JPH102502A - Starting method for steam superheater by sodium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent inflow of a moisture content (condensed water and saturated steam) to a superheater during the starting of the use of a steam superheater, i.e., during ventilation of steam to the superheater. SOLUTION: Superheated steam 14d is gradually fed from a seperheated steam valve 11 as steam is discharged from a steam discharge valve 13. A pressure and temperature in a spot situated upper stream from a steam superheater 1 are detected and a pressure and temperature in the superheater are gradually increased as a detecting pressure and a detecting temperature are held in a superheated steam region. Concretely, the superheated steam 14d having a constant temperature is gradually fed, a feed amount is reduced in short of a saturated pressure at temperature. Superheated steam is fed again according to the increase of a steam temperature, and the pressure and the temperature are gradually increased as a pressure is held at a value lower than the saturated pressure of a steam temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a steam superheater for heating steam using sodium as a heat medium, and more particularly to a method for starting the steam superheater.

[0002]

2. Description of the Related Art A steam superheater 1 (hereinafter simply referred to as a superheater) schematically shown in FIG. 3 is used to heat steam using high temperature liquid sodium as a heat medium to produce superheated steam having a high degree of superheat. Have been. The superheater 1 is a kind of indirect heat exchanger composed of a sodium container 1a and a heat transfer tube 1b passing through the inside thereof. Liquid sodium 2 is supplied into the sodium container 1a, and an evaporator (evaporator 3)
The steam 4a evaporated in the above flows inside the heat transfer tube 1b and is indirectly heated by the high-temperature (for example, about 450 ° C.) sodium 2 to become a superheated steam 4b having a high degree of superheat, and the superheated steam 4b is supplied to the steam turbine 5 and the like. To generate condensed water 4c with a condenser 5a.
At a, it is supplied to the evaporator 3. A steam line extending from the evaporator 3 to the steam turbine 5 and the like via the superheater 1 is called a main steam line. The main steam line includes a valve 6a for adjusting and shutting off the steam flow upstream and downstream of the superheater 1. , 6b.

In the above-described steam superheater 1 using sodium as a heat medium, stainless steel having excellent heat resistance and corrosion resistance is used for the heat transfer tube 1b. However, if water droplets adhere to stainless steel at a high temperature, iron and the like may be dissolved at that portion, causing stress corrosion cracking. Therefore,
In such a superheater, it is necessary to strictly control the moisture content of the ventilation steam in order to prevent stress corrosion cracking.

That is, when the superheater 1 is started to be used (during start-up), the valves 6a and 6b are closed, and even if the sodium 2 is supplied to the sodium container 1a, the valves 6a and 6b are closed. When the valves 6a and 6b are opened as they are, the steam may condense on the inner surface of the pipe and the water droplets may flow into the heat transfer pipe 1b until the temperature of the pipe sufficiently rises.

For this reason, in the conventional superheater, as shown in FIG. 3, an auxiliary steam line for guiding the superheated steam 4d from the auxiliary boiler 7a and a drain line for removing the drain 4e are provided to superheat the auxiliary steam (superheated steam 4d). After sufficiently heating the space between the valves 6a and 6b supplied from the vessel inlet side, the valves 6a and 6b
(Hereinafter referred to as warming).

[0006]

However, even during the above-mentioned warming with superheated steam, water vapor condenses in the low-temperature pipe, and condensed water may flow into the superheater 1 to cause stress corrosion cracking. There is. Therefore, the inlet side piping of the superheater 1 is provided with a function of discharging the condensed drain by providing a slope downward from the superheater to the upstream side, but there is a problem that the inflow of moisture into the superheater cannot be completely prevented. there were.

The present invention has been made to solve such a problem. That is, an object of the present invention is to provide a steam superheater that can prevent the inflow of moisture (condensed water and saturated steam) into the superheater at the start of use of the steam superheater, that is, at the time of steam aeration to the superheater. It is to provide a starting method.

[0008]

According to the present invention, there is provided a method for starting a steam superheater for indirectly heating steam using high temperature liquid sodium as a heat medium, comprising a superheated steam valve for superheated steam from the valve. A superheated steam line to feed the vessel,
A steam discharge line that has a steam discharge valve and discharges steam passing through the superheater from this valve, and a pressure sensor and a temperature sensor that detect pressure and temperature on the upstream side of the superheater, while discharging steam from the steam discharge valve Slowly supply superheated steam from the superheated steam valve, detect the pressure and temperature in the superheater, and gradually maintain the detected pressure and detected temperature in the superheated steam area, while gradually increasing the pressure and temperature in the superheater. A method for starting a steam superheater with sodium is provided.

