JP2004181373A - Air dryer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air dryer provided with an oil-water separation apparatus and which is space-saving type, low cost, and convenient for use and is capable of saving the energy by recycling waste heat in the apparatus as a heat source for vacuum distillation. <P>SOLUTION: This air dryer is a refrigeration type air dryer for cooling compressed air in a heat exchanger and compressing water contained in the compressed air as drain to be separated from the compressed air, and the air dryer is provided with an oil-water separation apparatus which is capable of evaporating and separating water in the drain from oil components by heating the drain from the heat exchanger in a reduced pressure in a vacuum distillation tank connected to the heat exchanger and recovering the evaporated water as purified water. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a refrigeration air dryer that cools compressed air obtained by a refueling compressor, condenses moisture in the compressed air as drain, and separates the compressed air from the compressed air.
[0002]
[Prior art]
Oil-supplied compressors are widely used in the industrial field where compressed air is used as a utility, because of the lower price of equipment compared to non-oil-supplied compressors, better compression efficiency and lower running cost.
[0003]
Air dryers are used to remove drain from compressed air and protect pneumatic equipment. Techniques for removing the drain from compressed air include cooling the compressed air with a refrigerator to condense moisture, collecting water with an adsorbent such as activated alumina, and passing compressed air through a hollow fiber membrane to remove moisture from the membrane. Although there is a system that allows only water molecules to permeate, a refrigeration system is superior in terms of maintainability and cost of the device. The compressed air obtained by the oil supply type compressor contains an oil component because lubricating oil is used for lubrication, sealing, cooling, and the like in the compression process. Refrigerated air dryers are generally used because activated alumina and hollow fiber membranes dislike the attachment of oil.
[0004]
By the way, the "Water Pollution Control Law" is a wastewater standard in Japan, and the maximum concentration of oil contained in wastewater is determined to be 5 mg / l, but it is generated from compressed air obtained by a refueling compressor. The oil concentration of the drain is generally about 5 mg / l or more and about 500 mg / l, and the drain cannot be drained in an untreated state.
[0005]
Conventionally, drain condensed by a refrigeration dryer is stored in a waste liquid tank, and the wastewater is drained after regularly requesting an industrial waste disposal company to dispose of it or installing a drain purification device to perform purification treatment. . As a drain purifying device, a method of adsorbing oil using a filter, an oil flotation method using microbubbles, a vacuum distillation method (see the following document), and the like are generally used.
[0006]
[Patent Document]
JP 2000-18162 A
[Problems to be solved by the invention]
According to the above prior art, the function of condensing the drain from the compressed air and the function of purifying the condensed drain correspond to respective individual devices. For this reason, supporting the drain condensation function and the purification processing function by independent systems has many inconvenient factors, such as an increase in installation space, an increase in equipment costs, and a connection operation between systems.
[0008]
The waste heat of the refrigeration air dryer is released to the atmosphere from the condenser without being reused. The amount of the waste heat reaches about three to four times the amount of the output of the refrigerator of the air dryer, and it is desirable to recover the energy from the viewpoint of energy saving and global environment.
[0009]
Therefore, an object of the present invention is to provide an air dryer with an oil-water separator that is space-saving, cost-saving, and easy to use.
[0010]
Another object of the present invention is to provide an air dryer with an oil-water separator that can save energy by reusing waste heat in the device as a heat source for vacuum distillation.
[0011]
[Means for Solving the Problems]
A feature of the present invention that solves the above problems is that a refrigeration air dryer that cools compressed air in a heat exchanger, condenses moisture in the compressed air as a drain, and separates the compressed air from the heat, In a vacuum distillation tank connected to the heat exchanger, the drain contained in the heat exchanger was heated and placed under reduced pressure to evaporate the water in the drain to separate it from oil, and the evaporated water was recovered as treated water. That is, an oil-water separator was provided.
[0012]
Further, the features of the present invention that solves the above-mentioned problems are characterized in that the heat recovered by the heat exchanger and the latent heat of the refrigerant that cools the compressed air and the ejector in the vacuum distillation process are used as the heat source for drain heating in the vacuum distillation tank. At least one of the heat transferred to the circulating water and the latent heat of the refrigerant for controlling the temperature of the circulating water of the ejector is used as a heat source in oil-water separation of the drain.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, one embodiment of the present invention shown in FIG. 1 will be described.
In FIG. 1, 1 is a heat exchanger of a refrigeration air dryer, 1a and 1b are baffle plates and piping in the heat exchanger 1, 2 is a partition valve, 3 is a refrigerant compressor, 4 is a vacuum distillation tank, 4a, 4b is a pipe and coil for heat exchange in the vacuum distillation tank 4, 5 is a hot gas bypass valve, 6 is a capillary tube, 7 is a drain discharge valve, 9 is an ejector, 10 is a water pump, 11 is a water tank, 12 Is a refrigerant compressor, 13 is a circulating water cooler, 14 is a capillary tube, 15 is a drain pipe, 16 to 19 are refrigerant pipes of the refrigerant compressor 3, 20 is an exhaust pipe, 21 is a drain pipe, and 22 to 24. Is a circulating water pipe, 25 to 27 are refrigerant pipes of the refrigerant compressor 13, and 28 is a purified water drain pipe.
