DE1945177A1 - Method and device for drying compressed gases - Google Patents

Description

NUREM

10 278 10 279

DELTECH ENUINEERZNG INC ₁ Century Park, New Castle, Delaware, USA

Method and apparatus for drying compressed gases

The invention relates to devices for drying compressed Gases, in particular of the type in which cooling is provided, is. Hit the invention should be both with regard to such drying process and the corresponding Drying device received a Beihe von ¥ er'Deeser \ mgen will.

Compressed gases, in particular compressed air, often have a very high moisture content after compression, more precisely actually actually normally. This high Peuchtigkeitsgehalt eoleJier gases is but the various intended VerwaMungssweslreR of gases in uaterseMedlichem mass counter and for this reason it was passed in practice to "the gases to dry before DE® use, the humidity that made them © jatfernea * S ¹ Ur © iaea such

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The drying process uses, among other things, cooled air dryers. In these drying devices, the water is removed from the compressed gas in such a way that the temperature the same is lowered to a certain value below the dew point, whereby the water vapors present in the gas condense to liquid water and precipitate out of the gas. The gas obtained in this way is always at the lowest operating temperature of the drying device Saturated water vapor, however, is far below the general degree of saturation and is therefore at the higher levels Temperatures at which it is normally used, sufficiently dry.

As is known, a cooling of compressed gas in the. Way can be achieved that a heat exchange between the gas and a coolant, beapielsweiee the usual Ereon, is carried out ₉ whereby the coolant Ia is contained in a normal cooling circuit ₈ which is usually composed of a compressor, a condenser _{9 of} a Äusdelmsmgsireiitil or the like, , a receptacle and of course. composed of & © s? © evaporator cooler e @ lbs ^l t,. ■.

With a sol @ h @ a einfaei & sa Sy @ t @ ia the © rlmltdne gas is cold, which in? Iel @ a garbage does not represent a ¥ © 3? 1s® £ i and often even came to be disadvantageous * B @ JL fiea ailgotieisi Iftliehea Vonriefetuag®a with deaeis. 2 £ @ apEimiert © s Sas v @ £ w @ ii (S © t wisd _e © mssdas das aielit t Isalt ® © ia w & ä «la F © mefetlgk @ it dl @. Inclination. Has»

to condense and precipitate in the outside air on cold surfaces} is a constant occurrence in the gas pipes to a "sweating" and the condensation water then runs off these lines, whereby the operation of such Facilities are impaired and, in the course of time, corresponding signs of corrosion occur, so that such systems ultimately become unusable.

Due to the conditions described above and also with regard to the fact that the heat absorption capacity the cold gases thus obtained is itself beneficial, various systems have already been proposed with which either the efficiency of the cooling gas drying device is improved or the coldness of the dried one is improved in some other way Gas should be used before it is used for its intended purpose. A well-known suggestion went along with it to exploit this cold in such a way that the cold product gases were used to divert the incoming product gases first of all to pre-cool by means of a heat exchange. If handled carefully, this procedure can be a better one Use of the energy introduced into the drying device at the compressor is achieved and also largely the size of the compressor to be changed"

However, this method described above has several serious ones ! specialist parts. So inevitably a gas

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Gas heat exchanger used «But such exchangers are inherently very unwieldy, take up an extremely large amount of space and are also not very thermally effective, since large heat exchange surfaces are always required in order to transfer a certain amount of heat per unit of time, which results from the low heat capacity of gases and from the poor heat transfer coefficients of the gases, which are much worse than liquids, or. at the Condensation or evaporation of liquids

When using the cold product gas to precool the inflowing gas, there is also a further difficulty in that a largely unchangeable drying system is obtained with such an arrangement. Paradoxically, less stringent drying requirements lead to a loss of flexibility. Should, for example, a unit in which the gas-gas pre-cooling stage is designed such that a gas with a dew point at 1.67 ° C is obtained, but to generate a slightly more humid gas, for example a gas with a dew point at 15.56 ⁰ C are used in order to obtain a correspondingly larger volume of product gas, it turns out that the heat exchange is disappointingly low, because the comparatively warmer gas coming from the drying stage is a comparatively poorer heat transfer medium in the GaerGae - pre-cooling stage is «'

4 t

♦ f

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The disadvantages described above can be reduced by the fact that the cooled product gas that comes with the coolant has been brought to a heat exchange, not for door cooling of the inflowing gas, but rather for cooling and used to condense the compressed refrigerant before it is expanded and evaporated in the drying stage is brought.

