Hydrocarbon Processing - September 2021 - 50

Refining Technology
of polymers and fluoropolymers in the
coalescer materials of construction allows
for expanded use of coalescers over earlier
conventional types, as these advanced materials
have excellent chemical resistance
to an array of fluids over a wide range of
temperatures from -40°F to 300°F. The
advantages of these coalescer systems are
that they have a small footprint, require
relatively low capital investment by owner/operators
and can break very stable
emulsions with drops in the micron size
range. They do not require electricity or
chemical treatment and can be operated at
a very low turndown ratio due to a separation
mechanism of direct interception. Additionally,
maintenance requirements are
much lower to replace coalescer or filter
cartridges periodically vs. troubleshooting
electrical short circuits and replacing
damaged electrodes. The disadvantages
are that these systems require replacement
cartridges for pre-filters and coalescers,
and they are not economical for mixedphase
streams with high suspended solids
concentrations. Electrostatic separators
vs. high-efficiency cartridge liquid-liquid
coalescers are compared in TABLE 1.
Pilot testing high-efficiency
cartridge
liquid-liquid coalescers. Onsite
pilot testing is useful to demonstrate
the performance of the high-efficiency
cartridge liquid-liquid coalescers
at
FIG. 3. Typical cartridge L/L coalescer inlet/outlet samples collected during pilot tests.
Note: The Middle Eastern refinery and the Canadian refinery are missing pictures of the ECP outlet.
TABLE 1. Electrostatic separators vs. high-effi ciency cartridge liquid-liquid coalescers
Separation technology Capital cost
Footprint
ECP
High-effi ciency
cartridge liquid-liquid
coalescer
High, typically
three times that of
a cartridge coalescer
Low
Large, typically
three times that of
a cartridge coalescer
Small
Separation effi ciency
Limited to larger-sized
droplets in coarse
emulsions
Not limited, can process
1-micron droplets and
larger droplets
Test parameter
Inlet visible
Outlet visiblec
Outlet visible ECP
Inlet sodium, ppm
Outlet sodiumc
, ppm
Outlet sodium ECP, ppm
Outlet free waterc
, ppm
Inlet caustic phase, vol%
Maximum test fl owrate,
gpm
Caustic strength,
°Bé or pH
Kerosene inlet TAN,
mg KOH/g
IFT, dyne/cm
Inlet TSS, mg/l
TABLE 2. Results of liquid-liquid coalescer pilot tests at fi ve refi neries
U.S. Refi nery 1
Hazy
Clear
Hazy
16-102
0.01
Not measured
12.5
0.91-1.97
0.75
3.5°Bé
0.048
1
0.4-1.2
50 SEPTEMBER 2021 | HydrocarbonProcessing.com
U.S. Refi nery 2
Hazy
Clear
Hazy
Not measured
Not measured
Not measured
10-12.5
1.7-2.4
0.76
2.4 °Bé-3.1°Bé
0.014
8.5-12.6
1.1
plant conditions and to determine the
optimum sizing for commercial-scale
equipment. A small-scale test coalescer
(typically, 6 in. in length and 2.5 in. in
diameter) is used, along with a test prefilter.
The pilot test equipment is tied into
the refinery process through side-stream
connections and functions in a manner
nearly identical to the horizontal, highefficiency
cartridge liquid-liquid coalescer
system previously described. The pilot
unit typically operates at a flowrate in the
range of 0.5 gpm-5 gpm. Testing starts at
a low flowrate that, upon verification that
the effluent product is clear and bright, is
subsequently increased in stages to find
the point at which the coalescer performance
is diminished. This point is determined
visually by the haze content in the
coalescer outlet samples collected in glass
bottles. The amount of caustic collected
vs. the total amount of kerosene is meaFouling
technology Operation cost
Low
Moderate, aff ected
by high solids
loadings
Low, unless subject upsets
where electrode failures occur
due to short circuits from slugs
Low-typical pre-fi lter
changeout every 3 mos and
coalescer 1x per yr
Canada refi nery
Hazy
Clear
Hazy
0.07-43.6
0.03-0.14
0.1-1.5
Not measured
0.09-0.46
1.5
3.5°Bé-10°Bé
0.017-0.149
4.8
16.5
Middle East refi nery
Hazy
Clear (0.6 NTU)
Hazy
Not measured
Not measured
Not measured
Not measured
0.22
1.3
13 pH
Not measured
Not measured
7.6
Asia-Pacifi c refi nery
Hazy
Clear
Hazy
6-10
0.18-0.55
1.38-3.3
Not measured
0.28
2
> 14 pH
Not measured
8.4
0.5

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Hydrocarbon Processing - September 2021

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