Process and Chemical Engineering - Doctoral Theses

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Characterisation and improvement of the rehydration behaviour of high-protein milk powder
(University College Cork, 2020-08-03) Wu, Shaozong; Fitzpatrick, John J.; Cronin, Kevin; Miao, Song; University College Cork; Teagasc; China Scholarship Council
Milk protein isolate (MPI) has poor rehydration behaviours, particular in wetting and dissolution. The rehydration difficulty inhibited the achievement of MPI functionality. Methods were explored to solve rehydration difficulty. Agglomeration was a valid method for enhancing the wetting of dairy powder. Moreover, broadband acoustic resonance dissolution spectroscopy (BARDS) monitored gas release from powder through the alteration of speed of sound in solution. Thus, BARDS was utilised to study the gas release behaviour of agglomerated MPI, and MPI coated with emulsifiers. Meanwhile, as MPI composed mainly by casein, pH of solution affected the status of casein which possibility modify the rehydration process of MPI as well. Real-time measurement of particle size was applied to analyse the effect of pH on rehydrating MPI. Sodium carbonate, as an alkali food additive, was firstly studied at rehydrating dairy powder. However, alkalization of MPI followed by neutralization has been thoroughly investigated. Consequently, considering the effect of calcium chelation on MPI, citric acid was utilised to neutralise MPI from alkalization. Finally, the gelation behaviour of MPI was studied in a different sequence of neutralisation. Our results showed that as the porous structure modified the gas distribution in agglomerated MPI, interstitial air within agglomerates and vacuole air within agglomerates determined the gas release behaviour of agglomerated powder, while the vacuole air in primary powder particle became a crucial barrier for MPI dissolution. The BARDS profile showed that there was faster initial gas release from the agglomerates, indicating better wetting and dispersion ability of the agglomerates. The gas release of MPI during the wetting step was facilitated by lecithin and Tween 80 while the dissolution step was still poor. The wetting behaviour of MPI covered by the emulsifiers was greatly improved except for samples coated with 4% lecithin. The most instant wetting behaviour was observed when coating MPI with Tween at the larger size fractions. The swelling of the primary particle was observed in alkalization, which was ascribed to the swelling of casein micelle aggregates. This swelling of casein micelle aggregates indicates greater water penetration and loosening of the aggregate structure at higher pH, which facilitated the faster dissolution of MPI powder, especially at pH 8.4. As alkalization proved an excellent ability at the dissolution of MPI, sodium carbonate was utilised, which also showed improvement of MPI rehydration. Sodium carbonate was supposed as a calcium chelation as well to modifying the structure of casein micelle. The results showed that wettability worsened with higher sodium carbonate concentrations, due to strong films developing at the powder/water interfaces which inhibited water penetration into the MPI. However, appropriate agitation could effectively wet and disperse MPI. On the other hand, particle size and centrifugal sedimentation studies showed that increasing the sodium carbonate concentration greatly improved the dissolution ability of the MPI powder. The subsequent neutralisation process by citric acid enhanced the effects of calcium chelation due to reaction-product citrate. Besides, alkalization and neutralisation created larger colloidal particle size, which is hypothesised as being a dynamic balance between micellar casein and non-micellar casein. The sequence of neutralisation determined the process of rehydration, which in turn determine the gelation process. As for the gelation time and gel stiffness, performing alkalization firstly before neutralisation had a better result corresponding with increasing mobile casein molecule by improved rehydration, exhibiting homogeneous gel structure.
Comparison of deterministic, stochastic and fuzzy logic uncertainty modelling for capacity extension projects of DI/WFI pharmaceutical plant utilities with variable/dynamic demand
(University College Cork, 2011-06) Riedewald, Frank; Byrne, Edmond P.
