WO2011077427A1 - Condenser ventilation control - Google Patents

Condenser ventilation control Download PDF

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Publication number
WO2011077427A1
WO2011077427A1 PCT/IL2010/001048 IL2010001048W WO2011077427A1 WO 2011077427 A1 WO2011077427 A1 WO 2011077427A1 IL 2010001048 W IL2010001048 W IL 2010001048W WO 2011077427 A1 WO2011077427 A1 WO 2011077427A1
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WO
WIPO (PCT)
Prior art keywords
fan
operation state
fans
fan operation
ambient temperature
Prior art date
Application number
PCT/IL2010/001048
Other languages
French (fr)
Inventor
Ofer Kogel
Eli Yogev
Original Assignee
Dor Chemicals Ltd.
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 Dor Chemicals Ltd. filed Critical Dor Chemicals Ltd.
Priority to EP10838823.2A priority Critical patent/EP2516818A4/en
Publication of WO2011077427A1 publication Critical patent/WO2011077427A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K23/00—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids
    • F01K23/02—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled
    • F01K23/06—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle
    • F01K23/10—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle with exhaust fluid of one cycle heating the fluid in another cycle
    • F01K23/101—Regulating means specially adapted therefor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K13/00—General layout or general methods of operation of complete plants
    • F01K13/02—Controlling, e.g. stopping or starting
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K9/00—Plants characterised by condensers arranged or modified to co-operate with the engines
    • F01K9/003—Plants characterised by condensers arranged or modified to co-operate with the engines condenser cooling circuits
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B1/00—Methods of steam generation characterised by form of heating method
    • F22B1/02—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers
    • F22B1/18—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines
    • F22B1/1807—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines using the exhaust gases of combustion engines
    • F22B1/1815—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines using the exhaust gases of combustion engines using the exhaust gases of gas-turbines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28B—STEAM OR VAPOUR CONDENSERS
    • F28B1/00—Condensers in which the steam or vapour is separate from the cooling medium by walls, e.g. surface condenser
    • F28B1/06—Condensers in which the steam or vapour is separate from the cooling medium by walls, e.g. surface condenser using air or other gas as the cooling medium
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28B—STEAM OR VAPOUR CONDENSERS
    • F28B11/00—Controlling arrangements with features specially adapted for condensers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F2250/00—Arrangements for modifying the flow of the heat exchange media, e.g. flow guiding means; Particular flow patterns
    • F28F2250/08—Fluid driving means, e.g. pumps, fans
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/14—Combined heat and power generation [CHP]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/16—Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]

Definitions

  • the present invention relates to condensers. More particularly, the present invention relates to a method of controlling ventilation of a condenser.
  • Steam turbines are commonly used to power electrical generators for the generation of electric power.
  • One or more steam turbines may be employed in conjunction with one or more gas turbines as part of a combined cycle power plant.
  • heated gas is formed as a result of a combustion process, for example, of natural gas or fuel oil. Expansion of the heated gas is utilized to rotate one or more (typically two) gas turbines. Rotation of the gas turbine may be used to power an electrical generator.
  • the heated gas that exits the gas turbine as exhaust is still hot enough to heat water to form steam.
  • the exhaust gas from the gas turbine may be conducted to a heat exchanger. In the heat water, the exhaust gas heats water to form pressurized steam.
  • the pressurized steam may be conducted to a steam turbine so as to rotate the steam turbine. Rotation of the steam turbine also powers an electrical generator.
  • the combined cycle utilizes the combustion products to generate additional electric power, making efficient use of the combustion.
  • the condenser may be air cooled.
  • the condenser may include one or more steam ducts or pipes that contain the exhaust steam. Exhaust steam from steam duct may be directed through a set of one or more cooling panels.
  • the cooling panels typically are include an array of parallel or coiled narrow pipes between which air may flow. Thus, the cooling panels provide a large contact area between the air and the pipes, enabling efficient thermal contact with the flowing air.
  • the air typically enters the condenser at the ambient air or atmospheric temperature. The air flows through the panels, either passively due to natural convection, or is blown through the panels (forced convection). The flow of the air may be controlled by one or more ventilation fans.
  • the fans may be turned on or off, or their speeds varied, by an automatic control system.
  • Water condensate resulting from the condensation of the steam is collected in a tank or reservoir (typically located below the cooling panels).
  • the collected condensate may then be returned to the heat exchanger to be reheated by exhaust gas from gas turbine, again forming pressurized steam for powering the steam turbine.
  • the efficiency of power generation by the steam turbine may depend on the temperature of the condensate formed by condensation of the exhaust steam.
  • thermodynamic efficiency of the turbine may be maximized by maximizing the difference in temperature between the hot pressurized steam created by the heat exchanger, and the condensate within the constraints of the turbine design.
  • the temperature of the pressurized steam should thus be as large as possible, while the temperature of the condensate is as low as possible.
  • the hot pressurized steam is generated by heating the condensate. Therefore, more energy is required to heat a colder condensate than a warmer condensate.
  • the temperature of the condensate in an air cooled condenser is typically controlled by adjusting operation of the cooling fans. For example, one or more order to achieve an optimum condensate temperature, cooling fans may be turned on or off in accordance with conditions in order to maintain an optimum air flow and condensate temperature. Alternatively, the fan blade rotation velocities of one or more of the cooling fans may be adjusted in order to adjust the air flow. Temperature of the condensate may also be affected by wind conditions.
  • a condenser may be provided with panels or other structure designed to block, divert, or slow the flow of wind through the condenser, thus reducing or eliminating the effect of wind on the condensate temperature.
  • Temperature of the condensate may also be affected by factors that reduce of affect the flow of cooling air or the steam through the condenser.
  • factors affecting the flow of air through the condenser may include such factors as trapping or external buildup of dust, bird feces, or mud.
  • Operation of the fans is generally adjusted in accordance with a set of instructions.
  • a controller operating in accordance with programmed instructions may turn a fan on or off, or adjust its rotation velocity.
  • the programmed instructions generally include controlling operation of the fans in accordance with one or more sensed conditions.
  • a heat loading (the required rate of heat removal) may be determined in a relatively straightforward manner on the basis of a few parameters.
  • an optimization may be based on heat loading, on conditions of the ambient atmosphere (assuming that the heat loading is known), or on both.
  • Optimized air flow in a condenser of a steam turbine may not be easily determinable.
  • optimized air inflow to a gas turbine (for example, as addressed by Kopko in US 6,880,343) depends on factors that are different than those of concern in optimizing the air flow through a condenser of a steam turbine.
  • Such result conditions may include, for example, the temperature of the condensate, steam pressure in the condenser, or the temperature of air as it exits the condenser.
  • closed loop control cycles may lead to inefficient oscillatory behavior when applied to a condenser of a steam turbine in a combined cycle power plant.
  • changes in result conditions may be not be detectable until long after changes in fan operation are made.
  • changing the number of fans in operation may not result in detectable changes in the result conditions until long (perhaps on the order of half an hour) after the change.
  • Such time delays sometimes referred to as hysteresis, may result in an oscillatory cycle of overcompensation, first in one direction then in the other. This may lead to slow convergence to stable operation.
  • a method for controlling operation of one or more ventilation fans of an air- cooled condenser for condensing exhaust steam from a steam turbine of an electric power plant, the steam turbine powering an electric power generator includes: acquiring an ambient temperature, measuring a parameter indicative of the power output of the generator, determining a fan operation state based on the acquired ambient temperature and the measured parameter, and operating the fan in accordance t with the determined fan operation state.
  • the fans include an array of fans.
