JPH059681B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a method of operating a fluidized bed boiler when the load increases, and more specifically, a plurality of air/fuel systems are individually provided within the fluidized bed, and the present invention relates to a method of operating a fluidized bed boiler when the load increases. The present invention relates to an operating method for operating a cell that is desired to be activated in response to an increase in boiler load among layer regions (hereinafter referred to as cells) that are substantially divided into a plurality of layers.

In a fluidized bed boiler where the fluidized bed is divided into multiple cells and each cell has multiple supply air and fuel supply systems, when the load on the boiler is increased, the fluidized bed temperature also increases as the load increases. I will do it. In order to maintain stable combustion in such a boiler, there is an appropriate temperature range for the fluidized bed temperature. Therefore, if the load is increased while the cells that are already in operation are left in operation, the bed temperature will rise above the upper limit of the appropriate temperature range, making the boiler unusable.

By activating one of the plurality of supply air/fuel systems, one cell in the fluidized bed transitions from a fixed bed state to a fluidized bed state, and the material in the bed of the adjacent flowing cell is transferred to the fluidized bed state. As the bed temperature of the adjacent flowing cell mixes with the bed material and falls within the proper temperature range, the bed temperature of the starting cell rises to the ignition temperature of the fuel. By subsequently supplying fuel air, it becomes possible to further increase the boiler load.

However, in reality, when activating such a cell, the following problems occur, so that it has conventionally been impossible to activate the cell. In other words, when a stopped cell is simply started, the layer of the currently operating cell is mixed with the material in the layer of the currently operating cell and the layer of the currently operating cell. There is a risk of the fire extinguishing due to the temperature dropping. Furthermore, when the cell is suddenly activated, the amount of heat transfer increases, and therefore the steam pressure and steam temperature from the steam pipe increase rapidly. In other words, the quality of the steam deteriorates.

The purpose of the present invention is to solve the above-mentioned technical problems,
When the boiler load increases, it is possible to reliably ignite and operate the cell when starting the cell, and to maintain the quality of the steam flowing out from the steam pipe, that is, the steam pressure and temperature, in other words, to reduce the boiler load. An object of the present invention is to provide a method of operating a fluidized bed boiler when the load increases, which can improve follow-up performance.

In the present invention, among the cells 3 and 4 which are each region of the fluidized bed 2 divided into a plurality of regions, the already operated cell 3 has an air flow rate and a fuel flow rate that are supplied to optimal values so that the quality of steam is constant. The cell 4 that is about to start its operation is equipped with a plurality of temperature detectors 35 to detect the temperature, and the cell 4 that is about to start its operation generates an air flow rate and determines the quality of steam. The air flow rate is such that the air flow rate increases gradually so as not to decrease, the air supplied to the cell 4 that is about to start its operation does not disturb the flow state of the cell 3 that is already in operation, and the quality of the generated steam does not deteriorate. value V3,
The air flow rate of the cell 4 to be operated has reached the above-mentioned value V3 based on the state of dispersion in the detected temperature of each temperature detector 35 installed in the cell 4 to be operated. After that, the air flow rate is maintained at the value V3 until the ignition temperature is reached, and when the O ₂ concentration or NOx concentration of the combustion exhaust gas from the fluidized bed 2 is equal to or higher than a predetermined constant value α, the air ratio of the already operated cell 3 is to reduce the O ₂ concentration of the flue gas from the fluidized bed 2 or
When the NOx concentration becomes less than a predetermined constant value α, the time rate of change in layer temperature dT/dt detected by the temperature detector 34 provided in the already operating cell 3 increases by a certain negative value or more. When the starting operation is stopped, and when the time rate of change dT/dt is less than a certain negative value, the layer temperature detected by the temperature detector 35 of the cell 4 about to start operation is When the temperature remains below the fuel ignition temperature even after the predetermined time W required for the unburned content in the layer 2 to completely burn out,
Temperature detector 3 of cell 4 that has stopped the startup operation and is about to start operation
When the layer temperature detected by cell 5 becomes equal to or higher than the fuel ignition temperature within the predetermined temperature W, the cell 4 whose operation is to be started after the predetermined temperature W is completed. Fuel supply is started, the fuel supply flow rate is increased until it matches the air flow rate value V3, and after the start of fuel supply, the O ₂ concentration or NOx concentration of the combustion exhaust gas reaches the predetermined constant value α.
This method of operating a flow rate bed boiler when the load increases is characterized by returning the air ratio of the already operated cells 3 to the optimum value when the ratio becomes less than 1.

