AU2001248140B2

AU2001248140B2 - Compressor/drier system and absorber therefor

Info

Publication number: AU2001248140B2
Application number: AU2001248140A
Authority: AU
Inventors: Anthony John Kitchener
Original assignee: Sullair LLC
Current assignee: Hitachi Global Air Power US LLC
Priority date: 2000-04-11
Filing date: 2001-04-10
Publication date: 2006-11-09
Anticipated expiration: 2021-04-10
Also published as: AU4814001A

Description

0 COMPRESSOR DRIER SYSTEM AND ABSORBER THEREFOR The present invention relates to improvements in compressor systems o adapted to provide clean dry compressed gas, particularly compressed air, at a discharge point therefrom, and an absorber configuration for use in such systems.

There is increasingly a need to provide moisture free pressurized gas, particularly compressed air, in many industries and applications. Such moisture free compressed gas or air is normally achieved by using separate add on gas 00 drying equipment such as refrigeration driers. Such additional drying equipment _is typically expensive to produce, and complicated and costly to operate. The objectives therefore of the present invention are to provide a simplified inexpensive means for producing dry pressurized gas including compressed air and an improved moisture absorber for use in such systems.

Accordingly, the present invention provides in one aspect, a drier for drying compressed gas, said drier being adapted to receive compressed gas to be dried from a gas compressor means, the compressed gas being delivered to a moisture absorber configured to receive and circulate therethrough a fluid capable of removing moisture from the compressed gas prior to the compressed gas being discharged as a dry compressed gas through filter means to remove any remaining said fluid therefrom, said fluid being circulated through a circuit including a moisture stripping means adapted to receive a portion of the dry compressed gas discharged from the moisture absorber and passing said portion of the dry compressed gas in moisture exchange relationship with said fluid prior to reintroducing said fluid into said moisture absorber, said fluid being heated after leaving said moisture absorber and before entering said moisture stripping means.

With such an arrangement the fluid within the circuit need not be particularly hygroscopic in nature but improved performance may be expected if the fluid is in fact hygroscopic in nature, i.e. capable of absorbing or attracting moisture. It has been surprisingly found that by heating the fluid before it enters the moisture stripping means improves overall performance by minimizing the amount of dry compressed gas that needs to be diverted from the dry compressed gas discharge line from the system. Overall efficiency of the system is preferably improved by utilizing waste heat generated by the gas compression means.

Preferably the discharged compressed gas from said gas compressor means is passed initially through a first cooler means to condense at least a portion of the moisture carried by the compressed gas which is collected and removed from the o compressed gas flow prior to entering said absorber.

According to a second aspect of this invention, there is provided a drier for drying compressed gas, said drier being adapted to receive compressed gas to be dried from a gas compressor means, the compressed gas being delivered to a moisture absorber configured to receive and circulate therethrough a fluid capable 0 of removing moisture from the compressed gas prior to the compressed gas being discharged as a dry compressed gas through filter means to remove any remaining said fluid therefrom, said fluid being circulated through a circuit including a moisture stripping means adapted to receive a portion of the dry compressed gas discharged from the moisture absorber and passing said portion of the dry compressed gas in moisture exchange relationship with said fluid prior to reintroducing said fluid into said moisture absorber, said fluid being heated after leaving said moisture absorber and before entering said moisture stripping means, said fluid being cooled after leaving said moisture stripping means and before entering said moisture absorber. Again performance is improved if the fluid has hygroscopic characteristics. Further preferred aspects and features of the drier may be as defined in claims 17 to 33 as annexed hereto which are hereby made part of the disclosure of this specification by this reference thereto.

In accordance with a further aspect, the present invention also anticipates providing a gas compressor system including a driven gas compressor means adopted to receive gas to be compressed including a drier as described above.

The gas compressor system may include features as defined in any one of claims 6 to 16 as annexed hereto, the subject of these claims being incorporated into the disclosure of this specification by this reference thereto.

