Liquid-Liquid Coalescer Design Manual

THREE 20 Ft. Gravity Separator

PHASE
IN GAS OUT

LIQUID LEVEL

THREE GAS
PHASE IN OUT
60" ID

LIQUID LEVEL LIGHT

36" ID

PHASE
OUT
16"

LIGHT
PHASE
INTERFACE OUT
30"

LEVEL

HEAVY
PHASE
12 Ft. Coalescer Vessel OUT

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 LIQUID-LIQUID COALESCER DESIGN MANUAL
Table of Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Stokes Settling — Using Gravity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Basic Design Concepts — The Emulsion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2
Basic Design Concepts — Operating Principles of a Coalescer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
Basis for Sizing and Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
Intra-Media Stokes Settling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
Direct Interception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
Gravity Separation Downstream of a Coalescer Element . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
Coalescer Configurations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Case Studies
-Oil-Water Separators - Environmental Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
-Gas Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
-Alkylation Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
-Oil/Water Separator on a Production Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
-Upgrading a Three-Phase Separator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
General References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Ranges of Application for Coalescing Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

ACS Oil / Water Separators utilize patented* technology to separate oily waste water.
Applications include oil spill clean up for marine, power plants, refineries, vehicle terminals, and
countless others. The separated water is purified for
direct sewer or ocean discharge. The oil is captured
1992 Vaaler Award
for ACS Industries and recycled.
Oil-Water Separator
*US Patent Nos. 5,023,002 & 5,246,592

20’L x 8’W x 9’-6"H

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Introduction flowing and the opposing forces of buoyancy and vis-
Whether engineering a new coalescer vessel, or cous drag balance (Figure 1), the droplet has achieved
debottlenecking an existing separator, full knowledge its Terminal Settling Velocity. This vertical velocity is
and understanding of the basic principles involved are constant because there are no net forces acting upon
required. Often overlooked are the capabilities of prop- the droplet. This mechanism of separating liquids by
erly selected and designed internals for the enhance- gravity is called Stokes Settling after the nineteenth
ment of simple gravity separation. This Liquid-Liquid century English researcher Sir George Stokes.
Coalescer Design Manual describes the use of various The equation he developed for the terminal settling
media and methods employed for decades to increase velocity is still used today:
plant productivity. Typical applications include:
• Removal of Bottlenecks in existing vt = 1.78 X 10-6 (∆S.G.) (d)2 / µ (1)
Decanters and Three Phase Separators.
vt = Terminal Settling Velocity, ft/s
• Reduction in New Vessel Sizes – Up to five
d = Droplet Diameter, microns
times relative to gravity settling alone.
∆S.G. = Specific Gravity Difference
• Improvements in Product Purity – Carry-over
between the Continuous
entrainment reduced to 1 ppm and less.
and Dispersed Phases
• Compliance with Environmental Regulations –
µ = Continuous Phase Viscosity, centipoise
Cost effective solutions to wastewater
treatment and oil spill cleanups.
When two liquids are immiscible, or non-soluble in The size of a gravity decanter is derived from 1) the
one another, they can form either an emulsion or a terminal settling velocity of a minimum sized droplet
colloidal suspension. In either of these mixtures, the and 2) the inertial force imparted to the droplet due to
dispersed liquid forms droplets in the continuous the velocity of the emulsion through the vessel. At
phase. In a suspension, the droplets are less than one these conditions, all droplets larger than a minimum
micron in diameter and the liquids cannot readily be will be removed at a quicker rate and hence need not
separated with the technologies described here. be considered. The minimum sized droplet must be
Fortunately, in the chemical and hydrocarbon process estimated if empirical data is not available. Typically
industries droplet sizes are typically greater than this the minimum droplet size is estimated to be between
and/or the purities required can be achieved without 75 to 300µm. For example, API Publication 421 uses
addressing the ultra-light colloidal component of the minimum sized droplets of 150µm for oil/water sys-
stream. tems in refineries. Note that in Stokes Settling the
vessel must be sized to ensure laminar or streamline
Stokes Settling – Using Gravity flow; turbulent flow causes remixing. An example of
Traditionally, gravity separators were used to handle this sizing method in a decanter is contained in Case
emulsions before the use of coalescing media became Study 2, see page 12.
FIGURE 1 commonplace. In this
equipment, differences in In order to settle fine droplets and ensure laminar flow,
Forces on a light droplet densities of the two liquids large vessels and long residence times are required.
dispersed in a heavy liquid cause droplets to rise or It may take five, ten, and or even thirty minutes to
Bouyant Force fall by their buoyancy. The make a separation, depending on the physical prop-
greater the difference in erties of the stream. With the capacity intensification
densities, the easier the forced on modern refineries and chemical plants and
Inertial Force
separation becomes. achieved with advanced mass transfer internals, cat-
d
Rising (or falling) droplets alysts, and heat exchanger designs, operators find
are slowed by frictional that their separators only have half or a third of the
forces from viscous effects time originally anticipated. This results in hazy, off
of the opposing liquid. spec products or intermediates that cause problems
Viscous Drag
Force When the stream is not in downstream equipment.

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With Coalescer Media and Internals, unit perform- FIGURE 2
ance can be restored. Typical applications include:
VOLUME FRACTION FREQUENCY DISTRIBUTIONS
• Upgrading 3-Phase Separators FOR DISPERSIONS OF VARIOUS MATURITIES
and Decanters
• Removing haze from finished
products such as diesel and jet fuel
• Oil/Water Separators
• Solvent recovery from liquid/liquid
extraction towers

