JP3768335B2 - Fuel supply control apparatus and method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel supply control apparatus and method suitable for use in supplying natural gas to a thermal power plant.
[0002]
[Prior art]
An increasing number of thermal power plants (consumption means) perform combined power generation using natural gas supplied from an LNG (liquefied natural gas) base as fuel. This type of thermal power plant operates multiple power generation units (fuel consumption units) with relatively small capacities to supply power, and is more efficient than conventional large boilers and turbines. It is characterized by good followability to changes in demand.
[0003]
On the other hand, the LNG base vaporizes LNG (liquid fuel) stored in the LNG tank at a low temperature using a plurality of vaporizers to generate natural gas (gaseous fuel), and the natural gas is used as a demand for thermal power plants. Sending in response. For example, at the LNG base, when natural gas is sent to a thermal power plant, the natural gas delivery amount is controlled based on the consumption information of the natural gas input from the thermal power plant and the pressure of the delivery pipe. Here, the distance between the LNG base and the thermal power plant is generally several kilometers away, and there is a time delay in the pressure change in the delivery pipe with respect to the change in the natural gas consumption in the thermal power plant. Occurs. For this reason, the LNG base controls the delivery amount of the natural gas by adding the consumption amount of the natural gas in the thermal power plant to the pressure of the delivery pipe.
[0004]
[Problems to be solved by the invention]
By the way, at the LNG base, the natural gas of the amount required by the thermal power plant could not be delivered by the conventional natural gas delivery method described above. The following points are raised as the cause.
(1) A thermal power plant that performs combined power generation operates a plurality of combined power generation units to generate power. In this case, there is a gas flow meter that measures the consumption of natural gas for each combined power generation unit. Provided. That is, the consumption information output from the thermal power plant to the LNG base is the total flow rate measured by a plurality of gas flow meters. Therefore, the measurement errors of these individual gas flow meters are integrated.
(2) The composition of LNG varies greatly depending on the place of origin. That is, when the composition of the natural gas delivered due to the composition change of LNG changes, the measurement error increases with the current gas flowmeter.
(3) Since the gas flowmeter is provided independently for each combined power generation unit, when an abnormal measurement value is output due to a failure or the like, this abnormal measurement value becomes a direct disturbance in the transmission control at the LNG base. .
(4) When a large amount of natural gas is collected for sampling or the like, the amount collected by this sampling becomes a direct disturbance in the transmission control at the LNG base.
[0005]
The present invention has been made in view of the above-described problems, and is capable of delivering a more accurate amount of natural gas with respect to the true natural gas consumption amount in a thermal power plant, and the rapid consumption amount. It is an object of the present invention to provide a fuel supply control device and method that have good followability to various fluctuations.
[0006]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, as a first means, when the gaseous fuel generated from the liquid fuel by the vaporizer is delivered, the gas fuel delivery pressure, the flow rate of the liquid fuel, and the gas consumed in the consuming means In a fuel supply control device for supplying gaseous fuel in an amount required by consumption means by controlling a flow rate control valve provided at an inlet of a carburetor based on a gas flow rate of fuel, the flow rate, the gas flow rate, , A first control signal generating device that generates a first control signal based on the output of the subtractor and the delivery pressure, the first control signal, and the flow rate of the liquid fuel And a second control signal generator for generating a second control signal for controlling the flow control valve based on the above.
[0007]
As a second means, when gaseous fuel generated from liquid fuel by a plurality of vaporizers is delivered, the gas consumed in the consuming means comprising the delivery pressure of the gaseous fuel, the flow rate of the liquid fuel, and a plurality of fuel consumption units In the fuel supply control device for supplying the amount of gaseous fuel required by the consumption means by controlling the flow rate control valve provided at the inlet of each carburetor based on the gas flow rate of the fuel, each fuel consumption unit A gas flow summing device for summing the gas flow rates, a liquid flow summing device for summing each flow rate of the liquid fuel, and a subtractor for calculating a difference between an output of the gas flow summing device and an output of the liquid flow summing device A first control signal generating device that generates a first control signal based on the output of the subtractor and the delivery pressure, the output of the first control signal and the liquid flow rate summing device And a third control signal obtained by equally dividing the control amount indicated by the second control signal according to the number of carburetors in operation. And a plurality of valve control signal generators for generating valve control signals for controlling the flow rate control valves based on the third valve control signal, respectively.
