JP4642630B2 - Gas turbine control system and control method - Google Patents

Description

  The present invention relates to a control system and a control method for a gas turbine. More specifically, in a gas turbine power generation facility, when a sudden load drop such as a load interruption occurs, the heat input to the gas turbine is quickly controlled to prevent the gas turbine from exceeding a predetermined rotational speed. The present invention relates to a gas turbine control system and a gas turbine control method.

  In the steelmaking field, for example, when pig iron is produced by the blast furnace method, the top gas (Blast Furnace Gas, referred to as BFG) is generated from the blast furnace as a low calorie by-product gas. In recent years, in gas turbines, combustion of a low-calorie by-product gas such as this BFG has become possible due to technical improvements, and there are an increasing number of cases where electricity is generated using gas turbine fuel. On the other hand, in addition to the blast furnace method, new iron making processes such as a direct reduced iron method and a smelted reduced iron method have been developed, and by-product gas is also generated from these new processes. In any steelmaking process, the by-product gas generated is a so-called low calorie gas, and its characteristics (gas composition and calorie) vary depending on the equipment and operation contents. Even in the same facility, it changes from moment to moment according to the characteristics of each raw material and the reaction process, and does not become constant. The development of a combustion method that can be applied to such effective utilization of by-product gas is awaited.

  Not only gas turbine power generation equipment that uses low-calorie by-product gas (hereinafter referred to as low-calorie gas) with varying caloric values as fuel, but also gas turbine power generation equipment that uses normal fuel such as natural gas. When a situation such as a sudden drop in the load occurs, it is necessary to control the gas turbine so as to suppress the overspeed (excessive increase in the rotational speed) and maintain the necessary minimum output without tripping. For example, when the gas turbine is operating at the rated load, when the load is interrupted due to some cause in the power transmission system or the gas turbine power generation facility and the line is disconnected from the load, the gas turbine immediately falls into an overspeed state. When this is detected by the control device, the opening of the flow control valve of the fuel supply system is rapidly reduced to suppress overspeed of the gas turbine. The detection of load interruption is performed by inputting an output signal of a generator, a rotation speed signal of a gas turbine, or the like.

  Then, the flow rate control valve is closed until the opening degree at which the necessary minimum flow rate of fuel for maintaining the rated rotational speed is maintained in the no-load state while avoiding misfire of the combustor. The opening degree control of the flow rate control valve is performed while monitoring operation state quantities such as the gas turbine rotation speed, the generator output, the exhaust temperature of the gas turbine, the inlet pressure and the outlet pressure of the air compressor. Such control at the time of load interruption is disclosed in many documents (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3).

  In addition, depending on the type of gas turbine, means for opening the inlet guide vanes of the gas turbine when the load suddenly drops is also used, thereby increasing the compressor driving power and increasing the braking effect of the rotating shaft, Some control overspeed.

  However, in a gas turbine power generation facility that uses the above low calorie gas as a fuel, it is not easy to control the operation when the load suddenly drops. In order to increase the supply amount to the gas turbine because the fuel gas is low in calorie, a large-diameter fuel gas supply pipe is used. As a result, the diameter of the flow control valve also increases, so that the opening / closing stroke increases and a long time is required for closing the valve. Therefore, it becomes difficult to rapidly reduce the amount of heat input to the gas turbine simultaneously with the occurrence of load interruption, and effective overspeed suppression of the gas turbine cannot be expected.

  In addition, as described above, the calorific value of the low calorie gas fluctuates from moment to moment. Therefore, when the control gain of the flow rate control valve is increased (increased responsiveness), the flow rate control valve reacts sensitively to disturbance of calorie fluctuation. Hunting may occur. In order to avoid such a situation, the control gain is set so that the responsiveness of the flow control valve is lowered. This further hinders the rapid closing operation of the flow control valve, which makes it difficult to rapidly reduce the heat input to the gas turbine.

  In a gas turbine power generation facility using low calorie gas as a fuel, a fuel compressor for compressing low calorie gas is installed in a fuel gas supply passage. In many cases, this fuel compressor is coaxially connected to the gas turbine. In this case, the moment of inertia of the entire rotating body of the generator train constituted by the gas turbine, the fuel compressor, and the generator is large. Moreover, since the engine is in an overspeed state due to the load interruption, rapid braking cannot be expected even if the flow regulating valve of the fuel supply line to the gas turbine is started simultaneously with the load interruption. It is difficult to suppress the increase in the rotational speed of the generator train including

