Chemical Engineering March 2023 - 6

Integrated capture and conversion of CO2 to methanol
P
rocesses that capture carbon dioxide from industrial
fluegas and simultaneously convert it
into useful chemicals are desirable because
they offer an opportunity to produce CO2derived
chemicals more efficiently and economically
than conventional approaches, where costs are driven
up by the energy-intensive regeneration of the capture
solvent. By integrating CO2 capture with conversion to
methanol (flowsheet), scientists at Pacific Northwest
National Laboratory (PNNL; Richland, Wash.; www.
pnnl.gov) have developed a process that could eventually
reach cost parity with producing methanol derived
from fossil fuels, the PNNL team says.
For the CO2 capture component, the team used
2-EEMPA (N-(2-ethoxyethyl)-3-morpholinopropan1-amine),
an advanced, water-lean, amine-based capture
solvent. To produce methanol, the CO2-containing
solvent is exposed to a catalyst that consists of platinum
metal atoms on a titanium-oxide support. The heterogeneous
catalyst allows a reaction pathway that avoids
methylation (and thus deactivation) of the capture solvent.
Other catalysts used for methanol synthesis in the
gas phase tend to deactivate the capture solvent by promoting
a route that methylates the amine site.
With an integrated capture and conversion process,
the exothermic CO2-to-methanol conversion process
partially offsets the energy that would normally be required
in conventional carbon capture and utilization for
the regeneration of the capture solvent, the PNNL team
explains. Further, " because the captured CO2 is converted
directly in the capture-solvent medium, there is
also energy saved on the CO2 compression and transportation
that would otherwise be required with gasphase
conversion, thus reducing additional energy inputs
and associated equipment costs, " PNNL says.
The PNNL research, reported in the journal Advanced
Energy Materials, includes a technoeconomic analysis
(TEA) of capturing CO2 from a natural-gas combinedcycle
power plant and converting it to methanol in the
condensed phase. The TEA suggests that the minimum
selling price for methanol can be significantly reduced,
and may reach price parity with conventional
methanol synthesis, if faster kinetics and higher selectivity
can be achieved through catalyst and reactor development.
Current efforts are focused in those areas,
the PNNL team says.
PNNL
A new way to improve valve resiliency against flashing
F
lashing occurs when the pressure of a fluid passing
through a valve is lower than the same substance's
vapor pressure. This causes the fluid
to boil - otherwise known as " flashing. " " By reducing
flow capacity and eroding the valve itself, flashing
causes unplanned maintenance, reduced reliability
and critical safety risks, " says Mike Semens-Flanagan,
Global Engineering Director at IMI Critical Engineering
(Birmingham, U.K.; www.imi-critical.com). The company
has therefore developed a new valve enhancement technology
called EroSolve Flashing, which aims to protect
angle and globe valves against leakage and other issues
caused by steam flashing. The EroSolve solution
prevents low-travel operation and moves the fluid-path's
vena contracta downstream of the seating area of the
valve, effectively protecting it against any damage. It also
gradually reduces pressure through the introduction of
special multi-path, right-angle-turned flow passages that
prevent sudden acceleration of fluid velocity.
In angle valves, hardened trim material and an enhanced
seat-plug design move flashing away from vital
6
trim parts, and enable the valve to withstand severe
conditions. The EroSolve variant designed for globe
valves employs a seat basket that creates backpressure
to reduce downstream velocity and pressure drop
to avoid damage to the valve body - without requiring
any piping modifications.
According to the company, this is the first dedicated
and successfully demonstrated valve technology on the
market aimed at mitigating problems related to flashing.
EroSolve Flashing has been demonstrated in a combined-cycle
power plant that had experienced erosion
in its heat-recovery steam generators (HSRGs). Following
the installation of valves equipped with EroSolve
technology, there was no component damage reported
after a year. In another demonstration, EroSolve valves
were installed at a chemical plant in South Korea to replace
boiler blowdown valves whose trim had not been
specified for flashing conditions. The new valves are
expected to last 2 to 4 times longer than the previous
valves, resulting in a significantly lower cost of ownership,
says the company.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
MARCH 2023
http://www.pnnl.gov http://www.pnnl.gov http://www.imi-critical.com http://WWW.CHEMENGONLINE.COM
Chemical Engineering March 2023

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