GB2398525A

GB2398525A - Compressed gas drying system

Info

Publication number: GB2398525A
Application number: GB0411748A
Authority: GB
Inventors: Andrew C Collins
Original assignee: Engineering & Design Services
Current assignee: Engineering & Design Services
Priority date: 2003-06-21
Filing date: 2004-05-24
Publication date: 2004-08-25
Also published as: GB0411748D0; GB0314520D0

Abstract

Gas/liquid separation apparatus for drying compressed gas of the type having two parallel separation vessels 5a,5b containing an adsorbent with one separation vessel being on-stream whilst the other is off-stream with its adsorbent being regenerated, characterised in that the regeneration is conducted by a low pressure gas which is separated from the condensate removed from the adsorbent without losing the gas. The gas to be dried may be stored in a header tank before being passed through the separation vessel stage and the dried gas may be passed through a particulate filter.

Description

1 2398525 COMPRESSED GAS DRYING & FILTERING SYSTEM The invention relates

to a gas / liquid separation apparatus for drying compressed gas of the type having two parallel separation vessels, each containing an absorbent, with one separation vessel being on-stream whilst the other is off- stream with its adsorbent being regenerated, characterised in that: The wet gas to be dried is stored in a header tank before being compressed and passed through the on-stream separation vessel.

À The off-stream separation vessel is regenerated by isolating it from the process flow of gas and reducing the pressure of the gas therein by purging the separation vessel of the trapped gas such that the adsorbed moisture becomes entrained in this gas as it is purged, condensing the moisture out of the purge gas by cooling the purge gas, collecting it separating it there from and feeding the dried gas back through the offstream separation vessel until all the adsorbed moisture has been removed so as to avoid loss of gas.

The drying and filtration package is located in the path of the high pressure gas from a compressor. The compressor increases the pressure of the gas taken from a wet gas suction header tank up stream to 350 bar g. The suction tank provides storage for a sufficient supply of gas from the mains feed to the site location. A coalescing filter down stream of the compressor, removes water droplets, aerosols and oil. Two separation vessels alternatively dry the compressed gas while the off-stream one is in regeneration. Dust and dirt introduced in to the gas flow from the earlier stages is removed by the particulate filter before the gas leaves the system.

The method of regenerating the off-stream separator vessel adsorbent material is preferred as there is no loss of gas, it makes use of a small portion of the main gas supply trapped in the regeneration loop at a reduced pressure thus saving gas and using low a pressure heater, heat exchanger and circulating booster. It will reduce cyclic fatigue compared to that of a heater-less system.

Description

Figure I shows the process in diagrammatic form.

Compressed gas enters the system from the compressor outlet in to a coalescing filter I where any condensate or aerosols are collected and removed from the system. The still saturated gas is directed to either of the separator vessels 5a or 5b by switching valves 2. Each separator vessel contains a desiccant material to adsorb the water vapour in the gas. Figure I shows the gas passing downward through one separator vessel 5a (the left) and then through a non-return valve 9 in to the particulate filter 19.

The now dry filtered gas is stored in high pressure vessels ready for use (not shown in this diagram).

Only one of the two separator vessels 5a or 5b at a time is used to separate the water vapour from the gas. The other (figure I shows the right) off stream separator vessel À À À . À À . . . . À À . À À 5b can be regenerated (removal of the previously adsorbed water). Inlet switching valve 2 to separator vessel Sb is closed isolating it from the incoming wet gas in readiness regeneration.

Switching valve 101inked to separator vessel Sb is opened to allow its pressure to be lowered through the pressure regulating valve 18 after which the gas is returned for re-use to the compressor suction tank. The gas in separator vessel Sb operates switch 6 when the pressure is low enough for regeneration to begin. A signal from switch 6 instructs switching valve 10 to close and separator vessel Sb regenerating valves 3 and 8 to open.

Gas booster 13, circulates the low pressure gas through the regeneration system. Gas from the outlet of the booster 13 is heated by a heater 12. Switching valves 8 directs the flow of hot gas in an upward direction through separator vessel Sb evaporating the adsorbed water and carrying it out through switching valves 3. The hot wet gas passes through a cooler 16 where it is chilled condensing the water vapour. Separator 1 S collects the condensate which is then removed from the system via drain valve 17.

The gas is then re-circulated by the booster 13. Temperature controller 4 monitors the heat of the gas leaving the separator vessel Sb. When the temperature at 4 is similar to the temperature at 11 the water will have been evaporated and the chamber can be allowed to cool. Cooling is by the same circulating system only the heater 12 is now switched off allowing cold gas to flow through separator vessel Sb.

Chamber Sb is returned to system pressure by closing switching valves 3 and 8 and opening valve 7. The above sequence is used to regenerate the separator vessels Sa and Sb alternately while one is always on stream. À À .

Claims

À À À À À . À À À À CLAIMS

1. A gas / liquid separation apparatus for drying compressed gas of the type having two parallel separation vessels containing an adsorbent material with one separation vessel being on-stream whilst the other is off-stream with its adsorbent being regenerated, characterised in that the regeneration is conducted by a lower pressure gas which is separated from the condensate removed from the adsorbent without loosing the gas.

2. A gas / liquid separation apparatus for drying compressed gas as claimed in Claim 1 where a method of reducing the gas pressure for regeneration is employed without loss of gas.

3. A gas / liquid separation apparatus for drying compressed gas as claimed in Claim 1 and Claim 2 where a method of regeneration is performed by re circulating trapped low pressure gas to transfer moisture evaporated from the adsorbent and condensed by a cooler, separated and drained.

4. A gas / liquid separation apparatus for drying compressed gas as claimed in Claim 3 where a method of evaporating the moisture previously adsorbed by the adsorbent material by heat transfer from the circulating trapped low pressure gas and then cooling and condensing the moisture for collection and removal by an automatic drain valve.