Hydrocarbon Processing - November 2022 - 65

Plant Safety and Environment
due to friability of solid sulfur-
and also possible in the cleanup
of sulfur spills
3. Explosions associated with fuel
gas burner ignition (methane
LEL 5%): Most likely with
improper or missing BMSs when
lighting SRU reaction furnaces,
reheaters and incinerators
4. Explosions (deflagrations)
associated with rapid
vaporization of liquids (most
SRU vessels are rated for 15 psi-
50 psi (100 kPa-350 kPa): Most
likely with high-pressure waste heat
boiler leaks or with rapid flashing
of a heat transfer medium.
The author's company's direct experience
with SRU explosions includes the
following:
* Sulfur storage (pits/tanks)
H2
S explosions: Six cases
* Sulfur transportation H2
explosions: One case
S
* Sulfur dust explosions: Two cases
* Burner ignition explosions:
Three cases
* Liquid-to-vapor pressure
explosions: Three cases
* Unknown internal explosions:
Two cases.
In addition, the OSHA records review
indicated one SRU explosion with which
the author's company was not familiar. A
refinery SRU explosion resulted in four
people being hospitalized, although further
details about the cause of the explosion
were not provided.
Overall, these cases represent an SRU
explosion incident rate of around one incident
every 2 yr. The author's company
is not aware of any deaths associated with
any of these explosions; however, most of
the cases have involved near misses (i.e.,
personnel were in the vicinity), and some
have involved injuries and hospitalizations.
All cases have involved significant
equipment damage and/or significant
lost processing opportunities.
Regarding incident investigations for
SRU explosions, the first step usually
involves a review to determine the most
likely type of explosion (H2
S, sulfur dust,
fuel gas, pressure). Although, in some cases,
this may be obvious, other cases may
require a more detailed investigation. As
with process fluid release incidents, the
determination of an explosion's root cause
usually comes down to a combination of
design reviews, equipment walkthroughs,
historical data reviews and personnel interviews
to determine if the release was
the fault of design or due to operational or
personnel procedures.
Regarding the prevention of future
explosions, the following recommendations
are based on the most common root
causes of explosions:
* H2
S explosions:
° Ensure proper sweep gas design
for liquid sulfur storage and
transportation vessels so that
the LEL cannot be reached.
In addition, confirm accurate
measurement of the sweep
flowrate so that operators know
when the sweep system is having
problems. Backup options for
non-working sweep systems
(e.g., second eductor, natural
venting, nitrogen blanketing)
should also be considered.
° Strongly consider degassing
of liquid sulfur to remove
enough H2
LEL downstream of the
degassing system.
° Include designed and operated
grounding systems in sulfur
storage, transfer, loading and
transportation systems, and
check that proper grounding
is in place before liquid sulfur
loading commences.
* Sulfur dust explosions:
° Properly educate personnel on
the possibility of dust explosions.
° Employ suitable dust collection
and/or suppression systems
during operation of a process
that might create sulfur dust.
* Explosions associated with
burner ignition:
° Confirm that up-to-date BMSs
are in place.
° Where modern BMSs are not
in place, review procedures to
prevent reaching fuel gas LEL
during burner ignition.
* Explosions associated with rapid
vaporization of liquids:
° Employ detailed design and
operating HAZOP reviews to
minimize the chances of expansive
fluids entering hot process vessels.
° Review all available pressure relief
options to prevent deflagration in
case of rapid vaporization.
S to prevent reaching
Takeaways. Despite the constant improvements
in design, operation and understanding
of SRUs, physical and mechanical
failures continue to occur frequently, causing
loss of processing and profits, and leading
to significant safety incidents. Based on
the author's company's case files, the serious
incident rates for the five failure types
discussed in this article include:
* Corrosion: 25-30 cases/yr
* Plugging: 25-30 cases/yr
* Thermal excursions: More than
20 cases/yr
* Process fluid releases: One serious
incident per year, one SRU-related
H2
* Explosions: One serious incident
every 2 yr.
It
is hoped that this summary will
serve to focus the industry's attention on
the continued high prevalence of these
types of dangerous incidents in the SRU
industry, along with the available means
for prevention, and the need for even
more improvements in SRU design, operation
and personnel training.
ACKNOWLEDGMENTS
The author would like to acknowledge Sulphur
Experts consultants (past and present) whose field
work and experience provided the bulk of the cases
for this database. The author would also like to thank
the plant personnel involved with these incidents who
have been willing to share pictures, videos and stories of
their experiences so that others might learn from them.
NOTES
This article was first presented at the Laurance Reid
Gas Conditioning Conference in Norman, Oklahoma,
in February 2022.
a
Laboratory test data was provided by Porocel.
LITERATURE CITED
7
OSHA, " Accident search database, " U.S. Department
of Labor, online: https://www.osha.gov/pls/imis/
accidentsearch.search?acc_keyword=
8
Lagas, J. A., " Stop emissions from liquid sulfur, "
Hydrocarbon Processing, October 1982.
GERALD E. BOHME has been
directly involved in all aspects of
the process engineering consulting
work conducted by Sulphur Experts
Inc. since 1988. He provides expert
advice and consulting services in
the areas of plant inspections,
testing and plant optimization for the sour gas and oil
refining industries-including working on plant
optimization projects in more than 200 operating
facilities around the world. He also has primary
responsibility for overseeing all of Sulphur Experts'
field crews and technical reports. His experience in
the field of sulfur recovery is global-he has worked
on projects in more than 50 countries.
Hydrocarbon Processing | NOVEMBER 2022 65
S death every 2 yr in OSHA files,
and one liquid sulfur-related death
or injury every 3 yr in OSHA files
https://www.osha.gov/pls/imis/

