JPH0217302A - Automatic control device for the number of boilers - Google Patents

Abstract

PURPOSE:To improve a load responding speed by a method wherein a contact point to be opened or closed with a pressure signal from a pressure sensor is arranged in parallel with another contact point to be opened or closed with a combustion instruction signal from a controller for use in controlling the number of devices and a combustion control solenoid valve is opened when either one of the contact points is closed. CONSTITUTION:A combustion control of a boiler is carried out by controlling an opening or a closing of a high combustion control solenoid valve VH and a low combustion control solenoid valve VL. A combustion control contact point X1 and a high combustion control contact point X2 are provided as contact points which are closed under a combustion instruction signal from the controller for controlling the number of devices, the contact point X1 is closed under the low combustion instruction, both contact points X1 and X2 are closed together under a high combustion instruction and they are opened together under an instruction of stoppage. A low setting pressure contact point SL is operated with an output from a pressure sensor (not shown) and a high combustion solenoid valve VH is operated when the combustion control contact point X1 is closed and either the contact X2 or SL is closed. A high setting pressure contact point SH is operated under a safe controlling pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a multi-can installation system for a boiler that improves response speed to a load.

[Conventional technology]

As is well known, in a multi-boiler installation system where multiple boilers are installed, a pressure detector is installed in the steam header to grasp the load condition and determine the required number of boilers according to a preset startup order according to the load amount. An automatic number control system is adopted in which the boilers are sequentially switched to combustion, and if there are load fluctuations, the boilers are fired or stopped in accordance with the load fluctuations to follow the load.

For example, if three three-position control boilers (NO, 1-NO, 3) are installed, which control combustion in three positions: high combustion state 9iH, low combustion state L, and stop state, this method is shown in Fig. 8. The number of steam generators is controlled as shown in the graph, and the control pressure is divided into seven steam pressure zones a- and =H, and the number of steam generators is controlled in accordance with each steam pressure zone. In other words, in the lower limit steam pressure zone a, all cans are in a state of high combustion (
HHH), and as the steam pressure increases, HHH
→ HHL → HH-HL-HL-L and then stop.
In the upper steam pressure zone g, all the vessels are stopped.

When the steam pressure decreases, the cans are activated in the reverse order.

[Problem to be solved by the invention]

However, the above automatic number control method has the following problems.

When the load is low, some boilers are stopped and on standby, but if the standby time is too long, the boilers will be cooled by heat radiation and the pressure inside the boiler will drop.

In this case, when the load suddenly increases, the steam pressure in the steam header decreases significantly because the steam header cannot fully respond to the load. In other words, if the pressure inside the can is too low due to cooling, it will take too long to raise the pressure to a predetermined pressure even if combustion is started, making it impossible to respond quickly to the load.

On the other hand, when using a single boiler (not in a multi-boiler installation), combustion is controlled by the signal from the pressure switch connected to the boiler. Control is performed so that combustion is high when the steam pressure in the can is below the low set pressure, low combustion when it is above the low set pressure and below the high set pressure, and stopped when the steam pressure is above the high set pressure. In the can installation system, the pressure in the steam ladder is used to control combustion as described above, so a pressure switch is not used directly.

As an example of how to use these pressure switches, as shown in the circuit diagram of Fig. 7, the high set pressure contact SH and the combustion control contact Xi of the number controller are connected in series, and the low set pressure contact SL and the number controller are connected in series. High combustion control contact
kg/cdG), it only has the function of a safety device that opens a contact and stops combustion when the pressure inside the can increases abnormally.

[Means to solve the problem]

In view of the above-mentioned problems, this invention performs backup combustion in a predetermined boiler based on a signal from a pressure sensor provided in each boiler, thereby further improving the response speed to the load.

That is, in this invention, a plurality of boilers are installed, a ladder is provided in each of these boilers to connect the steam separately, the internal pressure of this header is converted into an electric signal using a pressure detector, and the signal is used to generate an electric signal according to the amount of load. A number controller is installed to fire and stop the required number of boilers, and each of the multiple boilers is equipped with a pressure sensor to detect the pressure inside the boiler and a combustion control electromagnetic device to control the supply of fuel to the boiler. A valve is provided, and a contact that opens and closes in response to a combustion instruction signal from the number controller is connected in series to the combustion control solenoid valve, and when the contact is in a closed state, the combustion control solenoid valve is in an open state. In the control circuit, a contact that opens and closes at a predetermined pressure according to a pressure signal from the pressure sensor is connected in parallel with the contact, and when either of these contacts is in a closed state, the combustion It is characterized in that the control solenoid valve is configured to be in an open state.

