JPH0749212Y2 - Water level controller for boiler - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a water level control device for controlling the water level in a boiler can to an appropriate level.

[Conventional technology]

Generally, as a method for detecting the water level in the boiler can, there is a float type or an electrode rod type. In the former, the level switch is turned on and off through the float above and below the water level in the can.
It is used as a signal to start and stop the water supply pump.The latter utilizes the conductivity of water to determine whether the detection end of the electrode rod for starting or stopping water supply is submerged in water. A signal is taken out and the water supply pump is started and stopped by this signal.

[Problems to be solved by the device]

Normally, the water level in the can of the boiler is controlled to be maintained at a constant level by the above water level detection method, but the set water level for the control is fixed to one. But,
The amount of bubbles generated in the can water varies depending on the operating condition of the boiler and the condition inside the can (for example, combustion load, pressure inside the can, etc.), so when the combustion load is large and when it is small, and when the can pressure is high and when it is low. However, there is a considerable difference in the actual water level in the can. In other words, when the combustion load is large or the can internal pressure is low, the actual can water level tends to rise, and conversely, when the combustion load is small or the can internal pressure is high, the actual can water level is high. The level shows a downward trend.

As a result, if the water level in the can is too high, the dryness of the steam will decrease, and if the water level in the can is too low, the can body may be overheated. It is necessary to select the water level control range. Normally, the water level is set relatively high, with an emphasis on not overheating the can, so the stability of steam dryness maintenance is weak,
The dryness maintenance time has become short.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, this invention detects the dryness of the generated steam, raises or lowers the water level control range in accordance with the detected value, and selects the optimum water level control range to obtain a good dryness state. It can be maintained for a long time.

That is, this device is provided with a water level detector for detecting the water level in the can in the boiler, and the signal from this water level detector turns on the water supply pump to keep the water level in the can within a predetermined control range. In the water level control device for controlling OFF, the steam outflow pipe connected to the boiler is provided with a steam dryness detector for detecting the dryness of the steam flowing in the steam outflow pipe, and a signal from the steam dryness detector is provided. According to the above, a comparison arithmetic unit for determining the optimum water level control range and a controller for ON / OFF controlling the water supply pump to maintain the control water level within the optimum water level control range are provided.

[Action]

According to the water level control device according to the present invention, the optimum water level control range is determined according to the value of the dryness of steam, and the actual water level in the can can be changed by changing the water level control range even when the state inside the boiler can changes. The level is kept practically constant.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

The boiler (1) has an annular top header (1
1) and the lower header (12) are connected by a number of vertical water pipes (13). A space surrounding such a vertical water pipe array is used as a combustion chamber (14), and a burner (9) is installed above it. A water level control tube (15) is connected to the boiler (1) through connecting pipes (16) and (16). A water level detector (2) is installed in the water level control tube (15).
In the illustrated embodiment, the water level detector (2) has three electrode rods (S
Rods, M rods, L rods), and the controller (7) controls the water supply pump (3) ON-OFF based on signals from these electrode rods.

The steam generated in the boiler (1) is used in the steam separator (1
8), which is sent to an external steam-using device via the steam outflow pipe (4). The steam outflow pipe (4) has a steam dryness detector (for detecting the dryness of the steam flowing inside). 5)
Is provided, and the optimum water level control range is determined by the comparison calculator (6) based on the signal from the steam dryness detector (5).

The steam separator (18) is connected to the lower header (12) by a downcomer pipe (19), and a blow solenoid valve (8) is connected in the middle of the downcomer pipe (19). Further, the boiler (1) is provided with a water pipe overheat state detector (5 '),
For example, the dryness of steam in the water pipe (13) is detected. The lower header (12) has a water supply line (10)
Is connected to this water supply line (10) with a check valve (17)
And the water supply pump (3) is inserted.

