindert um die in das Metall der Verdampferheizfläche 4 eingespeicherte Wärmeleistung, und somit einen für die an das Strömungsmedium abzugebende Wärmeleistung charakteristischen Kennwert.On the output side, the subtracting member 54 thus transfers a heat output for the heating gas, reduced by the thermal power stored in the metal of the evaporator heating surface 4, and thus a characteristic characteristic of the heat output to be delivered to the flow medium.

Dieser Kennwert wird im Dividierglied 34 als Zähler verwendet, der dort durch einen Nenner geteilt wird, der einer im Hinblick auf den gewünschten Frischdampfzustand vorgegebenen Soll-Enthalpieerhöhung des Strömungsmediums in der Verdampferheizfläche 4 entspricht, so dass aus dieser Division oder diesem Verhältnis der Sollwert Ṁ s für den Speisewassermassenstrom Ṁ gebildet werden kann. Zur Bereitstellung des Nenners, also des Kennwerts für die gewünschte Soll-Enthalpieerhöhung auf der Wasser-Dampf- oder Strömungsmediumsseite, ist das Dividierglied 34 eingangsseitig mit einem Subtrahierglied 70 verbunden. Dieses ist eingangsseitig mit einem von einem Funktionsglied 72 bereitgestellten Kennwert für den gewünschten Sollwert für die Enthalpie des Strömungsmediums am Verdampferaustritt beaufschlagt. Des Weiteren ist das Subtrahierglied 70 eingangsseitig mit einem von einem Funktionsmodul 74 bereitgestellten Kennwert oder Istwert für die aktuelle Enthalpie des Strömungsmediums am Verdampfereintritt beaufschlagt, der im Subtrahierglied 70 vom genannten Kennwert für den Sollwert der Enthalpie am Verdampferaustritt abgezogen wird. Eingangsseitig ist das Funktionsmodul 74 dabei zur Bildung des genannten Kennwerts für die Ist-Enthalpie am Verdampfereintritt mit dem Drucksensor 46 und mit einem Temperatursensor 76 verbunden. Durch die Differenzbildung im Subtrahierglied 70 wird somit die in Abhängigkeit vom gewünschten Frischdampfzustand in das Strömungsmedium in der Verdampferheizfläche 4 einzubringende Enthalpieerhöhung ermittelt, die als Nenner im Dividierglied 34 verwendet werden kann.This characteristic is used in the divider 34 as a counter, which is divided there by a denominator, the one in the With regard to the desired live steam state, the predetermined desired enthalpy increase of the flow medium in the evaporator heating surface 4 corresponds, so that from this division or this ratio the desired value Ṁ s for the feedwater mass flow Ṁ can be formed. To provide the denominator, ie the characteristic value for the desired desired enthalpy increase on the water-steam or flow medium side, the divider 34 is connected on the input side to a subtractor 70. This is acted on the input side with a provided by a functional element 72 characteristic value for the desired setpoint for the enthalpy of the flow medium at the evaporator outlet. Furthermore, the subtracting element 70 is acted upon on the input side by a characteristic value or actual value for the current enthalpy of the flow medium at the evaporator inlet which is subtracted in the subtracter 70 from the characteristic value for the enthalpy at the evaporator outlet. On the input side, the function module 74 is connected to the pressure sensor 46 and to a temperature sensor 76 in order to form the characteristic value for the actual enthalpy at the evaporator inlet. As a result of the difference formation in the subtracting element 70, the enthalpy increase to be introduced as a function of the desired live steam state into the flow medium in the evaporator heating surface 4 is thus determined, which can be used as a denominator in the divider 34.

