Potential Honours Projects

The following list does not aim to be an exhaustive list of honours projects that I am interested in supervising, it is a list of things that are interesting to investigate. Don't worry if some of these projects don't make to you, come and see me for more details - the comments make sense to me.

Autothermal reactors

Autothermal processes combine exothermic reactions, which produce heat, and endothermic reactions, which take heat out of the system. The advantages of autothermal reactors include:

  1. In conventional reactors energy must be supplied for endothermic reactions to proceed, typically through the use of external burners or interstage heaters. The exothermic reaction produces heat, increasing the temperature of the reactor and increasing the rate at which the endothermal process occurs. In an autothermal reactor we get the heating for free. The absence of an external burner and the accompanying power supplies makes the system both simpler and less expensive.
  2. The endothermal reaction controls the temperature of the system, making it less likely that thermal runaway will occur as it provides a source of cooling.
  3. If the system is correctly setup then the overall process is energy neutral. The energy released by the exothermic reaction drives the endothermic reaction. This is an autothermal reactor.

There is growing interest in the use of autothermal reactors to efficiently produce hydrogen from natural gas, and other fuels such as ethanol, for use in fuel cells. Such technology has great potential as an energy supply for compact mobile power supplies, which can be used in homes and cars of the future. It can also be scaled up to provide a distributed supply of energy for industrial markets. The use of such reactors will contribute towards reducing greenhouse gas emissions.

Hydrogen can be produced through the catalytic reforming of hydrocarbons. This process couples endothermic steam reforming with exothermic oxidation to create hydrogen-rich fuel feeds. In this project we will examine some simple models for this process.

Biological Heating

Generation of heat within the human body. References supplied by Professor Brian Gray are:
Biological Applications of Combustion Theory, with N.A. Kirwan and P. Gray. Combustion and Flame 18, 439, 1972.
Heat Generation in Tissues, Bulletin of Mathematical Biology, 42, 273 (1980).
Distribution of Heat Sources in the Human Head, Journal of Theoretical Biology, 82, ???
Surface law and Metabolic Rate. J. Theoretical Biology, 2, 757, 1982.
Physical Theory of Enzyme Catalysis (with I. Gonda). J. Theoretical biology, 94, 513 (1982).

The last one is quantum mechanics, so you might not want to know about that.

Biotechnology

Panikov, N.S. Microbial Growth Kinetics. Chapman & Hall, UK, 1995.

Andrews model

  1. Look at double-substrate inhibition models with constant yields. (Follow up to Tim's advanced maths project with emphasis on stability calculations). (wu-sc:2007)
  2. Variable yield model with death. suzuki:1985.
  3. grieves:1968 Look at two-tank model with variable volume distribution and variable feed distribution.

Double substrate kinetics

(a good keyword). See sonmezisik:1998. "Under certain conditions, the growth rate of an organism may be simultaneously limited by two or more substrates" (6-9).

beyenal:2003 Double substrate kinetics that are both Tessier. (Standard is to use monod for both).

yurt:2002 "It is well-known that the microbial growth rate often depends on more than one substrate (Machado et al 1989; Beyenal and Tanyolac, 1997; Neeleman et al, 2001).

Ethanol

Food Engineering

Dong suggests the following as a good research problem for a strong PhD student

My suggestion is to work in heat/mass transfer (in drying) coupled with mechanics (stress strain analysis)...this can make a difference in literature. The ideal candidate is to look at how micron sized particles (functional particles for medical or food purpose) formed during liquid removal. So far heat and mass transfer have been investigated a great deal but the formation of the shell and shell structure has not been touched which I feel very very important.

Immobilised Enzyme Reactors

justification purwadi:2008

Membrane Reactors

Incomplete mixing

Nano-particulate Membrane Bioreactor (NMB)

AMT have developed a nano-particulate membrane bioreactor (NMB) which has been shown to work at various scales with gray water, grease trap waste, sewage and many different industrial waste water streams such as effluents from breweries, wineries and a detergent factory. We will develop models from this process based upon partial differential equations. (See work folder for chemeca flyer). (Note basic membrane reactor model also appears in yoon-sc:2004).

Predator-prey dynamics

Food processing wastewaters and slurries typically contain high concentrations of biodegradable organic matter. Before the wastewater can be discharged the pollutant concentration must be reduced. One way to achieve this is through the use of a biological species (`biomass') that consumes the organic matter (`substrate').

In this project we will examine what happens when competition is moved up one level by investigating what happens if there is a predator that grows by consuming the biomass. Our interest is in how this competition influences the level of pollutant that is discharged from the reactor.

