JP2002250504A - Method and device for controlling intermittent water supply to boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an economizer from being broken by water hammer by eliminating the occurrence of the water hammer in the economizer by automatically controlling the water supply quantity to a boiler, such as the multipipe once-through boiler, etc., which is on/off controlled for water supply. SOLUTION: The water supply quantity to the boiler is controlled by intermittently supplying water to the boiler by operating a water supply pump 10 and controlling the opening/closing of a motor-driven feed water valve 42 in accordance with a combustion load when the water level in the steam separator 24 of the boiler is high and a burner 40 is used for combustion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling intermittent water supply in a boiler such as a multi-tube once-through boiler. More particularly, the present invention relates to a method for preventing a water hammer caused by steaming in an economizer to protect the economizer. And a method and apparatus for controlling intermittent water supply in a boiler.

[0002]

2. Description of the Related Art Conventionally, water supply control in a boiler, for example, a multi-tube type once-through boiler, is performed by on-off control at low cost. As a result, steam is generated due to overheating (steaming), and a water hammer is generated in the economizer, which may generate an impact sound or break the economizer.

[0003]

The more exhaust heat is collected by the economizer in order to save energy and obtain high efficiency, the lower the exhaust gas temperature. However, the water supply temperature at the economizer outlet approaches the saturation temperature of the boiler operating pressure, and the above problem occurs.

[0004] The present invention has been made in view of the above points,
An object of the present invention is to control a water supply amount by operating a water supply pump when a burner burns at a high water level and opening and closing a water supply electric valve according to a combustion load, that is, by intermittently supplying water. , By creating a condition close to continuous water supply,
It is an object of the present invention to provide an intermittent water supply control method and apparatus in a boiler that prevents overheating of an economizer and prevents generation of water hammer due to steaming.

It is another object of the present invention to provide a method combining the following method in addition to the above-mentioned method at the time of transient response and an apparatus for implementing the method. (1) Post water supply immediately after stopping combustion (overheating prevention). (2) Water supply delay at startup (prevention of excessive water supply). (3) Water supply delay immediately after low combustion to high combustion (prevention of excessive water supply). (4) Excessive water supply immediately after high combustion to low combustion (overheating prevention).

[0006]

In order to achieve the above object, an intermittent water supply control method for a boiler according to the present invention is characterized in that a water level in a steam-water separator of a boiler is high and a water supply pump is used when a burner is burning. , And the water supply electric valve is controlled to open and close according to the combustion load to supply intermittent water, thereby controlling the water supply amount. In this method, assuming that the boiler output is 100, the feedwater pump is 120 to 18
In the case of 0%, for example, 150% water supply, high water level and high combustion, 70 to 100%, for example, 100% water supply, and in the case of high water level, low combustion, 35 to 50%, for example, 50% intermittent water supply control. It is preferable (see FIGS. 1 and 2).

[0007] It is preferable that a timer for controlling the opening time and the closing time of the electric water supply valve is controlled. further,
Immediately after stopping combustion, post-water supply is performed, delay control of water supply is performed at the start of combustion, delayed water supply control is performed immediately after shifting from low combustion to high combustion, and excess water control is performed during transition from high combustion to low combustion. It is preferable to configure so as to carry out. Instead of controlling the electric water supply valve, the water supply pump may be configured to intermittently supply water by controlling the on-time of the water supply pump according to the combustion load.

The intermittent water supply control device for a boiler according to the present invention is provided with a water supply motorized valve at an outlet of a water supply pump in the boiler, connecting at least two fuel supply valves in parallel to a burner of a boiler body, and connecting a pressure to a steam-water separator. A switch is provided, a level switch is provided in the water column pipe, at least two fuel supply valves, a pressure switch and a level switch are controlled by a control device to a feed water motorized valve, and the water feed motorized valve is intermittently controlled according to a combustion state. It is characterized by being connected (see FIG. 1).

In this apparatus, there may be a configuration in which a plurality of motorized water supply valves are arranged in parallel (see FIG. 2), or a configuration in which orifices are arranged in parallel with the motorized water supply valve (see FIG. 2). In these apparatuses, as a boiler, for example, a multi-tube once-through boiler is used.

