JPH09303710A - Auxiliary steam equipment of natural circulation boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable easy lowering of the temperature of superheater outlet steam by cooling to the demanded upper limit temperature of auxiliary steam by a simple construction. SOLUTION: This equipment is so constructed that superheater outlet steam 17 of a superheater 10 provided in a natural circulation boiler 1 is supplied as auxiliary steam 17a to a preheating device H of the natural circulation boiler 1 through a superheated auxiliary steam pipe 18 equipped with a pressure reducing orifice 19 (or a pressure reducing valve). A saturated steam mixing pipe 35 so designed as to take out saturated steam 3a of a drum 3 of the natural. circulation boiler 1 and to make it join the superheated auxiliary stem pipe 18 is provided and a temperature detector 36 is disposed on the downstream side of the pressure reducing orifice 19 in the superheated auxiliary steam pipe 18. Moreover, a flow control valve 37 provided for the saturated steam mixing pipe 35 regulates the flow rate of the saturated steam 3a on the basis of a detected temperature of the temperature detector 36.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an auxiliary steam device for a natural circulation boiler.

[0002]

2. Description of the Related Art FIG. 2 is a flow chart showing an example of the main configuration of a conventional natural circulation boiler, in which 1 is a natural circulation boiler consisting of a furnace 2 and a drum 3. Water 5 from a water supply pump 4 is supplied to the furnace wall of No. 1 through a economizer 6, and the water 5 is heated by combustion of fuel and air by a burner (not shown) and supplied to the drum 3. The steam 3a (saturated steam) is separated.

Saturated steam 3a separated by the drum 3
Is a superheater 10 such as a horizontal superheater 7 provided in the post-furnace transmission section, a radial superheater 8 provided in the furnace 2, a suspension type superheater 9, and the like.
After being superheated by the turbine, it is supplied to the high-pressure turbine 12 via the turbine inlet valve 11 to drive the high-pressure turbine 12, and then is guided via the turbine outlet pipe 13 to the horizontal reheater 14 in the post-fired part of the furnace. After being overheated again, it is supplied to the turbine 15 of medium pressure or low pressure to drive the turbine 15.

A superheat auxiliary steam pipe 18 for taking out a part of the superheater outlet steam 17 from the extraction point 16 is connected to the outlet of the radial superheater 8 in the superheater 10, and the superheat auxiliary steam pipe is also connected. 18 to a vacuum orifice 19 (or pressure reducing valve) the superheater outlet steam 17 having a provided example 196kg / cm ² of about pressure of 28 kg / cm ²
Reduce the pressure to a level of about 1 and use this reduced pressure steam as auxiliary steam 1
7a is supplied to a preheating device H for preheating air, water, fuel and the like.

On the other hand, the superheater outlet steam 17 from the superheater 10 has a high temperature of, for example, about 420 ° C. Further, when the natural circulation boiler 1 is started, the fuel supplied to the natural circulation boiler 1 is The temperature of the superheater outlet steam 17 may change transiently due to changes in the balance between water and air, and the temperature may rise to around 450 ° C.

However, the preheater H receiving the supply of the auxiliary steam 17a has a temperature of 350 ° C. of the auxiliary steam 17a as the required upper limit temperature due to the restriction based on the constituent material thereof. The temperature of 35
It is necessary to lower the temperature to about 0 ° C or lower.

For this reason, conventionally, as shown in FIG. 2, a spray water supply pipe 21 is provided at the outlet of the water supply pump 4 in a branched manner, and the end portion of the spray water supply pipe 21 is decompressed by the superheat auxiliary steam pipe 18. By connecting the downstream side of the orifice 19 through the spray mixer 20, the water supply pump 4
A part of the water 5 is mixed with the superheater outlet steam 17 to lower the temperature of the superheater outlet steam 17.

However, it is supplied from the water supply pump 4.
Water 5 pressure is usually 205kg / cm ^TwoAnd getting higher
The pressure of the auxiliary steam 17a (2
8kg / cm^Two42kg / cm according to the pressure)^TwoAbout
It is necessary to lower the temperature gradually, and the superheater outlet steam 17
Lower the temperature from about 420 ℃ to about 350 ℃
Since the amount of water 5 required for the
The two-stage pressure reducing valve 23 is installed in the spray water supply pipe 21.
Like that.

Further, the temperature of the auxiliary steam 17a is set to 350
In order to keep the temperature below ℃, a temperature detector 24 is installed downstream of the spray mixer 20 of the superheat auxiliary steam pipe 18, and further, the temperature detector 24 detects downstream of the pressure reducing valve 23 in the spray water supply pipe 21. A flow rate adjusting valve 25 is arranged to adjust the flow rate of water based on the temperature.