The last 30 years have seen Fuzzy Logic (FL) emerging as a method either complementing or challenging stochastic methods as the traditional method of modelling uncertainty. But the circumstances under which FL or stochastic methods should be used are shrouded in disagreement, because the areas of application of statistical and FL methods are overlapping with differences in opinion as to when which method should be used. Lacking are practically relevant case studies comparing these two methods. This work compares stochastic and FL methods for the assessment of spare capacity on the example of pharmaceutical high purity water (HPW) utility systems. The goal of this study was to find the most appropriate method modelling uncertainty in industrial scale HPW systems. The results provide evidence which suggests that stochastic methods are superior to the methods of FL in simulating uncertainty in chemical plant utilities including HPW systems in typical cases whereby extreme events, for example peaks in demand, or day-to-day variation rather than average values are of interest. The average production output or other statistical measures may, for instance, be of interest in the assessment of workshops. Furthermore the results indicate that the stochastic model should be used only if found necessary by a deterministic simulation. Consequently, this thesis concludes that either deterministic or stochastic methods should be used to simulate uncertainty in chemical plant utility systems and by extension some process system because extreme events or the modelling of day-to-day variation are important in capacity extension projects. Other reasons supporting the suggestion that stochastic HPW models are preferred to FL HPW models include: 1. The computer code for stochastic models is typically less complex than a FL models, thus reducing code maintenance and validation issues. 2. In many respects FL models are similar to deterministic models. Thus the need for a FL model over a deterministic model is questionable in the case of industrial scale HPW systems as presented here (as well as other similar systems) since the latter requires simpler models. 3. A FL model may be difficult to "sell" to an end-user as its results represent "approximate reasoning" a definition of which is, however, lacking. 4. Stochastic models may be applied with some relatively minor modifications on other systems, whereas FL models may not. For instance, the stochastic HPW system could be used to model municipal drinking water systems, whereas the FL HPW model should or could not be used on such systems. This is because the FL and stochastic model philosophies of a HPW system are fundamentally different. The stochastic model sees schedule and volume uncertainties as random phenomena described by statistical distributions based on either estimated or historical data. The FL model, on the other hand, simulates schedule uncertainties based on estimated operator behaviour e.g. tiredness of the operators and their working schedule. But in a municipal drinking water distribution system the notion of "operator" breaks down. 5. Stochastic methods can account for uncertainties that are difficult to model with FL. The FL HPW system model does not account for dispensed volume uncertainty, as there appears to be no reasonable method to account for it with FL whereas the stochastic model includes volume uncertainty.
Dairy powder breakage: mechanisms, impact factors, and influences on powder properties
(University College Cork, 2022-05) Han, Jie; Miao, Song; Fitzpatrick, John J.; Cronin, Kevin; Teagasc; University College Cork
Dairy powders provide a good form for convenient and stable preservation and transportation of milk ingredients, and most commercial dairy powders are agglomerated to improve powder functionalities. However, particle breakage during production and transportation is an important issue for agglomerates and only a few studies on dairy powder breakage have been published. Therefore, there is limited information to understand this phenomenon and find ways to decrease it. The present study investigated the breakage mechanisms of dairy powders, the influence of dairy powder breakage on powder properties, and the impact of powder characteristics on dairy powder breakage. This provides more information to better understand and control dairy powder breakage in an effort to improve the functionalities of dairy powders. The main breakage mechanisms of agglomerated infant milk formula (IMF) during transportation and mixing included dispersion, chipping (surface breakage), and fragmentation (body breakage, which includes both disintegration and splitting), which correspond to an increasing extent of breakage. The breakage mechanism of whole samples was one or a combination of breakage mechanisms because the breakage behaviour of samples with different particle sizes at the same process condition was different. Dairy powder breakage significantly decreased the particle size and porosity of powders and increased the specific surface area, particle density, and bulk density of samples. It also changed the shapes and surface composition of particles as seen with the increase in lactose content and the decrease in protein and fat contents for most samples. These changes in physical properties significantly deteriorated the rehydration properties of dairy powders, including the wettability and dispersibility, while it had only a small influence on powder flowability. In addition, body breakage had greater influences on powder physical properties than surface breakage. Thus, surface breakage had no influence on water sorption and mechanical properties of powders but body breakage significantly deteriorated these properties as seen with the increase in water sorption rates and final water contents, the acceleration in the crystallization, and the decrease in the overall molecular mobility. Dairy powder breakage degree or mechanisms was determined by the process conditions and particle characteristics. Breakage increased with increasing intensity of processing conditions, such as the transportation velocity and air pressures. In addition, fatigue affected the breakage of agglomerates dairy powders. For powder characteristics, the breakage degree of dairy powders increased with increasing particle size and decreasing particle structural strength. Considering particle structure, the strength of crystals and continuum solids were the highest, followed by particles with numerous holes throughout the particle, followed by the hollow sphere particle with a very thin shell. Under the same spray drying conditions, the formulation of dairy powders significantly affects dairy powder breakage by influencing the physical properties of powder particles, especially for particle size and particle structure. For whey protein/lactose model agglomerated powders, the two higher whey-protein powders were smaller in particle size, were less irregular in shape and had higher particle densities, which resulted in less breakage in comparison to the two lower whey-protein powders. For agglomerated model IMF powders that contained different protein and carbohydrates, whey protein powders were bigger in particle size, weaker in structural strength, and more irregular in shape in comparison to pure casein powders. This resulted in the better rehydration properties of whey protein powders but more breakage. Similarly, sucrose IMF samples had better rehydration properties but suffered more breakage than maltodextrin and pure lactose powders because of their bigger particle size. Findings in this study indicate that body breakage significantly deteriorates powder properties, so breakage should be limited to surface breakage. Since powder breakage cannot be avoided, changes to processing conditions (using lower conveying speeds or air pressures) and powder physical properties (mainly particle size and particle structure by changing production conditions or formulations) should be done to reduce breakage intensity.
