GB2138553A

GB2138553A - Apparatus for conditioning compressed gas

Info

Publication number: GB2138553A
Application number: GB08310207A
Authority: GB
Inventors: Andrew Thomas Tomlinson
Original assignee: PENTAGON RADIATORS
Current assignee: PENTAGON RADIATORS
Priority date: 1983-04-14
Filing date: 1983-04-14
Publication date: 1984-10-24
Also published as: GB8310207D0

Abstract

Apparatus for conditioning compressed gas to reduce its water content comprises an after cooler (12) connected to the compressor (10) so as to condense out a major proportion of the water content from the gaseous phase. A separator (14) removes water droplets prior to the compressed gas being fed to fluid pressure powered equipment (15). In contrast with conventional apparatus, the after cooler (12) is connected to the compressor (10) via a heat exchanger (20) which brings at least part of the cooler dried gas into heat exchange relation with the hotter gas from the compressor to cool the latter before entry into the aftercooler. The dried gas is then supplied to the utilising equipment (15). <IMAGE>

Description

SPECIFICATION Apparatus for conditioning compressed gas This invention relates to apparatus for conditioning compressed gas (especially air) prior to its supply to equipment which uses the compressed gas for example to perform work.

The production of compressed air by a compressor raises the temperature of the air above ambient. To reduce the water content of the compressed air, it is well known to connect the outlet of the compressor to a water or air cooled aftercooler so as to cool the air below its pressure dew point. The compressed air from the aftercooler is usually saturated with water vapour as a result of cooling and the condensed water content can be substantially reduced by passing the compressed air through proprietary filtration/separation equipment.

In this way, it is possible to reduce corrosion and related problems due to condensation as the moisture-carrying compressed air passes through pipework since the amount of water that can condense is correspondingly lower after conditioning as described above. Nevertheless, the extent to which the air can be dried by these means is insufficient for many applications and it has often been necessary to supplement the aftercooler with some form of air drier using refrigeration or chemical absorption techniques to reduce the water content further.

Although the use of an air drier does reduce water content to levels at which no significant condensation occurs in practice, conventional air driers require energy input either to warm the air after cooling by the refrigerant or to regenerate the chemical for re-use. Consequently, the use of an air drier entails higher capital and running costs.

The object of the present invention is to provide improved conditioning apparatus in which the problems associated with the water content of the compressed gas can be alleviated significantly without the need for an air drier in addition to an aftercooler.

According to the present invention we provide apparatus for conditioning compressed gas (e.g.

air) to reduce its water content, the apparatus comprising a cooler for cooling the compressed gas so as to cause condensation of at least part of the water content thereof and means for removing condensed water droplets from the compressed gas, characterised in that the compressed gas is supplied to the cooler via a heat exchanger in which the compressed gas upstream of the cooler is in heat exchange relation with the compressed gas downstairs of the cooler.

In this way, the hotter upstream gas is cooled by the cooler downstream gas and the latter is raised to a higher temperature as a result. Such preliminary cooling of the hotter gas reduces the cooling load of the cooler, hence allowing the cooler to reduce the compressed gas temperature further than would be the case if the heat exchanger were not present. Cooling of the compressed gas to a lower temperature, in turn, enables a greater proportion of the water content to be condensed. On the other hand, the increased temperature of the downstream gas will result in a lesser degree of condensation during passage through the pipework and components of the utilising equipment since cooling of the gas will take place from a higher temperature than in the case where the heat exchanger is not present.

Moreover, the working efficiency of the compressed air is enhanced when the gas is at a higher temperature.

The cooler may be liquid or air-cooled. In one convenient embodiment, the cooler comprises an air-cooled radiator with a motor driven fan for creating a flow of cooling air. The motor may be an air motor connected to receive compressed air from the output side of the radiator.

In a preferred embodiment, means is provided for by-passing a proportion of the downstream air around the heat exchanger and subsequently recombining it with the downstream air which has passed through the heat exchanger. This enables the temperature of the air supply to the utilising equipment to be controlled, e.g., maintained at a preset temperature level. Such by-pass means conveniently includes a thermostatically controlled valve which opens and closes in dependence upon the temperature of the air supplied to the utilising equipment. Such an arrangement is particularly useful for supply of compressed air to breathing apparatus and for installations employing plastics pipelines and components which should not be subjected to temperatures above a certain level.Moreover, the preferred form of the apparatus can be used with different types of compressors without requiring special adaptation since the provision of the by-pass means enables the temperature of the output air to be regulated; for example when used with a compressor (such as a reciprocating type compressor) which produces compressed air at a relatively high temperature, a suitable proportion of the downstream air from the aftercooler can be by-passed around the heat exchanger in order to achieve a given temperature for the output air, when the compressor is of the screw-type, the proportions of by-pass air may be less since such compressors generally produce compressed air at lower temperatures than reciprocating compressors.

