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    ABSTRACT: The emptying of pipework from fluids of high viscosity is a significant multiphase flow problem in many food and personal care industries. Maximising product recovery whilst minimising cleaning time and effluent volume is important in minimising the environmental footprint of the plant. The cleaning of pipework fully filled by toothpaste by water under different process conditions has been studied and monitored by weighing pipes at intervals. Three flow regimes have been identified; a short core removal stage of product recovery, before water breaks through the filled pipe, and two in subsequent cleaning, film removal when there is a continuous wavy annular film on the wall, and patch removal in which the material is present as patches on the wall. The amount of product recovered in core removal is here not a function of flow conditions; however, conditions during core removal significantly affect the overall cleaning time. Overall cleaning time can be reduced by at least 25% by selecting the best removal conditions in the different stages. It is hypothesised that this is due to changes in the wall layer induced during core removal, with a very wavy wall layer leading to rapid subsequent removal. If this effect could be understood and scaled up it may be possible to improve commercial cleaning processes.
    Chemical Engineering Research and Design 11/2014; 92(11). DOI:10.1016/j.cherd.2014.01.001
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    ABSTRACT: Lubrication behaviour of foodstuff is related to mouthfeel perception and consumer appreciation. Soft tribology of food related products has mainly been investigated with semi-solid food, polymer solutions and water continuous emulsions, and this is the first study aimed at investigating soft tribolocigal behaviour of oil continuous emulsions. All the emulsions considered here exhibit the same trends in terms of lubrication behaviour, where little boundary lubrication is observed at the entrainment speed considered. The volume of dispersed aqueous phase affects overall tribology of oil continuous emulsions via an increase in their dynamic viscosity. Increasing the phase volume leads to an increase in friction in the elastohydrodynamic regime whereas the lubrication in the boundary regime is improved. Elastohydrodynamic lubrication is independent of the aqueous phase composition and the type of emulsifier present at the water–oil interface. These parameters affect boundary lubrication of emulsion systems exhibiting droplet size bigger than the elastohydrodynamic oil film thickness. This is expected to have a significant impact on the design of low fat emulsions that match the lubrication properties of their full fat version.
    Journal of Food Engineering 10/2014; 139:24–30. DOI:10.1016/j.jfoodeng.2014.04.007
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    ABSTRACT: A nickel-silica core@shell catalyst was applied for a methane tri-reforming process in a fixed-bed reactor. To determine the optimal condition of the tri-reforming process for production of syngas appropriate for methanol synthesis the effect of reaction temperature (550–750 °C), CH4:H2O molar ratio (1:0–3.0) and CH4:O2 molar ratio (1:0–0.5) in the feedstock was investigated. CH4 conversion rate and H2/CO ratio in the produced syngas were influenced by the feedstock composition. Increasing the amount of steam above the proportion of CH4:H2O 1:0.5 reduced the H2:CO molar ratio in produced syngas to ∼1.5. Increasing oxygen partial pressure improved methane conversion to 90% at 750 °C. At low ∼550 °C reaction temperature the tri-reforming process was not effective with low hydrogen production (H2 yield ∼20%) and very low <5% CO2 conversion. Increasing reaction temperature increased hydrogen yield to ∼85% at 750 °C. From all the tested reaction conditions the optimal for tri-reforming over the 11%Ni@SiO2 catalyst was: feed composition with molar ratio CH4:CO2:H2O:O2:He 1:0.5:0.5:0.1:0.4 at T = 750 °C. The results were explained in the context of characterisation of the catalysts used. The obtained results showed that the tri-reforming process can be applied for production of syngas with composition suitable for methanol synthesis.