Basic Design Concepts

The Emulsion
In selecting and designing a coalescer, it is important
to understand and characterize the emulsion that has
to be treated. The finer the droplets dispersed in an
emulsion, the more stable it is, because the buoyancy
force diminishes in magnitude as the diameter
decreases. The manner in which the mixture is created Generating distributions can be done by collecting and
effects the droplet size distribution. For instance, plotting empirical data. Alternately, Mugele and Evans
centrifugal pumps shear liquid droplets much more (see General References) showed they have a reliable
severely than progressive cavity, thereby creating finer method for modeling this data as a function of standard
droplets. It is also important for the designer to know deviations that requires only knowledge of the maximum
how much time has elapsed since the mixing/shearing droplet diameter and two different values of the mean.
occurred. This is because as time goes on, smaller In the typical interconnecting piping between a con-
droplets aggregate (or coalesce) and larger droplets denser and a two or three phase separator; from a
are more likely to have joined a separate layer so that centrifugal pump and a distillation column feed
they are no longer considered to be entrained. coalescer; etc., a dispersion develops to where the
An important tool to quantify an emulsion is the Droplet Sauter (volume/ area) mean is roughly 0.3 and the
Size Distribution Curve generated by plotting the droplet mass (volume/ diameter) mean is roughly 0.4 of the max-
diameters against the volume or mass fraction at that dif- imum diameter, respectively.
ferential diameter. As stated above, the shape of the dis- A coalescer is often needed, though, for mature distri-
tribution is affected by the manner in which the emulsion butions (when the mean will be larger than a Gaussian
was formed, and its age. Consider a stream with a fine 0.5 of the maximum diameter). Examples are the dis-
emulsion (or immature dispersion) as in Figure 2. persion of produced water in crude oil that has traveled
Overtime, the peak of the volume fraction curve shifts to for weeks in a tanker and the water that has settled in
greater droplet diameters – until there are more large a product storage tank over several days. Therefore,
droplets than fines. with minimal data, an experienced designer can have
an accurate idea of the dispersion that a coalescer
Another key characteristic of an emulsion and the dis- must treat.
tribution that describes it is the existence of a Maximum
Droplet Diameter (1000µm in Figure 2). The maximum When the average droplet is greater than roughly 1/2 mil-
stable droplet size that an emulsion will develop in a limeter (500 microns), an open gravity settler is appropri-
given situation depends on the mechanism of their cre- ate. Table 1 shows some typical sources that can generate
ation, the amount of energy imparted to the mixture, dispersions that require the use of liquid-liquid coalescers.
and the interfacial tension between the phases. Also given are some characteristics of the emulsions that
Droplets larger than the maximum quickly leave the are created.
dispersed phase to form a separate liquid layer and
therefore need not be considered part of the emulsion.

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 Source Stability Droplet Size Step 1 – Droplet Capture
Range The first step of coalescing is to collect entrained
droplets primarily either by Intra-Media Stokes Settling
Flash Drum Emulsions Weak 100-1000 microns or Direct Interception. Figure 4 gives the useful zones of
with >5 % Dispersed Phase, separation for various mechanisms. Elements that
Static Mixers
FIGURE 4
Flash Drum Emulsions with
<5 % Dispersed Phase, ZONES WHERE DIFFERENT
Moderate 50-400 microns COALESCING MECHANISMS APPLY
Impellor Mixers, Extraction 1000
Columns

Centrifugal Pump Discharges, 100

Target Size, Microns

Caustic Wash Drums, Low Strong 10-200 microns
Interfacial Tension Emulsions 10

Haze from Condensing in Bulk

1
Liquid Phases, Surfactants
Very Strong 0.1-25 microns
Giving Emulsions With Very
Low Interfacial Tensions 0.1
Table 1 0.1 1 10 100 1000

Basic Design Concepts Droplet Size, Microns

Operating Principles of a Coalescer depend on Intra-Media Stokes Settling confine the dis-
Liquid-Liquid Coalescers are used to accelerate the tance a droplet can rise or fall between parallel plates
merging of many droplets to form a lesser number of or crimps of packing sheets (Figure 5). This is com-
droplets, but with a greater diameter. This increases pared to simple gravity separators in which the travel-
the buoyant forces in the Stokes Law equation. Settling
of the larger droplets downstream of the coalescer FIGURE 5
element then requires considerably less residence OIL DROPLETS RISING TO A COLLECTION SURFACE
time. Coalescers exhibit a three-step method of opera-
tion as depicted in Figure 3. L

FIGURE 3 h
THREE STEPS IN COALESCING
Submicron droplets
flow around target Several captured droplets
coalesce, forming larger ing distance is equal to the entire height of the pool of
Droplets strike drops...
target and adhere
liquid present in the separator. This effect is also seen
...which trickle down in knitted wire mesh, but their high void fractions mean
and fall, becoming
separated the surface is very discontinuous.
Meshes, co-knits of wire and yarns; and wire and glass
wools all depend primarily on Direct Interception
where a multiplicity of fine wires or filaments collect
fine droplets as they travel in the laminar flow stream-
lines around them (Figure 6). As can be see in Figure
4, in general they can capture smaller droplets than
1) Collection of Individual Droplets those that depend on enhanced Stokes Settling. A
2) Combining of Several Small Droplets into Larger Ones general rule with Direct Interception is that the size of
3) Rise/Fall of the Enlarged Droplets by Gravity the target should be close to the average sized droplet
in the dispersion. Finer coalescing media allow for the

