JP3837605B2 - Pressurized fluidized bed combined power generation system and control method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combined power generation system including a pressurized fluidized bed boiler, and more particularly, to a pressurized fluidized bed combined power generation system that controls the bed temperature or steam temperature of a fluidized bed by a bed height operation and a control method thereof.
[0002]
[Prior art]
One conventional power generation system using coal as a fuel is a pressurized fluidized bed combined power generation (PFBC) system in which coal is burned in a fluidized bed in a pressurized atmosphere and a steam turbine and a gas turbine are driven simultaneously. FIG. 7 shows an example of a pressurized fluidized bed combined power generation system. In a furnace 28 of a pressurized fluidized bed boiler, air is supplied from a combustion air nozzle 31 to a layer of fluidized medium particles on a dispersion plate 30 to form a fluidized bed 34, and fuel 47 is combusted in the fluidized bed 34. Steam is generated in the heat transfer pipe 33 in the fluidized bed 34, and the steam turbine 52 is driven by this steam. At the same time, the gas turbine 49 is driven by the high-temperature and high-pressure combustion exhaust gas 38 generated from the furnace 28. When increasing the load of the pressurized fluidized bed boiler, the bed height of the fluidized bed 34 is increased to increase the contact area with the heat transfer tube 33 and increase the amount of heat transfer. For this purpose, fluid medium particles (BM; Bed Material) 36 are introduced from the fluid medium container (BM tank) 35 into the furnace 28 via the BM supply line 45. Further, when reducing the load, the fluidized medium particles 36 forming the fluidized bed 34 are extracted from the BM extraction line 46 to the BM tank 35, thereby reducing the bed height, reducing the contact area, and reducing the amount of heat transfer.
[0003]
In a pressurized fluidized bed boiler, the amount of operation for adjusting the amount of heat transfer to steam is divided into the fuel supply amount for adjusting the amount of heat input to the pressurized fluidized bed boiler, and the layer for adjusting the heat transfer area from the fluidized bed to the heat transfer tube. Is high. In addition to the steam temperature, the bed temperature also has a state value that needs to be controlled in order to maintain a good combustion state. When the fuel supply amount is increased, the layer temperature and the steam temperature are increased, and when the fuel supply amount is decreased, the layer temperature and the steam temperature are decreased. When the bed height is increased, the bed temperature is lowered and the steam temperature is raised, and when the bed height is reduced, the bed temperature is raised and the steam temperature is lowered.
[0004]
The conventional automatic control technology for the PFBC plant has two control methods, a method for controlling the layer temperature by a layer height operation and a method for controlling the steam temperature. The control circuit of the method controlled by is shown. The bed height setting value 2 of the fluidized bed is determined as a function of the load command, and the bed temperature deviation between the bed temperature measurement value measured by the bed temperature measuring device 3 and the bed temperature setting value with respect to the bed height setting value 2 The layer height target value 9 corrected so that 5 is set to 0 is determined. When the layer temperature is controlled to fall within a certain temperature range, the dead zone setting unit 6 may set a dead zone that treats the layer temperature deviation 5 as 0 if the temperature deviation is within a certain temperature range. In the bed height operation, the bed height operation is performed so that the bed height deviation 12 between the bed height target value 9 and the bed height measurement value measured by the bed height measuring device 10 is zero. Since it is difficult to continuously perform the layer height operation to be supplied into or extracted from, the layer height operation command 14 is generated when the deviation exceeds a certain value, and the operation is stopped when the deviation becomes less than the certain value. 13 is used. In accordance with the bed height operation command 14, a fluid medium supply command 15 for supplying the fluid medium particles into the furnace or a fluid medium extraction command 16 for extracting the fluid medium particles from the furnace is transmitted to operate the bed height. The layer temperature is controlled to a set temperature or temperature zone by a control circuit as shown in FIG.
[0005]
When the load rises, the bed height is increased. At this time, the BM stored in the BM tank outside the furnace is heated to 100 ° C or less into the fluidized bed at 850 to 900 ° C. During high operation, the layer temperature decreases and the steam temperature also decreases. For stable operation of a pressurized fluidized bed combined power generation system, the steam temperature must be controlled within the allowable temperature range. For this purpose, it is necessary to keep the layer temperature above a certain temperature even if the layer temperature decreases during bed height operation. is there. Since the amount of BM introduced at one bed height operation, that is, the bed temperature decrease width increases as the bed height operation width increases, it depends on the width of the bed height deviation (hysteresis width) that starts or stops the bed height operation. The temperature drop is determined. Normally, an appropriate bed height operation width is determined by trial operation data or simulation and set as a control circuit set value. However, there may be a case where dynamic characteristics different from those predicted by the plant may be exhibited due to changes in operation load, fuel properties, and the like.