Der Zwangdurchlaufdampferzeuger 1 und der Zwangdurchlaufdampferzeuger 1' gemäß den FIG 1 bzw. 2 unterscheiden sich hinsichtlich der Ausgestaltung ihrer Speisewasserdurchflussregelung 32, 32' insbesondere bzgl. der Bildung des Sollwerts für die Enthalpie am Verdampferaustritt und somit hinsichtlich der eingangsseitigen Beaufschlagung des Funktionsmoduls 72. Der Zwangdurchlaufdampferzeuger 1 gemäß FIG 1 ist dabei für einen Betrieb im so genannten "Level Control Mode" ausgelegt, bei dem der Wasserstand im Wasserspeicher 6 geregelt wird, wobei an die dem der Verdampferheizfläche 4 nachgeschalteten Überhitzerheizflächen 8, 10, 12 ausschließlich Dampf weitergegeben wird, und das verdampferaustrittsseitig noch mitgeführte Wasser im Wasserspeicher 6 abgeschieden wird. In diesem Betriebsmodus wird das Funktionsmodul 72 eingangsseitig einerseits mit einem vom Drucksensor 60 gelieferten Messwert für den Druck im Wasserspeicher 6 beaufschlagt. Andererseits wird dem Funktionsmodul 72 über einen zugeordneten Eingang 78 ein für den gewünschten Frischdampfzustand charakteristischer Parameter, beispielsweise ein gewünschter Dampfgehalt am Verdampferaustritt, zugeführt. Aus diesem Parameter gemeinsam mit dem genannten Druckkennwert wird anschließend im Funktionsmodul 72 der Sollwert für die Enthalpie des Strömungsmediums am Verdampferaustritt gebildet.The once-through steam generator 1 and the once-through steam generator 1 'according to the FIG. 1 or 2 differ with regard to the design of their feedwater flow control 32, 32 'in particular with respect to the formation of the setpoint for the enthalpy at the evaporator outlet and thus with respect to the input-side loading of the functional module 72nd The forced flow steam generator 1 according FIG. 1 is designed for operation in the so-called "Level Control Mode", in which the water level is regulated in the water reservoir 6, wherein the superheater 8, 10, 12 connected downstream of the evaporator heating surface 4 exclusively Steam is passed, and the evaporator outlet side still entrained water in the water reservoir 6 is deposited. In this operating mode, the function module 72 is acted on the input side, on the one hand, with a measured value, supplied by the pressure sensor 60, for the pressure in the water reservoir 6. On the other hand, the function module 72 is supplied via an associated input 78 with a parameter characteristic of the desired live steam condition, for example a desired steam content at the evaporator outlet. From this parameter together with the mentioned pressure characteristic value, the desired value for the enthalpy of the flow medium at the evaporator outlet is subsequently formed in the function module 72.

Bei der Ausgestaltung nach FIG 1 liefert das Dividierglied 34 anhand der genannten Division ausgangsseitig einen Sollwert für den Speisewassermassenstrom, der anhand der genannten Wärmebilanz ausgerichtet und ermittelt ist. Dieser Sollwert wird anschließend in einem nachgeschalteten Addierglied 80 aber noch korrigiert um einen Korrekturwert, der eine über den Speisewasserzufluss gewünschte Veränderung des Pegelstands im Wasserspeicher 6 wiedergibt. Dazu wird der Pegelstand im Wasserspeicher 6 über einen Füllstandssensor 82 erfasst. Dieser Istwert für den Füllstand wird in einem Subtrahierglied 84 von einem hinterlegten oder auf andere Weise vorgebbaren Sollwert für den Füllstand im Wasserspeicher 6 abgezogen. Anhand der dabei festgestellten Abweichung des Iststands des Füllstands im Wasserspeicher 6 vom zugeordneten Sollwert wird in einem nachfolgenden Stellglied 86 ein effektiver Speisewasser-Massenstromwert ermittelt, mit dem der Wasserspeicher 6 zur Korrektur seines Füllstands beaufschlagt werden soll. Dieser Korrekturwert wird im Addierglied 80 zum anhand der Wärmestrombilanz ermittelten Sollwert für den Speisewassermassenstrom hinzuaddiert, so dass als Sollwert Ṁ s für den Speisewassermassenstrom ein aus beiden Anteilen zusammengesetzter Wert ausgegeben wird.In the embodiment according to FIG. 1 on the output side, the divider 34 supplies, on the output side, a desired value for the feedwater mass flow which is aligned and determined on the basis of the heat balance mentioned. This setpoint value is subsequently corrected in a subsequent adder 80 by a correction value which reproduces a desired change in the water level in the water reservoir 6 via the feedwater inflow. For this purpose, the water level in the water reservoir 6 is detected by a level sensor 82. This actual value for the fill level is subtracted in a subtractor 84 from a stored or otherwise presettable setpoint for the fill level in the water reservoir 6. Based on the determined deviation of the actual level of the liquid level in the water reservoir 6 from the assigned target value, an effective feedwater mass flow value is determined in a subsequent actuator 86, with which the water reservoir 6 is to be acted upon to correct its fill level. This correction value is added in the adder 80 to the reference value for the feedwater mass flow determined on the basis of the heat flow balance, so that a value composed of the two proportions is output as setpoint value Ṁ s for the feedwater mass flow.

