In the following:
The DOI (Digital Object Identifier) link for this article is http://dx.doi.org/10.1002/apj.106.
The DOI (Digital Object Identifier) link for this article is http://dx.doi.org/10.1016/j.aml.2007.08.014.
The DOI (Digital Object Identifier) link for this article is http://dx.doi.org/10.1016/j.cej.2007.11.035.
Abstract
Many industrial processes produce wastewater containing pollutants,
the concentration of which must be reduced
before the wastewater can be discharged. One way to do this is through the
use of a biological species (`biomass') that consumes the
pollutant (`substrate'). In a membrane bioreactor the biomass is
constrained to remain within the reactor whereas the feed stream flows
through it.
We investigate the behaviour of a reaction governed by Contois growth kinetics in both single and double membrane reactor configurations. The optimal performance of both configurations is determined and compared. It is found that in many cases the cascade reactor may outperform the single reactor by two orders of magnitude.
Keywords, Bioreactors; Membrane bioreactors;
Reaction Engineering; Wastewater reclamation.
M.I. Nelson, X.D. Chen and H.S. Sidhu. Reducing the emission of pollutants in industrial wastewater through the use of membrane reactors. In R.J. Hosking and E. Venturino (Editors), Aspects of Mathematical Modelling, Birkhäuser, Basel, 95-107, 2008.
Abstract
In this research we analyse the steady-state operation of a continuous
flow bioreactor, with or without
recycle, and an idealised, or non-idealised, continuous flow
membrane reactor. The
reaction is assumed to be governed by, the well-known, Monod growth kinetics.
We show that a flow reactor with idealised recycle has the same
performance as an idealised membrane reactor and that the performance
of a non-idealised membrane reactor is identical to
an appropriately defined continuous flow bioreactor with
non-idealised recycle. The performance of all three
reactor types can therefore be obtained by analysing a flow reactor with
recycle. The steady-states of the recycle model are found and their
stability determined as a function of the residence time.
The performance of the reactor at large residence times is obtained.
In the limit as the residence time becomes very large, all three
reactor configurations have identical performances.
Thus the main advantage of using
a membrane reactor, or a flow reactor with recycle, for
the treatment of industrial wastewaters and slurries is to
improve the performance at low residence times. This is
quantified for the case of an ideal membrane reactor.
M.I. Nelson, T. Kerru and X.D. Chen. A fundamental analysis of continuous flow bioreactor and membrane reactor models with death and maintenance included. Asia-Pacific Journal of Chemical Engineering, 3(1), 70-80, 2008.
The DOI (Digital Object Identifier) link for this article is http://dx.doi.org/10.1002/apj.106.
Abstract
In the late 1960s Gray and Yang developed the first reduced kinetic
model for the oxidation of hydrocarbon fuels that qualitatively described
many features observed experimentally. Since then
a number of reduced kinetic models have been proposed in the literature.
In this contribution we analyse the steady-state behaviour of one
such scheme. The chemical component of the model contains four chemical
species undergoing six reactions.
By making a pool-chemical approximation this system is reduced to
three coupled non-linear differential equations:
a temperature equation and equations for two reactive chemical
intermediates.
It is shown that any steady-state solution of this model having a
steady-state temperature greater than 420 (K) is non-physical as
the steady-state concentration of the chemical species are
negative. Hence
this particular scheme does not simulate closed-vessel
experiments and is defective as an extension of the
Gray-Yang model.
M.I. Nelson and E. Balakrishnan. Autoignition of hydrocarbons in a batch reactor. Analysis of a reduced model. Applied Mathematics Letters, 21(8), 866-871, 2008.
The DOI (Digital Object Identifier) link for this article is http://dx.doi.org/10.1016/j.aml.2007.08.014.
Abstract
We analyse the steady-state treatment of
industrial wastewaters in a continuous flow bioreactor
and in an idealised
continuous flow membrane reactor. The
reaction is assumed to be governed by Contois growth kinetics,
which is often used to model the growth of biomass in
wastewaters containing biodegradable organic materials.
We show that a flow reactor with idealised recycle has the same
performance as an idealised membrane reactor and that the performance
of a non-idealised membrane reactor is identical to
an appropriately defined continuous flow bioreactor with
non-idealised recycle. The performance of all three
reactor types can therefore be obtained by analysing a flow reactor with
recycle. The steady-states of the model are found and their
stability determined as a function of the residence time.
The performance of the reactor at large residence times is obtained.
In the limit as the residence time becomes very large, all three
reactor configurations have identical performances.
Thus the main advantage of using
a membrane reactor, or a flow reactor with recycle, for
the treatment of industrial wastewaters and slurries is to
improve the performance at low residence times.
M.I. Nelson, E. Balakrishnan, H.S. Sidhu and X.D. Chen. A fundamental analysis of continuous flow bioreactor models and membrane reactor models to process industrial wastewaters. Chemical Engineering Journal, 140, 521-528, 2008.
The DOI (Digital Object Identifier) link for this article is http://dx.doi.org/10.1016/j.cej.2007.11.035.
Abstract
We investigate the production of ethanol through continuous fermentation using
Saccharomyces cerevisiae in a single reactor and cascades of two
and three reactors. We use path following methods to investigate how the
ethanol yield varies with the residence time in reach reactor of the
cascade. Yields currently obtained in industry using yeast are approximately
0.48. We find reactor designs where the product yield approaches the
stoichiometric limit of 0.51. We also estimate the financial benefits
that can be achieved in typical US ethanol plants through increasing the
product yield from 0.48 to 0.51.
