JPS633201B2 - - Google Patents

Description

[Detailed Description of the Invention] Traditionally, multiple boilers have been used in steam power plants in consideration of load conditions and boiler handling problems, but in recent years, small-sized and It is becoming a global trend to install and use many small-capacity boilers. This is due to the development of small boilers with high reliability and extremely high thermal efficiency in various countries.In Japan, highly efficient small once-through boilers have also been developed, and this multi-can installation method has gained attention. This led to him being bathed in water.

However, little attention has been paid to methods for controlling a large number of boilers in an integrated manner, and standard automatic control devices are currently being used as they are.

A common way to control multiple boilers is to use one pressure controller to adjust the pressure of all boilers, but since all boilers are operated at the same time, this method is inefficient at low loads. This has the disadvantage that all cans have the same ON-OFF point, which increases the starting current (causing element damage or malfunction), and since ignition occurs at the same time, When using a chimney, backfire etc. are likely to occur when igniting.

In order to improve this situation, each boiler should be equipped with a pressure controller, each boiler should be stopped in an orderly manner as the load decreases, and all boilers in operation should be operated at efficient high loads.
When trying to do this with a standard automatic control system, the steam pressure varies greatly depending on the load, even in the case of three boilers, within the range of P to P' as shown in Figure 1, and even more boilers are used. If a small tank is installed, the control width of the entire system becomes larger (setting difference of each pressure switch x number of units), and the fluctuation range of the steam pressure guided to the supply destination may exceed the allowable range and become unusable. It can happen.

Moreover, in the case where each boiler is equipped with a pressure controller, the order in which the boilers are started and stopped is fixed, so they may be turned on and off frequently depending on the load.
However, changing this order requires resetting the steam pressure, and if you want to stop or shut down the boiler, you must operate the pressure controller each time. .

The present invention has been made in view of the above-mentioned problems. For example, by applying a control device consisting of a low limit pressure switch and a high limit pressure switch connected to a steam header, the required number of steam headers can be controlled based on the internal pressure of the header. By controlling the operation of the boilers, and detecting and integrating the operating time of each boiler individually, the operating order of each boiler is prioritized starting from the one with the least operating time, according to the operating time of each boiler. The main idea is to make changes as appropriate to average out the operating time of all boilers.

In other words, this invention aims to improve the reliability of the entire system by controlling a large number of boilers in an integrated manner and averaging the operating time (total combustion time) of all boilers. It is. As means for controlling the operation of the boiler in this invention, it is possible to use a control method using a low limit pressure switch and a high limit pressure switch, which will be described in detail in the following embodiments, but this is not the only means. It is not limited to.

When this type of unit control method is used, the operating order of the boilers can be easily changed by dial operation, extending the life of the boiler and reducing the pressure control width. Various advantages are obtained as indicated.

An embodiment of the present invention will be described below regarding control of the number of three boilers. As shown in the step diagram for each half stage (half car) in Figure 2,
A three-position control system (ON-
OFF, low combustion, and high combustion control methods), the horizontal axis shows the load (the amount of steam in the entire boiler), and the vertical axis shows the operating status of each boiler in area A, and B The pressure change at the steam header outlet is displayed in the area. As is clear from this, for example, if the load is about 3 t/h of steam, the No. 1 boiler located at the front stage of the startup order will have high combustion, and the No. 2 boiler located at the next stage (second stage) will have a high combustion rate. High combustion and low combustion are repeated within a certain pressure control range, and the No. 3 boiler in the subsequent stage (in this example, the final stage) remains stopped. The starting order of the boilers here is No. 1 → No. 2 in the diagram.
→ Since it is No. 3, if No. 2 is used as the reference, the boiler that should be operated next based on the preset operating order, No. 3 is located in the latter stage, and No. 1 is in the previous stage. It turns out. However, as will be clear from the description below, the order can be changed arbitrarily, such as starting No. 1 boiler, then No. 3 boiler, and then No. 2 boiler, etc.
If necessary, start No. 1 and No. 2 at the same time,
Of course, it is possible to create a sequence such as activating only No. 3 next time.

(a) When the load increases Until the load increases to 1.0t/h, the boiler in the first startup order enters low combustion ON-OFF control, but
When the amount of steam exceeds 1.0t/h, high combustion-low combustion control is entered and the operating state (combustion state) corresponds to the increase in load, and even when the maximum steam amount (2.0t/h, that is, high combustion) is reached, the When the steam pressure decreases and reaches the low limit setting pressure P ₁ (increase/decrease in Figure 2 B), the low limit pressure switch operates and after a certain period of time, the second
The startup boiler starts up and restores steam pressure.
When the load increases further and the steam pressure drops again, the low limit pressure switch operates to start the third starting boiler after a certain period of time. In this case, the only boiler that follows the load is the third boiler that was started last, and the first and second boilers in the previous stage that were started before that are kept at maximum capacity in order to maintain efficient and stable combustion conditions. Fixed operation is carried out in the steam region.