In commercial gas turbine power generation facilities, it is possible to confirm by a load interruption test that the governor functions so that the gas turbine does not exceed 110% of the rated speed during load operation when load interruption occurs. It is obligatory. And operation is permitted after the function of a speed governor is confirmed. For this reason, in gas turbine power generation facilities that use natural gas or other fuel that has a high caloric value as a fuel, equipment configuration aspects and controls for preventing overspeed of the gas turbine at the time of load interruption and not exceeding the specified range This is dealt with by making various improvements on the surface. Such a device has not yet been able to effectively suppress overspeed of the gas turbine at the time of load interruption in a gas turbine power generation facility using low calorie gas that constantly fluctuates in calories.
JP-A-8-165934 JP 2002-138856 A JP 2002-227610 A

  The present invention has been made to solve such a problem, and when a sudden drop in load such as load interruption occurs in a gas turbine power generation facility, the facility uses low calorie gas as fuel. However, an object of the present invention is to provide a gas turbine control system that can easily suppress an increase in the rotational speed of the gas turbine, and to provide a control method for such a gas turbine.

The gas turbine control system of the present invention includes:
A gas turbine control system that suppresses an increase in the rotational speed of a gas turbine when the load of the gas turbine suddenly drops,
A fuel flow control valve for adjusting the flow rate of the fuel gas, disposed in a fuel gas supply passage for supplying the fuel gas to the gas turbine;
A heat reducing gas supply device for supplying heat reducing gas to the fuel gas supply passage;
A system controller,
When this system controller detects a sudden drop in the load of the gas turbine, in order to reduce the amount of heat input to the gas turbine, in addition to the opening control of the fuel flow control valve, the heat reduction by the heat reducing gas supply device It is comprised so that the operation gas supply operation may be controlled.

  Thus, in order to reduce the amount of heat input to the gas turbine when the gas turbine load suddenly drops, in addition to controlling the opening of the fuel flow control valve, the supply of heat reduction gas to the fuel is also performed. Even if low calorie gas is used, the increase in the rotational speed of the gas turbine can be effectively suppressed.

  The system controller closes the fuel flow control valve to an opening that does not fall below a predetermined minimum opening when the load of the operating gas turbine is rapidly reduced to a predetermined value (for example, approximately in a stepped manner). It is possible to control the gas turbine so that the heat-reduction gas necessary for the rotation speed of the gas turbine not to exceed a predetermined value is supplied from the heat-reduction gas supply device.

  In this way, by adding the heat reducing gas to the fuel, the amount of heat input is reduced while the minimum fuel flow rate necessary to prevent the gas turbine from tripping is prevented, and the increase in the rotational speed of the gas turbine is suppressed. The predetermined number of rotations can be prevented from exceeding.

  The system controller uses the detected rotation speed of the gas turbine as a feedback input signal, and controls the supply amount of the heat reduction gas from the heat reduction gas supply apparatus so that the rotation speed of the gas turbine does not exceed a predetermined value. Feedback control can be performed.

In the above system controller, after the event of the process in which the load of the operating gas turbine rapidly decreases to a predetermined value is modeled, the heat reduction gas supply control and the fuel flow rate control valve performed along this model are modeled. Stores the simulation results of opening control,
The system control device can be configured to select and execute a preset control mode based on the simulation result when the load of the operating gas turbine rapidly decreases to a predetermined value.

  The gas turbine control system further comprises a hydrogen gas supply device for supplying hydrogen gas to the fuel gas supply passage, and a hydrogen concentration detection device for detecting the hydrogen concentration in the fuel gas, the system control device comprising: The hydrogen gas supply operation by the hydrogen gas supply device can be controlled based on the detection result of the hydrogen concentration.

  Even when the gas turbine load plummets, even if the heat input to the gas turbine is rapidly reduced, misfiring of the gas turbine is achieved by supplying the fuel gas with the necessary amount of hydrogen gas that has a fast combustion speed and good flame holding properties. Thus, stable combustion can be maintained in the combustor. The purity of the hydrogen gas to be supplied is not particularly limited. However, the higher the purity, the better the ignition and flame holding properties.

The gas turbine control method of the present invention includes:
A gas turbine control method for suppressing an increase in the rotational speed of a gas turbine when the load of the gas turbine suddenly drops,
When a sudden drop in the load on the gas turbine is detected,
Adjusting the flow rate of the fuel gas by controlling the opening of the fuel flow control valve disposed in the fuel gas supply passage for supplying the fuel gas to the gas turbine;
Supplying a heat reduction gas to the fuel gas supply passage,
These steps are executed to reduce the amount of heat input to the gas turbine.

When the load of the operating gas turbine drops rapidly to a predetermined value (for example, almost stepwise)
In the fuel flow rate adjustment step, the fuel flow rate control valve is closed to an opening degree that does not fall below a predetermined minimum opening degree to reduce the fuel flow rate,
In the heat reduction gas supply step, the heat reduction gas necessary for the rotation speed of the gas turbine not to exceed a predetermined value can be supplied to the fuel gas supply passage.

