Brochure
19
Time
(minutes)
DDSDrying/RegenerationCycle
0 2.5 3
changeover
time
dictate
d
by
outlet
dewpoint
changeover
0 2.5 3
changeover
time
dictated
by
outlet
dewpoint
changeover
SideA Regeneration Re-pressurisation EnergySaving Drying
Side
B Drying Regeneration Re-pressurisation Energy
Saving
DDS operation
At column changeover, the exhaust valve is closed to allow the
purge air to re-pressurise the o-line column, thus ensuring no
loss of system pressure.
At this time, both drying chambers are at full line pressure, so
that no purge air is being used and the dryer is in a state of zero
energy consumption.
Under normal operation, the drying chambers would proceed
to change over automatically, however the DDS energy
management system incorporates a hygrometer which is used
to monitor the pressure dewpoint of the air leaving the dryer. If
the air is drier than the pre-set dewpoint, the desiccant material
is only partially saturated and has drying capacity remaining
within it, therefore change over is delayed.
e hygrometer constantly monitors the outlet dewpoint until
the pre-set level has been achieved, at which point, change over
will occur.
e drying and regenerating cycle will then continue normally
until the end of the next column changeover when the DDS
energy management system may again extend the drying period
as dictated by the outlet air quality.
Saving energy with the dewpoint dependent
switching (DDS) energy management system
The energy required to regenerate the off-line desiccant
bed in an absorption dryer is constant, and based upon the
assumption that the dryer is operating at its full capacity
and the desiccant bed requiring regeneration has been fully
saturated. In reality, a dryer is rarely operating at full capacity
all of the time, for example during shift work and periods
of low demand. Daily and seasonal fluctuations in ambient
temperature and humidity also change the moisture loading
placed upon the dryer.
Under such conditions, at the point in the drying cycle where
the air flow is switched from one drying chamber to the
other, there is the potential for drying capacity to remain in
the desiccant material about to undergo regeneration. As the
energy used to regenerate this partially saturated bed is based
upon the assumption that the bed is fully saturated, more
energy (purge air) is consumed than is actually necessary.
Dewpoint Dependent Switching (DDS) Energy Management System
With the DDS Energy Management system installed, the drying cycle remains unchanged, however as the drying chambers are
about to change, the DDS system overrides normal operation to fully utilise the drying capacity of the on-line desiccant material.
DDS Operation - Energy Saving Cycle (Heatless Dryer example shown)
System pressure 6 bar g. Max Temp 35°C. System ow 1700 m
3
/hr (1000 cfm). Average pressure 6.5 bar g. Average Temp 30°C.
100 33.00 95,040 50,371
90 40.00 115,200 61,056
80 47.00 135,360 71,741
70 53.00 152,640 80,899
60 60.00 172,800 91,584
50 66.00 190,080 100,742
AirDemand% EnergySaving%
EnergySaving
P/AKw
EnvironmentalSaving
P/AKgCO
2
DDS Energy Saving (Heatless Dryer example shown)