OCR moving bed technology for the future
CLG's Onstream Catalyst
Replacement process (OCR),
is a counter-current,
moving bed reactor that enables refiners to significantly increase capacity
or improve product quality from a fixed bed RDS
reactor. The high pressure,
high temperature OCR reactor
can be added to the processing scheme either before
or after the fixed bed RDS unit.
When adding an OCR reactor in front of the
RDS unit, refiners can increase feed
throughput and/ or process heavier feeds
with higher levels of contaminant metals, while maintaining excellent product
qualities and economical fixed bed run lengths.
OCR enables refiners to process
resids with more than 400 ppm metal
(Ni + V) or to achieve deeper
desulfurization when processing low metal feeds. In
either case, the life of the downstream catalyst is improved substantially
and problems from pressure drop build-up are reduced.
After thousands of transfers, the catalyst movement system has proven to be simple, safe and highly reliable. Since catalyst transfer is a batch operation (typically once or twice a week), the system is generally used with at least two fixed bed reactors as well as the OCR unit. Catalyst transfer in and out of the OCR reactor is accomplished with no interruption in the processing scheme. |
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How OCR works
The OCR reactor
adds fresh catalyst and removes spent catalyst from a high
pressure reactor while the unit is onstream.
Fresh catalyst is added at the top of the reactor while residuum is fed into
the bottom. Both catalyst and feed move through the reactor in a counter-current
flow, causing the dirtiest residuum to contact the oldest catalyst first. The
up flow of the residuum through the OCR
reactor slightly expands the catalyst
bed. This enhances residuum/ catalyst contact, minimizes reactor plugging and
creates a consistent pressure drop for optimum flow patterns.
Meanwhile, the fully spent OCR
catalysts are removed at the bottom of the reactor.
Processing higher metal feeds
Either by crude changes or cutting deeper into the barrel, refiners have
maintained and/ or improved fixed bed run length and product quality.
Producing ultra-low sulfur fuel
OCR minimizes the
amount of fixed bed demetalation catalyst needed to protect
the high activity desulfurization catalyst while maintaining consistent catalyst
performance throughout the run.
Preparing feed for the RFCC
OCR/RDS technology has provided excellent quality
RFCC feed from a variety
of heavy atmospheric residuum feeds, including Arabian Heavy and Ratawi, with
no operating problems.
OCR was first commercialized in 1992 at Idemitsu Kosan Company (IKC) Ltd.’s Aichi Refinery. By adding an OCR reactor in front of their existing RDS unit, IKC was able to switch feeds from 100% Arabian Light to a less expensive blend of 50% Arabian Light and 50% Arabian Heavy.
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Retrofit or grassroots OCR improves production economics
OCR's efficient design can be
easily integrated into existing refinery configurations.
When retrofitting a fixed bed residuum hydrotreater with an
OCR reactor, benefits
may include the ability to:
- process less expensive heavy, high metals feedstock
- increase the feed rate to the existing
RDS/VRDS
unit
- increase product quality by operating the unit more severely
In grassroots installations, refiners can reduce overall construction cost
and minimize future operating expenses by building smaller fixed bed reactors
to achieve a given product target.
In either retrofit or grassroots installations, the investment cost of installing
an OCR reactor and
catalyst transfer equipment are more than offset by the
savings realized in crude cost and in improved catalyst efficiency.