According to the method of the present invention, the superheated steam is gradually supplied from the superheated steam valve while discharging the steam from the steam discharge valve, and the pressure and the temperature on the upstream side of the superheater are detected. Is maintained in the superheated steam region while gradually increasing the pressure and temperature in the superheater, so that the pressure and temperature in the superheater can be increased while always maintaining the superheater in the superheated state. . Next, after the pressure and temperature on the upstream side of the superheater become equal to or higher than the operating pressure and temperature of the main steam line, the valves 6a and 6b are opened to supply the steam from the evaporator 3 to the superheater. Thereby, even if the steam from the evaporator 3 is a saturated steam or a steam having a low degree of superheat, it is possible to reliably prevent the inflow of moisture (condensed water and saturated steam) into the superheater.

According to a preferred embodiment of the present invention, the superheated steam at a constant temperature is gradually supplied to reduce the supply amount just before the saturated steam pressure at the temperature, and then the superheated steam is again increased according to the increase in the steam temperature. And gradually increasing the pressure and temperature while maintaining the steam temperature at or below the saturated steam pressure. In other words, when steam is passed through the steam superheater, the pressure and temperature increase. In this case, since the pressure increase is relatively faster than the temperature increase, the outlet steam temperature of the superheater immediately before the steam supply valve opening operation is measured. Then, the saturated steam pressure at that time-α (pressure lower than the saturated steam pressure) is used as an index of the next valve opening operation amount (SV
Value), and perform the ventilation operation. By repeating this operation, the inside of the superheater is always kept in an overheated state,
The pressure and temperature in the superheater can be increased.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In addition, the same reference numerals are given to the common parts in the respective drawings, and the duplicate description will be omitted. FIG. 1 is a schematic diagram of a sodium steam superheater using the starting method according to the present invention. The starting method of the present invention is a method for starting a steam superheater 1 in which high-temperature liquid sodium is used as a heat medium and indirectly heats steam. As shown in FIG. 14
a superheated steam line 12 for supplying d to the superheater 1, and a steam discharge valve 13.
A steam discharge line 15 for discharging 4 e is provided, and a pressure sensor 16 and a temperature sensor 17 for detecting pressure and temperature on the upstream side of the superheater 1 are provided.

Further, the pressure sensor 16 and the temperature sensor 17 may be provided on the downstream side of the superheater 1, and either or both of the outputs may be used. In this case, the superheater 1
Due to the heating by the liquid sodium 2 inside, the pressure and the temperature on the downstream side are usually higher than those on the upstream side.

Each of the superheated steam valve 11 and the steam discharge valve 13 is a flow rate control valve, and the flow rate can be controlled by the control device 18. The control device 18 is, for example, a computer including a storage device, and is configured to input detection outputs of the pressure sensor 16 and the temperature sensor 17. As the superheated steam 14d supplied from the superheated steam line 12, it is preferable to use superheated steam having a higher pressure and temperature than the steam of the main steam line supplied from the valve 6a. The other parts are the same as those of the conventional sodium steam superheater shown in FIG.

FIG. 2 is a pressure / temperature diagram of steam schematically showing the method of the present invention. In this figure, the horizontal axis represents pressure (atg) and the vertical axis represents temperature (° C.). The curve A in the figure is a saturated steam curve. The lower side of the curve indicates a supersaturated steam region including moisture, and the upper side of the curve indicates a superheated steam region.

According to the method of the present invention, in the apparatus shown in FIG. 1, while the valves 6a and 6b of the main steam line are closed, the steam is discharged from the steam discharge valve 13 and the superheated steam 14d is discharged from the superheated steam valve 11. The pressure and the temperature on the upstream side of the superheater 1 are detected by the pressure sensor 16 and the temperature sensor 17, and the detected pressure and the detected temperature are maintained in the superheated steam region shown in FIG. The pressure and temperature in 1 are gradually increased. According to this method, the pressure and temperature in the superheater 1 can be increased while the upstream and downstream sides of the superheater 1 are always kept in an overheated state.

