HP March 2022 eBook—Energy Transition - 76

Special Focus Plant Safety and Environment
S. SINGH and R. MUKHERJEE, Engineers India Ltd.,
Gurugram, India
Are furnace emissions proving to be your
Achilles heel?
Furnaces, or fired heaters, provide the source of heat required
for major industrial processes. As an energy-intensive
industry, oil refining employs furnaces in most modern refinery
process units. The prime source of heat in furnaces is fuel
oil or fuel gas that is normally generated within the refinery;
these are essentially anthropogenic sources of carbon. The carbon
in these fuel sources ultimately ends up in the atmosphere
in the form of carbon dioxide (CO2
), a major pollutant and recognized
as a prime greenhouse gas (GHG).
The planet has been reeling with increasing global temperatures
that are poised to create havoc if the present rate of
temperature rise continues unabated. As per COP21 (Conference
of Parties, Paris Agreement 2015), a concerted effort is
being adopted to reduce carbon emissions to limit the global
temperature rise within 2°C above pre-industrial levels-more
specifically, targeting all efforts to limit the temperature rise
within 1.5°C.
Without a doubt, the task is difficult considering the climate's
antagonistic relationship with economic and financial
parameters. However, carbon emissions reduction and carbon
capture and sequestration (CCS) initiatives, as detailed in the
Paris Agreement, are progressive steps toward sustainable and
green development.
As part of this larger initiative, refinery furnaces have their
own role to play. Furnaces are one of the largest polluters in
terms of CO2
emissions, and the rate of carbon emissions is
directly proportional to the type of fuel being fired. Therefore,
any reduction in rate of fuel fired is amplified multiple times
into the reduction in CO2
sands of metric tons of CO2
emissions. Considering that thouare
emitted per year from a largescale
refinery, the emissions issue can become any refinery's
Achilles heel in the decade to come as climate initiatives invariably
gain momentum.
As the voices against carbon emissions grow louder, excellent
progress is being made on this front with some valuable literature.1,2,3,4
However,
most of these documented studies focus
on the reduction in carbon emissions on a pan-refinery level.
Literature with respect to the impact of optimization at the
grassroots level or equipment level is scarce. This article has
been framed considering this, as well as the impact of carbon
reduction strategies in quantitative terms on a furnace of appreciable
heat duty. This work also explores the magnitude of
carbon emissions reduction that can be achieved by common
yet easy-to-implement strategies.
Furnaces and their tryst with emissions. Both basic
sources of fossil fuels in fired heaters-fuel oil or fuel gas
that is generated internally within the refinery-are rich
sources of carbon and generate approximately 9,500 Kcal/
kg-12,000 Kcal/kg (kilocalories/kilogram) of energy of the
fuel burnt. However, each kg of fuel combusted generates approximately
18 kg-20 kg of flue gas: nearly 15%-20% of flue
gas mass is CO2
proximately 3 kg-3.5 kg of CO2
.
. Effectively, each kg of fuel oil generates ap,
whereas common refinery
fuel gas generates approximately 2.5 kg-2.7 kg of CO2
While evaluating carbon reduction strategies for furnaces,
it is imperative to review the strategies adopted on a pan-refinery
level and then extend them to furnaces. It is unanimously
agreed that the path to carbon reduction is defined by on the
following three pillars:
* Efficiency improvements and process intensfication
* Fuel substitution and feedstock management
* Carbon capture, utilization and storage (CCUS),
end-of-pipe solution.
Extending these three pillars to a refinery furnace, proven
and time-tested techniques exist that can be covered under
the first two categories (i.e., efficiency improvements and fuel
substitution). However, the end-of-pipe solution of CCUS remains
to be proven on a commercial scale.
While it is well-accepted that CCUS provides a significant
reduction in carbon emissions, multiple factors stand as roadblocks
between easy implementation on common refinery furnaces.
For example, a standard crude refining facility consists
of some 30-35 furnaces scattered across various points in the
refinery-no " single point source " of emissions exists where
CCUS can be planned, unlike power plant or fertilizer plant
furnaces where CCUS is easier to implement. Moreover, the
sulfurous content and the oxygen content of the flue gas are
captured to act as a hindrance for the amine-based reagent that
forms the heart of CCUS processes.
Even if these challenges are overcome, the utilization component
in CCUS is a major chink in the armor for a refinery.
Common utilization strategies include injecting CO2
for enhanced
oil recovery or for methanol generation, both of which
are dependent on geographical proximity to the end user, as
well as on prevailing markets for the end products.
It was decided to focus this study on the first two well-proven
options: energy efficiency improvement and fuel substitution.
CCUS has been kept beyond the scope of this article; however,
Hydrocarbon Processing | OCTOBER 2021 | HydrocarbonProcessing.com
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HP March 2022 eBook—Energy Transition

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