JPS60132006A - Gas extracting system of geothermal power plant - Google Patents

Abstract

PURPOSE:To prevent valves from being stuck due to the adherence of silica scale by injecting the compressed fresh water from outside to control valves discharging the drain from coolers to a condenser. CONSTITUTION:The uncondensed gas 2 extracted from a condenser 1 is guided to the first-stage cooler 4 together with the drive steam 7, and the drain is discharged to the condenser 1 via a control valve 10. The drain of the second- stage cooler 6 is discharged to the condenser 1 via a control valve 11. The control valves 10, 11 are periodically opened or closed depending on drain levels of the coolers 4, 6. Furthermore, the fresh water 12 is invariably fed to the gap between the valve stem 17 and the main body 16 of each of the control valves 10, 11. Accordingly, the valves can be prevented from being stuck due to the adherence of silica scale.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas extraction system for a geothermal power plant.

Conventionally, in the gas extraction system of a geothermal power plant, as shown in Fig. 1, non-condensable gas 2 is extracted from the condenser 1 using several stages of ejectors 3.5, etc., and the vacuum inside the condenser 1 is released. I kept it.

In this case, in order to send only non-condensable gas 2 to the next stage ejector, the steam used to drive the ejector is cooled and drained (
Equipped with a cooler 4.6 for water). Also, a cooler 6 is attached after the final stage ejector 5,
This is provided to drain the steam, since if the steam is released into the atmosphere together with the non-condensable gas 2, it will turn into white smoke and cause an environmental problem.

Note that the cooler 4.6 usually has a structure in which cooling water 21 is sprayed to condense steam. Since the drain 8.9 (water condensed with steam and cooling water) produced by the cooler 4.6 has a pressure lower than atmospheric pressure, the discharge destination is the condenser 1 whose pressure is also lower.

Since there is a pressure difference between the condenser 24.6 and the condenser 10, a U-seal 19 is provided in the drain 8.9 pipe to maintain this difference.

The height of the U-seal 19 needs to be greater than the pressure difference between the cooler 4.6 and the condenser 1, for example, if the pressure difference is 0 or 4 kVC.
, I is 4 m or more, and 0 , 9 kVC, 1 is 9 m or more. These long U-seal pipes 19 not only require a considerable amount of space for arrangement, but also require digging a hole underground for the U-seal pipes 19 when the condenser 1 is placed on the ground. It may be necessary to ensure the seal length l.

In short, the conventional U-seal method has the following drawbacks.

(a) Since condensers are usually located above ground, U
A pit must be dug underground for the seal piping.

(bl) Because a long U-seal must be provided, the piping arrangement becomes complicated and extra space is required.

(C) Due to changes in operating conditions such as changes in cooling water temperature,
Since the required U-seal length changes, if there is not enough margin in the U-seal length, the U-seal length will be insufficient and the U-seal will break, and the once extracted non-condensable gas 2 will be returned to the condenser 1.
The condenser vacuum may deteriorate.

The above U, which was conventionally used as a drain discharge method for the cooler.
Since this system has the above-mentioned drawbacks, the present invention uses a control valve instead of a U-seal in an attempt to solve this problem.The novelty of the present invention is simply that a control valve is used instead of a U-seal. When using a cooler, the silica contained in the cooler train adheres to the gap between the control valve stem and the main body, causing the valve to become stuck and becoming uncontrollable. To prevent the valve from sticking due to silica scale, run clean water between the valve stem and valve body to prevent scale from adhering to the gap, and open and close the control valve at the drain level in the cooler. By constantly opening and closing the valve periodically, the stick is made waterproof.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

A gas extraction system according to the invention is shown in FIG.

The non-condensable gas 2 extracted from the condenser 1 by the first stage ejector 3 is guided to the first stage cooler 4 together with the driving steam 7.
The steam becomes drain by the cooling water 21 and is discharged to the condenser 1 through the control valve 10.

