JPH0275806A - Boiler - Google Patents

Abstract

PURPOSE:To protect an economizer from being damaged by abnormal pressure increase by detecting the pressure of the economizer to slightly open a water level regulating valve when the pressure exceeds a specific value. CONSTITUTION:In the case where the pressure of an economizer 4 does not abnormally increase, an operation control device 9 performs normal operation such as a water level regulating valve 5 holds the water level of a steam drum 6 at a set point. When the water level of the steam drum 6 increases higher than the set point for some reason, the water level regulating valve 5 is wholly closed. Thereby the economizer 4 is in a condition to close because of having a check valve 3 at the inlet side and the temperature of water feed is increased by the holding heat quantity of a boiler or the heat quantity of the gas to heighten the pressure thereof by the thermal expansion of the feed water. The pressure increase is detected by a pressure detector to enforcedly slightly open the water level regulating valve 5 by the operation control device 9 so as to release the feed of the economizer 4 into the steam drum 6, so that the abnormal pressure increase of the economizer 4 can be prevented. Since the increment of the volume by the thermal expansion of the feed water is small as compared with the volume of the steam drum 6, the water level of the steam drum 6 is not abnormally increased.

Description

Detailed Description of the Invention (Objective of the Invention) (Industrial Field of Application) The present invention relates to a boiler that includes a economizer, an evaporator, and a steam drum, and a steam drum water level control valve at the outlet of the economizer. Fold,
In particular, the present invention relates to a boiler that prevents abnormal pressure rise in the economizer and prevents generation of excessive stress and damage to the economizer.

(Conventional technology) An example of a conventional boiler is shown in FIG.

In FIG. 2, water is supplied from the water supply pump 2, passes through the check valve 3, reaches the economizer 4, is heated, and then passes through the communication pipe 11 and the water level control valve 5, and reaches the steam drum 6. The water supplied in the drum 6 is appropriately circulated through the evaporator 7 to be heated and turned into steam, which is then sent to the user. In a boiler with such a configuration, when the water level in the steam drum 6 rises, the water level control valve 5 is closed, blocking the inflow of feed water into the drum.

(Problem to be solved by the invention) The prior art shown in FIG. 2 has the following drawbacks.

As mentioned above, when the water level of the steam drum 6 rises, the water level control valve 5
is fully opened and the flow of water supply is cut off.

Therefore, when the water supply in the energy saver 4 is heated roughly, the volume of the supply water expands due to the temperature rise. However, since the water level control valve 5 at the outlet of the energy saver 4 is closed and the energy saver 4 has a check valve at the outlet of the water supply pump 2, there is no room for volumetric expansion of the water supply. In such a case, the compressibility of the feed water is so low that even a slight temperature increase will cause an extremely large pressure increase. Generally, this is called abnormal pressure increase, and in this case, excessive stress is generated in the economizer 4 and its attached piping, and as this is repeated, various parts are damaged. In addition, designing each part to withstand abnormal pressure increases is uneconomical, such as making the pipes thicker. In particular, thicker heat transfer tubes such as those used in economizers can lead to a decline in heat transfer performance. , it would be extremely uneconomical overall.

The present invention was made in the background as described above, and
The purpose of this is to prevent abnormal pressure rise when the water level in the steam drum rises, the drum water level control valve closes, and the water economizer enters the cut-off state together with the water feed pump outlet check valve at the energy economizer inlet. The object of the present invention is to provide a boiler that prevents the generation of excessive stress and damage to the economizer, and prevents an increase in equipment costs and a decrease in heat transfer performance due to thickening of heat transfer tubes.

(Structure of the Invention) (Means for Solving the Problems) The present invention is intended to achieve the above-mentioned object, and includes a tubular economizer that receives supply water and heats the supply water, and has a water level inside. A steam drum that forms a steam drum, a communication pipe that connects the economizer and the evaporator via a water level control valve, and an evaporator that heats the water in the steam drum and supplies the steam generated by evaporation to the steam drum. A boiler equipped with this must have a pressure detection device that detects the pressure inside the economizer, and a calculation control device that slightly opens the water level control valve when the pressure exceeds a predetermined value. .