Since the cool gas coming from the drying stage of the unit is mixed with a condensed liquid, namely the coolant, to the Heat exchange is brought about, the part of the heat exchanger intended for this can be made much smaller and simpler than the bulky and not very powerful gas-gas heat exchangers that have hitherto been used to to utilize the heat absorption ability of the cold dried gas. By using the cold dried gas for the condensation of part of the coolant-parallel to a conventional condenser of the ambient air on the cold Page used to condense the rest of the refrigerant in the circuit - can be specified in a cooling system Big an increased gas drying capacity and also an increased independence from the influence the ambient temperature can be achieved on the capacity of the system; Another advantage here is that that the system is also more versatile in that it is also possible to treat more humid product gases, so that

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a correspondingly larger volume of product gas is obtained

By departing from the previously common procedure in which the product gas is used to pre-cool the inflowing gas, but it can also have other very important advantages be achieved. So first of all the condensation of the water from the inflowing gas, which is the most essential The task of the process is to perform in a single exchanger, which means that the collection and discharge of the Condensate water necessary measures essentially combine " fold »In addition, the overall size of such a system with a given capacity and a given dew point of the product are significantly reduced.

To this end, the invention provides a method of drying of compressed gas by cooling the same using a closed circuit in which the coolant is a Compression-condensation and an expansion-evaporation stage passes through, the heat exchanging gas with the liquid coolant and thereby the gas is cooled and the water is condensed from it. Following this the coolant is then evaporated, the condensed water is separated from the gas, the evaporated coolant is collected and compressed, the cooled gas is brought to heat exchange with at least part of the compressed coolant, so that the gas is heated and its relative humidity

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reduces, and the compressed coolant condenses, the ambient air with at least part of the compressed Coolant brought to heat exchange and finally that heated and dried gas is diverted to a consumption device.

Another object of the invention is to provide a drying device for compressed gases having a first Heat exchanger in which the compressed gas to be dried and the coolant to be evaporated for heat exchange with one another are brought, and a water separation device attached in the vicinity of the first heat exchanger, in which the water condensed from the compressed gas in the first heat exchanger is collected and discharged, so that the water can no longer come into contact with the gas, while at the same time major gas losses are avoided be, as well as with a second heat exchanger, in which the relatively dry cool compressed gas and the too condensing coolant, are brought to heat exchange and with a third heat exchanger in which the ambient air and the coolant to be condensed are brought to exchange heat with one another, with corresponding Lines are provided through which the compressed gas from an inlet point through the first heat exchanger and then flows through the second heat exchanger to an outlet point, and a closed circuit is provided is, in which the refrigerant passes through a compression-condensation and an expansion-vaporization stage, whereby through

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an appropriate routing of the coolant to be evaporated fed to the first heat exchanger and the coolant to be condensed to the second and third heat exchangers * In the first heat exchanger there is preferably a substantially vertical evaporation tube with closed Ends attached and the coolant expansion device is with the evaporation tube in the area of the lower end of the same connected in such a way that the no longer pressurized liquid coolant for evaporation is passed into the tube, while a coolant discharge tube, which is inserted in the bottom area of the evaporation tube into the same is, in the evaporation pipe up to a height located just before the upper end of the evaporation pipe,

so that the flue pipe extends through the evaporation pipe and its outer surface in the area of the same normally the liquid coolant located there and is exposed to the lubricant that was released from the coolant at the low temperatures.

By placing an indicator in the gas flow the color of which changes when a certain relative humidity of the gas stream is reached during rewarming the same changed after the dehumidification, can without an indication of the effect of the drying level can also be obtained.

The invention is explained in more detail below on the basis of some exemplary embodiments with reference to the drawings »

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Show it:

Figure 1 is a somewhat simplified shown to scale View of a preferred embodiment of an inventive ! Drying device j

Pigur 2 is a flow diagram for the drying device according to Pigur 1;

Pigur 3 shows a partially schematically illustrated vertical section through another embodiment of the invention, which is particularly suitable for such drying devices with a relatively low flow rate work on compressed gas; and

Pigur 4 is a side view of part of the device according to Pigur 3.

