Hydrocarbon Processing - October 2021 - 47

Sustainability
H. Z. HA, Fluor Canada Ltd., Calgary, Alberta,
Canada; and P. M. MATHIAS, Fluor Corp.,
Aliso Viejo, California
Rigorous modeling of CO2
emissions,
carbon capture and reduction are receiving increased attention
from a variety of process industries, especially power generation
and oil and gas exploration and production. One way to
capture carbon is to remove the CO2
the absorption solvent to remove CO2
absorbers
using potassium carbonate solutions
As part of the global campaign to reduce CO2
from flue gas resulting
from the combustion of fossil fuels. The hot potassium carbonate
(HPC) process is one of the major commercialized processes
for CO2
removal. Potassium carbonate has been used as
from flue gas for more
than 70 yr. At present, there are two commercialized technologies
for CO2
removal with HPC aqueous solutions: the Benfield
and CATACARB processes.
The Benfield process, which was introduced by Benson,
Field et al. in the 1950s, uses hot carbonate solutions as the
chemical solvent to capture CO2
of the Benfield Process is CO2
reforming (SMR) process for H2
. The process employs highpressure
absorption and low-pressure desorption. The technology
was licensed by UOP as the Benfield Process, with over
700 units in commercial service to date.1
A typical application
removal in the steam methane
production.
Meanwhile, Eickmeyer and Associates Inc. have commerplant
applications since the early 1960s. The CATA,
natural gas and ethylene
cialized CATACARB, an enhanced HPC system for ammonia
and H2
CARB process has been designed for more than 150 plants in
over 30 countries, and for a wide range of applications, with the
most common being ammonia, H2
oxide plants.1
With the advances in process simulations, rate-based column
modeling has become more accessible and has potential
applications in column design optimization and operation
guidance. The rate-based, rigorous modeling is frequently used
in gas absorption processes, in contrast to conventional equilibrium
modeling. One company has offered the rate-based
column model framework for CO2
in its proprietary softwarea since 2008.2,3
capture by K2
Borhani et al.4
CO3
or AMP
utilized the rate-based model in this softwarea
to simulate the diethanolamine (DEA)-promoted HPC process.
An acceptable agreement was found between model predictions
and the industry-measured data. The rigorous model
was further used to predict the optimum operation points
where the absorber performs best.
Solos et al.5
demonstrated that rate-based absorption modeling
is a powerful tool for simulating and designing chlorine
Feed gas
Steam
Rich solvent
Lean pump
Reboiler
FIG. 1. CO2 removal with hot potassium carbonate system.
Hydrocarbon Processing | OCTOBER 2021 47
drying columns using sulfuric acid, as it can provide fundamental
insight for the effect of equipment variables.
Mathias and Gilmartin6
studied the effect of chemical equilibrium
and reaction kinetics on the rate-based model performance
of the CO2
capture process with uncertainty analysis, using
perturbation theory. They demonstrated that the rate-based
model performance can be quantitively analyzed, thereby generating
a reliable method for model validations. Utilizing a ratebased
rigorous model not only can provide more cost-effective
design with more accurate estimation of column performance,
but also can offer opportunities to optimize column operation.
This article performs rate-based, rigorous modeling using a
of the previously discussed proprietary modeling softfeatureb
warea
via detailed kinetic models. The mass transfer correlations
for packings available in the simulator are evaluated with model
performance and compared with available industry data. The
best-detailed and most rigorous model parameter set is selected
and used for model predictions and optimizations.
HPC absorption process. The HPC absorption process includes
two major columns: the absorber and the regenerator.
The process flow scheme is illustrated in FIG. 1.
Both columns operate at similar temperatures (around
100°C). Absorption occurs at higher pressure (10 bar-50 bar),
and CO2
is desorbed in the regenerator at 1 bar-2 bar. Compared
to amine solutions, the K2CO3 solution (typical 15%-40%
Rich CO2
Clean gas
Lean solvent
Absorber
Lean/rich
exchanger
Regenerator
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