[0008]
As a third means, when the gaseous fuel generated from the liquid fuel is delivered by the vaporizer, vaporization is performed based on the delivery pressure of the gaseous fuel, the flow rate of the liquid fuel, and the gas flow rate of the gaseous fuel consumed by the consuming means. Calculating a flow rate difference between the flow rate and the gas flow rate in a fuel supply control method for supplying gaseous fuel in an amount required by the consumption means by controlling a flow rate control valve provided at the inlet of the vessel; A step of generating a first control signal based on the flow rate difference and the delivery pressure; and a second control signal for controlling the flow rate control valve based on the first control signal and the flow rate of the liquid fuel. Means for generating is employed.
[0009]
As a fourth means, when gas fuel generated from liquid fuel by a plurality of vaporizers is sent, the gas consumed in the consumption means composed of the delivery pressure of the gas fuel, the flow rate of the liquid fuel, and a plurality of fuel consumption units In the fuel supply control method for supplying the amount of gaseous fuel required by the consuming means by controlling the flow rate control valve provided at the inlet of each carburetor based on the gas flow rate of the fuel, each fuel consumption unit Calculating the total gas flow rate, summing the flow rates of the liquid fuels to calculate the total flow rate, calculating the flow rate difference between the total gas flow rate and the total flow rate, Generating a first control signal based on the flow rate difference and the delivery pressure, generating a second control signal based on the first control signal and the total flow rate, and A step of generating a third control signal by equally dividing the control amount indicated by the control signal of 2 by the number of operating carburetors, and a valve control for controlling the flow rate control valve based on the third valve control signal, respectively. Means for generating a signal is employed.
[0010]
As a fifth means, a means is adopted in which the above four means are applied to delivery of natural gas obtained by vaporizing liquefied natural gas.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, with reference to FIG.1 and FIG.2, one Embodiment of the fuel supply control apparatus concerning this invention and its supply method is described.
[0012]
FIG. 1 is a block diagram showing a natural gas (gaseous fuel) supply system in the present embodiment. In this figure, symbol A is an LNG base and symbol B is a thermal power plant (consumption means). The LNG base A includes an LNG tank 1, an LNG pump 2, flow control valves 3a to 3e, flow meters 4a to 4e, vaporizers 5a to 5e, a pressure gauge 6, and a fuel supply control device 7.
[0013]
The LNG tank 1 stores LNG (liquid fuel) at a low temperature, and the LNG pump 2 pumps LNG out of the LNG tank 1 and sends it to the vaporizers 5a to 5e. In general, a plurality of LNG tanks 1 and LNG pumps 2 are provided according to the scale of the LNG base A. At the inlets of the vaporizers 5a to 5e, there are one flow rate control valves 3a to 3e for limiting the flow rate of LNG flowing into the vaporizers 5a to 5e, and one flow meter 4a to 4e for detecting the flow rate, respectively. Is provided.
[0014]
The flow meters 4a to 4e output the flow rate of LNG flowing into the vaporizers 5a to 5e to the fuel supply control device 7 independently as flow rate signals Xa to Xe. Each vaporizer 5a-5e vaporizes LNG using seawater, and outputs a natural gas. The pressure gauge 6 measures the pressure of the delivery pipe that sends natural gas to the thermal power plant B, and outputs the pressure to the fuel supply control device 7 as a pressure signal Y. The delivery pipe is a pipe that collects the natural gas output from each of the vaporizers 5a to 5e and sends it to the thermal power plant B.