  • the fan operation state is selected from the group of states consisting of: number of fans of the array that are turned on or off, rotation velocity of the fans and blade pitch of the fans.
  • the step of determining a fan operation state includes selecting a value from a lookup table of fan operation states in accordance with the acquired ambient temperature and the measured parameter.
  • the step of determining a fan operation state includes application of an algorithm generated by an algorithm generation method.
  • the algorithm generation method includes: operating the power plant under an operating condition of substantially constant ambient temperature and a substantially constant value of a parameter indicative of the power output of the generator; operating a ventilation fan in accordance with a selected fan operation state; measuring an efficiency of the power plant; and repeating the previous steps while varying the selected fan operation state until a maximum efficiency is measured.
  • the step of determining a fan operation state includes application of an algorithm generated by an algorithm generation method.
  • the algorithm generation method includes: simulating operation of the power plant under an operating condition of substantially constant ambient temperature and electric power output; simulating operation of a ventilation fan in accordance with a selected fan operation state; calculating a simulated efficiency of the power plant; and repeating the previous steps while varying the selected fan operation state until a maximum simulated efficiency is calculated.
  • the algorithm is a computer executable algorithm.
  • a control system for controlling operation of one or more ventilation fans of an air-cooled condenser for condensing exhaust steam from a steam turbine of an electric power plant, the steam turbine powering an electric power generator.
  • the system includes a controller for receiving an ambient temperature and a parameter indicative of the power output of the generator, for determining a fan operation state based on the received ambient temperature and parameter, and for operating the fan in accordance with the determined fan operation state.
  • Fig. 1 is a block diagram of a combined cycle electrical power plant in accordance with embodiments of the present invention.
  • FIG. 2 A illustrates an air cooled condenser such as may be used in a system operated in accordance with embodiment of the present invention.
  • Fig. 2B shows the interior of the air cooled condenser shown in Fig. 2B.
  • Fig. 3 is a flow chart of a method for condenser ventilation fan control in accordance with embodiments of the present invention.
  • Fig. 4 shows a condenser ventilation fan control lookup table in accordance with some embodiments of the present invention.
  • FIG. 5 is a flowchart of a method for generation a control algorithm in accordance with embodiments of the present invention.
  • Embodiments of the invention may include an article such as a computer or processor readable medium, or a computer or processor storage medium, such as for example a memory, a disk drive, or a USB flash memory, encoding, including or storing instructions, e.g., computer-executable instructions, which when executed by a processor or controller, carry out methods of the disclosed embodiments.
  • a computer or processor readable medium such as for example a memory, a disk drive, or a USB flash memory
  • encoding including or storing instructions, e.g., computer-executable instructions, which when executed by a processor or controller, carry out methods of the disclosed embodiments.
  • Control of a ventilation fan for cooling a condenser for condensing exhaust steam from a steam turbine is based on two measured quantities: the ambient air temperature and a parameter indicative the electrical power output of a generator powered by the steam turbine.
  • the parameter may be a direct measurement of the output power of the generator, or may be related to the power input to a power plant of which the steam turbine is part (e.g. a fuel combustion rate).
  • the parameter is typically indicative of the force or torque required to maintain rotation of the turbine.
  • a condenser cooling fan for a steam turbine is typically designed to cause air to flow through one or more cooling panels of a steam turbine condenser.
  • the steam turbine and its condenser may typically be part of a combined cycle power plant.
  • a hot compressed gas is generated by combustion, for example, of natural gas or fuel oil.
  • the hot compressed gas is allowed to expand through, and drive, a gas turbine.
  • the hot exhaust gas from the gas turbine is conducted into a heat exchanger. In the heat exchanger, the exhaust gas heats water, or another suitable fluid, to form pressurized steam, or vapor.
  • steam (used hereinafter to refer to either water vapor or vapor of another liquid) may be generated directly using a power source to heat water (used hereinafter to refer to any suitable liquid) in a boiler or heat exchanger.
  • power sources may include, for example, combustion of coal, fuel oil, or natural gas, or may include heat generation by an alternative source such as, for example, a nuclear reactor, solar heating, or geothermal heating.
  • the pressurized steam may then be conducted to an intake of a steam turbine.
  • the hot pressurized steam passes through the steam turbine, rotating and powering it, - and exits as exhaust steam. Rotation of the steam turbine is typically utilized to power, an electric power generator.
  • the exhaust steam that exits from the steam turbine may be conducted to a condenser, where the exhaust steam is cooled and condensed to a condensate.
  • the condenser reduces the pressure of the exhaust steam to less than the pressure at the steam turbine intake.
  • Increasing the difference in steam pressure between the turbine intake and exhaust may increase the force or torque of the pressurized intake steam on the steam turbine. When the pressure increase is attained by reducing the exhaust pressure, the increased pressure difference may result in increased efficiency (ratio of energy output to energy input) of the turbine operation.
  • the liquid condensate that is formed by condensation of the exhaust steam in the condenser is collected in a condensate collection container.
  • condensate collection utilizes gravity to collect the condensate in a condensate collection container located near the bottom of the condenser. The collected condensate may then be conducted back to the heat exchanger to be reheated to form pressurized steam to again power the steam turbine.
  • a typical air-cooled condenser steam in the condenser is directed through a cooling panel that includes an array or bundle of narrow pipes.
  • the narrow pipes of the condenser bundle are spaced such that air may flow between the pipes. Air passing between the pipes of the bundle may thus cool the fluid, both steam and condensate, within the pipes. Any steam flowing through the panels is cooled to condensate to be collected in a condensate collection container.
  • the rate of cooling of the panels is typically dependent, among other factors, on the velocity of the air flowing between the pipes. Thus, actively moving the air by means of a fan may increase the cooling rate of the fluid in the pipes.
  • a condenser typically includes an array of several fans, each fan blowing air through a different section of the cooling panel. Therefore, controlling a fan that blows air through one section of the cooling panel may determine the temperature of a condensate collected from that section.
  • Condensate formed in several sections of the cooling panel is typically collected ⁇ in a single condensate collection container.
  • Separately controlling operation of two or more ventilation fans of a condenser may assist in controlling the temperature of the , condensate collected in the condensate collection container.
  • a typical condenser may include two elongated rectangular panels arranged in the form of an elongated sloped roof, having a cross section in the form of an inverted V shape. Steam is fed into the cooling panels from above via a horizontal steam duct that is located at the apex of the inverted V shape and is open to the cooling panels. Cooling fans may be arranged along the length of the panel structure at the base of the inverted V shape.
  • the cooling fans are typically spaced at regular intervals along the length of the panel structure.
  • the fans typically are arranged with their fan blade rotation axes oriented vertically.
  • the fan blows cooling air upward between the cooling panels such that the blown air flows upward and outward through the panels. Condensate within the panels may then flow downward into a condensate collection container.
  • the temperature of the condensate collected in the condensate collection container may depend partially on the cooling rate of the fluid in the cooling panels.
  • the cooling rate of the fluid in the cooling panels may depend partially on the flow rate of air through the cooling panels.
  • the flow rate of the air may be controlled by controlling the number of fans in operation or the rotation velocities of the fans.
  • the number of fans that are turned on or off may be varied by a controller in accordance with predetermined requirements, such as one or more measured quantities.
  • control of a condenser fan in accordance with embodiments of the present invention depends on two quantities.
  • One measured quantity is a parameter that indicates the electrical power output of a generator that is powered by a steam turbine whose exhaust steam is to be condensed by the condenser.
  • Electrical power meters that are capable of producing a digital or analog electrical output signal that indicates the measured electrical power are well known in the art.