H.S. Sidhu, J. Kavanagh, S.D. Watt and M.I. Nelson. Performance Evaluation of Ethanol Production Through Continuous Fermentation. In Proceedings of the 36th Australasian Chemical Engineering Conference, CHEMECA 2008, pages 590-599 (on CDROM), Engineers Australia, 2008. ISBN 85825-823-4.
Abstract
We investigate the behaviour of a reaction described by Michaelis-Menten
kinetics in an immobilised enzyme reactor (IER). The IER is treated as a
well-stirred flow reactor, in which the bound and unbounded enzyme species are
immobilized and therefore constrained to remain within the reaction vessel.
The product species leaves the bioreactor either in the reactor outflow
or by permeating through the semi-permeable reactor wall. We explore how
the concentration of recovered product and the reactor productivity vary
with process parameters, particularly those associated with the separation
of the product from the substrate through the semi-permeable reactor wall.
We show that at low residence times membrane extraction through the reactor walls increases the total product concentration recovered whereas at high residence times membrane extraction decreases the total product concentration. We also show that the reactor productivity is maximised at high residence times. For reactor productivity the key control variable is the ratio of the reactor volume to the jacket volume. If this ratio is greater than one, then membrane extraction increases the productivity. If this ratio is less than one, then membrane extraction decreases the productivity.
M.I. Nelson, H.S. Sidhu and A.A. Adesina. An Operational Model for a Well-Stirred Membrane Bioreactor: Reactor Performance Analysis. In Proceedings of the 36th Australasian Chemical Engineering Conference, CHEMECA 2008, pages 1566-1574 (on CDROM), Engineers Australia, 2008. ISBN 85825-823-4.
Abstract
In many circumstances it is useful to know the mean residence time of
food substrates within the body following digestion. For instance,
such information is crucial to estimate the extent to which dietary
components are fermented inside animal stomaches. The mean residence time
can be estimated by measuring the rate at which non-absorbable
markers, mixed as a supplement into an animals food, are deposited in the
animals faces. The experimental data are analysed with the use of an
appropriate mathematical model.
We analyse multicompartmental models for the flow of digesta along the gastrointestinal tract of animals. The problem can be treated as a sequence of `tanks' in series. Of interest is the fact that the volume of the tanks is not necessarily constant. For example, following digestion of food, secretion of pancreatic juices may occur; diluting the tracer. Thus the problem can be treated as a series of semi-batch reactors in series.
This problem is a good illustration of the application of the methods of chemical reactor engineering to a situation that, at first sight, does not appear to be a chemical engineering problem.
M.I. Nelson, H.S. Sidhu and X.D. Chen. The passage of food through animal stomachs: A chemical reactor engineering approach. In Proceedings of the 36th Australasian Chemical Engineering Conference, CHEMECA 2008, pages 533-542 (on CDROM), Engineers Australia, 2008. ISBN 85825-823-4.
Abstract
This paper deals with the esterification kinetics of oleic acid (OA)
using ethanol (EtOH) over acrylic-supported lipase from
Aspergillus niger (Novozym 435) as catalyst.
The reaction was carried out in a stirred 500 mL Pyrex glass reactor at
45oC under conditions with negligible external and internal
transport resistances. Reaction runs in a microaqueous medium
employed OA: EtOH ratio, β, between 0.01 to 2.0
without initial addition of water. The rate dependency on reactant
concentration has a maximum at β=0.9, just below the stoichiometric
ratio, and was therefore described by a Michaelis-Menten kinetic
expression implicating irreversible surface reaction between adsorbed
OA and EtOH as the rate-controlling step. Ethanol inhibition was significant
in this monophasic medium. Although there is no literature agreement on
the optimum water content in the biphasic system, the existence of
multiple peaks in the sinusoidally-decaying rate-water content profile
over a wider range (0 to 26.5 wt %) than previously investigated is
symptomatic of an autoregulatory behaviour between the organic and
aqueous phases. This was ascribed to the dynamic migration between the
well-mixed water and organic pools leading to periodic states in enzymatic
revivification. The oscillatory kinetics was adequately fitted
to under-damped sinusoidal expression with model parameters related to the
resonant frequency of the open-close water-assisted activation of the
lipase site.
M.S. Mahmudp, J.W. Ryanu, C.G. Cooperu, T. Safinski, M. Nelson, H.S. Sidhu and A.A. Adesina. Kinetic Analysis of Oleic Acid Esterification Using Lipolytic Enzyme As Catalyst. In Proceedings of the 36th Australasian Chemical Engineering Conference, CHEMECA 2008, pages 1382-1392 (on CDROM), Engineers Australia, 2008. ISBN 85825-823-4.
Abstract
R. Hudsonp, A. Porter and M. Nelson. Barriers to Using ICT in Mathematics Teaching: Issues in Methodology. In Proceedings of ED-MEDIA 2008, World Conference on Educational Multimedia, Hypermedia & Telecommunications, pages 5765-5700, Association for the Advancement of Computing in Education, Chesapeake, VA, USA, 2008.
Abstract
R. Hudsonp, A. Porter and M. Nelson. The View of Secondary School Mathematics Teachers in Australia regarding the use of Technology in the Classroom. In Proceedings of ED-MEDIA 2008, World Conference on Educational Multimedia, Hypermedia & Telecommunications, pages 5711 - 5777, Association for the Advancement of Computing in Education, Chesapeake, VA, USA, 008,