FR2510422A1 - METHOD AND APPARATUS FOR DRYING COMPRESSED GAS, PARTICULARLY COMPRESSED AIR - Google Patents

Abstract

THE PROCESS IS OF THE TYPE IN WHICH THE GAS IS FIRST COMPRESSED AT A HIGHER PRESSURE THAN THE DESIRED FINAL PRESSURE AND THEN IT IS RELAXED AT THE FINAL PRESSURE; IT IS CHARACTERIZED IN THAT THE GAS IS COOLED BEFORE RELAXING AT THE FINAL PRESSURE AND IT IS USED FOR THAT COOLING DUE TO THE RELAXATION. THE UNIT COMPRISES A HIGH PRESSURE GAS LINE 1 AND A REGULATOR 6 WHICH ARE IN GOOD THERMAL CONTACT BETWEEN THEM. THIS CONTACT CAN BE MECHANICALLY ESTABLISHED BUT ALSO BY A LIQUID CIRCULATION 3, 8, 9, 10.

Description

The present invention relates to a method for drying or dehydrating a

  Compressed gas, in particular compressed air, in which the gas is first compressed to a pressure higher than the desired final pressure and then it is expanded to the final pressure The invention further relates to an apparatus for setting in

process work.

  It is often necessary that a compressed gas does not

  holds no more than a certain maximum humidity Air to cicimaga-

  siner in steel bottles, for example, to be used in combination with diving equipment or smoke control equipment, should preferably have a relative humidity below 70% This in order to avoid the development of bacteria in the air, the blocking of diving valves by icing and the corrosion of the cylinder As regards the last point, it is necessary to

  also take into account the increase in the partial pressure of oxy-

uncomfortable.

  The Norwegian Labor Inspectorate has created a regulation

  information on maximum permissible humidity Meeting these regulations is difficult, however, and requires, for example,

expensive mechanical filtering.

  The reason why a compressed gas, especially compressed air, is very humid in the absence of special dehydration measures is that the humidity increases in the same proportion as condensation or compression. liter of air at 50% humidity at 1 bar in half a liter at 2 bars the humidity will be%. It is known to compress a gas, for example air, to a pressure higher than the desired final pressure and to

  then allow to relax at the final pressure This operation

  tion is of course carried out to dehydrate the air For example, if the air is compressed to 300 bars, where it has a humidity of 100%, and it is allowed to relax to 200 bars, the air at this pressure

  final will have a humidity of about 66%, i.e. 300.

  The invention constitutes an improvement of this pro-

  yielded and allows to obtain, in a simple and economical way, a dehydra-

further air intake.

  To this end, the gas is cooled before its expansion to the final pressure and the cooling due to expansion is used for this. The physical principle is therefore used, according to which the heat imparted to the gas during compression is transferred again to expansion.

  By cooling the gas while its pressure is higher

  higher than the desired final pressure, water precipitation occurs and, according to a characteristic of the invention, the separated liquid

  is precipitated upstream of the relaxation zone -

  An apparatus for carrying out the process comprises a high pressure gas line and an expansion valve or pressure reducer and it is characterized in that the line is in good condition

  thermal contact with the regulator.

  According to one embodiment, the good thermal contact is established by a circulating liquid which is in exchange contact

  thermal with the high pressure line and with the regulator.

  According to a second embodiment, the high pressure gas pipe is directly, mechanically, in thermal contact with the pressure reducer, for example because the pipe is

  arranged in a serpentine around the regulator.

  According to the process of the invention, a phenol is used.

  leads physically to dehydrate an almost free compressed gas, compressed air in particular, avoiding costly filtering and

annoying mentioned above.

  Other characteristics and advantages of the invention

  will emerge more clearly from the following description of two

  nonlimiting exemplary embodiments, as well as of the appended drawing, in which: FIG. 1 is a schematic representation of an apparatus according to a first embodiment of the invention; and Figure 2 is a similar view of a second example

of achievement.

  In FIG. 1, a line 1 comes from a compressor, delivering air at a pressure of 300 bars, for example Line 1

  passes in the form of a helical coil 2 through a cooling chamber

  pipe 3 When leaving this room, pipe 1 passes through a

  water separator 4 fitted with a drain tap 5 From the separator

  line 4, line 1 leads to an expansion valve or pressure reducer 6 which reduces the air pressure, so that it is no more than bars, for example in the discharge line 7, which is then the final pressure desired The regulator 6 is surrounded by a liquid chamber 8 which, in combination with a line 9 and a line

  return 10 forms a closed circuit with the cooling chamber

  ment 3 The entire device is enclosed in an envelope 11

thermally insulating.

  The device operates as follows: The heated humid air at high pressure which comes from the compressor via line 1 gives heat to the liquid in the cooling chamber 3 This liquid is transported by the return line 10 to the chamber 8 and is cooled by the cooling effect due to the expansion in the regulator 6 The liquid thus cooled is brought back-via line 9

  to chamber 3 This circulation can be maintained by a pump 12.

  It is, however, also possible to turn the apparatus 90, so that chamber 3 is at the bottom, in order to obtain an effect

  thermo-siphon to eliminate the pump 12.

  FIG. 2 shows a second example where the pipe 1 coming from the compressor and supplying the humid and heated air is arranged in a coil 13 in good thermal contact with the pressure reducer 6 around it The air is in this case cooled in the coil 13 and then passes through the regulator 6 in the discharge line 7 This apparatus also includes a water separator with a tap

  purge 5 upstream of the entry of high pressure gas into the

deur.

Claims (6)

R E V E N D I C A T I 0 N S   1 Method for drying or dehydrating a compressed gas, in particular compressed air, according to which the gas is first compressed to a pressure higher than the desired final pressure and then it is expanded to the final pressure by an expansion valve or pressure reducer, characterized in that the gas is cooled before its expansion to the final pressure and the cooling due to this is used to relax.   2 Method according to claim 1, characterized in that   the separated liquid is precipitated upstream of the regulator.   3 Apparatus for implementing the method according to claim 1, comprising a high pressure gas line and a pressure reducer, characterized in that the high gas line (1)   pressure is in good thermal contact with the regulator (6).   4 Apparatus according to claim 3, characterized in that a liquid separator (4) is disposed on the high pressure side of the regulator. Apparatus according to claim 3 or 4, characterized in   that the device is thermally insulated.   6 Apparatus according to any one of claims 3   to 5, characterized in that the thermal contact is established by a circulation of liquid (3, 8, 9, 10) in heat exchange contact   with the high pressure gas line (1) and with the regulator (6).   7 Apparatus according to any one of claims 3   to 5, characterized in that the high pressure line (1) is directed   mechanically, in thermal contact with the pressure reducer (6), for example thanks to the fact that the pipe (1) is arranged in a   helical coil around the regulator (6).