JPH0535242B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an exhaust heat recovery device, and more particularly, to a waste heat recovery device having a closed loop structure. The present invention relates to an exhaust heat recovery device that removes gas and prevents a decrease in exhaust heat recovery efficiency due to a decrease in heat transfer performance and an increase in condensation pressure.

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

In the above-mentioned 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 a 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 passes through the pump 5 again to the evaporator. 1, and the above operation is repeated.

Problems to be Solved by the Invention In the exhaust heat recovery device having the closed loop structure, a working fluid such as fluorocarbon is sealed prior to the start of operation, but a non-condensable gas such as air are often mixed in. If such non-condensable gas is involved in the system, it not only reduces the heat transfer performance of the condenser but also causes problems such as a reduction in exhaust heat recovery efficiency due to an increase in condensing pressure.

The main object of the present invention is to provide an exhaust heat recovery device with improved non-condensable gas removal function that can solve the above-mentioned problems found in conventional exhaust heat recovery devices. It is something.

Means for Solving the Problems In view of the above object, the present invention provides a positive displacement expansion machine 1.
2, an evaporator 11 for evaporating the working fluid supplied to the positive displacement expander 12 using waste heat, and a first evaporator 11 for condensing the vapor of the working fluid discharged from the positive displacement expander 12. In the exhaust heat recovery device constituted by a condenser 14 and pumps 20 and 22 for circulating the working fluid, the first
Low-temperature cooling water is supplied to the condenser 14 in order to separate the liquefied working fluid and the non-condensable gas entrained in the working fluid, so that the inside of the condenser 14 is kept at the highest pressure in the closed loop system. The lower part of the second condenser 17 and the working fluid storage tank 18 are connected, and the upper part of the working fluid storage tank 18 and the inside 19 of the second condenser 17 are connected to each other for discharging noncondensable gas. 10, and an exhaust valve 2 for discharging noncondensable gas is connected to the upper part of the second condenser 17.
The gist is an exhaust heat recovery device equipped with 7.

Embodiment FIG. 1 is a block diagram illustrating the overall structure of the apparatus of the present invention.

In the figure, 11 is an evaporator for heating and evaporating a working fluid, such as fluorocarbon, using a heat source such as industrial heated wastewater, and 13 is a positive displacement expander for supplying lubricating oil to a screw type expander 12. 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 the fluorocarbon vapor evaporated in the evaporator. 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 11 and lubricating oil heated to a higher temperature than the fluorocarbon vapor in the plate heat exchanger 13 are supplied. In this embodiment, a screw type expander is used as the positive displacement expander 12, but in the present invention, any other known positive displacement expander such as a reciprocating type expander can be used. be able to. 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 Freon will be explained. The screw type expander is
It is composed of a screw-shaped male rotor and a female rotor that are rotatably supported in a case body having suction holes and discharge holes (not shown), and both axes of the male rotor and female rotor are parallel to each other. , and are arranged within the case body so that the two are engaged and rotated. In addition, the capacity of the tooth-shaped space formed between the male and female rotors increases as they rotate and the meshing point moves from the suction side to the discharge side. The tooth profile shapes of both rotors are set. Further, the suction hole and the discharge hole of the case body are arranged so as to open at the end faces of the male rotor and the female rotor, and the outer peripheries of the male rotor and the female rotor are surrounded by the inner wall surface of the case body. . Therefore, the fluorocarbon vapor that has flowed into the suction hole of the screw type expander 12 is
It flows into the toothed space formed between the female rotor and the male rotor, rotates the female rotor and the male rotor, expands within the toothed space, and then is discharged from the discharge hole, during which time it rotates the generator 15. Perform power recovery. Further, at an arbitrary position of the suction hole, there is a nozzle (Fig. (not shown) is provided. The lubricating oil not only lubricates the male and female rotors and seals each part, but also superheats the fluorocarbon vapor by coming into direct contact with the fluorocarbon vapor supplied into the case body from the suction hole. on the other hand,
A small temperature difference heat exchanger such as the plate heat exchanger 13 raises the temperature of lubricating oil close to the inlet temperature of a heat source such as industrial heated wastewater, thereby discharging heat without using any other heat source. A reheat cycle can be formed in the recovery device. Further, 15 is a generator connected to the output shaft of the screw type expander 12, 16 is an oil separator for separating lubricating oil from freon vapor discharged from the discharge hole of the screw type expander 12, and 14 is This is the first condenser for condensing the freon vapor separated by the oil separator 16, and cooling water is supplied to the inside from outside the system as shown in the figure. 20 is a first pump for supplying the liquid Freon condensed in the first condenser 14 to the storage tank 18, and 21 is a pump for supplying lubricating oil to the plate heat exchanger 13, the screw expander 12 and the oil separator. This is a second pump for circulating between the vessels 16. In addition, 23 is an evaporator 11 and a plate heat exchanger 13 for industrial heated waste water.
and a third pump for supplying 24
is a fourth pump for supplying cooling water to the first condenser 14 and the second condenser 17 described later; For example, a pump 22 for supplying liquefied fluorocarbon is incorporated.

