PROCESSING
TECHNOLOGY
Discussion expands to
include hydroprocessing
This second of three articles presenting selections from the
2014 American Fuel and Petrochemical Manufacturers Q&A
and Technology Forum (Oct. 6-8, Denver) continues a discussion of safety and also addresses issues of mechanical integrity and profitability related to hydroprocessing.
The first installment, based on edited transcripts from
the 2014 event (OGJ, Aug. 3, 2015, p. 52), addressed gasoline
processing operations, with a focus on safety, blending, and
reforming issues. The final installment (OGJ, Oct. 5, 2015)
will highlight discussion surrounding processes associated
with fluid catalytic cracking.
The session included four panelists comprised of industry experts from refining companies and other technology
specialists responding to selected questions and then engaging attendees in discussion of the relevant issues (see accompanying box).
The only disclaimer for panelists and attendees was that
they discuss their own experiences, their own views, and
the views of their companies. What has worked for them in
their plants or refineries might not be applicable to every situation, but it can provide sound guidelines for what would
work to address specific issues.
Safety
As more refiners consider installing zeolite catalyst in their
hydrotreating units, what are your recommendations for a
depressuring system?
I am going to discuss both the emergency depressurization system (EDS), which is a manual depressurization
system, and the automated depressurization system (ADS).
I will start with the EDS since the ADS piggybacks on this
manual system.
All hydroprocessing units have an EDS. The EDS valve(s)
must be capable of activation by a dedicated button in two
locations: one on the control panel and one in a safe field
location. There is little difference in EDS sizing criteria between Chevron Lummus Global (CLG) and Chevron Corp.
(CVX). For CLG, we provide two equally-sized valves in parallel, with each valve sized to reduce the pressure to 25% of
normal in 20-30 min. The CVX standard is depressurization
to 50% of normal in 15 min and depressurization to nitrogen header pressure in 30 min.
The CLG standard is two redundant and equally-sized
valves installed in parallel. The pri-
mary activation is one valve, but the
operator has control of the second
valve. So you can effectively double
the depressurization rate if your re-
lief system is sized accordingly and if
the situation warrants it. When both
valves are utilized, the CLG system
will depressurize at a rate similar to
the CVX standard. Finally, the fail-
safe design condition is for the EDS valves to “Fail Open”
with loss of signal.
With EDS activation, the makeup hydrogen flow is reduced to 25% of normal to ensure that depressurization occurs as rapidly as expected. CLG will trip the heater to pilots. CVX trips the heater to a full chop.
Now I will discuss the ADS system. I mentioned that
EDS is required for all hydroprocessing units. The current
practice for ADS is that it is not required for hydrotreating
service using hydrotreating catalysts only, but it is required
for any unit utilizing hydrocracking catalyst, including mild
hydrocrackers.
We are currently reviewing the newest generation of
high-activity hydrotreating catalysts. There are some extremely active hydrotreating catalyst options available now,
and we are considering adding these catalysts to the list for
AFPM Q&A— 2
The panelists
Derek Blackwell, senior staff engineer for hydroprocessing
technology, Chevron Lummus Global LLC
Sergio Robledo, hydroprocessing catalysts technical manager, Haldor Topsoe Inc.
Kathy Wu, senior hydroprocessing technologist, Shell Global
Solutions (US) Inc.
Rick Manner, hydroprocessing specialist, KBC Advanced
Technologies Inc.
The respondents
Jeff Bull, Valero Energy Corp.
Michael Adkins, KP Engineering LP
Steven Zaritsky, Axens North America Inc.
Kevin Proops, Solomon Associates Inc.
Ray Hansen, Sinclair Wyoming Refining Co.
Danna Sharpe, Flint Hills Resources LLC