[0010]

Embodiments of the present invention will be described below. The present invention is not limited to the following embodiments at all, and can be implemented with appropriate modifications. FIG. 1 shows an intermittent water supply control device in a boiler according to a first embodiment of the present invention. FIG. 1 shows a case where a multi-tube once-through boiler is used as an example of a boiler. The water supply is sent by a water supply pump 10 to an economizer (an economizer) 12, where it is heated by contact with exhaust gas from the boiler body 14. 16 is a heat transfer tube. The feed water heated by the economizer 12 is sent to the lower header 18 of the boiler main body 14 and is heated while moving up the multiparallel pipe 20 in the vertical direction. 22 is an upper header.

The steam mixture from the upper header 22 is sent to a steam separator 24 where it is separated into steam and water (hot water). The separated hot water is supplied to the lower header 1 of the boiler body 14.
8 26 is a water column pipe, 28 is a water level gauge, 30 is a safety valve, 32 is a main steam stop valve, 34 is an economizer bypass valve, 36 is a water supply check valve, 38 is a water supply stop valve, and 40 is a burner.

In the boiler configured as described above,
An electric water supply valve 42 is provided at the outlet of the water supply pump 10, two fuel supply valves 44 and 46 are connected in parallel to the burner 40 of the boiler main body, and a pressure switch 48 is provided in the steam separator 24.
The water column pipe 26 is provided with a level switch 50. And 2
The two fuel supply valves 44 and 46, the pressure switch 48 and the level switch 50 are connected to the electric water supply valve 42 via the control device 52.
In addition, the water supply electric valve 42 is interlocked so as to be intermittently controlled in accordance with the combustion state.

Also, as shown in FIG.
In some cases, another water supply electric valve 54 may be connected and arranged in parallel, or the water supply electric valve 42 or the water supply electric valves 42 and 54 may be connected and arranged in parallel.

In the water column pipe 26, three water level control electrodes, that is, a low water level cutoff electrode for turning on the water supply pump when the water level B is reached, a water supply pump on electrode for turning on the water supply pump when the water level L is reached, and a water level H Then, a water supply off electrode for turning off the water supply pump is provided. With such a configuration, the once-through boiler is turned on / off by detecting a change in the water supply height by the electrode. On the other hand, in burner combustion, three-position control of high combustion, low combustion, and stop is performed by a change in steam pressure. Each of these is not linked and is a separate operation. Therefore, when the water is full, the water supply becomes zero (zero), and in the conventional configuration, the economizer is overheated. In order to prevent this, even when the water level is high and there is no water supply, the water supply pump 10 is turned on at the time of combustion and the water supply electric valve 42 is controlled so as to intermittently supply water so that the economizer does not evaporate without overheating. To prevent excessive water supply, supply an appropriate amount of water with high combustion and low combustion. At the time of high combustion, the electric valve 42 is opened and closed to adjust the opening time of the electric valve 42 to control the amount of water supply.

In order to perform economizer protection water supply control,
As shown in FIG. 3 and Table 1, during combustion, water is forcibly supplied according to the combustion state. When the boiler output is 100, the feedwater pump is 150% water supply.
In the case of% water supply, high water level and low combustion, intermittent control is performed to 50% water supply. For example, for 100% water supply, a timer for 40 seconds opening and 20 seconds closing is intermittently controlled so that the electric valve 42 is 66% open,
50% water supply is controlled by a timer that opens 33%.

[0016]

[Table 1]

In an actual machine, it is preferable to set 100% in Table 1 to 80% and 50% to 40%. 4 to 7 show the control during the transient response. FIG. 4 shows a case in which control is performed to prevent overheating of the economizer by performing post-water supply for 5 seconds, for example, immediately after the combustion is stopped. FIG. 5 performs delay control of economizer protection water supply at the start of combustion to reduce the overheated water supply of the economizer. FIG. 6 shows a case in which the delay water supply control is performed immediately after the transition from the low combustion to the high combustion to prevent overheating of the economizer, and FIG. 7 shows a case in which the high combustion changes to the low combustion. Shows a case where the control is performed to prevent overheating of the economizer by performing excess water supply control at the time of shifting.