Next, the operation will be described. The water that has flowed into the boiler (1) by the action of the water supply pump (3) receives the heat from the burner (9) to become steam, and passes through the steam outflow pipe (4) toward the external steam-using device. Boiler at that time (1)
The water level in the can is set so that the steam dryness is good and the can body is not overheated. However, if the boiler (1) continues to operate, the steam separator ( The water with high electric conductivity separated in 18) returns to the inside of the lower header (12) through the downcomer pipe (19), and the impurities contained in the water supply remain in the can. It gradually becomes highly concentrated. If this happens, good dryness cannot be maintained in the water level control range up to that point.

Therefore, the signal from the vapor dryness detector (5) provided in the vapor outflow pipe (4) determines that the dryness of the generated vapor has fallen below a preset value by the comparison calculator (6). Then, the water level control range is lowered (see FIG. 2). For example, in the embodiment using the three electrodes shown in the figure, the water supply pump (3) is turned on ₂ seconds after the water level cuts off the M rod, and the water supply pump (3) is turned off ₁ second after the water level reaches the S rod. , The water level is L
When the rod is cut, the burner (9) is controlled to have an abnormally low water level so as to cut the combustion. Therefore, the water level control range can be adjusted by changing t ₁ and t ₂ .
(See Figure 3).

In this way, by controlling the operating time of the water supply pump (3),
In addition to adjusting the water level control range, a plurality of water level detectors may be provided and appropriately switched.
When adjusting the water level control range, the water level control range may be adjusted in multiple stages, or may be adjusted in proportion to the detected vapor dryness value. That is, if the steam dryness is high, the water level control range is raised, and if the steam dryness is low, the water level control range is lowered.

As described above, the control water level is lowered when the steam dryness is lowered, but if it is lowered too much, the water pipe may be overheated. In this case, a water pipe overheat state detector (5 ') is provided as a safety device to detect the steam dryness in the water pipe (13), and when the detected value exceeds the set value, the steam dryness detector (5 ) Signal is given priority to raise the control water level to prevent overheating of the water pipe. The water pipe overheat state detector (5 ') may be, for example, a temperature sensor that directly measures the temperature of the water pipe in addition to a device that detects the dryness of steam, and may be a device that detects data that determines the risk of overheating. .

In addition, it can be used in combination with a concentrating blow device, and if the detected vapor dryness value falls below the set value set as the lower limit value, open the blow solenoid valve (8) and set an appropriate amount. By discharging the canned water, the concentration of the canned water can be suppressed and the dryness maintenance time can be further extended.

[Effect of device]

Since the present invention is configured as described above, the optimum water level control range can be selected according to the value of the steam dryness, and the most suitable water level that has good steam dryness and does not cause overheating of the can body. You can always get levels. In particular, even when condensing the can water where the steam dryness decreases, the steam dryness can be maintained in a good state by lowering the water level control range, and the dryness maintenance time is significantly extended.

As described above, according to the present invention, since it is possible to stably supply the vapor having a high degree of dryness to the external steam-using device, it is possible to improve and stabilize the efficiency of the steam-using device.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention, FIG. 2 is a flow chart showing an example of control in the embodiment of the present invention, and FIG. 3 is a change of water level control range in the embodiment of the present invention. FIG. (1) …… Boiler, (2) …… Water level detector (3) …… Water supply pump, (4) …… Steam outflow pipe (5) …… Steam dryness detector, (6) …… Comparison calculator (7) …… Controller

Claims (1)

[Scope of utility model registration request] 1. A boiler (1) is provided with a water level detector (2) for detecting the water level in the can, and the signal from this water level detector (2) keeps the water level in the can within a predetermined control range. In order to do so, in the water level control device for controlling the ON / OFF of the water supply pump (3), the degree of dryness of the steam flowing in the steam outflow pipe (4) is set in the steam outflow pipe (4) connected to the boiler (1). A steam dryness detector (5) for detecting is provided, and a comparison calculator (6) for determining an optimum water level control range by a signal from the steam dryness detector (5) and the control water level are set to the optimum water level. The water supply pump (3) to keep it within the control range
A water level control device for a boiler, comprising a controller (7) for ON-OFF control of the water.