PEC12-25 CAPEC-PROCESS Industrial Consortium ... - DTU Orbit

Two different pilot plant configurations of the airlift reactor technology were tested in nine
fermentations. The headspace pressure was varied between 0.1 and 1.1 barg and the
superficial gas velocity in the airlift riser section was varied between 0.02 and 0.06 m/s.
The biological model developed in the stirred tank reactor was shown to apply to the airlift
reactor with only small modifications: The mass transfer of oxygen in the airlift reactor was
studied and a mass transfer correlation containing the superficial gas velocity and the
apparent viscosity of the fermentation broth was shown to describe the experimental data
well. The mass transfer rate was approximately 20% lower than the literature data for airlift
reactors. Mixing in the pilot scale airlift reactor was also studied. As the mixing time was of
the same order of magnitude as the characteristic time for oxygen transfer, mixing could
also be limiting the process at that scale. The process model for the airlift reactor was also
shown to describe the experimental data well for a range of process conditions.
A cost function for oxygen transfer including the equipment cost and running cost for
nutrients and electricity was developed for both the stirred tank reactor and the airlift
reactor. The cost function was used to identify an optimum range of reactor configuration
and process conditions for industrial scale enzyme production fermentors. It was shown
that compared to the stirred tank reactor 22% of the electricity cost might be reduced for the
airlift reactor, and the capital cost might also be somewhat lower. However, since the
electricity cost is a relatively minor part of the total cost, there might currently not be an
obvious fiscal motive to change technology. The cost of nutrients is considerably larger
than the electricity cost and was shown to be independent of the technology and process
conditions. If the cost structure changes in the future and the airlift reactor is chosen as the
alternative production technology, suggestions on the practical scale-up procedure are
given. These include the use of Computational Fluid Dynamics (CFD) and scale-down
models of the production environment.
5.1.11: Yuan Xu, 2012, “Process Technology for Immobilized Lipasecatalyzed Reactions”
Ph.D. thesis (PROCESS)
Biocatalysis has attracted significant attention recently, mainly due to its high selectivity
and potential benefits for sustainability. Applications can be found in biorefineries, turning
biomass into energy and chemicals, and also for products in the food and pharmaceutical
industries. However, most applications remain in the production of high-value fine
chemicals, primarily because of the expense of introducing new technology. In particular
lipasecatalyzed synthesis has already achieved efficient operations for high-value products
and more interesting now is to establish opportunities for low-value products. In order to
guide the industrial implementation of immobilized-lipase catalyzed reactions, especially
for highvolume low-value products, a methodological framework for dealing with the
technical and scientific challenges and establishing an efficient process via targeted scaledown
experimental work is described in this thesis. The methodology uses economic
targets to test options characterized via a set of tools.
In order to validate the methodology, two processes based on immobilized lipase-catalysis
have been studied: transesterification and esterification of vegetable oils for the production
of biodiesel. The two processes are focused on the conversion of the two main components
of vegetable oil materials, glyceride esters and free fatty acids respectively, into fatty acid
alkyl esters. Although biodiesel is conventionally prepared via chemical-catalyzed
transesterification of vegetable oils with methanol to produce fatty acid methyl esters
(FAME), this work has been focused on the production of fatty acid ethyl esters (FAEE)
with bioethanol due to the expected improved sustainability of this type of biodiesel.
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