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 FIGURE 6 been retained. Whether a coalescer medium is
hydrophilic (likes water) or oleophilic (likes oil) depends
DROPLET INTERCEPTION Liquid Flow on the solid/liquid interfacial tension between it and the
Streamlines
d Droplet Trajectory dispersed phase. In general an organic dispersed
DROPLET
phase ‘wets’ organic (that is plastic or polymeric)
Area for efficient Filament d/2
media, as there is a relatively strong attraction between
droplet collection D d/2 the two, while an aqueous dispersed phase preferably
DROPLET
d Droplet Trajectory
‘wets’ inorganic media, such as metals or glass. This
aids in the coalescence step as the droplets adhere to
the media longer. Also assisting coalescing is the den-
separation of finer or more stable emulsions (Table 2). sity of media: lower porosities yield more sites available
Note that fine media will also capture or filter fine solid for coalescing. In the case of yarns and wools, capillary
particulates from the process stream. Therefore, unless forces are also important for retaining droplets.
the emulsion is very clean, an upstream duplex strainer
Once several droplets are collected on a plate, wire, or
or filter is needed to protect a high efficiency coalescer.
fiber, they will tend to combine in order to minimize their
interfacial energy. Predicting how rapidly this
Media Source Max Droplet Flow Range will occur without pilot testing is very difficult to
Diameter, µ gpm/ft2 do. Judgments of the proper volume, and
Corrugated Separators with 15-75 therefore residence time, in the coalescers
Sheets Coarse Emulsions 40-1000 (35-180 m3/hr/m2) are guided by experience and the following
& Static Mixers properties:
Overhead Drums, 7.5-45
Wire Mesh, Extraction Columns,
Wire Wool Distillation Tower Feeds, 20-300 (20-110 m3/hr/m2) Coalescing Media:
Impeller Mixers • Media/Dispersed Phase
Co-Knits of Steam Stripper Bottoms,
Caustic Wash Drums, 7.5-45
Interfacial Tension
Wire & 10-200 3/hr/m2) • Porosity
High Pressure Drop (20-110 m
Polymer Mixing Valves • Capillarity
Glass Mat, Haze from Cooling in
Co-Knits of Bulk Liquid Phase, 7.5-45
Wire & Surfactants Giving 1-25 Liquid Phases:
(20-110 m3/hr/m2)
Fiberglass Emulsions with Very • Continuous/Dispersed
Low Interfacial Tension Interfacial Tension
Media Hydro/Oleophilic Porosity Target Size Fouling/Cost • Continuous/Dispersed
Density Difference
Metal/Plastic H/O 98-99% 3/8" - 1" Low/Low
Corrugated Sheets Spacing/Crimps • Continuous Phase Viscosity
Wire/Plastic Mesh H/O 95-99% .002" - .011" • Superficial Velocity
Wire Wool H
Wire/Polymer O 94-98% 21-35 micron Coalescers work better in laminar flow for sev-
Co-Knits
eral reasons. First, as mentioned above,
Wire/FG Co-Knits, H 92-96% 8 - 10 micron High/High droplets will stay in the streamlines around a
Glass Mat
wire or fiber target. Second, high fluid velocities
Table 2 overcome surface tension forces and strip
Step 2 – Droplet Coalescence droplets out of the coalescer medium. This results in re-
The second step is to combine, aggregate, or coa- entrainment in co-current flow and prevents droplets
lesce captured droplets. Increasing the tendency for from rising/sinking in counter-current flow. Lastly, slow-
droplets to adhere to a medium, increases the proba- er velocities result in greater residence time in the
bility that subsequent droplets will have the opportuni- media and therefore more time for droplet-to-target
ty to strike and coalesce with those that already have impact, droplet-to-droplet collisions, and Intra-Media
Stokes Settling.
Table 3
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The guidelines in Table 2 are used for selecting the taking into account the effects of any particulates or
proper coalescer for a given source based on the surfactants present. ACS has several of these available,
both as hand-held batch testers and continuous units
media’s Droplet Collection ability. Also given are typical
flow ranges for each type of coalescer media. ºgle, double, or triple coalescer stages (Figure 7). This
allows a coalescer system to be developed that is
Step 3 – Stokes Settling With Coalesced Droplets optimized for its removal efficiency, on-stream time,
The third step is the Stokes Settling of the coalesced and cost effectiveness.
droplets downstream of the medium. The degree of
FIGURE 7
separation primarily depends upon the geometry of the
vessel and its ability to take advantage of the large
coalesced droplets that were created through steps
one and two as described above. PILOT FILTER AND COALESCER

Basis for Sizing and Selection

A preliminary procedure for determining how difficult it
is to separate two immiscible liquids involves the per-
formance of a simple field test. A representative sam-
ple of the emulsion is taken from a process pipeline or
vessel. It is either put it in a graduated cylinder in the
lab or, if it is under pressure, in a clear flow-through
sample tube with isolation valves. The time required to
observe a clean break between phases is noted. If the
continuous phase has a viscosity less than 3 cen-
tipoise, then Stokes Law says the following:
Separation Emulsion Droplet Size,
Time Stability Microns
< 1 minute Very Weak >500
< 10 minutes Weak 100-500
For liquid-liquid coalescers, as with any process equip-
Hours Moderate 40-100
ment, successful sizing and selection is always a
Days Strong 1-40 combination of empirical observation/experience and
Weeks Very Strong <1 (Colloidal) analytical modeling. Of the three steps in coalescing –
droplet capture, combining of the collected droplets,
Fortunately, the experienced designer with knowledge and gravity separation of the enlarged droplets – the
of the application, equipment, and physical properties first and the last can be modeled with good accuracy
can often estimate the strength of the emulsion and and repeatability. The modeling of the middle and the
determine which medium will be successful. A more actual coalescing step is a complex function of surface
definitive approach, and one that is often needed to tension and viscous effects, droplet momentum, and
provide a process warranty, is the use of an on-site the dynamics of the sizes of the droplets in the disper-
pilot unit. sion. This has been done successfully in porous
media, but is beyond the scope of this brochure.
Liquid-liquid coalescer performance is often rated in
parts per million of dispersed phase allowable in the Droplet capture, the first step in liquid-liquid coalesc-
continuous phase effluent. Even trace amounts of con- ing, is the most important. The next two sections
taminants such as emulsifiers and chemical stabilizers describe the formulas used for the collection mecha-
can have dramatic effects on results at these levels. In nisms of Intra-Media Stokes Settling and Direct
a pilot program, several alternate media are provided Interception.
to the customer so that their performance can be
documented on the actual process stream, thereby

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Intra-Media Stokes Settling VC = (C1) Q h µ (2)
In a horizontal 3-phase separator, in order for effi- (∆S.G.) d2
cient separation to take place, droplets of some min- Where
imum size which exist in both the gas and the liquid
phases must be captured within the equipment. VC = Coalescer volume, cubic feet
When coalescing media is installed in the lower segment C1 = 164 for Plate-Pak w/horizontal sheets
of the vessel, the furthest a droplet has to travel is 219 for STOKES-PAK w/horizontal sheets
from plate to plate or sheet to sheet, rather than 312 for STOKES-PAK w/vertical sheets
down from the liquid level to interface level and/or up
from the vessel wall to the interface level (depending Q = Liquid/liquid emulsion flow, US GPM
whether the dispersed phase is heavier or lighter h = Corrugated plate spacing or structured
than the continuous phase). packing crimp height, inches
ACS offers a number of Corrugated Plate Interceptors d = Minimum droplet diameter, microns
(CPI) to enhance coalescence, such as Plate-Pak™ and
STOKES-PAK™ crimped sheet packing (Figure 8). µ = Continuous phase viscosity, centipoise
FIGURE 8 Plate-Pak is the most efficient CPI and thus has the
smallest C1. The reason for this is that the height, h, a
COALESCING MEDIA THAT droplet must traverse before hitting a solid surface is
DEPENDS ON STOKES SETTLING minimized in this construction (see Figure 9 a-c).
FIGURE 9
Operating by enhanced gravity
settling, Plate-Pak ™ vanes DISTANCE BETWEEN PLATES IN
are especially effective VARIOUS STOKES-PAK COALESCERS
for removing larger 9a Plate-Pak™ corrugations perpendicular to the flow
droplets.
Oil Droplets
h=

