JPH0322521B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a waste heat boiler that solves the problem of economizer corrosion and efficiently recovers waste heat.

(Prior art and its problems) Conventionally, in waste heat boilers, the exhaust gas containing a particularly large amount of sulfur has a problem of corrosion.
Heat was not recovered in the low temperature range and was dissipated as is.

That is, as shown in FIG. 3, in the conventional waste heat boiler, the water supplied by the boiler feed water pump 3 is guided to the economizer 4, where the temperature is raised, and the water is supplied to the boiler drum 1. This water supply inside the boiler drum 1 is as follows:
The evaporator 5 collects waste heat and evaporates it. This steam is further guided to the superheater 6 provided on the highest temperature side, and becomes superheated steam.

In this conventional waste heat boiler, when the waste heat temperature is low, the economizer 4 installed in the lowest temperature part
When the pipe wall temperature of the economizer 4 decreases to below the dew point of the sulfur contained in the waste gas,
is corroded, making it virtually impossible to operate the waste heat boiler.

Therefore, in order to recover heat in a low temperature range where the economizer is corroded, the actual situation is to simply dissipate the heat without installing the economizer 4, or to preheat the water supply using a separately installed water heater 15.

(Objective of the Invention) The present invention has been made in view of the above circumstances, and aims to provide a waste heat boiler that solves the problem of economizer corrosion and efficiently recovers waste heat in a low temperature range. It is something.

(Structure of the Invention) The present invention raises the temperature of feed water from a boiler feed water pump using an economizer, leads the heated feed water to an evaporator to be evaporated, and leads the evaporation to a superheater to obtain superheated steam. The waste heat boiler is characterized in that a part of the high temperature water of the evaporator flows into the economizer water supply inlet to control the temperature of the economizer inlet water supply.

(Example) An example of a waste heat boiler according to the present invention will be described with reference to FIG. In the figure, the same reference numerals as in FIG. 3 indicate the same parts, and the water supplied from the water supply pump 3 is heated by the economizer 4, supplied to the boiler drum 1, heated by the evaporator 5 and evaporated, and then What is done to the superheated steam in the superheater 6 is the same as that of a conventional waste heat boiler. In addition, in the waste heat boiler of the present invention, a piping 8 is connected to a water supply pipe 7 from the water drum 2 to an economizer 4, and a circulation pump 9 and a temperature control valve 10 are installed in the middle of this piping 8. Opening/closing control is performed based on the temperature detected by a temperature detector 11 provided at the inlet of the economizer 4. Reference numeral 12 denotes a water supply flow rate control valve, which controls one element of the signal from the drum water level gauge 16 or controls three elements based on signals calculated by a calculator 18 from the signals of the drum water level gauge 16, steam flow meter 14, and water supply flow meter 17. control.

(Function) In the waste heat boiler of the above embodiment configured as described above, the amount of water supplied from the water supply pump 3 to the economizer 4 is determined by the water supply whose opening degree is controlled by one-element or three-element control as described above. It is regulated by a flow rate control valve 12. On the other hand, the high-temperature water taken out from the water drum 2 for temperature adjustment returns to the economizer 4 again via piping 8 and water supply pipe 7, so it circulates within the boiler, and the amount of water supplied within the boiler does not change. The flow rate to the water supply flow rate control valve 12 is not affected.

Now, the tube wall temperature of the economizer 4 is adjusted as follows. That is, the tube wall temperature of the economizer 4 is theoretically determined by the temperature of the water supply flowing inside it. Therefore, by adjusting the inlet water temperature of the economizer 4, the tube wall temperature is indirectly adjusted.

The inlet water temperature of the economizer 4 is detected by the temperature detector 11, and the opening degree of the temperature control valve 10 is adjusted so that the pipe wall temperature of the economizer 4 is equal to or higher than the dew point temperature of the sulfur content in the waste gas. Adjust the water supply inlet temperature of economizer 4.

In this case, the water injected from the water drum 2 is used only to raise the temperature of the water supplied to the economizer 4, so no heat is radiated to the outside, and the water is supplied to the economizer 4.
This will efficiently recover waste heat at low temperatures while preventing corrosion.

FIG. 2 shows another embodiment in which the system is applied to a forced circulation boiler, in which water supplied by a boiler feed water pump 3 is heated in an economizer 4 and supplied to a steam drum 1. This feed water is guided to the evaporator 5 by the circulation pump 9, evaporated, enters the steam drum 1, and then superheated by the super heater 6.

The feed water inlet temperature of the economizer 4 is detected by the temperature detector 11, and the temperature control valve 1 is thereby detected.
Similarly, the tube wall temperature of the economizer 4 is adjusted by adjusting the opening degree of 0 and the divided flow rate from the circulation pump 9.

In this embodiment as well, since the high temperature water for temperature adjustment circulates within the boiler, the water supply flow rate control valve 1
Regarding the fact that it does not affect the flow rate control in step 2, and that the high temperature water taken out from the evaporator 5 is used only to raise the temperature of the feed water and does not radiate heat to the outside, it efficiently recovers waste heat in the low temperature range. is the same as the embodiment shown in FIG.

(Effects of the Invention) As detailed above, the waste heat boiler according to the present invention branches some high-temperature water from the evaporator and injects it into the water supply inlet of the economizer to adjust the temperature of the water supply at the economizer inlet. As a result, the temperature of the economizer tube wall can be made higher than the dew point temperature of the sulfur content in the waste gas, which has excellent effects such as preventing corrosion of the tube wall and making it possible to recover heat from the waste gas at low temperatures. .

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 are one embodiment of the present invention,
Figure 1 shows the case where it is applied to a natural circulation boiler.
The figure is a flow sheet when applied to a forced circulation boiler. FIG. 3 is a flow sheet of a conventional waste heat boiler, taking a natural circulation boiler as an example. 1...Steam drum, 2...Water drum, 3...Water pump, 4...Economizer, 5...Evaporator,
6... Super heater, 7... Water supply pipe, 8... Piping, 9... Circulation pump, 10... Temperature control valve, 1
1...Temperature detector, 12...Water supply flow rate control valve, 1
3... Outlet pipe, 14... Flow rate detector, 15... Water supply heater, 16... Drum water level gauge, 17... Water supply flow meter, 18... Arithmetic unit.

Claims (1)

[Claims] 1 In a waste heat boiler in which the feed water from the boiler feed water pump is heated by an economizer, this heated feed water is led to an evaporator to be evaporated, and this steam is led to a superheater to obtain superheated steam, the evaporator A waste heat boiler characterized in that a part of the high-temperature water is merged into an economizer water supply inlet to control the temperature of the economizer inlet water supply.