[Effect]

In the above configuration, contact 04), which opens and closes according to the combustion instruction signal from the number controller, and contact 0ω, which opens and closes at a predetermined pressure according to the pressure signal from the pressure sensor, are connected in parallel, and either contact Since the combustion control solenoid valve is configured to be open when the boiler is closed, if the pressure inside the boiler is below the set pressure, the boiler will be in the combustion state even if there is no combustion instruction signal from the unit controller. This makes it possible to set the boiler to a high combustion state when a low combustion instruction is issued from the number controller. By doing so,
It is possible to keep the boiler always on standby at a constant pressure, and to shorten the time required to raise the pressure to a constant pressure when the pressure drops.

〔Example〕

In the figure, (1) is the boiler, and the following are three boilers (NO, 1 to N
083), each boiler is provided with an operation control device 00 and a combustion device 021. 03 is a pressure sensor for detecting the pressure inside the boiler can. Each boiler is connected to a common steam header (2) by a steam pipe (5) inserted with a check valve (6). This steam lug is equipped with a pressure detector (3) that detects the internal steam pressure, and based on the pressure detection signal, the number controller (4) controls combustion and shutdown of each boiler. It is supposed to be done. When the combustion control signal is issued from the number controller to each boiler, the order in which the boilers are activated follows a preset order.

(7) is a combustion supply line connected to the combustion device 021, in which the downstream side of the fuel pump (9) is divided into two thread paths, and each thread path is connected to a combustion control solenoid valve (8). ) is inserted. VH indicates a high combustion control solenoid valve, and VL indicates a low combustion control solenoid valve. Boiler combustion control is performed by opening and closing these solenoid valves. That is, when the low combustion control solenoid valve VL is open and the high combustion control solenoid valve VO is closed, the combustion state is low, when both solenoid valves are open, the combustion state is high, and when both solenoid valves are idle, the combustion state is stopped.

A combustion control contact Xi and a high combustion control contact X2 are provided as contacts that are closed by a combustion instruction signal from the number controller. When the low combustion instruction signal is output from the number controller, only the contact x1 is closed, and when the high combustion instruction signal is output, both the contact Xi and the contact x2 are closed. When a stop command is given, both contacts are open.

SH is a high set pressure contact, SL is a low set pressure contact, the high set pressure contact SH opens when the high set pressure is higher than the high set pressure, and closes when the lower set pressure is lower, and the low set pressure contact SL opens when the lower set pressure is higher than the low set pressure. It is in the closed state. Among these set pressures, the low set pressure is the pressure set for performing backup combustion control in the present invention, and is usually set to a value slightly lower than the control pressure in the ladder for steam. The high set pressure is the so-called safety control pressure, and is set at a higher value than the control pressure in the steam header to cut combustion in the boiler if the pressure inside the can increases abnormally for some reason. As the pressure sensor zero, one pressure sensor may be used and the output signal may be emitted at each of the high set pressure and the low set pressure, but as shown in FIG. Two pressure switches, a switch H and a low set pressure switch L, may be provided to set a high set pressure and a low set pressure, respectively. In addition, for the opening/closing operation of the contact at the set pressure, a slight differential is provided between the opening operating pressure and the closing operating pressure.

In the embodiment shown in FIG.
As such, a low set pressure contact SL is provided, and this low set pressure contact SL and two high combustion control contacts are connected in parallel. By doing so, when the combustion control contact x1 is in the closed state, if either the contact SL or x2 is closed, the high combustion control solenoid valve VH is energized and the boiler enters the high combustion state. 0ω indicates an AC power source.

FIG. 4 shows the relationship between the steam pressure and the combustion state of the boiler in the embodiment of FIG. 3, focusing on changes in the combustion state of the N003 boiler. The normal control pressure in the steam header is approximately 7 to 8 kg / cd G, high setting pressure 9kg
/cdG, and set the low set pressure to 6.6kg/cdG. The solid line represents the pressure inside the steam header, and the dashed line represents NO6.
Shows the internal pressure of 3 boilers. In this example, the control pressure is divided into seven steam pressure zones a - g, and the number of units is controlled in accordance with each steam pressure zone, but in the lower limit steam pressure zone a, all cans are in a state of high combustion (HHH). Yes, as the steam pressure increases, HHH-+HHL-4HH→HL
It stops like -4H→L, and the upper steam pressure zone g
In this case, all chains are stopped. Then, when the steam pressure decreases, it starts up in the reverse order of the above, so,
Normally, the steam pressure zone is in the HHL state, but according to the circuit configuration shown in Figure 3, the NO63 boiler is in the HHL state if the internal pressure is below the low set pressure (6.6 kg/cdG). Becomes in a state of combustion.