  • the electrical power output of a generator is generally routinely monitored for existing electrical power generators.
  • measurement of the generator output power parameter may be compatible with existing power plants.
  • the generator output power parameter may include a measured value that is related directly or indirectly to generator output.
  • the measured parameter may include a measured rate of fuel consumption or steam production, a boiler steam temperature or pressure, or any other parameter that may indicate generator output.
  • the second measured quantity is the ambient air temperature in the vicinity of the condenser.
  • one or more thermometers may be positioned near the air intake of one or more condenser fans.
  • Thermometers that are capable of producing a digital or analog electrical output signal that indicates the measured temperature are well known in the art.
  • Output signals indicating the values of the measured generator output power parameter and the ambient temperature may be input to a controller.
  • Each output signal may be transmitted from the appropriate meter to the controller via a suitable communications cable, or may be transmitted wirelessly.
  • The. controller may include one or more automatically operating processors, such as one or more programmable computers or microprocessors.
  • a processor may be programmed to read the input measurement signals and to output one or more instructions that control the number of fans to operate, or the fan speeds.
  • a controller may also be understood to include one or more human operators operating in accordance with predetermined instructions based on the measured parameter and ambient temperature.
  • a controller may include a processor operating in accordance with a control algorithm.
  • the control algorithm may determine the number of ventilation fans to operate with a given measured generator electrical power output and a given measured ambient temperature.
  • the algorithm may include one or more theoretically, empirically, or semi-empirically derived formulas, or one or more indexed lookup tables.
  • the algorithm may output a control signal that indicates such factors as: how many ventilation fans to operate, which fans of an array of ventilation fans to operate, a blade pitch (attack angle) for each fan, or a blade rotational velocity for each fan.
  • the algorithm may output a single value that indicates a relative fan cooling rate.
  • the fan cooling rate value may indicate a family of fan control states that may be implemented to yield similar fan cooling rate values.
  • a fan cooling rate value indicating 50% of maximum cooling capacity may be implemented by turning off half the fans or by running all fans., at approximately half their capacity.
  • the control signals may typically be transmitted, via communications cable or wirelessly, directly to one or more devices that control operation of the condenser fans.
  • the processor may transmit or display instructions to a human operator who may then act in accordance with the instructions to control operation of the fans.
  • An algorithm for determining operation of the fans may be generated by one or more methods. For example, parameters describing characteristics and operation of a turbine and condenser system may be input to an appropriate system simulator or simulation computer program, such as, for example, Thermoflex. Such simulation systems and programs are known in the art. For example, a series of such simulations may be run with the generator output and ambient temperature as variable input parameters. Each simulation may yield as its output an optimal mode of operation of the ventilator fans. The mode of operation may include defining which fans should be on and which should be off and, optionally, the speeds of the fans. The results may be output in the form of parameters of one or more empirical or semi-empirical formulas, or in the form of a lookup table.
  • the optimum fan operation as a function of generator power output and ambient temperature may be determined empirically during operation of the steam turbine. For example, performance may be monitored during routine operation so as to generate a lookup table. Alternatively, the system may be operated specifically for the purpose of generating the lookup table, with operation parameters being varied in a systematic fashion.
  • an algorithm may include one or more theoretically or empirically derived parameterized formulas. The parameters of the parameterized formulas may be determined experimentally during operation of the system.
  • Another option is to determine an algorithm by operating the system under a limited set of operating conditions. A simulation may then be used to extrapolate the algorithm to other operating conditions.
  • Fig. 1 is a block diagram of a combined cycle electrical power plant in accordance with embodiments of the present invention.
  • Energy for powering combined cycle power plant 10 is provided by combustion source 12.
  • Combustion source 12 provides hot gas 14 to gas turbine 16.
  • Gas turbine 16 emits exhaust gas 18.
  • Exhaust gas 18 heats supply water 48 in heat exchanger 20 to form pressurized steam 22.
  • Pressurized steam 22 is directed into, and drives, steam turbine 24.
  • Steam turbine 24 is coupled to generator 26.
  • Generator 26 provides electric power to a consumer of electric power, such as, for example, power grid 28, or to a factory or similar facility. Electric power output of generator 26 may be measured by electric power meter 27.
  • Exhaust steam 56 from steam turbine 24 is conducted into condenser 30.
  • Components of condenser 30 that are shown schematically in Fig. 1 are also shown in Fig. 2A and Fig. 2B.
  • Fig. 2A illustrates an air cooled condenser such as may be used in a system operated in accordance with embodiment of the present invention.
  • Fig. 2B shows the interior of the air cooled condenser shown in Fig. 2B.
  • Exhaust steam 56 is conducted into steam duct 46 of condenser 30.
  • Steam from steam duct 46 is conducted into pipes 51 of cooling panels 50.
  • One or more ventilation fans 42 such as ventilation fans 42a-42d, draw outside air 40 into central space 55 of condenser 30. Air in central space 55 is then forced outward as out-flowing air 44 through spaces 53 of cooling panels 50.
  • Thermometer 39 may measure the temperature of outside air 40.
  • Condensate 52 may be conducted, typically under the force of gravity, to condensate collection container 36 where it is collected as collected condensate 54. Collected condensate 54 may be then conducted from condensate collection container 36 as supply water 48 to heat exchanger 20 for conversion to pressurized steam 22.
  • Controller 34 may include one or more automated devices, such as an analog computer or a programmed digital processor or computer, or may, alternatively or in addition, include one or more human operators operating controls in accordance with of instructions. Controller 34 receives ambient temperature data 33 from thermometer 39 through a wired or wireless communications channel. Similarly, controller 34 receives generator . power output data 32 from electrical power meter 27. Controller 34 applies an algorithm . ; based on the received values of the ambient temperature and the generator power and generates fan operation instructions 41 for operating a motor 43 of a ventilation fan 42. For example, fan operation instructions 41 may include instructions to turn on or off one or more of ventilation fans 42, for example, one or more of fans ventilation 42a-42d. As another example, operation instructions 41 may include instructions to change the blade rotation velocity of one or more of ventilation fans 42, for example, one or more of ventilation fans 42a-42d.
  • Fig. 3 is a flow chart of a method for condenser ventilation fan control in accordance with embodiments of the present invention. It should be understood that in the flow chart, the division of the method into individual steps is illustrative only, and that alternative divisions into steps may yield identical results. Such alternative division into steps should be understood as being included within the scope of the present invention. Also, the order of the steps shown is illustrative only, and some steps of the method may be performed in a different order or concurrently without affecting the results. Such alternative orders of steps should also be understood as being included within the scope of the present invention. [0052] A condenser ventilation fan controller operating in accordance with the method acquires a value of the ambient air temperature (step 60).
  • the controller may query a thermometer that is located so as to measure the temperature of the ambient air.
  • the acquired ambient temperature value may optionally be adjusted to account for one or more additional environmental or meteorological factors that may affect condenser air cooling. Such factors may include, for example, wind direction and velocity and relative humidity.
  • the controller acquires the value of a parameter indicative of the electric power output of a generator being run by the steam turbine whose exhaust is condensed by the condenser (step 62).
  • the controller may query an electric power meter connected to out connection points of the generator. The controller compares the acquired values with values stored from a previous acquisition, if any (step 64). If the acquired values are substantially similar to the stored values, where substantially similar may be defined for each value in ,* ⁇ .
  • the acquired values are stored in place of the . previously stored values.
  • the previous steps, starting from step 60, are then repeated after a pre-defined interval. For example, values may be acquired at a typical time interval of once every ten minutes. A change in electric power output or load may also trigger repetition of the steps.