FIG. 1 is an overall system diagram of an embodiment of the present invention. The fluidized bed boiler 1 has a fluidized bed 2. The fluidized bed 2 consists of a bed material such as limestone, silica sand, etc. In this fluidized bed 2, cells 3 and 4 having two air/fuel systems are formed. In addition, as shown in the second figure, there is a partition wall 5 having a fluidized bed at least in the upper part.
It may be divided into a plurality of cells by.

Primary combustion air from an air supply means (not shown) is regulated by an air flow rate adjusting means 6 and supplied to the cell 3 from below the cell 3 through a flow path 7. Further, fuel, such as coal, from a fuel supply means (not shown) is supplied to the cell 3 from above or below the cell 3 via a flow path 9 while being regulated by a fuel flow rate regulating means 8 . As for the other cell 4, similarly to the cell 3, an air flow rate adjustment means 10 and a fuel flow rate adjustment means 12 are provided, and each adjustment means 10,
Air and fuel conditioned by 12 flow through channel 1
1 and flow path 13, respectively.

When air and fuel are supplied to the fluidized bed 2 in this manner, the fuel is combusted within the fluidized bed 2, and the combustion exhaust gas is discharged to the outside through the flow path 15.
The combustion energy of the fluidized bed 2 is absorbed by a fluid, such as steam, passing through the heat transfer tubes 16, and the heated steam passes through the flow path 17 and is supplied to a driving source such as a turbine.

The temperature of the steam passing through the flow path 17 is detected by a temperature detector 18, and a detection signal is sent to a control circuit 19.
will be sent to. A steam temperature setting signal 20 is input to the control circuit 19, and when the steam temperature is higher than the set value, a valve 21 is opened to supply water to an injection means 22 such as a sprayer. This injection means 2
2 injects water into the flow path 17 to cool the steam temperature. The flow rate of water injected from the injection means 22 is controlled by the control circuit 19 via the valve 21, so that the steam temperature can always be maintained at a constant value.

Further, the pressure and flow rate of steam passing through the flow path 17 are detected by a pressure detector 23 and a flow rate detector 24, and each detection signal is sent to a calculator 25. This calculator 25 calculates the flow rate of air and fuel supplied to the cells 3 and 4 in the normal mode. That is, the calculator 25 calculates the supply air flow rate and fuel flow rate corresponding to the signal from the flow rate detector 24 as the boiler load, and corrects the air flow rate and fuel flow rate in response to fluctuations in the signal from the pressure detector 23. calculate. In the normal mode, the calculation result from the calculation unit 25 is sent to the line 26, the activation calculation unit 27 of the cell 3, an air flow rate command signal is sent to the air flow rate adjustment means 6 via the line 28, and another signal is sent to the air flow rate adjustment means 6.
A fuel flow rate command signal is sent to the fuel flow rate adjusting means 8 via two lines 29. Flow rate adjustment means 6
Then, the air flow rate is adjusted and supplied to the cell 3 based on the air flow rate command signal, and the flow rate adjustment means 8 adjusts the fuel flow rate and supplied to the cell 3 based on the fuel flow rate command signal. Further, a signal from the computing unit 25 is sent to a cell activation computing unit 31 via a line 30, and an air flow rate command signal is further sent to the flow rate adjusting means 10 via a line 32. Also line 3
3, the fuel flow rate command signal is sent to the flow rate adjusting means 12.
will be sent to. Note that the computing unit 31 is a computing unit for computing the air/fuel flow rate for starting the cell 4. The air flow rate adjustment means 10 and the fuel flow rate adjustment means 12 adjust the air flow at a predetermined flow rate based on the signal.
Fuel is supplied to the cell 4.

Note that the cell activation computing units 27 and 31 send out signals having the same level as the signal from the computing unit 25 to the lines 28, 29, 32, and 33 in the above-mentioned normal mode.

The cell 3 is provided with a plurality of temperature detectors 34, and layer temperature detection signals from the temperature detectors 34 are sent to the activation calculator 27 of the cell 3. In addition, cell 4 also has a plurality of temperature detectors 35 similar to cell 3.
is provided, and the layer temperature detection signal is sent to the activation calculator 31 of the cell 4.

