Hydrocarbon Processing - February 2021 - GP-14

SPECIAL FOCUS: TREATING SOLUTIONS

Hydrocarbon
Caustic
Caustic/air/disulfide mix
Disulfide
Disulfide-caustic mix
Anthracite coal

Treated product

Extractor
plus

The current disposal methods for disulfide oil include:
* Deep well: See previous section
* Combination with sweetened naphtha: The combined
stream can be sold as bitumen diluent
* Waste hauler: See previous section
* Incineration in a combustor: SOX and other
consent-decree gases are generated
* Green disposal unit: Generates a 100% environmentally
compliant liquid or solid stream (FIG. 3).
The current disposal method for spent air includes:
* Vent to atmosphere: Typically needs activated carbon
canisters or special consent decrees for the strong,
objectionable disulfide and mercaptan smell
* Incineration in a combustor: See above
* Green disposal unit: Generates a 100% environmentally
compliant liquid or solid stream (FIG. 3).

Spent air to disposal

Disulfide oil

Air
Catalyst

Disulfide
separator

Feed

Static
mixer

Oxidizer
Regenerated caustic

Spent caustic to degassing drum

FIG. 3. Sulfur streams are spent air to disposal, disposal oil and
spent caustic to degassing drum.

methods, depending on acceptable environmental regulations. As emission regulations continue to tighten, the disposal of these effluent streams will come under greater scrutiny.
Minimizing environmental impact through use of greener
technology alternatives is becoming the best practice to process these streams.
Typical disposal methods for spent caustic include:
* Paper mills: These mills use sulfidic caustic in the
manufacture of caustic. If the midstream facility is
near a paper mill, a regeneration section may not even
be necessary, since the paper mill will likely pay the
fresh caustic cost to take the caustic.
* Deep well: The waste caustic is pumped back into
a well belowground. This is the least expensive
alternative; however, consent decrees allowing this
practice are expiring, and environmental agencies
are unlikely to renew them.
* Wet air oxidation methods: Sulfidic caustic
catalytically converts to salts in a reactor while reducing
chemical oxygen demand (COD) and biochemical
oxygen demand (BOD) by 50%-95%. Various
installation costs and recurring operating and catalyst
costs are involved. Units are difficult to operate
due to salting out and reactor bed plugging.
* Acid neutralization: A mineral or strong organic
acid is used to neutralize the caustic. H2S, mercaptans
and other acid gases evolved from the solution are
either incinerated or captured by other technologies,
creating more disposal issues.
* Waste hauler: A special waste hauler picks up the
caustic from the site and disposes of it; the cost could
exceed millions of dollars per year.
* Green disposal unit: Generates a 100% environmentally
compliant liquid or solid streamg (FIG. 3).
14 JANUARY/FEBRUARY 2021 | GasProcessingNews.com

Takeaway. Caustic treatment is an important part of gas processing operations to combat impurities to prevent corrosion
and to meet a variety of regulations. Many impurities need to be
considered when designing a treatment plan, including the boiling points of different compounds, as well as chemical reactions.
Extraction and sweetening processes are solutions to caustic treatment that can be designed for greenfield installations
and retrofitted into existing plants to maximize efficiency and
provide a cleaner feed to further downstream processes. Each
customer is faced with specific constraints, and licensors can
provide guidance on the tradeoffs between entire-stream or
partial-stream treating to meet CAPEX and OPEX objectives.
Additionally, these treating processes can be combined with
the state-of-the-art effluent disposal technology to provide a
greener, more-flexible effluent treatment solution to meet the
processor's needs and regulation requirements. GP
NOTES
UOP's Enhanced Prewash design
b
UOP's post-treatment COS removal section
c
Observed and diagnosed by UOP at various midstream facilities
d
UOP disulfide scrubber
e
UOP Minalk sweetening unit
f
UOP SweetFrac
g
UOP Callidus' nViro Met
a

JESSY TRUCKO is Principal Technology Specialist in the
Treating Technical Services Group at Honeywell UOP. He has
been with Honeywell UOP for more than 20 yr. During his time
in UOP's Development Group, he advanced the company's
alkylene and FCC technologies. Mr. Trucko has been involved
with Merox as a Project Engineer in the Gas Processing
Engineering Department and as a Treating Technical Service
Specialist for the past 13 yr. During this time, he designed individual units and
complexes. He has also innovated multiple improvements to the Merox design,
some of which are trade secrets and others which have been awarded patent.
Mr. Trucko holds a BS degree from the University of Illinois at Chicago, is a
Six Sigma Black Belt and holds seven patents.
JON TERTEL is Senior Offering Manager for Alkylation and
Merox at UOP LLC, a Honeywell Company. Over the past
29 yr, he has performed assignments with increasing scope
of responsibility in field operating services, engineering,
management, technology development and business
associated with a range of key UOP refining, petrochemical
and gas purification technologies. Mr. Tertel obtained his
BS degree in chemical engineering from the University of Wisconsin at
Madison and holds more than 25 U.S. patents.

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Hydrocarbon Processing - February 2021

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