[0014]
A gate valve 2 and a capillary tube 6 are respectively provided in the middle of a drain pipe 15 and a refrigerant pipe 16 connecting the heat exchanger 1 and the vacuum distillation tank 4. The hot gas bypass valve 5 is provided in the middle of the refrigerant pipe 19 connecting the refrigerant pipes 17 and 18. An ejector 9 is provided in the middle of a circulating water pipe 22 connecting the water pump 10 and the water tank 11, and a suction port in the middle of the ejector 9 is connected to a top plate of the vacuum distillation tank 4 by an exhaust pipe 20. . A capillary tube 14 is provided in the middle of a refrigerant pipe 27 connecting the heat exchange coil 4b and the circulating water cooler 13 in the vacuum distillation tank 4.
[0015]
Next, the flow of the compressed air will be described.
From the compressed air inlet of the heat exchanger 1 of the air dryer, compressed air of about 50 ° C., which has been raised to a specified pressure of a compressor not shown, flows in. The compressed air changes its flow path with the baffle plate 1a and flows to the compressed air outlet of the heat exchanger 1 while contacting the pipe 1b. Since the surface of the pipe 1b has a low temperature, heat exchange is performed with the compressed air. The refrigerant in the pipe 1b is heated by the compressed air, and changes the state from a low-temperature liquid refrigerant to a low-temperature gas refrigerant. At this time, the compressed air is cooled from about 50 ° C. to 5 to 10 ° C. In this process, the water contained in the compressed air becomes supersaturated, so that the water condenses and drains.
[0016]
The drain generated in the heat exchanger 1 is separated from the compressed air and accumulates in the lower part of the heat exchanger 1. A vacuum distillation tank 4 communicating with the heat exchanger 1 through the gate valve 2 and the drain pipe 15 is provided as a drain container. When the drain accumulated in the heat exchanger 1 reaches a certain amount, the gate valve 2 is opened and the pressure difference between the heat exchanger 1 and the vacuum distillation tank 4 (decompression of the vacuum distillation tank 4 will be described later). It flows to the 4 side. When there is no drain in the heat exchanger 1, the gate valve 2 closes, and the heat exchanger 1 and the vacuum distillation tank 4 become containers having independent functions.
[0017]
The vacuum distillation tank 4 is connected to the ejector 9 via a pipe 20, and the inside of the vacuum distillation tank 4 is kept in a depressurized state by the exhaust action of the ejector 9. Further, inside the vacuum distillation tank 4, a heat exchange means including a pipe 4a and a coil 4b is provided.
[0018]
The refrigerant compressor 3 sucks the low-pressure refrigerant gas that has absorbed heat from the compressed air in the heat exchanger 1 from the refrigerant pipe 17, raises the pressure to a predetermined pressure, and discharges it to the refrigerant pipe 18. At this pressure increase, the refrigerant further has latent heat. The refrigerant pipe 18 is connected to the vacuum distillation tank 4 and has a function of a heat exchanger inside the vacuum distillation tank 4. That is, the inside of the refrigerant pipe 18 is a high-temperature, high-pressure refrigerant gas, which exchanges heat with the drain in the vacuum distillation tank 4, and the refrigerant gas changes to a high-temperature liquid state.
[0019]
Thereafter, the refrigerant liquid passes through the refrigerant pipe 16 and is throttled by the capillary tube 6, and then expands in the refrigerant pipe 16 to become a low-temperature refrigerant liquid. The low-temperature refrigerant liquid absorbs heat from the compressed air in the heat exchanger 1 to recover the heat of the compressed air, returns to the low-temperature, low-pressure refrigerant gas, and thereafter repeats this cycle. In addition, since the amount of heat transferred to the refrigerant gas changes due to the change in the capacity of the compressed air, the hot gas bypass valve 5 is opened according to the load, and the high-pressure gas in the refrigerant pipe 18 is returned to the low-pressure side of the refrigerant pipe 17 through the pipe 19. .
[0020]
Next, the vacuum system will be described.
The ejector 9, the water pump 10, the water tank 11, and the circulating water cooler 13 are connected by circulating water pipes 22 to 24. The circulating water discharged from the water pump 10 becomes a high-pressure, high-speed jet flow in the ejector 9 and sucks air from a pipe 20 of the ejector 9. The vacuum distillation tank 4 becomes a closed space by closing the gate valve 2, and the inside of the vacuum distillation tank 4 is depressurized by the suction (exhaust) action of the ejector 9.
[0021]
Next, the drain purification process will be described.
The drain of the vacuum distillation tank 4 is heated by a heat pump composed of the refrigerant compressor 3 and the refrigerant pipes 16 to 18 by receiving heat transfer from the refrigerant in the pipe 4a. Since the inside of the vacuum distillation tank 4 is depressurized by the above-mentioned vacuum system, the heated drain boils at a low temperature of 100 ° C. or less and evaporates.