In the figure, reference numeral 26 is a separately provided auxiliary boiler, and the temperature of the superheater outlet steam 17 from the superheater 10 is low at the initial stage of startup of the natural circulation boiler 1, so that the preheater H is used. Therefore, the auxiliary boiler 26 is driven to supply the auxiliary steam 17b from the auxiliary boiler 26 to the preheating device H to preheat air, water and fuel. There is.

Further, when the natural circulation boiler 1 is in a normal operation state, steam which matches the temperature condition of the auxiliary steam 17a comes to be discharged from the high pressure turbine 12 to the turbine outlet pipe 13, An auxiliary steam extraction pipe 27 adapted to be supplied to the preheating device H as the auxiliary steam 17c is provided. In addition, this auxiliary steam extraction pipe 27
Are connected to various take-out positions where the steam that matches the required steam temperature of the preheating device H can be taken out.

Reference numeral 28 in the figure indicates that the saturated steam 3a from the drum 3 is taken out and the horizontal reheater 1 is installed when the natural circulation type boiler 1 is newly installed.
4 is a reheater safety valve test steam pipe for sending to 4 to test a safety valve (not shown) of the horizontal reheater 14, and after the safety valve test is completed, the shutoff valve 29 is closed and the flange portion 3
Therefore, the reheater safety valve test steam pipe 28 is not normally used.
In the figure, reference numerals 31, 32 and 33 denote open / close valves, and 34 denotes a discharge pipe.

When the conventional natural circulation boiler 1 is started, the water supply pump 4 is operated to supply water 5 from the economizer 6 to the furnace 2, and the fuel and air are burned by a burner (not shown). . At this time, the turbine inlet valve 11 is closed,
Further, the open / close valves 31 and 32 are closed and the open / close valve 33 is opened.

At the initial stage of starting the natural circulation boiler 1, the superheater outlet steam 17 cannot be used because it has a low temperature and a small amount. Therefore, the turbine inlet valve 11 and the opening / closing valve 32 are closed and opened / closed. The valve 33 is opened, and the superheater outlet steam 17 having a low temperature is discharged from the discharge pipe 34.

At this time, in order to preheat water, air, and fuel to shorten the start-up time (start-up time) of the natural circulation boiler 1, the auxiliary boiler 26 is driven and the auxiliary steam from the auxiliary boiler 26 is driven. 17b is supplied to the preheating device H.

When the amount of steam introduced into the drum 3 increases and the internal pressure of the drum 3 reaches, for example, about 10 kg / cm ² and the steam temperature at the outlet of the drum 3 reaches about 190 ° C., the on-off valve 33 is closed and the on-off valve is closed. 32 is opened so that the superheater outlet steam 17 from the superheat auxiliary steam pipe 18 is supplied to the preheating device H as the auxiliary steam 17a, and at the same time, the supply of the auxiliary steam 17b from the auxiliary boiler 26 is stopped, and the auxiliary boiler 26 Save energy consumption by.

When the temperature of the superheater outlet steam 17 gradually rises and exceeds 350 ° C., the flow rate control valve 25 is opened so that the temperature detected by the temperature detector 24 becomes the required upper limit temperature, for example, 350 ° C. The opening degree of the auxiliary steam 17a is adjusted so that the auxiliary steam 17a adjusted to the upper limit of 350 ° C. is supplied to the preheating device H.

When the temperature of the superheater outlet steam 17 reaches about 400 ° C., the turbine inlet valve 11 is opened and the superheater outlet steam 17 is supplied to the high pressure turbine to start warming of the high pressure turbine 12, Further, the steam in the turbine outlet pipe 13 is guided to the horizontal reheater 14 to be superheated again, and then is guided to the intermediate or low pressure turbine 15, so that the turbine 15 is also warmed.

After the warming of the high-pressure turbine 12 and the turbine 15, the high-pressure turbine 12 and the turbine 15 are gradually loaded (connected to the generator), and when the load reaches about 50% (half load), the on-off valve 32 is opened.
Is closed and the on-off valve 31 is opened, and thereafter, instead of the auxiliary steam 17a by the superheater outlet steam 17, the steam from the turbine outlet pipe 13 is supplied to the preheater H as the auxiliary steam 17c by the auxiliary steam extraction pipe 27. Will be supplied.