The general mode of operation of the method according to the invention with the device according to the invention can best be explained with reference to the flow diagram of the Pigur 2. The system shown in Pigur 2 comprises a first heat exchanger or cooler 10 and a second heat exchanger or reheater 11. These two devices form the main parts of the system through which the gas to be dried is passed, it first passing through the cooler and then flows through the reheater. The part of the system intended for gas treatment also includes a water separator 20 and

a collecting container 12.

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_{A compressor U 9,} a condenser 14, a condenser fan 15, a receptacle 16 and an expansion valve 17 belong to the cooling circuit of the system self-contained cooling system is created. A suitable coolant, for example one of the commonly used freons, is located in this cooling system.

As FIG. 2 illustrates, wet compressed gas is introduced into the system through line 18, through which it is fed to cooler 10. Here it is brought into heat exchange through appropriate contact with the coolant. The cooler 10 is preferably a heat exchanger of the type consisting of a tube and a corresponding jacket, with the compressed gas in the jacket and the coolant in the tube. In the cooler 10, the wet compressed gas gives off heat to the coolant, whereby it is evaporated. Thus, the temperature of the wet gas falls below its saup point to a predetermined or desired Semperatux, which is considerably below the dew point of the inflowing gas. The water vapor contained in the gas condenses and precipitates out of the gas as liquid water. Since the compressed gas in the heat exchanger 10 is in contact with liquid condensed water, ieO € ae d © .s everywhere in the heat exchanger at the various points of the

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194517

Heat exchanger given temperatures essentially saturates, but in the Masee in which the gas flows through of the heat exchanger cools down further, it contains an ever smaller absolute amount of water (weight per unit volume). The cooled gas, which now has a lower moisture content, then enters via a line 19 the reheater 11. At the same time, the condensed water is also passed through the line 19 but from this into the separator and passed into the collecting container 12. The water separator 20 and the collecting container 12 can be any Acting devices of known design that only have to meet the requirement that they have water in one under Accumulate pressurized system and can either intermittently or continuously remove it from the system, without any significant gas losses occurring within the facilities and the system.

The reheater 11 is also preferably one consisting essentially of a tube and a casing Existing heat exchanger and the compressed gas is expediently through the jacket and the coolant passed through the pipe. In this way, the cooled compressed gas becomes in heat-exchanging contact with the brought compressed hot coolant. There is that Coolant heat from the compressed gas, whereby this is heated and brought to a temperature, which is preferably Is above the dew point of the same. The compressed

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Gas therefore has a low outlet temperature absolute water content and a low relative humidity. The reheated dry compressed gas leaves the Plant through line 28 and is fed from there for further consumption.

The flow path and the use of the coolant in the process and the device according to FIG. 2 can be illustrated most clearly in the way that its flow path from the receiving container 16 through the system and again traced back to the receptacle 16. The pressurized liquid coolant leaves the receptacle 16 via a line 22, through which it is the relief valve 17 is fed. The expansion valve can be any known type of valve, for example a Act with valve with capillary tube or the like. The coolant is relaxed through the valve and reaches the Tube of the cooler 10. In the cooler 10, the coolant is heated by the compressed gas in the jacket and, made to evaporate. It leaves the cooler 10 as a gas through a line 24 through which it is fed to the compressor 13 will. In this compressor 13, it can expediently be a built-in motor compressor in a hermetically sealed housing. The compressor increases the The pressure of the cooling gas and the correspondingly pressurized coolant leaves the compressor in turn via line 25

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The line 25 opens at a distribution point 26. From this distribution point 26, part of the coolant flows into a line 27 'through which it reaches the pipe of the reheater. Here the coolant gives off heat to the inside of the jacket of the reheater 11 located cool air and thus condenses. The condensed coolant leaves the reheater 11 via a line 28 through which it is fed to the receptacle 16. That part of the Coolant that is not passed through the reheater 11 arrives from the distribution point 26 via a Line 29 into the condenser 14. The condenser 14 can expediently be one in the form of a Radiators designed heat exchanger act, its. Pipes are ribbed. The fan 15 blows the Ambient air past these finned tubes and the coolant in the tubes gives off heat to the air flowing past the tubes. This condenses Coolant and leaves the condenser 14 via a line 30 through which it reaches the receptacle 16.