If the boiler reaches high combustion support, it is the same as before, but if low combustion support occurs, and the steam pressure falls below the low set pressure due to long boiler standby times, the combustion control contact Since XI is closed and the low set pressure contact SL is also closed, the boiler shifts to high combustion. Then, when the steam pressure rises and exceeds the low set pressure, the low set pressure contact opens and transitions to low combustion. Therefore, the time required to increase the pressure to a constant pressure when the pressure decreases is improved.

In another embodiment shown in FIG. 5, a relay Oe is connected in series with the low set pressure contact SL, and the normally open contact X3 of this relay is
is connected in parallel with contact XI, and another normally open contact x3° of the same relay is connected in parallel with contact x2. The contact 0ω that opens and closes at a predetermined pressure based on the signal from the pressure sensor side is the contact X3. Therefore, if the pressure inside the boiler can is below the low set pressure, the low set pressure contact SL is in the closed state, relay 00 is energized and its contact X3. The state shifts to a high combustion state regardless of the combustion instruction signal from the number controller.

FIG. 6 shows the relationship between the steam pressure and the combustion state of the boiler in the embodiment shown in FIG. 5, focusing on changes in the combustion state of the N083 boiler. The low set pressure is the same as in the previous embodiment. Therefore, originally, in the steam pressure zone d, H
L and steam pressure zone C should be in the HH state, but according to the circuit configuration shown in Figure 5, the N003 boiler has a low internal pressure (6.6 kg/d G).
) A high combustion state occurs when: That is, according to the circuit configuration shown in FIG. 5, it is possible to always stand by at a constant pressure.

〔Effect of the invention〕

Since the present invention has the above-described configuration, it is possible to increase the response speed to a load and prevent a significant drop in steam pressure. That is, in the control circuit, by connecting in parallel a contact that closes when the pressure inside the can is below a preset value and a contact that closes when a combustion instruction signal is sent from the number controller. , set the boiler that has received a low combustion instruction from the number controller to a high combustion state to shorten the pressure rise time, or set the boiler to a combustion state regardless of the combustion instruction from the number controller to maintain a constant combustion state. It becomes possible to wait under pressure. Therefore, the necessary steam pressure can be ensured and the equipment on the load side can be used with peace of mind. In addition, since it can be implemented by using the existing pressure switch in the boiler and simply modifying the external wiring, a large practical effect can be obtained with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram showing an embodiment of the boiler multi-can installation system according to the present invention, FIG. 2 is a block diagram showing a part of FIG. 1 in detail, and FIG. A circuit diagram of one embodiment; FIG. 4 is a graph showing changes in the combustion pattern of the boiler with changes in steam pressure in the circuit diagram of FIG. 3; FIG. 5 is a circuit diagram of another embodiment of the present invention; FIG. is a graph showing changes in boiler combustion pattern due to changes in steam pressure in the circuit diagram of Figure 5, Figure 7 is a circuit diagram of a conventional automatic unit control system, and Figure 8 is a graph showing changes in steam pressure in the circuit diagram of Figure 7. 3 is a graph showing changes in the combustion pattern of the boiler due to (1)...Boiler (3)...Pressure detector (13)...Pressure sensor

Claims (1)

[Claims] A plurality of boilers (1) are installed, a common steam header (2) is provided for these boilers, and the internal pressure of this header is converted into an electric signal by a pressure detector (3) and taken out. A number controller (4) is provided which fires and stops the required number of boilers according to the load based on a signal, and each of the plurality of boilers (1) is equipped with a pressure sensor (13) that detects the pressure inside the can. A contact (14) is provided with a combustion control solenoid valve (8) that controls the supply of fuel to the boiler, and is opened and closed by a combustion instruction signal from the number controller.
is connected in series to the combustion control solenoid valve, and the contact (14
) is in a closed state, the combustion control solenoid valve (8) is in an open state; 14) in parallel, and is configured such that when either one of these contacts is in a closed state, the combustion control solenoid valve is in an open state.