[0015]
The thermal power plant B is a combined power plant, and includes, for example, five combined power generation units (fuel consumption units) U1 to U5. A number of the combined power generation units U1 to U5 are operated according to the power demand, and a gas flow meter for measuring the gas flow rate of the natural gas supplied from the LNG base A through the delivery pipe at the entrance thereof G1 to G5 are provided. The gas flow meters G1 to G5 output the flow rate of natural gas flowing into the combined power generation units U1 to U5 to the fuel supply control device 7 as gas flow rate signals Z1 to Z5. The fuel supply control device 7 controls the opening degree of each of the flow rate control valves 3a to 3e based on the flow rate signals Xa to Xe, the pressure signal Y, and the gas flow rate signals Z1 to Z5.
[0016]
Next, FIG. 2 is a block diagram showing a detailed configuration of the fuel supply control device 7. In this figure, reference numerals 7a and 7b denote adders, and an adder (gas flow summing device) 7a sums the flow rates of natural gas measured by the gas flow meters G1 to G5, and adds (total liquid flow rate). (Device) 7b is a total of LNG flow rates obtained by compressing LNG and BOG (Boil Off Gas: gas generated by LNG vaporization in the LNG tank 1 etc.) measured by the flow meters 4a to 4e. To do. Reference numeral 7c denotes a subtracter that outputs the difference between the total values of the adders 7a and 7b.
[0017]
Reference numerals 7d and 7e denote control signal generators (PID). Among them, the control signal generator (first control signal generator) 7d is controlled from the output of the subtractor 7c and the measured value of the pressure gauge 6 of the LNG base A. The signal P1 is generated, and the control signal generator (second control signal generator) 7e generates a control signal P2 from the control signal P1 and each output of the adder 7b. The control signal generation devices 7d and 7e output control signals P1 and P2 based on the two input signals, for example, by multiplying (modulating) the two signals input to each.
[0018]
Reference numeral 7f denotes a distributor, which generates a control signal P3 obtained by equally dividing the control amount indicated by the control signal P2 according to the number of operating carburetors 5a to 5e. Reference numerals 7ga to 7ge are also control signal generators (valve control signal generators) that output control signals for controlling the flow control valves 3a to 3e, respectively. The fuel supply control device 7 controls the flow rate control valves 3a to 3e by the control loop configured as described above, and controls the delivery amount of natural gas supplied from the LNG base A to the thermal power plant B.
[0019]
Reference numeral 7h denotes a pump operation number control device, which supplies seawater to the carburetors 5a to 5e based on an operation preparation signal (a signal indicating the operation state of each combined power generation unit U1 to U5) output from the thermal power plant B. The number of operating LNG pumps 9 and the number of LNG pumps 9 that send LNG to the vaporizers 5a to 5e is set, and start command signals are output to the vaporizer seawater pump 8 and the LNG pump 9 based on the set values. To do.
[0020]
Next, the operation of the fuel supply control device 7 will be described.
The thermal power plant B operates the required number of combined power generation units according to the power demand. Here, all the combined power generation units U1 to U5 are operating, and the carburetor seawater pump 8 and the LNG pump 9 are in operation. It is assumed that the number of operating units is preset based on the operation preparation signal of the thermal power plant B by the pump operating number control device 7h.
[0021]
Now, when the demand for electric power increases and the consumption of natural gas in the combined power generation units U1 to U5 increases, the gas flow rate of the natural gas indicated by the gas flow rate signals Z1 to Z5 increases, and the output of the adder 7a increases rapidly. As a result, the output of the subtractor 7c increases. However, since the distance between the LNG base A and the thermal power plant B is several kilometers away, the pressure signal Y output by the pressure gauge 6 of the LNG base A does not decrease immediately, and a time delay based on the distance is not achieved. It decreases with it. Therefore, the control signal P1 increases based on the output increase of the gas flow meters G1 to G5 provided in the combined power generation units U1 to U5.
[0022]
Here, the control signal generator 7d is driven based on a signal obtained by subtracting the total value of the flow rate signals Xa to Xe from the total value of the gas flow rate signals Z1 to Z5. That is, the total value of the gas flow signals Z1 to Z5 output from the gas flowmeters G1 to G5 having a large measurement error is the flow signal output from the liquid flowmeters, that is, the flowmeters 4a to 4e having a relatively small measurement error. The deviation is calculated from the total value of Xa to Xe.
