JPS63131904A - Method of controlling number of boiler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a simple and inexpensive method for controlling the number of boilers in which combustion control is ON-OFF control or three-position control (described later) when a large number of boilers are installed; More specifically, the present invention relates to a method for controlling the number of boilers that corresponds to the total load by operating a number of boilers commensurate with the load, and that does not start or stop two boilers at the same time.

[Conventional technology]

When a single boiler is used to cope with boiler load fluctuations, thermal efficiency deteriorates when the load becomes low. Generally, the higher the load, the better the thermal efficiency. For this reason, when many small-capacity boilers are installed and the overall load becomes small, some of the boilers installed with multiple boilers are stopped and the minimum number of boilers is operated to cover the overall load. In recent years, a method of controlling the number of boilers installed with multiple boilers, which maintains the load of the boiler as high as possible and operates the boiler in a state with good thermal efficiency, has been attracting attention in recent years.

To explain the system of one three-position control steam boiler using the block diagram in Figure 3, 7 indicates the steam to be supplied,
The steam pressure is supplied to the pressure switch 1, and an electrical signal 5 indicating whether it is below or above a certain set pressure is transmitted to the control word W2, and either the high twist burner 3a and the low salt burner 3b are burned, or the low salt burner The control device 2 judges and determines whether only the burner 3b is to be burned or both are to be stopped, and the high twist burner and the low salt burner are to be burned or stopped accordingly.

It is burned in a high-twist burner/low-salt burner, and the generated heat 6 is transferred to water through a heat transfer section 4, and steam is supplied.

A conventional number-of-units control system will be explained using FIG. 4 for, for example, four units. Each boiler is named N011 to N0.4, and the system inside the dashed-dotted line is exactly the same as in Fig. 3. 8 in the figure is a steam pipe that collects steam from each boiler and supplies it to the load, and a pressure switch 9 is provided downstream from where all the steam from all the boilers is collected.

In response to this signal from the pressure switch 9, the number control device 10
determines whether each boiler should be turned on or off, and transmits the start or stop of each boiler to each boiler using a signal 11 to control the number of boilers.

[Problem that the invention seeks to solve]

However, in the case of the above-mentioned multi-boiler installation, it is necessary to install an expensive pressure switch 9, and since there is always a pressure loss when steam flows through the steam pipes, the pressure transmitted to the pressure switch 9 and the pressure of each boiler are The pressure transmitted to the switch 1 is different from one boiler to another. For this reason, it is difficult to set the pressure switch 1 of each boiler by taking into account the difference in pressure loss in the steam pipes, and there is also the drawback that if the settings are incorrect, the number of boilers cannot be controlled properly.

The present invention was made in view of the above points, and by knowing the load of each boiler with respect to the overall load, it is possible to operate the number of boilers commensurate with the load, and two boilers can be operated at the same time.
The object of the present invention is to provide a method for controlling the number of boilers that can efficiently continue operating the boilers without starting or stopping each boiler.

[Means and effects for solving the problem] The method for controlling the number of boilers of the present invention is based on the method for controlling the number of boilers in which combustion control is ON-OFF control or three-position control in a system in which a large number of boilers are installed. The combustion stop time is measured, and a signal indicating whether or not the time exceeds the set time, a signal indicating whether each boiler is operating, and a preset boiler start order are used in combination to When the ON time of the burner of the pre-boiler of a boiler is more than a certain value, that boiler is started, and when the OFF time of the burner of the boiler to be stopped is more than a certain value and there is a stop signal of the post-boiler, the boiler is started. It is characterized by stopping the boiler.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. However, unless there is a specific description, the shapes of the components described in this example, their relative positions, etc. are not intended to limit the scope of the present invention to these, but are merely illustrative examples. Only.

The configuration of the number-of-units control system according to the present invention will be explained for four units, for example, with reference to FIG. Each boiler is NO, 1~N
004, and within the dashed-dotted line, the system described for the NO31 boiler and the others N011 to N014 are the same, and are the same system as in FIG. 3. However, between the control device 2 and the high-twist burner 3a, a measuring device 12 for counting the ON time of the combustion device of the high-twist burner is provided, and between the control device 2 and the low-salt burner 3b, a measuring device 12 is provided for counting the ON time of the combustion device of the high-twist burner. A measuring device 13 is provided for counting the OFF time of the combustion device. Therefore, signals corresponding to the measurement time from the measuring devices 12 and 13 and high-twist burner/low-salt burner operation instruction signals from the control device 2 are transmitted to the number control device 10, and the number control device 10 receives the number control signal. is transmitted to each boiler by a signal 11, and the number of boilers is controlled.

When multiple boilers are installed, the combustion amount of each boiler is adjusted by ON-OFF control or three-position control according to the hot water temperature in the case of a hot water boiler or the steam pressure in the case of a steam boiler. Since the ON-OFF control and the three-position control are basically the same, the three-position control will be explained below as an example.

A burner with three-position control burns at a combustion amount in three positions: maximum load, intermediate load, and stop, but for the sake of explanation, a low salt burner 3b and a high-twist burner 3a are incorporated, and each burner has a predetermined combustion amount. When both the high-twist burner 3a and the low-salt burner 3b burn, when the high-twist burner 3a stops and only the low-salt burner 3b burns, the high-twist burner 3a burns.
, three-position control is performed when both low-salt burners 3b are stopped. There are several methods of three-position control burner, but
Basically the same thing.

