JP2013228147A - Water supply control method and water supply control device of boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water supply control method and a water supply control device of a boiler capable of being easily applied even to an existing boiler since any new control equipment is not added, and controlling the water level fluctuation of the boiler in a low load zone.SOLUTION: A water supply control device of a boiler includes a water supply flow rate calculation unit 10, a water supply pump rotation number calculation unit 20, and a water supply operation amount calculation unit 30. The water supply flow rate calculation unit 10 calculates a water supply flow rate from deviation between a water level set value and a water level measurement value. The water supply pump rotation number calculation unit 20 calculates the number of rotation of a water supply pump based on the calculated water supply flow rate and a boiler pressure measurement value. The water supply operation amount calculation unit 30 calculates a water supply operation amount from the calculated number of rotation of the water supply pump, and controls the number of rotation of the water supply pump by the operation amount.

Description

  The present invention relates to a boiler water supply control method and a water supply control device. More specifically, the present invention relates to a boiler water supply control method and a water supply control device capable of suppressing water level fluctuations in a low load region.

  Conventionally, in a boiler, the water level is controlled so as to keep the water level of the boiler constant. As a method for controlling the water level, the rotational speed of the water supply pump is controlled.

  When the feed water pump is controlled by the rotational speed control, even if the rotational speed is controlled to be constant, the actual water supply amount varies due to the fluctuation of the boiler pressure. This fluctuation appears remarkably in a low load region where the rotational speed is low due to the characteristics of the feed water pump, and the water supply amount becomes zero at the moment when the rotational speed becomes lower than the rotational speed that is different depending on the boiler pressure. However, the operation of the boiler and the rotation speed control are continued thereafter, and the rotation speed of the feed water pump is increased as the boiler water level decreases.

  However, since there is a delay in the amount of water actually supplied to the boiler, the water supply control does not match the actual situation. As a result, in the low load region, the feed water flow rate is turned on / off despite the rotation speed control of the feed water pump. Therefore, the boiler water level hunts and the boiler pressure also fluctuates.

  In order to solve this problem, a proposal is made in Patent Document 1. However, in the control method according to the proposal of Patent Document 1, it is necessary to provide a flow sensor, which causes another problem that the control equipment becomes expensive. In addition, there is a problem that application to an existing boiler is not easy.

JP 2005-282932 A

  The present invention has been made in view of the problems of the prior art, and since it is not necessary to add a new control facility, it can be easily applied to an existing boiler and can suppress fluctuations in the water level of the boiler in a low load region. An object of the present invention is to provide a water supply control method and a water supply control device.

  The boiler water supply control method of the present invention is a procedure for calculating the feed water flow rate from the deviation between the water level set value and the water level measurement value, and a procedure for calculating the rotation speed of the feed water pump based on the calculated feed water flow rate and the boiler pressure. And a procedure for calculating an operation amount of the water supply amount from the calculated number of revolutions.

  In the boiler feedwater control method of the present invention, the flow rate, the feedwater pump speed, and the boiler pressure are correlated with each other due to physical characteristics. For example, the feedwater pump speed is calculated by the following equation: Is done.

n = ((K ₂ × G ² + P) / K ₁ ) ^0.5
Where n: feed water pump speed G: feed water flow rate calculation value P: boiler pressure measurement value K ₁ , K ₂ : constants determined by the feed water pump

  The boiler feed water control apparatus of the present invention includes a feed water flow rate calculation unit, a feed water pump rotational speed calculation unit, and a feed water amount manipulated variable calculation unit, wherein the feed water flow rate calculation unit includes a water level set value and a water level measurement value. The feed water flow rate is calculated from the deviation, and the feed water pump rotation speed calculation unit calculates the rotation speed of the feed water pump based on the calculated feed water flow rate and the boiler pressure measurement value, and the feed water amount The operation amount calculation unit is characterized in that the operation amount of the water supply amount is calculated from the calculated water supply pump rotation speed.

  In the boiler water supply control device of the present invention, for example, the rotation speed of the water supply pump is calculated by the following equation.

n = ((K ₂ × G ² + P) / K ₁ ) ^0.5
Where n: feed water pump speed G: feed water flow rate calculation value P: boiler pressure measurement value K ₁ , K ₂ : constants determined by the feed water pump

  Therefore, the boiler water supply control device of the present invention is provided in the boiler.

  Since the present invention is configured as described above, it is possible to calculate the rotation speed of an appropriate feed water pump in consideration of the influence of the boiler pressure with respect to the calculated flow rate, and the feed water flow rate in the low load region can be calculated. On / off is avoided and stabilization of the feed water flow rate is achieved, thereby producing an excellent effect of suppressing fluctuations in the water level of the boiler. In addition, since no new control equipment is required, it can be easily applied to existing boilers.

It is a block diagram of the feed water pump control device concerning one embodiment of the present invention. It is a block diagram of the feed water pump control apparatus by the conventional control. It is a graph which shows a simulation result, (a) shows a water level fluctuation | variation, (b) shows the fluctuation | variation of a water supply flow volume.

  Hereinafter, although the present invention is explained based on an embodiment, referring to an accompanying drawing, the present invention is not limited only to this embodiment.

  FIG. 1 is a block diagram showing a water supply control device C to which a boiler water supply control method according to an embodiment of the present invention is applied.

