JP2008164264A - Flow control apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To carry out fuel flow control with high readiness with respect to sudden change of a fuel flow desired value, fluctuation of fuel flow control valve post-pressure, and change of the number of ignited burners in a flow control system. <P>SOLUTION: The flow control system is provided for controlling a flow control valve 6 provided in a piping supplying fluid. The number of ignited burners is calculated from a state of a limit switch per burner stop valve, a burner post-pressure is calculated from the number of ignited burners and a fuel flow set value, a valve flow coefficient of the flow control valve 6 is calculated by the burner post-pressure, an upstream side pressure of the flow control valve, and the fuel flow desired value, a valve opening of the flow control valve 6 is calculated on the basis of the calculated valve flow coefficient, and the opening of the flow control valve 6 is controlled by a signal adding a valve opening signal and a correction amount signal from the flow control system. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a flow rate control device suitable for controlling the supply amount of fuel (fluid) in, for example, power plant boilers, industrial boilers, and the like.

  As a conventional technique, for example, as described in [Patent Document 1], in a boiler fuel flow control, there is one in which a fuel flow control valve is operated in advance by a fuzzy controller from the number of burners, the fuel flow rate, and the fuel pressure. .

  Further, as described in [Patent Document 2], the opening of the fuel regulator is calculated based on the required combustion amount determined by the load of the boiler and the number of operating burners, and the required combustion amount and the burner are calculated. There is one that sets the opening degree based on an addition value obtained by adding the opening degree of the combustion amount regulator corresponding to the deviation of the supplied fuel amount.

JP 7-233936 A JP-A 63-286614

  In the technique described in [Patent Document 1], the fuel flow rate control is a combination of the fuel flow rate, the fuel pressure, and the number of burners on the downstream side of the fuel flow control valve, and by fuzzy control using a jumping function, The control valve opening correction amount is obtained.

  In this method, since the flow control valve command signal corrected by the flow control valve correction signal is output by fuzzy control using a jumping function, the fuel flow rate changes, and further, the fuel flow rate change affects the correction signal. Therefore, there is an element in which the pressure after the fuel flow control valve becomes unstable. In addition, when mutual interference with fuel flow control becomes unavoidable, feedback control is used for fluctuations in the pre-pressure of the flow control valve and changes in the required flow rate. There is a difficulty in the responsiveness of the corresponding fuel flow control.

  In the technique described in [Patent Document 2], the opening degree of the fuel regulator is merely calculated and controlled in advance based on the required combustion amount determined by the load of the boiler and the number of operating burners. Since the influence is large and feedback control is performed with respect to fluctuations in the pre-pressure of the flow control valve and changes in the required flow rate, there is a difficulty in the responsiveness of the fuel flow control corresponding to the pre-control valve pressure and the required flow rate.

  An object of the present invention is to provide a flow rate control apparatus that can stably control the flow rate of a fluid with a small ratio that depends on feedback control.

  In order to achieve the above object, a flow control device of the present invention calculates a pre-burner pressure from the number of ignition burners and a required fuel flow rate in a fuel flow control system including a flow control valve, and calculates a pre-burner pressure value. The valve coefficient of the flow rate control valve is calculated from the pressure on the upstream side of the flow rate control valve and the fuel flow rate requirement value, and the valve opening degree of the flow rate control valve is calculated from the ratio with the valve coefficient of the fully open flow rate control valve.

  Further, the valve opening calculation means includes a pre-burner predicted pressure calculation unit that calculates a required pre-burner pressure calculation value from the number of burner ignitions and a required fuel flow rate, a pre-burner pressure calculation value, and a pressure upstream of the flow control valve. The valve flow coefficient calculation unit that calculates the valve coefficient of the flow control valve, the ratio calculation unit that calculates the ratio of the valve coefficient to the valve flow coefficient when the flow control valve is fully opened, and the ratio calculated by the ratio calculation unit It is comprised from the function generation | occurrence | production part converted into the valve opening degree.

  According to the present invention, the required pre-burner pressure is calculated from the required flow rate value of the supply destination and the number of ignition burners, and the opening signal of the flow control valve is calculated from the required pre-burner pressure and the pressure upstream of the flow control valve. Since the predetermined opening degree of the flow rate control valve can be obtained quickly by using the opening degree signal as the preceding signal, the ratio depending on the feedback control is reduced, and the flow rate control of the fluid can be performed stably.