  The required minimum opening is a valve opening for securing a fuel flow rate necessary for maintaining stable combustion of the gas turbine.

  ADVANTAGE OF THE INVENTION According to this invention, when load drop, such as load interruption | blocking, generate | occur | produces in gas turbine power generation equipment, the raise of the rotation speed of a gas turbine can be suppressed rapidly and effectively.

  Embodiments of a gas turbine control system and a gas turbine control method of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a system diagram schematically showing a gas turbine power generation facility 1 including an embodiment of a gas turbine control system of the present invention. As an example, the gas turbine power generation facility 1 (hereinafter also simply referred to as the power generation facility 1) uses, as an example, low calorie by-product gas (low calorie gas) in which the calorie value generated in the gas generation source S such as direct reduced iron facility continuously fluctuates. A fuel gas supply pipe 3 for supplying fuel to the gas turbine 2, a fuel compressor 4 for compressing low calorie gas, and a heat reduction gas supply device 5 for supplying heat reduction gas to the fuel gas supply pipe 3. And a hydrogen gas supply device 6 for supplying hydrogen gas to the fuel gas supply pipe 3, and a mixer 7 for mixing the supplied heat reduction gas and hydrogen gas with low calorie gas, respectively. The mixer 7 may be provided separately for mixing the heat reducing gas and for mixing the hydrogen gas. Moreover, you may install apparatuses, such as a buffer tank for suppressing the calorie fluctuation | variation of low calorie gas, on the fuel gas supply piping 3 as needed.

  In this power generation facility 1, heat reduction gas and hydrogen gas supply sources 15 and 19 having a pressure higher than that of the low calorie gas supplied as fuel gas are installed. The apparatus 6 and the mixer 7 are installed on the downstream side of the fuel compressor 4 in the fuel gas supply pipe 3. The fuel compressor 4 may be coaxially connected to the gas turbine 2 and driven by the gas turbine 2. Alternatively, the fuel compressor 4 may be separated from the gas turbine 2 and driven by a separately provided motor. You may comprise as follows.

Further, a system control device 10 is installed for controlling the operation of the gas turbine when a sudden drop in load such as load interruption occurs as well as normal operation of the gas turbine power generation facility 1. A fuel flow rate control valve (hereinafter also simply referred to as a control valve) 9 is installed upstream of the gas turbine combustor 8 in the fuel gas supply pipe 3. Reference numeral 11 denotes an air compressor, and reference numeral 12 denotes a generator. A hydrogen concentration meter 13 for measuring the hydrogen concentration in the fuel gas and a fuel flow meter 14 for measuring the flow rate of the low calorie gas are installed upstream of the mixer 7 in the fuel gas supply pipe 3. As the purity of hydrogen gas increases, the ignition flame holding property is good even with a small amount, but in practice, the hydrogen gas to be supplied does not need to be pure hydrogen. Here, the low calorie gas is defined as a gas having a calorific value of about 12 MJ / Nm ³ or less.

  The heat reducing gas supply device 5 is a gas for reducing heat to low calorie gas for the purpose of rapidly reducing the amount of heat input to the gas turbine 2 when a load drop such as a load interruption occurs in the gas turbine power generation facility 1. It is installed to mix. The heat reduction gas supply device 5 includes a heat reduction gas supply source 15, a heat reduction gas supply pipe 16 connected from the heat reduction gas supply source 15 to the mixer 7, and a heat reduction gas supply pipe. 16 has a heat reduction gas flow meter 17 and a flow control valve 18 installed at 16. The pressure of the heat reducing gas at the stage of entering the mixer 7 is higher than the pressure of the low calorie gas so that the necessary amount can be supplied quickly. For this purpose, a booster, a pressure accumulating container, or the like may be installed as necessary. Control of the heat reduction gas supply device 5 for supplying the heat reduction gas when the load suddenly drops is performed by the system control device 10 while controlling the fuel flow rate control valve 9 in the valve closing direction. This point will be described later.

  As the heat reducing gas, waste nitrogen, inert gas such as helium or carbon dioxide, air, combustion exhaust gas, or the like can be used. The air can be used by sucking inexhaustible air as it is, and the combustion exhaust gas is also generated in the gas turbine 2 so that it can be recovered and used, for example. Become. When using oxygen-containing gas such as air or combustion exhaust gas, after mixing this heat reducing gas with low calorie gas, monitor the oxygen concentration so that this mixed gas (fuel gas) does not enter the flammable limit. Control while driving.

