Hydrocarbon Processing - January 2022 - 44

Carbon Capture/CO2
Mitigation
one must consider the potential
adverse environmental effects
resulting from the disposal process.
concerns and other issues).
Resultant litigation and delays
could render the project
Company executives and safety/risk managers see
the need for a rapid but risk-managed transition to
low-carbon or zero-carbon technologies. The need
for such a transition merits careful consideration;
therefore, the long-term success of CO2
Numerous approaches are available
for amine disposal, including
physical (membrane), chemical
or biological treatments. Each
of these processes have benefits
and challenges. Regardless, the
goal is to minimize the overall
environmental impact.
* Liquid or solid sorbent
sensitivity to chemical species
in the flue gas, such as oxygen,
nitrogen oxides (NOx
) and
sulfur compounds: For example,
some sorbents may be too sensitive
to sulfur or sulfur derivatives and
may require sulfur removal in the
flow conditioning step (FIGS. 1 and
2). This will add to the project's
cost. In addition, particulates
from flue gas could cause plugging
problems, operational challenges
and low productivity.
* Amine emissions could pose
multi-phase environmental
issues: Amine emissions can
affect air quality and cause water
pollution (as rainwater will dissolve
amines), which can lead to soil
contamination problems. Similarly,
environmental systems must
be robust enough to handle
amine and byproduct spills.
* Acceptance from communities:
Despite well-intended efforts to
improve the environment, CO2
capture projects can receive a tepid
response or even fierce resistance
and/or legal challenges from
nearby communities if their
concerns are not addressed
adequately (such as regarding
noise levels and traffic during
construction, long-term noise
levels, amine emissions, odor
44 JANUARY 2022 | HydrocarbonProcessing.com
Improving operations to minimize
CO2
erations at high levels of excess air will
increase flows through the
CO2
capture process and
capture projects
requires focused attention on strategic and tactical issues.
unsustainable and could generate-
in the short term-public concern
or distrust about a company's
environmental stewardship.
* Operational upsets: In the event
of an operational upset that results
in unburnt hydrocarbons in flue
gas, the CO2
capture plant could
spread a flammability hazard over
a wide area. Control philosophies
should address this hazard, along
with similar plant upset issues.
* Flue gas CO2
lead to suboptimal operations,
while scant excess air
could cause unsafe conditions.
Optimizing the operation
of upstream equipment
will
improve CO2
of CO2/Btu (the amount of CO2
capture and enhance overall
productivity. In addition,
switching to fuels that
generate lower amounts
produced
per Btu of heat release) will help
lower the size of the CO2
capture equipment.
For example, the amount of CO2
released per MMBtu of heat output for
natural gas is approximately 40%-50%
lower than that generated by fuel oils,
such as diesel. However, this option may
not be viable for brownfield projects.
concentrations and
effective absorption: Depending
on the source, CO2
. Flue gas in
concentrations
in flue gas vary. For example, gas
turbine flue gases typically contain
3 vol%-4 vol% CO2
gas-fired heaters or boilers has CO2
levels of 8 vol%-10 vol%, and fueloil-fired
boilers have even higher
CO2
of CO2
levels. Low concentrations
mean a lower driving force
for absorption and may require
higher concentrations of amine.
Plants must establish an operating
window for CO2
concentrations.
* System integration: Although
instrument and control system
vendors have made significant
efforts to interoperability, at the
plant level, personnel must spend
a considerable amount of time
and resources to ensure smooth
operations. For example, if the
distributed control system (DCS) is
provided by X and the CO2
capture
vendor has its system based on
DCS Y, then data protocols must
be addressed carefully. Inadequate
consideration of DCS alignment will
cause recurring data-management
issues, along with operational and
safety problems.
Long-term considerations. The CO2
capture plant/project lifespan may be
25 yr-30 yr; therefore, it requires some
thought on several broad issues. Some of
the issues may not be easily manageable
or even amenable to quantitative analysis;
nonetheless, decisions must be made
in the face of volatile information. Several
of these issues include:
* Supply chain robustness and
CO2
markets: As with any project
or plant operations, supply chain
reliability is crucial. Similarly,
demand for CO2
will impact
operating rates and emissions.
* Stability of disposal contractors:
Implicit requirements of solid
waste disposal and Resource
Conservation and Recovery Act
(RCRA) regulations include an
assessment of a waste disposal
contractor's financial stability; the
same will apply for waste disposal
from CO2
capture projects.
* Environmentally advanced
technology suppliers: The
move toward environmentally
responsible processes and
technologies will continue.
In selecting any technology,
one should identify segments
that are problematic from an
environmental sustainability view,
such as high solvent or adsorbent
formation. Furnace or boiler op
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