When using the flow system according to FIG. 2, a number of advantages are achieved with regard to the mode of operation of such a system. The compressed coolant arriving at the distribution point 26 is divided into two streams so that it flies through two parallel heat exchangers 11 and 14 on its way to the receiving container 16.

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The amount of coolant flowing through the two flow paths in each case depends on the relative condensation capacity of the two heat exchangers 11 and 14, which is given at a specific point in time, and is correspondingly variable. The condensation capacity of the two exchangers is in turn determined by the heat flow present there at a given point in time and since the operating conditions, for example the temperature and humidity of the introduced gas and the temperature of the ambient air, change, the heat flow in the heat exchangers changes accordingly. If the heat flow in one heat exchanger increases relative to the heat flow in the other exchanger, this has the consequence that the pressure prevailing in the first exchanger on the coolant side has a tendency to drop in pressure. This increases the pressure difference between the inside of the first heat exchanger and the upstream side located Yteileretelle 26 increased. This increase in pressure Unters chi s eäe out there will be an increased _k flow of refrigerant from the point 26 in the first heat exchanger, while in the second heat exchanger flows correspondingly less. The flow rate flowing into the first heat exchanger increases until the pressure prevailing in this heat exchanger is equal to the pressure given in the second heat exchanger. As soon as this state is reached, the relative flow rates in the two parallel currents aö'lSiSgö g®g © 3 & Qiaa & der 'are stabilized _r to © e in the water flow of the

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there is a further relative change in both heat exchangers. In summary, it can be said that the flow rates in the two streams are constantly like this. balance each other so that the same pressure is maintained in the two heat exchangers · on these In this way, the condensation load is constant and automatic divided between the two heat exchangers, in each case in proportion to their relative Effectiveness. This self-sharing of the coolant condensation load between the heat exchangers 11 and largely contributes to increasing the capacity of such a system, as it also makes a somewhat more humid one compressed product gas stream can be introduced if this appears to be desirable. So if the The speed of the introduction of wet grass into the cooler 10 is increased, so that is the exiting from the cooler 10 and into the reheater 11 entering gas correspondingly warmer and thus has a lower ability to cool the Refrigerant in the reheater 11. That in the reheater 11 entering compressed gas could even have a temperature which is above the temperature of the ambient

air lies. Even in such a condition, the amount supplied to the receptacle 16 would be liquid Refrigerant does not decrease significantly because of the condenser compensates for the missing amount.

Due to the parallel arrangement of the heat exchangers,

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as is the versatility of such a system for the treatment of compressed gases of different temperatures. For example, let us assume that there is a desire to discharge the compressed grass to dry at a dew point that is a certain number of degrees below the inlet temperature. Further it is assumed that the inlet temperature of the compressed gas is so high that even after cooling at the desired dew point, the temperature of the gas in line 19 is still above ambient temperature. So that in the reheater 11 is compressed Gas to a certain extent is unable to cool a coolant to serve, but here again the capacitor 14 operated at ambient air temperature takes over the load and supplies sufficient liquid coolant to the receiving tank to maintain the cycle.

Despite the increased adaptability described above, the system illustrated in Figure 2 becomes vast less influenced by changes in the ambient air temperature than the previously known systems. Increases, for example the outside air temperature increases and the condenser loses part of its ability to liquefy the coolant, so the reheater 11 strives to have a larger one To take over part of the liquefaction load and thus a sufficient one Ensure onward delivery of liquid to the container.

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- 17 -.

A few modifications of the arrangement according to the invention can also be explained on the basis of Pigur 2. If one first looks at that part of the system in which the compressed gas is located, one can see that, as far as the Pliessweg is concerned, the separator 20 between the cooler 10 and the reheater 11 is switched on. Although this is a very useful arrangement, the separator can also be used on others Places in the area of the cooler 10 (seen with respect to the Pliessweg) can be arranged and it may be desirable appear to arrange it so that gravity can be used in the Pliessweg, so that on this Way water gets into the separator. In addition, FIG. 2 shows only a single cooler stage, which corresponds to the Representation of the Pigur 2 is arranged in the heat exchange counterflow direction, but multiple cooling stages can easily be used and / or a flow arrangement running in the same direction can be provided, as is the case in heat exchange technology is common. The same also applies to the reheater 11.

With regard to that part of the system in which the coolant is located, it should be noted that in the arrangement According to Pigur 2, a receptacle 16 is shown, in which a sufficient "inertia ^ is given to the responsiveness of the cooling circuit to minor operating fluctuations in different ropes, for example in the compressor

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reduce. However, a separate receptacle is not absolutely necessary and the liquid coolant can also be passed directly from its liquefaction point to the expansion valve. Otherwise, FIG. 2 shows a compressed air condenser 14, but in smaller systems a convection condenser working with ambient air can also be used for reasons of economy.

Indeed, especially in systems with larger capacities, the two heat exchangers condensing the coolant are preferably arranged parallel to one another, as is also the case is the case in Figure 2, but a number of the advantages achieved according to the invention are still achieved, if the two exchangers are connected in series with one another. Such a series arrangement means that the all of the coolant is passed through the two heat exchangers, but still a split occurs the condensing load between the two exchangers, at least largely§achieve.An arrangement of the above described type is explained in detail with reference to FIG.

Figure 1 shows some structural features and those shown here As far as possible, parts are denoted by the same reference numerals as in FIG. 2. The parts shown in FIG The device shown has a frame structure 35 »on its e the tubular heat exchangers and in its

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lower rope the cooling device including the on a kind of tray 36 attached compressed air condenser are arranged. So the cooler 10 is backwards the top of the unit and is connected to the inlet line 18. Next to it or in front of it is the reheater 11 attached, which is also designed as a cylindrical heat exchanger and from which the outlet line 21 leads away. The cooler 10 and the reheater 11 are through a Line 19 connected to one another, which leads away from the bottom of the cooler at one end thereof and at the reheater opens at the bottom at the end of the same. The separator 20 is branched off from the line 19. This arrangement has the advantage that the separator 20 is located below the cooler 10 and the reheater 11 and thus not only in the Cooler 10 condenses the main part of the water, but can also collect any water that is still forming, which may still condense in the connecting line 19.

As mentioned above, there are the compressor 13, the receptacle 16, the blower 15 and the condenser 14 mounted on a type of plate 36. The arrangement is preferably such that the receptacle 16 is below of the outlet of the reheater 11 and the condenser 14 is in order to thus the effect of gravity for the heating

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to take advantage of the coolant condensed in these ropes. In the arrangement according to FIG. 1, the expansion valve 17 is located at the top left near the coolant inlet in the cooler 10. The various lines completing the cooling circuit are included the same reference numerals as in Figure 2, and the direction of flow is indicated by small arrows.

It is true that FIG. 1 shows a cooler 10 of the type in which only a single tube is provided in the heat exchanger is, however, it is to be understood that the same arrangement can be maintained even if instead of a single one Rohres a multiple tube arrangement is used for the heat exchanger. In addition, both heat exchangers with single and multiple tube arrangements, the single tubes inside the cooler are also coiled or otherwise arranged in a winding manner. The same also applies to the reheater 11, which according to the illustration of Figure only as a heat exchanger with a single Tube is designed, but it can also be designed as a heat exchanger with multiple tube arrangement which can also be wound in the form of coils or serpentines within the casing as desired.

Also in the optional embodiment of Figure 3 is a Cooler 10a, a reheater 11a, a gas inlet 18a, a water collecting container 12a and a gas outlet 21a are provided,

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all of which belong to that part of the system in which the compressed gas is located. Purely the coolant in the system according to FIG. 3 is a compressor 13a, an ambient air condenser 14a and a relaxation device 17a provided, which is designed in the form of a coiled wound capillary tube. The one shown in FIG Plant has a number of structural features that make it particularly suitable for such uses suitable, in which the flow rate of the compressed gas is relatively low.

Although the cooler 10a and the reheater 11a are functionally separate heat exchangers, however, they are combined in a single heat exchanger jacket 45. Piped sheath 45 is closed at its upper end by the head piece 46. A gas outlet 21a is screwed into this head piece 46. A coolant line is through the end face of the head piece 46 47 carried out, which in turn by a bung .49 is sealed gas-tight.

Similarly, the other end of the jacket is also closed by a head piece 50 into which a gas is admitted Uck 18a is screwed in. Likewise, a coolant line 51 is passed through the head piece 50, which

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is in turn closed gas-tight by a bung 52. Furthermore, a line 53 is also in the head piece 50 screwed, the other end in the collecting container 12a tastes.

As FIG. 3 shows, the cooler 10a is located inside of the jacket 45 below the reheater 11a, or in other words, the jacket 45 is more or less arranged running less vertically, so that the cooler 10a is located below the reheater 11a. Through this Arrangement and in that the water collection container is located below the cooler 10a, it is ensured that the water condensing in the cooler 10a under the action effectively separated by gravity and then collected in the collecting container 12a. The cooler 10a and the reheater 11a are inside the casing 45 by a piece of steel wool 53 'ο. Like. Separated from each other, the approximately from Radiator 10a catches levers rising upwards and thus acts as a water separator.

The reheater 11a has a pipe 54 through which the coolant to be condensed is brought into heat-exchanging contact with the cooled dry gas flowing through the Sheath 45 flows upward. This tube is provided with ribs 55 projecting into the casing space, as a result of which

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the effective heat exchange surface is increased accordingly will. The expansion capillary tube 17a is at the bottom of the tube 54 and the condensed coolant leaves the tube 54 through the capillary tube.

The expansion capillary tube 17a is in the space of the jacket enclosing the cooler 10a, among other things for reasons of space saving wound up in a coil, so that it has the necessary capillary length despite the small space requirement to serve as an effective relaxation device. In this context it should be noted that instead of the Capillary arrangement, a relief valve can also be provided. The capillary tube 17a is connected at the bottom to the tube 56, which forms the pipe part of the cooler 10a. As it flows through the capillary tube, it expands and relaxes Coolant and from there enters the tube 56 from below, where it is used for heat-exchanging contact with the warm » moist gas flows up through the cooler 10a. According to the representation in FIG. 3, the pipe 51 is sufficient into the heat exchange tube 56, but ends shortly before the upper end of the tube 56. The coolant evaporating in the tube 56 reaches the pipe 51 and from there to the compressor 13a. Just like the reheater tube 54 is the cooling tube preferably equipped with ribs 57 so that in this way the effective heat transfer surface is increased accordingly will.

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The above-described configuration of the tube results in an undesirable accumulation of coolant lubricants avoided in this tube. The lubricants commonly mixed with coolants are usually Least soluble in the coolant at the lower temperatures. That's why they have lower ones at these Temperatures have a tendency to accumulate and if this accumulation occurs at the coldest point of the system, they can At other points in the system, for example in the compressor, they no longer perform a lubrication function.

The coldest point of the cooling device according to FIG. 3 is located near the lower end of the tube 56, so that there is a risk that the lubricant will be separated from the coolant at this point and one from the liquid phase of the coolant at the bottom of the tube 56 forms separate liquid phase. After the evaporation of the coolant in the pipe 5β , it reaches the top and enters the pipe 51. The vapors flowing upwards take a film of lubricant along the outer surface of the tube 51 and into the interior of the tube 51. In this way, the lubricant deposited at the bottom of the tube 56 is continuously reintroduced into the coolant flow so that there is no undesirable lubricant

accumulation comes.

In the embodiment of Figure 3, the capacitor 14a

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designed as a simple finned tube that after works according to the convection principle with ambient air flowing past. If necessary, however, can also be used at this point other condenser designs including those with a fan can be used. Between the tubes 47 and a coolant bypass line 58 which is provided with a valve 59 is switched on. With the help of this arrangement the coolant can be routed around the heat exchanger, whereby the capacity of the system can be changed accordingly is. Optionally, however, for the same purpose ■ a suitable device for changing the Compressor capacity, for example, a switch-on and switch-off device can be provided.

The flow path through the system according to FIG. 3 will now be briefly explained, reference being made to the small arrows in FIG. 3 which indicate the direction of flow. The compressed gas passes through the inlet 18a into the system and via the head piece 52 into the casing of the cooler 10a. It then flows upwards through the cooler 10a, where it cools with loss of water. The cool gas then passes through the mist separating device 53 ′ and then enters the casing of the reheater 11a. Then it flows upwards with gradual heating through the reheater 11a and leaves the system through the head piece 46 and the outlet 21a. DaB deposited from the gas water falls through the jacket of the plant down in the head piece 50 and is

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from there passed via line 53 into the collecting container 12a.