Demgegenüber ist der Zwangdurchlaufdampferzeuger 1' gemäß FIG 2 für einen Betrieb im so genannten "Benson Control Modus" ausgelegt, bei dem eine Überspeisung des auch als Wasserabscheider vorgesehenen Wasserspeichers 6 und die vollständige Verdampfung des Strömungsmediums erst in den nachfolgenden Überhitzerheizflächen 8, 10, 12 möglich ist. Bei dieser Betriebsvariante wird das Funktionsglied 72, über das der Sollwert für die Enthalpie des Strömungsmediums am Verdampferaustritt ausgegeben werden soll, eingangsseitig ebenfalls einerseits mit dem vom Drucksensor 60 ermittelten Istwert für den Druck im Wasserabscheider 6 beaufschlagt. Weiterhin ist dem Funktionsmodul 72 eingangsseitig ein weiteres Funktionsmodul 90 vorgeschaltet, das anhand des vom Drucksensor 60 ermittelten Ist-Drucks im Wasserspeicher 6 anhand einer hinterlegten Funktionalität oder des gewünschten Frischdampfzustands einen geeigneten Sollwert für die Temperatur des Strömungsmediums im Wasserspeicher 6 ermittelt. Beispielsweise könnte für einen Betrieb der Anlage im "Benson Control Modus" als Sollwert für die Temperatur hierbei ein Temperaturwert hinterlegt sein, der der Sättigungstemperatur des Strömungsmediums beim ermittelten Druck zuzüglich einer vorgesehenen Mindestüberhitzung von beispielsweise 35 °C entspricht. Das Funktionsmodul 72 ermittelt aus diesem Sollwert für die Temperatur unter Berücksichtigung des aktuellen Druckwerts den genannten Sollwert für die Enthalpie des Strömungsmediums am Verdampferaustritt.In contrast, the forced once-through steam generator 1 'according to FIG. 2 designed for operation in the so-called "Benson Control Mode", in which an overfeed of the intended as a water separator 6 and the complete evaporation of the flow medium only in the following superheater 8, 10, 12 is possible. In this operating variant, the functional element 72, via which the setpoint value for the enthalpy of the flow medium is to be output at the evaporator outlet, likewise receives on the input side the pressure value in the water separator 6 determined by the pressure sensor 60 on the input side. Furthermore, the function module 72 is preceded on the input side by another functional module 90, which determines a suitable setpoint for the temperature of the flow medium in the water reservoir 6 on the basis of a stored functionality or the desired live steam condition based on the actual pressure in the water reservoir 6 determined by the pressure sensor 60. For example, for operation of the system in "Benson Control Mode", a temperature value may be stored as the setpoint for the temperature, which corresponds to the saturation temperature of the flow medium at the determined pressure plus a predetermined minimum superheat of, for example, 35 ° C. The function module 72 determines from said setpoint value for the temperature, taking into account the current pressure value, said setpoint value for the enthalpy of the flow medium at the evaporator outlet.

Im Ausführungsbeispiel nach FIG 2 wird dieser vom Funktionsmodul 72 bereitgestellte Sollwert, der im Wesentlichen an den Eigenschaften des Strömungsmediums als solches orientiert ist, anschließend in einem nachgeschalteten Addierglied 92 noch um einen weiteren Korrekturwert verändert. Dieser von einem Funktionsmodul 94 gelieferte weitere Korrekturwert berücksichtigt im Wesentlichen in der Art einer Trimmfunktion die Abweichung der aktuell festgestellten Frischdampftemperatur von der im Hinblick auf den gewünschten Frischdampfzustand eigentlich gewünschten Frischdampftemperatur. Eine derartige Abweichung kann sich insbesondere dadurch bemerkbar machen, dass bei zu hoher Frischdampftemperatur in den Einspritzkühlern 14, 16 Kühlbedarf entsteht und somit die Beaufschlagung der Einspritzkühler 14, 16 mit Kühlmedium erforderlich ist. Falls ein derartiger Massenstrom zu