Waste nitrogen contains a large amount of N ₂ but does not contain combustible gases. Waste nitrogen is generated as a by-product from oxygen production plants used in various steelmaking processes, and is released from the nitrogen that is released and nitrogen produced at the nitrogen production plant attached to the oxygen production plant. Nitrogen containing trace amounts of nitrogen. Any nitrogen is usually released to the atmosphere as waste nitrogen. Such waste nitrogen has a gas composition of about 95 to 98% nitrogen gas and about 2 to 5% oxygen, and is a safe heat reducing gas from the viewpoint of low calorific gas flammability limit. . If these large amounts of discarded nitrogen are recovered and used as a heat reducing gas, the operation cost is extremely low.

  In addition, if the gas is lower in calorie than the fuel gas, it can be used as a heat reducing gas. For example, when using coke oven gas (COG) or converter gas (LDG) as the fuel gas, It is also possible to employ a low calorie blast furnace gas (BFG) as a heat reducing gas. However, it is preferable to use waste nitrogen or the like having a very low combustible component content because the heat reduction effect is much greater. In addition to the gas described above, water vapor can be employed as the heat reducing gas.

  During normal operation of the power generation facility 1, the system control device 10 uses, for example, the output value of the generator 12, the rotation speed of the gas turbine 2, the inlet / outlet pressure of the air compressor 11, the exhaust temperature of the gas turbine 2, and the like as input signals. The opening degree of the fuel flow control valve 9 is controlled so that the gas turbine heat input according to the fluctuation is performed.

  Moreover, the caloric value of the low calorie gas as the fuel fluctuates as described above. In order to maintain a stable heat input to the gas turbine even with respect to the calorie fluctuation, the system control apparatus 10 may control the opening of the fuel flow control valve 9 by appropriate feedforward control or feedback control. However, if the fuel flow control valve 9 is opened or closed in response to a change in the calorie value or a change in the generator output, the fuel flow control valve 9 may cause hunting along with a slight change in calorie. The control gain cannot be increased. That is, when low calorie gas is used, the responsiveness of the fuel flow control valve 9 cannot be increased, and the control gain is usually set small. Further, since the fuel gas supply pipe 3 for supplying the low calorie gas has a large pipe diameter, the fuel flow control valve 9 has to have a large diameter.

  For this reason, a rapid opening / closing operation of the fuel flow control valve 9 cannot be expected even when it is desired to instantaneously reduce the amount of heat input to the gas turbine when the load is interrupted. Therefore, in the power generation facility 1, the system control device 10 effectively controls the amount of heat input to the gas turbine 2 by mixing the heat reducing gas with the fuel gas in addition to the opening / closing operation of the fuel flow control valve 9. .

  Further, in order to reduce the amount of heat input to the gas turbine, the valve opening degree must be made very small in order to cope with only the narrowing of the fuel flow control valve 9 as in the prior art. In this case, backfire or the like may occur in the combustor due to insufficient fuel flow, and combustion may become unstable. However, since the power generation facility 1 controls the amount of heat input also with the heat reducing gas as described above, the fuel flow control valve 9 can be set to an opening degree that secures a necessary minimum flow rate for stable combustion. Thus, due to the synergistic effect of narrowing the fuel flow control valve 9 and mixing the heat reducing gas, the gas turbine heat input can be stably and quickly changed from the rated load operation state to the rated no load operation state without tripping the gas turbine. Can be migrated to.

  The fuel flow control valve 9 is closed while supplying the heat reducing gas, but the valve closing operation is stopped when the required minimum opening is reached. Even in this case, if it is necessary to further reduce the amount of heat input, the supply of the heat reducing gas can be continued within a range that does not fall below the misfire limit.

  With reference to FIG. 2, the control of the fuel flow rate control valve 9 at the time of load interruption of the power generation facility 1 described above, the control of the heat reduction gas supply device 5, and the change in the gas turbine rotation speed due to them will be described. .

  When a load interruption occurs, the gas turbine is momentarily disconnected from the load, but the amount of heat input that has been supplied to maintain rated operation until then cannot be reduced instantaneously. The extra heat input generates acceleration torque, which accelerates the gas turbine and increases the rotational speed. Even in such a case, the amount of heat input must be rapidly reduced so that the rotational speed of the gas turbine does not exceed the allowable maximum rotational speed Rmax.

  FIG. 2A shows a change in the load of the gas turbine 2 when the load is interrupted. The horizontal axis indicates time, the vertical axis indicates the gas turbine load (%), 100% rated load operation is performed until the load is interrupted, and 0% after the load is interrupted.