In the fluidized bed boiler 1 having such a configuration, in this embodiment, the cell 3 is in the operating state, and the cell 4 is in the operating state.
Assume that the is in a stopped state. In this case, when the startup calculator 31 of the cell 4 determines the start of cell startup based on the steam flow rate detection signal, the steam pressure detection signal, and the layer temperature detection signal of the cell 3, the calculation output of the calculator 25 in the normal mode Then, a new supply air flow rate command signal and a new supply fuel flow rate command signal are sent to the air flow rate adjustment means 10 and the fuel flow rate adjustment means 12 as calculation outputs of the startup computing unit 31, respectively, and the main operation is performed based on these sent signals. A predetermined air/fuel flow rate according to the method of the invention is regulated by flow rate regulating means 10, 12 and supplied to the cell 4. The same applies to the case where the cell 4 is in the operating state and the cell 3 is in the stopped state, and the cell 3 is also brought into the operating state.

The output of the temperature detector 34 is given to the starting calculator 31 via the starting calculator 27, and similarly, the output of the temperature detector 35 is given to the starting calculator 27 via the starting calculator 31. The signal lines for each of these outputs have been omitted in FIG. 1 for simplicity of illustration.

FIG. 3 is a graph showing the relationship between boiler load and bed temperature. When the load on the boiler is increased when the cell 4 is stopped and the cell 3 is in operation, the bed temperature increases from the lower limit T2 of the appropriate temperature range to the upper limit T1 as indicated by reference numeral 11. If the bed temperature exceeds the upper limit T1, the boiler will not be able to operate properly as described above, so the bed temperature will be lower than the upper limit T1.
When T1 is reached, cell 4 is operated according to the cell starting method according to the present invention, and the layer temperature is temporarily lowered to the lower limit value.
Descend to T2. Furthermore, by bringing the cells 3 and 4 into operation, it is possible to further increase the boiler load as indicated by reference numeral 12. In a fluidized bed boiler having a plurality of cells, it is possible to achieve a desired boiler load by sequentially activating the cells in this manner.

FIG. 4 is a flowchart of an operating method when the boiler load increases according to the present invention. Assume that the boiler load is increased from 50% to 100% as shown in Figure 3. For the sake of simplicity, it is assumed that the fluidized bed 2 is divided into cells 3 and 4 having the same volume.

When the flow rate detector 24 indicates that the steam flow rate has reached 70% as shown in the third figure while the cell 3 is in operation, activation of the cell 4 is initiated in accordance with the present invention. Note that while the cell 4 startup method according to the present invention is operated, the air/fuel flow rate is automatically controlled by the calculator 25 in the cell 3 in order to maintain the pressure and temperature of the generated steam at a constant value. The temperature is detected by the steam temperature detector 18 described above, and water is injected from the injection means 22 into the steam pipe 17 to lower the temperature and maintain the steam temperature at a constant value.

When the cell activation condition is satisfied in step n1,
The starting computing unit 31 of the cell 4 uses the output of the computing unit 25 in the normal mode as the starting computing output, and sends a new supply air flow rate command signal and a new supply flow rate command signal to the air flow rate adjusting means 10 and the fuel flow rate adjusting means 1.
Send to 2. First, the supply air is gradually increased. Note that the fuel is shut off by the flow rate regulating means 12.

In step n3, it is determined whether the air flow rate is V3. Here, V3 is the flow rate at which the flow state of the cell is not intense, that is, the state where there is less layer material from other flowing cells. As an indicator, it is 1 to 5 times, preferably 1.5 to 2.5 times, the air flow rate equivalent to the flow start speed, and in a flow state, the bed temperatures indicated by the plurality of detectors 35 are approximately the same value, and the bed material moves in the same way. However, at this purge air flow rate, the multiple thermometers 3 provided in the cell 4 to be operated exhibit separate movements.
The detected temperatures of 5 are different from each other and vary,
The purge air flow rate is determined based on the state of such variation in detected temperature. Let the value of this purge air flow rate be V3.

When the air flow rate is V3, step n4a
It is determined whether the O ₂ concentration or NOx concentration of the combustion exhaust gas is equal to or higher than a certain value α. Here, α is, for example, the pollution control concentration. If the O ₂ concentration or NOx concentration of the exhaust gas is equal to or higher than α, step n4b
The air ratio of cell 3 is decreased at . That is, the air ratio is decreased by changing the air flow rate relative to the fuel supply flow rate of the cell 3. If it is less than α in step n4a, the process moves to step n5, where the time rate of change dT/dt of the layer temperature of cell 3 is checked, and when dT/dt becomes greater than a certain negative value, that is, the negative absolute value When the value exceeds the certain value, step n
7, the supply of air to the cell 4 is stopped, and the startup operation is stopped. When the time rate of change dT/dt is not greater than the certain negative value, that is, when it is less than the certain negative value, the process moves from step n5 to step n6.