(b) When the load decreases When the load decreases, the steam pressure in the steam header increases, but when this pressure reaches the high limit setting pressure P ₂ (decreasing area B in Figure 2). ,
If the pressure does not decrease within a certain period of time after activation of the high limit switch, the boiler that should be operated last, that is, the boiler located at the previous stage, is stopped based on the preset operating order. Similarly,
When the load further decreases, the boilers are stopped one after another according to a desired starting order set in advance, until the load reaches zero.

Next, the sequence of the embodiment of this invention will be described as the fourth example.
The explanation will be made based on FIGS. 5 and 6. The symbols in the diagram are as follows.

SW... All can operation switches T ₁ , T ₂ ... Combustion transition timer T ₃ , T ₄ ... Combustion stop timer T ₅ ... Reset timer X ₁ to X ₃ ... Combustion state maintenance keep relay X ₄ , X ₅ ... _Relay for pressure switch _{X 6 ... Relay} for combustion stop X ₇ ...Relay for combustion _transition Coil section of X ₁ R to _{X 3} R... Coil section on the reset side _of X ₁ to Boiler) SRS ₂ ... Thumb rotary switch for combustion order selection (No. 2 boiler) SRS ₃ ... Thumb rotary switch for combustion order selection (No. 3 boiler) M ₁ ... No. 1 boiler combustion - stop relay M ₂ ...No.2 Boiler combustion-stop relay M ₃ ...No.3 Boiler combustion-stop relay SW ₁ ...No.1 Boiler switch SW ₂ ...No.2 Boiler switch SW ₃ ...No.3 Boiler switch GL ₁ ... No. 1 boiler combustion lamp GL ₂ ... No. 2 boiler combustion lamp GL ₃ ... No. 3 boiler combustion lamp HM ₁ ... No. 1 boiler combustion time integration meter HM ₂ ... No. 2 Boiler combustion time integration meter HM ₃ ... No. 3 boiler combustion time integration meter PH ₁ ... No. 1 boiler high limit pressure switch PH ₂ ... No. 2 boiler high limit pressure switch PH ₃ ... No. 3 boiler High limit pressure switch In the circuit configuration shown in Figure 4, first, the switch
When the SW is turned on, timer T ₅ is energized, but during the set time, T ₅ 's time-limited operation a contact is OFF.
Relay X ₈ is also OFF, and the reset side X ₁ R to X ₃ R of relays X ₁ to X ₃ is energized by the b contact of X ₈ .
Keep relays _X1 - _X3 are reset. As a result, the a contacts of X ₁ to _{X 3} shown in FIG. 5 are turned OFF, relay X ₈ is energized after the set time of timer T ₅ , and the reset sides of keep relays X ₁ to _{X 3} are turned OFF.

When the steam header pressure is low and the low limit and high limit pressure switches are ON, relays X ₄ and X ₅ are activated through the PL and PH contacts.
It becomes ON, and relay X ₇ is activated through the a contacts of X ₄ and X ₅ .
is turned ON, and the b contacts of X ₄ and X ₅ are separated, and relay X ₆ is turned OFF. Then, X ₇
When the set side _X1S of keep relay _X1 is energized through the a contact of _X7 when it is ON, _X1 is set to the ON side. Here, the timer _T1 is energized through the a contact _X1 of _X1 , and the a contact _X1 in FIG. 5 is also opened.

The steam header pressure is low and the pressure switch
If the PL and PH contacts remain the same, the timer
After the set time of _T1 , the time-limited operation a contact of _T1 closes, and the set side _X2S of keep relay _X2 is energized.
Since X ₂ is set to the ON side, _the a contact of X ₂
is closed and timer _T2 is energized. on the other hand,
The a contact _X2 in FIG. 5 is also closed.

Furthermore, if the steam header pressure is low and both pressure switch PL and PH contacts are closed, the timer
After the set time of T ₂ , the time-limited operation a contact of T ₂ closes, and the set side X ₃ S of keep relay X ₃ is energized.
_X3 is set to the ON side. As a result, the a contact _X3 in FIG. 5 is also closed.

If the pressure in the steam header increases at any of the above-mentioned stages and the contacts of the low limit pressure switch PL open, relay _X4 turns OFF. Therefore, the a contact of _X4 is also open, and the relay
_X7 is turned OFF, the a contact of _X7 is opened, the current is no longer energized to the set side of each keep relay _X1 to _X3 , and _X1 to _X3 are maintained in their current state.

