JP2012127231A - Rankine cycle system and power generation system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Rankine cycle system for dispensing with an oil pump.SOLUTION: This Rankine cycle system 1 includes: a circulating flow passage 7 for interposing a screw expander 2 for converting expansion force of a heating medium into torque by supplying the heating medium and lubricating oil, a condenser 3 for cooling and liquefying the heating medium delivered from the screw expander 2, a circulating pump 4 for pressurizing the heating medium liquefied in the condenser 3, a separating tank 5 for storing the heating medium discharged from the circulating pump 4 in a pressurized state and separating the lubricating oil included in the heating medium by a specific gravity difference, and an evaporator 6 for resupplying the heating medium to the screw expander 2 by evaporating by heating the heating medium of separating the lubricating oil by the separating tank 5; and an oil feeding flow passage 8 for resupplying the lubricating oil separated from the heating medium by the separating tank 5 to the screw expander 2.

Description

  The present invention relates to a Rankine cycle system and a power generation system using the Rankine cycle system.

  For example, as described in Patent Document 1, a pressurized liquid-phase heat medium is heated by heat exchange with a heat source in an evaporator (heater), and the expander is heated by the expansion force of the heated heat medium. A binary power generation system using a Rankine cycle that drives and rotates the generator, cools and liquefies the heat medium discharged from the expander, re-pressurizes the heat medium liquefied by the pump, and re-supplies it to the evaporator is known It is.

  Although it is also common to use a screw expander that uses lubricating oil for lubrication and sealing as an expander, conventionally, as described in Patent Document 1, the screw expander is exhausted. Lubricating oil was separated from the heat medium using a gas-liquid separator, and the separated lubricating oil was resupplied to the screw expander by an oil pump.

  In the case of a compressor that is mechanically similar to a screw expander, it can be re-supplied by the pressure of the gas discharged from the lubricant separated from the discharged gas, but in the case of a screw expander, the supply air pressure This is because it is higher than the exhaust pressure, and it is necessary to repressurize with a dedicated oil pump.

  Moreover, in patent document 1, the waste oil port for discharging | emitting lubricating oil is provided in the rotor chamber of the screw expander, and lubricating oil is collect | recovered. In this case, it is necessary to apply a certain amount of back pressure so that not only the lubricating oil but also the heat medium does not flow out into the recovery flow path. However, if the back pressure in the recovery flow path is too high, the lubricating oil will flow backward, increasing the pressure in the space where the waste oil port opens, causing a partial reversal of the pressure gradient in the expansion process, and rotating the screw rotor. The driving force in the opposite direction is prevented. For this reason, if the pressure of the lubricating oil recovery passageway cannot be strictly controlled, there arises a problem that the efficiency of the power generation system is lowered.

  In the Rankine cycle, if a gas-liquid separator is installed between the evaporator and the screw expander, lubricating oil having a pressure equal to the heat medium supplied to the screw expander can be obtained. May not be provided. However, in that case, since the lubricating oil also passes through the evaporator, there arises a problem that the efficiency of heat exchange in the evaporator is lowered, so that a system using the above-described oil pump is generally used.

JP 60-56104 A

  In view of the above problems, an object of the present invention is to provide a Rankine cycle system and a Rankine cycle power generation system that do not require an oil pump.

  In order to solve the above problems, a Rankine cycle system according to the present invention is supplied with a heat medium and a lubricating oil, and is discharged from the screw expander that converts the expansion force of the heat medium into a rotational force, and the screw expander. A condenser that cools and liquefies the heat medium, a circulation pump that pressurizes the heat medium liquefied in the condenser, and stores the heat medium discharged from the circulation pump in a pressurized state, and is included in the heat medium. A separation tank that separates the lubricating oil by specific gravity difference, and an evaporator that heats and evaporates the heat medium from which the lubricating oil has been separated by the separation tank and then re-feeds the screw expander. And an oil supply passage for re-supplying the lubricating oil separated from the heat medium by the separation tank to the screw expander.

  According to this configuration, since the separation tank separates the heat medium and the lubricating oil by specific gravity, the configuration is simple. Further, since the lubricating oil separated in the separation tank also has the same pressure as the heat medium supplied to the screw expander, it can be supplied to the screw expander without requiring a dedicated pump.

  In the Rankine cycle system of the present invention, the oil supply passage may include a heat exchanger that heats the lubricating oil.

  According to this configuration, in the screw expander, the lubricating oil does not take the heat of the heat medium and does not reduce the expansion force of the heat medium, and hence the rotational energy of the screw expander.

  In the Rankine cycle system of the present invention, the oil supply passage may supply the entire amount of the lubricating oil to a supply-side bearing of the screw expander.

  According to this configuration, since the lubricating oil having the same pressure as the supplied heat medium is supplied to the bearing on the air supply side, loss due to the pressure difference does not occur, and the lubricating oil that lubricated the bearing can be used together with the heat medium in the rotor. Since it is also supplied to the bearing on the exhaust side through the chamber, it is not necessary to supply lubricating oil to each part of the screw expander individually.

  In the Rankine cycle system of the present invention, the screw expander may discharge the entire amount of the lubricating oil supplied to the bearing together with the heating medium.

  According to this configuration, since the lubricating oil is not discharged halfway, the pressure gradient in the expansion stroke is not reversed, and the efficiency is high.

  A power generation system according to the present invention includes any one of the Rankine cycle systems described above, and the generator is driven by the screw expander.

  According to this configuration, power can be efficiently generated by a simple system using a general oil-lubricated screw expander with a relatively low-temperature heat source such as factory exhaust heat.

  In the power generation system of the present invention, the casing of the screw expander and the casing of the generator are integrated, and the heat medium exhausted from the screw expander passes through the internal space of the generator. May flow into the road.

  According to this configuration, the coil winding of the generator is cooled by the heat medium whose temperature has decreased by driving the screw expander by expanding, and the efficiency of the generator can be prevented from decreasing.

It is a Rankine cycle power generation system of a 1st embodiment of the present invention. It is a Rankine cycle power generation system of a 2nd embodiment of the present invention. It is a Rankine cycle power generation system of a 3rd embodiment of the present invention.

  Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 shows a configuration of a Rankine cycle power generation system 1 according to the first embodiment of the present invention. The Rankine cycle power generation system 1 is a system for recovering electric power by using, for example, factory exhaust heat such as low-pressure steam that has been conventionally discarded as a heat source, recovering the heat, and generating electric energy.

  The Rankine cycle power generation system 1 includes a screw expander 2, a condenser 3, a circulation pump 4, a separation tank 5, and an evaporator 6, and a circulation channel 7 enclosing a heat medium (for example, R245fa) and a separation It has the oil supply flow path 8 which connects the upper part of the tank 5 to the site | part which requires oil supply of the screw expander 2. As shown in FIG. A generator 10 is connected to the output shaft 9 of the screw expander 2.

  The screw expander 2 accommodates a pair of male and female screw rotors in a rotor chamber formed in a casing, and expands a heat medium in an expansion space formed by dividing the rotor chamber by a screw rotor, whereby the screw rotor. Rotate. Further, the screw expander 2 is configured to perform lubrication and sealing between the screw rotors and between the screw rotor and the casing by the supplied lubricating oil. Further, the screw rotor bearing is also prevented from being worn by the supply of lubricating oil. Therefore, the heat medium exhausted from the screw expander contains lubricating oil.

  The condenser 3 is a heat exchanger that cools and liquefies the heat medium with a very inexpensive cold heat source such as cooling water produced in a cooling tower. The circulation pump 4 repressurizes the heat medium liquefied in the condenser 3 up to the supply pressure to the screw expander 2.

The pressurized heat medium is introduced into the separation tank 5 and stays in the separation tank for a certain time. In the separation tank 5, the liquid-phase heat medium is stored at a very low flow rate, so that the contained lubricating oil droplets rise due to the specific gravity difference. For example, the specific gravity of the heat medium (R245fa) is 1300 kg / m ³ , whereas the specific gravity of the lubricating oil is 900 kg / m ³ .

