Brochure

4
Wet
Air
Wet Purge
Air to
Atmosphere
Desiccant
Bead
Desiccant
Bead
Dry Air
Dry Purge
Air
Time
(minutes)
StandardDrying/RegenerationCycle
0
2.5 3
changeover
0 2.5 3
SideA Regeneration
Re-pressurisation
Drying
SideB Drying Regeneration
Re-pressurisation
PNEUDRI - How It Works
Adsorption dryers work on the principle of moisture always
migrating to the driest medium possible. Therefore, water
vapour is removed from compressed air by passing it over
an adsorbent desiccant material.
As the air contacts the adsorbent material, water vapour
transfers from the wet air to the dry desiccant, however,
adsorbent materials have a fixed adsorption capacity and once
this capacity is reached, they must be regenerated or replaced.
Therefore, to provide a continuous supply of clean, dry
compressed air, adsorbent dryers utilise two chambers of
desiccant material and at any one time, whilst one chamber is
on-line, drying the incoming compressed air, the other is either
off-line, being regenerated or is re-pressurised, ready to come
on-line. All adsorption dryers remove water in this manner.
The energy consumed by an adsorption dryer can be directly
attributed to the method used to regenerate the adsorbent
material. Parker domnick hunter PNEUDRI dryers utilise either
the Heatless PSA or the Heat Regenerative TSA method to
regenerate the adsorbent material.
PNEUDRI Operation - Drying Cycle
The process air enters the dryer through the inlet and is
directed into the on-line drying chamber via the inlet valves
and lower manifold.
(PNEUDRI models can be made up of either single or multiple
drying columns, depending upon the range)
The air is evenly distributed through the drying columns and
passes over the desiccant material, reducing the water vapour
content.
The dried process air then combines in the upper manifold
and exits the dryer via the outlet check valves.
Column Changeover
Before the on-line (drying) and off -line
(regenerating) columns change over, the dryer
exhaust valve, is closed, allowing the purge air to
re-pressurise the off -line columns. This ensures a
consistent system pressure and dewpoint when the
drying chambers change over.
PNEUDRI Operation - Regeneration Cycle
(Heatless PSA or Pressure Swing Adsorption)
At the start of the regeneration cycle, the exhaust valve of the dryer is closed
and the off-line chamber is at full line pressure. The air in the off-line chamber
has a dewpoint equal to the air leaving the dryer.
The exhaust valve is then opened and the dry air within the chamber expands
rapidly as it leaves the dryer via the exhaust silencer, forcing water to be
removed from the desiccant material.
Once the off-line chamber has de-pressurised, a continuous bleed of dried
process air is directed into the off-line upper manifold. This air is known
as purge air.
With the exhaust valve open, the purge air expands from line pressure
to atmospheric pressure and flows downwards through the columns,
over the off-line desiccant material.
As the purge air at line pressure contains a fixed amount of water vapour,
allowing it to expand means the purge air becomes even drier, increasing
its capacity to remove water from the saturated desiccant bed.