[0006]
FIG. 9 shows the time-dependent changes in the bed height target value when the load of the pressurized fluidized bed boiler is increased, and the measured values of the bed height, fluidized bed temperature, and steam temperature. Here, the state where the circuit for controlling the layer temperature by the layer height is not utilized is shown so that the characteristics can be easily understood. In the first layer height operation, the decrease range of the layer temperature becomes larger than expected, and the temperature range is low as it is. As a result, the steam temperature also greatly decreased and exceeded the allowable temperature range, and the plant fell into unstable operation.
[0007]
The reason why the layer temperature has changed at a low temperature is that the layer height operation width was repeatedly executed at a preset value. FIG. 10 shows the state of the bed height operation, the bed temperature, the steam temperature, and the BM operation side by side. In the conventional control method, the bed height operation width is the same every time. When the deviation between the bed height target value and the bed height measurement value becomes the operation start layer height deviation, the BM supply air valve is opened and the bed height deviation is stopped. When the height difference is reached, the BM supply air valve is closed. Even when the layer height operation width is too large (the layer temperature decrease width is large), the same layer height operation is performed every time, so that the layer temperature becomes low each time.
[0008]
[Problems to be solved by the invention]
In the control method of the conventional pressurized fluidized bed combined power generation system, the operation is performed to increase the bed height when the load increases, but the amount of BM that is input at the time of one bed height operation, that is, the bed height operation width As the temperature increases, the decrease in the bed temperature increases, so the appropriate bed height operation width is determined by trial operation data and simulation and set as the control circuit set value, but the plant predicts due to changes in the operation load and fuel properties, etc. May show different dynamic characteristics.
[0009]
The conventional bed height operation width is the same every time. When the deviation between the bed height target value and the bed height measurement value becomes the operation start layer height deviation, the BM supply air valve is opened. Close the air valve. Even when the bed height operation width is too large and the bed temperature drop width is large, the same bed height operation is performed every time. Therefore, each time there is a problem that the bed temperature becomes low and it takes time to recover the temperature.
[0010]
An object of the present invention is to provide a pressurized fluidized bed combined power generation system that reduces the bed height operation amount per time when the temperature change amount after the bed height operation exceeds a preset maximum allowable change amount, and It is in providing the control method.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, in the pressurized fluidized bed combined power generation system according to the present invention, the bed height deviation between the bed height target value and the bed height measurement value of the fluidized bed is not less than a preset maximum value. The bed height operation is started, and the bed height operation is stopped when the bed height deviation is below the minimum value, and the state temperature consisting of the bed temperature or the steam temperature is controlled by the bed height operation to control the steam turbine and the gas turbine. In a pressurized fluidized bed combined power generation system to be driven, measurement of the state temperature between the state temperature at the start of the bed height operation and the minimum state temperature within a certain time after the bed height operation or after the bed height operation until the next bed height operation Control circuit that calculates the amount of change between the value and the state temperature set value, and when the amount of change exceeds the preset maximum allowable change amount, the maximum or minimum value of the layer height deviation is changed per time And a control circuit for reducing the layer height operation width.
[0012]
Further, in the first control method of the pressurized fluidized bed combined power generation system, when the bed height deviation between the bed height target value and the bed height measurement value of the fluidized bed is equal to or greater than a predetermined maximum value, the bed height is increased. Pressurized flow to start the operation, stop the bed height operation when the bed height deviation is below the minimum value, and control the state temperature consisting of the bed temperature or steam temperature by the bed height operation to drive the steam turbine and gas turbine In the control method of the layer combined power generation system, the change over time of the measured value of the state temperature is recorded, and the temperature change amount between the state temperature at the start of the layer height operation and the minimum state temperature within a certain time after the layer height operation is obtained, When the temperature change amount exceeds a preset maximum allowable change amount, the maximum or minimum value of the bed height deviation is changed to reduce the bed height operation width per time.
[0013]
In the second control method, the change over time of the measured value of the state temperature is recorded, and the maximum deviation between the state temperature measured value and the state temperature set value from after the layer height operation to the next layer height operation is stored. When the deviation exceeds a preset maximum allowable variation, the maximum or minimum value of the bed height deviation is changed to reduce the bed height operation width per time.