[0023]
Subsequently, the control signal generator 7e generates and outputs a control signal P2 based on the control signal P1 and the output signal of the adder 7b. Here, by adding the total value of the flow rate signals Xa to Xe again, the measurement error included in the total value of the gas flow rate signals Z1 to Z6 is reduced, and the influence of the time delay of the pressure signal Y is reduced. The
[0024]
The control signal P2 is converted into a control signal P3 by dividing the control amount, that is, the flow rate of LNG flowing into the vaporizers 5a to 5e into five equal parts by the distributor 7f. The valve control signal generators 7ga to 7ge increase the opening degree of each flow rate control valve 3a to 3e based on the control signal P3, and increase the passage flow rate of LNG equally. As a result, the flow rate of LNG flowing into each of the carburetors 5a to 5e is evenly increased, the gas flow rate of natural gas sent from the LNG base A to the thermal power plant B is increased, and the pressure signal Y increases. .
[0025]
By using the fuel supply control device 7 that constitutes such a feedback loop, the measurement error or operation failure of the gas flow meters G1 to G5 is canceled, and the amount of natural gas that the thermal power plant B really needs is thermal power. Supplied to power station B. Further, the time delay of the delivery pressure measured by the pressure gauge 6 is compensated, and the delivery control of the natural gas that responds at high speed to the fluctuation of the natural gas consumption of the thermal power plant B can be realized. Since the measurement error increases as the number of gas flow meters increases, the fuel supply control device 7 of this embodiment has a plurality of combined power generation units U1 to U5, and thus has a plurality of gas flow meters G1 to G5. Effective for power plants.
[0026]
In addition, although the said embodiment demonstrated the case where the flow control valves 3a-3e were controlled based on the measured value of several gas flowmeters G1-G5 and several flowmeters 4a-4e, this invention is limited to this. Although not practical as an LNG base and a thermal power plant, natural gas delivered from the LNG base is controlled by controlling one flow control valve with each one gas flow meter and flow meter. It is also possible to adjust the flow rate. In this case, however, the adders 7a and 7b and the distributor 7f are not necessary, and only one control signal generator for directly controlling the flow rate control valve is required.
[0027]
Furthermore, the present invention is not limited to the natural gas delivery control as described above, but is used for a fuel supply system that controls the delivery gas based on the measurement value of the gas flowmeter with many measurement errors. It is valid.
[0028]
【The invention's effect】
As described above, the fuel supply control device and the supply method according to the present invention have the following effects.
(1) The first control signal is generated based on the difference between the flow rate of the liquid fuel and the gas flow rate consumed by the consumption means and the delivery pressure, and based on the first control signal and the flow rate of the liquid fuel. Since the second control signal for controlling the flow rate control valve is generated, the consumption means can be used even when there is a detection error in the gas flow rate or when there is a mismeasurement in a plurality of gas flow meters that detect the gas flow rate. The required amount of gaseous fuel can be supplied.
(2) The first control signal is generated based on the difference between the flow rate of the liquid fuel and the gas flow rate consumed by the consumption means and the delivery pressure, and based on the first control signal and the flow rate of the liquid fuel. Since the second control signal for controlling the flow rate control valve is generated, the gaseous fuel can be supplied with good responsiveness to a sudden change of the gaseous fuel by the consuming means.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a natural gas supply system to which a fuel supply control apparatus and method according to the present invention are applied.
FIG. 2 is a block diagram showing a detailed configuration of a fuel supply control device according to the present invention.
