Scale suppression apparatus, geothermal power generation system using the same, and scale suppression method

A scale suppression apparatus capable of suppressing in a low-priced manner the generation of silica-based scale and calcium-based scale in the influent water containing at least a silica component and a calcium component, a geothermal power generation system using the same, and a scale suppression method are provided. The scale suppression apparatus includes a chelating agent and alkaline agent addition unit injecting liquid containing a chelating agent and an alkaline agent into a pipe arrangement through which influent water such as geothermal water or the like flows, and a controller controlling a pump and a valve of the chelating agent and alkaline agent addition unit. The controller controls the injection of the chelating agent and the alkaline agent and stops of the injection based on the signal output from a scale detection unit for detecting a precipitation state of the scale.

TECHNICAL FIELD

The present disclosure relates to a scale suppression apparatus, a geothermal power generation system using the same, and a scale suppression method.

BACKGROUND

After a geothermal power generation system generates power by using steam or hot water blown out of a production well, the hot water—the temperature of which has dropped—is made to return to an injection well. Since the hot water of high temperature blown out of the production well contains more calcium and dissolved silica than those in the well water or the river water, scale such as calcium carbonate or amorphous silica is easily precipitated. In particular, in the terrestrial part and in the injection well, there is a problem of suppressing generation of silica scale due to the temperature drops of hot water in the terrestrial part.

Generally, a sulfuric acid injection method is used as a suppression method of the silica scale. In the sulfuric acid injection method, the polymerization rate of silica is suppressed by lowering the pH of hot water to reduce the scale precipitation amount. However, as the sulfuric acid injection method merely decreases the polymerization rate of silica, silica is expected to be precipitated after a sufficient time passes in the injection well. In addition, as the sulfate ion density increases, the possibility that scale such as anhydrite or the like is precipitated increases. Further, there is a problem that piping or the like is eroded with acid.

As an attempt to solve these problems, there is a method of alkalizing hot water (for example, see Daisuke Fukuda,Geothermal Technology, Vol. 34, Nos. 1 & 2 (Ser. No 74) 51-57, 2009) (hereinafter “Fukuda”). In other words, the solubility of amorphous silica becomes higher as the alkalinity become higher, and it suddenly rises at pH 8 or more, in particular. Therefore, silica scale is hardly generated in a high pH solution. Further, this effect continues in the injection well, since the silica precipitation amount does not increase even if the time passes, which contrasts with the above-mentioned method of suppressing the rate of silica polymerization. Furthermore, disclosed is a method of suppressing the precipitation of calcium carbonate, anhydrite, or magnesium silicate in the production well, by also using a chelating agent of catching calcium or magnesium in the production well.

BRIEF SUMMARY

In the method disclosed in Fukuda, the chelating agent is injected into the production well, whereas an alkaline agent is injected into its terrestrial part. However, a sufficient amount of chelating agent catches the calcium ion, and the generation of calcium silicate hydrates (hereinafter, simply referred to as CSH) can be prevented, whereas a large amount of the chelating agent is demanded to be injected. In general, the chelating agent is an expensive agent, and there is a problem of not being economical.

In order to address the above drawback, in a first aspect of the present disclosure there is provided a scale suppression apparatus of injecting a chelating agent and an alkaline agent into influent water containing at least a silica component and a calcium component to suppress generation of scale, the scale suppression apparatus comprising a controller configured to alternately switch between an injection operation of injecting the chelating agent and the alkaline agent and stopping of the injection operation.

With such a configuration, while the injection of the chelating agent and the alkaline agent stops, amorphous silica of super saturation is precipitated, whereas while the chelating agent and the alkaline agent are being injected, the precipitated amorphous silica can be dissolved. On the other hand, while the alkaline agent is being injected, compounds (for example, CSH) are precipitated by reacting with polyvalent metal ions unless a sufficient amount of chelating agent is injected. However, by stopping the injection of the alkaline agent, the compounds can be dissolved. By alternately repeating the injection operation of the chelating agent and the alkaline agent and the stopping of the injection operation, it is possible to minimize the use amount of the chelating agent, which is an expensive agent. Both the amorphous silica and the compounds can be dissolved alternately, and the scale can be suppressed in the long term.

In a second aspect of the present disclosure, the controller may be configured to alternately switch between the injection operation and the stopping of the injection operation at a predefined interval.

With such a configuration, switching can be operated automatically at a predefined interval by a timer function of the controller.

In a third aspect of the present disclosure, the scale suppression apparatus may further comprise a scale detection unit configured to detect a precipitation state of the scale on a downstream side from an injection point into which the chelating agent and the alkaline agent are injected, and the controller may be configured to include: a memory configured to store an output signal from the scale detection unit; and a calculation unit configured to calculate an index of the injection operation based on the output signal from the scale detection unit. The controller may also be configured to control switching between the injection operation of injecting the chelating agent and the alkaline agent and the stopping of the injection operation by comparing a calculation result of the calculation unit with an upper limit threshold and a lower limit threshold.

With such a configuration, the injection operation of the chelating agent and the alkaline agent and the stopping of the injection operation can be determined automatically according to the output value from the scale detection unit.

In a fourth aspect of the present disclosure, the scale detection unit may include: a scale precipitation unit; an upstream-side manometer configured to measure a pressure on an upstream side from the scale precipitation unit and output a signal to the controller; and a downstream-side manometer configured to measure a pressure on a downstream side from the scale precipitation unit and output a signal to the controller.

With such a configuration, the controller calculates a pressure difference between the output values from the manometers before and after the scale precipitation unit. When the pressure difference is higher than the upper limit threshold or is lower than the lower limit threshold, the injection operation of injecting the chelating agent and the alkaline agent and the stopping of the injection operation are switched. Accordingly, it is possible to automatically dissolve amorphous silica and compounds alternately in accordance with the pressure difference that varies depending on the adhesion amount of the scale at the scale precipitation unit. It is to be noted that instead of the provisions of the upstream-side manometer and the downstream-side manometer, a differential manometer for obtaining the pressure difference before and after the scale precipitation unit may be used to input a pressure difference signal output from the differential manometer into the controller.

In a fifth aspect of the present disclosure, the scale detection unit may include: a scale precipitation unit; and a flowmeter configured to measure a flow rate of an upstream side or a downstream side from the scale precipitation unit and output a signal to the controller. The controller may obtain a value by subtracting a subsequent flow rate from the flow rate below the lower limit threshold.

With such a configuration, the controller calculates a value obtained by subtracting a subsequent flow rate of the flowmeter from the flow rate of the flowmeter when the injection of the chelating agent and the alkaline agent stops. When the flow rate difference is higher than the upper limit threshold or lower than the lower limit threshold, the injection operation of injecting the chelating agent and the alkaline agent and the stopping of the injection operation are switched. Accordingly, it is possible to automatically dissolve amorphous silica and compounds alternately in accordance with the pressure difference that varies depending on the adhesion amount of the scale at the scale precipitation unit.

In a sixth aspect of the present disclosure, there is provided a geothermal power generation system comprising: an evaporator configured to evaporate a medium with geothermal water; a turbine configured to rotate with the medium; a power generator coupled to the turbine and configured to generate the power with rotational power of the turbine; a condenser configured to condense the medium come out of the turbine; a circulation pump configured to feed the medium condensed by the condenser to the evaporator; and a scale suppression unit according to any one of the above first through fifth aspects, configured to use the geothermal water that has passed through the evaporator as influent water.

With such a configuration, it is possible to suppress the generation of amorphous silica and CSH adhered to the pipe arrangement above the ground or in the injection well, and to reduce the maintenance frequency of the pipe arrangement above the ground and in the injection well.

In a seventh aspect of the present disclosure, there is provided a scale suppression method of suppressing generation of scale by injecting a chelating agent and an alkaline agent into influent water containing at least a silica component and a calcium component, the scale suppression method comprising: a first step of injecting the chelating agent and the alkaline agent; and a second step of stopping injecting the chelating agent and the alkaline agent, where the first step and the second step are alternately switched.

With such a method, in the first step of injecting the chelating agent and the alkaline agent into the influent water, it is possible to dissolve amorphous silica that has already been generated by increasing the solubility of amorphous silica. In the second step of stopping the injection of the chelating agent and the alkaline agent, it is possible to dissolve the compounds generated in the first step. The use amount of the chelating agent that is an expensive agent is minimized, both of amorphous silica and the compounds are dissolved alternatively, and the scale can be suppressed in the long term.

According to the present disclosure, in the influent water containing at least a silica component and a calcium component, it is possible to suppress in a low-priced manner the generation of silica-based scale and calcium-based scale.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described with reference to the drawings. It is to be noted that the present disclosure is not limited to the following embodiments, and the embodiments may be changed as necessary without departing from the scope of the present disclosure.

First Embodiment

FIG. 1is a schematic configuration view of a scale suppression apparatus according to a first embodiment of the present disclosure. The scale suppression apparatus according to the first embodiment of the present disclosure is an apparatus of suppressing the generation of silica-based scale and calcium-based scale occur in influent water containing at least a silica component and a calcium component, and includes a pipe arrangement L1, a chelating agent and alkaline agent addition unit40, a scale detection unit60, a pipe arrangement L10, and a controller11.

The pipe arrangement L1leads the influent water that has flowed from an influent water inlet12to the scale detection unit60, and one end of the pipe arrangement L1is connected to an inlet part of the scale detection unit60.

The chelating agent and alkaline agent addition unit40injects liquid containing chelating agent and alkaline agent into the influent water flowing through the pipe arrangement L1, and includes a tank6configured to reserve the liquid containing the chelating agent and alkaline agent, a pump8configured to inject the liquid reserved in the tank6into the pipe arrangement L1, a pipe arrangement L6configured to connect a liquid outlet port of the tank6and an inlet port of the pump8, and a pipe arrangement L5configured to connect an exhaust port of the pump8and an injection port of the pipe arrangement L1.

In addition, the chelating agent and alkaline agent addition unit40has a valve7for opening and closing the intake side of the pump8, and the valve7is arranged in a partway of the pipe arrangement L6.

The scale detection unit60detects a precipitation state of the scale on a downstream side from the injection point where the chelating agent and alkaline agent are injected, and includes a scale precipitation unit16configured to precipitate the scale generated in the influent water. The scale precipitation unit16has a pipe line in which, for example, the influent water flows. The cross section of the flow path in the pipe line is changed as the scale is adhered to the inner face of the pipe line.

In addition, the scale detection unit60includes an upstream-side manometer17configured to detect an upstream-side pressure of the scale precipitation unit16, and a signal output from the upstream-side manometer17is supplied to controller11as upstream-side pressure information of the scale precipitation unit16. Further, the scale detection unit60has a downstream-side manometer18configured to detect a downstream-side pressure of the scale precipitation unit16, and a signal output from the downstream-side manometer18is supplied to the controller11as downstream-side pressure information of the scale precipitation unit16.

The pipe arrangement L10supplies the influent water that has flown through the scale detection unit60to an injection well13, and one end of the pipe arrangement L10is connected to an outlet unit of the scale detection unit60.

The controller11controls the pump8and the valve7based on the precipitation state of the scale detected by the scale detection unit60. The controller11includes a memory24configured to store the pressure measured by the manometers17and18of the scale detection unit60, a calculation unit25configured to calculate a difference in pressure between the upstream-side pressure measured by the manometer17and the downstream-side pressure measured by the manometer18, and a comparison unit26configured to compare the pressure difference calculated by the calculation unit25with an upper limit threshold and a lower limit threshold.

It is to be noted that the controller11is connected to an input-output unit, not illustrated, so that the input-output unit can change various set values and take out data.

In the scale suppression apparatus in the first embodiment, as illustrated inFIG. 6, a first step S2of injecting from the chelating agent and alkaline agent addition unit40the liquid containing the chelating agent and alkaline agent into the pipe arrangement L1through which the influent water flows, and a second step S3of stopping the injection of the liquid containing the chelating agent and alkaline agent are switched alternately in a switch step S1to suppress the generation of the scale. In this case, the first step S2may be carried out earlier and then the second step S3may be carried out later, or the second step S3may be carried out earlier and then the first step S2may be carried out later.

When the first step S2is carried out earlier, scale (for example, CSH) is gradually precipitated at the scale precipitation unit16of the scale detection unit60. The output value (i.e., pressure difference) from the scale detection unit60increases gradually as the first step S2proceeds, as illustrated inFIG. 7. Then, when the output value (i.e., pressure difference) from the scale detection unit60exceeds the upper limit threshold, the first step S2is switched to the second step S3, and the operation of the chelating agent and alkaline agent addition unit40stops.

When the first step S2is switched to the second step S3, the scale (for example, CSH) precipitated at the scale precipitation unit16is dissolved, and the output value (i.e., pressure difference) from the scale detection unit60decreases, accordingly. Then, when the output value (i.e., pressure difference) from the scale detection unit60becomes lower than the lower limit threshold, the second step S3is switched to the first step S2, and the liquid containing the chelating agent and alkaline agent is added from the chelating agent and alkaline agent addition unit40to the pipe arrangement L1. Subsequently, as discussed above, the first step S2and the second step S3are repeated alternately.

On the other hand, when the second step S3is carried out earlier, amorphous silica is precipitated at the scale precipitation unit16of the scale detection unit60. In this situation, the output value (i.e., pressure difference) from the scale detection unit60gradually increases as the second step S3proceeds, as illustrated inFIG. 8. Then, when the output value (i.e., pressure difference) of the scale detection unit60exceeds the upper limit threshold, the second step S3is switched to the first step S2, and the liquid containing the chelating agent and alkaline agent is added from the chelating agent and alkaline agent addition unit40to the pipe arrangement L1.

When the second step S3is switched to the first step S2, amorphous silica precipitated by the scale precipitation unit16is dissolved, the output value (i.e., pressure difference) from the scale detection unit60decreases, accordingly. Then, when the output value (i.e., pressure difference) from the scale detection unit60becomes lower than the lower limit threshold, the first step S2is switched to the second step S3, and the operation of the chelating agent and alkaline agent addition unit40stops. Subsequently, as discussed above, the second step S3and the first step S2are repeated alternately.

In the first step S2, the pump8is activated together with opening of the valve7. Then, the liquid (i.e., liquid containing the chelating agent and alkaline agent) reserved in the tank6flows through the pipe arrangements L6and L5, and is injected into the pipe arrangement L1.

In the second step S3, the pump8is stopped together with closing the valve7. This stops the injection operation of the liquid (i.e., liquid containing the chelating agent and alkaline agent) which has been injected into the pipe arrangement L1from the chelating agent and alkaline agent addition unit40.

By carrying out the above-described first step S2and second step S3alternately in many variations as described above, the generation of the scale can be suppressed.

FIG. 9illustrates relationships between precipitate and dissolved substance in a case where the liquid containing the chelating agent and alkaline agent is injected into the influent water (i.e., first step S2) and in a case where the injection of the liquid containing the chelating agent and alkaline agent is stopped (i.e., second step S3). When the liquid containing the chelating agent and alkaline agent is injected into the pipe arrangement L1through which the influent water flows from the chelating agent and alkaline agent addition unit40, the liquid reacts with polyvalent metal ions contained in the influent water, and compounds (for example, CSH) are precipitated, and in addition, amorphous silica is dissolved. Then, when the injection of the liquid containing the chelating agent and alkaline agent is stopped, amorphous silica is precipitated, and in addition, compounds precipitated (for example, CSH) by reacting with polyvalent metal ions are dissolved.

In the first embodiment, when the pressure difference calculated by the calculation unit25of the controller11reaches the upper limit threshold, a valve close signal is sent from the controller11to the valve7of the chelating agent and alkaline agent addition unit40, and a pump stop signal is also sent from the controller11to the pump8of the chelating agent and alkaline agent addition unit40. Accordingly, the pump8is in a stopped state together with closing the valve7of the chelating agent and alkaline agent addition unit40. The injection of the liquid containing the chelating agent and alkaline agent stops.

Further, the injection of the liquid containing the chelating agent and alkaline agent stops. When the pressure difference calculated by the calculation unit25of the controller11reaches the lower limit threshold, a valve open signal is sent from the controller11to the valve7of the chelating agent and alkaline agent addition unit40, and a pump activation signal is also sent from the controller11to the pump8of the chelating agent and alkaline agent addition unit40. Accordingly, the pump8is in an activation state together with opening of the valve7of the chelating agent and alkaline agent addition unit40. The injection of the liquid containing the chelating agent and alkaline agent is restarted.

As in the first embodiment, the first step S2of injecting the liquid containing the chelating agent and alkaline agent into the influent water and the second step S3of stopping the injection of the liquid containing the chelating agent and alkaline agent are switched alternately, so that the added amounts of the chelating agent and the alkaline agent can be reduced and reduction of the cost can be achieved.

In addition, the scale generated in the influent water is detected by the scale detection unit60. The injection of the chelating agent and alkaline agent is controlled based on the signal output from the scale detection unit60, so that the added amounts of the chelating agent and the alkaline agent can be reduced more.

Second Embodiment

In the above-described first embodiment, the chelating agent and alkaline agent addition unit configured to inject the liquid containing the chelating agent and alkaline agent into the pipe arrangement L1through which the influent water flows includes the tank6configured to reserve the liquid containing the chelating agent and alkaline agent, the pump8configured to inject the liquid reserved in the tank6into the pipe arrangement L1, the pipe arrangement L6configured to connect the outlet port of the tank6and the inlet port of the pump8, the pipe arrangement L5configured to connect the exhaust port of the pump8and the injection port of the pipe arrangement L1, and the valve7arranged in the partway of the pipe arrangement L6has been illustrated. However, the present disclosure is not limited to the above configuration. As illustrated inFIG. 2, for example, in a second embodiment, the chelating agent and alkaline agent addition unit40configured to inject the liquid containing the chelating agent and alkaline agent into the pipe arrangement L1through which the influent water flows may include a tank6aconfigured to reserve the liquid containing the chelating agent, a tank6bconfigured to reserve the liquid containing the alkaline agent, the pump8configured to inject the liquid reserved in the tanks6aand6binto the pipe arrangement L1, the pipe arrangement L6configured to connect the outlet port of the tank6aand the inlet port of the pump8, the pipe arrangement L7configured to connect the outlet port of the tank6band the inlet port of the pump8, the pipe arrangement L5configured to connect the exhaust port of the pump8and the injection port of the pipe arrangement L1, and valves7aand7barranged in pathways of the pipe arrangements L6and L7, respectively.

Third Embodiment

FIG. 3is a schematic configuration view of the scale suppression apparatus according to a third embodiment of the present disclosure. The scale suppression apparatus according to the third embodiment, as illustrated inFIG. 3, includes the pipe arrangement L1, the chelating agent and alkaline agent addition unit40, the scale detection unit60, pipe arrangements L17and L18, valves19and20, and the controller11.

The pipe arrangement L1leads the influent water that has flowed from an influent water inlet12to the scale detection unit60, and one end of the pipe arrangement L1is connected to the inlet part of the scale detection unit60.

The chelating agent and alkaline agent addition unit40injects the liquid containing the chelating agent and alkaline agent into the influent water flowing through the pipe arrangement L1. The chelating agent and alkaline agent addition unit40includes the tank6configured to reserve the liquid containing the chelating agent and alkaline agent, the pump8configured to inject the liquid reserved in the tank6into the pipe arrangement L1, the pipe arrangement L6configured to connect the liquid outlet port of the tank6and the inlet port of the pump8, and the pipe arrangement L5configured to connect the exhaust port of the pump8and the injection port of the pipe arrangement L1.

In addition, the chelating agent and alkaline agent addition unit40has the valve7for opening and closing the intake side of the pump8, and the valve7is arranged in the pathway of the pipe arrangement L6. Further, the chelating agent and alkaline agent addition unit40has a valve23for opening and closing a discharge side of the pump8, and the valve23is arranged in the pathway of the pipe arrangement L5. It is to be noted that the valve23is not necessarily provided, but the provision of the valve23on the discharge side of the pump8enables the maintenance with ease when a failure occurs at the pump8.

The scale detection unit60detects the precipitation state of the scale on a downstream side from the injection point into which the chelating agent and alkaline agent are injected, and includes the scale precipitation unit16configured to precipitate the scale generated in the influent water. The scale precipitation unit16has a pipe line through which, for example, the influent water flows, and the cross section of the flow path in the pipe line is changed as the scale is adhered to the inner face of the pipe line.

In addition, the scale detection unit60includes the upstream-side manometer17configured to detect the upstream-side pressure of the scale precipitation unit16, and the signal output from the upstream-side manometer17is supplied to controller11as the upstream-side pressure information of the scale precipitation unit16. Further, the scale detection unit60has the downstream-side manometer18configured to detect the downstream-side pressure of the scale precipitation unit16, and the signal output from the downstream-side manometer18is supplied to the controller11as the downstream-side pressure information of the scale precipitation unit16.

The pipe arrangement L17supplies the influent water that has flowed through the scale detection unit60to an acidity injection well15, and is connected to an inlet part of the acidity injection well15.

The pipe arrangement L18supplies the influent water that has flowed through the scale detection unit60to an alkalinity injection well14, and is connected to an inlet part of the alkalinity injection well14.

The valve19blocks the influent water that has flowed through the scale detection unit60from being injected into the alkalinity injection well14, and is arranged in a pathway of the pipe arrangement L18.

The valve20blocks the influent water that has flowed through the scale detection unit60from being injected into the acidity injection well15, and is arranged in a pathway of the pipe arrangement L17.

The controller11controls the pump8and the valves7,19,20, and23based on the precipitation state of the scale detected by the scale detection unit60. The controller11includes the memory24configured to store the pressures measured by the manometers17and18of the scale detection unit60, the calculation unit25configured to calculate a pressure difference between the upstream-side pressure measured by the manometer17and the downstream-side pressure measured by the manometer18, and the comparison unit26configured to compare the pressure difference calculated by the calculation unit25with an upper limit threshold and a lower limit threshold so as to determine on and off of the pump8or opening and closing of the valves7,19,20, and23.

In the scale suppression apparatus in the third embodiment, as illustrated inFIG. 6, the first step S2of injecting the liquid containing the chelating agent and alkaline agent into the pipe arrangement L1through which the influent water flows, from the chelating agent and alkaline agent addition unit40and the second step S3of stopping the injection of the liquid containing the chelating agent and alkaline agent are switched alternately in a switch step S1to suppress the generation of the scale. In this case, the first step S2may be carried out earlier and then the second step S3may be carried out later, or the second step S3may be carried out earlier and then the first step S2may be carried out later.

In the third embodiment, when the first step S2is carried out earlier, scale (for example, CSH) is gradually precipitated at the scale precipitation unit16of the scale detection unit60. The output value (i.e., pressure difference) from the scale detection unit60increases gradually as the first step S2proceeds, as illustrated inFIG. 7. Then, when the output value (i.e., pressure difference) from the scale detection unit60exceeds the upper limit threshold, the first step S2is switched to the second step S3, and the operation of the chelating agent and alkaline agent addition unit40stops.

When the first step S2is switched to the second step S3, the scale (for example, CSH) precipitated at the scale precipitation unit16is dissolved, and the output value (i.e., pressure difference) from the scale detection unit60decreases accordingly. Then, when the output value (i.e., pressure difference) from the scale detection unit60becomes lower than the lower limit threshold, the second step S3is switched to the first step S2, and the liquid containing the chelating agent and alkaline agent is added from the chelating agent and alkaline agent addition unit40to the pipe arrangement L1. Subsequently, as discussed above, the first step S2and the second step S3are repeated alternately.

On the other hand, when the second step S3is carried out earlier, for example, amorphous silica is precipitated at the scale precipitation unit16of the scale detection unit60. In this situation, the output value (i.e., pressure difference) from the scale detection unit60gradually increases as the second step S3proceeds, as illustrated inFIG. 8. Then, when the output value (i.e., pressure difference) of the scale detection unit60exceeds the upper limit threshold, the second step S3is switched to the first step S2, and the liquid containing the chelating agent and alkaline agent is added from the chelating agent and alkaline agent addition unit40to the pipe arrangement L1.

When the second step S3is switched to the first step S2, amorphous silica precipitated at the scale precipitation unit16is dissolved, and the output value (i.e., pressure difference) of the scale detection unit60decreases, accordingly. Then, when the output value (i.e., pressure difference) from the scale detection unit60becomes lower than the lower limit threshold, the first step S2is switched to the second step S3, and the operation of the chelating agent and alkaline agent addition unit40stops. Subsequently, as discussed above, the second step S3and the first step S2are repeated alternately.

In the first step S2, the pump8is activated together with opening of the valves7,19, and23and closing of the valve20. Then, the liquid (i.e., liquid containing the chelating agent and alkaline agent) reserved in the tank6flows through the pipe arrangements L6and L5, and is injected into the pipe arrangement L1. In addition, the influent water exhausted from the scale detection unit60is supplied to the alkalinity injection well14, flowing through the pipe arrangement L18.

In the second step S3, the pump8is stopped together with closing of the valves7,19, and23and opening of the valve20so as to stop the injection of the liquid containing the chelating agent and alkaline agent.

By carrying out the above-described first step S2and second step S3alternately in many variations as described above, the generation of the scale can be suppressed.

When the liquid containing the chelating agent and alkaline agent is injected into the pipe arrangement L1through which the influent water flows, from the chelating agent and alkaline agent addition unit40, the liquid reacts with polyvalent metal ions contained in the influent water, and compounds (for example, CSH) are precipitated. In addition, amorphous silica is dissolved, as illustrated inFIG. 9. Then, when the injection of the liquid containing the chelating agent and alkaline agent is stopped, amorphous silica is precipitated. Further, compounds precipitated (for example, CSH) by reacting with polyvalent metal ions are dissolved.

In the third embodiment, when the pressure difference calculated by the calculation unit25of the controller11reaches the upper limit threshold, the valve close signals are sent from the controller11to the valves7,19, and23, and the pump stop signal is also sent from the controller11to the pump8of the chelating agent and alkaline agent addition unit40. Accordingly, the pump8is in a stopped state together with closing of the valves7,19, and23. The injection of the liquid containing the chelating agent and alkaline agent stops.

Furthermore, in this situation, the valve20is opened by the valve open signal from the controller11, and the influent water which has flowed through the scale detection unit60is supplied to the acidity injection well15, flowing through the pipe arrangement L17.

The injection of the liquid containing the chelating agent and alkaline agent stops. When the pressure difference calculated by the calculation unit25of the controller11reaches the lower limit threshold, the valve close signal is sent to the valve20from the controller11. Moreover, in this situation, the valve open signals are sent from the controller11to the valves7,19, and23, and the pump activation signal is also sent from the controller11to the pump8. Accordingly, the pump8is in an activation state together with opening of the valves7,19, and23. The injection of the liquid containing the chelating agent and alkaline agent is restarted. Then, the influent water which has flowed through the scale detection unit60is supplied to the alkalinity injection well14, flowing through the pipe arrangement L18.

As in the third embodiment, the first step of injecting the liquid containing the chelating agent and alkaline agent into the influent water and the second step of stopping the injection of the liquid containing the chelating agent and alkaline agent are switched alternately, so that the added amounts of the chelating agent and the alkaline agent can be reduced and reduction of the cost can be achieved.

In addition, the scale generated in the influent water is detected by the scale detection unit60, and the injection of the chelating agent and alkaline agent is controlled based on the signal output from the scale detection unit60. In this way, the added amounts of the chelating agent and the alkaline agent can be reduced more.

Fourth Embodiment

FIG. 4is a schematic configuration view of a scale suppression apparatus according to a fourth embodiment of the present disclosure. The scale suppression apparatus according to the fourth embodiment of the present disclosure, as illustrated inFIG. 4, includes the pipe arrangement L1, the chelating agent and alkaline agent addition unit40, a scale detection unit61, the pipe arrangement L10, and the controller11. The pipe arrangement L1leads the influent water that has flowed from the influent water inlet12to the scale detection unit61, and one end of the pipe arrangement L1is connected to an inlet part of the scale detection unit61.

The chelating agent and alkaline agent addition unit40injects the liquid containing the chelating agent and alkaline agent into the influent water flowing through the pipe arrangement L1. The chelating agent and alkaline agent addition unit40includes the tank6configured to reserve the liquid containing the chelating agent and alkaline agent, the pump8configured to inject the liquid reserved in the tank6into the pipe arrangement L1, the pipe arrangement L6configured to connect a liquid outlet port of the tank6and an inlet port of the pump8, and the pipe arrangement L5configured to connect an exhaust port of the pump8and an injection port of the pipe arrangement L1.

In addition, the chelating agent and alkaline agent addition unit40has the valve7for opening and closing the intake side of the pump8, and the valve7is arranged in the pathway of the pipe arrangement L6.

The scale detection unit61detects the precipitation state of the scale on a downstream side from the injection point where the chelating agent and the alkaline agent are injected. The scale detection unit61includes the scale precipitation unit16configured to precipitate the scale generated in the influent water. The scale precipitation unit16has a pipe line through which, for example, the influent water flows. The cross section of the flow path in the pipe line is changed, as the scale is adhered to the inner face of the pipe line.

Further, the scale detection unit61includes a flowmeter21configured to measure a flow rate of the influent water flowing into the scale precipitation unit16from the pipe arrangement L1, and a signal output from the flowmeter21is supplied to the controller11.

The pipe arrangement L10supplies the influent water that has flowed through the scale detection unit61to the injection well13, and one end of the pipe arrangement L10is connected to an outlet part of the scale detection unit61.

The controller11controls the pump8and the valve7based on the precipitation state of the scale detected by the scale detection unit61. The controller11includes the memory24configured to store the flow rate of the influent water (i.e., flow rate below a lower limit threshold) measured by the flowmeter21of the scale detection unit61, the calculation unit25configured to calculate a flow rate difference between the flow rate measured by flowmeter21after the chelating agent and the alkaline agent are injected and the flow rate stored in the memory24, and the comparison unit26configured to compare the flow rate difference calculated by the calculation unit25with an upper limit threshold and a lower limit threshold.

In the scale suppression apparatus in the fourth embodiment, as illustrated inFIG. 6, the first step S2of injecting from the chelating agent and alkaline agent addition unit40the liquid containing the chelating agent and alkaline agent into the influent water flowing through the pipe arrangement L1and the second step S3of stopping the injection of the liquid containing the chelating agent and alkaline agent are switched alternately in a switch step S1to suppress the generation of the scale. In this case, the first step S2may be carried out earlier and then the second step S3may be carried out later, or the second step S3may be carried out earlier and then the first step S2may be carried out later.

In the fourth embodiment, when the first step S2is carried out earlier, scale (for example, CSH) is gradually precipitated at the scale precipitation unit16of the scale detection unit61. The output value (i.e., flow rate difference) from the scale detection unit61increases gradually as the first step S2proceeds, as illustrated inFIG. 7. Then, when the output value (i.e., flow rate difference) from the scale detection unit61exceeds the upper limit threshold, the first step S2is switched to the second step S3, and the operation of the chelating agent and alkaline agent addition unit40stops.

When the first step S2is switched to the second step S3, the scale (for example, CSH) precipitated at the scale precipitation unit16is dissolved, and the output value (i.e., flow rate difference) from the scale detection unit61decreases, accordingly. Then, when the output value (i.e., flow rate difference) from the scale detection unit61becomes lower than the lower limit threshold, the second step S3is switched to the first step S2, and the liquid containing the chelating agent and alkaline agent is added from the chelating agent and alkaline agent addition unit40to the pipe arrangement L1. Subsequently, as discussed above, the first step S2and the second step S3are repeated alternately.

On the other hand, when the second step S3is carried out earlier, for example, amorphous silica is precipitated at the scale precipitation unit16of the scale detection unit61. In this situation, the output value (i.e., flow rate difference) from the scale detection unit61gradually increases as the second step S3proceeds, as illustrated inFIG. 8. Then, when the output value (i.e., flow rate difference) of the scale detection unit61exceeds the upper limit threshold, the second step S3is switched to the first step S2, and the liquid containing the chelating agent and alkaline agent is added from the chelating agent and alkaline agent addition unit40to the pipe arrangement L1.

When the second step S3is switched to the first step S2, amorphous silica precipitated at the scale precipitation unit16is dissolved, and the output value (i.e., flow rate difference) from the scale detection unit61decreases accordingly. Then, when the output value (i.e., flow rate difference) from the scale detection unit61becomes lower than the lower limit threshold, the first step S2is switched to the second step S3, and the operation of the chelating agent and alkaline agent addition unit40stops. Subsequently, as discussed above, the second step S3and the first step S2are repeated alternately.

In the first step S2, the pump8is activated together with opening the valve7. Then, the liquid containing the chelating agent and alkaline agent is injected into the pipe arrangement L1from the chelating agent and alkaline agent addition unit40.

In the second step S3, the pump8is stopped together with closing the valve7. Then, the injection operation of the liquid containing the chelating agent and alkaline agent stops.

By carrying out the above-described first step S2and second step S3alternately in many variations as described above, the generation of the scale can be suppressed.

When the liquid containing the chelating agent and alkaline agent is injected into the pipe arrangement L1through which the influent water flows, from the chelating agent and alkaline agent addition unit40, as illustrated inFIG. 9, the liquid reacts with polyvalent metal ions contained in the influent water, and compounds (for example, CSH) are precipitated. In addition, amorphous silica is dissolved. Then, when the injection of the liquid containing the chelating agent and alkaline agent is stopped, amorphous silica is precipitated. In addition, compounds precipitated (for example, CSH) by reacting with polyvalent metal ions are dissolved.

In the fourth embodiment, when the flow rate difference calculated by the calculation unit25of the controller11reaches the upper limit threshold, the valve close signal is sent from the controller11to the valve7of the chelating agent and alkaline agent addition unit40. Further, the pump stop signal is also sent from the controller11to the pump8of the chelating agent and alkaline agent addition unit40.

Accordingly, the pump8is in a stopped state together with closing the valve7of the chelating agent and alkaline agent addition unit40. The injection of the liquid containing the chelating agent and alkaline agent stops.

Further, when the injection of the liquid containing the chelating agent and alkaline agent stops and the pressure difference calculated by the calculation unit25of the controller11reaches the lower limit threshold, the valve open signal is sent from the controller11to the valve7of the chelating agent and alkaline agent addition unit40. Also, the pump activation signal is also sent from the controller11to the pump8of the chelating agent and alkaline agent addition unit40. Accordingly, the pump8is in an activation state together with opening the valve7of the chelating agent and alkaline agent addition unit40. The injection of the liquid containing the chelating agent and alkaline agent is restarted.

As in the fourth embodiment, the first step S2of injecting the liquid containing the chelating agent and alkaline agent into the influent water and the second step S3of stopping the injection of the liquid containing the chelating agent and alkaline agent are switched alternately, so that the added amounts of the chelating agent and the alkaline agent can be reduced and reduction of the cost can be achieved.

In addition, the scale generated in the influent water is detected by the scale detection unit61, and the injection of the chelating agent and alkaline agent is controlled based on the signal output from the scale detection unit61, so that the added amounts of the chelating agent and the alkaline agent can be reduced more.

Fifth Embodiment

FIG. 5is a schematic configuration view of a scale suppression apparatus according to a fifth embodiment of the present disclosure. The scale suppression apparatus according to the fifth embodiment of the present disclosure, as illustrated inFIG. 5, includes the pipe arrangement L1, the chelating agent and alkaline agent addition unit40, the scale detection unit61, pipe arrangements L17and L18, valves19and20, and the controller11.

