JP5960045B2 - Binary power generation system - Google Patents

Description

  The present invention relates to a binary power generation system that converts heat energy into low power by using a low-temperature heat source such as geothermal / exhaust heat, and converts the heat energy into power, and in particular, improves the safety by using water as the medium. This is related to a binary power generation system that has achieved cost reduction.

In recent years, the use of energy from low-temperature heat sources such as natural energy, factory exhaust heat, engine cooling water, etc. is getting more and more attention due to the demand for departure from the nuclear power plant and further the request for CO ₂ reduction.

The binary power generation method is characterized by being able to generate power with low-temperature hot water (fluid) that could not be used with other types of power generation, and mainly using medium-low temperature fluid.
The binary power generation method uses a single fluid as a medium and is called the Rankine cycle. ORC vaporizes an organic medium having a boiling point lower than that of water due to the heat of steam or gas, and uses that steam to drive the turbine. It is.

  For example, as shown in FIG. 6, the binary power generation system 100 includes a heat exchanger 11 that takes in a heat source from a medium-low temperature resource and exchanges heat with a low-boiling organic medium, and heat from the low-boiling organic medium using the heat exchanger 11. The steam turbine 13 that operates by taking in, the generator 17 connected to the steam turbine 13, the condenser 14 that condenses the steam used in the steam turbine 13 and returns it to water, and the condenser 14. A pump 18 for sending water to the heat exchanger 11 together with the low boiling point organic medium is provided.

A temperature-entropy (TS) diagram of such a binary power generation system 100 can be shown as in FIG. The circled numbers in FIG. 6 indicate the position of each point in the state diagram shown in FIG. In addition, the encircled numerals 1-9 in FIG. 6 are described as 1-9 in the specification.
According to the TS diagram, in the state 1 to the state 2, the low boiling point organic medium enters the pump 18 as a saturated liquid in the state 1. Adiabatic compression is performed from the pump 18 to the inlet of the heat exchanger 11, and the temperature of the low-boiling organic medium slightly increases.
In the state 2 to the state 3, the low boiling point organic medium is heated at a constant pressure in the heat exchanger 11 by heat exchange with a heat source from a medium / low temperature resource. As a result, the low boiling point organic medium boils and vapor is extracted.
In the state 3 to the state 4, the steam is adiabatically expanded, and in the state 4 to the state 5, the steam is adiabatically expanded in the steam turbine 13, and the temperature is lowered to be brought to the condenser 14.
Then, in the state 1 from the state 5, the steam whose temperature has decreased is condensed by the blower 14 a in the condenser 14 and is sent to the pump 18 as a saturated liquid.
As described above, it can be understood that the binary power generation system 100 can generate power with hot water (fluid) in a low temperature region, and can mainly use fluids in a low / medium / low temperature region.

  By the way, conventionally, as disclosed in, for example, Patent Document 1, some binary power generators use a rotary separation type two-phase flow turbine as means for separating steam contained in hot water and hot water. The hot water is boosted and supplied directly to the heat exchanger, and is brought into direct contact with the low boiling point medium to exchange heat to generate steam of the low boiling point medium, which drives the turbine. Power generation.

  Moreover, in patent document 2, while providing a bottom pump in the bottom of a geothermal well, installing the two-phase flow turbine which has a rotation separator on the ground surface, and rotating and separating the geothermal water conveyed to the ground by the bottom pump Introduced into the rotary separator of a two-phase flow turbine and rotated the rotary separator, separated into steam and hot water, and driven the bottom pump using the power of the rotary separator Is described.