Development of a triple stage heat transformer for the recycling of low temperature heat energy
(University College Cork, 2014) Donnellan, Philip; Byrne, Edmond P.; Cronin, Kevin; Irish Research Council for Science Engineering and Technology
Absorption heat transformers are thermodynamic systems which are capable of recycling industrial waste heat energy by increasing its temperature. Triple stage heat transformers (TAHTs) can increase the temperature of this waste heat by up to approximately 145˚C. The principle factors influencing the thermodynamic performance of a TAHT and general points of operating optima were identified using a multivariate statistical analysis, prior to using heat exchange network modelling techniques to dissect the design of the TAHT and systematically reassemble it in order to minimise internal exergy destruction within the unit. This enabled first and second law efficiency improvements of up to 18.8% and 31.5% respectively to be achieved compared to conventional TAHT designs. The economic feasibility of such a thermodynamically optimised cycle was investigated by applying it to an oil refinery in Ireland, demonstrating that in general the capital cost of a TAHT makes it difficult to achieve acceptable rates of return. Decreasing the TAHT's capital cost may be achieved by redesigning its individual pieces of equipment and reducing their size. The potential benefits of using a bubble column absorber were therefore investigated in this thesis. An experimental bubble column was constructed and used to track the collapse of steam bubbles being absorbed into a hotter lithium bromide salt solution. Extremely high mass transfer coefficients of approximately 0.0012m/s were observed, showing significant improvements over previously investigated absorbers. Two separate models were developed, namely a combined heat and mass transfer model describing the rate of collapse of the bubbles, and a stochastic model describing the hydrodynamic motion of the collapsing vapour bubbles taking into consideration random fluctuations observed in the experimental data. Both models showed good agreement with the collected data, and demonstrated that the difference between the solution's temperature and its boiling temperature is the primary factor influencing the absorber's performance.
Dry mixing of spice powders - investigation of effect of powder properties on mixture quality of binary powder mixtures
(University College Cork, 2014) Shenoy, Pooja; Fitzpatrick, John J.; Ahrné, Lilia; European Commission
Dry mixing of binary food powders was conducted in a 2L lab-scale paddle mixer. Different types of food powders such as paprika, oregano, black pepper, onion powder and salt were used for the studies. A novel method based on a digital colour imaging system (DCI) was developed to measure the mixture quality (MQ) of binary food powder mixtures. The salt conductivity method was also used as an alternative method to measure the MQ. In the first part of the study the DCI method was developed and it showed potential for assessing MQ of binary powder mixes provided there was huge colour difference between the powders. In the second and third part of the study the effect of composition, water content, particle size and bulk density on MQ was studied. Flowability of powders at various moisture contents was also investigated. The mixing behaviour was assessed using coefficient of variation. Results showed that water content and composition influence the mixing behavior of powders. Good mixing was observed up to size ratios of 4.45 and at higher ratios MQ disimproved. The bulk density had a larger influence on the MQ. In the final study the MQ evaluation of binary and ternary powder mixtures was compared by using two methods – salt conductivity method and DCI method. Two binary food and two quaternary food powder mixtures with different coloured ingredients were studied. Overall results showed that DCI method has a potential for use by industries and it can analyse powder mixtures with components that have differences in colour and that are not segregating in nature.
Electrochemical materials for integrated magnetics
(University College Cork, 2021-06-23) Smallwood, Daniel C.; Rohan, James; McCloskey, Paul; Science Foundation Ireland
Next generation microinductors with magnetically enhanced VIA technology hold great promise for power converter applications in broad technology domains such as automotive, space, high-end computing, mobile devices, radio frequency (RF), artificial intelligence (AI) and the internet of things (IoT). Microinductor VIAs enable monolithic 3D device topologies with reduced footprint, increased inductance density and minimal parasitics. These qualities are essential for emerging 2.5/3D packaging architectures that require granular point-of-load (PoL) power delivery to efficiently supply a multitude of heterogeneously integrated devices. This thesis addresses the challenges of 3D monolithic microinductor design and fabrication, inclusive of magnetically enhanced VIAs comprising a clad laminated soft magnetic core. The current state-of-the-art utilizes 2D microinductor topologies and 2D fabrication methods, therefore significant advancement is required to enable fabrication of a novel 3D monolithic microinductor device comprising vertically oriented integrated magnetics. The major challenges addressed in this thesis fall into two main categories: 1) predictive modeling with computational lithography and computational electrochemistry to enable optimization of the VIA formation process and 2) the design and fabrication of a novel magnetically enhanced monolithic 3D microinductor device. A major contribution from the computational lithography is the derivation of a novel polychromatic light attenuation equation that is used to produce a succinct formula comprising a complete coupling between resist photochemistry and light diffraction effects. Additionally, new photoresist exposure dose determination methods are presented that negate the need for time consuming and costly in-situ metrology. These equations and methods enable fast and accurate predictive modeling of 3D photoresist VIA latent images, which are verified by comparison to directly corresponding experimental work, with highly positive correlation. These formulas converge quickly on the average modern computer and can be readily integrated into lithography simulators. Photoresist development is then investigated, wherein spin development is identified as the optimal method for wet etching VIA latent images. With computational electrochemistry, the electroforming process of Cu VIAs is explored using the FEM in COMSOL Multiphysics to perform 2D and 3D time-dependent simulation studies. Simulations are then verified by comparison to experimental results, with highly positive correlation. Special attention is given to electroformed surface topographies, which is valuable for sensor and flip chip