Hydrocarbon Processing - September 2021 - 55

Catalysts
C. BAILLIE, W. R. Grace, Worms, Germany;
and C. COOPER, W. R. Grace, Houston, Texas
Deliver high levels of SOx
with SOx
The global refining industry continues
) emisto
move toward more restrictive environmental
laws for sulfur oxide (SOx
sions. In addition, many refineries are
looking to maximize fluid catalytic cracking
unit (FCCU) profitability by processing
more challenging feedstocks that are
higher in sulfur, or using SOx
reduction
additives to reduce caustic consumption
in the wet gas scrubber for overall OPEX
reduction. As such, SOx
emissions control
remains a crucial topic for refineries
to ensure competitiveness in the market.
The authors' company recognizes this
and has recently allocated considerable
resources to developing the latest generation
of SOx
reduction additives.
SOx
A new FCC additive technologya
reduction has been successfully
for
commercialized. The SOx
reduction
additive incorporates a more homogeneous
distribution of cerium and vanadium
across the additive particle, as well
as an increase in the magnesium aluminate
spinel content of the additive. Since
its introduction, several refiners have
switched from general SOx
ditives to the proprietary SOx
reduction adreduction
additivea
due
to the step-out improvements
in performance.
The BP Rotterdam refinery recently
began using the proprietary additive.
This refinery initially switched from a
general SOx
authors' company's additivesb
by the aforementioned SOx
additivea
additive to another of the
, followed
reduction
. Both additive changes resulted
in an increase in SOx reduction.
SOx
additive development. In 2018,
additive manufacturing
the authors' company made a modification
at its SOx
facilities, which required significant capital
investment. The result is an improved
reduction
-reduction additive
version of its additiveb
for SOx
reduction,
adated
without an SOx
with improvements to both product properties
and performance. The new SOx
ditive was initially referred to by another
namec
to signify the improvement in
cerium and vanadium dispersion across
the additive particle. However, based on
commercial performance, the new additive
technology is being brandeda
to better
reflect its step-out performance.
Cerium and vanadium dispersion
play an important role in SOx
additive
performance. Improved dispersion of
these key active ingredients results in a
more effective oxidation of sulfur dioxide
(SO2
) to sulfur trioxide (SO3
), and
enhances the additive regeneration step
where the sulfate is reduced to hydrogen
sulfide (H2
steps in the SOx
For the development of SOx
S), both of which are key
reduction mechanism.
reduction
additives, the authors' company utilizes
larger scale test equipment, specifically
the Davison circulating riser (DCR) pilot
plant.1
Such a pilot unit provides valuable
information based on a continuous operation.
Additionally, compared to benchscale
units, the DCR pilot plant has the
advantage in that it mimics all the processes
present in a commercial operation
and can also operate at the same hydrocarbon
partial pressure as a commercial
unit. The continuous catalyst regeneration
in the DCR allows for the measurement
of regenerator SOx
oxide (NOx
and nitrogen
) emissions and testing of environmental
additives, experiments that
cannot be done in a batch unit.
FIG. 1 shows DCR pilot plant testing
comparing SOx reduction performance
for SOx
nadium and cerium vs. the same SOx
additives with less-dispersed vaadditives
with a higher level of dispersion.
The pilot plant testing was initially operthe
baseline level of SOx
0 hr " the SOx
additive to establish
, then at " Time =
additive was introduced in
a single dose to observe the initial level of
SOx
of time required for the SOx
reduction. The subsequent period
emissions to
increase back to the baseline level of SOx
was used as a measurement for the additive's
effectiveness for SOx
reduction.
The additives with high and low vana),
and
dium dispersion were tested at the standard
level of 1 vol% oxygen (O2
the results highlighted that both additives
showed the same initial level of SOx
reduction, but the additive with a higher
level of vanadium dispersion retained
the SOx
reduction activity for a longer
period of time.
200
180
160
140
120
100
80
60
40
20
-1
1
2
Lower V Dispersion
3
4
5
Time on additive, hr
Higher V Dispersion
FIG.1. Impact of vanadium dispersion
on SOx
additive performance.
120
80
100
60
40
20
11/5/17
Other SOx
2/13/18
additive
5/24/18
9/1/18
FIG. 2. The 7-d average SOx
(normalized).
12/10/18
Proprietary SOx additiveb
3/20/19
Proprietary SOx
additive rate
Hydrocarbon Processing | SEPTEMBER 2021 55
6/28/19
additivea
6
7
8
SO2, ppm
Hydrocarbon Processing - September 2021

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