[0020]

However, in the conventional auxiliary steam apparatus of the natural circulation boiler shown in FIG. 2, a part of the water supply from the water supply pump 4 is sprayed into the water supply pipe 2.
After decompressing by the two-stage decompression valve 23 provided in 1, the superheater outlet steam 17 is mixed with the decompressed auxiliary steam 17a by the spray mixer 20 to be cooled and supplied to the preheating device H. Since the temperature of the water is adjusted to be equal to or lower than the set upper limit temperature, the water 5 having a high pressure (about 205 kg / cm ² ) from the water supply pump 4 is supplied to the low pressure (42 k).
g / cm ² or so) until it is necessary to reduce the pressure, yet for the amount of water 5 to be used for the cooling of the auxiliary steam 17a is small, the pressure reducing valve 23 of the two-stage is required a very large pressure decrease The pressure reducing valve 23 cannot be used for a short time due to erosion due to strict conditions, and the erosion of the pressure reducing valve 23 also causes the flow rate control valve 25 to be used under severe conditions. However, in recent years, the natural circulation boiler 1 has been frequently started and stopped in response to fluctuations in the required amount of electric power. Since the pressure reducing valve 23 and the flow rate adjusting valve 25 are used more severely, it becomes necessary to replace the pressure reducing valve 23 and the flow rate adjusting valve 25 in a short period of time.
3. It is difficult to manufacture and select the flow rate control valve 25.
Since it is expensive, there is a problem that the cost increases.

In the conventional apparatus, the auxiliary steam 1 after depressurization is used.
Since the temperature of the auxiliary steam 17a is lowered below the required upper limit temperature by mixing the water 5 with 7a,
As it is a mixture of steam and water, it is difficult to mix it uniformly,
Moreover, vibration is also likely to occur, which is why the spray mixer 2
0 is installed, but this spray mixer 2
There is a problem that 0 is expensive, and moreover, erosion is likely to occur and maintenance is difficult.

The present invention has been made in view of such circumstances, and is a natural circulation type in which the temperature of the superheater outlet steam can be easily cooled to the required upper limit temperature of the auxiliary steam with a simple structure. It is intended to provide an auxiliary steam device for a boiler.

[0023]

According to the auxiliary steam apparatus for a natural circulation boiler of the present invention, the superheater outlet steam of the superheater provided in the natural circulation boiler is passed through a superheat auxiliary steam pipe provided with a pressure reducing orifice. It is an auxiliary steam device for a natural circulation boiler that is supplied as an auxiliary steam to a preheating device for a natural circulation boiler, and takes out saturated steam from a drum of the natural circulation boiler and joins it with the superheat auxiliary steam pipe. The saturated steam mixing pipe, and a temperature detector is arranged downstream of the pressure reducing orifice in the superheat auxiliary steam pipe, and the saturated steam mixing pipe is saturated based on the temperature detected by the temperature detector. It is characterized in that a flow control valve for controlling the flow rate of steam is provided.

Further, the present invention is characterized in that the saturated steam mixing pipe for taking out the saturated steam of the drum is connected to the reheater safety valve test steam pipe connected to the drum.

In the present invention, since the auxiliary steam is obtained by cooling the steam at the outlet of the superheater with the saturated steam at the outlet of the drum, any means for adjusting the pressure of the saturated steam is not required, and it is simple. In addition, since the vapors are mixed with each other, the saturated steam mixing pipe is simply connected to the superheating auxiliary steam pipe so as to be orthogonal to each other, so that the mixture can be easily and uniformly mixed without causing vibration or the like. .

If a saturated steam mixing pipe is connected to the reheater safety valve test steam pipe connected to the drum so that a part of the saturated steam in the drum is taken out, it is used only when a natural circulation boiler is newly installed. Reheater safety valve test The steam pipe can be effectively used and the drum need not be modified.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example of an embodiment for carrying out the present invention applied to the conventional auxiliary steam apparatus for a natural circulation type boiler shown in FIG. 2, in which the same reference numerals are attached to the same parts. Is represented.

As shown in FIG. 1, the conventional spray water supply pipe 21 in FIG. 2 is abolished, and the drum 3 and the shutoff valve in the reheater safety valve test steam pipe 28 connected to the drum 3 of the natural circulation boiler 1 are removed. A saturated steam mixing pipe 35 is provided between the saturated steam mixing pipe 35 and the saturated steam mixing pipe 29 so that a part of the saturated steam 3a of the drum 3 is taken out and merged with the superheater outlet steam 17 of the superheat auxiliary steam pipe 18.

Further, a temperature detector 36 is arranged downstream of the pressure reducing orifice 19 (or pressure reducing valve) in the superheat auxiliary steam pipe 18, and a flow rate control valve 37 is arranged in the saturated steam mixing pipe 35. When the temperature detected by the temperature detector 36 becomes equal to or higher than the required upper limit temperature (for example, 350 ° C.), the flow rate control valve 37 is opened to adjust the flow rate of the saturated steam 3a flowing through the saturated steam mixing pipe 35, thereby the superheater outlet steam 1
7 is cooled by the saturated steam 3a so that the temperature of the auxiliary steam 17a does not exceed the required upper limit temperature.