den Einspritzkühlern 14, 16 festgestellt wird, ist es Auslegungsziel des Funktionsmoduls 94, diesen Kühlbedarf von den Einspritzkühlern 14, 16 weg und hin zu einer erhöhten Speisewasserzufuhr zu verlagern. Bei einem dementsprechend festgestellten Kühlbedarf in den Einspritzkühlern 14, 16 wird dementsprechend im Funktionsmodul 94 die gewünschte Enthalpie des Strömungsmediums am Verdampferaustritt abgesenkt, um den Kühlbedarf zu minimieren. Andernfalls, also wenn eine zu niedrige Frischdampftemperatur festgestellt wird, wird über den vom Funktionsmodul 94 bereitgestellten Korrekturwert und dessen Addition im Addiermodul 92 der Enthalpie-Sollwert erhöht.In the embodiment according to FIG. 2 This setpoint, which is provided by the function module 72 and is essentially oriented on the properties of the flow medium as such, is subsequently changed in a downstream adder 92 by a further correction value. This further correction value supplied by a function module 94 essentially takes into account, in the manner of a trim function, the deviation of the currently detected live steam temperature from the live steam temperature actually desired in view of the desired live steam condition. A Such a deviation can be made noticeable in particular by the fact that, if the live steam temperature is too high, cooling demand arises in the injection coolers 14, 16, and thus the admission of the injection coolers 14, 16 with cooling medium is required. If such a mass flow to the injection coolers 14, 16 is detected, it is the design goal of the functional module 94 to shift this cooling demand away from the injection coolers 14, 16 and towards an increased feedwater supply. In a correspondingly determined cooling demand in the injection coolers 14, 16, the desired enthalpy of the flow medium at the evaporator outlet is correspondingly lowered in the function module 94, in order to minimize the cooling requirement. Otherwise, ie if a steam temperature that is too low is detected, the enthalpy setpoint is increased via the correction value provided by the function module 94 and its addition in the adder module 92.

Zur Absicherung umfasst die Speisewasserdurchflussregelung 32' des Zwangdurchlaufdampferzeugers 1' nach FIG 2 noch eine nachgelagerte direkte Regelschleife, bei der in einem Funktionsmodul 100 anhand der Messwerte im Wasserspeicher 6 ein Istwert für die Enthalpie des Strömungsmediums am Verdampferaustritt ermittelt und in einem Differenziermodul 102 mit der gewünschten Enthalpie, also mit dem Soll-Enthalpiewert, verglichen wird. Durch die Differenzbildung im Differenziermodul 102 wird dabei die Soll-Ist-Abweichung festgestellt, die über einen nachgeschalteten Regler 104 in einem Addierglied 106 dem vom Dividierglied 34 bereitgestellten Sollwert für den Speisewassermassenstrom überlagert wird. Diese Überlagerung geschieht geeignet zeitlich verzögert und gedämpft, so dass dieser Regeleingriff lediglich im Bedarfsfall, also bei zu grober Regelabweichung, eingreift.To safeguard the feedwater flow control 32 'of the forced once-through steam generator 1' after FIG. 2 a downstream direct control loop, in which a value for the enthalpy of the flow medium at the evaporator outlet is determined in a function module 100 on the basis of the measured values in the water reservoir 6 and compared in a differentiation module 102 with the desired enthalpy, ie with the desired enthalpy value. As a result of the difference formation in the differentiation module 102, the setpoint-actual deviation is ascertained, which is superimposed, via a downstream regulator 104 in an adder 106, on the desired value for the feedwater mass flow provided by the divider 34. This superimposition is suitably delayed in time and damped, so that this control intervention only in case of need, so too rough control deviation, intervenes.