In step n6, it is determined whether the layer temperature of the cell 4 has reached the fuel ignition temperature, for example 450°C.
If the layer temperature of the cell 4 is less than the fuel ignition temperature, the process moves to step n8, and if the time W has elapsed, the starting operation is stopped in step n9. If the time W has not yet been completed, the process returns to step n4 again. Here, the time W is the time required for the unburned matter in the layer to be completely burned out, and is, for example, about 5 minutes.

In step n10, it is determined whether the time W has been completed or not, and if it is less than the time W, the process returns to step n4 again. If time W has been completed, step n11
At step n12, fuel supply to the cell 4 is started, and at step n12, the flow rate of fuel supplied to the cell 4 is increased until it matches the air flow rate V3. In addition, after starting to supply fuel to cell 4, the O ₂ concentration of exhaust gas or
When the NOx concentration becomes less than α, the air ratio of cell 3 is returned to the optimum value.

Thereafter, in step n13, the mode is switched to the normal mode, and the cell 4 is operated by the output of the arithmetic unit 25. In this way, the activation operation of the cell 4 is completed at step n14.

FIG. 5 is a response waveform diagram when the boiler load changes. As shown in Figure 5, the steam flow rate is increased from 50% to 100%.
When starting the stopped cell 4, the supply air flow rate is increased according to the broken line l in FIG.
When the pressure increases rapidly as shown by 1a, the steam pressure and steam temperature suddenly increase and fluctuate as shown by the broken line l4a in FIG. 52 and the broken line l5a in FIG. 53. In other words, the quality of the steam deteriorates.
Therefore, the air supplied to the cell 4 is gradually increased using the cell starting method according to the present invention described above, and the air supply to the cell 4 is gradually increased.
After completion, as shown in FIG. 5, by supplying fuel to the cell 4, the cell 4 gradually transitions from a fixed bed state to a fluidized bed state. Therefore, a sudden increase in the amount of heat transferred to the heat transfer tube 16 can be avoided, and the solid line l4 in FIG. 52 and the solid line l4 in FIG.
As shown by the solid line 15, it is possible to maintain the steam pressure and steam temperature at approximately constant values.

As described above, according to the present invention, the flow rate of air supplied to a cell to be activated is gradually increased to a constant flow rate value, that is, a flow rate at which the movement of layer material from other flowing cells is small. Then,
Since the fuel ignition temperature can rise above the fuel ignition temperature of the cell to be activated, it is possible to prevent misfire of the cell and ensure ignition. In addition, since the air supply to the cell was gradually increased during operation, the startup cell slowly transitioned from a fixed bed state to a fluidized bed state, and the amount of heat transferred to the intrabed heat transfer tubes increased rapidly. Therefore, fluctuations in steam pressure and temperature generated by the boiler can be reduced. In other words, deterioration of steam quality is prevented.

That is, in the present invention, among the cells 3 and 4 which are divided into a plurality of fluidized bed regions, in response to an increase in boiler load, the cell 4 that is stopped, that is, the cell 4 that is not being supplied with air and fuel, is Regarding the method for starting by supplying air and fuel, for the operating cell 3 adjacent to the cell 4 to be started, that is, the cell to which air and fuel are being supplied, as much as possible The purpose of supplying air to the cell 4 that is about to start up is to bring the bed into a fluidized state, rather than supplying air specifically for cooling. Due to this, the layer material of the adjacent operating cell 3 mixes with the layer material of the cell 4 to be activated, thereby increasing the layer temperature of the cell 4 to be activated. In this way, smooth activation of the cell 4 is possible.

In the present invention, a plurality of temperature detectors 35 are provided in the cell 4 that is about to start operation, and the temperature is detected, and based on the state of variation in the detected temperature, the cell 4 that is about to start operation is The flow rate of air to be supplied to the fluidized bed boiler is determined at a value that does not disturb the flow state of the cells that are already in operation and does not deteriorate the quality of the generated steam, thereby automating the operation when the load of the fluidized bed boiler increases. This will enable the process to be carried out smoothly.

Further, according to the present invention, the cell 4 that is about to start operation is provided with a plurality of temperature detectors 35, and based on the state of dispersion in the detected temperature of each of the temperature detectors 35, the cell 4 is The value V3 of the flow rate of air to be supplied is determined, and thus it becomes possible to automatically judge whether the state changes due to an increase in the air flow rate of the cell 4 that is about to start operation.

