JP5400850B2 - Method and apparatus for controlling exhaust heat boiler system - Google Patents

Description

  The present invention relates to a method and apparatus for controlling the operation of an exhaust heat boiler system that receives thermal energy from a plurality of heat sources.

  In recent years, cogeneration systems (exhaust heat boiler systems) that use exhaust heat from various heat engines such as gas turbine engines in power generation apparatuses to heat boilers have become widespread. As such an exhaust heat boiler system, in order to increase the output of the exhaust heat boiler, two heat sources are provided, for example, in addition to the heat engine, hot exhaust gas from this heat engine is supplied to the exhaust heat boiler. It has been proposed to provide a duct burner in the middle of the exhaust gas passage.

  Also, when a duct burner is provided in the middle of the exhaust gas passage in this way, in order to continue operation without stopping the exhaust heat boiler even if the heat engine stops for any reason, on the upstream side of the duct burner, It is known to provide a blower that blows air to the duct burner in parallel with the exhaust gas passage. In this case, an exhaust bypass valve for bypassing the exhaust gas from the exhaust heat boiler is provided in the middle of the exhaust gas passage from the heat engine, and the opening degree of the exhaust bypass valve is adjusted so that the heat engine is in operation. The amount of exhaust gas supplied from the heat engine to the exhaust heat boiler, that is, the amount of heat is adjusted.

JP 2004-225966 A

  However, in this way, when a plurality of heat sources are provided to control the steam pressure of the exhaust heat boiler, depending on whether one of the heat sources (for example, the heat engine here) is in an operating state or in a stopped state, The magnitude of the influence of the control amount of the other heat source (for example, duct burner) on the steam pressure of the boiler to be controlled varies depending on the opening degree of the exhaust bypass valve when the engine is in an operating state. That is, due to such fluctuations in the operating state, the optimality of the control constant of the duct burner is lost, and it becomes difficult to stably control the steam pressure of the exhaust heat boiler.

  Accordingly, an object of the present invention is to provide a control method and a control device for stably operating an exhaust heat boiler system including a plurality of heat sources in order to solve the above-described problems.

  In order to achieve the above object, a control method or control apparatus for an exhaust heat boiler system according to the present invention includes a heat engine that drives a load to release exhaust heat, one or more other heat sources, and the heat engine. And an operation of a waste heat boiler system including a waste heat boiler that receives heat energy from a heat source, wherein a fuel control constant of the heat source is changed according to the operation and non-operation of the heat engine By doing so, the physical quantity related to the steam pressure of the exhaust heat boiler is maintained at a predetermined value. The heat engine is, for example, a gas turbine engine, and the heat source is, for example, a duct burner. The physical quantity is, for example, the fuel flow rate of the duct burner or the vapor pressure of the exhaust heat boiler.

  According to this configuration, the fuel control constant is changed according to the operation and non-operation of the heat engine that greatly affects the control sensitivity of the heat source, so an appropriate fuel control constant is set according to the operation status of the exhaust heat boiler system. Therefore, the system can be stably operated.

  In an embodiment of the present invention, the exhaust bypass valve is further provided with a rotary exhaust bypass valve that bypasses at least a part of the exhaust gas from the heat engine so as not to be supplied to the exhaust heat boiler. It is preferable to maintain the physical quantity at a predetermined value by correcting an opening degree control constant for controlling the rotation angle to a small value as the rotation angle increases. Furthermore, it is preferable to control the exhaust bypass valve by adding a delay time to the opening degree control constant. According to these configurations, in the control based on the opening degree of the exhaust bypass valve, in which the pressure control of the exhaust heat boiler is likely to be unstable, the opening degree of the exhaust bypass valve is more stably controlled, thereby further increasing the system. It becomes possible to drive stably.

  According to the control method or the control device according to the present invention, as described above, the exhaust heat boiler system including a plurality of heat sources can be operated extremely stably.

It is a block diagram showing a schematic structure of an exhaust heat boiler system provided with a control device concerning one embodiment of the present invention. It is a block diagram which shows schematic structure of the control apparatus of FIG. It is a block diagram which shows the example of the driving | running state of the waste heat boiler system of FIG. It is a graph which shows the control characteristic of the waste heat boiler system of FIG. It is a block diagram which shows the example of the driving | running state of the waste heat boiler system of FIG. Ru block view showing an example of operating conditions of the waste heat boiler system of Figure 1.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration of an exhaust heat boiler system BS provided with a control device 1 that executes a control method according to an embodiment of the present invention. The exhaust heat boiler system BS includes a heat engine (in this example, a gas turbine GT) that drives the load L to release exhaust heat, a heat source (in this example, the duct burner 3) provided separately from the heat engine, An exhaust heat boiler 5 that receives heat energy including the exhaust heat from a heat engine and a heat source to generate steam is provided as a main component. In the present embodiment, a generator is used as the load L.