[0014]
According to the present invention, the layer temperature measurement value is recorded over time, the minimum temperature in the recorded layer temperature is determined, and the deviation between the minimum temperature and the layer temperature target value is determined in advance for system stable operation. When the specified value is exceeded, the set value of the bed height operation width is changed to reduce the bed height operation width, thereby stabilizing the operation.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, a step in which the bed height set value 2 of the fluidized bed is determined by the function generator 1 as a function of the load command, and the bed temperature measured by the bed temperature measuring device 3 with respect to the bed height set value 2 is used. A step in which the layer height target value 9 is determined by correcting the layer temperature deviation 5 between the temperature and the layer temperature set value to 0, and the layer height target value 9 and the layer measured by the layer height measuring device 10 A step of calculating the layer height deviation 12 between the height measurement values by the subtractor 11 and a layer height operation command 14 generated from the hysteresis generator 13 when the layer height deviation 12 is equal to or greater than a predetermined maximum value. A step of starting operation, a step of generating a layer height operation command 14 from the hysteresis generator 13 when the layer height deviation 12 is less than a minimum value, and stopping the layer height operation, and a layer height operation based on the layer height operation command 14 To control the state temperature consisting of the layer temperature or the steam temperature by A method for controlling a pressurized fluidized bed combined power generation system that drives a steam turbine and a gas turbine, wherein, for example, a layer temperature of a state temperature is measured by a layer temperature measuring device 3 is measured with a layer temperature measurement value. The step of recording in the temperature change recording device 17 and the step of obtaining by the subtractor 19 the amount of temperature change between the layer temperature measurement value at the start of the layer height operation and the minimum layer temperature measurement value within a certain time after the layer height operation. And a step of calculating by the subtractor 20 that the temperature change amount exceeds a preset maximum allowable change amount (temperature change set value), and changing the maximum value or minimum value of the layer height deviation per time And a step of correcting the bed height manipulated variable smaller by the hysteresis generator 13.
[0016]
As another embodiment of the present invention, the vapor temperature of the state temperature is controlled similarly to the layer temperature as shown in FIG.
[0017]
That is, it is a control method of a pressurized fluidized bed combined power generation system that drives a steam turbine and a gas turbine by controlling the bed temperature or steam temperature by operating the bed height of the fluidized bed. When the temperature falls below the set value, the bed height operation width is corrected to be small so as to suppress the drop in the bed temperature or the steam temperature.
[0018]
The control circuit shown in FIG. 1 shows a method for controlling the layer temperature by the layer height. Based on the deviation between the bed height target value 9 obtained by correcting the bed height set value 2 with the bed temperature deviation 5 and the actual bed height measurement value measured by the bed height measuring device 10, a hysteresis is added to the bed height. The circuit for executing the operation is the same as that of the prior art shown in FIG. Here, in order to carry out the control method of the present embodiment, first, the change with time of the layer temperature measurement value measured by the layer temperature measuring device 3 is recorded in the layer temperature change recording device 17. This recording may record the layer temperature measurement value within the past certain time width. The lowest layer temperature of the recorded layer temperature measurement values is selected by the minimum value determination 18, and the layer temperature deviation (temperature change amount) between the minimum layer temperature and the layer temperature set value is obtained by the subtracter 19. The difference between the maximum bed temperature deviation output from the subtractor 19 and the temperature change set value is calculated by the subtracter 20, and the result is output as the bed height operation width command value 22 through the proportional controller 21. By this circuit, when the maximum bed temperature deviation exceeds the temperature change set value, the bed height operation width command value 22 is reduced. Conversely, when the maximum bed temperature deviation is smaller than the temperature change set value, the bed height operation width command value is growing. The layer height operation width command value is corrected so that the layer height operation width (hysteresis width) is equal to the layer height operation width command 22 by changing the setting of the operation start deviation or operation stop deviation of the layer height of the hysteresis generator. . In order to reduce the bed height operation width, there are methods of reducing the deviation between the bed height target value for starting the bed height operation and the bed height measurement value, or increasing the deviation for stopping the bed height operation.
[0019]
FIG. 3 shows a control circuit according to another embodiment of the present invention. In the embodiment shown in FIG. 1, the measured layer temperature is recorded over time, and the maximum layer temperature deviation within a predetermined time is determined. In the other embodiments, the next layer height is changed from one layer height operation. The maximum layer height deviation until the operation is used for determination. 1 is the same as the embodiment of FIG. 1 in that the layer height operation is performed by adding hysteresis so that the layer height set value becomes the layer temperature target value corrected by the layer temperature deviation. Stores the maximum deviation between the state temperature measurement value and the state temperature set value consisting of the bed temperature or steam temperature measured between the bed height operation and the next bed height operation, and the maximum deviation is the preset maximum allowable change. When the amount is exceeded, the maximum or minimum value of the bed height deviation is changed to reduce the bed height operation amount per time.