Various preferred embodiments and features of aspects of this invention will become clearer from the following description given in relation to the accompanying drawings, in which: Figure 1 schematically illustrates a first preferred embodiment of a gas compressor system according to the present invention; Figures 2 and 3 schematically illustrate two further preferred embodiments of similar gas compressor systems;

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O Figure 4 illustrates a still further embodiment of a gas compressor system while also illustrating features of a preferred absorber construction; o Figure 5 illustrates the preferred absorber construction shown in Figure 3 with a common gas receiver vessel; and Figure 6 illustrates in partial side view, further features of the preferred absorber construction; Referring first to Figure 1, the illustrated compressor system includes a 0 rotary compressor unit 10 driven by a motor 11 which receives a gas (typically air) _to be compressed at 12 via an inlet valve 7. The rotary compressor unit 10 may be a screw compressor of any known configuration or in fact any other form of rotary compressor. The system further includes a separator vessel 13 receiving compressed gas and entrained lubricant via line 14 with a preliminary separation of gas and lubricant occurring therein. The lubricant is collected in a lower region of the vessel 13 and returned via line 15 and a lubricant cooler 16 to a lower pressure region of the compressor unit 10. Compressed gas leaves the vessel 13 via a preliminary filter means 17 and a minimum pressure valve 18. The compressor system thus described is essentially conventional in nature and within the context of this invention might be substituted by any other known similar rotary compressor system.

The compressed gas flow leaving the separator vessel 13 is conveniently cooled in a gas cooler device 19 such that at least a portion of the moisture is cooled, condensed, collected and drained away at 20 from the system. The cool humid compressed gas flow is then passed via line 21 to an absorption column 22 where a shower of cool dry hygroscopic fluid is falling. As the compressed gas flow passes upwardly through this shower, moisture is absorbed into the hydroscobic fluid flow conveniently originates via diverting a portion of the lubricant flow in line 15 through a line 23 and thereafter passing same through a further lubricant cooler 24 prior to delivering same to the absorption column 22.

In an alternative arrangement the diverted flow might be after the cooler 16 with or without further cooling.

The lubricant falls to the bottom of the absorption column 22 where it is collected and conveniently passed via line 25 back to line 15 or some other lower pressure region of the compressor circuit including the compressor unit 10. This

IND

lubricant flow then mixes with the main lubricant flow where it is heated and the absorbed moisture flashes into vapour. This vapour is subsequently condensed c in the gas after cooler device 19 and at least partially drained away at 0 The cool dry compressed gas flow leaving the absorption column 22 passes through a final filter means 26 so that no droplets of coolant can escape with the clean dry compressed gas discharge at 27. Conveniently lubricant purge lines 28, 29 are operatively associated with each of the filter means 17 and 26 to 00 return any collected lubricant back to a lower pressure portion of the compressor system such as the compressor unit 10 itself. Further possible changes to the system may include integrating the absorption column 22 into the separator vessel 13 whereby a secondary vessel is not required. Alternatively, the absorption column 22 might be integrated into the air receiver tank as shown in Figure Referring now to Figures 2 and 3, there is illustrated a compressor system 9 including a gas compression device 8 which in the illustration is a rotary compressor device similar to that described in the foregoing with reference to Figure 1. It should, however, be recognised that any other form of gas compressor devices including reciprocating devices could be used.

Similar to the system described with reference to Figure 1, the compressed gas flow leaving the separator vessel 13 may be conveniently cooled in a gas cooler device 19 such that at least a portion of the moisture contained within the gas is cooled, condensed, collected and drained away at 20 from the system.

The cool humid compressed gas flow is then passed via line 21 to an absorber column 22, preferably in the form of an upright column where a shower of cool dry hygroscopic fluid is falling. As the compressed gas flow passes upwardly through this shower, moisture is absorbed into the hygroscopic fluid flow. It should be appreciated that any other form of absorber might be used.

The lubricant falls to the bottom of the absorber column 22 where it is collected and conveniently passed via line 25 in a closed circuit 6 back to the absorber column 22 via a heat exchanger 28 and line 29. The heat exchanger 28 may take up heat from the returning hot lubricant in line 15 from the separator vessel 13. Alternatively, an electric coil 31 might be used to heat the liquid in the aforementioned closed circuit. A still further alternative may be to use heat from

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the exiting compressed gas in the cooler 19 as shown in dashed outline. Such heating of the fluid conveniently minimizes the amount of dry compressed gas c that needs to be diverted from the dry compressed gas discharge line as 0 described hereinafter.