Japanese Examined Patent Publication No. 1-47461 Japanese Examined Patent Publication No. 2-43915

However, the thing of the said patent document 1 uses only a two-phase flow turbine, and has what has a property without a hydrophilic property, such as isobutane and butane, as a low boiling-point medium.
Moreover, although the thing of patent document 2 uses the two-phase flow turbine, it is not a thing of the combination of the two-phase flow after heat exchange and a steam turbine, and it is not assumed using water as a medium.
When performing binary power generation typified by ORC, the turbine inlet temperature that can be raised by the heat exchanger becomes low (the heat drop is small), so the cycle efficiency is low. In addition, since a low-boiling organic medium is used, handling is difficult, and safety and other costs are high, and environmental risks are high. When water is used as a medium, the efficiency is poor.
The present invention has been proposed from the above background, and it is an object of the present invention to provide a binary power generation system that improves cycle efficiency by using water as a medium instead of an organic medium. .

In order to solve the above-mentioned problem, in the invention according to claim 1, a low-temperature heat source of 50 ° to 300 ° C., a heat exchanger that exchanges heat with the medium, and the medium that is heat-exchanged by the heat exchanger are supplied. is, gas and two-phase flow turbine for obtaining power, a generator driven by the two-phase flow turbine, a separator for gas-liquid separating the medium flowing out from the two-phase flow turbine, from the separator, said medium by supplying steam obtained by liquid separation, and a steam turbine for obtaining power, a generator to the steam turbine Thus driven, the condenser for condensing the steam from the steam turbine, further comprising a Features.

Here, the low temperature heat source of 50 ° C. to 300 ° C. includes, for example, pentane (boiling point: 36 ° C.), isobutane (C ₄ H ₁₀ , boiling point −11.7 ° C.), ammonia (boiling point) as a low boiling point medium. This is because the low boiling point medium can be sufficiently boiled by heat exchange even when a mixed fluid of -33 ° C.) and water or an alternative chlorofluorocarbon (boiling point: 34 ° C.) is used.
In this way, the gas-liquid two-phase flow medium is separated into steam and hot water by the separator, and the generator is driven by the steam turbine. It turns out that the heat source can be used for power generation.

  Thereby, since the heat exchange outlet may be saturated water instead of saturated steam, a large heat drop is obtained, and the efficiency of the entire cycle is improved. This is advantageous in terms of safety, environmental friendliness, and ease of handling, and the cost and safety of the whole plant are improved.

In the invention according to claim 2, medium is characterized by a Mizudea Turkey.

  Thereby, although a heat exchange exit may be saturated water and the turbine efficiency in a two-phase flow turbine falls, efficiency improves as a whole cycle. Moreover, since the medium is water, cost reduction and safety of the entire plant are improved.

  In the invention according to claim 3, the medium is a low-boiling organic medium.

By using a low-boiling organic medium as the medium, the system efficiency is reduced, but the output of the two-phase turbine is 15% of the total, and an equivalent output can be obtained as compared with ORC using pentane.
Since heat exchange is possible in a liquid-liquid state in the heat exchanger, the working fluid specific volume is smaller than that of the conventional ORC gas-liquid heat exchange, and the cost can be reduced because the heat exchanger can be downsized. .

In the invention according to claim 4, medium is characterized by the alternative flon der Turkey.

  Thereby, the safety of the plant is ensured. Although the turbine efficiency in the two-phase flow turbine is reduced, the efficiency is improved as a whole cycle.

  The invention according to claim 5 is characterized in that the two-phase flow turbine is an impulse turbine.

  As a result, when using a low-boiling organic medium, the nozzle outlet can be brought out with a degree of thirst of 100% depending on conditions, and improvement in turbine efficiency can be expected.

  Further, the invention according to claim 6 is characterized in that the two-phase flow turbine is a positive displacement turbine.

  As a result, the screw has robustness with respect to the degree of thirst, and an improvement in reliability can be expected.

  According to the present invention, the efficiency of the entire system is improved, and safety is improved by using water as a medium, and the equipment cost can be suppressed.