applications. The major contributions from the microinductor device design and fabrication first include designing a unique device that meets target specifications for reduced footprint, increased inductance density and minimized parasitics. A novel fabrication process flow is next engineered to enable a vertically meandering current path with a repeating unit cell comprising a bottom interconnect, a first Cu VIA, a top interconnect and a second Cu VIA. This process flow is compatible with conformal deposition of a soft magnetic laminate (e.g., CoZrTa) for formation of a vertically oriented magnetic core clad on the Cu VIAs. Next, a 5-tiered photomask stack is designed and the corresponding SOPs are engineered. This enables fully in-house microinductor device fabrication, after which vital metrology and characterization is performed. The measured inductance density of our prototype magnetically enhanced monolithic 3D microinductor devices is 16.85 nH/mm2, which is comparable to previously reported metrics for fabricated 3D microinductors. This metric could be significantly improved in future devices by increasing the magnetic core thickness and/or optimizing the magnetic anisotropy characteristic of the integrated magnetic material and/or reducing the pillar diameter, wherein the VIA fabrication research presented in this thesis will be essential. Therefore, this novel microinductor research holds great promise for applications in next generation power converters.
Engineering design of a bioprocess for the production of natural red colourants by submerged fermentation of the thermophilic fungus Penicillium purpurogenum GH2
(University College Cork, 2015) Morales, Lourdes; Oliveira, Jorge C.; Sousa Gallagher, Maria J; Consejo Nacional de Ciencia y Tecnología, Mexico
The development of a new bioprocess requires several steps from initial concept to a practical and feasible application. Industrial applications of fungal pigments will depend on: (i) safety of consumption, (ii) stability of the pigments to the food processing conditions required by the products where they will be incorporated and (iii) high production yields so that production costs are reasonable. Of these requirements the first involves the highest research costs and the practical application of this type of processes may face several hurdles until final regulatory approval as a new food ingredient. Therefore, before going through expensive research to have them accepted as new products, the process potential should be assessed early on, and this brings forward pigment stability studies and process optimisation goals. Only ingredients that are usable in economically feasible conditions should progress to regulatory approval. This thesis covers these two aspects, stability and process optimisation, for a potential new ingredient; natural red colour, produced by microbial fermentation. The main goal was to design, optimise and scale-up the production process of red pigments by Penicillium purpurogenum GH2. The approach followed to reach this objective was first to establish that pigments produced by Penicillium purpurogenum GH2 are sufficiently stable under different processing conditions (thermal and non-thermal) that can be found in food and textile industries. Once defined that pigments were stable enough, the work progressed towards process optimisation, aiming for the highest productivity using submerged fermentation as production culture. Optimum production conditions defined at flask scale were used to scale up the pigment production process to a pilot reactor scale. Finally, the potential applications of the pigments were assessed. Based on this sequence of specific targets, the thesis was structured in six parts, containing a total of nine chapters. Engineering design of a bioprocess for the production of natural red colourants by submerged fermentation of the thermophilic fungus Penicillium purpurogenum GH2.
Engineering design of an integrated sustainable process system for cassava biobased materials
(University College Cork, 2016) Tumwesigye, Kashub S.; Sousa Gallagher, Maria J.; Oliveira, Jorge C.; National Agricultural Research Organisation, Uganda.
Cassava contributes significantly to biobased material development. Conventional approaches for its bio-derivative-production and application cause significant wastes, tailored material development challenges, with negative environmental impact and application limitations. Transforming cassava into sustainable value-added resources requires redesigning new approaches. Harnessing unexplored material source, and downstream process innovations can mitigate challenges. The ultimate goal proposed an integrated sustainable process system for cassava biomaterial development and potential application. An improved simultaneous release recovery cyanogenesis (SRRC) methodology, incorporating intact bitter cassava, was developed and standardized. Films were formulated, characterised, their mass transport behaviour, simulating real-distribution-chain conditions quantified, and optimised for desirable properties. Integrated process design system, for sustainable waste-elimination and biomaterial development, was developed. Films and bioderivatives for desired MAP, fast-delivery nutraceutical excipients and antifungal active coating applications were demonstrated. SRRC-processed intact bitter cassava produced significantly higher yield safe bio-derivatives than peeled, guaranteeing 16% waste-elimination. Process standardization transformed entire root into higher yield and clarified colour bio-derivatives and efficient material balance at optimal global desirability. Solvent mass through temperature-humidity-stressed films induced structural changes, and influenced water vapour and oxygen permeability. Sevenunit integrated-process design led to cost-effectiveness, energy-efficient and green cassava processing and biomaterials with zero-environment footprints. Desirable optimised bio-derivatives and films demonstrated application in desirable in-package O2/CO2, mouldgrowth inhibition, faster tablet excipient nutraceutical dissolutions and releases, and thymolencapsulated smooth antifungal coatings. Novel material resources, non-root peeling, zero-waste-elimination, and desirable standardised methodology present promising process integration tools for sustainable cassava biobased system development. Emerging design outcomes have potential applications to mitigate cyanide challenges and provide bio-derivative development pathways. Process system leads to zero-waste, with potential to reshape current style one-way processes into circular designs modelled on nature's effective approaches. Indigenous cassava components as natural material reinforcements, and SRRC processing approach has initiated a process with potential wider deployment in broad product research development. This research contributes to scientific knowledge in material science and engineering process design.