  • the acquired values are different, in accordance with predefined criteria, from the stored values, the acquired values are stored in place of the previously stored values (step 66).
  • a control algorithm then is applied using the acquired ambient temperature and generator output power values as input parameters (step 68) to generate ventilation fan control instructions.
  • the algorithm may include finding a value in a lookup table that is indexed by ambient temperature and generator output power parameter.
  • the indexed value in the lookup table may indicate, for example, how many ventilation fans to turn on and how many to turn off, which ventilation fans of a ventilation fan array to operate, or the operation speed of each ventilation fan.
  • the algorithm may include applying a formula or a set of instructions to determine the ventilation fan control instructions.
  • An algorithm may also be dependent on additional parameters that affect the cooling rate.
  • the algorithm may be dependent on wind velocity.
  • the validity of a given lookup table may be limited to a given range of wind conditions.
  • Fig. 4 shows a condenser ventilation fan control lookup table in accordance with some embodiments of the present invention.
  • the lookup table may be typical for a particular power plant configuration.
  • Each row of the lookup table represents a range of ambient temperatures (here given in units of degrees Celsius).
  • Each column of the table represents a generator output parameter (expressed as a percent of maximum capacity). For example, if the ambient temperature is 12°C and the generator is operating at 50% capacity, the table indicates that the required cooling rate is 75% to 80% of maximum cooling capacity. In order to achieve 75% to 80% cooling capacity, 20% to 25% of the ventilation fans may be turned off. Alternatively, all fans may be operated at 75% to 80% of their maximum capacities (for example, by reducing their rotation velocities).
  • the controller may be connected to motors of the ventilation fans such that the controller may directly control electric power to the fan motors.
  • the controller may transmit a control signal to a motor control device associated with the fan motor such that the motor control device may control the fan motor in accordance with the transmitted signal.
  • a motor control device may optionally communicate the current status of the ventilation fans to the controller.
  • the fan status data may be input as an input parameter to the control algorithm.
  • Fig. 5 is a flowchart of a method for generation a control algorithm in accordance with embodiments of the present invention. It should be understood that in the flow chart, the division of the method into individual steps is illustrative only, and that alternative divisions into steps may yield identical results. Such alternative division into steps should be understood as being included within the scope of the present invention. Also, the order of the steps shown is illustrative only, and some steps of the method may be performed in a different order or concurrently without affecting the results. Such alternative orders of steps should also be understood as being included within the scope of the present invention.
  • the control algorithm may be generated by actual or simulated operation of the steam turbine and condenser. All steps of the method referring to operation of the turbine and generator, of the condenser ventilation fans, or of operation at a given ambient temperature, should be understood as equally applying to actual operation, simulated operation, or to a combination of actual and simulated operation. For example, simulated operation may be followed by actual operation to verify the generated algorithm, or to make adjustments to the generated algorithm. Alternatively, actual operation under a limited set of operating conditions may be supplemented by simulated operation. Simulated operation may be utilized to extrapolate a generated - algorithm to include operating conditions that were not achieved during actual - operation. For example, various environmental or economic constraints may have, precluded actual operation at all desired operating conditions.
  • Operating conditions for the steam turbine and condenser are determined or measured, either as parameters of simulated operation or as operating conditions for actual operation. These operating conditions include determining the ambient temperature (step 72) and the output electric power of a generator that is run by the steam turbine (step 74). An initial value for best efficiency attained thus far is stored (step 76). For example, a typical initial value may be zero.
  • An initial fan operation state is selected (step 78). A fan operation state may include determining which fans are turned on and which are turned off, and the operation speeds of the fans. The power generation system that includes the steam turbine and condenser is then operated (either actually or in simulation) under these conditions.
  • the efficiency of the system with the current fan operation state is determined (step 80). For example, a measure of the efficiency may include a value proportional to the generated electrical power output divided by the rate of fuel consumption while generating the electrical energy.
  • the current system efficiency with the current fan operation state is compared to the stored best value (step 82). If the current system efficiency is greater than the stored value, the current fan operation state is stored, replacing the previously stored state, if any (step 84). Similarly, the stored best efficiency value is replaced with the current system efficiency. If the current system efficiency is not greater than the previously stored value, the method proceeds to step 88.
  • the next step of the method is to check whether all fans operation states that are to be tested have been tested already with the current operating conditions (step 88). If not, a new fan state to be tested is selected in accordance with predetermined criteria (step 89). The new state is then tested (returning to step 80).
  • the stored fan operation state is incorporated into the algorithm as the optimum fan operation state for the operating conditions (step 90).
  • a fan operation state defined by the number of ventilation fans in operation may be incorporated into a lookup table indexed by the ambient temperature and generator output power of the current operating conditions.
  • the fan operation state may be used to determine parameters of a function or other set of instructions for determining the optimum fan operation state given a set of operating conditions.
  • Another set of operating conditions for example, characterized by a new ambient temperature value or generator output power value (step 92) may then be determined.
  • the optimum fan operation state for the new operating conditions may then be found (returning to step 76).

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Abstract

A method controls operation of one or more ventilation fans of an air-cooled condenser for condensing exhaust steam from a steam turbine of an electric power plant. The steam turbine powers an electric power generator. The method includes the following steps: An ambient temperature is acquired and a parameter indicative of the power output of the generator is measured. A fan operation state is determined based on the acquired ambient temperature and the measured parameter. The fan is operated in accordance with the determined fan operation state.

Description

CONDENSER VENTILATION CONTROL
FIELD OF THE INVENTION
[0001] The present invention relates to condensers. More particularly, the present invention relates to a method of controlling ventilation of a condenser.
BACKGROUND OF THE INVENTION
[0002] Steam turbines are commonly used to power electrical generators for the generation of electric power. One or more steam turbines may be employed in conjunction with one or more gas turbines as part of a combined cycle power plant. In a combined cycle power plant, heated gas is formed as a result of a combustion process, for example, of natural gas or fuel oil. Expansion of the heated gas is utilized to rotate one or more (typically two) gas turbines. Rotation of the gas turbine may be used to power an electrical generator. The heated gas that exits the gas turbine as exhaust is still hot enough to heat water to form steam. Thus, in a combined cycle power plant, the exhaust gas from the gas turbine may be conducted to a heat exchanger. In the heat water, the exhaust gas heats water to form pressurized steam. The pressurized steam may be conducted to a steam turbine so as to rotate the steam turbine. Rotation of the steam turbine also powers an electrical generator. In this manner, the combined cycle utilizes the combustion products to generate additional electric power, making efficient use of the combustion.
[0003] In a steam turbine, heated steam is directed into the steam turbine at a high pressure, causing the steam turbine to rotate. After powering the steam turbine, the steam exits from the steam turbine at a lower exhaust pressure and temperature. The low exhaust pressure is typically maintained by a condenser in which the exhaust steam is actively cooled so as to cause the exhaust steam to condense to a liquid condensate. The force applied to the steam turbine increases with the difference in pressure between the high pressure of the heated steam and the exhaust pressure. The required force, typically depends on the electric power load on the generator (typically related to the demand of an electrical power grid). [0004] When the power plant is located near a body of water, the water may be used to actively or passively cool the condenser. When no such body of water is available, or when environmental constraints preclude using water, the condenser may be air cooled. For example, the condenser may include one or more steam ducts or pipes that contain the exhaust steam. Exhaust steam from steam duct may be directed through a set of one or more cooling panels. The cooling panels typically are include an array of parallel or coiled narrow pipes between which air may flow. Thus, the cooling panels provide a large contact area between the air and the pipes, enabling efficient thermal contact with the flowing air. The air typically enters the condenser at the ambient air or atmospheric temperature. The air flows through the panels, either passively due to natural convection, or is blown through the panels (forced convection). The flow of the air may be controlled by one or more ventilation fans. The fans may be turned on or off, or their speeds varied, by an automatic control system. Water condensate resulting from the condensation of the steam is collected in a tank or reservoir (typically located below the cooling panels). The collected condensate may then be returned to the heat exchanger to be reheated by exhaust gas from gas turbine, again forming pressurized steam for powering the steam turbine.