Figure 2 shows the relationship between the boiler load, burner ignition time (ON time) and extinguishing time (OFF time) of a three-position control boiler with a low salt burner capacity of 40% and a high twist burner capacity of 70%. It is something that

As can be seen from Figure 2, when the boiler load is between 0 and 40%, the low salt burner is ON-OFF, and as the load increases, the ON time becomes longer, the OFF time becomes shorter, and finally The low salt burner will not turn on when the boiler load is 40%. The opposite is true when the load decreases.

Then, when the load exceeds 40%, the high-twist burner also ignites,
As the boiler load increases, the ON time becomes longer than the OFF time, and at 110%, the high-twist burner also stops turning on. When the load decreases, the opposite occurs.

Such boiler load and burner ON/OFF at that time
The relationship with time can be easily calculated from the unique characteristic value of the boiler (referred to as boiler time constant) and the capacity of the burner, and can also be determined experimentally. Since the ON/OFF time of the burner is uniquely determined by the load on the boiler, by knowing this time, it is possible to know the status of the load on the boiler.

Now, an example will be explained in which four boilers are installed. Boilers are divided into boilers that are operated at a fixed maximum load (high-twist burner and low-salt burner are both burning) and boilers that control the load to match the overall load. To simplify the explanation, it is assumed that among the boilers in operation, only one boiler is controlled in three positions in response to the overall load, and the remaining boilers are fixed at the maximum load. This is done by a signal from the number control device 10.

As mentioned above, low salt burner 3b40%, high twist burner 3a7
When it is set to 0%, when the total load is 110% or more, it becomes the maximum load of the four joint ventures. According to the preset startup order, if the boiler stop order is N014→N013→N092→N011, if the overall load decreases, NO,
No. 3, No. 92, and No. 1 are fixed at the maximum load, but No. 4 boilers are controlled in three positions by the signal from the pressure switch 1 as load control. As the overall load decreases, the N014 boiler turns on and off the high twist burner 3a.
The FF alone cannot cope with this problem, and the high-twist burner 3a is stopped and the low-salt burner 3b is turned on and off. N
When the low-salt burner 3b OFF time of the 014 boiler exceeds a certain set value, the number control device 10 receives a signal from the measuring device 13 of the NO, 4 boiler, and the N094 boiler is stopped by the signal 11. The N011 boiler, NO, 2 boilers are fixed at the maximum load, and the NO, 3 boiler corresponds to the overall load. Therefore, when the pressure switch 1 signal is used to control the three positions, when the A0 overall load further decreases, the N013 boiler's The OFF time of the salt burner has exceeded a certain set value (signal from the measuring device 13 of the NO, 3 boiler), and the stop signal of the boiler after the NO, 3 boiler, that is, the N014 boiler (the signal from the NO, 4 boiler) signal from the control device 2), the number control device 10 outputs NO, 3 by the signal 11.
Stop the boiler. Thereafter, as the overall load decreases, the NO, 2 boiler is stopped, and only the NO, 1 boiler responds to the entire load using the same procedure. As the total load increases, N
The low-salt burner 3b of the O.1 boiler continues combustion, and the high-twist burner 3a is turned on and off, and the ON time of the high-twist burner 3a becomes longer.

When the ON time of the high-twist burner 3a exceeds a certain set value, the signal from the measuring device 12 of the No. 1 boiler determines the No.
,2 boilers are started and operated. The NO11 boiler is fixed at the maximum load, and the NO and 2 boilers are controlled in three positions by the pressure switch 1 of the NO12 boiler to correspond to the total load. When the ON time of the high twist burner 3a of the No. 2 boiler exceeds a certain set value, the measuring device 12 of the No. 2 boiler
The N093 boiler is started and operated by the signal. Thereafter, as the total load increases, the NO.4 boiler is started and operated in the same manner.

As described above, when the ON time of the high-twist burner of the pre-boiler of the boiler to be started exceeds a certain value, the boiler is started.

(2) When the OFF time of the low-salt burner of the boiler to be stopped is longer than a certain value and a stop signal for the downstream boiler is generated, the boiler is stopped.

By doing so, the number of operating boilers can be automatically increased or decreased in response to changes in the total load.

〔Effect of the invention〕

As explained above, according to the method of the present invention, by using a simple device 12 or 13 that issues a signal when the ON time or OFF time of a combustion device exceeds a certain set value, an inexpensive number control device can be used. can provide,
In addition, while operating the load control boiler corresponding to the overall load, the number of boilers is increased or decreased by checking the load of the boiler itself, which has the effect of reducing the range of changes in the hot water temperature or steam pressure supplied. be.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an example of a device implementing the boiler number control method of the present invention, and Fig. 2 shows a three-position control burner system in which the capacity of the low-salt burner is 40% and the capacity of the high-twist burner is 70%. Figures 3 and 4 are block diagrams showing the conventional boiler number control system. It is.

Claims (1)

[Claims] 1. In a device installed with multiple boilers whose combustion control is ON-OFF control or three-position control, the combustion operation time and combustion stop time of each boiler are measured, and a signal indicating whether or not the time exceeds the set time is generated. , the burner of the preboiler of the boiler to be started is turned on based on the combination of the signal indicating whether each boiler is operating or not and the preset boiler startup order.
The boiler is started when the time exceeds a certain value, and the boiler is stopped when the OFF time of the burner of the boiler to be stopped is above a certain value and there is a stop signal of the downstream boiler. How to control the number of boilers.