[0022]
Since the oil contained in the drain has a high boiling point of 100 ° C. or more, only the water evaporates, and the oil and water separate in the vacuum distillation tank 4. The water vapor is discharged through the pipe 20 by the exhaust action of the ejector 9, mixed with the circulating water by the ejector 9, cooled by the circulating water to become treated water, flows into the water tank 11, and discharged through the pipe 28. Is done. The treated water is purified water in which steam that has already been separated from oil and water and contains almost no oil is cooled by circulating water.
[0023]
Next, the temperature control of the circulating water will be described.
The steam sucked into the ejector 9 is cooled by the circulating water and collected in the water tank 11 as treated water. Since the circulating water is supplied with heat from the steam, the temperature of the circulating water rises with time and becomes hot water of 50 to 60C. The exhaust performance of the ejector 9 decreases as the water temperature rises up to a water temperature of about 20 ° C. Therefore, it is necessary to maintain the temperature of the circulating water at 20 ° C. or lower in order to maintain the exhaust capacity.
[0024]
Therefore, as a circulating water cooling system, a refrigerant cycle including the refrigerant compressor 12, the circulating water cooler 13, the heat exchange coil 4b, and the refrigerant pipes 25 to 27 is provided. The circulating water is sucked from the water tank 11 by the water pump 10 and is cooled by exchanging heat with a circulating water cooler 13 provided in the middle of the circulating water pipes 23 and 24. On the other hand, the refrigerant gas which has become high temperature in the circulating water cooler 13 is made high temperature and high pressure in the refrigerant compressor 12, and is introduced into the heat exchange coil 4b. After heat exchange with the drain inside the vacuum distillation tank 4 to become a liquid refrigerant, it expands in the capillary tube 14 through the pipe 27 and returns to the circulating water cooler 13 as a low-temperature liquid refrigerant to cool the circulating water and exchange heat. .
[0025]
Thereafter, this cycle is repeated.In this cycle, the temperature of the circulating water is controlled, and at the same time, the latent heat given to the refrigerant when the refrigerant is pressurized in the refrigerant compressor 12 is used for heating the drain, and the temperature is raised for that purpose. The heat of the circulating water is recovered as a heat source for drain heating of the vacuum distillation tank 4.
[0026]
The oil separated in the vacuum distillation tank 4 is periodically opened to open the drain discharge valve 7 and is collected in a waste liquid tank (not shown).
[0027]
In this embodiment, the heat exchanger of the air dryer and the oil-water separator are integrated, and an air dryer with an oil-water separator that is space-saving, cost-saving, and easy to use can be obtained.
[0028]
In addition, the heat recovered by the heat exchanger of the air dryer, the heat transferred to the circulating water of the ejector in the vacuum distillation process, the latent heat of the refrigerant for cooling the compressed air, and the latent heat of the refrigerant for controlling the temperature of the circulating water of the ejector are drained. It is possible to obtain an air dryer equipped with a drain purifying device which is used as a heat source in oil-water separation and has a high energy saving effect.
[0029]
If the drain heating in the vacuum distillation tank 4 can be sufficiently performed, either the pipe 4a or the coil 4b is deleted, and the heat recovered by the heat exchanger of the air dryer and the latent heat of the refrigerant for cooling the compressed air, In addition, at least one of the heat transferred to the circulating water of the ejector and the latent heat of the refrigerant for controlling the temperature of the circulating water of the ejector in the vacuum distillation process may be used as a heat source in oil-water separation of the drain.
[0030]
The air dryer can be used not only for compressed air obtained by an oil-supply type compressor but also for drying compressed air containing oil and moisture in the middle of a piping system.
[0031]
【The invention's effect】
As described above, according to the present invention, it is possible to obtain an air dryer with an oil-water separator that is space-saving, cost-saving, and easy to use.
[0032]
Further, according to the present invention, it is possible to obtain an air dryer with an oil-water separator that can save energy by reusing waste heat in the device as a heat source for vacuum distillation.
[Brief description of the drawings]
FIG. 1 is a system diagram of an air dryer with an oil-water separator according to one embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Heat exchanger 1a ... Baffle plate 1b ... Piping 2 ... Partition valve 3 ... Refrigerant compressor 4 ... Vacuum distillation tank 4a ... Piping 4b ... Coil 6 ... Capillary tube 9 ... Ejector 10 ... Water pump 11 ... Water tank 12 ... Refrigerant Compressor 13: Cooler for circulating water 14: Capillary tube

Claims (2)

In a refrigeration air dryer that cools compressed air in a heat exchanger and condenses moisture in the compressed air as a drain to separate it from compressed air,
The drain contained in the heat exchanger is heated and placed under reduced pressure in a vacuum distillation tank connected to the heat exchanger to evaporate the water in the drain to separate it from oil, and recover the evaporated water as purified water. An air dryer provided with an oil-water separation device adapted to perform the operation. In the air dryer according to claim 1, as a heat source for drain heating in the vacuum distillation tank, the heat recovered by the heat exchanger and the latent heat of the refrigerant that cools the compressed air, and the circulating water of the ejector in the vacuum distillation process. An air dryer using at least one of a transferred heat and a latent heat of a refrigerant for controlling the temperature of circulating water of an ejector.

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