JPH0457843B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an exhaust heat recovery device that generates power, for example, by using heated waste water discharged from a factory or the like.

Conventional Technology A waste heat recovery device as shown in Fig. 2 has been used to recover power by a Rankine cycle that utilizes small temperature differences using heated waste water discharged from factories, etc., for the purpose of generating electricity, for example. It is used. In the figure, 1 is an evaporator that heats and evaporates working fluid, such as fluorocarbons, using a heat source such as heated waste water, 2 is a turbine that is rotated by the fluorocarbon vapor evaporated in the evaporator 1, and 3 is the output of the turbine 2. It is a generator connected to the shaft. 4 is a condenser for condensing evaporated freon discharged from the turbine 2, and cooling water is supplied to the condenser 4. A pump 5 circulates Freon between the evaporator 1, the turbine 2, and the condenser 4.

In the above waste heat recovery device, in order to generate electricity from a heat source such as heated waste water, cool water is supplied to the condenser 4 at the same time as heated waste water is supplied to the evaporator 1, and in this state, the pump 5 to circulate the Freon. Then, the liquid Freon discharged from the pump 5 and sent to the evaporator 1 is heated by hot water in the evaporator 1, becomes Freon vapor, and is sent to the turbine 2. The fluorocarbon steam rotates the turbine 2, and the generator 3 connected to the output shaft of the turbine 2 rotates, thereby generating electricity. Further, the fluorocarbon vapor discharged from the turbine 2 is sent to the condenser 4, where it is cooled by the cooling water supplied to the condenser 4. After being condensed in the condenser 4, it returns to the pump 5 again, and the above-mentioned The action is repeated.

Problems to be Solved by the Invention However, when power is recovered from a relatively low-temperature heat source such as industrial heated wastewater as described above, it is not possible to increase the temperature difference, so it is difficult to sufficiently heat the working fluid, such as fluorocarbon vapor. It was recognized that there was a problem in that the power could not be recovered sufficiently.

In addition, to compensate for the above-mentioned drawbacks, the working fluid evaporated in the evaporator 1, such as fluorocarbon vapor, is guided to a second heater (not shown), and the fluorocarbon vapor is superheated in the second heater. , turbine 2
A method has been proposed to increase the amount of power recovered by supplying As the heat source for the second heater, the heat source supplied to the evaporator 1 may be used, or another heat source may be used.

However, when attempting to increase the amount of power recovery using the above method, the following problems arise. That is, since the fluorocarbon vapor supplied to the second heater is a gas, it is inevitable that the second heater for superheating the fluorocarbon vapor will be larger. Therefore, by interposing the second heater between the evaporator 1 and the turbine 2 shown in FIG. 2, the entire device becomes extremely large, making it difficult to secure installation space.

In view of the technical problems observed in the conventional waste heat recovery devices as described above, the present invention aims to recover working fluids such as fluorocarbons using a relatively low temperature heat source such as heated wastewater discharged from factories, etc. When recovering power by using steam as the working fluid, the amount of power recovered can be increased without increasing the size of the exhaust heat recovery device by superheating the steam without using a large heater. Its main purpose is to provide a new waste heat recovery device that can increase the amount of heat recovered.

Means for Solving the Problems In view of the above object, the present invention provides a positive displacement expansion machine 1.
2, an evaporator 10 for evaporating the working fluid supplied to the positive displacement expander 12 using waste heat, and a lubricating oil supplied to the positive displacement expander 12 at a temperature higher than the vapor temperature of the working fluid. A small temperature difference heat exchanger 11 for heating, an oil separator 19 for separating working steam and lubricating oil discharged from the positive displacement expander 12, and an oil separator 19 for separating the oil discharged from the positive displacement expander 12. It consists of a condenser 20 for condensing the vapor separated in the vessel 19, and first and second pumps 21 and 22 for circulating the working fluid and lubricating oil, which are supplied into the positive displacement expander 12. Evaporator 10
The working steam sent out from the small temperature difference heat exchanger 11
The lubricating oil heated to high temperature in the positive displacement expander 12
The gist is an exhaust heat recovery device that superheats working steam by bringing it into direct contact with the outside, thereby increasing the amount of power recovered by the exhaust heat recovery device.

