Hydrocarbon Processing - June 2021 - 35

Process Optimization
rator. Electrostatic separation of FCCU catalyst fines from slurry
oil has been in commercial operation for more than 30 yr. This
technology has continuously been improved to offer a more
robust, automatic process to remove catalyst fines from slurry
oil or other hydrocarbon streams using dielectrophoresis. Only
electrostatic separation can capture sub-micron catalyst fines. All
other technologies are limited to the size of the particle captured
(typically > 15 microns).3
Unique to electrostatic separation technology is the ability to
backflush with raw feed or vacuum gasoil. This increases the middle
distillate production and reduces loss from decreased reactor
productivity. The technology is not affected by the presence of
asphaltenes, making it an excellent choice for removing solids
from residual FCCU-derived slurry oil and from gasoil crackers.
Electrostatic separation operates efficiently and is impervious to
plugging from asphaltenes and waxes, thus significantly reducing
downtime and annual maintenance costs. The efficiency offered
by electrostatic separation technology, coupled with reduced
costs, has a direct and positive effect on a refinery's bottom line
and profit margins.
The economics of making the right choice. An example of
the value generated by using electrostatic separation methods in
removing FCCU catalyst fines from slurry oil is illustrated in the
following example.
An 80,000-bpd gasoil FCCU has a slurry oil yield of 4 vol%
(3,200 bpd). Catalyst content of the slurry oil is 2,000 ppm
(FIG. 1). This is compared against the base case in which the refinery
uses a holding tank to reduce its solids. The slurry oil holding
tank is assumed to require cleaning once per year for 2,000-ppm
slurry solids at a cost of $1.5 MM. Increased catalyst loads will incur
higher-frequency slurry holding tank cleanings and additional
total costs. A portion of the FCCU feed is used to backwash the
electrostatic separator, after which it and the associated catalyst
are fed back to the FCCU, thus reducing fresh FCCU catalyst
costs. FCCU catalyst costs are assumed to range from $2,000/t-
$5,000/t. It is estimated that the average product upgrade value
for this CSO can be between $2/bbl and $4/bbl. Benefits from
not having to purchase chemical settling aids were not considered,
even though such costs are estimated to be approximately
$45,000/yr. A basic case of slurry-to-bunker fuel specifications,
with a minimal uplift of $2/bbl, is presented, along with one case
for recovering 4,000 ppm of catalyst with $4/bbl uplift.
Profits from the use of an electrostatic separator range from
$4.5 MM/yr-$11 MM/yr. Without the proper technology installed
in this process, the reality is a true loss to the refiner.5
An electrostatic separator removes more than 99% of the catalyst
from the slurry to provide a CSO product containing < 50
ppm of FCCU catalyst. Catalyst savings might not be as valuable
for a residual unit, but would still be significant. Individual cases
involving deep residual cracking benefits would have to be calculated
based on a thorough knowledge of the residual FCCU feed,
operating conditions and catalyst characteristics, among other
criteria. It is important to note that smaller catalyst particles returned
to the unit have an inherently larger surface-to-volume
ratio, and could have a considerably higher residual cracking activity
than the larger equilibrium catalyst held in the unit. With
the increased focus on petrochemical production to increase
profits, a major key to survival is finding the right technology to
FIG. 1. View of 2,000-ppm main column bottom catalyst fines shown
through a scanning electron microscope.
increase the value of slurry. An improved bottom line depends
on achieving greater profit from the bottom of the barrel, even in
a post-pandemic reality.3
Post-pandemic recovery. The downstream industry must
find new ways to return profits and maintain on-spec products.
Whether it is providing highly valuable carbon black feedstock
or meeting the new IMO 2020 mandate for marine fuels, the
removal of FCCU slurry oil solids to low levels presents an opportunity
for improved profitability for refiners. The ability to
clarify slurry oil for use in higher-value applications-yielding
more than $4/bbl or eliminating the need for the disposal of
hazardous waste from a sludge in a holding tank-clearly supports
the drive to stabilize and improve a refinery's bottom line.
The upheaval brought about by recent events has opened the
door to new opportunities for the industry to initiate changes
to weather an uncertain future. Fossil fuels are an integral part
of the global economy, and these fuels still contribute strongly
to the world's economies and to daily ways of life. The refining
industry must continue to seek ways to innovate and evolve, and
to meet the challenges in the years ahead. The first step is to invest
in the right technology to increase refining capabilities and
ensure a return to profitability in a post-pandemic reality.
NOTES
a Mott
b Pall Corp.
c Eaton Corp.
d Dahlman
LITERATURE CITED
1
2
Russo, R., " Pandemic hastens threat of closure for struggling oil refineries, "
Hydrocarbon Processing, January 2021.
Kelly, S. and D. K. Kumar, " A historic oil price collapse, with worries headed into
2021, " Reuters, December 29, 2020, online: https://www.reuters.com/article/
us-global-oil-yearend-graphic/a-historic-oil-price-collapse-with-worries-headedinto-2021-idUSKBN2930FJ
3
4
5
Scalco,
V., " The plight of the modern refinery: Racing to meet IMO 2020 regulations, "
Hydrocarbon Processing, December 2019.
Methodology and Specifications Guide-Petroleum Product & Gas Liquids: U.S.
Caribbean and Latin America, Platts, January 2012.
Guercio, V. J., " U.S. producing, exporting more slurry oil, " Oil & Gas Journal,
October 2010.
Hydrocarbon Processing | JUNE 2021 35

https://www.reuters.com/article/us-global-oil-yearend-graphic/a-historic-oil-price-collapse-with-worries-headedinto-2021-idUSKBN2930FJ https://www.reuters.com/article/us-global-oil-yearend-graphic/a-historic-oil-price-collapse-with-worries-headedinto-2021-idUSKBN2930FJ https://www.reuters.com/article/us-global-oil-yearend-graphic/a-historic-oil-price-collapse-with-worries-headedinto-2021-idUSKBN2930FJ

Hydrocarbon Processing - June 2021

Table of Contents for the Digital Edition of Hydrocarbon Processing - June 2021