Hydrocarbon Processing - August 2021 - 39

Process
Optimization
M. B. MATAR, A. A. MANE and M. RAJENDRAN,
Kuwait National Petroleum Co., Ahmadi, Kuwait
MAA refinery-Bunker fuel oil challenge:
Stable and compatible VLSFO production
Studies have been conducted on strategies
for bunker fuel oil (BFO) production
with reduced sulfur and catalytic fines
concentration limits. However, these studies
conclude that refiners must face challenges
in terms of BFO stability and compatibility.
In addition, prices and demand
for heavy fuel oil (HFO) will diminish,
forcing refineries to find alternate options
for its disposal. Therefore, to determine
strategies for BFO production, Kuwait
National Petroleum Co.'s (KNPC's) Mina
Al-Ahmadi (MAA) refinery has conducted
feasibility and pilot studies. These
pilot studies are small-scale, preliminary
studies that aim to investigate whether the
blending ratio considered for the feasible
components available in the MAA refinery
to produce BFO as on-specification
very-low-sulfur fuel oil (VLSFO) is stable
for longer periods. Subsequently, the results
and analysis of the trial concluded
that managing blending and stream qualities
is the best way to increase the level of
compatibility in BFO.
This article provides a comprehensive
analysis of VLSFO quality constraints
and the MAA refinery's experience in
VLSFO production.
Bunker fuel-An easy guide. Bunker
fuel dates back to steamships that were
powered by coal. These ships stored
this fuel source in onboard coal bunkers.
While, today, ships have fuel tanks instead
of coal bunkers, these tanks are still
often referred to as bunkers.
Maritime vessels use this bunker fuel to
power their motors. Some water crafts use
diesel (i.e., marine gasoil, which is considered
a low-sulfur fuel oil) as their source of
bunker fuel. However, most commercial
vessels now rely on HFO to generate power
to propel their ships across the ocean.
HFOs can be highly polluting. They are
a component of acid rain, which damages
vegetation and wildlife, and these fuels can
also cause respiratory diseases.
Over recent years, emission control
area (ECA) limits have been gradually reduced
from their initial value of 1.5% sulfur
to 1% sulfur in 2010 and then to 0.1%
sulfur in 2015. The global sulfur limit in
marine fuels was set to 3.5% in 2012. On
January 1, 2020, the International Maritime
Organization's (IMO's) new sulfur
5%
4.5%
4.5%
4%
3.5%
3.5%
3%
2.5%
2%
1.5%
1.5%
1%
0.5%
0%
2008 2009
2010
2011
2012
2013
2014
2015
2016
FIG. 1. The gradual reduction of BFO sulfur specifications.
TABLE 1. Fuel names after IMO sulfur regulation went into effect (January 2020)
Sulfur content
Sulfur ≤ 0.1%
0.1% < sulfur ≤ 0.5%
Sulfur > 0.5%
ULSFO DM
VLSFO DM
HSFO DM*
2017
1.0%
0.5%
0.1%
2018
2019
2020
2021
2022
ECA
Global
regulations banned ships from using fuels
with a sulfur content above 0.5% (FIG. 1).
Today, the utilization of approved
alternative means of emissions reduction-which
are at least as effective as
using compliant fuels-is also permitted.
An exhaust scrubber designed for reducing
sulfur oxide (SOx
) content to the
level required is considered equivalent,
and fuels with higher sulfur content may
still be used on vessels that are equipped
with such a design. The usage of exhaust
scrubbers is limited due to restrictions
in the disposal of washwater, and most
HFO (RM grades) MDO (DMB, DFB) MGO (DMA, DFA, DMZ, DFZ)
ULSFO RM
VLSFO RM
HSFO RM*
*Fuels allowed only for ships with exhaust-reduction technologies yielding SOx
with the respective sulfur limit
reductions equivalent to using fuels
Hydrocarbon Processing | AUGUST 2021 39
Hydrocarbon Processing - August 2021

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