Another application is to reduce excess sludge production in the activated sludge process - zhang-b:1996

Sludge disintegration

  1. Sludge disintegration inside a normal bioreactor. EB
    Yasui and Shibata (wei-y:2003, 31) developed a new process for reducing sludge production in the activated sludge process. The process consists of a sludge ozonation stage and a biodegradation stage, in which a fraction of recycled sludge passes through the ozonation unit and then the treated sludge is decomposed in the subsequent biological treatment.
  2. Add a model for sludge disintegration. Thomas' model should be extended from 3 ODE to 6 ODE. The sludge disintegration unit should be treated as a second reactor. EDB
  3. Easy project is to look at exact parametric sensitivity in the yoon model using the exact steady-state values.
  4. EDB. Note that the usual model for sludge disintegration assumes that μm and KS are the same for all soluble organic materials, whether they are originated from influent or disintegrated liquor.
  5. The ultimate sludge-disintegration model is to use the bioreactor model from yoon-sh:2005 with simple kinetics.
  6. Should look at a disintegration unit inside a normal bioreactor.
    7. Variation of MLSS in a cascade of reactors with sludge disintegration units?
  7. grady:1980chap12 might be useful for background models with nonviable cells.

Processing of industrial wastewaters and slurries

  1. Re-consider the model with a variable yield coefficient and non-dimensionalise it correctly. Add death to the model.
    1. Determine performance of the optimised cascade and the cascade with equal residence time for two and three reactors.
    2. Re-investigate membrane model. H21 bifurcation curve in alpha-beta-k_d plane. (note basic membrane bioreactor model also appears in yoon-sc:2004)
    1. Model of a fixed-bed biological process and a generalized model of a fixed-bed biological process
    2. The fixed-bed reactor as two completely mixed compartments in parallel (Escudie et al., 2005).
  3. Contois model with X0 not equal to zero. EB. harmand:2006b looked at the standard model with recirculation and by-pass in a control session. Can this be extended to the contois model?
  4. Investigate a model with a sludge disintegration system (cf thomas' masters project)
  5. Ice cream in a series of membran reactors.
  6. Use Andrews solutions for a two- and three- reactor cascade. Use the optimisation functions of Erickson and Fan (1968). This is really an optimisation project, rather than a dynamical systems project. Similarly can look at the paper by Grieves and Kao. And the paper by Scuras (2001). And Hill and Robertson (1989). Harmand et al (2003) is definitive for some systems. Could re-investigate the effect of death upon many of these systems. It's interesting the in the paper with Andrew I observed that at high residence times equal-residence times give a performance that is very nearly optimal. Optimising the reactor design only seems to bring improvements at low residence time. Is this a function of death? Investigate recycle. Good
  7. grady:book page 640. Step Aeration Activated Sludge (SAAS) can be modeled as four CSTR's in series with feed distribution to each tank

Simple models for product inhibition

Seperator-reactor systems using a membrane

Extend Soji model to consider different kinetics: Monod, Contois, Andrews and product inhibition. (note basic membrane bioreactor model also appears in yoon-sc:2004)

Standard Model

  1. Add a model for hydrolysis of death biomass. EDB
  2. Model wall growth.
    1. bungay:1968 "In our laboratories, some studies of competition have shown that adherence to the walls of the vessel can be a key factor in competition. A slower growing species can persist in appreciable numbers in competition with rapidly growing organisms if the slow grower is continually reinoculated from the wall growth into the main liquid bulk".
    2. senn:1994 "It is well-known that wall growth can affect steady-state concentrations in chemostat cultures. This effect should be most pronounced at low input substrate concentrations in the medium feed where the proportion of biomass on the wall is high compared to that in solution".
  3. canale:1973 "a massive protozoan lysis had occurred. This cell lysis caused considerable amounts of debris to accumulate within the medium".
    Two other continuous runs of short duration at low dilution rates resulted in a similar breakdown of the Tetrahymena population.
    See predator-prey notes for a simple model.
  4. Models in which both species produce a toxin for each other with a variable yield coefficient.
  5. abulesz:1987 investigated time delay models. This leads to a system of three, rather than two, equations. This opens up a large avenue of potential problems!

    "All unstructured models predict a response to step-changes in operating variables which is faster than experimentally observed (40). This is a result of the inherent assumption of those models that there is no time lag between changes in the substrate level and adjustment of the growth rate at the appropriate level. To relax this assumption, one may assume that the specific growth rate is a function not only of the present substrate level but also of previous levels in a weighted manner". See also their references (41 & 42) and page 1062.