Clear liquid Emulsion

Plate-Pak ™
Axis of Corrugation

9b Axis of Corrugation
Stokes-Pak™ with
Horizontal Sheets
h 1/2"

Axis of Corrugation
Stokes-Pak ™
9c
Stokes-Pak™ with
They make more efficient use of a vessel volume than Vertical Sheets
a straight PPI (Parallel Plate Interceptor) since more
metal is used and the specific surface area is greater.
It can be shown from Equation 1 for Vt that the volume
of media necessary to remove virtually all droplets h

1/2"
equal to a minimum, typically 30-60 microns, is given
by:

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In order to decrease solid retention the axis of the cor- can be found by trial-and-error substitution of the terminal
rugations of Plate-Pak should be parallel to the flow. settling velocity from Equation 1 into Equation 3 below
However, vessel geometry often necessitates that the
corrugations be perpendicular to the flow, especially in
η
s = (vt/h)/ (vs/L) = .999
(3)
round vessels. Due to its light, self-supporting struc- where
ture and ease of installation, the overall project cost is s = η
Fractional Collection Efficiency
normally less for STOKES-PAK than Plate-Pak when by Stokes Settling
vs = Superficial Velocity
FIGURE 10 L = Element Length
vt/h = Droplet Rise Time
GAS OUT
vs/L= Droplet Residence Time
OIL OUT In horizontal flow when this length is over four ele-
ADJUSTABLE
ADJUSTABLE OIL WEIR FLOW
ments, ~32" (813 mm), the coalescer is usually split in
WEIR OIL DISTRIBUTION
BAFFLE
two or more beds with intermediate spacers or spacer
rings. Also, cross-flow designs are often used in this
WATER WASTEWATER
situation to allow for more frequent removal of the
OUT INLET collected dispersed phase.

Direct Interception
SOLIDS Direct Interception occurs when a droplet follows a
DRAIN
streamline around a target but collides with it because
SOLIDS
DRAIN
the approach distance is less than half its diameter,
d/2 (Figure 6). The formulas for Direct Interception in
mesh, co-knits, wire and glass wools are given below.
they both have sheets in the horizontal. STOKES-PAK Given first is a formula for the collection of a droplet on
with vertical sheets, on the other hand, retains fewer a single target. Following that is a formula which,
solids than the horizontal sheet version and so is often based on this factor, calculates the depth of the coa-
required in fouling situations. In this case, there is lescer element necessary to achieve a desired overall
some loss in coalescer efficiency due to the longer dis- collection efficiency at a selected minimum droplet
tance a droplet could travel (see Figure 9 b and c). The size.
entire CPI unit can also be put on a 45˚ to 60˚ angle in
order to retard fouling. However, this requires much (4)
more support structure and an additional 40 to 100%
of coalescer volume since droplet trajectory is length-
ened (Figure 10).

Equation 2 incorporates empirical factors that increase

η
the coalescer design volume over the theoretical in
order to compensate for the effects of bypass and D =Collection Efficiency of a Single
back mixing. With knowledge of the cross-sectional Target by Direct Interception
area of a fully flooded coalescer vessel or the lower
segment available in a horizontal 3-phase separator, E =Effective Length Multiplier
the required depth can easily be calculated from Vc.
ACS Plate-Pak and Stokes-Pak both come in units α =Volume Fraction of Fibers or Wires
which are 8" (203 mm) deep as a standard, but custom
depths are also available. d =Droplet Diameter, inches
Once the final coalescer length is selected the minimum
droplet size that can be collected at 99.9% efficiency K =Kuwabara’s Hydrodynamic Factor
-0.5 ln α -0.25 α2 + α -0.75

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The formulas for Direct Interception have no velocity
term in them, but to allow coalescence to take place (5)
designs are normally done for the middle of the flow
ranges given in Table 2. K, the Kuwabara
Hydrodynamic Factor, above is a correction to the col-
lection efficiency term that assumes a laminar/viscous
flow field. The effective length multiplier, E, is an ∑ = Overall Collection Efficiency by Direct Interception
empirical factor that takes into account the uneven dis- L = Element length required for removal of all droplets
tribution of curved and crinkled targets in a wool medi- > a minimum size at a ∑ = .999, inches
um and/or the shielding effects of the loops of knitted
mesh and twists of adjacent filaments in a strand of
yarn. The idealized layout of fiber targets where E=1 in As can be seen in Figure 4, there are two broad cate-
a coalescer is shown in Figure 11, while what actually gories of Interceptor-Pak™Coalescers that depend in
exists in a co-knit is shown in Figure 12. The finer the fil- Direct Interception, those that are made with fine wires
ament or wire the more the nesting/shielding effect and and those that are made with fine fibers. The factors to
the lower the value of E.
Application Min. Droplet
Diameter
Coalescer D E
microns/in.
FIGURE 11 microns
INTERCEPTOR LAYOUT IN AN IDEAL COALESCER Wastewater Fiberglass Mat 0.037 .04
4.5 Fiberglass Co-Knit 8.9/0.00035 0.027 .02
Sheen Interceptor-PakTM

Ordered FLOW S
Targets
Caustic Teflon
11.0 Co-Knit 21/0.00083 0.019 .07
Wash Drums Interceptor-PakTM
D

Impeller Polyester
12.5 Co-Knit 24/0.00095 0.021 .07
Mixers Interceptor-PakTM
FIGURE 12
Mixing Wire
22.0 Wool 50/.002 0.028 .40
Valves
Interceptor-PakTM