At the initial start-up of the natural circulation boiler 1, the auxiliary boiler 26 is driven in the same manner as in the conventional case, and the auxiliary steam 17b from the auxiliary boiler 26 is supplied to the preheating device H.

When the amount of steam introduced into the drum 3 increases and the internal pressure of the drum 3 reaches, for example, about 10 kg / cm ² and the steam temperature at the outlet of the drum 3 reaches about 190 ° C., the on-off valve 3
3 is closed and the on-off valve 32 is opened to supply the superheater outlet steam 17 from the superheat auxiliary steam pipe 18 to the preheating device H as the auxiliary steam 17a.
Stop the supply of the auxiliary steam 17b from the auxiliary boiler 2
Save energy consumption by 6.

When the temperature of the superheater outlet steam 17 gradually rises and exceeds 350 ° C., the pressure reducing orifice 19
The flow rate control valve 37 is opened and the opening thereof is adjusted so that the temperature detected by the temperature detector 36 provided downstream of the temperature control device reaches the required upper limit temperature of, for example, 350 ° C. The steam 17a comes to be supplied to the preheating device H.

At this time, since the superheater outlet steam 17 of about 420 ° C. is cooled by the saturated steam 3a of about 190 ° C., 10 to 20% of the saturated steam 3a of the superheater outlet steam 17 is supplied. Auxiliary steam at 350 ℃ 17
a, and does not require any means for adjusting the pressure of the saturated steam 3a.
Since the seven steams are mixed with each other, the saturated steam mixing pipe 35 is simply connected to the superheat auxiliary steam pipe 18 so as to be orthogonal to each other, so that the superheated auxiliary steam pipe 18 can be easily and uniformly mixed without causing vibration or the like.

Further, as shown in FIG. 1, a saturated steam mixing pipe 35 is connected to the reheater safety valve test steam pipe 28 connected to the drum 3 so that a part of the saturated steam 3a of the drum 3 is taken out. The reheater safety valve test steam pipe 28 is used only when the natural circulation boiler 1 is newly installed.
Can be effectively used, so that it is not necessary to modify the drum 3.

As described above, the auxiliary steam 17a whose temperature is adjusted by mixing the saturated steam 3a with the superheater outlet steam 17
Is supplied to the preheating device H in the same manner as the conventional one.
2 and the turbine 15 are continued until about half load, and thereafter, the auxiliary steam 17a by the superheater outlet steam 17
Instead, the steam from the turbine outlet pipe 13 is supplied to the preheating device H as the auxiliary steam 17c by the auxiliary steam extraction pipe 27.

[0037]

According to the auxiliary steam device for a natural circulation type boiler of the present invention, the auxiliary steam is obtained by cooling the steam at the outlet of the superheater with the saturated steam at the outlet of the drum. It does not require any means for adjustment and can have a simple structure. Furthermore, since it is a mixture of steams, it is only necessary to connect the saturated steam mixing pipe to the superheat auxiliary steam pipe at right angles, and vibration etc. It can be mixed easily and uniformly without causing

If a saturated steam mixing pipe is connected to the reheater safety valve test steam pipe connected to the drum so that a part of the saturated steam in the drum is taken out, it is used only when a natural circulation boiler is newly installed. Reheater safety valve test The steam pipe can be effectively used and the drum need not be modified.

[Brief description of drawings]

FIG. 1 is a flowchart showing an example of an embodiment for carrying out the present invention.

FIG. 2 is a flowchart showing an example of a main configuration of a conventional natural circulation boiler.

[Explanation of symbols]

 1 Natural circulation boiler 3 Drum 3a Saturated steam 10 Superheater 17 Superheater outlet steam 17a Auxiliary steam 18 Superheat auxiliary steam pipe 19 Pressure reducing orifice (or pressure reducing valve) 28 Reheater safety valve test steam pipe 35 Saturated steam mixing pipe 36 Temperature detection 37 Flow control valve H Preheating device

Claims (2)

[Claims] 1. A superheater outlet steam of a superheater provided in a natural circulation boiler is supplied as auxiliary steam to a preheater of the natural circulation boiler via a superheat auxiliary steam pipe provided with a pressure reducing orifice. An auxiliary steam device for a natural circulation type boiler, wherein a saturated steam mixing tube is arranged to take out saturated steam from a drum of the natural circulation type boiler and join the superheated auxiliary steam tube. A temperature detector is arranged on the downstream side of the decompression orifice in, and the saturated vapor mixing pipe is provided with a flow rate control valve for adjusting the flow rate of saturated vapor based on the temperature detected by the temperature detector. Auxiliary steam equipment for circulating boilers. 2. Auxiliary steam for a natural circulation boiler according to claim 1, wherein the saturated steam mixing pipe for extracting saturated steam from the drum is connected to a reheater safety valve test steam pipe connected to the drum. apparatus.