(634f) A VSA Process Cost Benchmark for Post-Combustion Carbon Capture from Wet Flue Gas Under Variable Economic Conditions

A VSA Process Cost Benchmark for
Post-Combustion Carbon Capture from Wet Flue Gas under Variable Economic
Conditions

Mark Purdue,^1,2 Shamsuzzaman
Farooq^1,2

¹ Department
of Chemical and Biomolecular Engineering, National University of Singapore, Singapore
117585

² Cambridge
Centre for Advanced Research in Energy Efficiency in Singapore (CARES), CARES
at CREATE Tower. #05-05, 1 CREATE Way, Singapore, 138602

The levelized cost of
electricity generation in fossil fuel power plants equipped with carbon capture
technology is an essential factor to consider for reducing human-induced global
warming due to the cumulative CO₂ emissions in the atmosphere. Adsorption
technology is a leading contender to reduce the cost of flue gas separation to
meet new emission regulations. An accurate economic assessment of adsorption
processes requires reliable gas-solid mixture equilibrium data and a validated
process simulation model. A pre-requisite for a successful flue gas separation
is high adsorbent selectivity of CO₂ over N₂ which should
be maintained or enhanced under humid gas conditions for a successful single
stage process. A computationally inexpensive non-linear multicomponent
adsorption isotherm model is also desirable. A techno-economic evaluation of a
two-stage VSA process with light product pressurization (LPP) for carbon
capture and concentration (CCC) is presented here using experimental and
molecular simulation equilibrium data between 25^oC and 75^oC
for CO₂/N₂/H₂O mixtures on Silica Gel and 13X
Zeolite to establish a baseline VSA cost with commercial adsorbents.

A dual adsorbent, two-bed,
four-step VSA process with industrially practical vacuum levels is considered for
continuous production of a concentrated stream of CO₂ for storage or
downstream utilization. Two moisture capture (MC) packed columns are positioned
upstream to guard two carbon capture (CC) packed columns. A non-isothermal
non-isobaric linear driving force model of the two-stage process was developed and
discretized using the weighted essential non oscillatory (WENO) finite volume
method. The resultant system of ordinary differential equations (ODEs) are
solved in Fortran. The process is optimized for minimum cost subject to 95% purity
and 90% recovery constraints. Optimization is performed on the CC columns
first, with relative humidity (RH) of the CC column gas feed varied initially.
With a required exit RH from the MC columns to feed the CC columns, the MC
column arrangement is optimized within the process. Cost benchmark parameters
associated with a variation in future fuel prices, CO₂ storage cost,
potential CO₂ feedstock price, weighted average cost of capital and
taxation policies are introduced. This parameterized VSA cost benchmark
can demark new adsorbents and processes with different capital expenditures under
selected economic conditions. Future research shall validate the simulation
model and the VSA cost benchmark for CCC from wet flue gas.