JPH07293803A - Control device for boiler circulation pump - Google Patents

Abstract

PURPOSE:To cause a pump discharging amount corresponding to a requisite circulation ratio to be varied in response to a load by a method wherein a forced circulation boiler is provided with a circulation pump having a variable number of rotation and there is provided a calculator for controlling the number of rotation of the circulation pump in response to a load of the forced circulation boiler. CONSTITUTION:A rotational speed of a boiler circulation pump 3 is made variable by a frequency converter 5 installed at an electrical motor 4 for use in driving:the circulation pump. That is, the number of rotation of the boiler circulation pump 3 is decreased, its discharging volume and its power are correspondingly decreased. The number of rotation of the pump is varied by the calculator to such a number of rotation of the pump as one capable of assuring a requisite minimum circulation ratio in response to a load of the boiler through utilization of the decreased discharging volume and power. The number of rotation of the pump at that time is controlled under a program controlling operation. With such an arrangement as above, the pump discharging volume corresponding to the requisite circulation ratio can be varied in response to a load at that time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device applied to a boiler circulation pump of a forced circulation boiler.

[0002]

2. Description of the Related Art Conventionally, a boiler circulation pump of a forced circulation boiler has been operated at a constant speed.

[0003]

Since the conventional boiler circulation pump is rotated at a constant speed, the discharge amount of the boiler is such that it corresponds to the maximum furnace heat load at the maximum boiler load. Therefore, in a partial load where heat absorption is low, the discharge amount becomes excessive and power is consumed excessively.

[0004]

In order to solve the above-mentioned conventional problems, the present inventor has proposed a circulation pump having a variable rotation speed provided in a forced circulation boiler and the circulation based on the load of the forced circulation boiler. A controller for a boiler circulation pump, comprising: a calculator for controlling the rotation speed of the pump;
And a circulation pump with a variable rotation speed provided in the forced circulation boiler, a means for measuring the can water enthalpy at the furnace outlet of the forced circulation boiler, and a calculation for controlling the rotation speed of the circulation pump based on the can water enthalpy. The present invention proposes a control device for a boiler circulation pump, which is characterized by including a heater.

[0005]

In the present invention, the circulation pump rotation speed of the forced circulation boiler is made variable, and the circulation pump rotation speed is controlled based on the boiler load or the boiler water enthalpy at the furnace outlet. Can be changed according to the load, and the pump drive power can be saved.

[0006]

1 is a schematic diagram of a system according to a first embodiment of the present invention. In the figure, (1) is a boiler furnace, (2) is a drum, (3) is a boiler circulation pump, (4) is a circulation pump driving electric motor, (5) is a manifold, and (6) is a frequency converter, respectively. Boiler circulation pump of this embodiment (3)
The rotation speed can be changed by a frequency converter (6) added to the circulation pump driving electric motor (4).

FIG. 2 is a diagram showing the relationship between pump characteristics and rotational speed. When the rotational speed of the pump is reduced, the discharge amount and power are reduced accordingly. Utilizing this, as shown in FIG. 3, the pump rotation speed is changed to a rotation speed capable of ensuring the required minimum circulation ratio according to the boiler load, as shown in FIG. The pump rotation speed is controlled by program control as shown in the lower diagram of FIG. FIG. 5 shows an example of the control circuit.

FIG. 6 is a schematic diagram of a system according to a second embodiment of the present invention. In the figure, (7) shows a boiler evaporation pipe, and (8) shows a fluid coupling. Other reference numerals are the same as the reference numerals in FIG.

In this embodiment, a fluid coupling (8) is provided between the boiler circulation pump (3) and the circulation pump driving electric motor (4), whereby the rotation speed of the boiler circulation pump (3) is changed. There is. Other configurations and operations are similar to those of the first embodiment.

FIG. 7 is a block diagram of a system according to a third embodiment of the present invention. In the figure, (9) shows an enthalpy meter. The other reference numerals are the same as those shown in FIG.

In the present embodiment, a boiler having a circulation ratio feedback obtained from the furnace outlet enthalpy measured by the enthalpy meter (9) as shown in FIG. 8 is used as a boiler as shown in FIG. The rotation speed of the circulation pump (3) is controlled to reduce power. That is, the circulation ratio is estimated from the can water enthalpy measured at the outlet of the furnace, and the number of boiler circulation pumps (3) is controlled using a computing unit so that the circulation ratio will be in accordance with the heat load of the furnace. Figure 10
Shows an example of the control circuit.

[0012]

According to the present invention, the circulation pump rotation speed of the forced circulation boiler is variable, and the circulation pump rotation speed is controlled based on the boiler load or the boiler water enthalpy at the furnace outlet. It becomes possible to change the discharge amount according to the load, and it is possible to save power.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a system according to a first embodiment of the present invention.

FIG. 2 is a conceptual diagram showing the relationship between the discharge amount and discharge pressure of a pump and the pump rotation speed.

FIG. 3 is a correlation diagram of a minimum required circulation ratio and a constant speed pump or a variable speed pump.

FIG. 4 is a diagram showing a logic of an arithmetic unit for obtaining a required rotation speed from a boiler load.

FIG. 5 is a diagram showing an example of a control circuit in the first embodiment.

FIG. 6 is a schematic diagram of a system according to a second embodiment of the present invention.

FIG. 7 is a schematic diagram of a system according to a third embodiment of the present invention.

FIG. 8 is a correlation diagram between the enthalpy of the furnace outlet and the circulation ratio.

FIG. 9 is a diagram showing a logic of a computing unit that obtains a required circulation ratio from a boiler load and controls a pump rotation speed via a furnace outlet enthalpy.

FIG. 10 is a diagram showing an example of a control circuit in the third embodiment.

[Explanation of symbols] (1) Boiler furnace (2) Drum (3) Boiler circulation pump (4) Circulation pump drive motor (5) Manifold (6) Frequency converter (7) Boiler evaporation pipe (8) Fluid coupling ( 9) Enthalpy meter

Claims (2)

[Claims] 1. A boiler comprising: a circulation pump having a variable rotation speed, which is provided in the forced circulation boiler; and an arithmetic unit for controlling the rotation speed of the circulation pump based on the load of the forced circulation boiler. Circulation pump controller. 2. A circulation pump having a variable rotation speed provided in a forced circulation boiler, means for measuring a can water enthalpy at a furnace outlet of the forced circulation boiler, and a rotation speed of the circulation pump based on the can water enthalpy. A controller for a boiler circulation pump, comprising: