JPH06221106A - Nozzle speed governing type geothermal turbine - Google Patents

Abstract

PURPOSE:To prevent output reduction due to scale adhesion and accumulation to a first stage nozzle so as to improve operation efficiency by dividing a steam chamber of a nozzle speed governing type geothermal into a first steam chamber which is used with its output up to the rated load, a second steam chamber, and a third chamber which are used one by one when output is reduced lower than a specific value. CONSTITUTION:The steam port of a geothermal turbine is divided by a partition board 10 so as to divide a steam chamber 3 and steam inlet pipes 2a, 2b, 2c having mutually separated steam adjustment first valve 1a, second valve 1b, and third valve 1c are connected thereto. Only the first valve 1a, the divided steam chamber, and a first stage nozzle 4a are operated up to the rated load, and when output is reduced remarkably due to scale adhesion to the first stage nozzle 4a, steam is introduced from the second valve 2b to a first stage nozzle 4b, and when scale adhesion is developed, output is recovered by the use of the third valve 3c and a first stage nozzle 4c. Thus the output reduction is compensated by opening the second valve and subsequent so that turbine stoppage times for inspections and cleaning can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nozzle-controlled geothermal turbine in which steam entering a steam chamber from a steam inlet pipe circulates around the entire circumference of the steam chamber and flows into a first stage nozzle in an axial direction.

[0002]

2. Description of the Related Art As is well known, a geothermal steam turbine plant pumps out underground geothermal energy in the form of steam or hot water from a geothermal well, and in the case of steam, removes impurities with a separator, etc. In the case of water, it is the most practical power generation plant as an energy-saving facility that converts steam with a flasher and drives a steam turbine using these steams as a drive medium to generate electricity.

However, as described above, since geothermal steam is used, mixed scales (silicon, sulfur, sodium, boron, chlorine, various metal elements and other impurities in the geothermal steam) mixed in the inside of the turbine are in operation. In particular, it adheres to the steam passage consisting of nozzles and blades and accumulates over time, obstructing the flow of steam inside the turbine, leading to reduced turbine output and reduced efficiency. This is a problem. Efforts are of course made to remove impurities before the geothermal steam enters the turbine, but it is not possible to do so completely. Especially in the first stage nozzle, the scale easily attaches and accumulates on its surface,
It is usually unavoidable that the output drops significantly in a relatively short period of time.

FIG. 3 is a schematic diagram showing the structure of a conventional geothermal steam turbine. Steam inlet pipe 2 controlled by steam control valve 1
The steam that has entered the steam chamber 3 further wraps around the entire circumference in the steam chamber 3 and flows into the first stage nozzle 4 in the axial direction. The steam expanded by the first-stage nozzle 4 hits the first-stage blade 5, and the velocity energy of the steam is converted into a rotational torque. Similarly, in the second and subsequent stages, the expansion is repeated in the nozzle group 6 and the blade group 7, the rotor 8 rotates, and the generator 9 is driven.

FIG. 4 is an aged deterioration curve of the conventional geothermal steam turbine described in FIG. 3 (a turbine output decrease curve due to scale adhesion to the first stage nozzle). In FIG. 4, the horizontal axis represents the time (month) from the plant operation start date, and the vertical axis represents the turbine output. In the example of this figure, the output has decreased to point A in 12 months, that is, one year from the first operation day of the plant. At the 12th month, the plant was shut down, the turbine was opened and inspected, the nozzle was scaled down, other maintenance was carried out and reassembled, and the operation was restarted two months later. If you continue to operate the turbine for the second year without stopping it in the first year,
Furthermore, a decrease in output up to point B is expected. The decrease in output from 100% output to point A depends on the properties of geothermal steam,
About 10% to 20% is reported. Generally, if the output is further reduced, it will also hinder stable power supply, so the plant must be stopped and the inspection must be performed. If it is operated up to the second year without periodic inspection, the output will be reduced by 20% to 40%, which will hinder the operation of the turbine itself, and the recovery from this state will occur in the first year. Compared to the case of overhaul inspection, the scale buildup is more severe, so it usually takes more time.

[0006]

As described above, in the conventional geothermal steam turbine, the output of the turbine is reduced due to the deposition and accumulation of the scale on the steam passage, especially on the first stage nozzle, which causes frequent turbine stoppage, open inspection, and internal normality. Will be forced to implement such measures, resulting in a decrease in plant operation rate. An object of the present invention is to eliminate the drawbacks of the prior art and to provide a geothermal turbine with less reduction in plant operation efficiency due to scale deposition.

[0007]

A nozzle speed control type geothermal turbine of the present invention is a nozzle speed control type in which steam entering a steam chamber from a steam inlet pipe circulates around the entire circumference of the steam chamber and axially flows into a first stage nozzle. In the geothermal turbine, a first steam chamber that uses the steam chamber up to the rated load, a second steam chamber that is additionally used when the output of the geothermal turbine falls below a predetermined value, and It is characterized in that it is divided into a third steam chamber which is additionally used when the output of the geothermal turbine falls below a predetermined value while the second steam chamber is being used.

[0008]

As a result, the first steam chamber is used up to the rated load, and the second steam chamber is additionally used when the output of the geothermal turbine drops below a predetermined value. When the output of the geothermal turbine further decreases below a predetermined value while the second steam chamber is being used, the third steam chamber is additionally used, so that the scale is attached to the first stage nozzle. Output drop can be prevented.

[0009]

EXAMPLE An example of the present invention will be described below. FIG. 1 is a schematic diagram showing the structure of a geothermal turbine according to the present invention.

[0010] In the conventional type, the entire circumference is inserted without the partition 10, but in the present invention, as is clear from the figure, there are a plurality of steam inlets (three chambers in this example) partition plate. Separated by 10, each steam room 3a, 3b, 3
c through separate steam control valves 1st valve 1a, 2nd valve 1b, and 3rd valve 1c, and steam inlet pipes 2a, 2b, 2c, respectively.
Are connected. Each steam room 3a, 3b, 3c
The first stage nozzles 4a, 4b, and 4c are assigned to each of the above. That is, structurally, the feature is that the nozzle speed control method is adopted in the geothermal turbine. Among these, the nozzle area of the first stage nozzle 4a is designed to be equal to the nozzle area of the entire circumference of the geothermal turbine according to the conventional technique.

In FIG. 1, after the start of operation, the steam regulating valve first valve 1a, the steam chamber 3a, and the first stage nozzle 4a up to the rated load.
When it is operated only by itself, when the output drop due to scale adhesion and deposition on the first stage nozzle becomes remarkable, the steam control valve 2b 1b is opened, steam is also introduced into the steam chamber 3b, and it is made to flow into the nozzle 4b to perform work, The output reduction due to the scale accumulation on the nozzle 4a of the valve eye is compensated. As the scale adheres further,
The third valve 2c and the nozzle 4c are also used to recover the output, and the operation is continued without performing an open check.

The numbers 1 to 9 among the numbers in FIG. 1 are the same as those in the conventional one in FIG. The steam inlet steam chamber 3 is partitioned in the circumferential direction by a partition plate 10, each steam chamber 3a, 3b, 3c is independent, and the first stage nozzle 4 also depends on the partition angles a, b, c of each steam chamber. It is allocated to 4a, 4b, and 4c by the area ratio of the spout. The nozzle area of the first stage nozzles 4a, 4b, 4c has the same nozzle area as the all-circumferential insertion nozzle 4 of the conventional geothermal turbine described in FIG. 3, that is, the steam control valve No. 1 normally connected to the nozzle 4a. It is possible to operate up to the rated load only by controlling with the 1-valve 1a. On the other hand, second and third
The nozzle area of the second nozzles 4b and 4c is set to about 10% to 20% of that of the nozzle 4a by predicting the tendency of turbine output decrease due to scale accumulation on the first stage nozzle from the operation record of the similar plant. Therefore, the steam control valves 1b and 1c for sending steam to these nozzles can be considerably smaller than the first valve 1a.

Next, the operation of the geothermal turbine according to the present invention described above will be described. Since it was decided that the first stage nozzle 4a could swallow the amount of steam equivalent to the rated load, at the beginning of the operation, it is possible to operate up to the rated load only by opening / closing the steam control valve first valve 1a. When the scale in the geothermal steam begins to adhere and accumulate on the first stage nozzle 4a during operation, it becomes difficult for the steam to pass through and the output starts to decrease. At this time, the nozzle 4 into which steam does not flow
Almost no scale deposit is observed in b and 4c. Normally, the operation is performed for a certain period and then the open inspection is performed. However, in the case of the present invention, the output can be recovered without stopping the turbine by opening the second valve 1b and guiding the steam to the first stage nozzle 4b. it can. If the operation is continued in this state, naturally, the scale will start to accumulate on the nozzle 4b and the output will decrease again. However, at this stage, the output can be recovered by using the third valve and the first stage nozzle 4c. . Only when the scale deposition of the first stage nozzle 4c becomes remarkable, the necessity of opening the turbine arises.

FIG. 2 shows an example of the turbine output reduction curve during this period, together with the conventional case described in FIG. As described in the example of the related art, the horizontal axis is the time (month) from the start of operation, and the vertical axis is the turbine output. In the first year, the output decreases to point A due to scale accumulation.
It is the same as the conventional one, but after this, in the conventional case, the turbine had to be stopped and the open inspection had to be performed.In the case of the present invention,
As described above, opening the second valve restores the output and returns to point C. One year later, when the output again drops to the vicinity of point A ', the third valve is opened and the output is restored to point D. When the output decreases from point D to point A ", since scale has already accumulated considerably over the entire circumference of the first stage nozzle, it is only here that the open inspection is required. For example, while the first regular inspection is performed in the third year, the turbine according to the related art has already completed two regular inspection suspensions, which means that the third inspection is required in the near future. The shaded area is the output gain for the prior art turbine according to the present invention.

In the embodiment described above, the case of three valves and three steam chambers has been described. Of course, if there are multiple valves, any number of partitions may be used. You should plan economically.

[0016]

As described above, according to the present invention, the nozzle cut-off speed control structure is adopted in the geothermal turbine, and the second valve and subsequent valves are sequentially opened to reduce the output due to the output reduction due to scale adhesion and accumulation of the first stage nozzle. Since it is compensated, the number of times the turbine is stopped for open inspection and internal cleaning is reduced to at least half or less, which dramatically improves the plant operation rate.

[Brief description of drawings]

FIG. 1 is a structural schematic diagram showing an embodiment of the present invention.

FIG. 2 is a characteristic diagram of a power reduction curve of a turbine according to the present invention.

FIG. 3 is a structural schematic diagram showing a conventional example.

FIG. 4 is a characteristic diagram of a turbine output reduction curve according to a conventional example.

[Explanation of symbols]

 1 ... Steam control valve 2 ... Steam inlet pipe 3 ... Inlet steam chamber 4 ... First stage nozzle 5 ... First stage blade 6 ... General stage nozzle 7 ... General stage blade 8 ... Rotor 9 ... Generator

Claims (1)

[Claims] 1. In a nozzle-controlled geothermal turbine in which steam that has entered the steam chamber from a steam inlet pipe circulates around the entire circumference of the steam chamber and flows into a first stage nozzle in the axial direction, the steam chamber is operated up to a rated load. The first steam chamber used in the above, the second steam chamber additionally used when the output of the geothermal turbine is lower than a predetermined value, and the geothermal turbine further using the second steam chamber. A nozzle-controlled geothermal turbine characterized by being divided into a third steam chamber for additional use when the output falls below a predetermined value.