Extraction Knitted
79.0 Mesh 152/.006 0.014 .60
Columns Interceptor-PakTM
Table 3

be used in the formulas above for these media, the

appropriate minimum droplet size to use; and the
CO-KNIT MESH COALESCER THAT applications where they have found success are given
DEPENDS ON DIRECT INTERCEPTION in Table 3. In wire-yarn co-knits the wire occupies as
much as a third of the volume fraction as the yarn, but
As with CPI coalescers, sizing of a liquid-liquid coalescer exhibits only a few percent of the surface area.
that operates primarily on Direct Interception also corre- Therefore, for the sake of conservatism, the constants
lates well to an Overall Collection Efficiency of 99.9% of given in the table do not take into account either factor.
a minimum droplet size. Once this droplet size, empiri-
cally found to be approximately half the target diameter, The equations for droplet collection above can also be
is substituted into Equation 4, the length, L, required for used to derive the dispersed phase’s concentration in
a clean break can be predicted as follows. the effluent stream. First, a measured distribution or
the curve estimated with Mugele’s droplet size distri-

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bution equations is broken up into a large number of mium. The coalescer is located downstream of the
discrete diameter ranges. The fractional collection interface so that entrained continuous phase is
efficiency is then calculated at the mid-point of the removed from the dispersed. Lieberman (see General
range using either equation 3 or 5 (rewritten to be References) recommends that the liquid loading in a
explicit in ∑) thereby deriving the volume of dispersed vertical wash tower be limited to at most 1.6 ft/min of
phase that penetrates at that diameter. The effluent the dispersed phase. With the installation of a coa-
curve is then plotted. The area under both curves is lescer this can safely be increased to 2 ft/min (15
found with the influent normalized to 1 (Figure 13). gpm/ft2) thereby decreasing the cross-sectional area of
With knowledge of the influent dispersed phase con- the column by 20 to 40%.
centration, the effluent level is found by multiplying by In pressure vessels with full diameter coalescers such
the ratio of these areas. as those shown in Figures 14B and 14C, it is important
economically to keep the L/D ratio in the range of 3 to
FIGURE 13 5. It is typical and desirable that coalesced droplets
emerge from media that operates either on Intra-
Media Stokes Settling or Direct Interception at a size
of from 500 to 1,000 microns. The vessel length nec-
essary for inlet distribution devices upstream of the
Volume Fraction per Micron

media (such as sparger pipes, ‘picket fences’, and per-

forated plates used to assure uniform flow through the
media as in Figures 14B and 14C) and the depth of the
typical coalescer element itself with supports is typi-
cally 1 to 1.5 D. In order to keep the vessel’s aspect
ratio in the economical range, assuming an average
750-micron droplet emerging from the coalescer, the
axial velocity of the two liquid phases should be
limited to:
UMax = 0.78 |∆ ρ|
Droplet Diameter, microns
(6)
µ
Gravity Separation Downstream Where
of a Coalescer Element
Successful gravity separation downstream of a coa- UMax =Emulsion velocity, feet/minute
lescer element depends primarily on vessel geometry.
Various schemes are used with horizontal vessels
|∆ρ| =Absolute value of the difference
depending on whether there is a significant amount of between the densities of the
gas present as with Three-Phase Separators (Fig. 14A) continuous and dispersed
and/or the volume percent of the dispersed phase. The phase, pounds/cubic feet
formation of a wedge between a coalescer and a sharp µ =Continuous phase viscosity,
interface level as seen in Fig. 14B is well documented. centipoise
A boot is desirable when the amount of dispersed phase
is <15% v/v (Fig. 14C) where the control of the interface The successful design of a liquid-liquid coalescer starts
level is linear with the volume of dispersed phase dis- with knowledge of the source of the emulsion and the
charged. A dispersed phase velocity of 10 inches (254 stream’s physical properties. It has been shown that a
mm)/minute is desirable to allow disengagement of the combination of empirical experience and analytical
continuous phase, while keeping the boot diameter modeling of available coalescing media based on
<40% of the diameter of the horizontal portion to mini- removal of 99.9% of a minimum droplet size can then
mize the necessity for weld pads. The most common be used to predict allowable entrainment concentrations
applications for coalescers in vertical flow are in the effluent stream. Once the coalescer is properly
extraction/liquid-liquid absorption towers (Fig. 14D) located in an existing or new vessel a project that has a
and entrainment knockout installations (Fig. 14E) high rate of return is achieved that gives many years of
where the available plot plans in the plant are at a pre- reliable service.

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 COALESCER FIGIRE 14 D

Configurations Vertical Extraction Column with Coalescer

Light Stream Out

Vertical Coalescers
Coalescer

Heavy
Horizontal Coalescers Stream
In

FIGIRE 14 A
Trays,
3-Phase Horizontal Coalescer Vessel Packing
Mixed or Agitated
Vapor Internals
Phase Plate-Pak™ Outlet
Inlet Inlet Device Mist Eliminator

Vapor & Mist Flow

Light
Collected Mist Drain Stream
In
Liquid Flow
Hydrocarbon
Two
Liquid Hydrocarbon
Aqueous
Phases
Heavy Stream Out
Aqueous Hydrocarbon
Coalescer Outlet Outlet

FIGIRE 14 E
FIGIRE 14 B
Vertical Decanter with Coalescer
2-Phase Horizontal Coalescer Vessel
Emulsion In Wedge Light Product

LC Light
Stream
Out
Coalescer
Liquid Coalescing Heavy
Distributor Medium Product

FIGIRE 14 C
Emulsion
2-Phase Horizontal Coalescer Vessel with Boot In
Emulsion In Light Product