  In this way, the liquid-phase heat medium from which the lubricating oil is separated in the separation tank 5 is heated by heat exchange with the heat source in the evaporator 6, and is supplied to the screw expander 2 as saturated steam.

  Further, the lubricating oil separated in the separation tank 5 is supplied again to the screw expander 2 via the oil supply passage 8. An orifice, a throttle valve, or the like may be provided in the oil supply passage 8 to adjust the flow rate of the lubricating oil supplied to the screw expander 2. In addition, when supplying oil to a plurality of parts of the screw expander 2, an orifice, a throttle valve, or the like may be provided in the branch flow path of the oil supply flow path 8 so that the required amount of lubricating oil can be supplied to each part.

  In the present embodiment, the evaporator 6 heats only the pure heat medium after separating the lubricating oil. Therefore, the evaporator 6 is designed to be optimized for heating the heat medium, thereby maximizing heat recovery. It can be made possible.

  Further, the separation tank 5 does not require a complicated structure like a gas-liquid separator and may be a simple container, so it is inexpensive and does not require maintenance.

  Further, since the separation tank 5 maintains the pressure after the heat medium and the separated lubricating oil are pressurized by the circulation pump 4, the pressure of the lubricating oil supplied from the oil supply passage 8 to the screw expander 2 is It is equal to the pressure of the heat medium supplied to the screw expander 2 via the evaporator 6. For this reason, the lubricating oil separated in the separation tank 5 can be introduced into the screw expander 2 without further pressurization.

  Then, in FIG. 2, the structure of the Rankine cycle power generation system 1a which is 2nd Embodiment of this invention is shown. In addition, about this embodiment, the same code | symbol is attached | subjected to the same component as 1st Embodiment, and the overlapping description is abbreviate | omitted. In the Rankine cycle power generation system 1a of this embodiment, the oil supply passage 8 is provided with a heat exchanger 11 for heating the lubricating oil by the same heat source that heats the heat medium in the evaporator 6.

  As a result, the temperature of the lubricating oil is increased, so that the lubricating oil cools the heat medium inside the screw expander 2 and the expansion force is not reduced, so that the energy conversion efficiency (power generation efficiency) can be increased.

  Further, FIG. 3 shows a configuration of a Rankine cycle power generation system 21 which is the third embodiment of the invention. The Rankine cycle power generation system 21 of this embodiment includes a screw expander 22, a generator 23, a condenser 24, a circulation pump 25, a separation tank 26, and an evaporator 27, and encloses a heat medium. And the oil supply passage 29 for re-supplying the lubricating oil separated in the separation tank 26 to the screw expander 22.

  The screw expander 22 accommodates a screw rotor 32 in a rotor chamber 31 formed in the expander casing 30, and a bearing in which a rotation shaft 33 of the screw rotor 32 is accommodated in bearing chambers 34 and 35 formed in the expander casing 30. 36, 37. The heat medium is supplied from the circulation flow path 28 to the rotor chamber 31 through the air supply flow path 38, and the heat medium that rotationally drives the screw rotor 32 by expanding in the rotor chamber 31 is exhausted from the exhaust flow path 39.

  The generator 23 includes a rotor 42 and a stator 43 accommodated in an internal space 41 of a generator casing 40 that is integrally connected to the expander casing 30. The rotor 42 is provided on the rotating shaft 33 of the screw rotor 32 extending to the internal space 41, and generates electric power in the stator 43 by rotating together with the screw rotor 32. The internal space 41 of the generator 23 communicates with the bearing chamber 35 and the exhaust passage 39 on the exhaust side of the screw expander 22. As a result, the heat medium exhausted from the screw expander 22 to the internal space 41 of the generator 23 flows out from the exhaust port 44 provided in the generator casing 40 to the circulation passage 28.

  The oil supply passage 29 is connected only to the supply-side bearing chamber 34 of the screw expander 22 and supplies the entire amount of lubricating oil separated by the separation tank 26 to the supply-side bearing 36. Yes. The lubricating oil supplied to the supply-side bearing chamber 34 passes through the clearance between the rotary shaft 33 and the expander casing 30 and the clearance between the supply-side end surface of the screw rotor 32 and the expander casing 30. It flows into 32 tooth spaces (a space defined by the inner wall of the expander casing 30 and the teeth of the screw rotor 32).

