Adam Donaldson

Fluid dynamics topics in bloodstain pattern analysis: Comparative review and research opportunities

This comparative review highlights the relationships between the disciplines of bloodstain pattern analysis (BPA) in forensics and that of fluid dynamics (FD) in the physical sciences. In both the BPA and FD communities, scientists study the motion and phase change of a liquid in contact with air, or with other liquids or solids. Five aspects of BPA related to FD are discussed: the physical forces driving the motion of blood as a fluid; the generation of the drops; their flight in the air; their impact on solid or liquid surfaces; and the production of stains. For each of these topics, the relevant literature from the BPA community and from the FD community is reviewed. Comments are provided on opportunities for joint BPA and FD research, and on the development of novel FD-based tools and methods for BPA. Also, the use of dimensionless numbers is proposed to inform BPA analyses.

Advancements and future directions in enzyme technology for biomass conversion.

Enzymatic hydrolysis of pre-treated lignocellulosic biomass is an ideal alternative to acid hydrolysis for bio-ethanol production, limited primarily by pre-treatment requirements and economic considerations arising from enzyme production costs and specific activities. The quest for cheaper and better enzymes has prompted years of bio-prospecting, strain optimization through genetic engineering, enzyme characterization for simple and complex lignocellulosic feedstock, and the development of pre-treatment strategies to mitigate inhibitory effects. The recent shift to systematic characterizations of de novo mixtures of purified proteins is a promising indicator of maturation within this field of study, facilitating progression towards feedstock assay-based rapid enzyme mixture optimization. It is imperative that international standards be developed to enable meaningful comparisons between these studies and the construction of a database of enzymatic activities and kinetics, aspects of which are explored here-in. