JP2013064330A - Device for removing air mixed into working medium of electric power generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device which detects air mixed into a medium passage of the device using a medium which is lower in boiling point than water, and automatically removes the mixed air.SOLUTION: The device comprises: an eductor using a liquid medium cooled by a cooler as a drive medium; a first vessel; a pressure gauge which measures the pressure of an air phase part of a passage of a mixed gas; and a temperature gauge which measures a temperature of the passage of the mixed gas. The device also comprises a control part which calculates a pressure threshold obtained by totaling a saturation vapor pressure value of the medium and an excess value which are calculated on the basis of a temperature of the temperature gauge and a pressure value of the pressure gauge, detects that the air is mixed into the medium when the pressure value of the pressure gauge is larger than the pressure threshold, takes the mixed gas out of the passage of the mixed gas by using the eductor by operating the cooler and a pump and transfers it to the first vessel, and performs control for returning the liquid medium which is separated into air and liquid by the first vessel to the passage of the mixed gas via a first valve.

Description

  The present invention relates to an apparatus for removing air mixed in a working medium in a power generation apparatus using a medium having a boiling point lower than that of water as a working medium.

  A power generation apparatus using a low boiling point medium that recovers heat energy from a low-temperature heat source that has not been used in geothermal power generation using a conventional steam turbine has recently attracted special attention as an energy recovery apparatus (Patent Document 1). reference).

  FIG. 5 shows a basic system diagram of a power generator using a conventional low boiling point medium. In this power generation apparatus, the evaporator 100 exchanges heat between a medium having a boiling point lower than that of water and a heat source to evaporate the medium, rotate the turbine 101 with the medium vapor, and rotate the generator 102 with the rotational force. Activate to get power. The medium leaving the turbine is condensed by the condenser 103 and sent to the evaporator 100 again by the circulation pump 104 via the preheater 105, and the above cycle is repeated.

In general, when a medium having a high vapor pressure (ie, a low boiling point) is used, vaporization in the evaporator is easy, but condensing in the condenser becomes difficult, and conversely, the vapor pressure is low (ie, the boiling point is high). ) Use of a medium makes vaporization difficult but condensing is easy. From this viewpoint, the medium to be used is selected such that the enthalpy difference (heat drop) between the turbine inlet and outlet is as large as possible. For example, n-pentane (nC ₅ H ₁₂ ) is mainly used as a natural medium used under conditions of a geothermal heat source temperature of 130 to 140 ° C. and a cooling source temperature of 15 ° C. to 30 ° C.

  Since the cooling source of the condenser is generally circulating cooling water or air, the temperature of the cooling source differs greatly between winter and summer. Therefore, when the condenser is designed only based on the cooling capacity required in the summer, the cooling capacity of the condenser is further enhanced when the cooling source temperature decreases in the winter.

However, as shown in FIG. 3, when the vapor pressure of n-pentane falls below 36 ° C., it becomes 101 kPa or below. There is. Then, there is a possibility that air may be mixed into the medium flow path from various couplings of the condenser main body and its connecting pipe, or a mechanical seal portion of the turbine shaft.
Therefore, Patent Documents 2 to 6 below are known as apparatuses for removing air mixed in a medium in an apparatus related to power generation.

Patent Document 2 discloses a device including an air extraction device for extracting air from the discharge water of a condenser in a binary power generation device that uses water instead of a low boiling point medium.
In Patent Document 3, a working fluid formed by mixing a high-boiling point medium and a low-boiling point medium is composed of a steam generator that generates a steam by heating a solution of the working fluid, and a steam supplied from the steam generator. A steam turbine to be driven, a condenser that cools the steam discharged from the steam turbine and condenses it into a solution, and a supply pump that supplies the solution supplied from the condenser to the steam generator are circulated in this order. The concentration of the low boiling point medium of the working fluid in the condenser is determined so that the lowest pressure that can occur in the condenser in the power cycle circuit is the pressure near the atmospheric pressure. A power system is disclosed.

  In Patent Document 4, a chamber having a piston inside is provided in the upper part of the condenser, and a valve connecting the space below the piston of the chamber and the condenser and the lower part of the chamber are cooled by a coolant through a wall. An apparatus comprising cooling means and a discharge valve connected to the lower part of the chamber is disclosed.

  In Patent Documents 5 and 6, a sealed chamber is provided at the top of the condenser, and this chamber is provided with a movable diaphragm that divides the inside of the chamber into an upper part and a lower part, and is arranged in series between the condenser and the lower part of the chamber. Further, there is disclosed an apparatus including two flow control valves, a cooling means for cooling the lower part of the chamber with a coolant through a wall, and a discharge valve connected to the lower part of the chamber.

  Patent Document 7 discloses a gas extraction system for a geothermal power plant that extracts uncondensed gas from a condenser using several stages of eductors and the like, and maintains a vacuum in the condenser.

JP 62-26304 A JP 2003-120513 A JP 2007-262909 A US Pat. No. 5,119,635 US Patent No. 5,113,927 US Pat. No. 5,487,765 Sho 60-132006

Since the above-mentioned Patent Document 2 uses water as a medium, there is a problem that the heat source must be 100 ° C. or higher and a lower temperature heat source cannot be used.
In Patent Document 3, since the concentration of the low boiling point medium is determined so that the minimum pressure that can occur in the condenser in winter is a pressure close to atmospheric pressure, the condenser pressure in summer increases and the power generation efficiency increases. There has been a problem of lowering.

  The above Patent Documents 4, 5, and 6 disclose an apparatus for removing air from a medium, but the operation timing of the apparatus merely gives an example of periodically operating every 20 minutes. There was a problem that the air removal operation was performed more than necessary, and the amount of medium outflow increased.

  In Patent Document 7, since steam is used to drive the eductor, both the driving steam and the gas taken out from the condenser must be cooled by a subsequent cooler, which causes a problem that the cooling load is large. It was.

  In view of the above problems, an object of the present invention is to provide a mixed air removing device that can automatically detect air mixed in a medium flow path of a power generation device and discharge the mixed air to the outside of the device.

  In order to achieve the above object, the mixed air removing apparatus of the present invention for removing air from a mixed gas of a medium having a boiling point lower than that of water and air includes a cooler for cooling the medium, and the cooled liquid medium And an eductor for sucking the mixed gas from the mixed gas flow path, a pump for supplying a liquid medium to the eductor, and a pipe connected to the discharge part of the eductor and communicating with the atmosphere. A pressure valve for measuring the pressure of a gas phase part of the mixed gas flow path, a first valve provided in a pipe connecting the lower part of the first container and the mixed gas flow path, A thermometer that measures the temperature of the flow path of the mixed gas, and a pressure threshold that is the sum of the saturated vapor pressure value and the margin value of the medium calculated based on the temperature of the thermometer and the pressure value of the pressure gauge The pressure gauge from the pressure threshold When the force value is large, it is detected that air is mixed in the medium, the cooler and the pump are operated, the eductor takes out the mixed gas from the mixed gas flow path, and the first A control unit is provided that performs control to return the liquid medium, which is transferred to the container and separated into gas and liquid in the first container, to the mixed gas flow path via the first valve.

  According to such a configuration, since the mixed gas is taken out from the mixed gas flow path by the eductor using the pressure of the cooled medium as a driving force, the mixed gas is easily cooled by the eductor, and the concentration of the medium contained in the air Can be reduced. As a result, the amount of the medium released outside the apparatus can be reduced.

  In addition, it is preferable that the mixed air removing device further includes a liquid level gauge that detects a liquid level of the first container. According to such a configuration, since the opening and closing of the first valve is controlled so that the inside of the first container is not emptied, the air in the first container can be prevented from flowing into the flow path of the mixed gas.

  The mixed air removal apparatus of the present invention includes an air supply unit that supplies air to the mixed gas, a second valve that adjusts an amount of air supplied from the air supply unit, and a mixed gas supplied from the first container. A third valve for adjusting a flow rate; a combustor that is connected to each of the second valve and the third valve and burns the medium discharged from the first container; and the control unit includes the second valve And the third valve may be controlled to burn the medium in the combustor. According to such an aspect, when the flammable medium is used, it can be safely discharged out of the mixed air removing device of the present invention.

If the mixed air removing device is provided in the power generation device, air in the medium can be automatically removed, so that power generation efficiency can be improved.
In addition, as a medium used in the present invention, an organic low boiling point medium having a boiling point lower than that of water such as various chlorofluorocarbons such as R245fa and n-pentane is used.

  According to the present invention, the pressure threshold value obtained by adding a margin value to the saturated vapor pressure value of the medium calculated based on the temperature of the liquid phase part of the medium storage part and the pressure value of the gas phase part of the medium storage part are compared. Thus, since air contamination is detected, it is possible to automatically detect that air has entered the medium flow path of the power generation device. In addition, the amount of working medium discharged outside the apparatus can be reduced. And the fall of power generation efficiency by the air which is not condensed with a condenser mixes in a medium, and the condensation capability of a condenser falls can be prevented.

It is a figure which shows the structure of the apparatus which concerns on the Example of this invention. It is an operation | movement sequence diagram of the apparatus which concerns on the Example of this invention. It is a saturated vapor pressure diagram of n-pentane. It is a figure showing the volume ratio of n-pentane which saturates in air, using temperature as a parameter at a pressure of 101 kPa. It is a figure which shows the structure of the electric power generating apparatus using the conventional general low boiling-point medium.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of a mixed air removing apparatus according to an embodiment of the present invention. The condenser 103 in FIG. 1 corresponds to the condenser 103 in FIG. The medium storage unit 1 is connected to the upper part of the outlet side collector of the condensate 103, and a thermometer 10 that measures the temperature of the liquid phase part of the medium storage unit 1 and the pressure of the gas phase part of the medium storage unit 1. A pressure gauge 11 to be measured is installed.

  The first container 2 is connected to the medium storage unit 1 by piping through a valve 12. Furthermore, a pipe connecting the medium storage unit 1 and the eductor 41 is installed, and a valve 16 and a pressure gauge 45 are installed in this pipe.

  The medium tank 24 is connected to the pump 18. The pump 18 is connected to the eductor 41 by piping through the flow meter 6, the cooler 42, the thermometer 15, and the valve 13. The discharge port of the eductor 41 is connected to the upper part of the first container 2.

A pressure gauge 7, a liquid level gauge (high liquid level) 8, and a liquid level gauge (low liquid level) 9 are installed in the first container 2 in order from the top of the container.
The combustor 4 includes a combustion catalyst therein, and a lower portion of the combustor 4 is connected to the first container 2 via a valve 14 by piping. The air supply means 19 is connected to the combustor 4 through a valve 17 by piping. The mixed gas supplied from the first container 2 is mixed with the air supplied from the air supply means 19 and burned by the combustion catalyst of the combustor 4 to become exhaust gas. The generated exhaust gas is released to the atmosphere. The combustor 4 is provided with a heater for controlling the combustion catalyst to a predetermined temperature in order to make the combustion catalyst function. The combustor 4, the air supply unit 19, the valve 17, and the pipes connecting them are not essential, and are not necessary when the gas discharged from the valve 14 is diluted with the atmosphere without being burned.

  The control unit 5 is connected to the thermometers 10 and 15, the pressure gauges 11, 7 and 45, the liquid level gauge (high liquid level) 8, the liquid level gauge (low liquid level) 9 and the flow meter 6 through signal lines, respectively. The signal from each device is input to the control unit 5. The control unit 5 is connected to the valves 12, 13, 14, 16, and 17 by electric wiring, and controls the opening and closing of each valve.

  Next, the operation of this apparatus will be described. FIG. 2 is a diagram showing an outline of an operation sequence of the apparatus according to the first embodiment of the present invention. The control part 5 performs in order of air mixing detection process S1 and air removal process S2, and returns to air mixing detection process S1 after that. In the initial state, all valves are in a closed state.

  First, the air mixing detection step S1 will be described. The mixed air removing device is operated only when it is confirmed that the pressure of the pressure gauge 11 is equal to or lower than atmospheric pressure (or 36 ° C. or lower when the medium is n-pentane). This is because, if the pressure in the medium flow path continues to be equal to or higher than the atmospheric pressure, it is difficult for air to be mixed into the medium flow path from the outside air, and in the second half of the air removal step S2 described later, This is because the difference between the atmospheric pressure and the pressure inside the medium reservoir 1 is used as the driving force when returning the liquid medium collected in the container 2 to the medium reservoir 1. A new pump may be provided in the pipe between the first container 2 and the valve 12 so as to operate without this pressure difference.

First, the control unit 5 determines whether or not the pressure value (PIa) of the pressure gauge 11 installed in the gas phase part of the medium storage unit 1 is less than 101 kPa. When the pressure value (PIa) is 101 kPa or more, the process returns to the upstream of this determination condition and continues this determination. When the pressure value (PIa) is less than 101 kPa, the signal of the pressure gauge 11 installed in the gas phase part of the medium storage unit 1 and the signal of the thermometer 10 installed in the liquid phase part of the medium storage unit 1 are acquired. Then, a pressure threshold value obtained by adding a margin value to the saturated vapor pressure value of the medium calculated based on the temperature of the thermometer is calculated. And when the pressure value (PIa) of the pressure gauge 11 is below a pressure threshold value, it returns to the beginning of air mixing detection process S1. If the pressure value (PIa) of the pressure gauge 11 is higher than the pressure threshold value, it is determined that air has entered the medium, and the process proceeds to the next step. The margin value is a fixed value or a proportional value obtained by multiplying the saturated vapor pressure value of the medium calculated based on the temperature of the thermometer by a coefficient. Specifically, for example, in the case of n pentane, the saturated vapor pressure value (Pst) at the temperature (T1) is calculated using the following formula 1. A graph is shown in FIG. If the medium to be used is different, the equation for obtaining the saturated vapor pressure value (Pst) is appropriately changed according to the characteristics of the medium.
Pst = 0.0003 (T1) ³ +0.0159 (T1) ² +1.1844 (T1) +24.316 (Formula 1)
The margin value is determined through several tests in consideration of the number and condition of joints. For example, in the case of a fixed value, it is about 10% at 1 atmosphere. In the case of a proportional value, the coefficient is set to about 0.1.

  Next, air removal process S2 is demonstrated. The main purpose of this step is to transfer the mixed gas in the gas phase part from the medium storage part 1 to the first container 2 by the eductor 41. At this time, the mixed gas is cooled by cooling the drive medium of the eductor, and the medium concentration in the mixed gas is reduced.

  Specifically, the cooler 42 is operated after the valves 12, 13, 16, and 14 of the mixed air removing apparatus shown in FIG. After a predetermined time has elapsed, the valves 13 and 14 are opened, and the pump 18 is operated. Then, the medium cooled by the cooler 42 is transferred to the first container 2 via the stool 13 and the eductor 41.

  Thereafter, a part of the vaporized medium is discharged from the first container 2 through the valve 14 to the outside. At this time, the valve 17 is also opened. At this time, the combustor 4, the air supply unit 19, the valve 17, and piping connecting them are not essential components. For example, when the gas discharged from the valve 14 is diluted in the atmosphere without burning, the valve 14 may be opened to release the mixed gas to the atmosphere as it is. When the mixed gas is burned and released to the atmosphere, it is assumed that complete combustion cannot be achieved only with oxygen contained in the mixed gas. For example, in the case of n-pentane, when the mixing ratio with air exceeds the combustion range of n-pentane (1.5% to 7.8%), it is necessary to supply oxygen. In order to adjust the air amount within this range, air is supplied through the valve 17. The air is preferably supplied from a compressed air supply facility, and for example, instrument air for operating instrumentation equipment of the apparatus may be used. Specifically, the following procedure is used. The combustor 4 includes a ceramic honeycomb filter in which platinum fine particles are supported as a combustion catalyst. In a state where the inside of the combustor 4 is heated by the heater 4a so as to be 200 to 350 ° C., the valve 17 and the valve 14 are opened, and the mixed gas and air are supplied to the combustor 4 to burn the medium.

From here, two branch sequences operating in parallel are executed.
The first branch sequence is a step of sucking the mixed gas in the medium storage unit 1 by the eductor and transferring it to the first container 2 together with the cooled medium, and the second branch sequence is stored in the first container 2. In this step, the medium is returned to the medium storage unit 1.

  More specifically, in the first branch sequence, it is determined whether or not the pressure value (PIb) of the pressure gauge 45 is less than half the pressure value (PIa) of the pressure gauge 11. This determination is merely checking the degree of vacuum of the eductor. Here, a half value of the pressure value (PIa) of the pressure gauge 11 is temporarily used, but can be arbitrarily set arbitrarily. . When the pressure value (PIb) of the pressure gauge 45 is equal to or more than half the pressure value (PIa) of the pressure gauge 11, the determination returns to the upstream of this determination condition and the determination is continued. When the pressure value (PIb) of the pressure gauge 45 is less than half the pressure value (PIa) of the pressure gauge 11, the valve 16 is opened. Then, the mixed gas in the medium storage unit 1 is sucked by the eductor and transferred to the first container 2 together with the cooled medium.

Next, it is determined whether the pressure value (PIb) of the pressure gauge 45 is less than the determination threshold value (F3 × Pst). Pst in this determination formula is the saturated vapor pressure of the medium at the temperature (TI2) measured by the thermometer 15. F3 is a coefficient, and 1.1 is used initially. If this device frequently stops at this value, the efficiency of the power generator will continue to decline, so check for leaks at the joints.
This determination is provided in order to detect the limit of the air removal capability of the mixed air removal apparatus of the present invention. When the pressure value (PIb) of the pressure gauge 45 is equal to or greater than the determination threshold value (F3 × Pst), an error signal is transmitted and the apparatus is stopped. When the pressure value (PIb) of the pressure gauge 45 is less than the determination threshold value (F3 × Pst), the valve 16 is closed after the predetermined time has elapsed, the pump 18 and the cooler 42 are stopped, and the valve 13 is closed. And it returns to the beginning of air mixing detection process S1.

  On the other hand, in the second branch sequence, it is determined whether the valve 13 is open. If the valve 13 is closed, it means that the first branch sequence has ended. Is stopped, and the process returns to the beginning of the air mixing detection step S1. When the valve 13 is open, it is determined whether or not the liquid level in the first container 2 is higher than the position (LI1) of the liquid level gauge 8. When the liquid level in the 1st container 2 is below the position (LI1) of the liquid level indicator 8, it returns to the part which determines whether the above-mentioned valve 13 is open. When the liquid level in the first container 2 is higher than the position of the liquid level gauge 8 (LI1), the valve 12 is opened. When the valve 12 is opened, the liquid medium collected in the first container 2 returns to the medium storage unit 1. This is because there is a difference between the atmospheric pressure and the pressure inside the medium reservoir 1, so that the medium can be transferred without using a pump. Note that the medium may be actively transferred using a pump.

  Next, it is determined whether the valve 13 is open as described above. When the valve 13 is closed, it means that the first branch sequence has been completed, so the second branch sequence is stopped and the process returns to the beginning of the aeration detection step S1. When the valve 13 is open, it is determined whether or not the liquid level in the first container 2 is higher than the position (LI2) of the liquid level gauge 9. When the liquid level in the 1st container 2 is below the position (LI2) of the liquid level meter 9, it returns to the part which determines whether the valve 13 immediately before is open. When the liquid level in the first container 2 is higher than the position (LI2) of the liquid level gauge 9, the valve 12 is closed. Then, the process returns to the beginning of the second branch sequence.

Here, the reason why the amount of medium in the mixed gas can be reduced by cooling the mixed gas of air and medium will be described. The amount Fst of n-pentane saturated with air can be expressed by the following equation 2.
Fst = Fa × (Pst / (Pc−Pst)) (Equation 2)
Fst: Standard state quantity of n-pentane saturated in air at temperature t (Nm ³ )
Fa: Standard state quantity of air (Nm ³ )
Pst: saturated vapor pressure of n-pentane at temperature t (kPa)
Pc: Operating pressure (kPa)
FIG. 4 shows the result of calculating the volume ratio of n-pentane saturated in the air from Equation 2 using the temperature as a parameter at 101 kPa. The volume ratio here is a value representing how many times the volume of n-pentane saturated with respect to the air 1 is that of air. As can be seen from FIG. 4, the lower the temperature, the less pentane is saturated in the air.

1: Medium storage part 2: First container 4: Combustor (combustion catalyst filling)
5: Control unit 6: Flow meter 7: Pressure gauge of the first container 8: Liquid level gauge of the first container (high liquid level)
9: Level gauge of the first container (low liquid level)
10, 15: Thermometer 11, 45: Pressure gauge 12, 13, 14, 16, 17: Valve 18: Pump 19: Air supply unit 24: Medium tank 41: Eductor 42: Cooler S1: Air contamination detection step S2: Air removal process 100: evaporator 101: turbine 102: generator 103: condenser 104: circulation pump 105: preheater

Claims (4)

In the mixed air removal apparatus that removes air from a mixed gas of a medium having a lower boiling point than water and air,
A cooler for cooling the medium;
An eductor that draws the mixed gas from the flow path of the mixed gas using the cooled liquid medium as a driving medium;
A pump for supplying a liquid medium to the eductor;
The first container provided with a pipe connected to the discharge part of the eductor and communicating with the atmosphere;
A first valve provided in a pipe connecting the lower part of the first container and the flow path of the mixed gas;
A pressure gauge for measuring a pressure in a gas phase portion of the flow path of the mixed gas;
A thermometer for measuring the temperature of the mixed gas flow path;
When a pressure threshold value is calculated by adding the saturation vapor pressure value of the medium and a margin value calculated based on the temperature of the thermometer and the pressure value of the pressure gauge, and the pressure value of the pressure gauge is greater than the pressure threshold value In addition, it is detected that air is mixed in the medium, the cooler and the pump are operated, the eductor takes out the mixed gas from the flow path of the mixed gas, and transfers it to the first container, A mixed air removal apparatus comprising: a control unit that performs control to return the liquid medium gas-liquid separated in the first container to the flow path of the mixed gas through the first valve. The mixed air removing apparatus according to claim 1, further comprising a liquid level gauge that detects a liquid level of the first container. The mixed air removing device according to claim 1 or 2,
An air supply unit for supplying air to the mixed gas;
A second valve for adjusting the amount of air supplied from the air supply unit;
A third valve for adjusting the flow rate of the mixed gas supplied from the first container;
A combustor connected to the second valve and the third valve, respectively, for combusting the medium discharged from the first container;
The said control part controls the said 2nd valve and the said 3rd valve, and burns the said medium with the said combustor, The mixed air removal apparatus characterized by the above-mentioned. A power generation device comprising the mixed air removing device according to any one of claims 1 to 3.

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