Authors: Jeremy Anderson1, James Lockhart1, Jim Wearing1, David Genders2, Peter Symons2, Erika Milligan2
1 NORAM Engineering & Constructors Ltd. Vancouver, Canada
SUMMARY
Applications for Cellulose Nano Crystals (CNC) are
being developed, resulting in greater demand for highquality
CNC. NORAM Engineering & Constructors Ltd. and
its partners have developed two improvements to the wellknown
acid hydrolysis pathway: a continuous reactor using
compressed pulp to improve reaction uniformity and reduce
the acid:pulp ratio required to achieve adequate wetting,
and the use of electrodialysis and ion exchange for sulfate
removal from CNC suspensions.
Pulp is compressed, resulting in a higher pulp density.
The compressed pulp exhibits rapid wicking of the acid,
resulting in a uniformly wetted reaction mixture with ~3x
less total acid usage and far less mixing energy required. The
mixture is pumped continuously through a reactor where
the required residence time at temperature is maintained
until the reaction of the pulp fibers into CNC is complete.
By completing the reaction with less acid, the downstream
washing and neutralizing steps are greatly reduced.
In order to purify CNC, dialysis is often used to wash out the
remaining sulfuric acid and other soluble impurities. However,
the dialysis process requires very large quantities of water to
adequately remove the acid. NORAM and Electrosynthesis have
demonstrated the use of bi-polar electrodialysis combined with
ion-exchange resins to selectively remove sulfuric acid from
the CNC solution, even at very low residual levels of acid. The
power requirements for this process are linear with the acid to be
removed, unlike dialysis which experiences logarithmic drops in
washing effectiveness as the acid concentration decreases.
These process improvements have the potential to
decrease the capital and operating costs of a CNC production
facility, making it easier for pulp producers to pivot into this
new and exciting industry.
Keywords: Cellulose Nano-Crystal, Acid Hydrolysis,
Continuous Reactor, Electrodialysis, Pilot Plant