Heavy Stream Out

Coalescing Heavy
LC
Medium Dispersed
Phase

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CASE STUDY #1 Interceptor-Pak™ Co-Knit coalescing media were
Oil-Water Separators — Environmental Response used. Their efficiency was maintained despite the
The Oil-Water Separators (OWS) developed by ACS to presence of the highly viscous oil by cleaning both of
handle accidental offshore spills have three stages of them with diesel oil which was injected at an amount
coalescing, one using Stokes Settling and two using equal to only 0.5% by weight of the amount of oil antic-
Direct Interception. It can, therefore, serve as an exam- ipated to be collected. This media works on Direct
ple of how to apply all the equations for droplet coa- Interception so equations 4 and 5 are used. Media
lescing given above. After the Exxon-Valdez incident the properties are given in Table 3. First Kuwabara’s
US government was looking to set up a quick response Hydrodynamic Factor is calculated as follows.
system with ship-board equipment to skim potential K= -0.5 ln .027 - 0.25(.027)2 + (.027) - 0.75
large spills of crude oil that on the frigid ocean waters
congeals to a viscosity of up to 50,000 centistokes, sep- = 1.083
arate out all contaminants on board, and return the sea
water with less than the EPA mandated 10 ppm hydro- According to Table 3 fiberglass co-knit can remove
carbons present. The Marine Spill Response 99.9% of all droplets 4.5 microns and larger.
Corporation (MSRC) was set-up for this purpose with 16 Therefore
locations in all major US ports including Puerto Rico,
Hawaii, and Guam. ACS engineers quickly developed,
ηD = 0.02 (1-.027)(4.5/8.9) 2

1.083 (1+(4.5/8.9))
tested, and proved to MSRC the viability of the 525-gpm
OWS system shown in Figure 15 below, two of which = 0.00305
were installed on each quick-response vessel. ACS was
awarded the prestigious Vaaler Award and two US L = π (.00035") (1-.027)ln (1-.999)
patents (Nos. 5,023,002 and 5,246,592) in developing -4(0.00305) 0.027
the coalescers for this application.
Typical conditions are – removing 25 gpm of oil with a = 22.4"
specific gravity of 0.85, and a viscosity of 12,000 centis- For safety each stage was supplied with a
tokes from 500 gpm of water with 3% salinity, a specific 24" thick fiberglass co-knit element.
gravity of 1.02, and a viscosity of 1 centistoke. The over-
all dimensions of the OWS for the MSRC are 8’ square
by 25’ long at a full of water weight of 25,000 lbs.
FIGURE 15
CPI media, such as ACS Plate-Pak™ which in this case
had 3/4" plate spacing to accommodate the highly vis- ADVANCED OIL/WATER SEPARATOR
cous oil, is known to be able to remove 99+% of all
droplets down to about 100 microns. Oil
Putting these factors into equation 2 yields –

Vc = 164 (525) 0.75(1.02)

0.17 (1002) Advanced
Dual Capacitance
Pre-Filters LC Probes LC
= 38.0 cubic feet
The Plate-Pak was designed for 25gpm/ft2, requiring
21 square feet (installed at 7 feet wide X 3 feet high to Oily Water
water
accommodate the design shown in Figure 15 and the drawn in FC

shipping dimensions given above). Therefore, the by suction

required depth is 38.0 cubic feet/21 square feet, or

Solvent Solvent
1.81 feet. This was rounded up to two feet for safety. Injection Injection

In order to meet stringent EPA regulations for dis-

charging wastewater overboard, two stages of ACS

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CASE STUDY #2 viscosity of 7.2 cp. A quick design for a gravity separator
Coalescers in Gas Plants can be done with equation 2 if the maximum height that
A major South American engineering company was a 30-micron glycol droplet would have to fall from the liq-
designing a 100 MMSCFD natural gas plant that used uid level to the boot at the bottom of the vessel is used as
ethylene glycol (EG) for dehydration and for inhibiting if it was the CPI coalescer’s h. In this case 42" was
hydrate formation. There is a horizontal Three Phase assumed for a 60" ID vessel. Thus
Cold Separator with a boot in this process that does mist V= 162(45) 42 (.11)
elimination in the free board above a large liquid hold-up (.818-.496)302
section that extends the length of the vessel. The latter
volume is used to recover the glycol that has become = 215 cubic feet
emulsified as fine droplets in the NGL’s (natural gas liquids)
and the dispersed hydrocarbons that have stabilized in This means with gravity alone a 5’ dia. x 20’ tangent
the EG. Since the glycol continually re-circulates in the to tangent vessel would be required. In order to improve
system, fine NGL droplets tend to build up in the inventorycontrol and to allow for disengagement at 10”/min., a
causing an emulsification of both liquid phases. The EG 16” dia. x 30” tall boot was specified. ACS recommended
droplets are thought to be as small as 30 microns in the and supplied a 24" thick mesh coalescer of a co-knit of
organic phase, so 30-minute hold-up times for gravity fiberglass yarn and stainless steel wire. The liquid load-
separation are not uncommon in the industry. ACS was ing sizing criteria required the installation of a 24" high
asked if a coalescer could be provided to significantly segment in a 36" ID vessel. This vessel was 12’ tangent
reduce the resultant vessel size. to tangent with the same 16" diameter X 30" tall boot.
Thus, as compared to a conventional gravity separator,
The process conditions for the coalescer sizing was for it
the use of an engineered coalescer was successful in
to handle 37.5 gpm of NGL’s that had a density of 31
reducing the vessel volume by a factor of 4.5.
lbs/ft3 and a viscosity of 0.11 cp; and 7.5 gpm of 75%
ethylene glycol that had a density of 51.1 lbs/ft3 and a An illustration of this is shown on the cover of this bulletin.

FIGURE 16
GAS PLANT WITH JOULES-THOMPSON DEW POINT CONTROL
Compressor
Gas Product to Pipeline
70˚F 25˚F Hydrocarbon Vapor
Gas-Gas
Exchanger
90˚F @1150 PSIG
Feed From
Gas Field
Flash Tank
J-T Valve Steam
Lean
Glycol
COLD SEPARATOR
WITH COALESCER Reboiler
AT 250 PSIG
Condensate
LC