Next, the non-condensable gas 2 from the first stage cooler 4 is extracted by the second (3) stage ejector 5, and the non-condensable gas 2 is extracted together with the driving steam 7
The steam enters the stage cooler 6, becomes drain by the cooling water 21, and is discharged to the condenser 1 through the control valve 11 and the drain line 9. From the second stage cooler 6, only the non-condensable gas 2 is released 20 to the atmosphere.

The control valves 10 and 11 are opened and closed by electrical signals from a high level switch 14 and a low level switch 13 attached to the cooler, as shown in FIG. or control valve 10.1
1, pressurized fresh water 12 is extracted. Note that the control valve 10. ．． Stop valves and bypass valves are provided upstream and downstream for repair in the event of a failure.

Next, the action and effects will be described.

Control valve 10.11 controls the drain discharged from cooler 4.6.
Cooler 4.
The internal pressure of No. 6 is maintained.

When the condensate level of the cooler 4.6 rises and the high level switch 14 is activated, the control valve 10.11 opens and the condensate is discharged to the condenser 1, the condensate level gradually decreases, and the low level switch 13 is activated. When the voltage drops to a level at which the level switch 13 operates (4), the electric signal from the level switch 13 closes the control valves 10 and 11, and the discharge of condensate to the condenser 1 is stopped.

When drain discharge to the condenser 1 is stopped, the drain level in the cooler 4.6 gradually rises again, and when the level of the high level switch 14 rises, the control valve 10.11 is opened again by an electric signal. . The control valves 10, 11 are periodically opened and closed to maintain a range of drain levels. Control valves 10 and 11 are supplied with fresh water 1 pressurized from the outside.
2 is inserted into the gap between the valve stem 17 and the main body 16 to prevent drain from the cooler 4.6 from constantly entering the gap. A portion of the extracted fresh water 12 enters the drain flowing through the valve, and a portion still leaks outside the valve and is discharged to the drain pit 15 or the like.

With the above configuration and operation, the present invention provides the following effects.

(al Control valve 10.11 for drain from cooler 4.6
Since the condenser is discharged to the condenser 1, the conventional U-seal is no longer necessary, and accordingly, the U-seal focus, which conventionally requires a large amount of construction cost, is no longer necessary.

(1)) Since the control valves 10.11 are periodically opened and closed depending on the trend level of the cooler 4.6, the problem of valve stickiness caused by silica scale adhesion, which is peculiar to geothermal water, is eliminated.

(C) Since fresh water 12 is constantly flowing into the gap between the valve stem 17 and the main body 16 of the control valve 10.11, silica-containing tolen will not enter this gap, so silica scale will adhere to the gap and the valve will become damaged. It won't be like sticking.

(d) In the conventional U-seal method, the required U-seal length changes due to changes in operating conditions such as changes in cooling water temperature.

In the unlikely event that there is not enough margin in the U-seal length, the U-seal will break and the non-condensable gas extracted from the condenser will return to the condenser, causing problems such as not being able to obtain the required condenser vacuum. Occur. However, since the U-seal is stopped and the control valve is operated at the cooler drain level, it can also be adapted to changes in operating conditions as described above.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing a conventional gas extraction system, Fig. 2 is a system diagram according to the system of the present invention, Fig. 3 is a system diagram showing the control method of the control valve, and Fig. 4 shows the configuration of the control valve. FIG. 1. Condenser, 2. Non-condensable gas, 3. 1st stage ejector, 4. 1st stage cooler, 5. 2nd stage ejector,
6. 2nd stage cooler, 7. Drive steam, 8, 9. Fist drain line, 10.11φ-control valve, 12.. M water, 1
3...Low level switch, 14 High level switch, 15
...Drain pit, 16.. Main body, 17.. Valve stem.

Claims (1)

[Claims] In gas extraction systems using ejectors in geothermal power plants, we prevent valves from sticking due to silica scale by constantly opening and closing periodically within the appropriate range of the drain level of the cooler, and we also prevent valves from sticking in the gaps between the valve stem and the main body. A gas extraction system for a geothermal power generation plant, characterized by extracting clean water and discharging cooler drain after an ejector to a condenser using a control valve having a mechanism to prevent scale-containing drain from entering gaps.