Chemical Engineering March 2016 - 8

Dissolving pulp is a pulp
manufactured by enhancing
the purity of cellulose, the
main component of wood.
The term generally refers to
pulp with a cellulose content
of 90% or greater, compared
with about 85% for pulp for
general paper manufacturing.
Dissolving pulp is mainly
used as feedstock for rayon
or acetate that is used in
applications such as clothing,
and demand for the
substance is expected to
increase in the future.
Bio-gasiFicaTion
Researchers at Southern
Illinois University (SIU; Carbondale,
Ill.; www.siu.edu)
are developing microbial
processes to convert coal
into methane. The team
has developed strains of
bacteria and archaea that
consume coal and excrete
methane, and is looking at
how to apply them to waste
coal leftover from mining
operations, as well as to
in-situ coal, such as material
left in abandoned coal
mines. The researchers say
the microbes and associated
processes could allow
the harvesting of methane
from areas where the coal
is " unmine-able " for various
reasons, such as poor
quality, small seams, or
dispersed distribution of
coal. More than 200 species
were identified from
samples taken from water
surrounding coal deposits.
The researchers then applied
various techniques to
stimulate the microbes' production
of methane.
recycling Brine
Covestro AG (Leverkusen,
Germany; www.covestro.
com) is testing a new process
for recycling saline
process wastewater that is
generated in the production
of polycarbonate, a highperformance
plastic. A pilot
plant for the process, located
at the Krefeld-Uerdingen
site in Germany, was
opened last month.
The current project at Cove(Continues
on p. 10)
8
Monetizing coke-oven gas, while capturing CO2
Chemical reaction
Crystallization
Acid gas from
desorption
(1,000 Nm3/h)
Tailgas to
Claus plant
Centrifugation
Drying
Purge back to
desorption
thyssenkrupp Industrial Solutions
A
process that converts process
gases, generated during the production
of metallurgical coke, into
marketable chemicals is being developed
in a pilot plant installed on the works
site of thyssenKrupp Steel Europe AG (www.
thyssenkrupp-steel-europe.com) in Duisburg,
Germany. The process is being developed
in a collaborative project by the Schwelgern
coke plant (KBS), plant-engineering company
thyssenKrupp Industrial Solutions AG (Essen;
www.thyssenkrupp-industrial-solutions.com)
and Berlin Technical University (TU Berlin; all
Germany; www.tu-berlin.de).
In the conventional treatment of coke-oven
gas (COG), H2S and NH3 are scrubbed from
COG with aqueous ammonia solutions (deacidified
water, stripped water) by the CyclaSulf
process. The rich absorption solution
(enriched water) is pumped to the regeneration,
H2S/NH3-desorption column. The head
product of the H2S/NH3-desorption is acid
gas, which is rich with H2O, NH3 (20-30
vol.%), CO2 (15-25 vol.%) and H2S. The rate
of H2O, NH3 and CO2 in acid gas is nearly
equimolar, which makes it possible to synthesize
crystalline ammonium bicarbonate.
In the new, patented process (flowsheet),
the acid gas from the CyclaSulf process is
first compressed (by acid-gas-condensate
jet flow) in a jet ejector, where a spontaneous
condensation of H2O and NH3 takes place.
The gas-liquid mixture flows directly from
the ejector through a falling film apparatus,
in which selective conditions accelerate the
1,000 kg NH4HCO3
chemical absorption of CO2 by NH3. The
condensate flows to a vessel, and the gas
(mostly CO2, H2S and HCN) is directed to the
Claus plant or the sulfuric-acid plant. In the
collecting vessel, the absorbed CO2 reacts
further to HCO3
-, and the NH3 to NH4
+. The
condensate in the collecting vessel, which
is produced under specific reaction conditions,
is an under-saturated mother liquor of
NH4HCO3. As the mother liquor is fed to the
crystallizer, a decrease in temperature causes
the NH4HCO3 to crystallize and precipitate
from the solution. The suspension is then
centrifuged and the crystalline NH4HCO3
dried to achieve the final product quality.
With the pilot plant, 95% of the ammonia
contained in the COG can be utilized, producing
15 kg/h of solids from 15 Nm3 of acid gas
and 2 Nm3 of CO2. A commercial plant - for
example a medium-sized coke plant with a capacity
of 150,000 Nm3/h COG and a concentration
of 6 gr/Nm3 ammonia in COG - could
produce 4.2 ton/h of NH4HCO3, in addition to
the other byproducts produced (tar, COG, sulfur
and benzene, toluene and xylenes).
The end products can be put to a range of
uses, such as nitrogen fertilizers, propellants
and foaming agents for plastics or porous
ceramics, and also in the food industry (baking
soda). Although the process economics
have to be evaluated individually for each
coke plant, some samples of byproduct
plants that have been economically analyzed
have shown a return on investment after 3-5
years, say the companies.
Collaboration lowers cost for
bio-based FDME process
A
partnership between DuPont Industrial
Biosciences (Wilmington, Del.;
www.dupont.com) and Archer Daniels
Midland Co. (ADM; Chicago, Ill.;
www.adm.com) has developed a less costly
and more efficient process for producing
bio-based furan dicarboxylic methyl ester
(FDME) from the six-carbon sugar fructose.
Applications for the renewable material could
be in packaging, textiles, high-performance
plastics and others, the companies say.
FDME is a high-purity derivative of furandicarboxylic
acid (FDCA), one of 12 building
blocks identified by the U.S. Dept. of Energy
that can be converted into a number of highvalue,
bio-based chemicals. Despite considChemiCal
engineering www.Chemengonline.Com marCh 2016
http://www.siu.edu http://www.thyssenkrupp-steel-europe.com http://www.thyssenkrupp-industrial-solutions.com http://www.tu-berlin.de http://www.covestro http://www.dupont.com http://www.adm.com http://www.Chemengonline.Com
Chemical Engineering March 2016

Table of Contents for the Digital Edition of Chemical Engineering March 2016
