JPS6222902A - Steam generator - 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 a steam generator, and more particularly to a variable pressure boiler in which the pressure changes depending on the load.

4) Conventional boilers generally have a water-cooled wall structure in which at least the side wall of the furnace peripheral wall is composed of evaporation tubes, and at least the side wall of the peripheral wall of the rear flue connected to the furnace is evaporatively cooled. The furnace water-cooled wall and the rear flue steam-cooled wall are joined by welding using fins or the like.

Problems to be Solved by the Invention However, in such a boiler, as shown in FIGS. 5 and 6, there are differences in heat storage capacity and heating conditions between the water-cooled wall of the furnace and the steam-cooled wall of the rear flue. Therefore, when the boiler load changes, the rate of temperature change between the two is different, especially when the load decreases, the temperature of the water-cooled wall outlet fluid and the temperature of the steam-cooled wall outlet fluid (steam), or the average of each wall tube of the water-cooled wall and the steam-cooled wall. There will be a difference in metal temperature.

In particular, in a variable pressure boiler, when the load drops, the saturation temperature decreases with the load, so the fuel is squeezed in advance by the difference in heat capacity of the metal (underfiring), so the water-cooled wall fluid Temperature and water-cooled wall metal temperature depends on the refrigeration according to load changes.In contrast, steam-cooled walls are slow to follow changes in the state of the fluid in the pipe, Because of this, the effect of underfiring (reduction in heat load) is delayed, and it is also affected by the heat retained in the metals of the inlet connecting pipes, steam-cooled wall pipes, etc., so the steam-cooled wall metal temperature does not change due to changes in the water-cooled wall metal temperature. However, there will be a delay. This results in a large difference in thermal expansion between the water-cooled wall and the steam-cooled wall.

Therefore, when the water-cooled wall of the furnace and the steam-cooled wall of the rear flue are joined by welding using fins, etc., stress generated due to the difference in thermal expansion occurs at this joint, especially at the fin ends.
This may cause damage to the fins.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to reduce the thermal stress generated at the joint between the water-cooled wall of the furnace and the steam-cooled wall of the rear flue, and to prevent damage to the joint.

Means for Solving the Problems In the present invention, at least the side wall of the furnace peripheral wall is constituted by a water-cooled wall, and at least the side part of the rear flue peripheral wall joined to the water-cooled wall is constituted by a steam-cooled wall. In a steam generator, a superheat reducer is placed in the middle of a steam cooling wall inlet communication pipe, a spray water supply pipe that supplies spray water is connected to this superheat reducer, and a water cooling wall outlet is placed in the middle of this spray water supply pipe. A spray control valve is provided whose opening degree is controlled by the temperature difference between the fluid at the outlet of the steam cooling wall and the fluid at the outlet of the steam cooling wall, or by the temperature difference between the metal near the outlet of the water cooling wall and the vicinity of the outlet of the steam cooling wall.

According to such a means, when the load changes, the difference between the steam cooling wall outlet fluid temperature and the water cooling wall outlet fluid temperature or the difference between the steam cooling wall metal temperature and the water cooling wall metal temperature is controlled by the spray control by the spray control valve. By controlling the temperature to be below a certain temperature, it is possible to prevent an excessive temperature difference from occurring, and therefore from generating thermal stress.

Example Embodiments of the present invention will be described in detail below with reference to the drawings.

In Figures 1 and 2, 1 is a water-cooled wall forming the furnace peripheral wall, 2 is a steam-cooled wall forming the rear flue surrounding wall, 3 is a water-cooled wall outlet connecting pipe, 4 is a water-cooled wall outlet connecting pipe, and 5 is a water-cooled wall forming the furnace peripheral wall. Steam/water separator or drum, 6 is a steam cooling wall inlet connecting pipe, 7 is a superheat reducer, 8
9 is a steam cooling wall inlet distribution pipe, 9 is a steam cooling equipment inlet header, and 10 is a steam cooling wall outlet connecting pipe.

A spray water supply pipe 11 for supplying spray water is connected to the superheat reducer 7 disposed in the middle of the steam-cooled wall inlet communication pipe 6, and a temperature difference controller 12 is connected in the middle of this pipe 11. Spray control valve 1 whose opening degree is controlled
3 is provided.

In FIG. 1, the temperature difference controller 12 controls the opening degree of the spray control valve 13 by detecting the temperature difference between the fluid flowing through the water-cooled wall outlet connecting pipe 4 and the fluid flowing through the steam-cooling wall outlet connecting pipe 10. The temperatures of these fluids are detected by temperature detectors 14a and 14b, respectively.

In addition, in FIG. 2, the temperature difference controller 12 detects the temperature difference between the metal near the outlet of the water-cooled wall 1 and the metal near the outlet of the steam-cooled wall 2, and adjusts the temperature difference Δ )Concave-#Shika-1-Fu-ni-mon-117 Tsukasa Dob, To^ya J are separated, and the temperature of these metals is measured by a temperature detector 14 having a plurality of temperature detecting elements 14C/, 14d/, respectively.
c, 14d.

Therefore, when the load changes, as shown in Figures 3 and 4, the difference between the fluid temperature at the outlet of the water-cooled wall and the fluid temperature at the outlet of the steam-cooled wall, or the difference between the temperature of the water-cooled wall metal and the steam-cooled wall metal temperature increases. The amount of spray water supplied to the attenuator 7 is controlled by the spray control valve 13 so that the temperature is below a certain level without causing large thermal stress at the joint between the water-cooled wall and the steam-cooled wall. .

Effects of the Invention As detailed above, according to the present invention, excessive thermal stress can be prevented from occurring at the joint between the furnace water-cooled wall and the rear flue steam-cooled wall by controlling the spray amount of feed water using the spray control valve. This makes it possible to reliably prevent damage to this joint, especially its weld fin.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an example of the steam generator according to the present invention, Fig. 2 is a diagram showing a modification thereof, and Fig. 3 is a diagram showing the fluid temperature at the outlet of the water cooling wall by the feed water spray control according to the present invention when the load changes. Figure 4 showing the change in temperature of the evaporating wall outlet fluid.
The figure similarly shows the change in the water-cooled wall metal temperature and the vapor-cooled wall metal temperature, and FIG.
FIG. 6 is a diagram similarly showing changes in water-cooled wall metal temperature and steam-cooled wall metal temperature. 1. Furnace water cooling wall, 2. Rear flue steam cooling wall, 4. Water cooling wall outlet connecting pipe, 6. Steam cooling wall inlet connecting pipe, 7. Superheat reducer, 10. Steam cooling wall outlet. Connecting pipe, 11...Spray water supply pipe, 12--Temperature difference controller, 13--Spray control valve, 14a-14d...Ten (and 1 other person) Fig. 3 □ Time Fig. 4-Gin MFJ

Claims (1)

[Claims] In a steam generator in which at least the side wall of the furnace peripheral wall is constituted by a water-cooled wall, and at least the side part of the rear flue peripheral wall joined to the water-cooled wall is constituted by a steam-cooled wall, the steam-cooled wall inlet connecting pipe is A superheat reducer is placed in the middle, and a spray water supply pipe that supplies spray water to the superheat reducer is connected, and the temperature between the fluid at the water-cooled wall outlet and the steam-cooled wall outlet is adjusted in the middle of the spray water supply pipe. A steam generator equipped with a spray control valve whose opening degree is controlled by the metal temperature difference between the vicinity of the outlet of the water-cooled wall and the vicinity of the outlet of the steam-cooled wall.