In FIG. 2, a curve B represents a superheated steam line 1.
2 is an isenthalpy curve of the superheated steam 14d supplied from Step 2. In this example, a case where superheated steam having a temperature of 369 ° C. and 127 atg and a degree of superheat of about 41 ° C. is used is shown. In addition, a zigzag straight line C in the drawing indicates the pressure / temperature state of steam in the superheater according to the present invention. That is, as shown by a zigzag straight line C in FIG. 2, a state in which the valves 6a and 6b of the main steam line are closed and a constant temperature (20 in FIG.
0 ° C.) is gradually supplied to reduce the supply amount before the saturated steam pressure (about 15 atg) at this temperature. The temperature gradually rises due to heat transfer. Then, the superheated steam 14d is supplied again in accordance with the rise of the steam temperature, and as shown by a zigzag straight line in the figure, the pressure and the temperature are gradually increased while maintaining the steam temperature at or below the saturated steam pressure, thereby superheating the steam. The pressure and temperature in the superheater 1 can be increased while keeping the upstream side and the downstream side of the vessel 1 always in an overheated state.

Next, after the pressure and temperature in the superheater 1 become equal to or higher than the operating pressure and temperature of the main steam line, the valves 6a and 6b are opened to supply steam from the evaporator 3 to the superheater. Thereby, even if the steam from the evaporator 3 is a saturated steam or a steam having a low degree of superheat, it is possible to reliably prevent the inflow of moisture (condensed water and saturated steam) into the superheater.

In the embodiment of FIG. 1, the superheated steam line 12 is used in addition to the main steam line. However, when the steam from the evaporator 3 of the main steam line is a superheated steam having a sufficiently high degree of superheat. Can omit the superheated steam line 12 and use the main steam line valve 6a (main steam supply valve) as the above-described superheated steam valve 11. Therefore,
The present invention does not use an external heat source (warming with auxiliary steam, heating with a heater, etc.) as a measure to prevent the inflow of moisture when ventilating a superheater, and simplifies equipment and increases thermal efficiency by devising operation operations. Can be expected to improve plant efficiency.

It should be noted that the present invention is not limited to the above-described embodiment, but can be variously modified without departing from the gist of the present invention.

[0020]

As described above, the method for starting a steam superheater using sodium according to the present invention includes the steps of:
That is, when steam is passed through the superheater, it is possible to prevent moisture (condensed water and saturated steam) from flowing into the superheater, furthermore, it is possible to omit an external heat source, simplify the equipment,
It has excellent effects such as an increase in thermal efficiency.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a sodium steam superheater using the starting method according to the present invention.

FIG. 2 is a pressure / temperature state diagram of steam schematically illustrating the method of the present invention.

FIG. 3 is a schematic view of a conventional sodium superheater.

[Explanation of symbols]

 Reference Signs List 1 steam superheater (superheater) 1a sodium container 1b heat transfer tube 2 sodium 3 evaporator (evaporator) 3a feed water pump 4a steam 4b superheated steam 4c condensed water 4d superheated steam 4e drain 5 steam turbine 6a, 6b valve 7a auxiliary boiler Steam valve 12 Superheated steam line 13 Steam exhaust valve 14d Superheated steam 14e Steam 15 Steam exhaust line 16 Pressure sensor 17 Temperature sensor 18 Controller

Claims (2)

[Claims] 1. A method for starting a steam superheater in which steam is indirectly heated by using high-temperature liquid sodium as a heat medium, comprising: a superheated steam valve having a superheated steam valve for supplying superheated steam to the superheater from the valve; A steam discharge line that has a valve and discharges steam passing through the superheater from the valve, a pressure sensor and a temperature sensor that detects pressure and temperature on the upstream side of the superheater, and superheated steam while discharging steam from the steam discharge valve Slowly supply superheated steam from the valve, detect the pressure and temperature on the upstream side of the superheater, and gradually increase the pressure and temperature in the superheater while maintaining the detected pressure and detected temperature in the superheated steam area. A method for starting a steam superheater using sodium. 2. Superheated steam at a constant temperature is gradually supplied to reduce the supply amount just before the saturated steam pressure at the temperature, and then superheated steam is supplied again as the steam temperature rises. The method for starting a steam superheater using sodium according to claim 1, wherein the pressure and temperature are gradually increased while maintaining the steam pressure or lower.