  The gas turbine engine GT is connected to a compressor 11 that compresses air, a combustor 13 that supplies fuel to the compressed air from the compressor 11 to burn, and a compressor 11 that is connected to the compressor 11 via a rotary shaft 15. And a turbine 17 that is driven by the combustion gas from 13 and exhausts high-temperature exhaust gas, and drives a load L such as a generator connected to the rotating shaft 15.

  A high temperature gas supply path 21 for supplying a high temperature gas for supplying heat energy to the exhaust heat boiler 5 is bifurcated on the upstream side, and a turbine 17 of the gas turbine engine GT is connected to one end thereof. A blower 23, for example, a blower fan is installed at the other end. In the following explanation, one side of the bifurcated branch of the hot gas supply path 21 is connected to the gas turbine engine GT, the turbine exhaust path 25, and the other bifurcated branch blower 23 is installed. The portion on the downstream side of the blower passage 27 and the branching portion 29 (that is, the joining portion of the turbine exhaust passage 25 and the blower passage 27) is referred to as a boiler supply passage 31. The duct burner 3 is provided in a portion slightly downstream of the branch portion 29 of the boiler supply path 31, and further heats the exhaust gas from the gas turbine engine GT as necessary.

  The downstream end of the boiler supply path 31 is connected to a first gas discharge path 33 that discharges the exhaust gas after being used for heating the water supply system of the exhaust heat boiler system BS. Further, in the middle of the turbine exhaust passage 25, an exhaust gas bypass passage 35 is connected to bypass the turbine exhaust from the exhaust heat boiler 5 and adjust the amount of high-temperature gas supplied to the exhaust heat boiler 5. A rotating exhaust bypass valve 41 is provided at a connection portion between the turbine exhaust duct 37 forming the turbine exhaust path 25 and the exhaust gas bypass duct 39 forming the exhaust gas bypass path 35. In the exhaust bypass valve 41, the turbine exhaust passage 25 is completely blocked from the state where the inlet to the exhaust gas bypass passage 35 is completely closed and the entire amount of turbine exhaust is sent to the boiler supply passage 31 (fully closed state). Thus, it is possible to set an arbitrary opening, that is, a rotation angle α until a state where the entire amount of turbine exhaust is sent to the exhaust gas bypass passage 35 (fully opened state).

  On the other hand, in the middle of the air duct 43 forming the air passage 27, a rotary air valve 45 is provided. When the air blower 23 does not operate, the air passage 27 is completely blocked by the air valve 45. When the blower 23 is in operation, the blower valve 45 is fully opened.

  The exhaust heat boiler 5 is a steam that generates steam by receiving the heat energy of the exhaust gas that passes through the boiler supply passage 31 from the boiler drum 51 to which water from the water supply passage 47 is supplied and the water supplied to the boiler drum 51. Generator 53. In the middle of the water supply path 47, a economizer 55 for preliminarily heating the water supplied to the exhaust heat boiler 5 is provided. On the other hand, a superheater 59 for further heating the output steam is provided in the middle of the output path 57 for outputting the steam generated in the exhaust heat boiler 5. The steam generator 53, the economizer 55, and the superheater 59 are all disposed in the boiler supply path 31, and are heated using the heat of the exhaust gas that passes through the boiler supply path 31.

  As shown in FIG. 2, the control device 1 compares the detected steam pressure value detected by the pressure monitor 61 that monitors the steam pressure in the boiler drum 51 with a preset steam pressure command value, By controlling the fuel supply amount to the duct burner 3, the steam pressure in the boiler drum 51 is maintained at a predetermined value, that is, a steam pressure command value. More specifically, the control device 1 operates and disables the fuel control constant setting unit 65 that sets a fuel control constant for controlling the amount of fuel supplied to the duct burner 3 and the gas turbine engine GT that is a heat engine. A change circuit 67 for changing the fuel control constant according to the operation is provided.

  In the control device 1, the steam pressure command value setting unit 69 sets the steam pressure command value, and the fuel control valve is based on the deviation between the steam pressure command value and the detected steam pressure value and the fuel control constant of the fuel control constant setting unit. By controlling 71, the amount of fuel supplied to the duct burner 3 is controlled. The fuel control constant of the fuel control constant setting unit 65 is changed by the change circuit 67 according to whether the gas turbine engine GT is in an operating state or an inactive (stopped) state, as will be described in detail later. .

  Further, the control device 1 is provided with an opening degree control constant setting unit 75 for setting an opening degree control constant for controlling the turning angle α of the exhaust bypass valve 41, and the opening degree control constant is turned. A correction circuit 77 is provided for correcting the value to a smaller value as the angle α increases.

  Hereinafter, the operation of the control device 1 according to the operation status of the exhaust heat boiler system BS, particularly the operation status of the gas turbine engine GT which is a heat engine will be described.

