JPH086889B2 - Boiler number control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention provides a simple and inexpensive unit control method when a large number of boilers are installed in which the combustion control is ON-OFF control or three-position control (described later). More specifically, the present invention relates to a method for controlling the number of boilers in which the total load is handled by operating the number of boilers commensurate with the load, and the two boilers are not started or stopped at the same time.

[Conventional technology]

When one boiler responds to the load fluctuation of the boiler,
When the load becomes low, the thermal efficiency becomes poor. Generally, the higher the load, the better the thermal efficiency. For this reason, when a large number of small capacity boilers are installed and the overall load becomes small, some of the boilers installed with multiple cans are stopped, and the minimum number of boilers that can be operated corresponds to the total load. In recent years, a number-of-units control system with multiple cans installed, which keeps the load of the boiler as high as possible and operates the boiler in a state of good thermal efficiency, has been receiving attention in recent years.

Explaining the system of one three-position control steam boiler with the block diagram of FIG. 3, the steam supplied by 7 is shown, and its steam pressure is supplied to the pressure switch 1 and is below a certain set pressure. The above electric signal 5 is transmitted to the control device 2 to burn both the high-burn burner 3a and the low-burn burner 3b.
The control device 2 judges and decides whether to burn only the low-burn burner 3b or to stop both of them, and the high-burn burner / low-burn burner burns or is stopped accordingly.

The amount of heat generated by combustion with high-burn burners and low-burn burners 6
Is transferred to the water through the heat transfer unit 4, and steam is supplied.

A conventional number control system will be described with reference to FIG. 4 for four units, for example. The boilers are named No.1 to No.4, and the inside of the one-dot chain line is the same system as in Fig. 3. 8 in the figure
Is a steam pipe that collects steam from each boiler and supplies it to the load.
A pressure switch 9 is provided in the wake of collecting all the steam of all boilers. Upon receiving the signal from this pressure switch 9,
The number-of-units control device 10 judges the start / stop of each boiler and determines it, and transmits the start / stop of each boiler to each boiler by a signal 11 to control the number of units.

[Problems to be Solved by the Invention]

However, in the case of a multi-can installation of steam, it is necessary to provide an expensive pressure switch 9, and when steam flows through the steam pipe, there is always a pressure loss, so the pressure transmitted to the pressure switch 9 and the pressure of each boiler are The pressure transmitted to the switch 1 is different for each boiler. For this reason, it is difficult to set the pressure switch 1 of each boiler in consideration of the pressure loss difference in the steam pipe, and if the settings are incorrect, the number of units cannot be controlled properly.

The present invention has been made in view of the above points, and by knowing the load of each boiler with respect to the total load, it is possible to operate the number of boilers commensurate with the load, and simultaneously start two boilers. Another object of the present invention is to provide a boiler number control method capable of efficiently continuing the operation of a boiler without stopping it.

[Means and Actions for Solving the Problems]

In the boiler number control method of the present invention, the combustion control is ON-OFF.
In a device with multiple boilers installed that is controlled or three-position control, the continuous ON time of the burner for which a combustion instruction is issued for each boiler, that is, the ON time per operation, the burner for which a combustion stop instruction is issued A continuous OFF time, that is, an OFF time per measurement is measured, a signal indicating whether or not the time exceeds a set time, and a signal indicating whether or not each boiler is operating,
Depending on the combination with the preset boiler starting order, when the boiler on-time of the boiler to be started exceeds a certain value, the boiler should be started and turned off. The above is characterized in that the boiler is stopped when there is a stop signal for the rear boiler.

The burner repeats combustion and stop, but when the load increases, the time for continuous combustion becomes longer and the time for continuous stop becomes shorter. In the present invention, this is utilized, and the ON time per time is called continuous ON time, and the OFF time per time is called continuous OFF time.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. However, the shape of the constituent devices described in this embodiment, the relative arrangement thereof, and the like, unless otherwise specified, are not intended to limit the scope of the present invention only to them, and are merely illustrative examples. Only.

The configuration of the number-of-units control method according to the present invention will be described for four units, for example, with reference to FIG. No.1 to No.4 of each boiler
Within the chain line, the system described in No. 1 boiler and other No. 2 to No. 4 are the same, and they are the same system as in Fig. 3. However, a measuring device 12 for counting the continuous ON time of the combustion device of the high-burn burner is provided between the control device 2 and the high-burn burner 3a, and the control device 2 and the low-burn burner are provided.
A measuring device 13 for counting the continuous OFF time of the combustion device of the low-burner burner is provided between the measuring device 13 and 3b. For this reason,
A signal corresponding to the measurement time from the measuring devices 12 and 13 and the operation instruction signal of the high-burn burner / low-burn burner from the control device 2 are transmitted to the number-of-units control device 10, and the number-of-units control signal is transmitted to each boiler by the number of units control device 10. Signal 11 to control the number of vehicles.

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

The three-position control burner burns at three positions: maximum load, intermediate load, and stop.However, for the sake of explanation, a low-burn burner 3b and a high-burn burner 3a are installed and each has a specified burn rate. In the burner that burns, the high-burn burner 3a stops when the high-burn burner 3a and the low-burn burner 3b both burn, and the high-burn burner 3a burns only when the low-burn burner 3b burns.
Three-position control when both 3b stop. There are several types of three-position control burners, but they are basically the same.