  The water supply control device C is configured, for example, by storing a program that performs processing to be described later in a computer. As shown in FIG. 1, the water supply flow rate calculation unit 10, the water supply pump rotation speed calculation unit 20, and the water supply amount manipulated variable The calculation unit 30 is provided as a main part.

  The feed water flow rate calculation unit 10 calculates the feed water flow rate from the deviation between the water level setting value and the boiler water level measurement value (hereinafter sometimes simply referred to as the water level measurement value).

  The feed water pump rotation speed calculation unit 20 calculates the rotation speed of the feed water pump according to the following formula based on the feed water flow rate calculated by the feed water flow rate calculation unit 10 and the measured value of the boiler pressure.

n = ((K ₂ × G ² + P) / K ₁ ) ^0.5
Where n: feed water pump speed G: feed water flow rate calculation value P: boiler pressure measurement value K ₁ , K ₂ : constants determined by the feed water pump

  The water supply amount operation amount calculation unit 30 calculates a ratio with respect to the rated rotation number by dividing the feed water pump rotation number calculated by the water supply pump rotation number calculation unit 20 by the rated rotation number (this process is referred to as “ It is referred to as “normalization processing”.), For example, processing for calculating%. This ratio value (this value is referred to as “normalized value” in the present specification) corresponds to the inverter output frequency when the rotation speed control is performed by the inverter control. That is, the standardized value 0-100% corresponds to the inverter output frequency 0-60 Hz (or 0-50 Hz).

  As described above, in the present embodiment, the measured value of the boiler pressure is used in calculating the rotation speed of the feed water pump, and the characteristics of the feed water pump are also taken into account. The rotation speed of the feed water pump that matches is calculated. Therefore, in this embodiment, the feed water flow rate is stable, and fluctuations in the boiler water level and on / off of the feed water flow rate in the low load region are avoided. That is, the boiler water level and the feed water flow rate are stabilized.

  Moreover, in this embodiment, since a new control installation is not required, the application to an existing boiler is also easy.

  Hereinafter, the present invention will be described based on more specific examples.

  A simulation when the load is reduced is performed in both the control according to the present embodiment and the conventional control shown in FIG. 2, and the result is shown in FIG.

  As shown in FIG. 2, the conventional water level control device 100 includes a feed water flow rate calculation unit 110, a feed water pump rotation number calculation unit 120, a normalization processing unit 130, and a limit processing unit 140, and sets a water level set value and a water level measurement. The feed water flow rate is calculated based on the deviation from the value, then the feed water pump rotation speed is calculated from the calculated feed water flow rate, and it is normalized, and the calculated normalized value is determined as the upper limit value determined by the boiler pressure and The amount of operation of the water supply amount is calculated by performing a limit process with the lower limit value.

  The simulation was performed by setting the control constants of the feed water flow rate calculation units 10 and 110 to be the same.

  Moreover, the outline of the boiler and the outline of the feed water pump which performed simulation are shown below.

Boiler Outline Model: Multi-tube once-through boiler Equivalent evaporation: 4000kg / h
Maximum working pressure: 0.98 MPa

Outline of water supply pump Model: Multi-stage inline centrifugal pump Discharge rate: 70L / min
Total lift: 116m

  From FIG. 3 (a), according to this embodiment, it is understood that the boiler water level stabilizes quickly, and from FIG. 3 (b), on / off of the feed water flow rate is avoided, and hunting of the boiler water level is avoided. Is understood.

  The present invention can be applied to the boiler industry. Further, since the present invention does not require new control equipment, it can be easily applied to existing boilers.

DESCRIPTION OF SYMBOLS 10 Water supply amount calculation part 20 Water supply pump rotation speed calculation part 30 Water supply amount operation amount calculation part C Water supply control apparatus

Claims (5)

A procedure for calculating the feed water flow rate from the deviation between the water level set value and the water level measurement value,
A procedure for calculating the rotation speed of the feed water pump based on the calculated feed water flow rate and boiler pressure;
And a procedure for calculating an operation amount of the water supply amount from the calculated number of revolutions. The boiler feed water control method according to claim 1, wherein the rotation speed of the feed water pump is calculated by the following equation.
n = ((K ₂ × G ² + P) / K ₁ ) ^0.5
Where n: feed water pump speed G: feed water flow rate calculation value P: boiler pressure measurement value K ₁ , K ₂ : constants determined by the feed water pump A water supply flow rate calculation unit, a water supply pump rotation speed calculation unit, and a water supply amount operation amount calculation unit,
The feed water flow rate calculation unit calculates the feed water flow rate from the deviation between the water level setting value and the water level measurement value,
The feed water pump speed calculation unit calculates the speed of the feed water pump based on the calculated feed water flow rate and the boiler pressure measurement value,
The water supply control device for a boiler, wherein the water supply amount operation amount calculation unit calculates an operation amount of the water supply amount from the calculated water supply pump rotation speed. The boiler feed water control device according to claim 3, wherein the rotation speed of the feed water pump is calculated by the following equation.
n = ((K ₂ × G ² + P) / K ₁ ) ^0.5
Where n: feed water pump speed G: feed water flow rate calculation value P: boiler pressure measurement value K ₁ , K ₂ : constants determined by the feed water pump   A boiler comprising the water supply control device according to claim 3 or 4.