Hydrocarbon Processing - November 2022

Table of Contents for the Digital Edition of Hydrocarbon Processing - November 2022

Industry Perspectives
Editorial Comment
Construction
Innovations
Digital Technologies
Optimization of ethylene in the processing of hydrocarbons
Shift focus to more open control technology
Integrated remote operations drive collaboration and autonomy
Reliability analysis of analyzers bridges the gap between assessing and addressing risk
Implement advanced level control techniques to improve crude distillation unit stabilizer performance
Leading capital projects in a VUCA environment
Trip your turbine troubles: Optimize the reliability of steam-driven turbines
Development of novel epoxy closed-cell foam for personnel and corrosion protection—Part 2
Obsolescence management in a manufacturing unit
Decarbonizing your fired heaters with hydrogen fuel
Mechanical design challenges in high-temperature electric heaters
Why sulfur plants fail: An in-depth study of sulfur recovery unit failures—Part 2
Advertiser Index
Hydrocarbon Processing - November 2022 - 1
Hydrocarbon Processing - November 2022 - 2
Hydrocarbon Processing - November 2022 - 3
Hydrocarbon Processing - November 2022 - Industry Perspectives
Hydrocarbon Processing - November 2022 - 5
Hydrocarbon Processing - November 2022 - 6
Hydrocarbon Processing - November 2022 - Editorial Comment
Hydrocarbon Processing - November 2022 - 8
Hydrocarbon Processing - November 2022 - 9
Hydrocarbon Processing - November 2022 - Construction
Hydrocarbon Processing - November 2022 - 11
Hydrocarbon Processing - November 2022 - Innovations
Hydrocarbon Processing - November 2022 - 11B
Hydrocarbon Processing - November 2022 - 12
Hydrocarbon Processing - November 2022 - Digital Technologies
Hydrocarbon Processing - November 2022 - 14
Hydrocarbon Processing - November 2022 - 15
Hydrocarbon Processing - November 2022 - 16
Hydrocarbon Processing - November 2022 - Optimization of ethylene in the processing of hydrocarbons
Hydrocarbon Processing - November 2022 - 18
Hydrocarbon Processing - November 2022 - 19
Hydrocarbon Processing - November 2022 - 20
Hydrocarbon Processing - November 2022 - Shift focus to more open control technology
Hydrocarbon Processing - November 2022 - 22
Hydrocarbon Processing - November 2022 - 23
Hydrocarbon Processing - November 2022 - 24
Hydrocarbon Processing - November 2022 - Integrated remote operations drive collaboration and autonomy
Hydrocarbon Processing - November 2022 - 26
Hydrocarbon Processing - November 2022 - 27
Hydrocarbon Processing - November 2022 - 28
Hydrocarbon Processing - November 2022 - 29
Hydrocarbon Processing - November 2022 - 30
Hydrocarbon Processing - November 2022 - Reliability analysis of analyzers bridges the gap between assessing and addressing risk
Hydrocarbon Processing - November 2022 - 32
Hydrocarbon Processing - November 2022 - 33
Hydrocarbon Processing - November 2022 - Implement advanced level control techniques to improve crude distillation unit stabilizer performance
Hydrocarbon Processing - November 2022 - 35
Hydrocarbon Processing - November 2022 - 36
Hydrocarbon Processing - November 2022 - Leading capital projects in a VUCA environment
Hydrocarbon Processing - November 2022 - 38
Hydrocarbon Processing - November 2022 - Trip your turbine troubles: Optimize the reliability of steam-driven turbines
Hydrocarbon Processing - November 2022 - 40
Hydrocarbon Processing - November 2022 - 41
Hydrocarbon Processing - November 2022 - 42
Hydrocarbon Processing - November 2022 - 43
Hydrocarbon Processing - November 2022 - 44
Hydrocarbon Processing - November 2022 - 45
Hydrocarbon Processing - November 2022 - 46
Hydrocarbon Processing - November 2022 - Development of novel epoxy closed-cell foam for personnel and corrosion protection—Part 2
Hydrocarbon Processing - November 2022 - 48
Hydrocarbon Processing - November 2022 - 49
Hydrocarbon Processing - November 2022 - 50
Hydrocarbon Processing - November 2022 - Obsolescence management in a manufacturing unit
Hydrocarbon Processing - November 2022 - 50B
Hydrocarbon Processing - November 2022 - Decarbonizing your fired heaters with hydrogen fuel
Hydrocarbon Processing - November 2022 - 52
Hydrocarbon Processing - November 2022 - 53
Hydrocarbon Processing - November 2022 - 54
Hydrocarbon Processing - November 2022 - Mechanical design challenges in high-temperature electric heaters
Hydrocarbon Processing - November 2022 - 56
Hydrocarbon Processing - November 2022 - 57
Hydrocarbon Processing - November 2022 - 58
Hydrocarbon Processing - November 2022 - 59
Hydrocarbon Processing - November 2022 - 60
Hydrocarbon Processing - November 2022 - Why sulfur plants fail: An in-depth study of sulfur recovery unit failures—Part 2
Hydrocarbon Processing - November 2022 - 62
Hydrocarbon Processing - November 2022 - 63
Hydrocarbon Processing - November 2022 - 64
Hydrocarbon Processing - November 2022 - 65
Hydrocarbon Processing - November 2022 - Advertiser Index
Hydrocarbon Processing - November 2022 - 67
Hydrocarbon Processing - November 2022 - 68
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