Claims (11)

Verfahren zum Betreiben eines Durchlaufdampferzeugers mit einer Verdampferheizfläche (4), bei dem einer Vorrichtung zum Einstellen des Speisewassermassenstroms (Ṁ) ein Sollwert (Ṁ s) für den Speisewassermassenstrom (Ṁ) zugeführt wird, der anhand des Verhältnisses aus dem aktuell in der Verdampferheizfläche (4) vom Heizgas auf das Strömungsmedium übertragenen Wärmestrom einerseits und einer im Hinblick auf den gewünschten Frischdampfzustand vorgegebenen Soll-Enthalpieerhöhung des Strömungsmediums in der Verdampferheizfläche (4) andererseits vorgegeben wird, wobei der vom Heizgas auf das Strömungsmedium übertragene Wärmestrom unter Berücksichtigung eines für die aktuelle Temperatur des Heizgases am Verdampfereintritt charakteristischen Temperaturkennwerts und eines für den aktuellen Massenstrom des Heizgases charakteristischen Massenstromkennwerts ermittelt wird.Method for operating a continuous steam generator with an evaporator heating surface (4), in which a setpoint value ( Ṁ s ) for the feedwater mass flow ( Ṁ ) is fed to a device for adjusting the feedwater mass flow ( Ṁ ), which is determined from the ratio in the evaporator heating surface (4) ) is given by the heating gas to the flow medium heat flow on the one hand and a predetermined with respect to the desired live steam state desired enthalpy of the flow medium in the evaporator (4) on the other hand, said transferred from the heating gas to the flow of heat flow taking into account one for the current temperature of the Heating gas at the evaporator inlet characteristic temperature characteristic value and a characteristic of the current mass flow of the fuel gas mass flow characteristic is determined. Verfahren nach Anspruch 1, bei dem als charakteristischer Temperaturkennwert und/oder als charakteristischer Massenstromkennwert jeweils ein aktueller Messwert berücksichtigt wird.The method of claim 1, wherein in each case a current measured value is taken into account as a characteristic temperature characteristic and / or as a characteristic mass flow characteristic. Verfahren nach Anspruch 1 oder 2, bei dem der vom Heizgas auf das Strömungsmedium übertragene Wärmestrom anhand der Enthalpiedifferenz des Heizgases zwischen Verdampfereintritt und Verdampferaustritt ermittelt wird.Method according to claim 1 or 2, in which the heat flow transferred from the heating gas to the flow medium is determined on the basis of the enthalpy difference of the heating gas between the evaporator inlet and the evaporator outlet. Verfahren nach Anspruch 3, bei dem die Enthalpiedifferenz des Heizgases zur Ermittlung des vom Heizgas auf das Strömungsmedium übertragenen Wärmestroms um einen für die Wärmeein- oder -ausspeicherung in die Verdampferbauteile charakteristischen Korrekturwert modifiziert wird.Method according to Claim 3, in which the enthalpy difference of the heating gas for determining the heat flow transferred to the flow medium by the heating gas is modified by a correction value characteristic of the heat input or withdrawal into the evaporator components. Verfahren nach Anspruch 3 oder 4, bei dem die aktuelle Enthalpie des Heizgases am Verdampferaustritt anhand des Drucks des Strömungsmediums am Verdampfereintritt unter Berücksichtigung des charakteristischen Massenstromkennwerts ermittelt wird.The method of claim 3 or 4, wherein the current enthalpy of the heating gas at the evaporator outlet on the basis of the pressure of the flow medium at the evaporator inlet under consideration the characteristic mass flow characteristic is determined. Verfahren nach einem der Ansprüche 1 bis 5, bei dem die Soll-Enthalpieerhöhung des Strömungsmediums in der Verdampferheizfläche (4) unter Berücksichtigung des aktuellen Drucks des Strömungsmediums am Austritt der Verdampferheizfläche (4) vorgegeben wird.Method according to one of claims 1 to 5, wherein the desired enthalpy increase of the flow medium in the evaporator heating surface (4), taking into account the current pressure of the flow medium at the outlet of the evaporator heating surface (4) is specified. Verfahren nach Anspruch 6, bei dem bei der Vorgabe des Sollwerts für die Enthalpie des Strömungsmediums am Austritt der Verdampferheizfläche (4) ein aktueller Kühlbedarf bei der Verdampferheizfläche (4) nachgeschalteten Einspritzkühlern (14, 16) berücksichtigt wird.The method of claim 6, wherein in the specification of the setpoint for the enthalpy of the flow medium at the outlet of the evaporator (4) a current cooling demand in the evaporator (4) downstream injection coolers (14, 16) is taken into account. Verfahren nach einem der Ansprüche 1 bis 7, bei dem für den Sollwert (Ṁ s) für den Speisewassermassenstrom (Ṁ) ein Füllstands-Korrekturwert berücksichtigt wird, der die Abweichung des Iststands des Füllstands in einem