[0005] The efficiency of power generation by the steam turbine may depend on the temperature of the condensate formed by condensation of the exhaust steam. For example, thermodynamic efficiency of the turbine may be maximized by maximizing the difference in temperature between the hot pressurized steam created by the heat exchanger, and the condensate within the constraints of the turbine design. Thus, in order to maintain a large thermodynamic efficiency, the temperature of the pressurized steam should thus be as large as possible, while the temperature of the condensate is as low as possible. On the other hand, the hot pressurized steam is generated by heating the condensate. Therefore, more energy is required to heat a colder condensate than a warmer condensate. Thus, if the temperature of the condensate is too low, too much energy may be expended in heating the condensate to form steam. These two considerations must be balanced in order to achieve an optimum condensate temperature. [0006] The temperature of the condensate in an air cooled condenser is typically controlled by adjusting operation of the cooling fans. For example, one or more order to achieve an optimum condensate temperature, cooling fans may be turned on or off in accordance with conditions in order to maintain an optimum air flow and condensate temperature. Alternatively, the fan blade rotation velocities of one or more of the cooling fans may be adjusted in order to adjust the air flow. Temperature of the condensate may also be affected by wind conditions. (However, a condenser may be provided with panels or other structure designed to block, divert, or slow the flow of wind through the condenser, thus reducing or eliminating the effect of wind on the condensate temperature.) Temperature of the condensate may also be affected by factors that reduce of affect the flow of cooling air or the steam through the condenser. For example, factors affecting the flow of air through the condenser may include such factors as trapping or external buildup of dust, bird feces, or mud.
[0007] Operation of the fans is generally adjusted in accordance with a set of instructions. For example, a controller operating in accordance with programmed instructions may turn a fan on or off, or adjust its rotation velocity. The programmed instructions generally include controlling operation of the fans in accordance with one or more sensed conditions.
[0008] Methods for controlling air flow or other factors for optimizing a cooling process have been described previously. For example, techniques have been described (for example, by Hartman in US 6,257,007, Hislop in WO 98/06987, Braun et al. in US 5,040,377, Grove et al. in US 2005/086943, Henry in US 6,718,779, Caskey et al. in US 2006/174640, Nishida et al. in JP 3122461, Maheshwari et al. in US 6,446,941 , and Gustafson et al. in US 2001/054293) for the simpler case of optimizing air conditioning or refrigeration systems. In the case of air conditioning or refrigeration, a heat loading (the required rate of heat removal) may be determined in a relatively straightforward manner on the basis of a few parameters. Thus, an optimization may be based on heat loading, on conditions of the ambient atmosphere (assuming that the heat loading is known), or on both. Optimized air flow in a condenser of a steam turbine, however, may not be easily determinable. Similarly, optimized air inflow to a gas turbine (for example, as addressed by Kopko in US 6,880,343) depends on factors that are different than those of concern in optimizing the air flow through a condenser of a steam turbine.
[0009] Methods of controlling the air flow through condensers have been described. For example, GB 904959 (Happel Gesellschaft mit Beschrankter Haftung) describes a method where air flow is adjusted on the basis of the outdoor ambient temperature. The main objective of the described method is to avoid excessively cooling, and possibly freezing, the condensed fluid. However, such a method would not be suitable for optimizing air flow to optimize the efficiency of a steam turbine. For example, the described method does not address variations in operating conditions of the power plant.
[0010] Methods have been described for optimizing the operation of air cooling of a steam condenser, for example, by Mayer (US 4,085,594), Niemann (US 3,289,742), Takahama (US 2004/172947), Kudo (JP 11337272), Furuye et al. (JP1 1132675), Schwedler et al. (US 5,600,960), Jakobsson et al. (US 4,450,899), and by Yakota et al. (JP 57031788). In the described methods, one or more conditions resulting from the operation of ventilation fans is measured. The measured condition is utilized in a closed loop feedback control cycle to adjust fan operation. Such result conditions may include, for example, the temperature of the condensate, steam pressure in the condenser, or the temperature of air as it exits the condenser. Such closed loop control cycles may lead to inefficient oscillatory behavior when applied to a condenser of a steam turbine in a combined cycle power plant. For example, changes in result conditions may be not be detectable until long after changes in fan operation are made. For example, changing the number of fans in operation may not result in detectable changes in the result conditions until long (perhaps on the order of half an hour) after the change. Such time delays, sometimes referred to as hysteresis, may result in an oscillatory cycle of overcompensation, first in one direction then in the other. This may lead to slow convergence to stable operation.
[0011] Thus, there is a need for a method of controlling operation of cooling fans in a condenser of a steam turbine that can rapidly respond to changing conditions.
[0012] It is an object of the present invention to provide a method of controlling a fan of a condenser of a steam turbine that does not employ closed loop feedback, that may respond effectively to changes in operating conditions, and that may be easily applied to the operation of an existing power plant.
[0013] Other aims and advantages of the present invention will become apparent after reading the present invention and reviewing the accompanying drawings.
SUMMARY OF THE INVENTION
[0014] There is thus provided, in accordance with some embodiments of the present invention, a method for controlling operation of one or more ventilation fans of an air- cooled condenser for condensing exhaust steam from a steam turbine of an electric power plant, the steam turbine powering an electric power generator. The method includes: acquiring an ambient temperature, measuring a parameter indicative of the power output of the generator, determining a fan operation state based on the acquired ambient temperature and the measured parameter, and operating the fan in accordance t with the determined fan operation state.
[0015] Furthermore, in accordance with some embodiments of the present invention, the fans include an array of fans.
[0016] Furthermore, in accordance with some embodiments of the present invention, the fan operation state is selected from the group of states consisting of: number of fans of the array that are turned on or off, rotation velocity of the fans and blade pitch of the fans.
[0017] Furthermore, in accordance with some embodiments of the present invention, the step of determining a fan operation state includes selecting a value from a lookup table of fan operation states in accordance with the acquired ambient temperature and the measured parameter.
[0018] Furthermore, in accordance with some embodiments of the present invention, the step of determining a fan operation state includes application of an algorithm generated by an algorithm generation method. The algorithm generation method includes: operating the power plant under an operating condition of substantially constant ambient temperature and a substantially constant value of a parameter indicative of the power output of the generator; operating a ventilation fan in accordance with a selected fan operation state; measuring an efficiency of the power plant; and repeating the previous steps while varying the selected fan operation state until a maximum efficiency is measured.
[0019] Furthermore, in accordance with some embodiments of the present invention, the step of determining a fan operation state includes application of an algorithm generated by an algorithm generation method. The algorithm generation method includes: simulating operation of the power plant under an operating condition of substantially constant ambient temperature and electric power output; simulating operation of a ventilation fan in accordance with a selected fan operation state; calculating a simulated efficiency of the power plant; and repeating the previous steps while varying the selected fan operation state until a maximum simulated efficiency is calculated.
[0020] Furthermore, in accordance with some embodiments of the present invention, the algorithm is a computer executable algorithm.