The cool dry compressed gas flow leaving the absorber column 22 passes through a final filter means 26 so that no droplets of absorber liquid can escape _with the clean dry compressed gas discharge at 27 possibly to a gas air receiver 0 tank. Conveniently a lubricant purge line 29 is operatively associated with the _filter means 17 to return any collected lubricant back to a lower pressure portion of the compressor system such as the compressor unit 10 itself. Further possible changes to the system may include integrating the absorber column 22 into the separator vessel 13 whereby a secondary vessel is not required. Alternatively, the absorber column 22 might be integrated into the air receiver tank 32 as shown in Figure The compressor system of Figure 3 is essentially similar to that of Figure 2 except that in Figure 2 the compressor system 9 is constructed as a common support platform 9 whereas in Figure 3, the absorber may be constructed as a support platform 5 different to the support platform 4 of the compressor 8 thus providing a separate gas drier assembly.

In Figures 2 and 3 a moisture stripper 32, preferably in the form of a column, is provided cooperatively working with the absorber column 22. Fluid exiting from the column 22 may pass via line 25 through the heat exchanger 28 or, in an alternative embodiment may pass via line 33, to the moisture stripper column 32. A portion of dry compressed gas may be taken from the discharge line 27 and delivered via line 34 to the stripper column 32 such that it may pass in contact with the fluid in the circuit 6 after it has left the absorber column 22 where it has picked up moisture. The dry air or gas delivered to the stripper column 32 effectively dries the fluid passing through the stripper column 32 before it enters the absorber column 22. Moisture picked up by the gas air passing through the stripper column is discharged via line 35 as vapour. Diverting dry compressed gas from the discharge line 27 in this way provides an inefficiency in the system and therefore it is desirable to minimize the amount of dry gas diverted from the line 27. Liquid moisture absorber medium entering the absorber 22 should be

IND

0 cool for proper operation and accordingly, a cooler 70 may be provided in the line S23 following the pump 30 leading to the absorber 22. The pump 30 may be any c known type including electrically driven or air driven pumps utilizing compressed 0 air from the discharge 27. As a possible alternative to the cooler 70, a heat exchanger 71 may be provided between the line 23 and the line 29.

With arrangements as illustrated in Figures 2 and 3, the liquid within the substantially closed circuit 6 need not be particularly hygroscopic in nature but 0 improved performance may be achieved if it was hygroscopic in nature. Glycol _based fluids may be suitable for this application including glycol based lubricants such as Ingersoll Rand's Ultra coolant and Kluber-Summit's Supra coolant.

Figure 4 illustrates a preferred construction of absorber for use in compressor systems as described above, or in fact for any other application. The compressor system 9 is similar in nature to that shown in Figures 1 and 2 except that the preliminary cooler 19 has been omitted and the line 35 is directed to the inlet gas flow 12 to the compressor 10. Like features in the earlier embodiments have been given the same reference numerals in Figure 4.

The absorber column 22 has an outer upright cylindrical shell or casing 36 closed at an upper end by plates 37, 38 and at a lower end by plate 39. Located within the outer casing 36 are a plurality of plates 40 each with a plurality of small gas flow holes 41 in a predetermined array. The plates 40 each have three vertical tubes 42 or conduits passed through apertures in the plates 40 such that the position of the tubes 42 can be adjusted relative to the plates prior to being fixed in an adjusted position. As best seen in Figure 7, the tubes 42 are closed at the bottom by end caps 43 each having a reduced foot portion 44 to allow liquid flow around the foot portion. It will of course be appreciated that, depending on performance requirements, the number of tubes 42 per plate 40 can be varied depending on allowed space. Each tube 42 has at least one opening 45 adjacent the lower end caps 43 as well as at least one reduced volume flow opening adjacent their upper edges. The reduced volume flow openings may be one or more apertures 46 or notches 47 as illustrated in Figure 7. To enable an absorber column to be built of any desired capacity, a selected number of modules 48 consisting of a plate 40 and one or more tubes 42 can be stacked one on another within an outer cylindrical casing of desired length. Compressed