The pipe arrangement L1leads the influent water that has flowed from an influent water inlet12to the scale detection unit61, and one end of the pipe arrangement L1is connected to an inlet part of the scale detection unit61.

The chelating agent and alkaline agent addition unit40injects the liquid containing the chelating agent and alkaline agent into the influent water flowing through the pipe arrangement L1. The chelating agent and alkaline agent addition unit40includes the tank6configured to reserve the liquid containing the chelating agent and alkaline agent, the pump8configured to inject the liquid reserved in the tank6into the pipe arrangement L1, the pipe arrangement L6configured to connect a liquid outlet port of the tank6and an inlet port of the pump8, and the pipe arrangement L5configured to connect an exhaust port of the pump8and an injection port of the pipe arrangement L1.

In addition, the chelating agent and alkaline agent addition unit40has the valve7for opening and closing the intake side of the pump8, and the valve7is arranged in the partway of the pipe arrangement L6. Further, the chelating agent and alkaline agent addition unit40has the valve23for opening and closing a discharge side of the pump8, and the valve23is arranged in the pathway of the pipe arrangement L5. It is to be noted that the valve23is not necessarily provided, but the provision of the valve23on the discharge side of the pump8enables the maintenance with ease when a failure occurs at the pump8.

The scale detection unit61detects the precipitation state of the scale on a downstream side from the injection point into which the chelating agent and alkaline agent are injected, and includes the scale precipitation unit16configured to precipitate the scale generated in the influent water. The scale precipitation unit16has a pipe line through which, for example, the influent water flows. The cross section of the flow path in the pipe line is changed as the scale is adhered to the inner face of the pipe line.

Further, the scale detection unit61includes the flowmeter21configured to measure a flow rate of the influent water flowing into the scale precipitation unit16from the pipe arrangement L1, and the signal output from the flowmeter21is supplied to the controller11.

The pipe arrangement L17supplies the influent water that has flowed through the scale detection unit61to the acidity injection well15, and is connected to the inlet part of the acidity injection well15.

The pipe arrangement L18supplies the influent water that has flowed through the scale detection unit61to the alkalinity injection well14, and is connected to the inlet part of the alkalinity injection well14.

The valve19blocks the influent water that has flowed through the scale detection unit61from being injected into the alkalinity injection well14, and is arranged in the pathway of the pipe arrangement L18.

The valve20blocks the influent water that has flowed through the scale detection unit61from being injected into the acidity injection well15, and is arranged in the pathway of the pipe arrangement L17.

The controller11controls the pump8and the valves7,19,20, and23based on the precipitation state of the scale detected by the scale detection unit61. The controller11includes the memory24configured to store the flow rate of the influent water (i.e., flow rate below the lower limit threshold) measured by the flowmeter21of the scale detection unit61, the calculation unit25configured to calculate a flow rate difference between the flow rate measured by flowmeter21after the chelating agent and the alkaline agent are injected and the flow rate stored in the memory24, and the comparison unit26configured to compare the flow rate difference calculated by the calculation unit25with an upper limit threshold and a lower limit threshold.

In the scale suppression apparatus in the fifth embodiment, as illustrated inFIG. 6, the first step S2of injecting the liquid containing the chelating agent and alkaline agent into the pipe arrangement L1through which the influent water flows, from the chelating agent and alkaline agent addition unit40and the second step S3of stopping the injection of the liquid containing the chelating agent and alkaline agent are switched alternately in the switch step S1to suppress the generation of the scale. In this case, the first step S2may be carried out earlier and then the second step S3may be carried out later, or the second step S3may be carried out earlier and then the first step S2may be carried out later.

When, in the fifth embodiment, the first step S2is carried out earlier, scale (for example, CSH) is gradually precipitated at the scale precipitation unit16of the scale detection unit61. In this situation, the output value (i.e., pressure difference) from the scale detection unit61increases gradually as the first step S2proceeds, as illustrated inFIG. 7. Then, when the output value (i.e., pressure difference) from the scale detection unit60exceeds the upper limit threshold, the first step S2is switched to the second step S3, and the operation of the chelating agent and alkaline agent addition unit40stops.

When the first step S2is switched to the second step S3, the scale (for example, CSH) precipitated at the scale precipitation unit16is dissolved, and the output value (i.e., flow rate difference) from the scale detection unit61decreases, accordingly. Then, when the output value (i.e., flow rate difference) from the scale detection unit61becomes lower than the lower limit threshold, the second step S3is switched to the first step S2, and the liquid containing the chelating agent and alkaline agent is added from the chelating agent and alkaline agent addition unit40to the pipe arrangement L1. Subsequently, as discussed above, the first step S2and the second step S3are repeated alternately.

On the other hand, when the second step S3is carried out earlier, for example, amorphous silica is precipitated at the scale precipitation unit16of the scale detection unit61. In this situation, the output value (i.e., flow rate difference) from the scale detection unit61gradually increases as the second step S3proceeds, as illustrated inFIG. 8. Then, when the output value (i.e., flow rate difference) of the scale detection unit61exceeds the upper limit threshold, the second step S3is switched to the first step S2, and the liquid containing the chelating agent and alkaline agent is added from the chelating agent and alkaline agent addition unit40to the pipe arrangement L1.

When the second step S3is switched to the first step S2, amorphous silica precipitated at the scale precipitation unit16is dissolved, and the output value (i.e., pressure difference) of the scale detection unit60decreases, accordingly. Then, when the output value (i.e., pressure difference) from the scale detection unit60becomes lower than the lower limit threshold, the first step S2is switched to the second step S3, and the operation of the chelating agent and alkaline agent addition unit40stops. Subsequently, as discussed above, the second step S3and the first step S2are repeated alternately.

In the first step S2, the pump8is activated together with the opening of the valves7,19, and23and closing of the valve20. Then, the liquid containing the chelating agent and alkaline agent is injected into the pipe arrangement L1through which the influent water flows.

In the second step S3, the pump8is stopped together with the closing of the valves7,19, and23and opening of the valve20, so as to stop the injection of the liquid containing the chelating agent and alkaline agent.