  FIG. 2B shows a change in the opening degree of the fuel flow control valve 9 when the load of the gas turbine 2 is interrupted. The horizontal axis represents time so as to correspond to FIG. The vertical axis indicates the opening degree (%) of the control valve, but it may be equated with the fuel flow rate. Until the load is cut off, the rated opening (100%) ODrat. Of the control valve 9, that is, the fuel flow rate (FIG. 2 (c)) enabling the rated heat input HIrat. Operation is performed at the rated fuel flow rate (Qrat.). After the load is cut off, the control valve 9 is closed to a small opening (referred to as a necessary minimum opening) ODmin. At which the fuel flow rate becomes a necessary minimum flow rate (Qmin.) That can maintain the no-load rated rotational speed of the gas turbine. The necessary minimum flow rate Qmin. Is set in order to ensure the flow rate of the fuel gas in a range in which so-called backfire does not occur in the combustor 8, and to ensure the necessary minimum heat input amount HImin. That does not reach the misfire limit described later. The fuel flow rate.

  A dashed-dotted line curve B1 in FIG. 2 (b) reduces the gas turbine heat input so that the gas turbine rotational speed does not exceed the allowable maximum value Rmax. (FIG. 2 (e)) when load interruption occurs. Therefore, it is a valve closing curve necessary for this, and a fuel flow rate decrease curve. This is called an ideal curve B1. On the other hand, a curve B2 indicated by a solid line is an actual valve closing curve of the control valve 9 in the present embodiment. As described above, this indicates that the valve diameter of the control valve 9 is large and that the control gain is set to be small, so that rapid valve closing cannot be performed.

  2 (c) and 2 (d) show changes in heat input per unit time to the gas turbine when the load is interrupted. FIG. 2 (c) shows a decrease in heat input due to only the valve closing operation of the control valve 9, and FIG. 2 (d) shows a decrease in heat input due to the valve closing operation of the control valve 9 and the supply of heat reducing gas. Yes. The horizontal axis represents time so as to correspond to FIG. The vertical axis represents the amount of heat input to the gas turbine per unit time. Until the load is interrupted, the gas turbine 2 is operated with the rated heat input HIrat., And after the load is interrupted, the gas turbine 2 is operated with the heat input within a range that does not decrease to the misfire limit of the gas turbine.

  A dashed-dotted line curve C1 in FIG. 2 (c) shows that the amount of heat input to the gas turbine decreases when the valve is closed along the ideal valve closing curve B1 (FIG. 2 (b)). Yes. This is a reduction curve of the amount of heat input to the gas turbine that is necessary so that the gas turbine rotational speed does not exceed the allowable maximum value Rmax. (FIG. 2 (e)) when load interruption occurs. This is called an ideal curve C1. On the other hand, a curve C2 indicated by a solid line is a decrease curve of the actual heat input amount that accompanies the closing of the control valve 9 that cannot be rapidly closed.

  The dashed-dotted curve D2 in FIG. 2D shows the same curve as the actual heat input decrease curve C2 in FIG. On the other hand, the solid curve D1 closes the control valve 9 along the actual valve closing curve B2 in FIG. 2B and supplies the heat reducing gas from the heat reducing gas supply device 5 to the fuel gas. This is a curve when the amount of heat input to the gas turbine 2 is rapidly reduced. This is a curve showing an example of control in the present embodiment.

  Looking at the curve D1, compared to the heat input decrease curve D2 only by closing the control valve 9, the decrease rate is large and the minimum value of the heat input is also low (undershoot from the point d1 to the point d2). ) This occurs when the control gain of the heat reduction gas supply is set so as to coincide with the ideal heat input amount decrease curve C1 in FIG. This undershoot improves the effect of suppressing the increase in the rotational speed of the gas turbine. Of course, in this case, the required minimum heat input (misfire limit) HImin., Which is set to prevent misfire of the gas turbine 2, is not reduced. From the above, it can be seen that the hatched portion surrounded by the curves C1 and C2 is the amount of heat input that is reduced by the supply of the heat reducing gas.

  FIG. 2 (e) shows changes in the rotational speed of the gas turbine under the heat input control shown in FIGS. 2 (c) and 2 (d). The horizontal axis shows time so as to correspond to FIG. 2 (c) and FIG. 2 (d). The vertical axis indicates the gas turbine rotational speed, and the percentage of rotational speed with the rated rotational speed Rrat. During rated load operation as 100%.