Evaporation maps for ternary non-ideal liquid mixtures
(University College Cork, 2016) Dillon, Paul; Cronin, Kevin; Byrne, Edmond P.
This thesis deals with the evaporation of non-ideal liquid mixtures using a multicomponent mass transfer approach. It develops the concept of evaporation maps as a convenient way of representing the dynamic composition changes of ternary mixtures during an evaporation process. Evaporation maps represent the residual composition of evaporating ternary non-ideal mixtures over the full range of composition, and are analogous to the commonly-used residue curve maps of simple distillation processes. The evaporation process initially considered in this work involves gas-phase limited evaporation from a liquid or wetted-solid surface, over which a gas flows at known conditions. Evaporation may occur into a pure inert gas, or into one pre-loaded with a known fraction of one of the ternary components. To explore multicomponent masstransfer effects, a model is developed that uses an exact solution to the Maxwell-Stefan equations for mass transfer in the gas film, with a lumped approach applied to the liquid phase. Solutions to the evaporation model take the form of trajectories in temperaturecomposition space, which are then projected onto a ternary diagram to form the map. Novel algorithms are developed for computation of pseudo-azeotropes in the evaporating mixture, and for calculation of the multicomponent wet-bulb temperature at a given liquid composition. A numerical continuation method is used to track the bifurcations which occur in the evaporation maps, where the composition of one component of the pre-loaded gas is the bifurcation parameter. The bifurcation diagrams can in principle be used to determine the required gas composition to produce a specific terminal composition in the liquid. A simple homotopy method is developed to track the locations of the various possible pseudo-azeotropes in the mixture. The stability of pseudo-azeotropes in the gas-phase limited case is examined using a linearized analysis of the governing equations. Algorithms for the calculation of separation boundaries in the evaporation maps are developed using an optimization-based method, as well as a method employing eigenvectors derived from the linearized analysis. The flexure of the wet-bulb temperature surface is explored, and it is shown how evaporation trajectories cross ridges and valleys, so that ridges and valleys of the surface do not coincide with separation boundaries. Finally, the assumption of gas-phase limited mass transfer is relaxed, by employing a model that includes diffusion in the liquid phase. A finite-volume method is used to solve the system of partial differential equations that results. The evaporation trajectories for the distributed model reduce to those of the lumped (gas-phase limited) model as the diffusivity in the liquid increases; under the same gas-phase conditions the permissible terminal compositions of the distributed and lumped models are the same.
Experimental quantification and modelling of attrition of infant formulae during pneumatic conveying
(University College Cork, 2011-08) Hanley, Kevin John; Byrne, Edmond P.; Cronin, Kevin; Irish Research Council for Science Engineering and Technology
Infant formula is often produced as an agglomerated powder using a spray drying process. Pneumatic conveying is commonly used for transporting this product within a manufacturing plant. The transient mechanical loads imposed by this process cause some of the agglomerates to disintegrate, which has implications for key quality characteristics of the formula including bulk density and wettability. This thesis used both experimental and modelling approaches to investigate this breakage during conveying. One set of conveying trials had the objective of establishing relationships between the geometry and operating conditions of the conveying system and the resulting changes in bulk properties of the infant formula upon conveying. A modular stainless steel pneumatic conveying rig was constructed for these trials. The mode of conveying and air velocity had a statistically-significant effect on bulk density at a 95% level, while mode of conveying was the only factor which significantly influenced D[4,3] or wettability. A separate set of conveying experiments investigated the effect of infant formula composition, rather than the pneumatic conveying parameters, and also assessed the relationships between the mechanical responses of individual agglomerates of four infant formulae and their compositions. The bulk densities before conveying, and the forces and strains at failure of individual agglomerates, were related to the protein content. The force at failure and stiffness of individual agglomerates were strongly correlated, and generally increased with increasing protein to fat ratio while the strain at failure decreased. Two models of breakage were developed at different scales; the first was a detailed discrete element model of a single agglomerate. This was calibrated using a novel approach based on Taguchi methods which was shown to have considerable advantages over basic parameter studies which are widely used. The data obtained using this model compared well to experimental results for quasi-static uniaxial compression of individual agglomerates. The model also gave adequate results for dynamic loading simulations. A probabilistic model of pneumatic conveying was also developed; this was suitable for predicting breakage in large populations of agglomerates and was highly versatile: parts of the model could easily be substituted by the researcher according to their specific requirements.