[Explanation of symbols]
A LNG base B Thermal power plant (consumption means)
G1 to G5 Gas flowmeters P1 and P2 Control signals U1 to U5 Combined power generation unit (fuel consumption unit)
Xa to Xe Flow signal Y Pressure signal Z1 to Z5 Gas flow signal 1 LNG tank 2 LNG pumps 3a to 3e Flow control valves 4a to 4e Flow meters 5a to 5e Vaporizer 6 Pressure gauge 7 Fuel supply control device 7a Adder (Gas flow rate Total equipment)
7b Adder (liquid flow totalizer)
7c Subtractor 7d Control signal generator (PID: first control signal generator)
7e Control signal generator (PID: second control signal generator)
7ga-7ge control signal generator (PID: valve control signal generator)
7f Distributor 7h Pump operation number control device 8 Vaporizer seawater pump 9 LNG pump

Claims (6)

When the gaseous fuel generated from the liquid fuel by the vaporizer is delivered, it is provided at the inlet of the vaporizer based on the delivery pressure of the gaseous fuel, the flow rate of the liquid fuel, and the gas flow rate of the gaseous fuel consumed by the consuming means. A fuel supply control device for supplying gaseous fuel in an amount required by the consumption means by controlling the flow control valve,
A subtractor for calculating a difference between the flow rate and the gas flow rate;
A first control signal generating device for generating a first control signal based on the output of the subtractor and the delivery pressure;
A second control signal generating device for generating a second control signal for controlling the flow rate control valve based on the first control signal and the flow rate of the liquid fuel;
A fuel supply control device comprising: When the gaseous fuel generated from the liquid fuel is delivered by a plurality of vaporizers, the delivery pressure of the gaseous fuel, the flow rate of the liquid fuel, and the gas flow rate of the gaseous fuel consumed in the consumption means comprising a plurality of fuel consumption units A fuel supply control device for supplying a gaseous fuel in an amount required by the consumption means by controlling a flow rate control valve provided at an inlet of each carburetor,
A gas flow rate summing device for summing up the gas flow rates of the fuel consuming units;
A liquid flow summing device for summing the flow rates of the liquid fuels;
A subtractor that calculates the difference between the output of the gas flow summing device and the output of the liquid flow summing device;
A first control signal generating device for generating a first control signal based on the output of the subtractor and the delivery pressure;
A second control signal generating device that generates a second control signal based on the first control signal and the output of the liquid flow rate summing device;
A distributor that outputs a third control signal obtained by equally dividing the control amount indicated by the second control signal according to the number of operating vaporizers;
A plurality of valve control signal generators for generating valve control signals for controlling the flow rate control valves based on the third valve control signals;
A fuel supply control device comprising: 3. The fuel supply control device according to claim 1, wherein the fuel supply control device is applied to delivery of natural gas obtained by vaporizing liquefied natural gas. When the gaseous fuel generated from the liquid fuel by the vaporizer is delivered, it is provided at the inlet of the vaporizer based on the delivery pressure of the gaseous fuel, the flow rate of the liquid fuel, and the gas flow rate of the gaseous fuel consumed by the consuming means. A fuel supply control method for supplying gaseous fuel in an amount required by the consumption means by controlling the flow control valve,
Calculating a flow rate difference between the flow rate and the gas flow rate;
Generating a first control signal based on the flow rate difference and the delivery pressure;
Generating a second control signal for controlling the flow rate control valve based on the first control signal and the flow rate of the liquid fuel;
A fuel supply control method comprising: When the gaseous fuel generated from the liquid fuel is delivered by a plurality of vaporizers, the delivery pressure of the gaseous fuel, the flow rate of the liquid fuel, and the gas flow rate of the gaseous fuel consumed in the consumption means comprising a plurality of fuel consumption units A fuel supply control device for supplying a gaseous fuel in an amount required by the consumption means by controlling a flow rate control valve provided at an inlet of each carburetor,
Summing the gas flow rate of each fuel consuming unit to calculate the total gas flow rate;
Adding each flow rate of the liquid fuel to calculate a total flow rate; and
Calculating a flow rate difference between the total gas flow rate and the total flow rate;
Generating a first control signal based on the flow rate difference and the delivery pressure;
Generating a second control signal based on the first control signal and the total flow rate;
Generating a third control signal obtained by equally dividing the control amount indicated by the second control signal according to the number of operating vaporizers;
Generating a valve control signal for controlling each flow control valve based on the third valve control signal;
A fuel supply control method comprising: 6. The fuel supply control method according to claim 4, which is applied to delivery of natural gas obtained by vaporizing liquefied natural gas.

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