  A curve E2 in the figure shows a case where the gas turbine rotational speed after load interruption exceeds the allowable maximum rotational speed (a value of 110% of the rated rotational speed) Rmax. Without being effectively suppressed. As described with reference to the curve B2 in FIG. 2 (b), the gas turbine heat input amount is appropriately reduced because the control valve 9 cannot be rapidly closed due to the aperture or the gain setting. If this is not done (curve C2 in FIG. 2 (c) and curve D2 in FIG. 2 (d)). On the other hand, the curve E1 combines the supply of the heat reducing gas shown in FIG. 2 (d) to rapidly reduce the heat input to the gas turbine 2 along the curve D1, and to appropriately increase the rotational speed. The case where suppression was made is shown. In this case, the gas turbine rotational speed does not exceed the allowable maximum rotational speed Rmax.

  As described above, as shown in FIG. 2A to FIG. 2E, the load on the gas turbine 2 is stepped from the point A1 which is 100% to the point A2 where the load is 0% in FIG. The system control apparatus 10 in the present embodiment closes to the required minimum opening ODmin. Of the control valve 9 in order to suppress a rapid increase in the rotational speed of the gas turbine 2 (curve B2 in FIG. 2B). In addition, the heat reduction gas is supplied from the heat reduction gas supply device 5 to the fuel gas. Then, the amount of heat input to the gas turbine 2 rapidly decreases (curve D1 in FIG. 2 (d)). As a result, the gas turbine that has been decoupled from the load and has started to rapidly increase in rotational speed is prevented from exceeding the allowable maximum rotational speed Rmax. By the braking effect resulting from the reduced heat input, and the rated rotational speed Rrat. It is decelerated to the vicinity (curve E1 in FIG. 2 (e)).

  As means for detecting that the load of the gas turbine 2 has dropped suddenly by the system control device 10, for example, a conventionally known technique called power load imbalance detection can be used. Of course, it is not limited to such a method. If possible, a sudden drop in the load may be detected from a rotational speed signal of the gas turbine, an outlet pressure signal of the fuel compressor, a cutoff signal from the load circuit breaker, or the like.

  Then, when the system controller 10 controls the valve closing operation of the control valve 9 and the operation of the heat reducing gas supply device 5 after detecting the sudden drop in the load, the actual rotational speed Rrad. The turbine speed can be fed back and controlled. In addition, other gas turbine operating state quantities may be fed back and controlled. It is also possible to simulate gas supply control for heat reduction and valve closing control of a control valve that model an event after a sudden drop in load from the rated load operation of the gas turbine. Data relating to the opening degree of the control valve at the time of sudden load drop and the supply amount and supply timing of the heat reducing gas corresponding to the opening degree obtained from the simulation result are preset in the control device 10. The preset data can be selected and executed when the actual load suddenly drops. Further, actual data (including data at the time of load interruption) obtained through actual operation may be used by replacing part or all of simulation data. That is, the preset data of the simulation result may be used after being corrected with the actual operation data.

  As described above, the system control device 10 stores the program and preset data for performing the arithmetic processing necessary for the control, and the RAM and the program for temporarily storing data and numerical values during operation are stored in the system control device 10. CPU which performs the arithmetic processing along is equipped.

  As described above, the system control device 10 controls the entire operation of the gas turbine operation. That is, the system control device 10 is responsible for each operation mode such as start-up (including start-up preparation, purging, ignition, synchronous input, cold start, warm start), rated load operation, partial load operation, stop, cool down, load cut-off, etc. To do. The description of modes other than load shedding is omitted here. Particularly in the load cutoff mode, in addition to the operation control of the fuel flow rate control valve 9 and the control of other control objects, the present gas turbine realizes a rapid decrease in the heat input by mixing the fuel gas with a heat reducing gas. This is a feature of the control system.

  When the load cut-off occurs and the operation mode of the system control device 10 is changed to the load cut-off mode, the system control device 10 instructs the heat-reduction gas supply device 5 on the necessary supply flow rate and supply time of the heat-reduction gas. . The required supply flow rate and supply time are stored as preset data. At this time, for example, the opening / closing operation of the flow rate control valve 18 may be controlled so that the measurement result of the heat reduction gas flow meter 17 becomes the target supply flow rate using the measurement result as a feedback signal. Considering that it is necessary to supply a predetermined amount of heat reduction gas in a short time, the diameters of the heat reduction gas supply pipe 16 and the flow rate control valve 18 may be reduced to increase the number of installations and the number of installations.

  Next, the hydrogen gas supply device 6 will be described. Since hydrogen gas has a high combustion speed and good ignition flame holding properties, it contributes to maintaining stable combustion even when the amount of heat input to the gas turbine is greatly reduced. Therefore, the hydrogen gas supply device 6 is installed to hold a flame in the combustor 8 of the gas turbine 2 by mixing hydrogen gas in the fuel gas. Therefore, this hydrogen gas supply device 6 is useful for preventing a gas turbine misfire due to a decrease in heat input when the load suddenly drops. The hydrogen gas supply device 6 includes a hydrogen gas supply source 19, a hydrogen gas supply pipe 20 connected from the hydrogen gas supply source 19 to the mixer 7, a hydrogen gas flow meter 21 installed in the hydrogen gas supply pipe 20, and A flow control valve 22. When high purity hydrogen gas that is not pure hydrogen is used as the hydrogen gas, a hydrogen concentration meter (not shown) is installed in the hydrogen gas supply pipe 20.