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O gas may enter the absorber column 22 via line 21 and a port 49 in the lower end C plate 39. The gas essentially travels upwardly through the absorption zone c within the casing 36 by passing successively through the holes 41 in the plates 0 Dry liquid is delivered via line 51 from the pump 39 to a port 52 in the upper end plates 38, 37. The liquid travels down the tube 53 in the absorber column 22 to be discharged onto the uppermost plate 40. Gas travelling up through the holes 41 in this plate causes the liquid to bubble or froth up and flow eventually 0 into the upper ends of the tubes 42 to flow down these tubes to the next lower plate 40. This process is repeated in a cascade fashion until the liquid is collected in the lower chamber 54 and discharged therefrom via a port 55 in the lower plate 39 to line 29 or lines 29, 33 returning to the moisture stripper 32. In some applications it may be desired to keep a pool of liquid in the lower chamber 56 so that gas entering this chamber must pass through the liquid before reaching the lowermost plate 40. Compressed gas leaving the absorber 22 may conveniently pass through a coalescent type final filter means to remove any liquid picked up via the drying process in the absorber. The filter means 26 may be mounted from one of the plates 37, 38 to be positioned within the absorber. In some applications, a minimum pressure valve (mpv) 18 may be provided mounted to the gas outlet port 57 (Figure 4) or be separated therefrom (Figure 3).

Claims

1. A drier for drying compressed gas, said drier being adapted to receive compressed gas to be dried from a gas compressor means, the compressed gas being delivered to a moisture absorber configured to receive and circulate therethrough a fluid capable of removing moisture from the compressed gas prior to the compressed gas being discharged as a dry compressed gas through filter 00 means to remove any remaining said fluid therefrom, said fluid being circulated through a circuit including a moisture stripping means adapted to receive a portion of the dry compressed gas discharged from the moisture absorber and passing said portion of the dry compressed gas in moisture exchange relationship with said fluid prior to reintroducing said fluid into said moisture absorber, said fluid being heated after leaving said moisture absorber and before entering said moisture stripping means.

2. A drier according to claim 1 wherein the fluid has hygroscopic characteristics.

3. A drier according to claim 1 or claim 2 wherein the fluid is heated by heat exchange with a hot region of the compressor means.

4. A drier for drying compressed gas, said drier being adapted to receive compressed gas to be dried from a gas compressor means, the compressed gas being delivered to a moisture absorber configured to receive and circulate therethrough a fluid capable of removing moisture from the compressed gas prior to the compressed gas being discharged as a dry compressed gas through filter means to remove any remaining said fluid therefrom, said fluid being circulated through a circuit including a moisture stripping means adapted to receive a portion of the dry compressed gas discharged from the moisture absorber and passing said portion of the dry compressed gas in moisture exchange relationship with said fluid prior to reintroducing said fluid into said moisture absorber, said fluid being heated after leaving said moisture absorber and before entering said moisture stripping means, said fluid being cooled after leaving said moisture stripping means and before entering said moisture absorber. IND A gas compressor system including a driven gas compressor means adapted to receive gas to be compressed and discharge compressed gas c therefrom, said gas compressed system including a drier according to any one of 0 claims 1 to 4 whereby the discharged compressed gas from said driven gas compressor means is delivered to said moisture absorber. S6. A gas compressor system according to claim 5 wherein the gas 00 compressor means is a rotary compressor arrangement including a compressor N unit receiving said gas to be compressed and a liquid lubricant with the Scompressed gas and entrained liquid lubricant being delivered to and at least partially separated in a separator means, the liquid lubricant being recirculated from the separator means to the compressor unit, said hot region being a region of hot compressed gas discharged from the compressor means.

7. A gas compressor system according to claim 5 wherein the compressor means is a rotary compressor arrangement including a compressor unit receiving said gas to be compressed and a liquid lubricant with the compressed gas and entrained liquid lubricant being delivered to and at least partially separated in a separator means, the liquid lubricant being recirculated from the separator means to the compressor unit, said hot region being a region of hot liquid lubricant being returned to the compressor unit.

8. A gas compressor system according to claim 5 wherein independent heater means is provided to heat said fluid before entering said moisture stripping means.

9. A gas compressor system according to any one of claims 5 to 8 wherein the discharged compressed gas from said gas compressor means is passed initially through a first cooler means to condense at least a portion of the moisture carried by the compressed gas which is collected and removed from the compressed gas flow prior to entering said moisture absorber. A gas compressor system according to any one of claims 5 to 9 wherein Sthe gas compressor means, the absorber and the moisture stripping means are C.) o mounted on a common support platform. S11. A gas compressor system according to any one of claims 5 to 10 wherein the gas compressor means is mounted on a support platform separate to the Sabsorber and/or the moisture stripping means. 00 C 12. A gas compressor system according to claim 5 when appended to claim 4 Owherein the fluid is heated after leaving said moisture absorber and before N entering said moisture stripping means.

