JPH10103009A - Steam turbine for geothermal power generation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a countermeasure capable of preventing the generation of corrosion and sticking caused by scale in geothermal steam, and simply applying to the existing steam turbine in the stator blade holding structure of a steam turbine for geothermal power generation. SOLUTION: A stator blade 3 is held in a stator blade holder 2 having upper and lower divided structure, a circumferential groove 2b formed on the outer circumference of the stator blade 2 is fit to a rib-shaped supporting ring 1b projected on the inner circumferential side of an outer casing 1 to support so as to ensure the airtightness in the axial direction. A sheet-shaped anti- corrosion sealing member 5 is interposed between the circumferential groove of the stator blade holder 2 and the supporting ring 1b to fill a gap between them to prevent steam leak passing through the groove in the fitting supporting part and the generation of corrosive drain. As the sealing member, a pressure sensitive adhesive double coated tape formed by applying an adhesive to both surfaces of a fluororesin (Teflon) foamed sheet is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steam turbine for geothermal power generation, and more particularly, to a seal support structure for a stationary blade holder incorporated in a turbine casing.

[0002]

2. Description of the Related Art The internal components of a steam turbine exposed to geothermal steam containing corrosive gas and the like are considered not only for corrosion resistance and erosion but also for ease of maintenance. It is easy to care for, and has a detachable structure so that it can be restored in a short period of time even in the event of trouble that may hinder operation.

FIGS. 2 (a) and 2 (b) show a detachable support structure by a stationary blade holder fitting method employed in a conventional steam turbine for geothermal power generation. In the drawing, reference numeral 1 denotes an outer casing of a turbine, 2 denotes a stationary blade holder in which a stationary blade 3 is implanted for each of a high pressure stage and a low pressure stage, and the stationary blade holder 2 is It is supported as follows.

That is, each of the outer casing 1 and the stationary blade holder 2 has an upper and lower divided structure, and a horizontal flange portion 1 is provided.
a, 2a are fastened by fastening bolts 4 to ensure the airtightness of the divided surface. A rib 2b is formed in the center of the outer peripheral surface of the stationary blade holder 2 along the circumferential direction. The concave groove 2b protrudes toward the inner peripheral surface of the outer casing 1. When the turbine is in operation, the side surface of the concave groove 2b of the stationary blade holder 2 is pressed against the side surface of the support ring 1b with a thrust force generated by a pressure difference between the high pressure side and the low pressure side during turbine operation to hermetically seal steam in the axial direction. The steam is caused to flow along the stationary blade 3 and the rotor blade 5 on the rotor side. The support structure of the stationary blade holder is widely used in ordinary thermal turbines and is well known.

[0005]

By the way, when a geothermal steam is supplied to a steam turbine for geothermal power generation employing the above-mentioned stationary blade holder seal support structure, and a long-term actual operation of the steam turbine is performed, a periodic inspection is performed. It was found that the following problems occurred. That is, 1) local corrosion (corrosion) occurs on the surface of the concave groove 2b of the stationary blade holder 2 and the surface of the support ring 1b of the outer casing 1, and there is a situation where traces of steam flow remain in this portion. . In the assembled structure of the outer casing and the stationary vane holder in which the flanges are bolted between the flanges as an upper and lower two-part structure, if the contact surface pressure of the fitting portion between the two is uniform over the entire circumferential area, For this reason, a humid geothermal steam containing a corrosive gas at a pressure difference between the high pressure side and the low pressure side causes a slight gap g (1 mm) between the support ring 1b and the concave groove 2b.
It is presumed that it flows through the following and condensed and liquefied in the fitting groove to change into a corrosive drain, causing corrosion for a long period of time. The drain generated in the fitting groove remains in the groove without flowing down due to its surface tension because of a narrow gap.

In addition, if the progress of the corrosion caused by such crevice corrosion is left as it is, the leakage of steam from the high pressure side to the low pressure side (the stationary blades do not pass through the blade row of the stationary blades and the moving blades). (Bypassing the outer peripheral side of the holder) increases, and this steam leakage causes energy loss and lowers the efficiency of the turbine, so it is necessary to take some protective measures.

2) The gap between the concave groove 2b of the stationary blade holder 2 and the support ring 1b of the outer casing 1 is fixed to each other by a scale included in the drain, and it is difficult to remove the stationary blade holder 2 from the casing 1. . The present invention has been made in view of the above points, and provides a measure against corrosion so as to prevent generation of corrosion by corrosive drainage and sticking by scale in geothermal steam, and to easily cope with an existing steam turbine. It is an object of the present invention to provide a seal support structure for a stationary blade holder of a steam turbine for geothermal power generation.

[0008]

According to the present invention, in order to achieve the above-mentioned object, according to the present invention, a stationary blade is implanted in a stationary blade holder having an upper and lower two-part structure, and is formed on an outer peripheral surface of the stationary blade holder. In a geothermal power generation steam turbine in which a groove is fitted to a rib-shaped support ring formed to protrude on the inner peripheral side of the outer casing to ensure airtightness in the axial direction, the circumferential groove of the stationary blade holder and the support of the outer casing are supported. It is assumed that a seal member having high corrosion resistance is interposed between the ring and the peripheral surface.

Here, the corrosion-resistant seal member is a sheet-like seal made of a fluororesin-based material, and more specifically, one of the gaps between the circumferential groove of the stationary blade holder and the support ring of the outer casing. It is preferable to use a double-sided pressure-sensitive adhesive tape in which a pressure-sensitive adhesive is applied to both sides of a foam sheet having a thickness of about 0.5 times. When the stationary blade holder is incorporated into the outer casing, the corrosion-resistant sealing member (a fluororesin-based material such as Teflon (DuPont) is attached to a concave groove formed on the peripheral surface of the stationary blade holder or a support ring formed on the outer casing side. Product name): Polytetrafluoroethylene double-sided adhesive tape) is adhered and sealed without leaving a gap between the groove of the stationary blade holder and the support ring of the outer casing. There is no leakage of steam and no generation of corrosive drain at the fitting portion between the stationary blade holder and the outer casing, and the surface of the fitting portion between the stationary blade holder and the outer casing is covered with a corrosion-resistant seal member. There is almost no risk of receiving it. In addition, the fixation of the fitting portion due to the scale can be prevented well.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In the drawings of the embodiment, the same members corresponding to FIG. 2 are denoted by the same reference numerals. That is, FIG.
According to the embodiments (a) and (b), the circumferential groove 2b formed on the outer peripheral surface of the stationary blade holder 2 and the rib-shaped support ring 1b formed to protrude on the inner peripheral side of the outer casing 1 are formed. At the fitting portion, a sheet-like corrosion-resistant seal member 6 is interposed between the two. (B) As shown in the figure, the sealing member 5 is formed by applying a sheet of a foam (closed cell sponge-like foam) made of a fluororesin (Teflon: trade name) as a base material 6a and applying an adhesive 6b to both front and back surfaces thereof. Is a cushioning double-sided pressure-sensitive adhesive tape, the thickness of which is
About 1.5 times the gap (usually 1 mm or less) between the groove and the groove 2b.

Then, the stationary blade holder 2 is attached to the outer casing 1.
When the above-mentioned is installed, the above-mentioned sheet-shaped seal member 6 is attached to the peripheral surface of the concave groove 2b of the stationary blade holder 2 and is fitted into the support ring 1b of the outer casing 1 so that the stationary blade holder 2 is fitted and supported. Then, the sealing member 6 is compressed and hermetically sealed so as to fill the fitting gap between them. Thereby, even when a differential pressure is applied between the high pressure side and the low pressure side across the fitting support portion during the operation of the turbine, there is no steam leakage, no corrosive drain is generated in the groove, and the support ring Since the surfaces of the groove 1b and the groove 2b are covered with the corrosion-resistant sheet-like seal 6, the occurrence of corrosion can be effectively suppressed.

Incidentally, even for a steam turbine already installed and operating at a geothermal power generation site, a special seal is attached to the fitting groove of the outer casing and the stationary blade holder only at the time of the periodic inspection, so that a special condition is obtained. It is possible to easily take measures for preventing corrosion without requiring any processing.

[0013]

As described above, according to the structure of the present invention, the corrosive drain associated with long-term operation can be obtained simply by attaching a simple corrosion-resistant seal member to the fitting groove between the stationary blade holder and the outer casing. Generation in the grooves and corrosion due to corrosive drain can be prevented well, thereby preventing unnecessary steam leakage and turbine efficiency reduction due to the steam leakage. Reliability can be improved.

[Brief description of the drawings]

1A and 1B are diagrams showing a seal support structure of a stationary blade holder according to an embodiment of the present invention, wherein FIG. 1A is a partial cross-sectional view of a fitting support portion between a stationary blade holder and an outer casing, and FIG. )

FIG. 2 is a view showing a seal support structure of a stationary blade holder employed in a conventional steam turbine for geothermal power generation, wherein (a) is a partial sectional view of a fitting support portion between the stationary blade holder and an outer casing;
(b) is a sectional view taken along the line XX.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Outer casing 1a Upper and lower split flange part 1b Support ring 2 Stator blade holder 2a Upper and lower split flange part 3 Stator blade 5 Moving blade 6 Corrosion-resistant sealing member (double-sided adhesive tape) 6a Foam-shaped sheet base 6b Adhesive

Claims (3)

[Claims] A stationary blade is implanted in a stationary blade holder having an upper and lower divided structure, and a circumferential groove formed on an outer peripheral surface of the stationary blade holder is formed on a rib-shaped support ring formed to protrude toward an inner peripheral side of an outer casing. In a steam turbine for geothermal power generation that is fitted and supported so as to ensure airtightness in the axial direction, a highly corrosion-resistant seal member is inserted along the circumferential surface between the circumferential groove of the stationary blade holder and the support ring of the outer casing. A steam turbine for geothermal power generation. 2. The steam turbine for geothermal power generation according to claim 1, wherein the corrosion-resistant seal member is a sheet-like seal made of a fluororesin-based material. 3. The steam turbine according to claim 2, wherein the sheet-like seal has a thickness of about 1.5 times a gap between the circumferential groove of the stationary blade holder and the support ring of the outer casing. A steam turbine for geothermal power generation, characterized in that it is a double-sided adhesive tape having both sides coated with an adhesive.