[0020]
That is, after the layer height operation, the layer temperature deviation signal 5 is stored in the storage unit 24 via the maximum value selector 25. The layer temperature deviation signal 5 at the time of the next measurement is compared with the value stored in the previous storage unit 24 by the maximum value determination unit 25, and a larger value is stored in the storage unit 24 again. The recorded maximum deviation is subtracted from the temperature change set value by the subtracter 20 and passes through the proportional controller 21 to become the layer height operation width command value 22. The point that the layer height operation width is corrected by the layer height operation width command value 22 is the same as that of the embodiment shown in FIG. When the layer height deviation 12 between the layer height target value 9 and the layer height measurement value 10 exceeds the layer height operation start deviation and the layer height operation command 14 is transmitted, the reset switch 23 that receives this signal is sent to the memory 24. The stored maximum layer temperature deviation value is deleted. As a result, the bed height operation range can be corrected by the maximum bed temperature deviation between the bed height operation and the next operation, and even if the operating conditions change for each bed height operation during load changes, It is possible to correct the layer height operation width by determining the decrease width. According to this other embodiment, by using the maximum value of the decrease in the layer temperature until the next operation after one layer height operation as a criterion, it is possible to operate the layer height operation during a load change. Even if the operating conditions change every time, it is possible to respond quickly.
[0021]
3 and 4 show a control circuit according to another embodiment of the present invention. Here, the present invention is applied to a control method for controlling the steam temperature by the bed height operation. FIG. 3 shows the same control circuit as that of the embodiment of FIG. 1 except that the vapor temperature deviation is used as a criterion for determination instead of the layer temperature. The other embodiment shown in FIG. 4 uses the deviation of the steam temperature as a criterion in place of the layer temperature in the same control circuit as that of the other embodiment of FIG.
[0022]
Next, the operation of the present invention will be described. If the bed temperature drop exceeds the expected value when the bed height is operated once, the bed height operation width will be corrected to be smaller in the next bed height operation, so the amount of BM input will be reduced and the bed temperature drop will be reduced. Can be kept small. Thereby, it can prevent that steam temperature falls exceeding the allowable value required for a plant stable operation. FIG. 5 shows the characteristics of the layer temperature and the steam temperature when the above means is used. In the case of (1) where the bed temperature and steam temperature decrease beyond the allowable values, in the case of (2) where the bed height operation stop deviation is increased and (3) where the operation start deviation is reduced, one operation is performed. As a result, the temperature drop width is reduced, and the steam temperature can be controlled within the lower limit.
[0023]
ADVANTAGE OF THE INVENTION According to this invention, the abnormal fall of the bed temperature or steam temperature at the time of bed height operation can be prevented, the stable operation of a plant can be maintained, or the time of stabilization operation can be shortened. FIG. 6 shows changes in bed height operation and bed temperature or steam temperature during load increase operation when the control method of the present invention is applied to a pressurized fluidized bed combined power generation system. Since the decrease range of the layer temperature is increased by the first layer height operation, the hysteresis width that determines the layer height operation width is corrected to be small, and the layer height operation width is decreased from the second time. As a result, a significant decrease in the layer temperature can be prevented, and there is no significant disturbance in the layer temperature or the steam temperature, and the layer temperature gradually increases. This effect makes it possible to control the steam temperature within an allowable range. In addition, as the load increases, the bed height increases, and as the bed temperature drop due to the same amount of BM input decreases, the bed height operation width increases one by one. Follow-up is also improved. Therefore, it becomes easy to operate the bed height while maintaining the plant stability condition.
[0024]
Next, as shown in FIGS. 1 to 4, as another embodiment of the present invention, a pressurized fluidized bed combined power generation system uses any one of the control methods of the pressurized fluidized bed combined power generation system, State temperature measurement and state temperature measured between the state temperature measurement at the start of the operation and the minimum state temperature measurement within a certain time after the layer height operation or between the layer height operation and the next layer height operation A control circuit that calculates the amount of temperature change between the set values, and when the amount of temperature change exceeds the preset maximum allowable change amount, the maximum or minimum value of the layer height deviation is changed to change the layer per time A control device having a control circuit for reducing a high operation amount is provided. The other operations and effects similar to those described above can also be obtained by other embodiments.
[0025]
【The invention's effect】
According to the present invention, when the bed temperature or the steam temperature is lower than the set value due to the bed height operation, the bed height operation width is corrected to be small. The track height is improved, and it becomes easy to operate the bed height while maintaining the stability condition of the system.