    International Journal of Hydrogen Energy 08/2014; 39(24). DOI:10.1016/j.ijhydene.2014.06.071
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    ABSTRACT: The development of new infrastructure is often a consideration in the introduction of new innovations. Currently there is some confusion around how to develop a hydrogen infrastructure to support the introduction of FCVs. Lessons can be learned from similar technology introduction in the past and therefore this paper investigates how mobile phone infrastructure was developed allowing the mass-market penetration of mobile phones. Based on this successful infrastructural development suggestions can be made on the development of a hydrogen infrastructure. It is suggested that a hydrogen infrastructure needs to be pre-developed 3–5 years before the market introduction of FCVs can successfully occur. A lack of infrastructural pre-development will cause to the market introduction of FCVs to fail.
    International Journal of Hydrogen Energy 05/2014; 39(16):8185–8193. DOI:10.1016/j.ijhydene.2014.03.156
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    ABSTRACT: The aim of this research was to control the mechanical properties of gellan through the addition of a secondary polymer network, for use as an alternative to current tissue regeneration techniques. Cartilage and skin are complex structures, and a complex structure would therefore be required in order to closely mimic their mechanical properties. In this research, the gellan gels were strengthened through the addition of Poly (vinyl alcohol) (PVA), as the secondary polymer. Compressive strength and compressive stiffness were both increased with the addition on PVA, until 10-15% (w/w). This research has shown that gellan and PVA are phase separated, and the decrease on mechanical strength and stiffness is strongly affected by the polymer overlap concentration, occurring at 14% (w/w). (C) 2014 The Authors. Published by Elsevier Ltd.
    Food Hydrocolloids 05/2014; 42. DOI:10.1016/j.foodhyd.2014.05.001
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    ABSTRACT: Modern emulsion processing technology is strongly influenced by the market demands for products that are microstructure-driven and possess precisely controlled properties. Novel cost effective processing techniques, such as membrane emulsification, have been explored and customised in search for better control over the microstructure, and subsequently the quality of the final product. Part A of this review reports on the state-of-the-art in membrane emulsification techniques, focusing on novel membrane materials and proof of concept experimental set-ups. Engineering advantages and limitations of a range of membrane techniques are critically discussed and linked to a variety of simple and complex structures (e.g. foams, particulates, liposomes etc.) produced specifically using those techniques.
    Journal of the Science of Food and Agriculture 03/2014; 94(4). DOI:10.1002/jsfa.6444
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    ABSTRACT: Membrane emulsification is a promising process for formulating emulsions and particulates. It offers many advantages over conventional 'high-shear' processes with narrower size distribution products, higher batch repeatability and lower energy consumption commonly demonstrated at a small scale. Since the process was first introduced around 25 years ago, understanding of the underlining mechanisms involved during microstructure formation has advanced significantly leading to the development of modelling approaches that predict processing output; e.g. emulsion droplet size and throughput. The accuracy and ease of application of these models is important to allow for the development of design equations which can potentially facilitate scale-up of the process and meet the manufacturer's specific requirements. Part B of this review considers the advantages and disadvantages of a variety of models developed to predict droplet size, flow behaviour and other phenomena (namely droplet-droplet interactions), with presentation of the appropriate formulae where necessary. Furthermore, the advancement of the process towards an industrial scale is also highlighted with additional recommendations by the authors for future work.
    Journal of the Science of Food and Agriculture 03/2014; 94(4). DOI:10.1002/jsfa.6443
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    ABSTRACT: This study investigated the in vitro acid-induced gelation of mixed systems of two biopolymers; low acyl and high acyl gellan gum. Rheological and texture analysis showed that these mixed gels displayed textures that lay between the material properties exhibited for the low and high acyl variants. DSC analysis showed that mixtures of the low acyl and high acyl forms exhibit two separate conformational transitions at temperatures coincident with each of the individual biopolymers. Various metabolically relevant pH environments and hydrocolloid concentrations were investigated. These resulted in very different acid gelled structures, which were characterised by texture analysis. The structures of the acid gels were shown to depend upon the pH, hydrocolloid concentration and proportion of each biopolymer used during their production. A selection of these mixed gellan structures were assessed post-production in terms of their response to prolonged exposure to an acidic (pH 1), stomach-like, environment. This resulted in a significant increase in the gel strength, regardless of the biopolymer proportions. The high acyl gellan was less acid-sensitive, and subsequently no evidence of acid gelation was observed with high acyl gellan at a proportion greater than 60% of the total biopolymer. The findings presented here demonstrate that structuring as well as de-structuring of mixed gellan acid gels can be controlled in acidic environments similar to those that are present in the stomach after food consumption.