Embodiment FIG. 1 is a block diagram illustrating the configuration of an exhaust heat recovery apparatus according to the present invention. In the figure, 10 is an evaporator for heating and evaporating a working fluid, such as fluorocarbon, using a heat source such as hot water, and 11 is an evaporator for evaporating lubricating oil to be supplied to the screw type expander 12, which is the positive displacement expander. This is a plate type heat exchanger which is a small temperature difference heat exchanger for heating to a higher temperature than the temperature of fluorocarbon vapor. The same heat source may be used, or other heat sources may be used. Reference numeral 12 denotes a screw type expander to which fluorocarbon vapor evaporated in the evaporator 10 and lubricating oil heated to a higher temperature than the fluorocarbon vapor in the plate heat exchanger 11 are supplied.
In this embodiment, a screw type expander is used as the positive displacement expander 12, but any other known positive displacement expander such as a reciprocating expander can be used. In addition to the above-mentioned fluorocarbons, fluids having a low boiling point such as butane, ammonia, or alcohol can be used as the working fluid. However, in the following description, in order to facilitate understanding, embodiments using a screw type expander, a plate type heat exchanger, and fluorocarbons will be explained. As shown in FIGS. 3 to 5, the screw type expander 12 includes a case body 15 having a suction hole 13 and a discharge hole 14, and a screw-shaped male rotor 16 rotatably supported within the case body 15. It is composed of a female rotor 17. The case body 1 is arranged so that the female rotor 16 and the male rotor 17 have their axes parallel to each other, and rotate while meshing with each other.
It is located within 5. Furthermore, the capacity of the tooth-shaped space a formed between the male rotor 16 and the female rotor 17 increases as they rotate and the meshing point moves from the suction side to the discharge side. The tooth profile shapes of both rotors 16 and 17 are set so that they increase. Further, the suction hole 13 and the discharge hole 14 of the case body 15 are arranged so as to open at the end faces of the male rotor 16 and the female rotor 17, and the outer peripheries of the male rotor 16 and the female rotor 17 are connected to the case body 1.
It is surrounded by the inner wall surface of 5. Therefore, the fluorocarbon vapor that has flowed into the suction hole 13 of the screw type expander 12 flows into the tooth space a formed between the male rotor 16 and the female rotor 17.
After the male rotor 16 and the female rotor 17 are rotated and expanded within the tooth space a, they are discharged from the discharge hole 14, and power is recovered during this time.
Furthermore, the fluorocarbon vapor discharged from the evaporator 10 comes into direct contact with lubricating oil heated to a higher temperature than the fluorocarbon vapor discharged from the plate heat exchanger 11 in the piping, as shown in FIG. The fluorocarbon vapor is superheated and supplied into the case body 15 from the suction hole 13. The lubricating oil lubricates the female and male rotors 16 and 17 and seals each part.
On the other hand, a small temperature difference heat exchanger such as the plate heat exchanger 11 raises the temperature of lubricating oil close to the inlet temperature of a heat source such as hot water, thereby exhausting heat without using any other heat source. A reheat cycle can be formed in the recovery device. Further, 18 is a generator connected to the output shaft of the screw type expander 12, and 19 is a generator connected to the screw type expander 1.
20 is an oil separator for separating fluorocarbon vapor discharged from the discharge hole 14 and lubricating oil; 20 is a condenser for condensing the fluorocarbon vapor separated by the oil separator 19; As shown in the figure, cooling water is supplied from outside the system. 21 is a first pump for lubricating Freon between the evaporator 10, screw type expander 12, oil separator 19 and condenser 20; 22 is for lubricating oil between the plate heat exchanger 11, screw type expander 12 and This is a second pump for circulating oil between the oil separators 19. Further, 23 is a third pump for supplying heated waste water to the evaporator 10 and the plate heat exchanger 11.

In order to generate electricity using the waste heat recovery device according to the present invention, a heat source such as heated waste water is supplied to the evaporator 10 and the plate heat exchanger 11, and at the same time, cooling water is supplied to the condenser 20. . In this state, the first to third pumps 21, 22, and 23 are driven to circulate Freon and lubricating oil. Then, the liquid Freon discharged from the first pump 21 and sent to the evaporator 10 is heated by hot water in the evaporator 10, becomes Freon vapor, and enters the suction hole 13 of the screw type expander 12. flows into. In addition, the lubricating oil discharged from the second pump 22 and sent to the plate heat exchanger 11 is also heated to a higher temperature than the above-mentioned fluorocarbon vapor by hot water in the plate heat exchanger 11, and becomes a fluorocarbon. The steam and the lubricating oil heated to a higher temperature than the freon steam come into direct contact in the piping, and after being superheated, the mesh between the male rotor 16 and the female rotor 17 of the screw type expander 12 causes a gap between the two. It flows together with lubricating oil into the tooth profile space a created in the tooth shape space a. After the fluorocarbon vapor expands in the tooth space a and rotates the male rotor 16 and the female rotor 17, the fluorocarbon vapor and lubricating oil are discharged from the discharge hole 14 of the screw type expander 12 into the oil separator 19. flows into. When the male rotor 16 and female rotor 17 of the screw type expander 12 rotate as described above, the generator 18 connected to the output shaft of the screw type expander 12 also rotates, so that power is generated. Furthermore, the fluorocarbon vapor and lubricating oil that have flowed into the oil separator 19 are separated within the oil separator 19,
The freon vapor is sent to the condenser 20.
After being cooled by cooling water and turned into a fluorocarbon liquid, it is sent to the evaporator 10 again through the first pump 21. Furthermore, the lubricating oil discharged from the oil separator 19 is sent to the plate heat exchanger 11 again through the second pump 22. By continuously repeating the above operation, power is recovered from a heat source such as heated waste water.

