NOTE: Choose the following subparagraph or the
subparagraph entitled "Compressed Air Refrigerated
Air Dryer."
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2.7.3.1
Compressed Air Desiccant Air Dryer
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NOTE: The refrigerated air dryer is limited with an
atmospheric dew point of approximately minus 23
degrees C 10 degrees F equivalent to minus 12
degrees C plus 10 degrees F at 172 kPa (gage) 25 psig
and 2 degrees C 35 degrees F at 690 kPa (gage) 100
psig, and where this may be a problem the desiccant
air dryer should be used as a much lower dew point
can be attained.
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Provide for systems exposed to freezing temperatures [one] [two] compressed
air dual chamber type desiccant dryer[s] each of sufficient capacity for
each system listed below. Each dryer shall be equipped with an automatic
regeneration system which uses [steam heated dry air] [unheated dry air]
for the regenerative media. The capacity of each dryer shall be such that
compressed air, in the quantities listed below will be dried from a
saturated condition at [_____] degrees C F to a pressure dew point of minus
40 degrees C F.
Service
Capacity (Each Tower)
Baghouses
[_____] L/s at 862 kPa (gage)
Ash Handling
[_____] L/s at 862 kPa (gage)
[_____] L/s at 862 kPa (gage)
Service
Capacity (Each Tower)
Baghouses
[_____] cfm at 125 psig
Ash Handling
[_____] cfm at 125 psig
[_____] cfm at 125 psig
The contact time of the air in the chambers shall not be less than 4.5
seconds. Velocity of the air shall be less than that which will fluidize
the desiccant bed. Pressure drop through the unit when operating at rated
flow shall not exceed 27 kPa 4 psi. Units shall be field adjustable to
maintain the pressure dew point of the dried air at any preselected value
below operating temperature, to minus 40 degrees C F. Units shall have as
an integral part of the construction an indicator showing the water content
of the dry air and a calibrated adjustment control to change the water
content to any preselected level.
Desiccant dryers shall provide a
continuous supply of dry air by automatically cycling operation of the
desiccant beds.
a.
Chambers: Designed for 1034 kPa (gage) 150 psig working pressure
in accordance with the ASME BPVC SEC VIII, and so stamped. Each
chamber shall be fitted with separate fill and drain ports so that
inlet and outlet piping manifolds need not be removed to fill or
SECTION 15502N
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