Mass transfer analysis of gas exchange through microperforated packaging films
(University College Cork, 2017) Viana Ramos, Andresa; Oliveira, Jorge C.; Sousa Gallagher, Maria J; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior; Department of Agriculture, Food and the Marine
The primary purpose of this work was to provide robust tools for the design of perforated packaging based on rigorous mathematical methods. A dimensionless correlation was established based on the identification of the variables affecting mass transfer through perforations. It was proved that the diameter of the perforation is the most important parameter. Air velocity and temperature (via its effect on viscosity and density of air) and diffusivity of gases through air are also relevant to this analysis. The Buckingham π Theorem was applied to identify the dimensionless numbers that provide a dimensionless correlation availing of the principle of dynamic similarity to predict the mass transfer coefficients of both oxygen and water vapour through perforations. As films tend to be much more permeable to water than to oxygen, a study on the effect of water (humidity) on films was also performed. It was found that diffusion and hence permeability can be significantly affected by the water content of the films and therefore the humidity of the atmospheres that the films are exposed to on both sides. A methodology was applied combining the William, Landel and Ferry and the Gordon-Taylor equations with the isotherm of water sorption to obtain the correct effective permeability of films during storage depending on the relative humidity. A methodology was also developed to analyse leakage flow in sealed packages in order to identify the relevant parameters that influence their variability and provide the most robust sealing conditions. The results on this thesis provide substantial data and rigorous mathematical approaches for a more efficient and accurate packaging design to achieve maximum shelf life.
Mathematical modelling and optimisation of the formulation and manufacture of aggregate food products
(University College Cork, 2010-07) Baş, Nurşin; Byrne, Edmond P.; Fitzpatrick, John J.; Department of Agriculture, Fisheries and Food, Ireland
In this PhD study, mathematical modelling and optimisation of granola production has been carried out. Granola is an aggregated food product used in breakfast cereals and cereal bars. It is a baked crispy food product typically incorporating oats, other cereals and nuts bound together with a binder, such as honey, water and oil, to form a structured unit aggregate. In this work, the design and operation of two parallel processes to produce aggregate granola products were incorporated: i) a high shear mixing granulation stage (in a designated granulator) followed by drying/toasting in an oven. ii) a continuous fluidised bed followed by drying/toasting in an oven. In addition, the particle breakage of granola during pneumatic conveying produced by both a high shear granulator (HSG) and fluidised bed granulator (FBG) process were examined. Products were pneumatically conveyed in a purpose built conveying rig designed to mimic product conveying and packaging. Three different conveying rig configurations were employed; a straight pipe, a rig consisting two 45° bends and one with 90° bend. It was observed that the least amount of breakage occurred in the straight pipe while the most breakage occurred at 90° bend pipe. Moreover, lower levels of breakage were observed in two 45° bend pipe than the 90° bend vi pipe configuration. In general, increasing the impact angle increases the degree of breakage. Additionally for the granules produced in the HSG, those produced at 300 rpm have the lowest breakage rates while the granules produced at 150 rpm have the highest breakage rates. This effect clearly the importance of shear history (during granule production) on breakage rates during subsequent processing. In terms of the FBG there was no single operating parameter that was deemed to have a significant effect on breakage during subsequent conveying. A population balance model was developed to analyse the particle breakage occurring during pneumatic conveying. The population balance equations that govern this breakage process are solved using discretization. The Markov chain method was used for the solution of PBEs for this process. This study found that increasing the air velocity (by increasing the air pressure to the rig), results in increased breakage among granola aggregates. Furthermore, the analysis carried out in this work provides that a greater degree of breakage of granola aggregates occur in line with an increase in bend angle.