[0021] There is further provided, in accordance with some embodiments of the present invention, a control system for controlling operation of one or more ventilation fans of an air-cooled condenser for condensing exhaust steam from a steam turbine of an electric power plant, the steam turbine powering an electric power generator. The system includes a controller for receiving an ambient temperature and a parameter indicative of the power output of the generator, for determining a fan operation state based on the received ambient temperature and parameter, and for operating the fan in accordance with the determined fan operation state.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] In order to better understand the present invention, and appreciate its practical applications, the following Figures are provided and referenced hereafter. It should be noted that the Figures are given as examples only and in no way limit the scope of the invention. Like components are denoted by like reference numerals.
[0023] Fig. 1 is a block diagram of a combined cycle electrical power plant in accordance with embodiments of the present invention.
[0024] Fig. 2 A illustrates an air cooled condenser such as may be used in a system operated in accordance with embodiment of the present invention. [0025] Fig. 2B shows the interior of the air cooled condenser shown in Fig. 2B.
[0026] Fig. 3 is a flow chart of a method for condenser ventilation fan control in accordance with embodiments of the present invention.
[0027] Fig. 4 shows a condenser ventilation fan control lookup table in accordance with some embodiments of the present invention.
[0028] Fig. 5 is a flowchart of a method for generation a control algorithm in accordance with embodiments of the present invention.
DETAILED DESCRIPTION OF EMBODIMENTS
[0029] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, modules, units and/or circuits have not been described in detail so as not to obscure the invention.
[0030] Embodiments of the invention may include an article such as a computer or processor readable medium, or a computer or processor storage medium, such as for example a memory, a disk drive, or a USB flash memory, encoding, including or storing instructions, e.g., computer-executable instructions, which when executed by a processor or controller, carry out methods of the disclosed embodiments.
[0031] Control of a ventilation fan for cooling a condenser for condensing exhaust steam from a steam turbine, in accordance with embodiments of the present invention, is based on two measured quantities: the ambient air temperature and a parameter indicative the electrical power output of a generator powered by the steam turbine. For example, the parameter may be a direct measurement of the output power of the generator, or may be related to the power input to a power plant of which the steam turbine is part (e.g. a fuel combustion rate). The parameter is typically indicative of the force or torque required to maintain rotation of the turbine.
[0032] A condenser cooling fan for a steam turbine is typically designed to cause air to flow through one or more cooling panels of a steam turbine condenser. The steam turbine and its condenser may typically be part of a combined cycle power plant. In a combined cycle power plant, a hot compressed gas is generated by combustion, for example, of natural gas or fuel oil. The hot compressed gas is allowed to expand through, and drive, a gas turbine. The hot exhaust gas from the gas turbine is conducted into a heat exchanger. In the heat exchanger, the exhaust gas heats water, or another suitable fluid, to form pressurized steam, or vapor. Alternatively, steam (used hereinafter to refer to either water vapor or vapor of another liquid) may be generated directly using a power source to heat water (used hereinafter to refer to any suitable liquid) in a boiler or heat exchanger. Such power sources may include, for example, combustion of coal, fuel oil, or natural gas, or may include heat generation by an alternative source such as, for example, a nuclear reactor, solar heating, or geothermal heating.
[0033] The pressurized steam may then be conducted to an intake of a steam turbine. The hot pressurized steam passes through the steam turbine, rotating and powering it, - and exits as exhaust steam. Rotation of the steam turbine is typically utilized to power, an electric power generator. The exhaust steam that exits from the steam turbine may be conducted to a condenser, where the exhaust steam is cooled and condensed to a condensate. The condenser reduces the pressure of the exhaust steam to less than the pressure at the steam turbine intake. Increasing the difference in steam pressure between the turbine intake and exhaust may increase the force or torque of the pressurized intake steam on the steam turbine. When the pressure increase is attained by reducing the exhaust pressure, the increased pressure difference may result in increased efficiency (ratio of energy output to energy input) of the turbine operation.
[0034] The liquid condensate that is formed by condensation of the exhaust steam in the condenser is collected in a condensate collection container. Typically, condensate collection utilizes gravity to collect the condensate in a condensate collection container located near the bottom of the condenser. The collected condensate may then be conducted back to the heat exchanger to be reheated to form pressurized steam to again power the steam turbine.
[0035] In a typical air-cooled condenser, steam in the condenser is directed through a cooling panel that includes an array or bundle of narrow pipes. The narrow pipes of the condenser bundle are spaced such that air may flow between the pipes. Air passing between the pipes of the bundle may thus cool the fluid, both steam and condensate, within the pipes. Any steam flowing through the panels is cooled to condensate to be collected in a condensate collection container. The rate of cooling of the panels is typically dependent, among other factors, on the velocity of the air flowing between the pipes. Thus, actively moving the air by means of a fan may increase the cooling rate of the fluid in the pipes. Turning the fan on, or increasing the rotation velocity of the fan blades, may result in more rapid cooling of the fluid in the pipes. On the other hand, while turning a fan off or reducing its rotation velocity decreases the cooling rate. Typically, a condenser includes an array of several fans, each fan blowing air through a different section of the cooling panel. Therefore, controlling a fan that blows air through one section of the cooling panel may determine the temperature of a condensate collected from that section.
[0036] Condensate formed in several sections of the cooling panel is typically collected ^ in a single condensate collection container. Separately controlling operation of two or more ventilation fans of a condenser may assist in controlling the temperature of the , condensate collected in the condensate collection container. For example, a typical condenser may include two elongated rectangular panels arranged in the form of an elongated sloped roof, having a cross section in the form of an inverted V shape. Steam is fed into the cooling panels from above via a horizontal steam duct that is located at the apex of the inverted V shape and is open to the cooling panels. Cooling fans may be arranged along the length of the panel structure at the base of the inverted V shape. The cooling fans are typically spaced at regular intervals along the length of the panel structure. The fans typically are arranged with their fan blade rotation axes oriented vertically. Thus, when a fan is in operation, the fan blows cooling air upward between the cooling panels such that the blown air flows upward and outward through the panels. Condensate within the panels may then flow downward into a condensate collection container.
[0037] The temperature of the condensate collected in the condensate collection container may depend partially on the cooling rate of the fluid in the cooling panels. The cooling rate of the fluid in the cooling panels may depend partially on the flow rate of air through the cooling panels. The flow rate of the air may be controlled by controlling the number of fans in operation or the rotation velocities of the fans. Thus, for example, the number of fans that are turned on or off may be varied by a controller in accordance with predetermined requirements, such as one or more measured quantities.
[0038] For example, control of a condenser fan in accordance with embodiments of the present invention depends on two quantities. One measured quantity is a parameter that indicates the electrical power output of a generator that is powered by a steam turbine whose exhaust steam is to be condensed by the condenser. Electrical power meters that are capable of producing a digital or analog electrical output signal that indicates the measured electrical power are well known in the art. The electrical power output of a generator is generally routinely monitored for existing electrical power generators. Thus, measurement of the generator output power parameter may be compatible with existing power plants. Alternatively, the generator output power parameter may include a measured value that is related directly or indirectly to generator output. For example, the measured parameter may include a measured rate of fuel consumption or steam production, a boiler steam temperature or pressure, or any other parameter that may indicate generator output.
[0039] The second measured quantity is the ambient air temperature in the vicinity of the condenser. For example, one or more thermometers may be positioned near the air intake of one or more condenser fans. Thermometers that are capable of producing a digital or analog electrical output signal that indicates the measured temperature are well known in the art.
[0040] Output signals indicating the values of the measured generator output power parameter and the ambient temperature may be input to a controller. Each output signal may be transmitted from the appropriate meter to the controller via a suitable communications cable, or may be transmitted wirelessly. The. controller may include one or more automatically operating processors, such as one or more programmable computers or microprocessors. For example, a processor may be programmed to read the input measurement signals and to output one or more instructions that control the number of fans to operate, or the fan speeds. A controller may also be understood to include one or more human operators operating in accordance with predetermined instructions based on the measured parameter and ambient temperature. [0041] For example, a controller may include a processor operating in accordance with a control algorithm. For example, the control algorithm may determine the number of ventilation fans to operate with a given measured generator electrical power output and a given measured ambient temperature. The algorithm may include one or more theoretically, empirically, or semi-empirically derived formulas, or one or more indexed lookup tables. For a given set of measured parameters, the algorithm may output a control signal that indicates such factors as: how many ventilation fans to operate, which fans of an array of ventilation fans to operate, a blade pitch (attack angle) for each fan, or a blade rotational velocity for each fan. Typically, the algorithm may output a single value that indicates a relative fan cooling rate. The fan cooling rate value may indicate a family of fan control states that may be implemented to yield similar fan cooling rate values. For example, a fan cooling rate value indicating 50% of maximum cooling capacity may be implemented by turning off half the fans or by running all fans., at approximately half their capacity. The control signals may typically be transmitted, via communications cable or wirelessly, directly to one or more devices that control operation of the condenser fans. Alternatively, the processor may transmit or display instructions to a human operator who may then act in accordance with the instructions to control operation of the fans.
[0042] An algorithm for determining operation of the fans may be generated by one or more methods. For example, parameters describing characteristics and operation of a turbine and condenser system may be input to an appropriate system simulator or simulation computer program, such as, for example, Thermoflex. Such simulation systems and programs are known in the art. For example, a series of such simulations may be run with the generator output and ambient temperature as variable input parameters. Each simulation may yield as its output an optimal mode of operation of the ventilator fans. The mode of operation may include defining which fans should be on and which should be off and, optionally, the speeds of the fans. The results may be output in the form of parameters of one or more empirical or semi-empirical formulas, or in the form of a lookup table.
[0043] Alternatively to performing a simulation, the optimum fan operation as a function of generator power output and ambient temperature may be determined empirically during operation of the steam turbine. For example, performance may be monitored during routine operation so as to generate a lookup table. Alternatively, the system may be operated specifically for the purpose of generating the lookup table, with operation parameters being varied in a systematic fashion.
[0044] Another option is to generate a general algorithm via simulation, and to adapt the algorithm to a particular system by operation of the system under various conditions. For example, an algorithm may include one or more theoretically or empirically derived parameterized formulas. The parameters of the parameterized formulas may be determined experimentally during operation of the system.
[0045] Another option is to determine an algorithm by operating the system under a limited set of operating conditions. A simulation may then be used to extrapolate the algorithm to other operating conditions.
[0046] Reference is now made to the accompanying Figures.
[0047] Fig. 1 is a block diagram of a combined cycle electrical power plant in accordance with embodiments of the present invention. Energy for powering combined cycle power plant 10 is provided by combustion source 12. Combustion source 12 provides hot gas 14 to gas turbine 16. Gas turbine 16 emits exhaust gas 18. Exhaust gas 18 heats supply water 48 in heat exchanger 20 to form pressurized steam 22. Pressurized steam 22 is directed into, and drives, steam turbine 24. Steam turbine 24 is coupled to generator 26. Generator 26 provides electric power to a consumer of electric power, such as, for example, power grid 28, or to a factory or similar facility. Electric power output of generator 26 may be measured by electric power meter 27.
[0048] Exhaust steam 56 from steam turbine 24 is conducted into condenser 30. Components of condenser 30 that are shown schematically in Fig. 1 are also shown in Fig. 2A and Fig. 2B. Fig. 2A illustrates an air cooled condenser such as may be used in a system operated in accordance with embodiment of the present invention. Fig. 2B shows the interior of the air cooled condenser shown in Fig. 2B. Exhaust steam 56 is conducted into steam duct 46 of condenser 30. Steam from steam duct 46 is conducted into pipes 51 of cooling panels 50. One or more ventilation fans 42, such as ventilation fans 42a-42d, draw outside air 40 into central space 55 of condenser 30. Air in central space 55 is then forced outward as out-flowing air 44 through spaces 53 of cooling panels 50. Thermometer 39 may measure the temperature of outside air 40.
[0049] Steam in cooling panels 50 may be cooled to form condensate 52. Condensate 52 may be conducted, typically under the force of gravity, to condensate collection container 36 where it is collected as collected condensate 54. Collected condensate 54 may be then conducted from condensate collection container 36 as supply water 48 to heat exchanger 20 for conversion to pressurized steam 22.
[0050] Operation of ventilation fans 42 is controlled by controller 34. Controller 34 may include one or more automated devices, such as an analog computer or a programmed digital processor or computer, or may, alternatively or in addition, include one or more human operators operating controls in accordance with of instructions. Controller 34 receives ambient temperature data 33 from thermometer 39 through a wired or wireless communications channel. Similarly, controller 34 receives generator . power output data 32 from electrical power meter 27. Controller 34 applies an algorithm . ; based on the received values of the ambient temperature and the generator power and generates fan operation instructions 41 for operating a motor 43 of a ventilation fan 42. For example, fan operation instructions 41 may include instructions to turn on or off one or more of ventilation fans 42, for example, one or more of fans ventilation 42a-42d. As another example, operation instructions 41 may include instructions to change the blade rotation velocity of one or more of ventilation fans 42, for example, one or more of ventilation fans 42a-42d.
[0051] Fig. 3 is a flow chart of a method for condenser ventilation fan control in accordance with embodiments of the present invention. It should be understood that in the flow chart, the division of the method into individual steps is illustrative only, and that alternative divisions into steps may yield identical results. Such alternative division into steps should be understood as being included within the scope of the present invention. Also, the order of the steps shown is illustrative only, and some steps of the method may be performed in a different order or concurrently without affecting the results. Such alternative orders of steps should also be understood as being included within the scope of the present invention. [0052] A condenser ventilation fan controller operating in accordance with the method acquires a value of the ambient air temperature (step 60). For example, the controller may query a thermometer that is located so as to measure the temperature of the ambient air. The acquired ambient temperature value may optionally be adjusted to account for one or more additional environmental or meteorological factors that may affect condenser air cooling. Such factors may include, for example, wind direction and velocity and relative humidity. Similarly, the controller acquires the value of a parameter indicative of the electric power output of a generator being run by the steam turbine whose exhaust is condensed by the condenser (step 62). For example, the controller may query an electric power meter connected to out connection points of the generator. The controller compares the acquired values with values stored from a previous acquisition, if any (step 64). If the acquired values are substantially similar to the stored values, where substantially similar may be defined for each value in ,*·. accordance with predetermined criteria, the acquired values are stored in place of the . previously stored values. The previous steps, starting from step 60, are then repeated after a pre-defined interval. For example, values may be acquired at a typical time interval of once every ten minutes. A change in electric power output or load may also trigger repetition of the steps.
[0053] If the acquired values are different, in accordance with predefined criteria, from the stored values, the acquired values are stored in place of the previously stored values (step 66). A control algorithm then is applied using the acquired ambient temperature and generator output power values as input parameters (step 68) to generate ventilation fan control instructions. For example, the algorithm may include finding a value in a lookup table that is indexed by ambient temperature and generator output power parameter. The indexed value in the lookup table may indicate, for example, how many ventilation fans to turn on and how many to turn off, which ventilation fans of a ventilation fan array to operate, or the operation speed of each ventilation fan. Alternatively, the algorithm may include applying a formula or a set of instructions to determine the ventilation fan control instructions. Alternatively, separate algorithms that may differ from one another may be provided for different subsets of one or more ventilation fans of a ventilation fan array. [0054] An algorithm may also be dependent on additional parameters that affect the cooling rate. For example, the algorithm may be dependent on wind velocity. For example, the validity of a given lookup table may be limited to a given range of wind conditions.