Further, according to the present invention, the air ratio of the already operating cell 3 is determined by the O ₂ concentration of the combustion exhaust gas from the flow layer 2 or
When the NOx concentration is above a predetermined constant value α,
When the time rate of change in layer temperature dT/dt detected by the temperature detector 34 installed in the already operating cell 3 increases by more than a certain value , stops the activation operation of the cell 4 to prevent the already operated cell 3 from extinguishing the fire.

Further, according to the present invention, in order to judge whether or not the cell 4 that is about to start operation has completed standby, the time rate of change dT/dt related to the already operating cell 3 is less than a certain negative value. , the temperature sensor 35 of the cell 4 that is about to start its operation
The layer temperature detected by
If the fuel ignition temperature remains below the fuel ignition temperature even after the elapse of time, the starting operation is stopped, and this predetermined time W is set as the time required for the unburned content in layer 2 to be completely burned out. If the layer temperature detected by the temperature detector 35 of the cell 4 that is about to start becomes equal to or higher than the fuel ignition temperature within the predetermined time W, then after the predetermined time W is completed, , starts supplying fuel to the cell 4 that is about to start its operation, and increases the fuel supply flow rate until it matches the air flow rate value V3. In this way, a so-called interlock for safe activation of the cell 4 is added, making it possible to start operation automatically.

Furthermore, after the fuel supply starts, the combustion exhaust gas
When the O ₂ concentration or NOx concentration becomes less than the predetermined constant value α, the air ratio of the already operated cell 3 is returned to the optimum value, thus making it possible to continue stable operation.

[Brief explanation of the drawing]

FIG. 1 is an overall system diagram of an embodiment of the present invention, FIG. 2 is a simplified diagram of another embodiment of the fluidized bed boiler 1, and FIG. 3 is a graph showing the relationship between boiler load and bed temperature.
FIG. 4 is a flowchart showing an operating method when the boiler load increases according to the present invention, and FIG. 5 is a response waveform diagram when the boiler load changes. DESCRIPTION OF SYMBOLS 1... Fluidized bed boiler, 2... Fluidized bed, 3, 4... Cell, 6, 10... Air flow rate adjustment means, 8, 12... Fuel flow rate adjustment means, 18... Steam temperature detector, 23...
Steam pressure detector, 24... Steam flow rate detector, 34,
35... Layer temperature detector.

Claims (1)

[Scope of Claims] 1 Among the cells 3 and 4 which are each area of the fluidized bed 2 divided into a plurality of parts, the air flow rate supplied to the cell 3 that is already in operation is the highest value so that the quality of steam is constant. The cell 4 that is about to start operation is equipped with a plurality of temperature detectors 35 to detect the temperature, and the cell 4 that is about to start operation is controlled automatically to generate an air flow rate. The air is gradually increased so that the quality of the steam does not deteriorate, the air supplied to the cell 4 that is about to start its operation does not disturb the flow state of the cell 3 that is already in operation, and the quality of the generated steam does not deteriorate. The value of air flow rate V3,
The air flow rate of the cell 4 to be operated has reached the above-mentioned value V3 based on the state of dispersion in the detected temperature of each temperature detector 35 installed in the cell 4 to be operated. After that, the air flow rate is maintained at the value V3 until the ignition temperature is reached, and when the O ₂ concentration or NOx concentration of the combustion exhaust gas from the fluidized bed 2 is equal to or higher than a predetermined constant value α, the air ratio of the already operated cell 3 is to reduce the O ₂ concentration of the flue gas from the fluidized bed 2 or
When the NOx concentration becomes less than a predetermined constant value α, the time rate of change in layer temperature dT/dt detected by the temperature detector 34 provided in the already operating cell 3 increases by a certain negative value or more. When the starting operation is stopped, and when the time rate of change dT/dt is less than a certain negative value, the layer temperature detected by the temperature detector 35 of the cell 4 about to start operation is When the temperature remains below the fuel ignition temperature even after the predetermined time W required for the unburned content in the layer 2 to completely burn out,
Temperature detector 3 of cell 4 that has stopped the startup operation and is about to start operation
When the layer temperature detected by cell 5 becomes equal to or higher than the fuel ignition temperature within the predetermined temperature W, the cell 4 whose operation is to be started after the predetermined temperature W is completed. Fuel supply is started, the fuel supply flow rate is increased until it matches the air flow rate value V3, and after the start of fuel supply, the O ₂ concentration or NOx concentration of the combustion exhaust gas reaches the predetermined constant value α.
A method for operating a fluidized bed boiler when the load increases, the method comprising: returning the air ratio of the already operated cells 3 to the optimum value when the air ratio becomes lower than the optimum value.