1 is an overall system explanatory diagram showing a first embodiment of a binary power generation system according to the present invention. It is a TS diagram of the binary power generation system shown in FIG. 2 is a graph showing the relationship between the heat source temperature and cycle efficiency when pentane is used as the low boiling point organic medium in the binary power generation system shown in FIG. 1. It is an overall system diagram showing a reference example of binaries power generation system. It is a perspective explanatory view showing an example of a steam turbine used in a first embodiment of a binary power generation system according to the present invention. It is a schematic system diagram showing an example of a conventional binary power generation system. FIG. 7 is a TS diagram of the binary power generation system shown in FIG. 6.

  Embodiments of a binary power generation system according to the present invention will be described below and described with reference to the accompanying drawings.

(First embodiment)
FIG. 1 shows a binary power generation system 10 according to the first embodiment.
The binary power generation system 10 includes a heat exchanger 11 that exchanges heat between a low-temperature heat source of 50 ° C. to 300 ° C. and a medium.
The binary power generation system 10 includes a separator 12 that gas-liquid separates the gas-liquid two-phase flow medium of the medium from the heat exchanger 11 into steam and hot water.
Further, the binary power generation system 10 includes a steam turbine 13 that supplies steam after gas-liquid separation from the separator 12 to acquire power, and a condenser 14 that condenses the steam from the steam turbine 13. Yes.
And between the heat exchanger 11 and the separator 12, the two-phase flow turbine 15 which supplies the gas-liquid two-phase flow medium of the medium after heat exchange, and acquires motive power is provided.

In this binary power generation system 10, water is used as a medium.
The heat source for geothermal heat is approximately 220 ° C., and water as a medium in the heat exchanger 11 is taken out as saturated water at around 190 ° C. from the outlet of the heat exchanger 11 by heat exchange and supplied to a two-phase turbine 15 described later. It has come to be.

The two-phase turbine 15 can be a known axial turbine although not shown.
When the saturated water of about 190 ° C. flows, the generator 16 connected to the rotating shaft is rotated to take out electric power.

  Next, the sealed separator 12 connected to the outlet side of the two-phase flow turbine 15 separates steam and hot water from the two-phase flow of gas and hot water containing saturated water from the two-phase flow turbine 15. And a sealed housing 12b. That is, steam is separated from the top of the housing 12b, and hot water is taken out from the bottom of the housing and separated.

  Furthermore, the steam turbine 13 on the downstream side of the separator 12 is rotated by the steam separated by the separator 12, and the generator 17 connected to the rotating shaft of the steam turbine 13 is rotated to take out electric power.

  The condenser 14 is an air-cooled type, and the steam that has passed through the steam turbine 13 is condensed by the blower 14a to be sent as a saturated liquid to the first pump 18 on the downstream side.

  The downstream side of the first pump 18 merges with the hot water separated in the separator 12 described above, and is sent to the second pump 19 for sending it to the heat exchanger 11 as a saturated liquid with increased pressure. It is a configuration.

The binary power generation system 10 according to the first embodiment is configured as described above. Next, the operation will be described based on the temperature-entropy (TS) diagram shown in FIG.
In the state 1, the water as the medium is pressurized and mixed by the first pump 18 until the condensate output from the condenser 14 becomes equal in pressure to the hot water separated from the separator 12 in the state 2 ′. (State 2), and in state 3, it is fed into the heat exchanger 11 by the second pump 19.
The condensate from the condenser 14 is pressurized by the first pump 18 to slightly increase the temperature, and the temperature rises by mixing with the hot water separated from the separator 12.
From state 4 to state 5, in the heat exchanger 11, with the heat source of about 200 ° C. in geothermal heat, the water as the medium is heated up by heat exchange and taken out as saturated water at about 190 ° C. It is fed into the two-phase flow turbine 15.

In the two-phase flow turbine 15, when the saturated water flows, the turbine shaft rotates and the generator 16 connected to the turbine shaft is rotated to extract electric power.
When passing through this two-phase flow turbine 15, the saturated water at 190 ° C. works while adiabatically expanding from state 6 to state 7, the temperature drops, and is fed into the separator 12 as saturated water at about 150 ° C. It is.