Rich
Rich Glycol Glycol

Make-up Lean-Rich Exchanger

Pump
Ethylene Glycol Lean Glycol Lean Glycol

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CASE STUDY #3 removing essentially all droplets down to 15 microns.
Coalescers in Alkylation Units A Kuwabara hydrodynamic factor for this media of
A refinery was using a 15-psi mix valve to acid wash 1.251 is found using the data from Table 3. The col-
the reactor products of their H2SO4 alkylation unit. This lection efficiency of a single Teflon fiber is found when
is done to extract both acidic and neutral ester side this factor and the data above are plugged into equa-
products that readily polymerize, reduce acid strength, tion 4 as follows
and cause foaming. A vertical two-stage coalescer
drum with a horizontal boot (Figure 17) follows imme- ηD = 0.07 (1-.019) (15/21) 2
= 0.0163
diately in order to make a clean break between the two 1.251 (1+(15/21))
immiscible phases and lower the free acid concentra-
tion in the hydrocarbon to less than 15 ppm. The first Putting this value in equation 6 gives
coalescer stage in the horizontal section, used to
remove the bulk of the acid, is a vertical Stokes-Pak™ L = π (.00083") (1-.019)ln (1-.999)
element, which is preceded by a 20% open perforated -4(0.0163) 0.019
plate liquid distributor. The second stage is a horizon-
tal ACS Interceptor-Pak™ with Teflon® Multi-Filament = 14.3"
Co-Knit. The inlet section of the large diameter vertical
section removes the fine acid droplets and allows Thus a 15" depth of a 15’ diameter Alloy 20/Teflon
them to drain counter-current to the ascending contin- Multi-Filament Interceptor-Pak Coalescer was chosen
uous hydrocarbon stream. for the second stage element.
Process conditions were 2480 GPM of alkylate that
had a specific gravity of 0.59 and a viscosity of 0.21 cp FIGURE 17
was mixed with 110 GPM of acid (2/1 ratio of recycle
to fresh) that had a specific gravity of 1.85 and a vis- COALESCER IN ALKYLATION UNITS
cosity of 25 cp. The mix valve is reported to create an HYDROCARBON OUT
average droplet size of approximately 400 microns for
the washing, but also generates a significant amount
of fine droplets. Stokes-Pak™ with horizontal sheets
and 1/2" crimps was chosen to remove 99+% of all STAGE 2
Teflon Multifilament Co-Knit
droplets down to about 35 microns. The volume of
15"

coalescer required was estimated with equation 2:

180" DIA.

180" T/T
Vc = 219 * 2590 * 0.5 * .21 = 38.6 cubic feet
HC/
72" I.D.

(1.85-.59) 352 ACID

IN
Thus a 16" thickness of Alloy 20 Stokes-Pak was
used in the 78" ID X 5’ long horizontal boot. 60" T/S Hydrocarbon
Acid
As mentioned above, counter-current flow in the verti- Liquid
Distributor
cal portion of the tower necessitates liquid loads on the
V.B.
coalescer below 15 gpm/ft2 (2 ft/min). This required a
15’ diameter vertical section. The Teflon Multi-Filament
Acid Out
Co-Knit Coalescer was chosen due to corrosive condi-
tions and the tight residual acid specification. Drain
Experience has shown that a 15-ppm spec requires

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Case Study #4 surface area so that it has been found to have an E of
Oil-Water Separator on a Production Platform 0.04. The additional high efficiency polishing of the efflu-
Produced water enters an oil and gas production platform ent water stream obtained with the mat is allowable at this
along with the organics and forms a distinct separate point since it is well protected from particles of sand by
phase after several let downs in pressure through First, the co-knit mesh above.
Second, and even Third Stage Separators; FWKO (Free It is difficult to tell exactly which media did the most to
Water Knock Out) Treaters, Test Separators, etc. achieve the effluent produced water’s compliance with
According to the governing regulations for the Gulf of the <25 mg/l level as is regularly confirmed by an EPA
Mexico all water must be treated to remove oils down to approved lab. However, the following calculations show
<25 mg/l before it can be discharged overboard. Plot plan that the fiberglass mat is up to three times more efficient
area is at a premium on a platform. This often necessi- than fiberglass yarn in coalescing oil droplets from water.
tates a vertical ‘Oil Skimmer Vessel’ and, even though a The Case Study on page 11 showed that 22.4" of co-knit
significant amount of fine sand comes in with the process were required to remove 99.9% of all droplets > 4.5
stream, it must still be high efficiency. In many cases microns.
these are also four phase separators as a small amount Similarly, the Kuwabara Factor for fiberglass mat is
of residual gas needs to be handled as well.
ACS worked with a Gulf Coast fabricator to both design K= -0.5 ln .037 -0.25(.037)2 +(.037) -0.75
the pressure vessel shown in Figure 18 and then supply = 0.935
the internals. Here 10,000 BWPD (barrels of water per Equation 4 is then used to calculate the collection effi-
day) of salt water are handled in an 8’ diameter X 15’ ciency of a single target by Direct Interception as fol-
seam-to-seam vessel with a cone bottom. The inlet nozzle lows:
extends into a tee immediately inside the vessel. One
arm extends vertically above the liquid level where ηD= 0.04 (1-.037) (4.5/8.9)2
gasses can be discharge. It was determined that the 0.935 (1+(4.5/8.9)
amount of gas is so small that the use of a mist elimina- = .00699
tor was not necessary. Simultaneously the contaminated
water jets down toward the cone via the opposite arm. A Finally, by Equation 5 the required element length for
vertical baffle retains the water in a low velocity zone at fiberglass mat is only
the bottom of the vessel where the flow is sufficiently slow
for the sand to drop out. Lastly, at the top of the vessel L= π (0.00035) (1-.037) ln (1-.999)
there is an overflow weir that collects the oil which flows -4 (.00699) .037
by gravity off all the coalescers and then flows through
the oil outlet nozzle under pressure to a suitable, atmos- = 7.1"
pheric holding tank. FIGURE 18
The water is then forced through two stages of coalesc-
ing media. The first is 24" depth of vertical Plate-Pak™
with its plates also in the vertical. When the spacing in this
media at 1/2" there is no line-of-sight and the oil droplets
in the stream are forced to hit 33 baffles in series. Very
fine ones could still float up 42" before striking the roof of
the housing, but are collected at the oil/water interface. At
an effective width of 92" the liquid load is ~11gpm/ft2.
Nonetheless, this is the less efficient orientation, but also
the least susceptible to fouling.
The second stage is in vertical down flow. First there is a
liquid distributor made from 10% perforated plate. This is
needed in order to take full advantage of the entire vol- VERTICAL 10,000
ume of coalescing media. The element is 22" depth of co- BPWD PRODUCED
knit of stainless steel wire and fiberglass yarn that has 2" WATER OIL SKIMMER
of a fiberglass mat below it. The latter media has the
same size target collectors at 8.9 microns as the yarn
material. Besides being denser at an α of 0.037, its
needled, non-woven construction exposes much more