    Food Hydrocolloids 03/2014; 35(100):522-530. DOI:10.1016/j.foodhyd.2013.07.014
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    ABSTRACT: Converting glycerol, a by-product from biodiesel production into useful products and energy could contribute to a positive life cycle for the biodiesel process. One kg of glycerol is produced for every 10 kg of biodiesel and has the potential to be used as a source of H2, syngas or CH4 by an appropriate conversion process. Catalytic Supercritical Water Gasification (CSCWG) processing of crude glycerol solutions is one such viable option. Above its critical point [>221 barg, >374 °C], the properties of water, such as the low relative permittivity and high ionic product make it capable of dissolving non-polar organic compounds, allowing for high reactivity, and the ability to act as an acid/base catalyst. In this work, the degradation of glycerol by CSCWG at temperatures [400–550 °C] and pressures [170–270 barg] was investigated using a packed bed reactor (PBR) containing a Fe2O3 + Cr2O3 catalyst. Glycerol feed concentrations were between 2 and 30 wt% at flow rates from [10–65 ml/min], which gave weight hourly space velocities (WHSV) of [38–125 h−1]. The results indicated that high temperature and low feed concentration tended to increase the gas yield and selectivity toward H2 production with some char (<2.7 wt%). Syngas of up to 64 mole% was obtained with minimum 4:1 mole ratio of H2:CO. High yields of volatile hydrocarbons were also obtained: 14 and 69 mole % for methane and ethylene, respectively, which could be used for energy generation in SOFCs or turbines, reformed to syngas or converted to chemicals by an appropriate route. Pressure had little effect on the gas yields in the subcritical water region, but had a positive effect on H2 and CO2 in the supercritical region where char formation also was increased resulting in loss of catalyst activity. Complete conversion of glycerol was achieved at high temperature (550 °C). A maximum of 11 wt% liquid products were obtained at 400 °C (mainly allyl alcohol, methanol and formaldehyde). Catalyst stability was also evaluated, which was found to reach relative stability in the supercritical water environment for up to 9 h of operation.
    Renewable Energy 01/2014; 62:353-361.
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    ABSTRACT: Hydroxyapatite nanoparticles have uses in a number of fields where the required particle size distribution and morphology can be application specific. Hydroxyapatite particles were prepared using a sol–gel technique in order to study the effects of agitation rate and temperature on particle size. Agitation rates were investigated at 200 rpm, 1200 rpm, 2200 rpm using an overhead stirrer, and 3000 rpm and 7000 rpm using a mechanical blade homogeniser at 20 and 40 °C. Primary particles between 43 and 68 nm can be obtained as sized by TEM images, while from Scherrer's formula using XRD data, these were found to be between 38 and 56 nm. Dynamic light scattering was also used to size the particle agglomerates which gave mean particle sizes between 145 and 219 nm. Above 2200 rpm the agitation rate did not significantly affect the size of the agglomerate particle size and inferred that kinetic coagulation had led to the formation of stable aggregates. An increase in process temperature from 20 to 40 °C had a slight affect on particle size.The different particle sizes were explained in terms of power input and turbulence within the mixing zone. Different particle morphologies were obtained at different agitation rates which were dependent on equipment selection. Cuboid-like particles were obtained at lower agitation rates with the overhead stirrer, while elongated particles were obtained at high shear created by the homogeniser. Co-precipitating Mg2 + into the hydroxyapatite structure was observed to also decrease particle size at a higher agitation rates and MgCl2 concentrations.
    Powder Technology 12/2013; 218:109–118. DOI:10.1016/j.powtec.2011.11.049
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