Furthermore, when the pressure rises and the contact of the high limit pressure switch PH is also open, _relay
turns OFF, the b contacts of X ₄ and X ₅ both close, relay X ₆ turns on, the a contact of X ₆ closes, the reset side X ₃ R of keep relay X ₃ is _energized , It becomes OFF, and the a contact of _X3 in Fig. 5 becomes open. Then, the b contact of _X3 is closed, and timer _T3 is energized. pressure switch
If both PH and PL remain open, the time-limited operation a contact of _T3 will close after the set time of _T3 , the reset side _X2R of keep relay _X2 will be energized, and _X2 will be
It becomes OFF. Furthermore, if the steam header pressure increases and both PH and PL contacts are open, X ₂
The timer _T4 is energized through the B contact of the timer T4, and after the set time, the time-limited operation A contact is closed, and the reset side _X1R of the keep relay _X1 is energized, so that _X1 is turned OFF. At the same time, the a contact point of _X1 in FIG. 5 is opened.

When the pressure in the steam header decreases and the high limit pressure switch PH is closed, relay _X5 is energized and relay _X6 is de-energized, keeping the circuit in this state.

Next, when the pressure decreases and the low limit pressure switch PL is also closed, relay _X4 is also energized, and relay _X7 is energized.

In this way, from the zero pressure level until the low-limit pressure switch is activated, the boiler is started up step by step in the direction of increase by the timer from the front stage to the rear stage according to the desired order (L area : increasing range). Further, from when the low limit pressure switch is activated until when the high limit pressure switch is activated, the boiler stops increasing and decreasing and performs equilibrium operation. (M area: equilibrium area). and,
At a level above the operating pressure of the high-limit pressure switch, the boilers are stopped in stages starting from the later stage in the direction of decrease using another timer in the opposite manner to the case of increasing the number of boilers described above (N area:
decreasing area).

Figure 5 shows the sequence of the combustion order selection circuit part of the number controller. In this sequence, _the operating current flowing through the combustion state maintenance _relays By switching the thumb rotary switches SRS ₁ to SRS ₃ arranged in the same number as necessary, it is possible to selectively supply the boiler relays M ₁ to _{M 3} that control the operating status of each boiler. When the thumb rotary switch SRS ₁ for combustion order selection is set to No. 1, when relay X ₁ is activated, No.
Boiler relay M ₁ is activated. In the same way, if the combustion order selection thumb rotary switch SRS ₂ is set to number 2, the No. 2 boiler relay M ₂ will be activated when relay X ₂ is activated.

As a result, as mentioned above, the operating order of each boiler can be freely changed by operating the dial of the thumb rotary switch. In place of the rotary switch described above, it is also possible to use a switching means that performs the same function of selecting the boiler starting order, such as a switching circuit that combines a plurality of switching elements, or a commercially available keyboard matrix device. Of course, the configuration of the thumb rotary switch is not limited to the example illustrated.

Figure 6 shows the sequence of the controller for each boiler. In this sequence, the contacts of the combustion-stop relays M ₁ , M ₂ , M ₃ of each boiler and the high limit pressure switch of each boiler are connected.
PH ₁ , PH ₂ , and PH ₃ are each connected in series.

In addition, each boiler is equipped with integrated totalizers HM ₁ , HM ₂ , HM ₃ for totalizing and detecting its own combustion time.
are installed, and these and the combustion lamps GL ₁ , GL ₂ , GL ₃ of each boiler are connected in parallel, respectively, as shown in FIG. As a result, it is possible to grasp the total combustion time of boilers in operation after a certain period of time has elapsed using each integral meter. With boilers, it becomes possible to change the operating order of each boiler for averaging purposes. In other words, using the operating time of each boiler as an indicator, for the next certain period,
By appropriately changing the starting order of the boilers so that the boilers with fewer boilers are operated preferentially, it is possible to operate and use all the boilers evenly.

As explained above, the present invention provides the following benefits compared to the conventional multi-can installation by incorporating the above-mentioned automatic number control method into the multi-can installation system.

It is possible to achieve an effect similar to tire rotation in a car, and the boiler operating order can be easily changed by manual operation of a dial like a thumb rotary switch connected to the control circuit. Boiler operation management can be carried out in a planned manner. Therefore, certain boilers often
This eliminates the inconvenience of turning the boiler on and off, improves the reliability and longevity of the boiler in the entire system, and greatly contributes to reducing management and maintenance costs.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram illustrating a control method using a standard type automatic control device in comparison with the present invention, and Fig. 2 is an explanatory diagram illustrating steam pressure and steam amount characteristics of each boiler in the number control method of this invention. , FIG. 3 is a flow sheet of the entire embodiment of this invention, and FIGS.
FIG. 6 is a sequence diagram of an embodiment of the present invention.

Claims (1)

[Claims] 1. By using a boiler number control means that operates to control the operation of the required number of boilers based on the internal pressure of the steam header, and an operating totalizer that individually detects and totals the operating time of the boilers,
The operation estimation is characterized in that the operating order of each boiler is appropriately changed according to the operating time of each boiler so that the boiler with the least operating time is operated preferentially, and the operating time of all the boilers is averaged. Automatic boiler number control system using a meter.