JPS61161304A - Air preheater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an air preheating device for preheating combustion air supplied to a boiler using steam.

BACKGROUND OF THE INVENTION In order to increase the combustion efficiency in conventional boilers, combustion air is prewarmed and the warmed air is supplied to the boiler. Air preheaters are used for this purpose, in which part of the steam generated in the boiler is used to heat the air. That is, the air preheater is a heat exchanger between steam and air, and is usually referred to as a steam air preheater (hereinafter abbreviated as SAH).

Figure 2 is shown to explain the function of a steam air preheater (SAH). 1 is the SAH main body, 1a is its superheating part, 1b is its saturation part (air-water mixing), and 2 is the SAH main body. 1
3 is a flow of combustion air that is sent to a boiler (not shown) through the SAH main body 1; 4 is a condensate pipe that is generated when the steam is cooled by heat exchange with the air; 1 to a condenser (not shown).

In this more advanced SAH, superheated steam is used as the heating source.
" is supplied to the SAH main body 1 from above in Fig. 2 and exhausted from below, while combustion air is supplied to the SAH main body 1 from the left in Fig. 2 and exhausted to the right, and steam and air Air is heated by the steam when it passes through the SAH main body 1.Then, this heated air is supplied to the boiler as combustion air.

Problems to be Solved by the Invention By the way, the air temperature at the outlet of the SAH main body 1 is operated at a relatively low temperature as part of the recent countermeasures against fine engineering. Therefore, even if the internal pressure of the SAW main body 1 is low and the temperature of the heating steam is constant, -
Since the saturation temperature decreases, the degree of superheating of the steam at the inlet of the SAH body 1 increases. Therefore, the temperature difference between the steam at the inlet and outlet of the SAH main body 1 becomes large, and the temperature of the heated air is also higher at the steam inlet and lower at the outlet. According to the unbalance of the steam temperature within the boiler, the air temperature also becomes unbalanced, resulting in a reduction in combustion efficiency in the boiler.

Note that FIG. 3 is a characteristic diagram showing the air temperature in correspondence with the position of the SAH main body 1, and shows that there is a large difference in air temperature between the steam inlet side and the steam outlet side.

Means for Solving the Problems The problem with the prior art is that the degree of superheating of the steam at the inlet of the SAH main body 10 is large, causing an imbalance in the steam temperature within the SAH main body 1. Therefore, in the present invention, the combustion air is heated by the steam line that leads heating steam to the steam air preheater to which the combustion air is guided, and the fluid that has become a gas-liquid multiphase flow is heated by the steam air preheater. In an air preheating device equipped with a discharge line, a desuperheater is disposed in the middle of the vapor line, and a drain line is provided in the discharge line to guide and spray liquid to the desuperheater.

Operation In the present invention, a portion of the liquid discharged from the SAH main body, that is, condensate condensate, is used as spray water to spray superheated steam in the steam line, thereby lowering the steam temperature. Therefore, the degree of superheating of the steam decreases, and the imbalance in steam temperature within the SAH main body 1 is reduced, thereby reducing the imbalance in the temperature of the heated air.

EXAMPLE Hereinafter, an example of the present invention will be described in detail with reference to FIG. In FIG. 1, the same parts as in FIG. 2 are designated by the same reference numerals.

In FIG. 1, reference numeral 1 denotes a steam air preheater (SAH) body, and a desuperheater 5 is provided in the middle of a steam pipe 2 that leads heating steam to the SAH body 1. In addition, SAH main body 1
In the middle of the discharge pipe 4 that discharges condensate from the
An AH drain tank 6, a SAH drain/bongua, and a level control valve 8 are provided in series. This level control valve 8
The opening and closing of the SAH drain tank 6 is controlled by a level regulator 9 provided in the SAH drain tank 6.

The discharge pipe 4 is branched between the SAH drain pump 7 and the level control valve 8, and this branch pipe 1° is connected to the desuperheater 5 via the spray water control valve 11 and the reversal valve 12. There is. A temperature regulator 13 is provided in the steam pipe 2 on the outlet side of the attemperator 5, and the spray water control valve 11 is controlled to open and close by the temperature regulator 13.

Next, the effect will be explained.

The heating steam is introduced into the SAH main body l via the attemperator 5, which will be described later, and heats the combustion air. The steam that is cooled and condensed through heat exchange with the combustion air becomes a drain and is sent to the SA.
The drain is collected in the H drain tank 6, and is sent out by the SAH drain pump 7 to the condenser (not shown) and the recovered light of the LP heater.

In order to maintain the drain in the SAH drain tank 6 within a predetermined level range, the level regulator 9 detects the drain and opens and closes the level control valve 8 accordingly.

A portion of the drain sent out from the SAH drain pump 7 is extracted to the branch pipe 10. This extracted drain is supplied to the attemperator 5 as spray water. That is,
The drain is sprayed into heating steam in the desuperheater 5. On the outlet side of the desuperheater 5, the temperature of the heating steam is detected by the temperature controller 13, and if this temperature is higher than the set temperature, the spray water control valve 11 is opened to continue spraying the condensate and the heating steam is The temperature of the steam is lowered, and when this temperature reaches the set temperature, the spray water control valve 11 is closed to stop the drain spray. The opening degree of the spray water control valve '11 is controlled according to the temperature of the heating steam.

In the above embodiment, the case where the internal pressure of the SAH main body 1 is constant is explained, but when the internal pressure changes,
A pressure detector is provided to detect the internal pressure of the vessel, the saturation temperature is determined from the internal pressure ρ) detected by this detector, and the spray water control valve 11 is operated so that the steam temperature becomes the saturation temperature + 2. Preferably, K is controlled.

Effects of the Invention As detailed above, according to the present invention, the degree of superheating of the heating steam is controlled to an appropriate temperature to balance the steam temperature within the SAH main body, and thus the BAH is preheated. This prevents the temperature of the combustion air from becoming unbalanced.

Therefore, it is possible to prevent the combustion efficiency of the boiler from decreasing due to an imbalance in the combustion air temperature.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an embodiment of the air preheating device according to the present invention, Fig. 2 is an explanatory diagram shown to explain the function of a steam type air preheater, and Fig. 3 is a conventional air preheating device. FIG. 3 is a characteristic diagram showing the state of air temperature corresponding to the position of the steam type air preheater in FIG. 1. Steam air preheater (SAH) body, 2. Steam pipe, 4... Discharge pipe, 5... Attemperator, 10... Branch pipe, 11... Spray water control valve, 13... Temperature regulator. (7 others) Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] A steam line that guides heating steam to a steam air preheater through which combustion air is introduced; and a discharge line that discharges a fluid that has been heated by the steam air preheater and has become a gas-liquid multiphase flow. An air preheating device comprising: a desuperheater disposed in the middle of the steam line, and a drain line for guiding and spraying liquid from the middle of the discharge line to the desuperheater. .