  An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a configuration diagram of a flow rate control device according to the present embodiment. The present embodiment is an example in which the flow rate control device for controlling the flow rate is applied to a fuel flow rate device for a boiler that uses liquid fuel as a fuel.

As shown in FIG. 1, a fuel supply mother pipe 12 is connected to the fuel supply unit 11, and a burner 14 is connected to the fuel supply mother pipe 12 via a flow rate adjusting valve 6 and a burner stop valve 13. Fuel is supplied from the section 11 to the burner 14. On the upstream side of the flow control valve 6, the fuel supply main pipe 12 between the fuel supply unit 11 and the flow control valve 6 is provided with a flow transmitter 5 for measuring the flow rate and a pressure transmitter 7 for measuring the pressure. It has been. The burner stop valve 13 is provided with a burner stop valve limit switch 15.

  The burner stop valve limit switch 15 is connected to an ignition burner count circuit 16, and the ignition burner count circuit 16 detects the opening and closing of the burner stop valve 13 and calculates the number of burner ignitions. The ignition burner count circuit 16 is connected to the pre-burner pressure calculation unit 17.

  The fuel setting unit 1 that sets and stores the required fuel flow rate required value FS in the burner 14 is connected to a pre-burner pressure calculation unit 17, a CV value calculation unit 8, which will be described later, and a comparison calculation unit 2. . The CV value calculator 8 is connected to the pre-burner pressure calculator 17 and the pressure transmitter 7. The comparison operator 2 is connected to the flow rate transmitter 5.

  The CV value calculator 8 is sequentially connected to the ratio calculator 9, the function generator 10, the addition calculator 4, and the flow rate control valve 6. The comparison calculator 2 is sequentially connected to the proportional-plus-integral calculator 3 and the addition calculator 4. It is connected to the.

  The ignition burner count circuit 16 and the pre-burner pressure calculation unit 17 constitute a pre-burner predicted pressure calculation unit 101, and the CV value calculator 8, the ratio calculator 9 and the function generator 10 constitute a valve opening command unit 100. Yes. The fuel flow rate control system that controls the flow rate control valve 6 to control the flow rate of fuel includes a fuel setting unit 1, a valve opening command unit 100, a pre-burner predicted pressure calculation unit 101, a comparison calculation unit 2, and a proportional integration calculation unit 3. Consists of.

  The fuel flow rate requirement value FS required by the burner 14 set by the fuel setting unit 1 and the fuel flow rate value 5S measured by the flow rate transmitter 5 are input to the comparator 2 and compared, and the deviation value is calculated. The calculation result is output to the proportional-plus-integral calculator 3. The proportional-plus-integral calculator 3 performs proportional-integral processing on the deviation value calculated by the comparison calculator 2 and outputs the calculation result to the addition calculator 4.

  The burner 14 can be regarded as having been ignited when the burner stop valve 13 is opened, and the fact that the burner stop valve 13 has been opened is detected by a limit switch 15, and the burner count circuit 16 detects the burner 14. The number of ignitions 16S is calculated. The calculated burner ignition number 16S and the fuel flow requirement value FS from the fuel setting unit 1 are input to the pre-burner predicted pressure calculation unit 101, and the pre-burner pressure P2 is calculated.

FIG. 3 shows an example of the relationship between the required fuel flow rate FS and the pre-burner fuel pressure with the number of burner ignitions as a parameter. As shown in this example, the pre-burner pressure P2 is calculated from the burner ignition number 16S calculated by the ignition burner count circuit 16 with respect to the fuel flow rate request value FS from the fuel setting unit 1.

  Next, the valve opening command unit 100 will be described. In the CV value calculator 8 of the valve opening command unit 100, the pressure P1 measured by the pressure transmitter 7 and the pre-burner pressure P2 calculated by the pre-burner predicted pressure calculation unit 101 are input, and the CV value is calculated. .

  When the flow rate of the fuel that is liquid is the weight display of the flow rate of the liquid fluid, the CV value of the flow rate control valve 6 can be calculated by Equation 1.

  Here, CV is the valve flow coefficient, G is the specific gravity, W is the flow rate (t / h), ΔP is the pressure difference (MPa), and ΔP is expressed by Equation 2.

  The CV value calculated by the CV value calculator 8 is input to the ratio calculator 9 and is compared with the CV value when the flow rate control valve 6 is fully opened to calculate the ratio (%). Assuming that the CV value when the flow rate regulating valve 6 is fully opened is CVmax, the output of the ratio calculator 9 is obtained by Equation 3.