By carrying out the above-described first step S2and second step S3alternately in many variations as described above, the generation of the scale can be suppressed.

When the liquid containing the chelating agent and alkaline agent is injected into the pipe arrangement L1through which the influent water flows, from the chelating agent and alkaline agent addition unit40, the liquid reacts with polyvalent metal ions contained in the influent water, and compounds (for example, CSH) are precipitated. In addition, amorphous silica is dissolved, as illustrated inFIG. 9. Then, when the injection of the liquid containing the chelating agent and alkaline agent is stopped, amorphous silica is precipitated. In addition, compounds precipitated (for example, CSH) by reacting with polyvalent metal ions are dissolved.

In the fifth embodiment, when the pressure difference calculated by the calculation unit25of the controller11reaches the upper limit threshold, the valve close signals are sent from the controller11to the valves7,19, and23, and the pump stop signal is also sent from the controller11to the pump8of the chelating agent and alkaline agent addition unit40. Accordingly, the pump8is in a stopped state together with the closing of the valves7,19, and23. The injection of the liquid containing the chelating agent and alkaline agent stops.

Furthermore, in this situation, the valve20is opened by the valve open signal from the controller11, and the influent water which has flowed through the scale detection unit60is supplied to the acidity injection well15, flowing through the pipe arrangement L17.

The injection of the liquid containing the chelating agent and alkaline agent stops, and when the pressure difference calculated by the calculation unit25of the controller11reaches the lower limit threshold, the valve close signal is sent to the valve20from the controller11. Moreover, in this situation, the valve open signals are sent from the controller11to the valves7,19, and23, and the pump activating signal is also sent from the controller11to the pump8. Accordingly, the pump8is activated together with the closing of the valve20and opening of the valves7,19, and23. The injection of the liquid containing the chelating agent and alkaline agent is restarted. Then, the influent water which has flowed through the scale detection unit60is supplied to the alkalinity injection well14, flowing through the pipe arrangement L18.

As in the fifth embodiment, the first step of injecting the liquid containing the chelating agent and alkaline agent into the influent water and the second step of stopping the injection of the liquid containing the chelating agent and alkaline agent are switched alternately, so that the added amounts of the chelating agent and the alkaline agent can be reduced and reduction of the cost can be achieved.

In addition, the scale generated in the influent water is detected by the scale detection unit61, and the injection of the chelating agent and alkaline agent is controlled based on the signal output from the scale detection unit61, so that the added amounts of the chelating agent and the alkaline agent can be reduced more.

Sixth Embodiment

Next, a sixth embodiment of the present disclosure will be described with reference toFIG. 10. The sixth embodiment of the present disclosure is related to a geothermal power generation system including a scale suppression apparatus100illustrated inFIG. 1,FIG. 2, orFIG. 4. Specifically, the geothermal power generation system includes an evaporator71configured to evaporate the medium with geothermal water taken out of a production well70, a turbine72configured to rotate with the medium evaporated by the evaporator71, a power generator73configured to be coupled to the turbine72and generate the power with the rotational power of the turbine72, a condenser74configured to condense the medium come out of the turbine72, and a circulation pump75configured to feed the medium condensed by the condenser74to the evaporator71, so that the geothermal water that has passed through the evaporator71is used as the influent water to the scale suppression apparatus100. The geothermal water that has come out of the scale suppression apparatus100is supplied to the injection well13. The power generated by the power generator73is input into a conditioner77through power wiring76, is converted into a desired voltage current by the conditioner77, and is then output through power output wiring78to the exterior.

Seventh Embodiment

Next, a seventh embodiment of the present disclosure will be described with reference toFIG. 10. The seventh embodiment of the present disclosure is related to a geothermal power generation system including a scale suppression apparatus101illustrated inFIG. 3orFIG. 5. Specifically, the geothermal power generation system includes the evaporator71configured to evaporate the medium with geothermal water taken out of the production well70, the turbine72configured to rotate with the medium evaporated by the evaporator71, the power generator73configured to be coupled to the turbine72and generate the power with the rotational power of the turbine72, the condenser74configured to condense the medium that has come out of the turbine72, and the circulation pump75configured to feed the medium condensed by the condenser74to the evaporator71, so that the geothermal water that has passed through the evaporator71is used as the influent water to the scale suppression apparatus101. Alkali discharged water that has come out of the scale suppression apparatus101is made to flow into the alkalinity injection well14, whereas acid discharged water is made to flow into the acidity injection well15. The power generated by the power generator73is input into the conditioner77through the power wiring76, is converted into a desired voltage current by the conditioner77, and is then output through the power output wiring78to the exterior.

With such a configuration, it is made possible to prevent the alkaline water and acid water from being mixed together to become neutral at the discharged destination. It is therefore possible to reduce the frequency of maintenance by suppressing the generation of scale.

In the first to seventh embodiments, as illustrated inFIG. 8, the second step S3of stopping the injection of the chelating agent and the alkaline agent is performed earlier, and then the first step S2of injecting the chelating agent and the alkaline agent is performed later. In this manner, it is possible to reduce the amounts of the chelating agent and the alkaline agent, as compared to the method of performing the first step S2earlier as illustrated inFIG. 7.

It is to be noted that when the chelating agent is added at a mol concentration equal to the calcium ion concentration, there are few metals that can be caught by the chelating agent except for calcium in the case of the geothermal water, and the chelating agent will catch all calcium in the geothermal water. Accordingly, CSH may not be precipitated. Therefore, when insufficient chelating agent is added, CSH will be piled up before silica is dissolved and the output value will not become lower than the lower limit threshold. Therefore, it is desirable that the chelating agent concentration be reduced little by little from the mol concentration equal to the calcium ion concentration, so that the output from the scale detection unit becomes lower than the lower limit threshold in the first step.

Heretofore, according to each of the embodiments of the present disclosure, it is possible to suppress the generation of the silica-based scale and the calcium-based scale in a cheaper method than adding the chelating agent to the influent water containing at least the silica component and the calcium component.