[0055] Fig. 4 shows a condenser ventilation fan control lookup table in accordance with some embodiments of the present invention. The lookup table may be typical for a particular power plant configuration. Each row of the lookup table represents a range of ambient temperatures (here given in units of degrees Celsius). Each column of the table represents a generator output parameter (expressed as a percent of maximum capacity). For example, if the ambient temperature is 12°C and the generator is operating at 50% capacity, the table indicates that the required cooling rate is 75% to 80% of maximum cooling capacity. In order to achieve 75% to 80% cooling capacity, 20% to 25% of the ventilation fans may be turned off. Alternatively, all fans may be operated at 75% to 80% of their maximum capacities (for example, by reducing their rotation velocities).
[0056] Referring again to Fig. 3, once the ventilation fan control instructions are generated, the generated instructions are applied (step 70). For example, the controller may be connected to motors of the ventilation fans such that the controller may directly control electric power to the fan motors. Alternatively, the controller may transmit a control signal to a motor control device associated with the fan motor such that the motor control device may control the fan motor in accordance with the transmitted signal. Such a motor control device may optionally communicate the current status of the ventilation fans to the controller. The fan status data may be input as an input parameter to the control algorithm.
[0057] Prior to application of the control method shown in Fig. 3, the control algorithm applied during step 68 must be generated. For example, a lookup table must be prepared that yields a fan control state for a given combination of acquired ambient temperature and generator output parameter. Fig. 5 is a flowchart of a method for generation a control algorithm in accordance with embodiments of the present invention. It should be understood that in the flow chart, the division of the method into individual steps is illustrative only, and that alternative divisions into steps may yield identical results. Such alternative division into steps should be understood as being included within the scope of the present invention. Also, the order of the steps shown is illustrative only, and some steps of the method may be performed in a different order or concurrently without affecting the results. Such alternative orders of steps should also be understood as being included within the scope of the present invention.
[0058] The control algorithm may be generated by actual or simulated operation of the steam turbine and condenser. All steps of the method referring to operation of the turbine and generator, of the condenser ventilation fans, or of operation at a given ambient temperature, should be understood as equally applying to actual operation, simulated operation, or to a combination of actual and simulated operation. For example, simulated operation may be followed by actual operation to verify the generated algorithm, or to make adjustments to the generated algorithm. Alternatively, actual operation under a limited set of operating conditions may be supplemented by simulated operation. Simulated operation may be utilized to extrapolate a generated - algorithm to include operating conditions that were not achieved during actual - operation. For example, various environmental or economic constraints may have, precluded actual operation at all desired operating conditions.
[0059] Operating conditions for the steam turbine and condenser are determined or measured, either as parameters of simulated operation or as operating conditions for actual operation. These operating conditions include determining the ambient temperature (step 72) and the output electric power of a generator that is run by the steam turbine (step 74). An initial value for best efficiency attained thus far is stored (step 76). For example, a typical initial value may be zero. An initial fan operation state is selected (step 78). A fan operation state may include determining which fans are turned on and which are turned off, and the operation speeds of the fans. The power generation system that includes the steam turbine and condenser is then operated (either actually or in simulation) under these conditions. The efficiency of the system with the current fan operation state is determined (step 80). For example, a measure of the efficiency may include a value proportional to the generated electrical power output divided by the rate of fuel consumption while generating the electrical energy.
[0060] The current system efficiency with the current fan operation state is compared to the stored best value (step 82). If the current system efficiency is greater than the stored value, the current fan operation state is stored, replacing the previously stored state, if any (step 84). Similarly, the stored best efficiency value is replaced with the current system efficiency. If the current system efficiency is not greater than the previously stored value, the method proceeds to step 88.
[0061] The next step of the method is to check whether all fans operation states that are to be tested have been tested already with the current operating conditions (step 88). If not, a new fan state to be tested is selected in accordance with predetermined criteria (step 89). The new state is then tested (returning to step 80).
[0062] When all fan states have been tested for the given operating conditions, the stored fan operation state is incorporated into the algorithm as the optimum fan operation state for the operating conditions (step 90). For example, a fan operation state defined by the number of ventilation fans in operation may be incorporated into a lookup table indexed by the ambient temperature and generator output power of the current operating conditions. Alternatively, the fan operation state may be used to determine parameters of a function or other set of instructions for determining the optimum fan operation state given a set of operating conditions.
[0063] Another set of operating conditions, for example, characterized by a new ambient temperature value or generator output power value (step 92) may then be determined. The optimum fan operation state for the new operating conditions may then be found (returning to step 76).
[0064] Thus, a control is provided for efficient operation of a steam turbine condenser by means of an open loop control system.
[0065] It should be clear that the description of the embodiments and attached Figures set forth in this specification serves only for a better understanding of the invention, without limiting its scope.
[0066] It should also be clear that a person skilled in the art, after reading the present specification could make adjustments or amendments to the attached Figures and above described embodiments that would still be covered by the present invention.

Claims

1. A method for controlling operation of one or more ventilation fans of an air- cooled condenser for condensing exhaust steam from a steam turbine of an electric power plant, the steam turbine powering an electric power generator, the method comprising:
acquiring an ambient temperature;
measuring a parameter indicative of the power output of the generator;
determining a fan operation state based on the acquired ambient temperature and the measured parameter; and
operating the fan in accordance with the determined fan operation state.
2. A method as claimed in claim 1 wherein said one or more fans comprises an array of fans.
■i 3. A method as claimed in claim 2, wherein the fan operation state is selected from the group of states consisting of: number of fans of the array that are turned on or off, rotation velocity of the fans and blade pitch of the fans.
4. A method as claimed in claim 1 , wherein the step of determining a fan operation state includes selecting a value from a lookup table of fan operation states in accordance with the acquired ambient temperature and the measured parameter.
5. A method as claimed in claim 1, wherein the step of determining a fan operation state includes application of an algorithm generated by an algorithm generation method comprising:
operating the power plant under an operating condition of substantially constant ambient temperature and a substantially constant value of a parameter indicative of the power output of the generator;
operating a ventilation fan in accordance with a selected fan operation state; measuring an efficiency of the power plant;
repeating the previous steps while varying the selected fan operation state until a maximum efficiency is measured.
6. A method as claimed in claim 1, wherein the step of determining a fan operation state includes application of an algorithm generated by an algorithm generation method comprising:
simulating operation of the power plant under an operating condition of substantially constant ambient temperature and electric power output;
simulating operation of a ventilation fan in accordance with a selected fan operation state;
calculating a simulated efficiency of the power plant;
repeating the previous steps while varying the selected fan operation state until a maximum simulated efficiency is calculated.
7. A method as claimed in claim 1, wherein the algorithm is a computer executable algorithm.
8. A control system for controlling operation of one or more ventilation fans of an air-cooled condenser for condensing exhaust steam from a steam turbine of an electric power plant, the steam turbine powering an electric power generator, the system comprising a controller for receiving an ambient temperature and a parameter indicative of the power output of the generator, for determining a fan operation state based on the received ambient temperature and parameter, and for operating the fan in accordance with the determined fan operation state.
PCT/IL2010/001048 2009-12-23 2010-12-13 Condenser ventilation control WO2011077427A1 (en)

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