Optimisation of granola breakfast cereal manufacturing process by wet granulation and pneumatic conveying
(University College Cork, 2010-07) Pathare, Pankaj B.; Byrne, Edmond P.; Department of Agriculture, Fisheries and Food, Ireland
This study has considered the optimisation of granola breakfast cereal manufacturing processes by wet granulation and pneumatic conveying. Granola is an aggregated food product used as a breakfast cereal and in cereal bars. Processing of granola involves mixing the dry ingredients (typically oats, nuts, etc.) followed by the addition of a binder which can contain honey, water and/or oil. In this work, the design and operation of two parallel wet granulation processes to produce aggregate granola products were incorporated: a) a high shear mixing granulation process followed by drying/toasting in an oven. b) a continuous fluidised bed followed by drying/toasting in an oven. In high shear granulation the influence of process parameters on key granule aggregate quality attributes such as granule size distribution and textural properties of granola were investigated. The experimental results show that the impeller rotational speed is the single most important process parameter which influences granola physical and textural properties. After that binder addition rate and wet massing time also show significant impacts on granule properties. Increasing the impeller speed and wet massing time increases the median granule size while also presenting a positive correlation with density. The combination of high impeller speed and low binder addition rate resulted in granules with the highest levels of hardness and crispness. In the fluidised bed granulation process the effect of nozzle air pressure and binder spray rate on key aggregate quality attributes were studied. The experimental results show that a decrease in nozzle air pressure leads to larger in mean granule size. The combination of lowest nozzle air pressure and lowest binder spray rate results in granules with the highest levels of hardness and crispness. Overall, the high shear granulation process led to larger, denser, less porous and stronger (less likely to break) aggregates than the fluidised bed process. The study also examined the particle breakage of granola during pneumatic conveying produced by both the high shear granulation and the fluidised bed granulation process. Products were pneumatically conveyed in a purpose built conveying rig designed to mimic product conveying and packaging. Three different conveying rig configurations were employed; a straight pipe, a rig consisting two 45° bends and one with 90° bend. Particle breakage increases with applied pressure drop, and a 90° bend pipe results in more attrition for all conveying velocities relative to other pipe geometry. Additionally for the granules produced in the high shear granulator; those produced at the highest impeller speed, while being the largest also have the lowest levels of proportional breakage while smaller granules produced at the lowest impeller speed have the highest levels of breakage. This effect clearly shows the importance of shear history (during granule production) on breakage during subsequent processing. In terms of the fluidised bed granulation, there was no single operating parameter that was deemed to have a significant effect on breakage during subsequent conveying. Finally, a simple power law breakage model based on process input parameters was developed for both manufacturing processes. It was found suitable for predicting the breakage of granola breakfast cereal at various applied air velocities using a number of pipe configurations, taking into account shear histories.
The post-dehydration processing and the effects on the structural modifications and functionalities of milk protein powders
(University College Cork, 2017) Ji, Junfu; Miao, Song; Cronin, Kevin; Fitzpatrick, John J.; Department of Agriculture, Food and the Marine
The variability of the raw materials, the diversity of the chemical compositions and the heterogeneity of structures are believed to contribute to the complexity in the physicochemical behaviours of dairy powders. Post-dehydration technology is widely used as an effective method to modify the structural properties and potentially improve the functionalities of dairy powder. In the present study, the dairy powders were firstly agglomerated by fluidised bed (FB) to investigate the effects on their rehydration processes. Then milk protein isolate powder (MPI) was used as the model system, which was agglomerated by fluidised bed and high shear mix (HS) granulators, using different liquid binders and comparing different granule sizes. The impact of both agglomeration methods on powder structures, as well as the consequent effects on the rehydration abilities, flowability and water adsorption are investigated. MPI agglomerated by FB had the more irregular shapes and porous structures. However, densely packed structures of HS granules caused the higher bulk density and lower porosity. Their shapes were more like spheres with smoother surfaces. FB agglomeration significantly improved the dynamic wetting of MPI and micellar casein powders, by requiring shorter wetting time, being more quickly penetrated by water droplets and absorbing more water by capillary force. But the influences on whey protein were limited, only if using lecithin as a liquid binder. Agglomeration exhibited no advantageous effects on the solubilisation of milk protein powders. The HS granules even delayed the release of materials. The denselypacked structures made MPI adsorbed least moisture and showed the slowest adsorption kinetics. Meanwhile, these MPI granules have significantly better powder flow behaviours. The study provided information about the post-dehydration process as a useful technique to modify the structures of dairy powders, which could be helpful to enhance the wetting process, control the water adsorption and improve the powder flowability.
