Intensified biodiesel production from waste cooking oil and flow pattern evolution in small-scale reactors

In this paper, the transesterification reaction of waste cooking oil (WCO) with methanol using KOH as catalyst to produce biodiesel was performed in a micro-reactor (1 mm ID) using a cross-flow inlet configuration. The effects of different variables such as, methanol-to-oil molar ratio, temperature, catalyst concentration, and residence time on biodiesel yield, as well as the associated flow patterns during the transesterification reaction were investigated and the relationship between flow characteristics and mass transfer performance of the system was examined. The work reveals important aspects and the links between the hydrodynamic behaviour and the mass transfer performance of the intensified reactors. It was found that high yield (>90%) of biodiesel can be achieved in one-stage reaction using cross-flow micro-reactors for a wide range of conditions, i.e., methanol-to-oil molar ratio: 8–14, catalyst concentration: 1.4%–1.8% w/w, temperature: 55°C–60°C, and residence times: 55–75 s

Hydrodynamics and mass transfer in segmented flow small channel contactors for uranium extraction

In this work, the extraction of U(VI) by tributyl phosphate (TBP) is studied in small channels of different sizes, operated in segmented flow. The variables analysed include the channel diameter (1–4 mm I.D.), mixture velocity (1.06 - 4.24 cm s−1), volume fraction of the continuous phase (between 0.200 and 0.500), and concentration of extractant (TBP 30% v/v in kerosene and TBP 100%). The hydrodynamic characteristics of the flow, such as plug and slug lengths, specific interfacial area, and dispersed phase holdup, were obtained experimentally using high-speed imaging, while the pressure drop was measured with a differential pressure transducer. These parameters were correlated to the studied variables. The concentration of uranium in the aqueous phase was measured with UV-vis spectroscopy, and the mass transfer coefficients were compared with the predictions of a numerical model of segmented flow developed in Comsol Multiphysics, with good agreement

Predictive model for the scale-out of small channel two-phase flow contactors

In this paper, double manifolds are theoretically investigated for the scale-out of two-phase incompressible flows in small channels. Statistical descriptors are proposed to characterise the maldistribution of the total flow rate and the ratio of the flow rates in the two-phase channels, based on the variances and covariance of the flow rates of the two fluids. A novel resistance network model is developed that relates the flowrates of the fluids in the two-phase channels to the hydraulic resistances of the manifold. The statistical descriptors and the resistance network model are then used to develop relationships between the maldistribution coefficients and the hydraulic resistances of the double manifold, the overall pressure drop and the pumping power requirements for different parallel channel numbers. Based on these, scaling laws are proposed that maintain a constant degree of maldistribution for a scale-up factor up to 102. Double manifolds designed using these scaling laws have a constant pressure drop as the number of channels increases, whilst the power requirements increase linearly. The power requirements are inversely proportional to the phase ratio maldistribution descriptor. Recommendations for the design of double manifolds for the scale-out of two-phase systems are proposed

Osteogenic potential of murine periosteum for critical-size cranial defects.

Tissue engineering of bone has combined bespoke scaffolds and osteoinductive factors to maintain functional osteoprogenitor cells, and the periosteum has been confirmed as a satisfactory source of osteoblasts. Suitable matrices have been identified that support cell proliferation and differentiation, including demineralised bone matrix (both compatible and osteoinductive) and acellular human dermis. We have evaluated the osteogenic potential of an osteogenic unit, developed by combining periosteum, demineralised bone matrix, and acellular human dermis, in rodents with critical-size cranial defects. Briefly, remnants from the superior maxillary periosteum were used to harvest cells, which were characterised by flow cytometry and reverse retrotranscriptase-polymerase chain reaction (RT-PCR). Cells were cultured into the osteogenic unit and assessed for viability before being implanted into 3 rodents, These were compared with the control group (n=3) after three months. Histological analyses were made after staining with haematoxylin and eosin and Von Kossa, and immunostaining, and confirmed viable cells that stained for CD90, CD73, CD166, runt-related transcription factor, osteopontin, and collagen type I in the experimental group, while in the control group there was only connective tissue on the edges of the bone in the injury zone. We conclude that osteogenic unit constructs have the osteogenic and regenerative potential for use in engineering bone tissue

Mechanical Influences on Morphogenesis of the Knee Joint Revealed through Morphological, Molecular and Computational Analysis of Immobilised Embryos

Very little is known about the regulation of morphogenesis in synovial joints. Mechanical forces generated from muscle contractions are required for normal development of several aspects of normal skeletogenesis. Here we show that biophysical stimuli generated by muscle contractions impact multiple events during chick knee joint morphogenesis influencing differential growth of the skeletal rudiment epiphyses and patterning of the emerging tissues in the joint interzone. Immobilisation of chick embryos was achieved through treatment with the neuromuscular blocking agent Decamethonium Bromide. The effects on development of the knee joint were examined using a combination of computational modelling to predict alterations in biophysical stimuli, detailed morphometric analysis of 3D digital representations, cell proliferation assays and in situ hybridisation to examine the expression of a selected panel of genes known to regulate joint development. This work revealed the precise changes to shape, particularly in the distal femur, that occur in an altered mechanical environment, corresponding to predicted changes in the spatial and dynamic patterns of mechanical stimuli and region specific changes in cell proliferation rates. In addition, we show altered patterning of the emerging tissues of the joint interzone with the loss of clearly defined and organised cell territories revealed by loss of characteristic interzone gene expression and abnormal expression of cartilage markers. This work shows that local dynamic patterns of biophysical stimuli generated from muscle contractions in the embryo act as a source of positional information guiding patterning and morphogenesis of the developing knee joint

Scale-Up Studies for Co/Ni Separations in Intensified Reactors

In this paper, the effect of the scalability of small-scale devices on the separation of Co(II) from a binary Co(II)/Ni(II) mixture in a nitric acid solution by an organic Cyanex 272/TBP/kerosene (Exxsol D80) phase is studied. In particular, circular channels with diameters of 1, 2, and 3.2 mm are considered. The results were compared against those from a confined impinging-jets (CIJ) cell with a main channel diameter of 3.2 mm. The effects of total flowrate, residence time, Cyanex 272 concentration, and flowrate ratio on the mass transfer performance were investigated. It was found that at increased channel size, the throughputs were also increased but the extraction percentages remained the same. Higher extraction percentages were obtained by using the CIJ configuration at short residence times. However, for longer residence times, the mass transfer coefficients were similar and capillary channels should be preferred over the CIJ because of the ease of separation of the two phases at the end of the unit. The overall mass transfer coefficients ranged between 0.02 and 0.14 s-1 for the capillary channels during plug flow and between 0.05 and 0.45 s-1 for the CIJ cells during dispersed flow