[Brief description of the drawings]
FIG. 1 is a diagram of a control circuit showing an embodiment of the present invention.
FIG. 2 is a diagram of a control circuit showing another embodiment of the present invention.
FIG. 3 is a control circuit diagram showing another embodiment of the present invention.
FIG. 4 is a diagram of a control circuit showing another embodiment of the present invention.
FIG. 5 is a diagram for explaining the layer height operation of the pressurized fluidized bed combined power generation system using the present invention.
FIG. 6 is a diagram illustrating an operating state of a pressurized fluidized bed combined power plant using the present invention.
FIG. 7 is a diagram showing an example of a pressurized fluidized bed combined power generation system.
FIG. 8 is a diagram illustrating an example of a conventional control circuit.
FIG. 9 is a diagram illustrating an operating state of a pressurized fluidized bed combined power generation system according to the prior art.
FIG. 10 is a diagram for explaining the bed height operation of the conventional pressurized fluidized bed combined power generation system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Function generator 2 Layer height set value 3 Layer temperature measuring device 4 Subtractor 5 Layer temperature deviation signal 6 Dead zone set device 7 Proportional integral controller 8 Adder 9 Layer height target value 10 Layer height measuring device 11 Subtractor 12 Layer height Deviation signal 13 Hysteresis generator 14 Layer height operation command 15 Fluid medium supply command 16 Fluid medium extraction command 17 Layer temperature change recording device 18 Minimum value determiner 19 Subtractor 20 Subtractor 21 Proportional integral controller 22 Layer height operation width command value 23 reset switch 24 storage unit 25 maximum value determination unit 26 steam temperature measurement unit 27 layer differential pressure measurement unit 28 furnace 29 pressure vessel 30 dispersion plate 31 combustion air nozzle 32 window box 33 heat transfer pipe 34 fluidized bed 35 fluidization medium vessel 36 fluidization medium Particle 37 Cyclone 38 Combustion exhaust gas 39 BM supply air valve 40 BM supply air 41 BM extraction air valve 42 BM extraction air 43 BM return air 44 BM return air 45 BM supply line 46 BM withdrawal line 47 fuel 48 compressor 49 gas turbine 50 air 51 generator 52 steam turbine 53 chimneys

Claims (3)

The bed height operation is started when the bed height deviation between the bed height target value and the bed height measurement value of the fluidized bed is equal to or greater than a predetermined maximum value, and when the bed height deviation is less than the minimum value, In a pressurized fluidized bed combined power generation system that drives a steam turbine and a gas turbine by controlling the state temperature consisting of the layer temperature or the steam temperature by the layer height operation, the state temperature and the layer at the start of the layer height operation A control circuit for obtaining a change amount between a state temperature measurement value and a state temperature set value between a minimum state temperature within a certain time after a high operation or after a layer height operation until the next layer height operation; and the change amount Provided with a control device having a control circuit for changing the maximum or minimum value of the layer height deviation to reduce the layer height operation width per time when the maximum allowable change amount set in advance is exceeded. A pressurized fluidized bed combined power generation system. The bed height operation is started when the bed height deviation between the bed height target value and the bed height measurement value of the fluidized bed is greater than or equal to a preset maximum value, and when the bed height deviation is less than the minimum value, In a control method of a pressurized fluidized bed combined power generation system for driving a steam turbine and a gas turbine by controlling a state temperature consisting of a layer temperature or a steam temperature by stopping the operation and controlling the state temperature, the measured value of the state temperature is Record the change over time, calculate the amount of temperature change between the state temperature at the start of layer height operation and the minimum state temperature within a certain time after layer height operation, and the temperature change amount exceeds the preset maximum allowable change amount A control method for a pressurized fluidized bed combined power generation system, wherein the maximum or minimum value of the bed height deviation is changed to reduce the bed height operation width per cycle. The bed height operation is started when the bed height deviation between the bed height target value and the bed height measurement value of the fluidized bed is equal to or greater than a predetermined maximum value, and when the bed height deviation is less than the minimum value, In a control method of a pressurized fluidized bed combined power generation system that drives a steam turbine and a gas turbine by controlling a state temperature consisting of a layer temperature or a steam temperature by stopping the operation, and controlling the measured value of the state temperature Record the change over time, store the maximum deviation between the state temperature measurement value and the state temperature setting value after the layer height operation until the next layer height operation, and when the maximum deviation exceeds the preset maximum allowable change amount A method for controlling a pressurized fluidized bed combined power generation system, wherein the maximum or minimum value of the bed height deviation is changed to reduce the bed height operation width per cycle.

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