der Verdampferheizfläche (4) nachgeschalteten Wasserspeicher (6) von einem zugeordneten Sollwert charakterisiert.Method according to one of Claims 1 to 7, in which a fill level correction value is taken into account for the setpoint value ( Ṁ s ) for the feedwater mass flow ( Ṁ ), which determines the deviation of the actual level of the fill level in a water store (6) connected downstream of the evaporator heating surface (4). characterized by an associated setpoint. Verfahren nach einem der Ansprüche 1 bis 8, bei dem für den Sollwert (Ṁ s) für den Speisewassermassenstrom (Ṁ) ein Enthalpie-Korrekturwert berücksichtigt wird, der die Abweichung des Iststandes der Enthalpie am Austritt der Verdampferheizfläche (4) von einem zugeordneten Sollwert charakterisiert.Method according to one of Claims 1 to 8, in which an enthalpy correction value is taken into account for the setpoint value ( Ṁ s ) for the feedwater mass flow ( Ṁ ), which characterizes the deviation of the actual state of enthalpy at the outlet of the evaporator heating surface (4) from an assigned setpoint value , Zwangdurchlaufdampferzeuger (1, 1') mit einer Verdampferheizfläche (4) und mit einer Vorrichtung zum Einstellen des Speisewassermassenstroms (Ṁ), die anhand eines Sollwerts (Ṁ s) für den Speisewassermassenstrom (Ṁ) geführt ist, wobei eine zugeordnete Speisewasserdurchflussregelung (32, 32') zur Vorgabe des Sollwerts (Ṁ s) anhand des Verfahrens nach einem der Ansprüche 1 bis 9 ausgelegt ist.Forced - circulation steam generator (1, 1 ') having an evaporator heating surface (4) and a device for adjusting the feedwater mass flow ( Ṁ ), which is guided by a desired value ( Ṁ s ) for the feedwater mass flow ( Ṁ ), an associated feedwater flow control (32, 32 ') for setting the desired value ( Ṁ s ) is designed by the method according to one of claims 1 to 9. Zwangdurchlaufdampferzeuger (1, 1') nach Anspruch 10, der heizgasseitig mit dem Abgas aus einer zugeordneten Gasturbinenanlage beaufschlagt ist.Forced-circulation steam generator (1, 1 ') according to claim 10, which is acted upon by the hot gas side with the exhaust gas from an associated gas turbine plant.
EP07023081A 2007-11-28 2007-11-28 Method for operating a continuous flow steam generator and once-through steam generator Withdrawn EP2065641A3 (en)

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EP07023081A EP2065641A3 (en) 2007-11-28 2007-11-28 Method for operating a continuous flow steam generator and once-through steam generator
CN200880116657.7A CN102216685B (en) 2007-11-28 2008-11-14 Method for operating a once-through steam generator and forced-flow steam generator
US12/743,881 US9482427B2 (en) 2007-11-28 2008-11-14 Method for operating a once-through steam generator and forced-flow steam generator
PT88536644T PT2212618E (en) 2007-11-28 2008-11-14 Method for operating a continuous flow steam generator and once-through steam generator
PCT/EP2008/065522 WO2009068446A2 (en) 2007-11-28 2008-11-14 Method for operating a once-through steam generator and forced-flow steam generator
CA2706794A CA2706794C (en) 2007-11-28 2008-11-14 Method for operating a once-through steam generator and forced-flow steam generator
ES08853664T ES2402842T3 (en) 2007-11-28 2008-11-14 Procedure for the operation of a steam generator as well as a steam generator
MYPI2010002487A MY154744A (en) 2007-11-28 2008-11-14 Method for operating a once-through steam generator and forced-flow steam generator
JP2010535331A JP5318880B2 (en) 2007-11-28 2008-11-14 Method for operation of once-through boiler and forced once-through boiler
RU2010126182/06A RU2010126182A (en) 2007-11-28 2008-11-14 METHOD FOR OPERATION OF A DIRECT-LINE VAPOR GENERATOR AND A DIRECT CIRCULATION STEAM GENERATOR
EP08853664A EP2212618B1 (en) 2007-11-28 2008-11-14 Method for operating a continuous flow steam generator and once-through steam generator
PL08853664T PL2212618T3 (en) 2007-11-28 2008-11-14 Method for operating a continuous flow steam generator and once-through steam generator
AU2008328934A AU2008328934B2 (en) 2007-11-28 2008-11-14 Method for operating a once-through steam generator and forced-flow-once-through steam generator
BRPI0819844-6A BRPI0819844A2 (en) 2007-11-28 2008-11-14 Method of operation of a single pass steam generator and forced flow steam generator
TW097145590A TWI465674B (en) 2007-11-28 2008-11-26 Method for operation a once-through steam generator and forced-flow steam generator
ARP080105181A AR069453A1 (en) 2007-11-28 2008-11-28 PROCEDURE FOR THE OPERATION OF A CONTINUOUS CIRCULATION STEAM GENERATOR, AS WELL AS FORCED CONTINUOUS CIRCULATION STEAM GENERATOR
ZA201001475A ZA201001475B (en) 2007-11-28 2010-03-01 Method for operating a once-through steam generator and forced-flow steam generator

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