(Function) When heat is applied to the economizer when the water level control valve is fully open, the pressure inside the economizer increases due to thermal expansion of the water supply inside the economizer. At this time, the water level control valve opens slightly, preventing an excessive rise in pressure.

(Example) Hereinafter, one example of the present invention will be described with reference to FIG. However, parts common to the prior art shown in FIG. 2 are given the same reference numerals and their explanations will be omitted. The boiler abnormal pressure increase prevention device shown in FIG. 5 as appropriate.

During normal operation with the above configuration, if the pressure of the economizer 4 does not rise abnormally, the arithmetic and control unit 9 does nothing, so the water level control valve 5 is operated normally to maintain the water level of the steam drum 6 at the set value. perform the following actions. When the water level in the steam drum 6 rises above the set value due to some reason, such as load fluctuation or hot banking, the water level control valve 5 is fully opened to prevent the supply water from flowing into the steam drum 6. As a result, since the economizer 4 has the check valve 3 on the inlet side, it is in a closed state, and when the temperature of the feed water rises due to the amount of heat held by the boiler or the amount of heat of the gas, the pressure increases due to thermal expansion of the feed water. This pressure increase is detected by the pressure detector 8, and the calculation control I
The water level control valve 5 is forcibly opened slightly by the II device 9 to allow the water supplied in the economizer 4 to escape into the steam drum 6, thereby preventing abnormal pressure rise in the economizer 4.

The increase in volume due to thermal expansion of the feed water is usually negligibly small compared to the volume of the steam drum 6, so this release operation will not cause the water level in the steam drum 6 to rise abnormally.

On the other hand, if the water level control valve 5 is left in the forced state, water will be supplied through the check valve 3 when the water pump 2 is in operation, causing an abnormal rise in the water level in the steam drum.

Therefore, the pressure of the energy saver 4 becomes lower than the cut-off pressure of the water supply pump 2 or the minimum 70 - discharge pressure during operation, and the check valve 3
When the pressure rise in the economizer 4 subsides, the water level control valve 5 is closed and the water level control valve 5 is closed to prevent the water from flowing into the economizer 4 and the steam drum 6. The forced operation of the water level control valve 5 may be performed for a short time using a timer or the like.

Also, while the water level control valve 5 is forcibly closed, the check valve 3 may also be forcibly closed.

Therefore, in this embodiment, it is possible to prevent abnormal pressure increase in the energy saver 4, and to prevent generation of excessive stress and damage due to this.

〔Effect of the invention〕

As described above, the boiler abnormal pressure rise prevention device according to the present invention prevents abnormal pressure rise in the energy saver, and prevents generation of excessive stress and damage due to this. There is no need for a detailed design, and it is possible to reduce equipment costs and improve the heat transfer efficiency of the energy saver.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of an embodiment of a boiler according to the present invention;
The figure is a system diagram of a conventional boiler. 1...Boiler body, 2...Water pump, 3.
... Check valve, 4... Energy saver, 5... Water level control valve, 6... Steam drum, 7... Evaporator,
8... Pressure detector, 9... Arithmetic control device, 11... Communication pipe, a... Gas,
b...Steam, C...Water supply, d...Signal. Agent Patent Attorney Noriyuki Chika Ken Yudo Daishimaru Ken Figure 1

Claims (1)

[Claims] A tubular economizer that receives a supply of water and heats the water, a steam drum that forms a water level inside, and a water level control valve that is connected between the economizer and the evaporator. A pressure detection device that detects the pressure in the economizer, in a boiler equipped with a communication pipe that communicates with the water, and an evaporator that heats water in the steam drum and supplies steam generated by evaporation to the steam drum, 1. A boiler comprising: an arithmetic and control device that slightly opens the water level control valve when the pressure exceeds a predetermined value.