In the device of the present invention, the first condenser 14
A second condenser 17 for separating condensed and liquefied fluorocarbons from noncondensable gas, such as air, entrained in the fluorocarbon vapor, and a storage tank 18 for condensed and liquefied fluorocarbons are connected to the fluorocarbons. With,
The upper part of the storage tank and the non-condensable gas outlet 19 of the second condenser 17 are connected by a communication pipe 10 for discharging non-condensable gas. On the other hand, a second conduit 25 is provided between the bottom of the second condenser 17 and the storage tank 18 for refluxing the fluorocarbons condensed in liquid form. A first pipe line 26 is connected from between the first pump 20 and the second condenser 17 for refluxing the fluorocarbon vapor that has not been sufficiently condensed and entrains the non-condensable gas. It's branching out.

The operating capacity of the device of the present invention will be explained below. To generate electricity using the exhaust heat recovery device according to the present invention,
The pump 23 is started to supply a heat source such as heated waste water to the evaporator 11 and the plate heat exchanger 13, and at the same time the pump 24 is started to supply the heat source to the first condenser 14 and the second condenser 17. Supply cooling water. In this state, pumps 20, 21 and 2
2 to circulate fluorocarbons and lubricating oil into the exhaust heat recovery device. Then, the liquid Freon discharged from the pump 22 and sent to the evaporator 11 is heated in the evaporator 11 by heat exchange with the heated waste water, becomes a Freon vapor, and flows into the screw type expander 12. do. On the other hand, the lubricating oil discharged from the pump 21 and sent to the plate heat exchanger 13 is also heated to a higher temperature than the above-mentioned fluorocarbon vapor by the heated wastewater supplied into the plate heat exchanger. In this state, the liquid is supplied to a nozzle installed in a suction hole (not shown) of the screw type expander 12, and is injected into the suction hole from the tip of the nozzle. In this way, the fluorocarbon vapor supplied to the suction hole of the screw type expander 12 comes into direct contact with the lubricating oil heated to a higher temperature than the fluorocarbon vapor and is superheated. It flows together with lubricating oil into the tooth space created between the male rotor and the male rotor. After the fluorocarbon vapor expands within the tooth space and rotates the male and female rotors, the fluorocarbon vapor and lubricating oil are transferred from the discharge hole of the screw type expander 12 to the oil separator 16.
flow inward. When the male rotor, female rotor, and female rotor of the screw type expander 12 rotate, the generator 15 connected to the output shaft of the screw type expander 12 also rotates, so that power generation is performed. Furthermore, the fluorocarbon vapor and lubricating oil that have entered the oil separator 16 are separated within the oil separator, and the fluorocarbon vapor is sent to the first condenser 14 where it is cooled by cooling water and becomes a fluorocarbon liquid. After that, pump 20
The water is sent to the storage tank 18 through the pump 22, and then refluxed to the evaporator 11 through the pump 22. Furthermore, the lubricating oil discharged from the oil separator 16 is sent to the plate heat exchanger 13 again through the pump 21. By continuously repeating the above operations, power is recovered from a heat source such as industrial heated waste water.