To promote further understanding of the invention, one embodiment will now be described by way of example only with reference to the accompanying drawings, the sole figure of which is a block diagrammatic view of the apparatus.

As shown, in common with conventional compressed air producing apparatus, a preferred form of apparatus according to the present invention comprises a compressor 10, an aftercooler 1 2 connected to the compressor 10 so as to cool the hot compressed air and thereby condense out a major proportion of its water content from the gaseous phase, and a separator 14 for removing water droplets (and depositirig the same via output 13) before the compressed air is applied to the utilising equipment 1 5. The aftercooler may be liquid or air-cooled and in the latter event it may for example comprise a radiator and fan means 1 6 driven by motor 18 for blowing or sucking ambient air through the radiator core.

In contrast with conventional apparatus, the aftercooler 12 is connected to the compressor 10 through the agency of a heat exchanger 20 and the air from the separator 1 4 is fed via line 22 to the heat exchanger 20 so that the "dried" air downstream of the aftercooler is brought into heat exchange relation with the air from the upstream side. Thus, instead of being supplied directly to the utilising equipment 15, the "dried" downstream air is first passed through the heat exchanger 20 and is then supplied to the utilising equipment via line 24.

In this way, the hot compressed air from the compressor 10 is subjected to a certain degree of cooling in the heat exchanger 20 by heat exchange with the cooler compressed air derived from the aftercooler 12 and the hot air therefore enters the aftercooler at a lower temperature than in conventional apparatus. The heat exchanger 20 may be of any conventional form suitable for achieving efficient heat exchange between hotter and cooler fluids. The motor 1 8 used to drive the fan 1 6 of the aftercooler may be an air motor and may be supplied with compressed air via line 26 on the downstream of the aftercooler.

The temperature of the compressed air produced by various forms of compressor (e.g.

reciprocating and screw-type compressors) can vary substantially from one type to another. To adapt the apparatus for use with different types of compressor, a by-pass line 28 may be incorporated whereby a proportion of the downstream air from line 22 can be by-passed around the heat exchanger 20 and used to control the temperature of the air fed via line 24.

The proportion of air by-passed in this manner is conveniently controlled by means of a thermostatically controlled valve 30 which may close and open to a degree governed by the temperature variations in line 24 so as to maintain the temperature of the air in line 24 substantially uniform at a pre-settable level. A mixer 32 may be provided to effect mixing of the "dried" downstream air which has passed through the heat exchanger 20 with air (if any) which has been by-passed via line 28.

From the foregoing, it will be seen that the apparatus of the present invention possesses important advantages over and above conventional compressed air conditioning apparatus. In particular, it will be noted that the advantages of the present invention are obtained without the need for any additional energy input.

Claims

1. Apparatus for conditioning compressed gas (e.g. air) to reduce its water content, the apparatus comprising a cooler for cooling the compressed gas so as to cause condensation of at least part of the water content thereof and means for removing condensed water droplets from the compressed gas, characterised in that the compressed gas is supplied to the cooler via a heat exchanger in which the compressed gas upstream of the cooler is in heat exchange relation with the compressed gas downstream of the cooler.

2. Apparatus as claimed in Claim 1 in which the cooler comprises an air-cooled radiator with a motor driven fan for creating a flow of cooling air.

3. Apparatus as claimed in Claim 2 in which the motor is an air motor connected to receive compressed air from the output side of the radiator

4. Apparatus as claimed in Claim 1,2 or 3 in which means is provided for by-passing a proportion of the downstream air around the heat exchanger and subsequently recombining it with the downstream air which has passed through the heat exchanger.

5. Apparatus as claimed in Claim 4 in which said by-pass means includes a thermostatically controlled valve which opens and closes in dependence upon the temperature of the air supplied to the utilising equipment.

6. Apparatus for conditioning compressed gas, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.