A mode of filtration where
the fluid contacts the filter material at 90° C.
All the fluid must pass through the filter material
to reach the downstream side. Most cartridge filtration
works in this mode.
DEFORMABLE
Used to describe suspended
solids that extrude into the interstices of a filter
cake and cause rapid filter plugging.
DEGREE OF FILTRATION
A reusable filter consisting
of a tube made from ceramic or metal. Flow is from the
outside-in with particulate accumulating on the outside
of the candle. The candle can be cleaned by various
means, including back-pulsing, heats chemical, etc.
DEHYDRATION
Removal of water or hydrocarbon
in vapor form from an air or gas; also water from another
immiscible liquid.
DELTA P
A symbol (?p) designation
pressure drop. The difference in pressure between two
points, generally measured at the inlet and outlet point
of a filter, separator/ filter, etc.
DEPTH
A filter medium which primarily
retains contaminants with the tortous passages within
the thickness of the element wall.
DEPTH FILTRATION
A process that entraps
contaminants both within the matrix and on the surface
of the filter media.
DESALINATION
Production of fresh (potable)
water from sea water, salt or brackish water by one
of several processes, e.g., distillation, flash distillation,
electrodialysis or reverse osmosis if salt content is
not too high.
DEWATER
Removal of water from solids.
DEW POINT
The temperature at which
condensation begins to form as a gas is cooled.
DIFFERENTIAL PRESSURE (Delta
P)
The difference between
static pressure measured at the inlet and outlet of
a component device.
DIFFERENTIAL RATING
Differential pressure specified
as the maximum an element will withstand without structural
failure.
DIFFUSION
A natural phenomena of
gas passing through a liquid film in a membrane from
the high pressure to the low pressure side.
DIFFUSION INTERCEPTION
In gas filtration, at low
gas flow velocities, very small particles <0.1 µm
are subject to Brown motion. Thus they can move out
of the gas streamlines and become intercepted by the
filter.
DIMENSIONAL STABILITY
The ability of the fabric
to retain finished dimensions under stress at operating
conditions. This stability is imparted to a fabric by
chemical treatment, mechanical means, construction or
blends.
DIRECTION OF FLOW
Direction in which product
flows through element; may be from inside to outside,
from outside to inside, or end to end, depending on
the design of the element.
DIRECT INTERCEPTION
In gas filtration, particles
larger than the pores are removed by direct interception
with the filter surface. Some particles smaller than
pores can be removed as well depending on the probability,
which is proportional to their size, of hitting the
surface.
DIRT HOLDING CAPACITY
Volume of contaminate an
element can hold before reaching the maximum allowable
pressure drop. Volume will vary depending on the size
and design of the element and the density of the solid
particles. Usually reported by weight such as grams
or pounds per element. Also called solids retention
or solids holding capacity.
DISCONTINUOUS PHASE
Separated phase or product
from the continuous phase. Example: water maybe the
discontinuous phase when separated from hydrocarbon,
air or gas.
DISPOSABLE FILTER
Those filter not cleaned
or reused. Referred to as one-time of single-use filters.
DOWNSTREAM
Portion of the product
steam which has already passed through the system or
the portion of a system located after, separator/filter
etc.
DOWNSTREAM PROCESSING
Product recovery operations
after a primary production process such as fermentation.
DRAIN
A low level point valve
connection on a filter or system to allow drainage of
liquid.
DROPLET
Minute drop which mates
to form larger drops capable of falling by gravity.
DRY SCRUBBER
A chemical reaction chamber
that neutralizes acids in a gas stream. Two system types
are common: the spray dryer system injects a slurry,
whereas dry sorbent injection systems use a dry powder.
DUPLEX FILTER
Assembly of two filters
with valving for selection of either or both filters.
DUST (OR MIST) CONCENTRATION
The weight of dust or mist
contained in a unit of gas; e.g., pounds per thousand
pounds of gas, grains per actual cubic foot of gas or
grains per standard dry cubic foot (the temperature
and pressure of the gas must be specified if given as
volume).
DUSTCAKE
Desired dust buildup on
fabric to filter incoming gases and keep particulate
on fabric surface.
DUST LOADING
The weight of solid particulate
suspended in an air (gas) stream, usually expressed
in terms of grains per cubic foot, grams per cubic meter
or pounds per thousand pounds of gas.
DYNE
The amount of force that
causes a mass of one gram to alter its speed by one
centimeter per second for each second during which the
force acts.