  When this tooth groove reaches the exhaust side by the rotation of the screw rotor 32, most of the lubricating oil is exhausted into the internal space 41 of the generator 23 through the exhaust passage 39 together with the heat medium, and flows out to the circulation passage 28. However, part of the lubricating oil in the tooth grooves of the screw rotor 32 is part of the heat medium, the gap between the end surface on the exhaust side of the screw rotor 32 and the expander casing 30, and the rotary shaft 33 and the expander casing 30. Through the gap to the exhaust-side bearing chamber 35. The lubricating oil that has flowed into the bearing chamber 35 lubricates the exhaust-side bearing 37 and flows out together with the heat medium into the circulation passage 28 through the internal space 41 of the generator 23.

  In the present embodiment, since the rotor 42 and the stator 43 of the generator 23 are cooled by the heat medium whose pressure and temperature are reduced by expanding in the rotor chamber 31 of the screw expander 22, the power generation efficiency of the generator 23 is increased. Can be prevented.

  Further, as in the present embodiment, the entire amount of the lubricating oil is supplied to the bearing chamber 34 on the supply side, and the entire amount of the supplied lubricating oil is discharged to the circulation flow path 28 together with the heat medium, so that the expansion stroke of the screw expander is increased. By not supplying and discharging the lubricating oil in the middle, it is possible to prevent the pressure gradient of the heat medium from being reversed inside the screw expander, so that the heat energy can be efficiently converted into rotational energy, and thus power generation. Efficiency can be improved.

  The present invention can be widely applied not only to a power generation system but also to a system that converts thermal energy into rotational energy by a Rankine cycle, and can be used, for example, in a Rankine cycle system that drives a compressor by a screw expander.

1, 1a, 21 ... Rankine cycle power generation system 2, 22 ... Screw expander 3, 24 ... Condenser 4, 25 ... Circulation pump 5, 26 ... Separation tank 6, 27 ... Evaporator 7, 28 ... Circulation flow path 8, DESCRIPTION OF SYMBOLS 29 ... Oil supply flow path 10, 23 ... Generator 11 ... Heat exchanger 30 ... Expander casing 31 ... Rotor chamber 32 ... Screw rotor 33 ... Rotating shaft 34, 35 ... Bearing chamber 36, 37 ... Bearing 38 ... Supply air flow path 39 ... exhaust flow path 40 ... generator casing 41 ... internal space 42 ... rotor 43 ... stator 44 ... exhaust port

Claims (6)

A screw expander that is supplied with a heat medium and lubricating oil and converts the expansion force of the heat medium into a rotational force;
A condenser that cools and liquefies the heat medium discharged from the screw expander;
A circulation pump for pressurizing the heat medium liquefied in the condenser;
A separation tank that stores the heat medium discharged by the circulation pump in a pressurized state and separates the lubricating oil contained in the heat medium by a specific gravity difference;
A circulation flow path provided with an evaporator that heats and evaporates the heat medium from which the lubricating oil has been separated by the separation tank and then re-feeds the screw expander;
A Rankine cycle system comprising an oil supply passage for re-supplying the lubricating oil separated from the heat medium by the separation tank to the screw expander.   The Rankine cycle system according to claim 1, wherein the oil supply passage includes a heat exchanger that heats the lubricating oil.   The Rankine cycle system according to claim 1 or 2, wherein the oil supply passage supplies the entire amount of the lubricating oil to a bearing on an air supply side of the screw expander.   The Rankine cycle system according to claim 3, wherein the screw expander discharges the entire amount of the lubricating oil supplied to the bearing together with the heat medium.   5. A power generation system comprising the Rankine cycle system according to claim 1, wherein a power generator is driven by the screw expander.   A casing of the screw expander and a casing of the generator are integrated, and the heat medium exhausted from the screw expander flows out into the circulation channel through an internal space of the generator. The power generation system according to claim 5.

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