JP3907730B2 - Turbine water injection system for geothermal power plant - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a geothermal power plant that uses geothermal steam as steam for driving a turbine, and more particularly to a turbine water injection device that effectively prevents scales and the like from adhering to steam passages such as nozzles and blades.
[0002]
[Prior art]
In geothermal power plants, since the steam source is geothermal steam taken out from the geothermal well, it is known that the scale in the steam precipitates in the process of expanding in the steam turbine and adheres to the steam passages of the nozzles and blades as crystals. It has been. When a large amount of scale adheres to the steam passage portion, the steam passage area is remarkably reduced, and the turbine output is greatly reduced due to a reduction in the amount of steam flowing into the steam turbine. For this reason, it is necessary to periodically stop the geothermal power plant, disassemble the steam turbine, and remove scales from nozzles, blades and the like.
[0003]
An example of a conventional geothermal power plant will be described with reference to FIG. Turbine driving steam is taken out through the production well 1 from a place called a reservoir in which high-temperature hot water in the ground is stored. This steam flows into the separator 2, where the scale in the steam is removed, and then is led from the main steam pipe 3 to the steam turbine 6 through the main stop valve 4 and the steam control valve 5, where it expands and works. Do.
[0004]
The steam that has passed through the steam turbine 6 is discharged to a condenser 7 where it is condensed and becomes circulating water. This circulating water is extracted by the circulating water pump 8 and sent to the cooling tower 9 where it is cooled by the outside air. The cooled circulating water flows into the condenser 7 due to a pressure difference between the condenser 7 and the water tank below the cooling tower 9, and is used as cooling water for the steam that has finished work in the steam turbine 6. In the figure, reference numeral 10 denotes a generator driven by the steam turbine 6.
[0005]
[Problems to be solved by the invention]
As described above, the geothermal steam used as turbine driving steam includes a scale, which is deposited in the course of the expansion of the steam and adheres to the steam passages such as nozzles and blades. In particular, when a large amount of scale adheres to the nozzle, the amount of steam flowing into the steam turbine 6 decreases due to the reduction of the passage area, and the turbine output decreases.
[0006]
The relatively large scale contained in the geothermal steam is removed by the separator 8 before flowing into the steam turbine 6, but the fine scale is difficult to be completely removed by the separator 8, which flows into the steam turbine 6. Therefore, it is unavoidable that it adheres to steam passages such as nozzles and blades.
[0007]
For this reason, the geothermal power plant must be periodically stopped and the scale adhering to the steam passage portion must be removed to such an extent that the turbine performance is not affected. However, power generation during this stop is impossible, and it is required to reduce the number of stops. In addition, the scale once attached to the nozzles and blades cannot be easily removed, and a great amount of labor and cost are spent for removing the scale. Accordingly, an object of the present invention is to provide a turbine water injection device for a geothermal power plant that prevents the turbine from being lowered due to the scale adhering to the nozzles and blades, and reduces the number of times the plant is stopped for scale removal. It is to provide.
[0008]
[Means for Solving the Problems]
In the invention according to claim 1, the geothermal steam sent from the production well through the main steam pipe is led to the steam turbine as the main steam to be expanded, and the finished steam is discharged to the condenser and condensed, In a turbine water injection apparatus for a geothermal power plant in which the obtained condensed water is extracted together with circulating water from the condenser with a circulating water pump and guided to a cooling tower, the spray water is refined and the main steam pipe passes through the main steam pipe. A spray water system including at least two injection nozzles for injecting into the steam, a pump for supplying the pressurized spray water to the injection nozzle, and a main steam passing through the main steam pipe in the spray water system the note and the flow is water injection valve to stop the water spray of the spray water system when reduced, a flow meter for detecting the flow rate of the main steam flowing through the main steam pipe, based on a signal from the flow meter And a controller for closing the valve, maintains an equilibrium state between the main steam flow rate and the main steam pipe of the spray water, spray water commensurate with the main steam flow rate detected by the flow meter and When one or a plurality of the injection nozzles are selected and used to obtain a desired particle size, and the balance between the spray water amount and the main steam flow rate is lost, the controller A water injection valve for a geothermal power plant, wherein the water injection valve is closed on the basis of the signal .
[0010]
The invention according to claim 2 is a turbine water injection device for a geothermal power plant, characterized in that circulating water extracted from a condenser is pressurized by a pump and supplied to an injection nozzle as spray water. .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the structure same as the structure by the prior art shown in FIG. 4, and description is abbreviate | omitted.
[0012]
In FIG. 1, an injection nozzle 11 is provided on the path of a main steam pipe 3 that connects a separator 2 and a steam turbine 6, and sprays the spray water in the steam finely. In the present embodiment, a total of four injection nozzles 11 (one is not shown) are provided, and these are arranged at regular intervals. In order to supply spray water to each injection nozzle 11, a spray water pipe 12 branched from the discharge side of the circulating water pump 8 and reaching the injection nozzle 11 is connected. An injection pump 13 is provided in the path of the spray water pipe 12 to increase the pressure of the spray water to a pressure higher than the pressure of the main steam pipe 3. Furthermore, a water injection valve 14 is provided on the discharge side of the injection pump 13 to automatically open and close by a signal from a controller described later.
[0013]
A flow meter 15 is provided downstream of the steam control valve 5 of the main steam pipe 3, and the detected steam flow rate is input to the controller 16. A controller 16 having a logic circuit described later outputs a control signal to the drive portion of the injection valve 14.
[0014]
Furthermore, a strainer 17 is interposed in the path of the spray water pipe 12 to remove foreign substances contained in the spray water extracted from the circulating water. Further, a flow meter 18 is provided on the downstream side of the strainer 17, and a spray water flow rate is detected for monitoring. Reference numeral 19 denotes a check valve for preventing geothermal steam from flowing into the spray water pipe 12.
[0015]
Next, the operation of the turbine water injection apparatus having the above configuration will be described.
[0016]
During plant operation, the circulating water stored in the hot well of the condenser 7 is supplied to the cooling tower 9 by the circulating water pump 8. When the injection pump 13 is started for cleaning the nozzles and blades, the circulating water extracted from the discharge side of the circulating water pump 8 to the spray water pipe 12 passes through the strainer 17 and the water injection valve 14 as spray water to each injection nozzle 11. To flow. The spray water flowing to the injection nozzle 11 is blown out into the steam flowing through the main steam pipe 3 while maintaining a predetermined particle diameter.
This atomized spray water flows with the steam over the nozzles and vanes and cleans the scale before it solidifies on the surface of the steam passage. Thereby, it is possible to prevent the scale from adhering to the nozzles and the blades even during the turbine operation.
[0017]
The characteristics of the injection nozzle 11 will be described in detail with reference to FIG. The vertical axis represents the average particle diameter of the spray water and the spray flow rate, and the horizontal axis represents the difference between the water injection differential pressure, that is, the pressure in the main steam pipe 3 and the nozzle discharge pressure of the spray water. As shown in the figure, the average particle diameter of the spray water decreases as the water injection differential pressure increases, and conversely, the spray flow rate increases as the water injection differential pressure increases. This figure shows per injection nozzle. The characteristics in the case of using a plurality of water injection nozzles have the characteristic that the value of the average particle diameter does not change, but the spray flow rate increases in proportion to the increase.
[0018]
On the other hand, for the steam turbine 6, the influence of the inflow amount of spray water and the erosion of the blades and nozzles of the particle diameter is extremely large, and the best consideration is required.
[0019]
The inflow amount of the spray water needs to be a value proportional to the inflow amount of the steam, and the particle size a to b in the figure is an allowable range for the particle size. Thereby, the range of the water injection differential pressure is determined from the particle diameter c to d. Due to this water injection differential pressure, the spray water flow rate of the injection nozzle 11 changes from e to f. Therefore, in the present embodiment, at least two injection nozzles 11 are arranged in the main steam pipe 3, and the injection nozzle 11 to be used is appropriately selected. Thereby, it becomes possible to maintain the amount of spray water and a desired particle diameter corresponding to the main steam flow rate.
[0020]
Further, in the present embodiment, the main steam flow rate is detected by the flow meter 15 so that a balance between a predetermined spray water amount and the turbine load (steam flow rate) is maintained. If, for some reason, the equilibrium state is lost and the amount of spray water becomes excessively large, the water injection valve 14 is closed by a signal from the controller 16. Thereby, the flow of spray water can be stopped.