(1) When Gas Turbine Engine GT is Stopped While the gas turbine engine GT is stopped, as shown in FIG. 3, the exhaust bypass valve 41 is in a fully opened state, and the turbine exhaust passage 25 is connected to the exhaust bypass valve 41. It is blocked by The pressure control of the boiler in this case is controlled by the amount of combustion air sent by the blower 23 and the fuel flow rate of the duct burner 3, but since the range to be controlled by the duct burner 3 is wide, the fuel control constant is set to a larger value. It is preferable to set. As shown in FIG. 4, the fuel flow rate of the duct burner 3 and the steam generation amount of the exhaust heat boiler 5 during the stop of the gas turbine engine GT are in a substantially proportional relationship, and the fuel control of the duct burner 3 is performed as it is. Pressure control.

(2) When the gas turbine engine GT is operating In the state where the gas turbine engine GT is operating, the steam load of the exhaust heat boiler 5 is small, and the exhaust heat boiler is obtained only by the amount of heat of the turbine exhaust from the gas turbine engine GT. When the steam pressure required for 5 can be achieved, the duct burner 3 is not used. In this case, as shown in FIG. 5, the exhaust bypass valve 41 of the turbine exhaust passage 25 is fully closed or partially closed, and is supplied to the exhaust heat boiler 5 by controlling the rotation angle α of the exhaust bypass valve 41. The amount of turbine exhaust, that is, the amount of heat given to the exhaust heat boiler 5 is controlled. Since the pressure of the exhaust heat boiler 5 varies by controlling the amount of heat given to the exhaust heat boiler 5, as a result, the pressure of the exhaust heat boiler 5 is controlled by controlling the rotation angle α of the exhaust bypass valve 41. Is done.

  On the other hand, when the steam load is large and the required steam pressure cannot be output only by the heat quantity of the turbine exhaust, the exhaust bypass valve 41 is fully closed and the exhaust gas is supplied to the exhaust heat boiler 5 as shown in FIG. In addition, the duct burner 3 is also used. When the exhaust gas calorific value on the gas turbine engine GT side is almost fixed with no adjustment allowance, the change in the steam load is mainly controlled by the duct burner 3. A fuel control constant different from that for control is required. That is, the fuel control constant needs to be changed depending on whether or not the gas turbine engine GT is operated, and is set to a value smaller than the fuel control constant when the gas turbine engine GT is stopped by the change circuit 67 of FIG. To do.

(3) Transition from Stopped State of Gas Turbine Engine GT to Operating State During operation of exhaust heat boiler 5 when gas turbine engine GT is stopped, exhaust bypass valve 41 is open as shown in FIG. . When the gas turbine engine GT enters the operating state and the steam load increases, the exhaust bypass valve 41 on the gas turbine engine GT side is gradually closed from the state of FIG. 3, and finally, as shown in FIG. The entire amount of turbine exhaust is sent to the exhaust heat boiler 5. At this time, since the control sensitivity of the duct burner 3 decreases, it is necessary to increase the fuel control constant of the duct burner 3. However, if the fuel control constant is instantaneously changed in either the fully closed state or the fully open state of the exhaust bypass valve 41, the control during the transition from the fully closed state to the fully open state of the exhaust bypass valve 41 is extremely unstable. Become. Therefore, it is necessary to change the fuel control constant gradually in accordance with the opening degree of the exhaust bypass valve 41. In this case, the fuel control constant is changed by controlling the rotation angle α of the exhaust bypass valve 41 while decreasing the opening degree control constant as the rotation angle α increases using the correction circuit 77 of FIG. Can be performed stably.

(4) Transition from Gas Turbine Engine GT Operating State to Stopped State When the gas turbine engine GT is in an operating state and the duct burner 3 is also in an operating state, the exhaust bypass valve 41 is closed as shown in FIG. When the gas turbine engine GT is stopped, the exhaust bypass valve 41 is gradually shifted from the fully closed state to the fully opened state in FIG. 3, and the entire amount of turbine exhaust is sent to the exhaust gas bypass passage 35 side. At this time, since the control sensitivity of the duct burner 3 increases, the fuel control constant needs to be set low. However, when the control constant is changed instantaneously in either the fully open state or the fully closed state of the exhaust bypass valve 41, the control during the transition from the fully closed state to the fully open state of the exhaust bypass valve 41 becomes unstable. . Therefore, it is desirable to change the control constant in accordance with the opening degree of the exhaust bypass valve 41. In this case, similarly to the above (3), the rotation angle α of the exhaust bypass valve 41 is controlled using the correction circuit 77 of FIG. 2 while decreasing the opening degree control constant as the rotation angle α increases. Thus, the fuel control constant can be changed stably.

