Hydrocarbon Processing - July 2022 - 70

Catalysts
* Ensure a catalyst handling contractor has the experience,
expertise, equipment and resources to complete the
catalyst unload and reload. Saving $100,000-$200,000 on
the cost of the catalyst handling contractor can easily result
in a multi-day delay in completion of the turnaround,
particularly during the unloading of the catalyst.
During a catalyst change-out turnaround, surprises and issues-impossible
to predict-will arise that must be resolved.
Managing the surprises is a critical success factor and begins
with the planning phase.
Planning for a catalyst reload turnaround should begin soon
after the completion of the last catalyst reload. The first item
to address is the catalyst evaluation and selection for the next
catalyst cycle, once data is available on how the current cycle is
tracking against the predicted performance.
Ideally, the catalyst selection process should begin at least 18
mos-24 mos before the next catalyst change-out to provide sufficient
time for all requisite tasks. Typically, catalyst lead time is 6
mos-12 mos, leaving the remaining time for planning, evaluation
and internal processing. To put it simply: the earlier, the better.
Best practices. As a general practice, it is best to apply a
multi-discipline approach to set the key catalyst requirement
or strategy [e.g., longer run length or more difficult (cheaper)
feedstocks]. Refinery management and the economics and
scheduling departments will have input into the future catalyst
strategies. Additionally, the refinery's focal point (usually a unit
process engineer) should also incorporate current operating issues
(e.g., high reactor pressure drop, feed contamination levels)
into the invitation to bid (ITB) so the catalyst supplier can properly
address these problems in the next cycle.
While some refiners still rely on vendor estimations/predictions,
pilot plant testing has become more popular as a tool to
unveil or expose actual catalyst performance. This evaluation
approach is particularly vital to a critical unit like a hydrocracker,
where a slight difference in product yield can result in multi-million
dollars of profit/loss per year over the whole cycle.
Comparing paper estimates/predictions from different catalyst
vendors is not an apples-to-apples comparison, but this approach
is nonetheless prevalent among refiners due to its simplicity.
Catalyst vendors employ different design assumptions,
feed characterization techniques, kinetic models and product
property estimators (e.g., basic to non-basic nitrogen ratio, aromatics
distribution). Consequently, it is fundamentally inaccurate
to compare estimates/predictions between catalyst vendors
at face value; unfortunately, many refiners are unaware of the errors
inherent in this simplistic approach.
It is, however, acceptable to use a paper-based evaluation
for less critical applications (e.g., for a naphtha or kerosene hydrotreater),
although the best practice is still to have the catalysts
tested before evaluating the options.
For refiners without an in-house pilot plant testing facility,
several companies can provide an independent pilot plant testing
service. Two primary methods are available: full pilot-scale
and high throughput bench-scale approaches. Each method
has its own advantages/disadvantages, and refiners must select
the best independent pilot plant testing laboratory to suit their
requirements and constraints. Based on experience, both approaches
provide adequate essential information for hydrocrack70
JULY 2022 | HydrocarbonProcessing.com
ing catalyst evaluation and selection. It must be noted that some
laboratories are more preferred by refiners than others. At least
one independent laboratory requires 24 mos pre-booking before
the actual test date. As such, a refiner should proactively contact
these independent laboratories as soon as the new cycle starts.
The testing fee for each catalyst loading scheme can range
between $45,000 and $95,000. So, who pays for the pilot plant
testing? The refiner may have to pay the total cost, or the catalyst
suppliers may agree to share this cost. In general, the willingness
of the catalyst supplier to share the testing cost increases
with the value of the catalyst package.
Accurately interpreting the results of the pilot plant testing is
complex and requires experience and expertise.
A catalyst change-out turnaround is a large, complex logistical
undertaking and a structured and disciplined approach to
planning-along with attention to detail-is the foundation
upon which good catalyst turnaround execution is based. A
small, empowered, multi-discipline pre-shutdown team should
be given the responsibility to conduct all planning and preparation
activities and then provide the continuity throughout the
turnaround execution phase. Established project management
practices should be used in the planning phase and an integrated
operations and maintenance schedule should form the basis
of the turnaround plan.
Critical path activities should be subject to careful risk assessment
and challenged and optimized aggressively throughout
the planning and execution phases. Contingency plans
should be prepared for the most likely and high-consequence
events that may impact the turnaround (e.g., weather-sensitive
work like catalyst loading, uncertain or risky activities, and critical
materials or spares that may be required). Confirm the quantities
of fresh catalyst onsite prior to the turnaround and ensure
the catalyst is stored in a safe, dry, cool warehouse. Do not add
additional maintenance or engineering work that could be conducted
during normal operations just because the unit is down.
A detailed plan is required for the catalyst handling work,
covering the spent catalyst unloading and fresh catalyst loading,
along with a dedicated health, safety and environment (HSE)
plan. Detailed procurement and logistics plans should involve
the catalyst vendor and the catalyst handling contractor as early
as possible.
The area around the reactor(s) must be a controlled space
with only authorized entry due to the elevated level of activity
involving people, cranes, vehicles, equipment and, consequently,
the high risk attached to these activities happening in a small
area. Clear planning and communication of how the space is to
be used and controlled (crane locations, truck and forklift access
ways, etc.) are required.
Utility requirements and availability, particularly air and ni),
must be understood and provided with a high derequirement
during catalyst unloading
trogen (N2
gree of certainty. The N2
is often underestimated, especially when unloading from more
than one reactor at a time, when N2
). Ample N2
usage is high elsewhere for
purging vessels and columns of hydrocarbons and hydrogen
(H2
supply and distribution capacity will reduce
supply capacity. A dedicated air supply to
delays caused by high oxygen levels in the reactor(s) resulting
from insufficient N2
the catalyst dense-loading machine is preferred to avoid fluctuating
supply pressure caused by offtake of other users.
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