  The ratio (%) obtained by the ratio calculator 9 is input to the function generator 10 and the opening degree of the flow rate adjusting valve 9 is calculated. This operation is given as a program function. The function is determined from the inner valve characteristic and the range ability factor. FIG. 2 shows an example of the characteristic.

  Using this characteristic, the opening degree of the flow rate control valve 6 can be calculated by calculating with the program of the function generator 10. In the case of the valve having the equal percent characteristic shown in FIG. 2, the characteristic is the range ability 50, but the flow rate control valve when the ratio of the calculated CV value to the CV value when the flow rate control valve 6 is fully opened is 30%. The valve opening of 6 is about 67%.

  The output of the function generator 10, that is, the preceding control signal 10S, which is a signal of the valve opening command unit 100, and the proportional / integral signal from the proportional-plus-integral calculator 3 are input to the adder 4 and added. Is output to the drive unit of the flow control valve 6.

  The signal output 10S of the valve opening command unit 100 is the flow control valve opening at the pressure upstream of the flow control valve 6 and the pre-burner pressure, and this advance control signal 10S is output to the adder 4 to adjust the flow. By controlling the valve 6 in advance (feed-forward control), stable flow rate control can be obtained earlier. That is, an appropriate opening degree of the flow rate control valve 6 is calculated following a sudden change in various conditions, and the calculation result is given to the flow rate control valve 6 as a preceding value, so that the control is improved.

  In the above-described embodiment, the case where the fuel flowing through the fuel supply pipe 12 is liquid fuel has been described. However, the present invention can also be applied to gaseous fuel. When gaseous fuel is applied to the fuel, it can be similarly configured by replacing the CV value calculation of the flow rate control valve with a calculation formula for gaseous fluid.

  According to this embodiment, the required pre-burner pressure is calculated from the required flow rate value of the supply destination and the number of ignition burners, and the opening signal of the flow control valve is calculated from the required pre-burner pressure and the pressure upstream of the flow control valve. However, since the opening degree of the predetermined flow rate control valve can be obtained quickly by using this opening degree signal as the preceding signal, the ratio depending on the feedback control is reduced, and the flow rate control of the fluid can be performed stably. This contributes to the stable operation of the plant.

  In recent thermal power plants, it is required to respond to load changes according to power demand, but in very rare cases, it is possible to respond flexibly and promptly to such changes even during sudden load reduction operations. There is.

It is a schematic structure figure concerning one example of an embodiment of the present invention. It is a figure showing the relationship between the ratio of the calculated CV value with respect to the CV value at the time of a flow control valve full open, and a control valve opening degree. It is the figure which showed the relationship between fuel flow requirement value FS and the fuel pressure before a burner.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel setting part 2 Comparison calculator 3 Proportional integral calculator 4 Addition calculator 5 Flow rate transmitter 6 Flow rate control valve 7 Pressure transmitter 8 CV value calculator 9 Ratio calculator 10 Function generator 11 Fuel supply part 12 Fuel supply mother Pipe 13 Burner stop valve 14 Burner 15 Burner stop limit switch 16 Ignition burner count circuit 17 Pre-burner pressure calculation unit 100 Valve opening command unit 101 Pre-burner predicted pressure calculation unit FS Fuel flow requirement value

Claims (2)

In a flow control device equipped with a flow control system for controlling a flow control valve provided in a pipe that supplies fluid, calculate the CV value from the pressure upstream of the flow control valve, the required flow rate value, and the pre-burner pressure calculation value. A ratio calculation unit that calculates a ratio of the calculated CV value to the CV value when the flow rate adjustment valve is fully opened, and a function generation that converts the ratio calculated by the ratio calculation unit into a correction opening of the flow rate control valve Addition calculation means for adding the valve opening degree command signal calculated by the unit and the valve opening degree correction signal obtained by the proportional / integral calculation from the deviation of the fuel flow rate signal and the fuel setting unit and outputting to the flow rate control valve Having a flow control device.   The burner pre-pressure calculation value includes an ignition burner count circuit for calculating the number of ignition burners from a limit switch installed for each burner stop valve of each burner, and the number of ignition burners calculated by the ignition burner count circuit and the fuel flow rate. The flow rate control device according to claim 1, further comprising: a pre-burner predicted pressure calculation unit that calculates the pre-burner pressure associated with the point fire extinguishing of the burner by a function generation unit that calculates the pre-burner pressure from the required value.

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