Chemical Engineering August 2020 - 6

RO-303
paper for stickers, labels and
adhesive tapes. Additionally,
they work for release films
and manufacturing process
release liners and a myriad of
other applications.
MAKING SPIDER SILK
Spiders produce strong and
lightweight threads called
draglines that are made from
silk proteins. Although such
silks can be used to manufacture
a number of useful materials,
getting enough of the protein
is difficult because only a
small amount can be produced
by each spider. In a new study
published in Communications
Biology, a research team, led
by Keiji Numata at the Riken
Center for Sustainable Resource
Science (CSRS; Yokohama,
Japan www.riken.jp),
reported that they succeeded
in producing the spider silk
using photosynthetic bacteria.
This study could open a new
era in which photosynthetic
bio-factories stably output the
bulk of spider silk.
The CSRS researchers focused
on the marine photosynthetic
bacterium Rhodovulum
sulfidophilum. This bacterium
is ideal for establishing a sustainable
bio-factory because
it grows in seawater, requires
CO2 and N2 from the atmosphere,
and uses solar energy,
all of which are inexhaustible.
The bacterium was genetically
engineered to produce MaSp1
protein, the main component
of the Nephila spider dragline,
which is thought to play an important
role in the strength of
the spider silk. Optimization of
the gene sequence that they
inserted into the bacterium's
genome was able to maximize
the amount of silk that could
be produced. They also found
that a simple recipe - artificial
seawater, bicarbonate salt, N2
gas, yeast extract, and irradiation
with near-infrared light -
allows R. sulfidophilum to grow
well and produce the silk protein
efficiently. The surface and
internal structures of the fibers
produced in the bacteria were
found to be very similar to those
produced naturally by spiders.
F-T SYNTHESIS
Even though more than one
hundred years have passed
(Continues on p. 8)
6
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM
AUGUST 2020
A step toward supercritical-CO2 power generation
Natural gas
C
onstruction is complete
on a new building to
house a fully integrated
electricity-generating
power plant that will demonstrate
operability and performance of a
10-MW power-generation facility
using supercritical carbon dioxide
(sCO2) as the working fluid in
a Brayton thermodynamic cycle.
Known as the STEP (supercritical
transformational
electric
power)
Demo project, the pilot-plant test
facility is located on the property
of Southwest Research Institute (San Antonio,
Tex.), one of the STEP team members,
along with project-leader GTI (Des Plaines,
Ill.; www.gti.energy), GE Research (Niskayuna,
N.Y.), and the National Energy Technology
Laboratory (Morgantown, W.Va.).
The sCO2 cycle (diagram) offers significant
potential benefits in efficiency, cost and
environmental performance over the steam
Rankine cycle, a common method for producing
electricity currently. Above its critical
point, CO2 has properties of both a gas and
liquid. " In a Rankine cycle, you have a liquidvapor
phase change, " explains John Marion,
GTI senior program director. " In a Brayton
cycle with sCO2, there is no phase change
- sCO2 behaves like a gas, but it's noncompressible
like a liquid - and that allows
overall cycle efficiencies of over 50% (2 to 5
percentage points higher than steam Rankine),
and allows the turbomachinery components
to be 10 to 30 times smaller than
those for Rankine cycles. " These attributes
result in a levelized cost of energy that is
3-4% lower than with steam cycles.
The objective of the STEP Demo is to integrate
all the elements required for a gridQ
uesTek
Innovations LLC (Evanston,
Ill.; www.questek.com)
has introduced a stainless-steel
powder designed for additive
manufacturing (AM; 3D printing) that allows
complex, high-strength parts to be made
without the need for expensive post-treatments,
such as cryogenic processing or
high-temperature heat treatment. Designed
for powder-bed fusion 3D printing, the new
powder overcomes the poor and variable
properties observed when using 17-4 steel
(17% Cr; 4% Ni) in 3D printers.
Dana Frankel, QuesTek Manager of Design
and Product Development says " With
QuesTek's QT 17-4 powders, a fully martensitic
microstructure is achieved in the
as-printed condition. The high-temperature
Blower
Generator GB
Power for
compressor
motors
Load
bank
connected
commercial
powergeneration
CO2
700∘‒
HT
Turbine
HT
Recup
LT
Recup
Cooler
Electric
Comp
motor
Cooling
water
plant, which has not been done previously,
although sCO2 Brayton cycles have been
used in smaller, niche applications. Major
equipment components have been fabricated
and delivered for assembly.
Recent advances in materials and turbine
modeling have allowed the Brayton sCO2
cycle in a practical system for power generation,
says Don Stevenson, GTI vice president of
energy supply. In order to realize the efficiency
gains with the sCO2 Brayton cycle, the system
needs to operate at high (500-700°C) temperatures,
which necessitates materials that can
withstand the temperatures, for example.
Other technological advances developed
and built for the STEP Demo project include
high-temperature, printed-circuit heat recuperators,
a monolithic turbine rotor and the
application of dry gas seals for the turbine
and compressor, Marion says.
The STEP project leaders anticipate commissioning
and testing the pilot
facility
Stainless-steel alloy for additive manufacturing
solution heat-treatment process, required
for conventional 17-4, is not needed for
QuesTek's alloys, and the resulting properties
have less variation. " The corrosion
resistance and fatigue performance of AM
alloys made from these powders is equivalent
or improved over AM material printed
using commercially available 17-4 powders,
QuesTek says.
The company's new powders can be
used in a wide range of industries, including
aerospace, defense, medical, chemical
processing and energy. QuesTek is in discussions
with commercialization partners,
including alloy producers, metal AM machine
manufacturers and service bureaus to
license these technologies and accelerate
commercial adoption.
in
summer 2021. It is funded by the U.S. Department
of Energy and by industry partners.
Ros
ma
con
Ed
Eng
Em
Electric
motor
Comp
STEP Demo
04_CHE_0820_Chementator_p05-09.indd 6
7/21/20 9:21 AM
http://www.gti.energy http://www.riken.jp http://www.questek.com http://WWW.CHEMENGONLINE.COM
Chemical Engineering August 2020

Table of Contents for the Digital Edition of Chemical Engineering August 2020