The refrigerant is compressed in the compressor 13a and conducted to the condenser 14a, where its heat azi the ambient air gives away. There is indeed the possibility that only a small one or none at all in the heat exchanger 14a Part of the coolant condenses, but by losing heat, the coolant at least approaches that Condensation point. The coolant then flows through the line 47 into the upper cable of the reheater 11a and condenses in tube 54 of the reheater. The liquefied coolant then exits tube 54 and enters into the capillary tube 17a, where it expands and relaxes and then enters the tube 56 of the cooler 10a. Here the coolant evaporates and leaves the pipe 56 through the pipe 51 'through which it is fed to the compressor 13a. As the above description makes clear, the arrangement in the system according to FIG. 3 is such that the two Heat exchangers 11a and 14a. for coolant treatment · not like the corresponding heat exchangers in the arrangement according to Figures 1 and 2 are connected in parallel but in series with one another.

FIG. 4 shows a side view of the upper rope of Installation according to FIG. 3. As shown in FIG. 4, hesrwrgsSit »consists

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the casing 45 made of a transparent material. The transparency of the cladding is for the purposes of Invention only in the area of the reheater 11a of importance, but it is useful to cover the sheathing to manufacture their entire length from one and the same transparent material. Inside the casing 45 is located one extending over the entire length of the reheater 11a Strips of a display or indicator material 60. This indicator 60 can expediently consist of a strip of paper impregnated with an appropriate chemical substance which gives its color within changes over a narrow range of humidity, as is the case with cobalt chloride or cobalt bromide, for example. The indicators can be selected at will and there is also the possibility of choose another form of display for this, for example by placing granulated indicator substance over the ribs of the reheater 11a is distributed over its entire length or almost its entire length.

As can be seen, the indicator thus extends over a substantial part of the length of the reheater 11a on the compression gas side. The cool compressed gas enters the reheater with a relative humidity of essentially $ 100>. In the hate in which it warms up as it "flows through the reheaters" becomes his

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relative humidity gradually decreases and it reaches its lowest value at the outlet end of the reheater, where the gas is warmest. The indicator used should change its color at a relative humidity, those lower than 100 # and higher than the output target gas humidity is. If the indicator is selected from this point of view, then there is a length at one point of the reheater a point at which the gas has a relative humidity equal to the humidity value, in which a color change occurs on the indicator. At this point there will be a color indicator line on the indicator strip visible. Such a line is indicated in FIG. 4 on strip 60 at 61.

This color indicator line serves as a very effective control and control aids for the drying device according to the invention. To the extent that the product gas becomes more humid, the line shifts upwards in the direction of the outlet End of reheater closed. If, on the other hand, the product gas becomes drier, the line shifts to the inlet side End of the reheater. For a given unit, for example, the position of this indicator line be brought into a corresponding correlation with the relative humidity of the product gas and according to one on this Wise calibration made separate measurements of the relative humidity unnecessary, since the operating personnel

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Can read moisture directly from the color indicator. If the operator notices that the position of the color indicator line has changed, it is a display given that the relative humidity has changed, according to which a possibly provided Calibration scale can be used to determine which new relative humidity is now present. The change goes in one undesired direction in front of them, the operating personnel can easily take appropriate remedial measures, by changing the flow rate, for example, so that in this way the relative humidity is set back to the desired value.

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Claims (12)