[0021]
An example of a logic circuit for controlling the water injection valve 14 is shown in FIG. In this embodiment, the amount of spray water is set so as to achieve equilibrium at a turbine load (steam flow rate) of 90% or more. When the flow meter 15 detects that the steam flow rate has decreased to 90% or less when the water injection valve 14 is fully open, the water injection valve 14 is fully closed by a control signal from the controller 16.
[0022]
In the present embodiment, the circulating water is pressurized by the injection pump 13 and supplied as spray water, and the total head of the pump that maintains the pressure required for the spray water can be reduced.
[0023]
As described above, in the above-described turbine water injection device, even when the flow rate of the steam flowing into the steam turbine 6 fluctuates, it is possible to inject while maintaining the appropriate amount of spray water and maintaining a desired particle diameter. It is possible to prevent erosion from occurring.
[0024]
In addition, although the spray water pipe 12 in said embodiment guides the circulating water extracted on the discharge side of the circulating water pump 8 as spray water, the spray water obtained from another water source other than this is each injection nozzle 11. You may lead to.
[0025]
【The invention's effect】
As described above, according to the first aspect of the present invention, spray water is injected into the main steam pipe by the injection nozzle connected to an arbitrary water source, so that the turbine output is reduced due to the scale adhering to the nozzle and the blade. It is possible to prevent this, and it is possible to reduce the frequency of stopping the plant for removing the scale.
[0026]
Further, in the invention according to claim 1, since the injection nozzle is provided at least two, selected and used these injection nozzles, to hold the proper spray water and the desired particle size commensurate with the steam flow rate It is possible to prevent the blades and nozzles from being eroded.
[0027]
The invention according to claim 1, since in order to detect the geothermal steam flow by the flow meter arranged in the main steam pipe, when the equilibrium between the spray water and steam flow is lost, closes the injection valve It is possible to prevent an excessive amount of spray water from entering the steam turbine and damaging the turbine components.
[0028]
Furthermore, in the invention according to claim 2 , since the circulating water extracted from the condenser is pressurized by the pump and supplied as spray water, the total head of the pump that maintains the pressure required for the spray water The turbine water injection device can be simply configured.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an embodiment of a turbine water injection apparatus according to the present invention.
FIG. 2 is a diagram showing characteristics of an injection nozzle.
FIG. 3 is a circuit diagram showing a logic circuit used for controlling a water injection valve.
FIG. 4 is a system diagram showing a conventional geothermal power plant.
[Explanation of symbols]
1 Production Well 3 Main Steam Pipe 6 Steam Turbine 11 Injection Nozzle 13 Injection Pump 14 Water Injection Valves 15 and 18 Flow Meter 16 Controller

Claims (2)

The geothermal steam sent from the production well through the main steam pipe is led to the steam turbine as the main steam and expanded, and the finished steam is discharged to the condenser and condensed, and the resulting condensed water is circulated. In addition, a turbine water injection device for a geothermal power plant extracted from the condenser with a circulating water pump and led to a cooling tower,
At least two injection nozzles for atomizing spray water into the main steam passing through the main steam pipe;
A spray water system including a pump for supplying the spray water by increasing pressure over the injection nozzle;
A water injection valve for stopping the spray water of the spray water system when the flow rate of the main steam passing through the main steam pipe in the spray water system decreases;
A flow meter for detecting a flow rate of main steam flowing in the main steam pipe;
A controller for closing the water injection valve based on a signal from the flow meter ,
To maintain an equilibrium state between the flow rate of the spray water and the main steam flow rate in the main steam pipe, either the amount of spray water corresponding to the main steam flow rate detected by the flow meter or a desired particle diameter is selected. One or more injection nozzles are selected and used, and when the balance between the spray water amount and the main steam flow is lost, the water injection valve is closed based on a signal from the controller. A turbine water injection device for a geothermal power plant, characterized by comprising The turbine water injection apparatus for a geothermal power plant according to claim 1 , wherein circulating water extracted from the condenser is pressurized by the pump and supplied to the injection nozzle as spray water .

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