JPS63183304A - Steam-temperature control method of waste gas boiler - 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] Industrial applications The present invention relates to a steam temperature control method for an exhaust gas boiler.

Conventional technology Figure 3 shows a conventional example, in which the exhaust gas boiler is of a gas horizontal flow natural circulation type, 1 is a water supply pump, 2 is an energy saver, 3
4 is a water supply control valve, 4 is a steam drum, 51 evaporators, 6 is a superheater, and 7 is a mixer.

Then, the superheated steam is sent to the mixer through a line (hereinafter referred to as superheated steam line) 8 leading from the steam drum 4 to the mixer 7 via the superheater 6, bypassing the superheater 6 from the steam drum 4 and passing through the mixer. Saturated steam sent to this mixer through a line 9 (hereinafter referred to as saturated steam line) leading to 7 is mixed in, and the steam temperature after this mixing is kept at a constant value by means of a steam temperature controller 10 and a steam temperature control valve 11. It is controlled as follows.

Problems to be Solved by the Invention This conventional example, however, has the following problems.

That is, in the system as shown in FIG. 3, it is necessary that the pressure loss in the superheated steam line 8 and the saturated steam line 9 be the same. However, in a case where the load on the exhaust gas boiler decreases, naturally the generated steam 1 also decreases, and the pressure loss in the superheated steam line 8 decreases. Therefore, in such a case, it will be difficult to maintain the differential pressure of the steam temperature control valve 11 installed in the saturated steam line 9, so it is necessary to plan each component of this line to minimize pressure loss. be.

Therefore, due to such a pressure loss problem, not only does the saturated steam line 9 require large piping, but also a special arrangement is required in selecting the diameter and number of control valves for the controllability of the steam temperature control valve 11. It was needed.

Particularly when the load is low, there is almost no pressure loss in the superheated steam line 8, so there is a problem that the steam temperature cannot be controlled.

In order to solve the above-mentioned problem, an orifice or a square is provided between the superheater 6 and the mixer 7 to increase the pressure loss of the superheated steam line 8, thereby reducing the shoulder of the saturated steam line 9. Although it is possible to increase the number of effect fields, in this case, the pressure of the evaporator 5 will also rise correspondingly, and the amount of evaporation will decrease, so this is not an appropriate method in terms of heat recovery from the exhaust gas boiler. .

Means for Solving the Problems In order to solve these conventional problems, the present invention provides the following:
A part of the preheated feed water is taken out from the upstream side of the feed water control valve in the exhaust gas boiler and flashed to form saturated steam, and this saturated steam is mixed with superheated steam to control the steam temperature. This is how it was done.

According to such means, a part of the feed water is flashed to form saturated steam and the line for mixing it with the superheated steam is always controlled to a constant high pressure regardless of the pressure of the line that produces the superheated steam, This makes it possible to control the steam temperature even at lower loads.

EXAMPLES Hereinafter, examples of the present invention will be described in detail with reference to FIGS. 1 and 2. In these figures, the same parts as shown in FIG. 3 are designated by the same reference numerals, and detailed explanation thereof will be omitted.

FIG. 1 shows an embodiment in which a line 12 is connected from the upstream side of the water supply control valve 3 that controls the amount of water supplied to the steam drum 4 (the amount of water supplied), which is preheated by the wandering gas in the energy saver 2. A branch is made to extract a portion of this preheated feed water.

This line 12, like the saturated steam line 9 in FIG.
There is a pressure regulating valve on the upstream side of 1] 3 and a flash tank 14
The feed water is flushed to the flash tank 14 under a constant pressure according to the pressure adjustment*3 to form saturated steam, and this saturated steam is sent to the mixer 7 through the steam temperature control valve 11, thereby It is mixed into the superheated steam from the superheated steam line 8 to control the steam temperature. Water separated from steam in the flash tank 1417 can be returned to the steam drum 4 through the drain line 6 via the drain discharge valve 15.

In the exhaust gas boiler system as described above, the feed water control valve 3 is installed between the steam drum 4 and the economizer 2, and the water feed pump 1 is placed on the population side of the economizer 2. Therefore, during normal operation, the water supply pressure at the outlet of the economizer is approximately 20K17cm higher than the pressure at the steam drum 4.
Since the pressure is maintained at a high level, flushing of this high-pressure water supply can be easily performed.

Figure 2 shows the second actual winding example, where the water supply ° - saturated steam line 1
In case 2 requires a large amount of steam for temperature control,
An additional economizer 17 is provided in the evaporator 5, and this economizer is installed in the middle of the line 12 to ensure sufficient functionality.

The present invention can be applied not only to exhaust gas boilers of the horizontal gas flow natural circulation type as shown in FIGS. 1 to 3, but also to vertical gas flow forced circulation type exhaust gas boilers.

Effects of the Invention As detailed below, according to the present invention, a part of the preheated high-pressure feed water is flashed under a constant pressure, and the saturated steam thus formed is mixed into the superheated steam to increase the steam temperature. As a result, the pressure of this water supply-saturated steam line can always be maintained at a high level regardless of the pressure of the line that produces superheated steam, making it easy to control the steam temperature even at low loads. can be done.

In addition, in such a water supply-saturated steam line, the line pressure can be determined by taking appropriate pressure loss into consideration.
This facilitates the design of equipment such as steam temperature control valves provided in this line.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an example of the steam temperature control method for an exhaust gas boiler according to the present invention, FIG. 2 is a diagram showing a modification thereof, and FIG. 3 is a diagram showing a conventional example. 1. Water supply pump, 2. Energy saver, 3. Water supply control valve,
4. Steam drum, 5. Evaporator, 6. Superheater, 7.
-Mixer, 8...Superheated steam line, ]O...Steam temperature controller, 11...Steam temperature control valve, 12...Water supply-
Saturated steam line, 13. power control box, 14.. flash tank, I5.. drain discharge valve, 16.. drain line, 17.. energy saver. (1 other person) Figure 3

Claims (1)

[Claims] A feature is that a portion of the preheated feed water is taken out from the upstream side of the feed water control valve in the exhaust gas boiler and flashed to form saturated steam, and this saturated steam is mixed with superheated steam to control the steam temperature. A steam temperature control method for an exhaust gas boiler.