By the way, if a non-condensable gas, such as air, is mixed with the working fluid, such as fluorocarbons, in the closed loop that constitutes the above-mentioned waste heat recovery device, not only will the heat transfer performance of the condenser deteriorate, but the condensing pressure will also decrease. Problems such as a decrease in waste heat recovery efficiency occur due to the increase in
As a means to avoid such a problem, the present invention provides, in the first condenser 14, the fluorocarbons liquefied by the first condenser and the non-condensable gas, such as air, entrained in the liquefied fluorocarbons. a second condenser 17 for separating and discharging the non-condensable gas out of the closed loop;
It is connected to a fluorocarbon storage tank 18 connected to the second condenser. The operation procedure of the noncondensable gas discharge device having such a structure will be explained below.

The working fluid, such as fluorocarbon vapor, sent to the first condenser 14 is cooled by cooling water and discharged from the first condenser in a condensed state, and is then discharged from the first condenser at the branch point 2.
At step 8, the liquefied fluorocarbon containing no non-condensable gas is separated into fluorocarbon vapor which is not sufficiently condensed and entrains non-condensable gas such as air bubbles. The former is fed directly into the fluorocarbon storage tank 18 through the pump 20, while the latter, that is, fluorocarbon vapor entrained with non-condensable gases, is sent through the first reflux pipe 26 to the second condenser. The fluorocarbon vapor is liquefied and sent into the fluorocarbon storage tank 18 through the second pipe line 25. In addition,
The noncondensable gas and uncondensed fluorocarbon vapor sent into the fluorocarbon storage tank 18 float in the fluorocarbon liquid, reach the upper space of the fluorocarbon storage tank 18, and pass through the communication pipe 10 to the second condenser 17. The non-condensable gas flows into the second condenser 17 from the outlet 19 . Since the second condenser is equipped with an introduction mechanism for low-temperature cooling water supplied via the pump 24, the uncondensed freon vapor that has flowed into the second condenser 17 is
The fluorocarbons are condensed due to heat exchange with the cooling water and accumulated in the condenser, and then flow into the second pipe line 25 for recirculating the fluorocarbons.
It flows back into the Freon storage tank 18 through. Further, the non-condensable gas separated from the fluorocarbon vapor is discharged from the closed loop through an exhaust valve 27 provided at the top of the second condenser 17.

In this way, when a working fluid is sealed in the exhaust heat recovery device to form a closed-loop reheat cycle circuit,
The noncondensable gas entrained in the working fluid is automatically discharged out of the closed loop when the exhaust heat recovery device starts operating.

Effects of the Invention As can be understood from the above explanation, in the present invention, a second condenser is provided to separate the noncondensable gas from the working fluid, and low-temperature cooling water is supplied to the second condenser. By supplying and creating the lowest pressure part of the closed loop system in the condenser, the working fluid can be condensed and the concentration of non-condensable gas can be increased and discharged from the system. Therefore, good power recovery efficiency can be obtained under conditions where the condensing pressure is relatively low.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating the overall structure of the apparatus of the present invention, and FIG. 2 is an explanatory diagram of a conventional exhaust heat recovery apparatus. 12... Positive displacement expander, 11... Evaporator, 14
...First condenser, 20, 22... Pump, 17
... Second condenser, 18 ... Working fluid storage tank, 1
9...Noncondensable gas outlet, 10...Communication pipe.

Claims (1)

[Claims] 1. A positive displacement expander, an evaporator for evaporating working fluid supplied to the positive displacement expander using waste heat, and vapor of the working fluid discharged from the positive displacement expander. In the exhaust heat recovery device configured by a first condenser for condensing the working fluid and a pump for circulating the working fluid, the first condenser is provided with the liquefied working fluid and the working fluid. A second condenser and working fluid that supply low-temperature cooling water into the vessel to separate noncondensable gases entrained in the fluid and make the inside of the vessel the lowest pressure part in the closed loop system. The upper part of the working fluid storage tank and the inside of the second condenser are connected by a communication pipe for discharging noncondensable gas, and the upper part of the second condenser is connected to the upper part of the second condenser. An exhaust heat recovery device characterized by being equipped with an exhaust valve for discharging condensable gas.