    1. beyenal:2003 "It was expected that at low agitation rates the growth of microorganisms was limited by external mass transport. Therefore, when the agitation rates increased, the mass transfer rate to the microorganisms increased, along with the SOUR, which reached a maximum value. Increasing the agitation rate beyond this maximum actually decreased the SOUR, probably because the agitation was injuring the microorganisms."
    2. yurt:2002 At low agitation rates, Leptothrix discophora SP-6 aggregated, and at higher agitation rates it was mechanically damaged.
  7. Is it possible to investigate a stochastic version of the standard model and investigate the effect on wash-out conditions?
  8. Standard model with dead cells. See grady:1980 for background and also link this to the sludge disintegration unit work.
  9. grady:1980. Basic CSTR model with non-viable cells.
  10. grady:1980. Recycle models. There are four cases of particular interest, all of which will use equal reactor volumes. In the first case, the system corresponds to a simple chain, with all feed and all recycle going to reactor one. In case two, the feed and recycle are distributed evenly amongst the four tanks. In case three, the feed is distributed evenly among the four tanks and the recycle is added to tank 1, whereas in case four, all recycle is returned to tank 1 and all feed enters tanks 3.
  11. grady:1980. Extend the basic model to analyse oxygen demand. This can then be used to determine waste stabilisation. (chapter 12). This would make a good six credit-point project.
  12. Velocity dependent death rate.
  13. Asymptotics for membrane reactor cascade (contois). Compare against conventional reactors.
  14. jost-c:2000 has lots of interesting things to read.

    The first approach to reconcile theory and experiment was to introduce flexible models that contain both Monod's and Contois's functions as special cases (Roques et al 1982, Borija et al. 1995).

    μ(S,X) = μS/(Ks+S+cX)

    This form was introduced independently in ecology by DeAngelis et al (1975) and by Beddington (1975).

  15. incomplete mixing using the standard approach. First assume no death.
  16. roques:1982 proposed a general rate expression which includes both the Monod and Contois expressions as special cases:
    μ(S,X) = &mumaxS/(S+a+bX).
  17. Model recycle more realistically (if possible) by looking at sludge thickness analysis. See references [62,65] on page 673 of grady:book for starts.

    Miscellaneous

    1. Systems with Tissiet kinetics. fu-g:2005
    2. Edwards kinetics (sonmezisik:1998 reference 17)
    3. Luong kinetics (sonmezisik:1998 reference 18)
    4. Tessier kinetics with substrate inhibition and product inhibition annuar:2008. Need to check out the reference (Heinzle and Lafferty, 1980).
    5. Tessier kinetics with a sludge disintegration system.

    Heat Transfer

    Heterogeneous catalysis

    Extend CTM paper on heterogeneous catalysis from a single reaction to a bi-molecular reaction.

    Mathematical Ecology and Epidemiology

    1. R.S. Cantrell and C. Cosner. Spatial Ecology via Reaction-Diffusion Equations. Wiley. 577.0151/3.
      Malchow, S.V. Petrovskii, Venturino. Spatiotemporal Patterns in Ecology and Epidemiology. 577.015118/2
    2. Apply semi-analytical technique to RD equations.
    3. jost-c:2000 has lots to say about predator dependent growth-rates in mathematical ecology in analogy with microbiology and provides good references.

    Drug delivery by nano-particles

    1. Spherical particles with concentric layers of inert and drug. Can target time-to-release by design of layers.
    2. Maybe c(r) - internal concentration of drug as a function of radius as a way to control drug delivery rate.
    3. Want to achieve a constant delivery of drug.
    4. Maybe we could design different biodegradable materials with different k values. Then distribution of k values leads to a different delivery profile.

    Food Engineering

    The food industry offers a surprisingly rich variety of interesting problems in applied mathematics. Here are a couple that I am interested in.

    Drying of small particles
    We will investigate the composition and temperature of spray-dried particles using distributed drying kinetics. This model will be used to investigate segregation, which has been observed experimentally during the spray drying of milk. (Model can also be applied to the rice swelling problem.)
    Drying of a French Fry
    This project involves modelling the frying of a french fry in hot oils. The primary practical interest in this problem is to drive vapour out of the fry and this is what we will seek to model. The chicken pattie model may be useful for this problem...

    Mathematical modelling of the GIT

    1. Volume increasing + decreasing. Fit data to wrong models? EB?
    2. Spratt, P., Nicolella, C., Pyle, D.L. (2005) An engineering model of the human colon. Trans IChemE, Part C, Food and Bioproducts Processing 83 (C2), 147-157.

    Semi-analytical solutions

    This would be a joint-project with Professor T.R. Marchant.

    Transform methods to solve linear PDEs

    Dong's salt diffusion problem as a two-layer diffusion problem. Apply the mean action time approach used by Hickson.

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    Page Created: 27th October 2007.
    Last Updated: 25th September 2009.