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Case Study # 5 on a tee be raised from 6" to 24". This also
Upgrading a Three Phase Separator helped to prevent water droplets coming off the
A major refiner in the Central US was reluctant to top of the downstream coalescer face from
put any internals in a critical Three Phase entraining into the HC outlet nozzle.
Separator, the Naphtha Stripper Overhead Drum A Stokes Law analysis of the separator while it
of the FCC Unit. However, slugs of water entrain- was cycling showed that mean and maximum
ing in the hydrocarbon phase’s outlet were con- aqueous droplet sizes were 105 and 350
tinually causing cycling of its transfer pump which microns, respectively, as they entered with the
was a high head centrifugal. Water must be naphtha. In order to achieve the specification of
injected upstream of an air cooled condenser to <1/2% water in the naphtha at normal flow and
dissolve ammonium sulfide. The rate of injection <1% at 120% of design, a Stokes-Pak®
had recently been raised 20% due to an increase Coalescer segment that extends to a 39" height
in salt forming components in a new slate of and has horizontal sheets with 1/2" crimps needs
crudes. Nonetheless, any solution had to be able to be 48" deep. Due to the low pressure drop of
to operate over a 30 month turn-around cycle. this media a liquid distributor of 10% open perfo-
Another problem was that their engineers did not rated plate was held 6" away with integral truss-
want to weld to the vessel’s shell since the sour es. In order not to weld to the vessel expansion
water service required stress relieving. rings of 1-1/2" angle were installed upstream of
The three phase inlet consisted of 3900 BPD of the distributor and downstream of the coalescer.
naphtha that at operating conditions had a spe- These rings incorporate jack bolts at several
cific gravity of 0.82 and a viscosity of 1.6 cp, splits in the hoops which forced the ring up
1200 BPD of foul water that had a specific gravi- against the inside of the vessel wall.
ty of 0.99 and a viscosity of .55 cp, and 2.2 In order to achieve the < 1% outlet spec above at
MMSCFD of Off Gas at 0.1136 lbs/ft3. ACS engi- 120% of design flow, 99.9% of all droplets > 60
neers worked around the constraints of an exist- microns must be removed. Equation 3 shows
ing 60" ID X 15’ T/T separator with a 24" diame-
ter X 36" tall boot that was now undersized (see VC= 219 (178.5) .5 (1.6)
Figure 19). Calculations of the gas velocity of 1.8 0.17(60)2
ft/s showed that the Normal Liquid Level (NLL)
had to be left at 39" to allow for mist droplets to = 51.1 cubic feet
fall out in the vessel. However, the velocity of The 39" high segment of 60" ID is equal to 13.5
water in the boot was 20"/minute, double that square feet. Thus 45" of depth is required. This
allowable for oil disengagement (see page 9). was rounded up to the 48" used. After installation
Because of this ACS recommended that the the cycling problem stopped, outlet specs were
oil/water interface be relocated to the main hori- achieved, and the Stokes-Pak made it to the next
zontal section of the vessel and that the naphtha turn-around without significant fouling.
outlet’s internal standpipe with vortex breakers
FIGURE 19

COALESCER RETROFIT INTO AN

EXISTING THREE PHASE SEPARATOR

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 APPROXIMATE RANGES OF APPLICATION FOR VARIOUS COALESCING MEDIA

Plate-Pak™ Wire Mesh Teflon® Fiber Fiberglass

Coalescer Interceptor-Pak™ Interceptor-Pak™ Interceptor-Pak™
125 micron 75 micron 15 micron 7.5 micron

Human hair Mist Fog Bacteria

Three-Phase Extraction Mix Condensation

Separators Columns Valves in Pipelines
Static Two-Phase Caustic Wash Anti-Foam
Mixers Pump Discharges Drums Surfactant

Stokes-Pak™ Wire Wool Polyester Fiber Fiberglass Mat

Interceptor-Pak™ Interceptor-Pak™ Interceptor-Pak™

General References: Holmes, T. L., AIChE Mugele, R. A., and Evans, H. D., ACS Industries presents the
Symposium Series, Industrial and Engineering information in this publication in
American Petroleum Institute 77, 211, pp. 40-47, 1981. Chemistry, 43, 6, 1951. good faith, believing it to be accu-
Publication 421, rate. However, nothing herein is to
Design and Operations of Oil- be construed as either an express
Lee, K. W. and Liu, B.Y.H., Paragon Engineering or implied guarantee or warranty
Water Separators, API Journal of the Air Pollution Services, Produced Water
Refining Department, regarding the performance, mer-
Control Association, 30, 6, Theory and Equipment chantability, fitness, application,
Washington, DC, 1990. 4/80. Description, Houston, TX. suitability, nor any other aspect of
the products and services of ACS
Gas Processors Suppliers Monnery, W.D. and Svrcek, Perry’s Chemical Engineer’s Industries, LP. No information
Association, Engineering Data W.Y., Chemical Engineering Handbook, 6th Edition, contained in this bulletin consti-
Book, Volume 1, 11th Edition, tutes an invitation to infringe any
Progress, pp. 29-40, 9/94. McGraw-Hill, New York, NY, patent, whether now issued or
Tulsa, OK, 1998. 1984. issued hereafter. All descriptions
Lieberman, N. P., and specifications are subject to
Hoffmann-La Roche Standard Troubleshooting Process Reist, P.C., Aerosol Science change without notice. Stokes-
Design Practice for Decanters Operations, and Technology, 2nd Edition, Pak, Interceptor-Pak and Plate-
(Liquid-Liquid Settlers), Nutley, 3rd Edition, PennWell Books, McGraw-Hill, New York, NY, Pak are trademarks of ACS
NJ, 11/84. Industries, LP. Teflon is a regis-
Tulsa, OK, 1991. 1993. tered trademark of E. I. Dupont de
Nemours.