  The system control device 10 controls the supply of hydrogen gas as follows when the calorie value and flow rate of the fuel gas supplied to the gas turbine 2 are rapidly reduced when the gas turbine load suddenly drops. That is, the detection result of the hydrogen concentration meter 13 of the fuel gas supply pipe 3 so as to maintain the hydrogen gas necessary content ratio of the fuel gas in the combustor 8 that is predetermined for holding the flame, A necessary supply amount of hydrogen gas is calculated from the mixing ratio, the flow rate of the fuel gas detected by the fuel flow meter 14, and the like. The opening / closing operation of the flow control valve 22 is controlled while monitoring the hydrogen gas flow meter 21. The supplied hydrogen gas is mixed with the low calorie gas by the mixer 7.

  FIG. 3 shows another gas turbine power generation facility 31. In this power generation facility 31, a relatively low-pressure heat-reduction gas supply source 15 and a hydrogen gas supply source 19 are installed, so that the heat-reduction gas supply device 5, the hydrogen gas supply device 6, and the mixer 7 are fuel gas. It is installed upstream of the fuel compressor 4 in the supply pipe 3. Since the other structure is the same as the power generation equipment 1 shown in FIG. 1, the same code | symbol is attached | subjected to the same structure part and the description is abbreviate | omitted. Also in this gas turbine power generation facility 31, the system control device 10 performs the same control as in the power generation facility 1 of FIG.

  In the embodiment described above, the by-product gas generated by the direct reduction iron manufacturing method is exemplified as the low calorie gas to be used. However, the present invention is not limited to this. Low calorie gas includes blast furnace gas (BFG), converter gas (LDG), coal bed gas (Coal mine gas, expressed as CMG), by-product gas generated by smelting reduction iron making process, GTL (Gas-to-Liquid) process generated tail gas, by-product gas generated from oil sands during the oil refining process, gas generated by pyrolyzing garbage, general waste containing garbage However, combustible methane gas (Landfill gas) generated in the process of fermentation and decomposition in the landfill, and low calorie gas such as by-product gas generated by chemically reacting other similar raw materials are included. Of course, the gas includes not only the gas alone but also a gas obtained by mixing a plurality of different gases. Further, the present invention can be applied not only to low calorie gas but also to facilities for supplying a gas whose calorie value varies as a gas turbine fuel.

  Depending on the characteristics of the fuel gas, especially when caloric fluctuations are significant, a buffer tank that suppresses caloric fluctuations or a calorie fluctuation suppressing device employing a control mechanism may be provided to enhance the control effect at the time of load interruption.

  In the gas turbine control system described above, the gas turbine fuel gas is low calorie gas. However, the gas turbine control system is not limited to this, and high gas calorie gas may be used as fuel. When high calorie gas is used as a fuel, it is generally easy to control the amount of heat input to the gas turbine using the fuel flow control valve even when the gas turbine load drops sharply. This is because when using high-calorie gas such as natural gas, hydrocarbon gas such as propane or butane, COG, mixed gas of COG and other by-product gas, the diameter of the fuel gas piping and the fuel flow control valve is low. It can be smaller than that for calorigas. As a result, the valve closing stroke is shortened and a quick response is possible. In addition, if the gas properties including the caloric value are stable, it is not necessary to set the control gain of the fuel flow control valve small. Further, since there is no need to provide a fuel compressor, there is no increase in the moment of inertia of the rotating body. As a result, the fuel flow rate control valve can be quickly closed to the minimum required opening even when the load drops suddenly. However, even when high calorie gas is used, there are cases where the moment of inertia increases due to the additional installation of various devices in the gas turbine after operation, and the control gain needs to be reset. Even in such a case, if a gas supply device for heat reduction is installed, the load shutoff operation can be performed without having to change or modify the fuel flow control valve by using the gas turbine heat input reduction function. It becomes possible to complement easily and accurately.

  The gas turbine control system of the present invention easily realizes a reduction in the amount of heat input that cannot be achieved only by narrowing the fuel flow control valve by mixing the heat reducing gas with the fuel gas. Such a gas turbine control system can be applied to a gas turbine power generation facility without requiring a large design change.