13. A gas compressor system according to claim 12 wherein the fluid is heated by heat exchange with a hot region of said compressor means before entering the moisture stripping means.

14. A gas compressor system according to claim 5 when appended to claim 4 wherein the discharged compressed gas from said gas compressor means is passed initially through a first cooler means to condense at least a portion of the moisture carried by the compressed gas which is collected and removed from the compressed gas flow prior to entering said moisture absorber. A gas compressor system according to claim 5 when appended to claim 4 wherein the gas compressor means, the absorber and the moisture stripping means are mounted on a common support platform.

16. A gas compressor system according to claim 5 when appended to claim 4 wherein the gas compressor means is mounted on a support platform separate to the absorber and/or the moisture stripping means.

17. A drier according to any one of claims 1 to 4, wherein the moisture absorber is a moisture absorber column including an outer housing defining a vertically disposed absorption zone, a plurality of vertically spaced partition members traversing the absorption zone and each having a plurality of gas flow 0 openings formed therein, at least one conduit member extending through an Saperture in each said partition member to have a first portion extending upwardly c from the partition member and a second portion extending downwardly towards 0 the next adjacent said partition member located below said partition member, the conduit member having liquid flow means at or adjacent a lower end arranged to allow liquid flow from within the conduit member across the partition member located beneath said conduit member, said absorber column having liquid inlet 00 means arranged to deliver liquid to the uppermost said partition member and _liquid outlet means to withdraw liquid from a region below the lowermost said partition member, gas inlet means arranged to deliver gas to the region below the lowermost said partition member whereby said gas flows upwardly through the gas flow openings formed therein, and gas outlet means arranged to withdraw gas from the absorption zone above the uppermost said partition member.

18. A drier according to claim 17 wherein a liquid retaining zone is provided within said absorption zone through which gas must pass when flowing through said absorption zone.

19. A drier according to claim 18 wherein the liquid retaining zone is located beneath the lowermost partition member. A drier according to any one of claims 17 to 19 wherein at least three said conduit members are provided extending through each said partition member.

21. A drier according to any one of claims 17 to 20 wherein the lower end of each said conduit member is closed.

22. A drier according to claim 21 wherein at least one liquid flow opening is formed through each said conduit member adjacent the closed lower end.

23. A drier according to claim 21 or claim 22 wherein the lower end of each said conduit member engages the next adjacent said partition member located below the partition member through which the conduit member passes. IND O 24. A drier according to claim 23 wherein the lower end of each said conduit N member is supported on a reduced area zone or zones whereby liquid can flow c underneath the lower end or ends. 0 A drier according to any one of claims 17 to 24 wherein a reduced volume flow zone is formed at or adjacent the upper end of the or each said conduit 00 member. S26. A drier according to claim 25 wherein the reduced volume flow zone is Sformed by at least one aperture.

27. A drier according to claim 25 wherein the reduced volume flow zone is formed by at least one notch formed in an upper edge of the or each said conduit member.

28. A drier according to claim 25 wherein the or each notch is formed as a square, rectangular or triangular shape.

29. A drier according to any one of claims 17 to 28 wherein the outer housing is formed by a cylindrical upright outer wall closed at upper end lower ends by plate members through which the gas inlet and outlet means and the liquid inlet and outlet means pass. A drier according to claim 29 wherein each partition member has an outer circumference conforming to an internal circumference of said cylindrical upright outer wall.

31. A drier according to any one of claims 17 to 30 wherein a coalescent type filter means is provided within the outer housing above the uppermost partition member through which gas must pass to reach the gas outlet means.

32. A drier according to claim 31 further including a minimum pressure valve (mpv) arranged to receive gas from said gas outlet means.

33. A drier according to claim 32 wherein the minimum pressure valve is mounted from said outer housing. C)

34. A gas compressor system including a driven gas compressor means adapted to receive gas to be compressed and discharge compressed gas therefrom, said gas compressor system including a drier according to any one of claims 17 to 33. 00 A gas compressor system according to claim 34 further including a Opressurised gas receiving vessel to receive and temporarily store compressed C gas, said moisture absorber column being positioned within the pressurised gas receiving vessel. DATED this 20th day of October 2006 ANTHONY JOHN KITCHENER WATERMARK PATENT TRADE MARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA P18220AUPC SKP/MEH