Chemical Engineering May 2020 - 8

to-chip communication can
be increased by a factor of
1,000, according to TUE.
To use light in chips, an integrated
laser is required. The
main semiconductor material
that computer chips are
made of is silicon. But bulk
silicon is extremely inefficient
at emitting light, and so was
long thought to play no role
in photonics. Thus, scientists
turned to more complex
semiconductors, such as
gallium arsenide and indium
phosphide. These are good
at emitting light but are more
expensive than silicon and are
hard to integrate into existing
silicon microchips. The team
will now start creating a silicon
laser to be integrated into
current chips, which could be
realized in 2020.
WHITE SANS TIO2
Titanium dioxide has been
the standard pigment used
for white coloring of lacquers,
paints, and plastics, as well as
of cosmetics, foods, chewing
gum and pills. " Titanium dioxide
has a very high refractive
index, it reflects incident light
almost completely, " explains
professor Hendrik Hölscher of
the Institute of Microstructure
Technology (IMT) at the Karlsruhe
Institute of Technology
(KIT; Germany; www.kit.edu).
" But it is associated with the
drawback that its particles
do not degrade and thus pollute
the environment in the
long term, " says Hölscher.
(Continues on p. 9)
Piloting a new sewage-treatment process to
tackle emerging contaminants
University of Hong Kong
Fe (III)
flocculant
Fe(III)Raw
wastewater
enhanced
primary
sedimentation
(Reduced
loading)
Organic-C
+ O2 → CO2
NH4
+ + O2 → NO3-
NO3
- → N2
Secondary
sedimentation
Treated
effluent
(for reuse)
H2 recovery
Organic- and
P-rich sludge
Acidogenic
membrane
biorector
(A-MBR)
Excessive sludge
(to digestion and
biogas production)
Add-on module
A
s new types of water contaminants
continue to emerge, such as retinoids
and endocrine-disrupting chemicals,
wastewater-treatment techniques are
evolving to economically handle them. One
new process that has shown process against
both conventional and emerging water pollutants
integrates two technologies in tandem
- chemically enhanced primary sedimentation
(CEPS) of sewage and acidogenic fermentation
(AF) of sludge. The process, developed
by researchers at University of Hong
Kong (HKU; www.hku.hk), is being scaled up
at a pilot plant in Shenzhen, China, in collaboration
with the Nanshan Sewage Treatment
Plant. The pilot plant is currently under construction,
and is anticipated to start operations
and testing within the next few months.
In addition to effective removal of pollutants,
the combination of CEPS and AF provides
cost benefits in that it enables the recovery of
salable materials, including phosphorus and
B
8
y replacing part of cement
clinker with calcined (thermally
activated) clay, CO2
emissions
in
cement
organic compounds.
The CEPS portion of the process utilizes an
iron flocculant fed alongside raw wastewater.
The resulting sludge sidestream is then fed to
an acidogenic membrane bioreactor module
for organic hydrolysis (as opposed to digestion,
as in a conventional sewage-treatment process).
Here, a phosphorus product is recovered,
and volatile organic acids are extracted
back into the process. In laboratory tests comparing
the new process to typical sewagetreatment
processes, the combination CEPSAF
system generates cleaner effluent - the
team reported that 65-80% of retinoids were
removed during the CEPS step, with an additional
50% reduction following the AF step,
compared to just 57% reduction using traditional
treatment methods. The pilot plant will
demonstrate the technology's potential to be
retrofitted into existing treatment plants as an
add-on module to further enhance the removal
of both conventional and emerging pollutants.
First industrial-scale plant uses CO2-lean cement production
production
are lowered by up to 40%,
according to thyssenkrupp Industrial
Solutions AG (Essen, Germany; www.
thyssenkrupp-industrial-solutions.
com), which developed the technology
known as " polysius
the
Netherlands)
activated
will
clay. " Cimpor Global Holdings B.V.
(Amsterdam,
use the technology on an industrial
scale at a new plant being built near
the Cameroon sea port of Kribi. Upon
completion in fall 2021, the plant will
save more than 120,000 ton/yr of
CO2 emissions. Thyssenkrupp is carrying
out engineering, procurement,
construction and commissioning of
the new plant, which will produce 720
tons of activated clay per day. It is the
second calcined clay project of Cimpor
Global Holdings.
Carbon dioxide is a natural constituent
of limestone, the main component
of cement. For each ton of cement clinker
produced, around 790 kg of process-related
CO2 is emitted. Around
two thirds of this results from the limestone
used, which releases CO2 in a
chemical reaction in the production
process. At the same time, the process
requires large amounts of energy,
because for the production of cement
clinker, limestone has to be heated with
other aggregates to temperatures of
more than 1,400°C.
With polysius activated clay, thyssenkrupp
has developed a technology
that allows around one third of
the cement clinker to be replaced with
activated clay. The clay is heated to
around 800°C, which is significantly
less heat than is needed to produce
clinker. Thanks to the significant energy
savings in the production of thermally
activated clays and the changed
chemical composition, CO2 emissions
per ton of cement can be cut by up to
40%, says the company.
CHEMICAL ENGINEERING WWW.CHEMENGONLINE.COM MAY 2020
Volatile
organic
acids
Biomass return
Soluble organic stream
for denitrification
P recovery
Excessive sludge (to
digestion and biogas
production)
http://www.hku.hk http://www.kit.edu http://WWW.CHEMENGONLINE.COM
Chemical Engineering May 2020

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