- 30 claims 1J Method for drying compressed gas by cooling the same using a closed circuit, in which a coolant passes through a compression-condensation and an expansion-evaporation stage, the gas to be dried being brought to heat exchange with the liquid coolant and thus the gas is cooled and Water is condensed therefrom, while the coolant evaporates, and the condensed water is separated from the gas and the cooled gas is brought to heat exchange with a fluid supplied to the first heat exchanger, thereby heating the gas and reducing its relative humidity, characterized in that the with the fluid brought to the cooled gas for heat exchange is a condensed and compressed coolant and that the ambient air is brought to heat exchange with at least a part of the compressed coolant for cooling the same. 2. The method according to claim 1, characterized in that. the compressed coolant with the ¹ cooled gas and 'with ambient air in parallel to each other! it ^ osien for heat exchange. brought and at least one rope of the 009836/1046 compressed coolant is condensed by the heat exchange with the ambient air. 3. The method according to claim 1 or 2, characterized in that the gas "when it is heated on an indicator (60) is bypassed, in which a color change (at 61) at a predetermined relative humidity a point located along the flow path of the heated gas occurs, so that a measure for the relative humidity of the heated and dried gas is given. 4. The method according to claim 3, characterized in that a color display line (61) is created on the indicator (60) and the position of this line along the length of the indicator in the flow path of the relative humidity of the gas depends at the point at which it is fed to its further use. 5. Drying device for carrying out the method according to One or more of the preceding claims with a first heat exchanger in which the compressed to be dried Gas and the coolant to be evaporated are brought to heat exchange with each other, and one in the vicinity the first heat exchanger attached water separator, fn which the compress in the first heat exchanger from the! Gas accumulated and condensed water 009836/1046 is diverted so that the water no longer comes into contact with the gas, while at the same time preventing major gas losses, characterized in that that a second heat exchanger (11) is provided, in which the relatively dry cool compressed gas and the coolant to be condensed for heat exchange are brought together, and that a third heat exchanger (14) is provided in which the ambient air and the coolant to be condensed are brought to heat exchange with one another, with corresponding Lines (18, 19 »21) are provided through which the compressed gas from an inlet point through the first heat exchanger (10) and then through the second heat exchanger (11) and to an outlet point flows, and that a closed circuit is provided in which the coolant has a compression-condensation and undergoes an expansion / evaporation stage, wherein the coolant to be evaporated to the first heat exchanger through a corresponding line routing (22 to 29) (10) and the coolant to be condensed is fed to the second and third heat exchangers (11, 14) will. 6.Drying device according to claim 5 with a compressor for the coolant, characterized in that in the coolant » line an expansion device (17) is connected that the first heat exchanger (10) and the compressor (13) Row to each other and that also the 009836/1046 second and third heat exchangers (11, 14) between the compressor (13) and the expansion device (17) are switched on. 7. Drying device according to claim 6, characterized in that that a receptacle (16) is provided for the coolant and that the coolant lines (22, 23, 24) the receptacle (16), the expansion device (17) »the first heat exchanger (10) and the compressor (13) connect in series with each other. 8. Drying device according to claims 5, 6 or 7, characterized in that the line routing is such that the coolant to be condensed to the second and third heat exchangers (11, 14) in parallel to each other Flow paths (27ι 28 and 29, 30) is fed. 9 · Drying device according to claim 5 or 6, characterized in that that the line routing is chosen such that the coolant to be condensed first to the third Heat exchanger (14a) and then the second heat exchanger (11a) is fed. 10. Drying device according to claim 5 »6 or 9, characterized characterized in that the first and second heat exchangers (10a, 11a) each consist of a tube with a coating and the compressed gas through the 009836/1046 jacket flows, and that further for the first and the second heat exchanger a common, generally cylindrical jacket (45) Torgeseiien _9, the arrangement is such that the first heat exchanger is arranged lower than the second heat exchanger, and that the water separator with one below the First heat exchanger (10a) attached collecting container (12a) and the cooling system is provided with an expansion device (17a) for the coolant, which is located inside the jacket and connects the second and the first heat exchanger to one another. 11. Drying device according to one or more of the claims 5 to 10, characterized in that the second heat exchanger (11a) has a transparent wall (45) is provided, through which the gas flow area to the outside over a substantial part of the gas flow path is visible through the second heat exchanger, and that from the second heat exchanger (11a) on the On the gas side of the same, an indicator (60) is attached to a point visible through the transparent wall is at which at a predetermined relative humidity a color change occurs, and that this Indicator over a substantial part of the flow paths B. by the second. Heat exchanges !? ^ s 009836/1046 12. Drying device in particular according to one or more of claims 5 "to 11, characterized in that a substantially vertical evaporation tube (56) with closed ends in the first heat exchanger (10a) attached and the coolant ent tensioning device (17a) is connected to the evaporation tube at the lower end of the same in such a way that the expanded liquid coolant enters the tube for evaporation, and the one in the bottom area of the evaporation tube opens into this Coolant discharge pipe (51) in the evaporation pipe up to just before the upper end of the evaporation pipe so that the flue pipe extends through the evaporation pipe and its outer surface extends with the liquid refrigerant normally found in the evaporation tube and with the low one Temperatures from this excreted lubricant is in contact. 009836 / 10A6