  Next, in the separator 12, the steam and the hot water are separated from the two-phase flow of the gas and the hot water from the two-phase flow turbine 15, and the steam is separated from the upper part of the sealed casing 12b. Hot water is separated from the bottom of 12b.

The steam taken out from the separator 12 is in the state 8. By rotating the turbine shaft in the steam turbine 13, the generator 17 connected to the turbine shaft is rotated and electric power can be taken out.
When passing through the steam turbine 13, in the state 8 to the state 9, the steam works again while adiabatically expanding, the temperature is lowered, and is sent to the condenser 14.

  Then, the steam is condensed in the condenser 14 by the blower 14a, and it is pressurized and mixed as saturated water by the first pump 18 until it becomes the same pressure as the hot water separated from the separator 12, and the first pump 19 is mixed. Is sent to the heat exchanger 11 again. In this way, the operation as a Rankine cycle is executed.

As described above, according to the binary power generation system 10 according to the first embodiment, since water is used as a medium, the outlet of the heat exchanger 11 is not saturated steam but saturated water. Even at about 220 ° C., a sufficiently large heat drop is obtained, and the efficiency of the entire cycle is improved (see FIG. 3).
Thus, the use of water as a medium is advantageous in terms of safety, environmental friendliness, and ease of handling, leading to cost reduction of the entire plant and improvement of safety.

The present invention can also be implemented by the binary power generation system 10 according to the second embodiment.
(Second Embodiment)
In the binary power generation system 10 according to the second embodiment, since the system configuration itself is the same as that of the first embodiment, illustration is omitted, and only differences will be described.
That is, in the binary power generation system 10 according to the second embodiment, instead of water, an organic medium such as pentane (boiling point: 36 degrees) or an alternative chlorofluorocarbon (boiling point: 34 ° C.) with a high environmental load may be used as the medium. it can. Further, as the medium, a mixed fluid of isobutane (C4H10, boiling point-11.7 ° C.), ammonia (boiling point: −33 ° C.) and water is also possible.

  According to the binary power generation system 10 according to the second embodiment as described above, since the outlet of the heat exchanger 11 is not saturated steam but saturated water, it is sufficient even if the heat source in geothermal heat is approximately 220 ° C. Although a heat drop is obtained and the turbine efficiency in the two-phase flow turbine 15 is reduced by about 20%, the efficiency of the entire cycle is improved.

(Reference example)
FIG. 4 shows a binary power generation system 10 according to a reference example .
In the reference example , a low boiling point organic medium such as pentane is used as the medium.
Unlike the systems of the first and second embodiments, the binary power generation system 10 here excludes the two-phase flow turbine 15. Since other configurations are the same as those of the system according to the first and second embodiments, description thereof will be omitted.

According to the binary power generation system 10 according to such a reference example , the system efficiency is reduced, but in the low boiling point organic medium such as pentane, the output in the two-phase flow turbine 15 of the first embodiment is about 15% of the whole. Since it is small, an equivalent output can be obtained when compared with pentane ORC.
Since heat exchange is possible in the liquid-liquid state in the heat exchanger 11, the working fluid specific volume is small and the heat exchanger becomes smaller by the gas-liquid heat exchange of the conventional ORC. Can be suppressed.

The present invention has been described with reference to the first and second embodiments.
As the two-phase flow turbine 15 used in the binary power generation system 10 according to the first embodiment, an impulse turbine can be used as shown in FIG.
In this case, the two-phase flow turbine 15 includes a turbine shaft 20, a rotor 21, and a nozzle 22. On the outer peripheral surface of the rotor 21, the moving blades 23 project at equal intervals. The nozzle 22 is arranged so that hot water is ejected toward the moving blade 23. In this case, the nozzle 22 has a shape in which the front end jet port 22a is opened in a square shape and expands toward the center side.