Shear effects on the properties and separation characteristics of whey protein precipitates
(University College Cork, 2001-04) Byrne, Edmond P.; Fitzpatrick, John J.; Department of Agriculture, Fisheries and Food, Ireland
Selective isoelectric whey protein precipitation and aggregation is carried out at laboratory scale in a standard configuration batch agitation vessel. Geometric scale-up of this operation is implemented on the basis of constant impeller power input per unit volume and subsequent clarification is achieved by high speed disc-stack centrifugation. Particle size and fractal geometry are important in achieving efficient separation while aggregates need to be strong enough to resist the more extreme levels of shear that are encountered during processing, for example through pumps, valves and at the centrifuge inlet zone. This study investigates how impeller agitation intensity and ageing time affect aggregate size, strength, fractal dimension and hindered settling rate at laboratory scale in order to determine conditions conducive for improved separation. Particle strength is measured by observing the effects of subjecting aggregates to moderate and high levels of process shear in a capillary rig and through a partially open ball-valve respectively. The protein precipitate yield is also investigated with respect to ageing time and impeller agitation intensity. A pilot scale study is undertaken to investigate scale-up and how agitation vessel shear affects centrifugal separation efficiency. Laboratory scale studies show that precipitates subject to higher impeller shear-rates during the addition of the precipitation agent are smaller but more compact than those subject to lower impeller agitation and are better able to resist turbulent breakage. They are thus more likely to provide a better feed for more efficient centrifugal separation. Protein precipitation yield improves significantly with ageing, and 50 minutes of ageing is required to obtain a 70 - 80% yield of α-lactalbumin. Geometric scale-up of the agitation vessel at constant power per unit volume results in aggregates of broadly similar size exhibiting similar trends but with some differences due to the absence of dynamic similarity due to longer circulation time and higher tip speed in the larger vessel. Disc stack centrifuge clarification efficiency curves show aggregates formed at higher shear-rates separate more efficiently, in accordance with laboratory scale projections. Exposure of aggregates to highly turbulent conditions, even for short exposure times, can lead to a large reduction in particle size. Thus, improving separation efficiencies can be achieved by the identification of high shear zones in a centrifugal process and the subsequent elimination or amelioration of such.
Study of the relation between the shape of lacosamide crystals and the composition of crystallization medium
(University College Cork, 2016) Allegaert, Sven; Fitzpatrick, John J.; European Commission
Crystallization is the critical process used by pharmaceutical industries to achieve the desired size, size distribution, shape and polymorphism of a product material. Control of these properties presents a major challenge since they influence considerably downstream processing factors. Experimental work aimed at finding ways to control the crystal shape of Lacosamide, an active pharmaceutical ingredient developed by UCB Pharma, during crystallization was carried out. It was found that the crystal lattice displayed a very strong unidirectional double hydrogen bonding, which was at the origin of the needle shape of the Lacosamide crystals. Two main strategies were followed to hinder the hydrogen bonding and compete with the addition of a Lacosamide molecule along the crystal length axis: changing the crystallization medium or weakening the hydrogen bonding. Various solvents were tested to check whether the solvent used to crystallize Lacosamide had an influence on the final crystal shape. Solvent molecules seemed to slow down the growth in the length axis by hindering the unidirectional hydrogen bonding of Lacosamide crystals, but not enough to promote the crystal growth in the width axis. Additives were also tested. Certain additives have shown to compete in a more efficient way than solvent molecules with the hydrogen bonding of Lacosamide. The additive effect has also shown to be compatible with the solvent effect. In parallel, hydrogen atoms in Lacosamide were changed into deuterium atoms in order to weaken the hydrogen bonds strength. Weakening the hydrogen bonds of Lacosamide allowed to let the crystal grow in the width axis. Deuteration was found to be combinable with solvent effect while being in competition with the additive effect. The Lacosamide molecule was eventually deemed an absolute needle by the terms of Lovette and Doherty. The results of this dissertation are aimed at contributing to this classification.
Sustainability analysis of biopharmaceuticals manufacturing
(University College Cork, 2020-04-30) Lalor, Fergal; Byrne, Edmond P.; Fitzpatrick, John J.; Sage, Colin
The production of biopharmaceutical treatments is increasing globally at a rapid pace, leading to the treatment of more and more disorders, many of which historically were untreatable and debilitating. This increase in production poses sustainability concerns, with economic unsustainability from erratic returns on investment, societal concerns around treatment cost and access, and a dearth of published research on pathways to environmentally sustainable production methods. Recombinant protein production by perfusion cell culture under stainless-steel and single-use technologies was investigated using life cycle assessment (LCA) to determine the impact on environmental factors. The ReCiPe for LCA method was utilised, and the single-use scenario was found to result in 40% impacts than stainless-steel alternative across all production volumes. Factors influencing the difference in environmental impacts include infrastructural variables, such as the electricity source to the facility, and process variables, such as the interval between ultrafiltration/diafiltration batches. The feasibility of environmentally sustainable manufacturing processes were investigated, with novel technologies such as water-for-injection (WFI) production by reverse osmosis, the use of biologically-sourced polymeric materials for single-use items and the benefits of increased containment using single-use equipment on cleanroom maintenance evaluated. The results of this analysis indicate reductions in environmental impacts across both single-use and stainless-steel scenarios of 60%, but with further research required to fully understand the process impacts resulting from adopting these technologies. A multiple-criteria decision-making framework was developed to evaluate the economic, environmental and social sustainability of biopharmaceutical manufacturing processes under varying value orientations, enabling the comparison of treatments produced under different modalities. This framework may be utilised to assess treatments for regulatory approval and governmental reimbursement in a holistic manner, as opposed to a reductionist economic standpoint. Further research is required to account for greater complexities in the biopharmaceutical industrial system such as feedback loops between various stakeholders and to provide and document indices from existing processes to be used for evaluation of prospective treatments.

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