Hydrocarbon Processing - January 2022 - 70

Bio-Based Processing
ditions. Counter-dosing with an acid or
base to neutralize them is common practice.
Judicious addition of base in the optimal
location can also reduce the energy
requirements for stripping the water. Detailed
discussions of this and other operational
challenges in sour water stripping
have been published in literature.15
Wastewater can also contain significant
quantities of hydrocarbons and particulates,
and may vary significantly in appearance,
depending on the degree of contamination
in the source waters (FIG. 6).
Hydrocarbons that are not stripped from
the water will often-in conjunction with
particulates-form a fouling material that
adversely affects SWS performance.15
In addition, lighter hydrocarbons that
enter the SWS will be removed and sent
with the overhead gas to the SRU. This
may create operational problems for the
SRU and be detrimental to its performance.
Even a small increase in heavier
hydrocarbons in the SWAG can result
in a large increase in the amount of air
required for combustion in the SRU reaction
furnace, a phenomenon that is aggravated
when the hydrocarbon content of
the water is not stable. The following may
occur in the SRU because of hydrocarbons
in the sour water:
* Decreased hydraulic capacity
* Unstable plant operation
due to variable air demand
* Damage to the SRU reaction
furnace caused by rapid temperature
variations
* Reduced efficiency because of
poor H2
S-to-SO2 ratio control
* Decreased recovery efficiency
due to increased carbon
disulfide (CS2
) formation
* Increased operating pressure
from catalyst bed plugging by
soot deposition from incomplete
hydrocarbon combustion
* Decreased catalyst activity
because of catalyst blockage
from aromatic cracking
* Reduced sulfur quality due to
soot in the sulfur product,
resulting in " black sulfur "
* Soot fouling of the sulfur plant waste
heat boiler and condenser systems.
These effects are extensively documented
in literature.16
Hydrocarbons in water streams can be
present in three forms: free, dissolved and
emulsified.17
In most cases, biofeed co70
JANUARY 2022 | HydrocarbonProcessing.com
processing is done without resizing water
separation vessels on the FCCU or HDT,
which means less residence time for water
and liquid hydrocarbon separation
because of the increased water volume associated
with processing biofeeds. Additionally,
less time for separation can leave
more liquid hydrocarbon in the wastewater
from the FCCU or HDT.
Minimizing the hydrocarbon content
of the sour water feed may be achieved by
the following actions:
* Removing free hydrocarbons in
the inlet three-phase separator; in
general, 25 min of residence time
with a liquid level at 50%-60% of
drum height is optimal
* Installing a sufficiently large feed
stabilization tank with hydrocarbon
skimming facilities (sometimes,
these tanks have several days of
residence time, during which some
emulsified hydrocarbons will
come out of emulsion and may be
removed)
* Installing a coalescer to remove
emulsified hydrocarbons-typically,
this requires pre-filters (FIG. 7)
* Using a hydro-cyclone separator to
reject a hydrocarbon-rich light phase
back to the feed stabilization tank.
Part 2. Part 2 will be published in the
February issue.
NOTES
This work was first presented at the 28th European
Biomass Conference & Exhibition (EUBCE 2020).
ACKNOWLEDGMENTS
The authors would like to thank MPR Services for
sharing information on FCCU breakdown products,
Jeroen Engels for his assistance with graphics and formatting
and Peter Seville for the proofing of this paper.
LITERATURE CITED
1 Van Dyk, S., J. Su, J. D. McMillan and J. N. Saddler,
" 'Drop-In' Biofuels: The Key Role that Co-Processing
will Play in Its Production, " IEA Bioenergy, 2019.
2
Karatzos, S., J. D. McMillan and J. N. Saddler, " The
Potential and Challenges of Drop-In Biofuels, " IEA
Bioenergy, 2014.
3
Pinho, A. R., M. B. B. Almeida, F. L. Mendes, L. C.
Casavechia, M. S. Talmadge, C. M. Kinchin and H.
L. Chum, " Fast Pyrolysis Oil from Pinewood Chips
Co-Processing with Vacuum Gas Oil in an FCC Unit
for Second Generation Fuel Production, " Fuel, 2017.
4
Egeberg, R., K. Knudsen, S. Nyström, E. L. Grennfelt
and K. Efraimsson, " Industrial-Scale Production of
Renewable Diesel, " Petroleum Technology Quarterly,
2011.
5
Van Dyk, S., J. Su, J. D. McMillan, J. N. Saddler
and J. Su, " Potential Synergies of Drop-In Biofuel
Production with Further Co-Processing at Oil
Refineries, " Biofuels, 2019.
6
Kampman, B., R. Verbeek, A. van Grinsven, P. van
Mensch, H. Croezen and A. Patuleia, " Options to
Increase EU Biofuels Volumes Beyond the Current
Blending Limits, " European Commission Study, 2013.
7
Bielansky, P., A. Weinert, C. Schönberger and A.
Reichhold, " Catalytic Conversion of Vegetable Oils
in a Continuous FCC Pilot Plant, " Fuel Processing
Technology, 2011.
8
Ng, S. H., N. E. Heshka, Y. Zheng, Q. Wei and F.
Ding, " FCC Co-Processing Oil Sands Heavy Gas Oil
and Canola Oil. 3. Some Cracking Characteristics, "
Green Energy & Environment, 2019.
Complete literature cited available online at
www.HydrocarbonProcessing.com.
PHILIP LE GRANGE is a chartered
Chemical Engineer with 15 yr in
operating, design and consulting
roles. He has performed
troubleshooting, optimizing,
commissioning and training on the
amine and sour water systems at 77
production facilities across 31 countries. He is a
co-author of the industry reference textbook Amine
Treating and Sour Water Stripping.
KAIYR TEKEBAYEV is a Process
Engineer at Sulphur Experts,
specializing in the commissioning
and startup of sulfur and amine
facilities. He is passionate about
developments in the renewable
energy industry and is working
toward obtaining an MS degree in renewable energy
engineering from the University of Aberdeen.
LEAH GOETTLER is a Chemical
Engineer with 4 yr of experience as
a Process Engineer-in-Training at
Sulphur Experts. During that time,
she has been directly involved in
more than 35 different sulfur
recovery plant projects, with work
ranging from testing and optimization to design
evaluations across North America, Europe, Asia and
the Eastern Mediterranean.
JAN KIEBERT is a Regional Manager
for Sulphur Experts, responsible for
projects in Europe, the Middle East
and Asia. Since 2005, he has been
directly involved in all aspects of
the process engineering consulting
work conducted by Sulphur Experts
and has worked in more than 35 countries. Mr. Kiebert
has provided consulting services in plant
troubleshooting, inspections, reliability studies, design
evaluations, testing and plant optimization for the
sour gas and oil refining industries. He is also one of
the primary speakers at Sulphur Experts' globally
recognized Sulphur Recovery Seminar, which has
been presented at nearly 100 sites around the world.
MIKE SHEILAN is the Co-founder
of Amine Experts and is the Senior
Principal Engineer for Amine
Experts and Dehydration Experts.
For 41 yr, he has provided training
and consulting services in hydrate
control, gas dehydration, gas
and liquid sweetening, hydrocarbon recovery and
sulfur plant operations.He is a co-author of the
industry reference textbook Amine Treating and
Sour Water Stripping.
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