HP March 2022 eBook—Energy Transition - 30

Sustainability
ment of a CO2
capture technology depends on parameters that
include energy demand, cyclic capacity, solvent stability, reactivity,
volatility, environmental sustainability and availability.10
Solvent-based technologies are categorized based on the solvent
used in the CO2
capture process.
Conventional amine absorption process (CAAP). A
conventional amine absorption process applied to the flue gas
(10 kPa CO2
-15 kPa CO2) for CO2
capture using monoethanolamine
(MEA) as a solvent involves absorption at 40°C-45°C
and desorption at 115°C-120°C. An aqueous MEA solution (20
wt%-30 wt%) can achieve a high level of CO2
capture (90% or
more) due to the fast kinetics and strong chemical reaction. The
typical minimum stripper reboiler duties for CAAP are ~3.6 GJ/
metric t-4 GJ/metric t of CO2
captured.11,12
In the solvent-based
process, gas and liquid streams are contacted in a counter-current
fashion. A simplified flow diagram of this process is given in FIG. 1.
One commercial example of a CAAP is Econamine FGSM
(EFG), a Fluor proprietary conventional amine-based technology
used for large-scale, post-combustion CO2
capture. The EFG
technology is the first and most widely applied process that has
extensive proven operating experience in the removal of CO2
from high-oxygen content flue gases. The Econamine FGSM
technology uses a 30 wt% MEA as the absorption solvent, with
chemical inhibitors to counter the effects of corrosion caused by
oxygen in the flue gas. This process is best operated at low levels
of sulfur dioxide (SO2
(< 20 ppmv) to avoid excessive solvent degradation.13
MEA has good rates of CO2
) (< 10 ppmv) and nitrogen oxide (NOx
mass transfer, is low in cost
)
and readily biodegradable but suffers from moderate rates of
oxidative, thermal degradation and moderate levels of toxicity.
It is also corrosive when used at higher concentrations and is
particularly suited to low-CO2
, partial-pressure applications.14
capture and,
The major drawback of such a process is its high energy consumption
of 3.6 GJ/metric t-4 GJ/metric t of CO2
therefore, high operating cost. The capital cost is also quite high
with very tall absorption and desorption towers required for a
high percentage of CO2
capture. Another major difficulty is high
solvent degradation in the presence of oxygen in flue gas, as well
as an excess corrosion rate demanding high metallurgy for both
the absorber and desorber columns.
Flue gas
to stack
Lean
amine
Amine
flow
CO2
absorption
column
Gas
flow
Flue gas
12 vol%-14 vol%
CO2
Rich
amine
Lean
amine
FIG. 1. Schematic of amine-based post-combustion CO2
process.12
capture
Steam
Amine
solvent
heat
exchange/
integration
Solvent
regeneration
column
Item
Gas Source
Process
Absorption liquid
Plant scale
CO2
recovery rate
CO2 concentration
Description
NRG WA Parish power generation plant, 610-MW
(net) coal-fired power generation facility
KM CDR ProcessTM
KS-1TM
solvent
Corresponding to 240 MW
90%
CO2 capture amount 4,776 metric tpd (1.4 MM metric tpy)
11.5 mol%-wet
Hydrocarbon Processing | JUNE 2021 | HydrocarbonProcessing.com
Rich
amine
CO2 to
compression
Hindered amine absorption process. With the potential
of large-scale power plant CO2
mitigation, technology developers-such
as Mitsubishi Heavy Industries (KM-CDR process),
Linde-BASF (OASE blue process) and Carbon Clean Solution
Ltd. (CDRMax™ process)-have begun to optimize chemical
absorbing technologies to reduce the overall operating and capital
costs of CO2
ily on thermal integration of the CO2
capture. The modifications focused are primarcapture
system with the
power plant and development of improved solvent formulations
with lower stripping steam demand, lower solvent circulation
rates than CAAP, and reduced solvent degradation. These process
improvements have the potential to reduce the cost and energy
intensity of post-combustion CO2
30% compared to a conventional amine route.
Recent commercial solvent technologies for CO2
capture by an estimated
capture are
based on the use of hindered amine solvent or blends of amines
with additives to reduce problems related to equipment corrosion,
amine degradation and high energy consumption. Hindered
amine solvents are basically derivative of tertiary amine,
which has greater absorption capacity but lower CO2
mass
transfer rates than sterically unhindered primary and secondary
amines. Blending of hindered amine solvent with additives can
help to overcome the mass transfer problem.
MHI's CO2
capture technology. To overcome the issues of
capture technology called the KM-CDR™
The KM-CDR process can
from a flue gas stream and
CAAP, Mitsubishi Heavy Industries (MHI) has developed a
post-combustion CO2
(Kansai Mitsubishi Carbon Dioxide Recovery) process. It uses
KS-1™ solvent, which has low energy consumption, minimal
solvent loss and low corrosivity.15
capture more than 90% of the CO2
the produced CO2
is more than 99.9% pure. The use of steam
) is lower than CAAP. So far, MHI
The world's largest CO2
capture plants to produce fertilcapture
plant
capture technology by implementin
MHI's KM-CDR technology (0.98 metric t/metric t-1.48
metric t/metric t of CO2
has commercialized 13 CO2
izer, methanol and oil.16
(4,776 metric tpd) on a coal-fired power plant to Petra Nova
Parish Holdings LLC was delivered by MHI in 2016. Details of
the plant are provided in TABLE 1.
MHI improved its CO2
ing a new system into the KM-CDR process. Three of the major
improvements are:
1. A load adjustment control system that helps maintain
smooth operation for the dynamic flue gas changes in
the host coal-fired plant. This allows the desired CO2
TABLE 1. Outline of CO2
in Texas, U.S.18
capture plant for EOR project
http://www.HydrocarbonProcessing.com
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