Note that the control characteristic when the steam pressure is adjusted by the exhaust bypass valve 41 usually has a non-linear characteristic, so that the opening degree control constant has a quadratic function characteristic with respect to the opening degree. Further, in the pressure control by the exhaust bypass valve 41, since the time delay is large for the heat amount change with respect to the opening of the exhaust bypass valve 41, the value of the opening control constant is set small, and the fuel control constant on the burner side is increased. Setting is preferable. In this case, as shown in FIG. 2, if the delay circuit 79 is provided to add a delay time to the opening degree control constant and the exhaust bypass valve 41 is controlled, the opening degree of the exhaust bypass valve 41 can be controlled more stably. Can do.

  Thus, according to the control method or the control device 1 according to the present embodiment, the fuel control constant is changed according to the operation and non-operation of the heat engine (gas turbine engine GT) that greatly affects the control sensitivity of the heat source. Therefore, it is possible to set an appropriate fuel control constant according to the operation status of the exhaust heat boiler system BS, and it is possible to operate the system extremely stably.

  In the above embodiment, the steam pressure of the exhaust heat boiler has been described as an example of the control target of the control device 1. However, the control target of the control device 1 is limited to the steam pressure as long as it is a physical quantity related to the steam pressure. For example, it is good also as the water level in a boiler drum.

  As described above, the preferred embodiments of the present invention have been described with reference to the drawings, but various additions, modifications, or deletions can be made without departing from the spirit of the present invention. Therefore, such a thing is also included in the scope of the present invention.

1 Control device 3 Duct burner (heat source)
5 Waste Heat Boiler 11 Compressor 13 Combustor 17 Turbine 41 Exhaust Bypass Valve 61 Pressure Monitor 65 Fuel Control Constant Setting Unit 67 Change Circuit 69 Steam Pressure Command Value Setting Unit 75 Opening Control Constant Setting Unit 77 Correction Circuit 79 Delay Circuit α Rotation angle of exhaust bypass valve (opening)
BS Waste heat boiler system GT Gas turbine engine (heat engine)

Claims (4)

Method for controlling operation of an exhaust heat boiler system comprising a heat engine that drives a load to release exhaust heat, one or more other heat sources, and an exhaust heat boiler that receives thermal energy from the heat engine and the heat source Because
By changing a fuel control constant for controlling the amount of fuel supplied to the heat source during operation of the heat engine according to the operation and non-operation of the heat engine, the steam pressure of the exhaust heat boiler is set to a predetermined value. To maintain
Opening control for controlling the rotation angle of the exhaust bypass valve by providing a rotary exhaust bypass valve in the system for bypassing at least part of the exhaust gas from the heat engine so as not to be supplied to the exhaust heat boiler The steam is corrected by correcting the constant to a smaller value as the rotation angle increases toward the side of bypassing the exhaust gas, and changing the fuel control constant according to the rotation angle of the exhaust bypass valve. Maintaining the pressure at a predetermined value,
A delay time is added to the opening degree control constant so as to match a time delay when the amount of heat given to the exhaust heat boiler changes with respect to the opening degree of the exhaust bypass valve to control the exhaust bypass valve. Control method of exhaust heat boiler system.   The method for controlling the exhaust heat boiler system according to claim 1, wherein the load is a generator, the heat engine is a gas turbine engine, and the heat source is a duct burner. Controlling the operation of an exhaust heat boiler system including a heat engine that drives a load to release exhaust heat, one or more other heat sources, and an exhaust heat boiler 5 that receives thermal energy from the heat engine and the heat source. A device,
A fuel control constant setting unit for setting a fuel control constant for controlling the amount of fuel supplied to the heat source during operation of the heat engine;
A change circuit for maintaining the steam pressure of the exhaust heat boiler at a predetermined value by changing the fuel control constant according to the operation and non-operation of the heat engine;
A rotary exhaust bypass valve that bypasses at least a part of the exhaust gas from the heat engine so as not to be supplied to the exhaust heat boiler is set, and an opening degree control constant that controls the rotation angle of the exhaust bypass valve is set. An opening control constant setting unit to perform,
A correction circuit for maintaining the steam pressure at a predetermined value by correcting the opening degree control constant to a small value as the rotation angle increases toward the side of bypassing exhaust gas;
A change circuit for maintaining the steam pressure at a predetermined value by changing the fuel control constant according to the rotation angle of the exhaust bypass valve;
A delay time is added to the opening degree control constant so as to match a time delay when the amount of heat given to the exhaust heat boiler changes with respect to the opening degree of the exhaust bypass valve to control the exhaust bypass valve. An exhaust heat boiler system control device having a delay circuit.   4. The exhaust heat boiler system control device according to claim 3, wherein a load of the exhaust heat boiler system is a generator, the heat engine is a gas turbine engine, and the heat source is a duct burner.

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