  The two-phase flow turbine 15 may be a positive displacement turbine (not shown) in addition to the impulse turbine.

  When the two-phase flow turbine 15 of the impulse turbine as described above is used, when a low-boiling organic medium is used as the medium, the nozzle outlet can be brought out with a degree of thirst of 100% depending on the conditions. Improvement can be expected.

  On the other hand, when a positive displacement turbine is used as the two-phase flow turbine 15 of the impulse turbine, the screw has a characteristic that the efficiency is robust with respect to the dryness, the erosion is strong, and reliability can be expected.

Here, the present invention is actually verified by comparing an example in which pentane is used as a medium and an example in which water is used as a medium.
A pentane hybrid cycle using pentane as the medium in the binary power generation system 10 shown in FIG. 1 will be described.
In the pentane hybrid cycle, the temperature of the low-temperature heat source is 200 ° C., the temperature of pentane obtained by heat exchange by the heat exchanger 11 is 189.99 ° C., the output of the generator 16 by the two-phase turbine 15 is 553 kW, steam The output of the generator 17 by the turbine 13 was 3542 KW, the total power output was 4095 KW, the power transmission output was 3350 KW, and the cycle efficiency was 13.85%.
As described above, when pentane is used as a medium, it can be understood that the steam turbine occupies most of the output. In this case, the operating conditions other than the flow rate of the steam flowing into the steam turbine are similar to those of the current ORC, and feasibility is expected.
Even if the two-phase flow turbine is eliminated and the output is somewhat reduced, an evaporator is not required, and the system can be manufactured at a low cost. Thus, the system is superior to the current ORC.

On the other hand, a water hybrid cycle using water as a medium in the binary power generation system 10 shown in FIG. 1 will be described.
In the water hybrid cycle, the output of the generator 16 by the two-phase flow turbine 15 is 1238 kW, the output of the generator 17 by the steam turbine 13 is 2206 kW, the total power output is 3443 kW, the power transmission output is 2991 kW, and the cycle efficiency Was 12.37%.
As described above, when water is used as a medium, the power distribution is about 1: 2 between the two-phase flow turbine 15 and the steam turbine 13.
The problem is whether the flow rate of steam to the steam turbine 13 is small and the efficiency of the turbine can be secured 80%.

  In the binary power generation system of the present invention, the overall efficiency of the system is improved, and the safety is improved by using water as a medium, and the facility cost can be suppressed. Therefore, the present invention can be applied to binary power generation systems of various scales and various systems.

DESCRIPTION OF SYMBOLS 10 Binary power generation system 11 Heat exchanger 12 Separator 12b housing | casing 13 Steam turbine 14 Condenser 15 Two-phase flow turbines 16 and 17 Generator 18 1st pump 19 2nd pump 20 Turbine shaft 21 Rotor 22 Nozzle 23 Moving blade

Claims (6)

A heat exchanger for exchanging heat between the low-temperature heat source and the medium;
A two-phase flow turbine that is supplied with the medium heat-exchanged by the heat exchanger and obtains power;
A generator driven by the two-phase turbine;
A separator for gas-liquid separation of the medium flowing out of the two-phase flow turbine ;
A steam turbine for obtaining power by supplying steam obtained by gas-liquid separation of the medium from the separator;
A generator driven by the steam turbine;
A condenser for condensing steam from the steam turbine;
A binary power generation system characterized by comprising: Binary power generation system of claim 1 wherein the medium is characterized in that Ru Mizudea.   The binary power generation system according to claim 1, wherein the medium is a low boiling point organic medium. Binary power generation system of claim 1 wherein the medium is characterized in that Ru der alternative flon. The binary power generation system according to claim 1 , wherein the two-phase flow turbine is an impulse turbine. The binary power generation system according to claim 1 , wherein the two-phase flow turbine is a positive displacement turbine.

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