JPH06159609A - Waterlevel control device for boiler - Google Patents

Abstract

PURPOSE:To prevent a rapid fall of waterlevel in a drum at the start of steam- feeding by feeding water as soon as an electrode detects no water when it continues to detect water during combustion for more than a given time. CONSTITUTION:Combustion starts, and waterlevel is detected. When an electrode E1 detects no water, a start signal is generated to a water-feeding pump 6 to start water-feeding, which is stopped when E1 detects water. As the desired amount of steam cannot be obtained soon after the combustion starts, the steam is not fed to an objective part, and the electrode E1 continues to detect water because of little amount of evaporation. When the electrode E1 continues to detect for more than a given time, a waterlevel control device 1 starts water- feeding as soon as E1 detects no water, even if the waterlevel does not fall to an electrode E2. Thus, a rapid fall of waterlevel due to the load fluctuation at the start of steam-feeding, and a loss of steam pressure due to the combustion stop can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water level controller for a multi-tube type once-through boiler.

[0002]

2. Description of the Related Art Can water supply control of a multi-tube once-through boiler is
There is a method to detect the water level by providing several water level detection electrode rods in the water level detection cylinder connected to the upper head or the brackish water separator and the lower head, and whether or not the electrodes detect the presence of water. Has been taken. Usually, three electrode rods E1, E2,
E3 is provided, and the detection electrode rods from the highest water level to below are E1, E2, and E3, respectively. The water supply control is performed by operating the water supply pump to supply water when the electrode rod E2 detects the absence of water, and stopping the water supply pump when water is detected at the electrode rod E1. The electrode rod E3 is used for detecting the water level in the can. Further, when controlling with two electrode rods, the electrode rods E1 and E3 are provided, and in the case of one electrode, the electrode rod E1 is provided, and the water level is predicted by the burning time after the electrode rod E1 detects the absence of water, To start.

At the start of combustion, the water level of the can water is usually E1 and E.
2 is located between the two, but when the water level is at a position where the electrode rod E2 starts to detect the presence of water, the steam pressure in the boiler decreases when the steam consumption is large, and the water level in the pipe sharply decreases. There is a possibility that the rod E3 will drop to a water level that does not detect the presence of water.

[0004]

The problem to be solved by the present invention is to supply a control device for preventing a sharp drop in the can water level at the start of steam supply.

[0005]

In order to solve the above-mentioned problems, the present invention detects the absence of water in the electrode rod E1 when the electrode rod E1 continues to detect the presence of water for a predetermined time or longer while the boiler is burning. Water will be supplied immediately after.

[0006]

If the water is supplied at the start of burner combustion, the water level hardly changes until the steam supply is started, so the electrode rod E1 continues to detect the presence of water. Large load fluctuations occur when steam supply is started. Only at that time, it is possible to mitigate the sudden drop in water level by accelerating the start of water supply.

[0007]

EXAMPLE An example of the present invention will be described. The water level detector tube (4) is connected to the brackish water separator (5) and the lower head (3), and the brackish water separator is connected to the upper head (2) and the lower head. The steam generated in the can is sent from the upper head to the brackish water separator where it is separated from the water and sent as dry steam to the steam required location. For the detection of the water level, the presence or absence of water is detected by the electrode rod in the water level detection cylinder, and the information on the water level is sent to the water level control device (1). Water supply control is performed by operating the water supply pump when water is detected by the electrode E2,
When the presence of water on the electrode rod E1 is detected, the water supply pump is stopped. The electrode rod E3 is used for detecting the water level in the can.

FIG. 2 shows the actual change of the water level in the can in one embodiment. When the operation of the boiler is started, the time from the stop of combustion to the start of the next combustion reaches a specified value or more, or the measured value from the temperature sensor attached to the can body or the water pipe is set to a specified value. When the boiler is cold, the water level is detected when the combustion start is started, and when the absence of water in the electrode rod E1 is detected, a start signal is sent to the water supply pump to start the water supply. Water supply is E
When it detects that there is water in 1, it stops. Even if combustion is started, the required amount of steam cannot be obtained immediately, so no steam is sent to the steam supply destination. Since the evaporation amount is small, the electrode rod E1 continues to detect the presence of water. The water level control device is set to start water supply even if the water level does not drop to E2 when the detection time (T) of the electrode rod E1 continues for a predetermined time or longer. When the steam pressure rises and steam supply is started, the steam has a large pressure difference and is rapidly sent to the supply destination. When the steam pressure drops and more steam needs to be supplied, the evaporation amount increases and the water level in the can drops sharply. As soon as the high water level is no longer detected, the water supply pump (6) is activated and water supply is started to prevent a sudden drop of can water. It is only at this time that water is supplied when the water does not fall to E2, and normal water level control is performed at other times.

[0009]

By implementing the present invention, it is possible to prevent the loss of steam pressure due to the stop of combustion without causing a sudden drop in the water level due to load fluctuations that occur at the start of steam supply, and it is extremely effective in practice. .

[Brief description of drawings]

FIG. 1 is a schematic diagram of an embodiment of the present invention.

FIG. 2 is a graph of water level according to an embodiment of the present invention.

[Fig. 3] Graph of conventional water level change

[Explanation of symbols]

 1 Water level control device 2 Upper pipe draw 3 Lower pipe draw 4 Water level detector 5 Brackish water separator 6 Water supply pump

Claims (1)

[Claims] 1. A water level detecting device, which is connected to an upper head or a brackish water separator by a steam connecting pipe and is connected to a lower head by a water connecting pipe, is provided outside the boiler main body to detect the water level in the water level detecting device. In a multi-tube once-through boiler with an electrode rod, where the water supply start level to the boiler of the water supply pump is E2 and the water supply stop level is E1, when the electrode rod E1 detects that the water level has not reached the water supply stop level E1. The feature is that water is supplied to the water level E1 at the same time when the burner starts burning, and thereafter, when the electrode E1 continues to detect the presence of water for a predetermined time or more during combustion, water is supplied immediately when the electrode E1 detects the absence of water. Boiler water level control device.