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

As can be seen from Fig. 2, when the boiler load is between 0 and 40%, the low-burn burner turns on and off, and as the load increases, it turns on.
The time becomes longer, the OFF time becomes shorter, and finally the low-burn burner remains on when the boiler load is 40%. The opposite is true when the load decreases.

Next, when the load exceeds 40%, the high burner also ignites,
As the boiler load increases, the ON time gradually becomes longer than the OFF time, and at 110%, the high-burn burner remains on. The opposite is true when the load decreases.

The relationship between the boiler load and the ON-OFF time of the burner at that time can be calculated easily from the characteristic value of the boiler (called the boiler time constant) and the capacity of the burner. You can also ask. Since the ON / OFF time of this burner is uniquely determined with respect to the load of the boiler, it is possible to know the load condition of the boiler by knowing this time.

Now, a case where four boilers are installed will be described as an example. A boiler that fixes the operating boiler to the maximum load (state in which both high-burn burner and low-burn burner are burning),
It is divided into a boiler that controls the load to match the total load. For simplification of description, it is assumed that only one can among the operating boilers is controlled in three positions corresponding to the total load, and the remaining boilers are fixed to the maximum load. This is performed by a signal from the number control device 10.

As mentioned above, if the low-burner burner 3b is 40% and the high-burner burner is 3a 70%, if the total load is 110% or more, all four units have the maximum load. According to the preset boot order, N
o.4 → No.3 → No.2 → No.1 is the boiler stop order,
No.3, No.2, and No.1 are fixed to the maximum load when the total load is reduced, but the No.4 boiler is controlled in three positions by the signal of the pressure switch 1 as load control. The No. 4 boiler turned on the high-burn burner 3a as the total load decreased.
The high-burn burner 3a stops, and the low-burn burner 3b turns on and off. No.4 Boiler low burner 3b When the OFF time 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 signal 11 causes the No. 4 boiler to stop. The No. 1 boiler and the No. 2 boiler are fixed to the maximum load, and the No. 3 boiler corresponds to the total load, so three positions are controlled by the signal of the pressure switch 1. When the overall load goes down,
The OFF time of the low-burner burner of the No.3 boiler exceeded a certain set value (signal from the measuring device 13 of the No.3 boiler), and the post-boiler of the No.3 boiler, that is, the No.4 boiler. With the stop signal (the signal from the control device 2 of the No. 4 boiler), the number control device 10 stops the No. 3 boiler by the signal 11.
Following the same procedure, as the total load decreases, the No. 2 boiler is stopped, and only the No. 1 boiler responds to the total load. As the total load increases, the low-burn burner 3b of the No. 1 boiler continues to burn and the high-burn burner is turned on and off to respond, and the ON time of the high-burn burner 3a becomes longer. When the ON time of the high burner 3a exceeds a certain set value, the measuring device of No.1 boiler 12
The No. 2 boiler is started and operated by the signal. The No. 1 boiler is fixed to the maximum load, and the No. 2 boiler is controlled in three positions by the pressure switch 1 of the No. 2 boiler to handle the entire load. When the ON time of the high burner burner 3a of the No. 2 boiler exceeds a certain set value, the signal from the measuring device 12 of the No. 2 boiler
No.3 Start the boiler and operate it. Following the same procedure, the No. 4 boiler is started and operated as the total load increases.

As described above, with respect to the increase / decrease in the total load, (1) the high combustion burner of the front boiler of the boiler to be started
When the ON time is over a certain value, the boiler is started.

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

By doing so, the number of operating boilers can be automatically increased or decreased with respect to the increase or decrease of the total load.

〔The invention's effect〕

As described above, according to the method of the present invention, when the continuous ON time or the continuous OFF time of the combustion device is equal to or more than a certain set value, a simple device 12 or 13 for outputting a signal is used, which is inexpensive. To control the number of boilers while increasing the number of boilers while checking the load of the boiler while operating the load control boiler corresponding to the total load. The effect is that the change width of can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of an apparatus for carrying out the method for controlling the number of boilers of the present invention, and FIG. 2 is a three-position control burner system in which a low burner capacity is 40% and a high burner capacity is 70%. % Boiler load and burner ignition time (ON
Time) and fire extinguishing time (OFF time), and FIGS. 3 and 4 are block diagrams showing a conventional boiler number control system. 1 ... Pressure switch, 2 ... Control device, 3a ... High burner burner, 3b ... Low burner burner, 4 ... Heat transfer section, 5 ... Electric signal, 6 ... Generated heat amount, 7 ... Supply steam , 8 ... steam pipe,
9 ... Pressure switch, 10 ... Unit control device, 11 ... Signal, 12, 13 ... Measuring device

Claims (1)

[Claims] 1. In an apparatus in which multiple boilers are installed, in which combustion control is ON-OFF control or three-position control, continuous ON time of a burner for which a combustion instruction for each boiler is issued, and a combustion stop instruction are issued. Start the burner by measuring the continuous OFF time of the burner and combining the signal indicating whether the time has exceeded the set time, the signal indicating whether each boiler is operating, and the preset starting order of the boiler. When the ON time of the boiler front burner of the boiler should be over a certain value, start the boiler,
When the OFF time of the boiler burner to stop is more than a certain value,
A method for controlling the number of boilers, characterized in that the boiler is stopped when there is a stop signal for the rear boiler.