Deliquescent compressed air or natural gas dryer filtration: Why a coalescing filter downstream of dryer is important

Deliquescent dryers are a perfect solution for portable compressed air applications and point of use fuel gas applications. They are the ideal compressed air and gas treatment choice when low initial cost, ease of use, rugged handling and no electrical power is available on site.  These features offer a unique advantage over other dryer types.

What about filtration? Unlike other types of air and gas dryers, the desiccant media in deliquescent dryers is not fouled by oil being condensed or absorbed. The deliquescent desiccant does not adsorb oil vapor and it isn’t harmed by oil or hydrocarbon aerosols. Since there will be some cooling through the deliquescent desiccant bed, small amounts of oil aerosols can form just downstream of the dryer. For this reason, the use of a coalescing pre filter when treating compressed air with a deliquescent type dryer is often omitted. Instead, a coalescing filter with drain is highly recommended and used as an after filter.

Some customers like to minimize the risk of oil carryover by installing a coalescing pre filter and after filter. In this case, a 5 micron coarse coalescing filter is installed downstream of the compressed air after cooler / separator to make up for separator inefficiencies and a 1 micron general purpose coalescing filter is installed after the deliquescent dryer to assure removal of all oil aerosols. The added benefit of this installation is increased filter life and added protection for your application.

When drying fuel gas coming from a scrubber or separator the higher cost deliquescent desiccant used in gas applications is protected from liquids by a general purpose coalescing pre filter. After the gas passes through the dryer, coalescing filtering of hydrocarbon or oil aerosols may or may not be desired. A general purpose particulate filter should be installed after the dryer to protect downstream equipment from particulate damage in applications where a coalescing after filter is not elected.

Fuel Gas dryer with coalescing filters installed downstream

Correct selection and placement of filters is important for any air or gas drying application.  For more information on filter selection, we recommend that you download our F200 series catalog.