FIG. 6 is a graph comparing the case where the fluorocarbon vapor supplied to the screw type expander is superheated with lubricating oil and the case where it is not superheated when power is recovered by the above-mentioned exhaust heat recovery device. In the figure, h1 and h1' are the screw-type expander inlet (evaporator outlet), h2 and h2' are the screw-type expander outlet (condenser inlet),
h3 is the condenser outlet (first pump inlet), h4
indicates the first pump outlet (evaporator inlet). The thermodynamic cycle when Freon vapor is not superheated by lubricating oil is h1 → h2 → h3 → h
4, and the power recovery amount is (h1 - h2). or,
The thermodynamic cycle when fluorocarbon vapor is superheated by lubricating oil is h1′→h2′→h3→h
It becomes 4. Also, the power recovery amount is (h1'-h2'), and (h1'-h2')/(h1-h2)>1.0. Here, under the conditions that the temperature of the freon vapor at the inlet of the screw type expander 12 is 62°C and the outlet is 30°C,
If the fluorocarbon vapor is superheated by 20°C using lubricating oil, (h1'-h2')/(h1-h2)≒1.1, which increases the power recovery amount by about 10%.

According to experiments conducted by the present inventors, for example, when factory heated wastewater having an inflow temperature of approximately 75° C. is supplied into the evaporator 10 and the plate heat exchanger 11 to generate fluorocarbon vapor and heat lubricating oil. The lubricating oil whose inflow temperature into the plate heat exchanger was about 50°C is heated to about 72°C, while the factory wastewater at about 75°C which entered the evaporator 10 is sent out from the condenser 20. The liquid fluorocarbon is converted into steam at about 62°C, and the fluorocarbon vapor is brought into direct contact with lubricating oil in the pipe to superheat the fluorocarbon vapor and then supplied into the screw type expander 12. Incidentally, the temperature of the heated waste water discharged from the plate heat exchanger 11 was about 53°C.

In this way, in the screw type expander 12, the temperature of the freon is lowered from about 62°C to about 50°C, and the temperature of the lubricating oil is lowered from about 72°C to about 50°C. Therefore, it is possible to generate a large temperature drop compared to conventional devices, and the amount of power recovered by the generator 18 is significantly increased.

Effects of the Invention As described above, after the working fluid, for example, Freon, is evaporated by the evaporator, it is supplied to the screw type expander consisting of a pair of rotors, and
If the lubricating oil supplied to the screw-type expander is heated to a higher temperature than the fluorocarbon vapor and then brought into direct contact with the fluorocarbon vapor to superheat the fluorocarbon vapor, compared to conventional equipment that directly supplies fluorocarbon vapor to the turbine, The amount of power recovered can be increased. In addition, if the vapor of working fluid such as Freon is superheated using a small temperature difference heat exchanger such as a plate heat exchanger and a positive displacement expander, the lubricating oil can be heated using a small heat exchanger. Since this can be done using an exchanger, the amount of power recovered can be increased without increasing the size of the exhaust heat recovery device.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an exhaust heat recovery device according to the present invention, FIG. 2 is a block diagram showing the configuration of a conventional exhaust heat recovery device, and FIGS. 3 to 5 are:
FIG. 6, which is a schematic diagram showing the structure of a screw type expander as an example of a positive displacement expander, is a temperature (pressure)-enthalby diagram showing the thermodynamic cycle of the exhaust heat recovery device according to the present invention. 10... Evaporator, 11... Small temperature difference heat exchanger (e.g. plate heat exchanger), 12... Positive displacement expander (e.g. screw-type expander), 1
3... Suction hole, 14... Discharge hole, 15... Case body, 16... Male rotor, 17... Female rotor, 2
0... Condenser, 21... First pump, 22...
Second pump, 23...Third pump.

Claims (1)

[Claims] 1 A positive displacement expander, an evaporator for evaporating the working fluid supplied to the positive displacement expander using waste heat, and a lubricating oil supplied to the positive displacement expander at a temperature higher than the vapor temperature of the working fluid. an oil separator to separate the working steam discharged from the positive displacement expander from the lubricating oil, and an oil separator to separate the working steam discharged from the positive displacement expander from the lubricating oil. a condenser for condensing the vapor produced by the pump, and first and second pumps for circulating the working fluid and lubricating oil, and the working fluid is supplied from the evaporator to the positive displacement expander. An exhaust heat recovery device characterized by superheating working steam by bringing steam and lubricating oil heated to a high temperature in a small temperature difference heat exchanger into direct contact outside a positive displacement expander.