As described above, in the present invention, the water supply amount is controlled in accordance with the three-position combustion. In addition, combustion-on delay water supply is performed. When the combustion is on, the water in the boiler expands and the water level rises, so that the continuous water supply is delayed. Delayed water supply is performed at the time of transition from low combustion to high combustion.
This reduces the continuous water supply since there is an expansion of the water level. In addition, post water supply (post water supply) is performed. Immediately after the combustion is stopped, steaming is performed using existing hot gas.
Post water supply for 7 seconds, preferably about 5 seconds.

[0019]

As described above, the present invention has the following effects. (1) A boiler whose water supply is on / off controlled, by automatically controlling the water supply (water flow) according to the operating condition,
Eliminating steaming and water hammer in the economizer can prevent damage to the economizer and the generation of impact noise. Note that, in the above embodiment, the case where the water supply electric valve is controlled has been described. Alternatively, the water supply pump may be configured to intermittently supply water by performing on / off control of the on-time according to the combustion load. It is.

[Brief description of the drawings]

FIG. 1 is a schematic configuration explanatory diagram of an intermittent water supply control device in a boiler according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration explanatory view showing another example around the electric water supply valve in FIG. 1;

FIG. 3 is a flowchart illustrating an example of an operation according to the present invention.

FIG. 4 is a control explanatory diagram showing a case of post water supply according to the present invention.

FIG. 5 is a control explanatory diagram showing a case of delayed water supply in the present invention.

FIG. 6 is a control explanatory diagram showing a case of delayed water supply immediately after transition from low combustion to high combustion in the present invention.

FIG. 7 is a control explanatory diagram showing a case of excess water supply immediately after transition from high combustion to low combustion in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Water supply pump 12 Economizer 14 Boiler main body 16 Heat transfer tube 18 Lower header 20 Multi-parallel tube 22 Upper header 24 Steam separator 26 Water column tube 28 Water level gauge 30 Safety valve 32 Main steam stop valve 34 Economizer bypass valve 36 Water supply check valve 38 Water supply Stop valve 40 Burner 42, 54 Electric water supply valve 44, 46 Fuel supply valve 48 Pressure switch 50 Level switch 52 Controller 56 Orifice

Continued on the front page (72) Inventor Hirofumi Hamasaki 1000 Aochi-cho, Kusatsu-shi, Shiga F-term in the Shiga Plant of Kawaju Cooling and Heating Co., Ltd. F-term (reference) 3L021 AA04 BA00 CA01 EA04 FA03

Claims (9)

[Claims] The water supply in a steam-water separator of a boiler is at a high water level, and when a burner is burning, a water supply pump is operated to control opening and closing of a water supply electric valve according to a combustion load to supply intermittent water. An intermittent water supply control method in a boiler, characterized in that the amount is controlled. 2. When the boiler output is set to 100, the water supply pump supplies 120 to 180% of water, 70 to 100% of water for high water level and high combustion, and 35 for high water level and low combustion.
The intermittent water supply control method for a boiler according to claim 1, wherein the intermittent water supply is controlled to about 50% of water supply. 3. The intermittent water supply control method in a boiler according to claim 2, wherein timer control of the open time and the close time of the electric water supply valve is performed. 4. Post-water supply is performed immediately after combustion is stopped, delay control of water supply is performed at the start of combustion, delayed water supply control is performed immediately after transition from low combustion to high combustion, and post-water supply control is performed during transition from high combustion to low combustion. 4. The intermittent water supply control method in a boiler according to claim 1, wherein the water supply control is performed. 5. The intermittent water supply control method for a boiler according to claim 1, wherein instead of controlling the electric water supply electric valve, the water supply pump is intermittently supplied with on / off control of an on-time according to a combustion load. 6. A water supply motorized valve is provided at an outlet of a water supply pump in a boiler, at least two fuel supply valves are connected in parallel to a burner of a boiler body, a pressure switch is provided in a steam separator, and a level switch is provided in a water column pipe. And at least 2
An intermittent water supply control device for a boiler, wherein two fuel supply valves, a pressure switch, and a level switch are connected to an electric water supply valve via a control device so that the electric water supply valve is intermittently controlled according to a combustion state. 7. The intermittent water supply control device for a boiler according to claim 6, wherein a plurality of electric water supply electric valves are arranged in parallel. 8. The intermittent water supply control device for a boiler according to claim 6, wherein an orifice is arranged in parallel with the electric water supply valve. 9. The intermittent water supply control device in a boiler according to claim 6, wherein the boiler is a multi-tube once-through boiler.