It is a distribution diagram showing roughly an example of gas turbine power generation equipment including one embodiment of a gas turbine control system of the present invention. FIG. 2A is a graph showing a change in load when the load of the gas turbine is interrupted, and FIG. 2B is a graph showing a change in the opening degree of the fuel flow control valve controlled in response to the load interruption. 2 (c) is a graph showing a change in the amount of heat input to the gas turbine due to a change in the opening of the fuel flow control valve. FIG. 2 (d) shows a change in the opening of the fuel flow control valve and It is a graph which shows the change of the gas turbine heat input by supply of the gas for heat reduction, and FIG.2 (e) is a graph which shows the rotation speed change of the gas turbine produced by the change of this gas turbine heat input. It is a distribution diagram showing roughly other examples of gas turbine power generation equipment containing one embodiment of a gas turbine control system of the present invention.

Explanation of symbols

1. Gas turbine power generation equipment
2 ... Gas turbine
3 ... Fuel gas supply piping
4 ... Fuel compressor
5 .... Gas supply device for heat reduction
6 .... Hydrogen gas supply device
7. Mixer
8 ... Combustor of gas turbine
9. Fuel flow control valve
10 .... System controller
11. Air compressor
12 .... Generator
13 .... Hydrometer
14 .... Fuel flow meter
15 .... Gas supply source for heat reduction
16 .... Gas supply pipe for heat reduction
17. Gas flow meter for heat reduction
18 .... Flow control valve
19 ... Hydrogen gas supply source
20 .... Hydrogen gas supply pipe
21 ... Hydrogen gas flow meter
22 ... Flow control valve
31 ... Gas turbine power generation facilities
S ... Direct reduction iron equipment

Claims (7)

A gas turbine control system that suppresses an increase in the rotational speed of a gas turbine when the load of the gas turbine suddenly drops,
A fuel flow control valve for adjusting the flow rate of the fuel gas, disposed in a fuel gas supply passage for supplying the fuel gas to the gas turbine;
A heat reducing gas supply device for supplying heat reducing gas to the fuel gas supply passage;
A system controller,
When the system controller detects a sudden drop in the load of the gas turbine, in order to reduce the amount of heat input to the gas turbine, in addition to the opening control of the fuel flow control valve, the heat reduction by the heat reducing gas supply device A gas turbine control system configured to control a gas supply operation.   When the load of the operating gas turbine rapidly decreases to a predetermined value, the system control device closes the fuel flow control valve to an opening that does not fall below a predetermined minimum opening, The gas turbine control system according to claim 1, wherein control is performed so that the heat reduction gas necessary for the rotation speed not to exceed a predetermined value is supplied from the heat reduction gas supply device.   The system controller uses the detected rotation speed of the gas turbine as a feedback input signal, and determines the supply amount of the heat reduction gas from the heat reduction gas supply apparatus so that the rotation speed of the gas turbine does not exceed a predetermined value. The gas turbine control system according to claim 2 which performs feedback control. In the system control apparatus, an event of a process in which the load of the operating gas turbine rapidly decreases to a predetermined value is modeled, and the opening degree of the gas supply control for heat reduction and the fuel flow control valve made along the model is modeled Control simulation results are stored,
The system control device is configured to select and execute a preset control mode based on the simulation result when the load of the operating gas turbine rapidly decreases to a predetermined value. Gas turbine control system. A hydrogen gas supply device for supplying hydrogen gas to the fuel gas supply passage, and a hydrogen concentration detection device for detecting the hydrogen concentration in the fuel gas,
The gas turbine control system according to claim 1, wherein the system control device is configured to control a hydrogen gas supply operation by the hydrogen gas supply device based on a detection result of the hydrogen concentration. A gas turbine control method for suppressing an increase in the rotational speed of a gas turbine when the load of the gas turbine suddenly drops,
When a sudden drop in the load on the gas turbine is detected,
A fuel flow rate adjusting step for adjusting the flow rate of the fuel gas by controlling the opening degree of the fuel flow rate control valve disposed in the fuel gas supply passage for supplying the fuel gas to the gas turbine;
A heat reduction gas supply step for supplying a heat reduction gas to the fuel gas supply passage,
A method for controlling a gas turbine, which executes these steps to reduce the amount of heat input to the gas turbine. When the load on the operating gas turbine drops rapidly to a predetermined value,
In the fuel flow rate adjustment step, the fuel flow rate control valve is closed to an opening degree that does not fall below a predetermined minimum opening degree to reduce the fuel flow rate,
The gas turbine control method according to claim 6, wherein in the heat reduction gas supply step, a heat reduction gas necessary for preventing the rotation speed of the gas turbine from exceeding a predetermined value is supplied to the fuel gas supply passage.

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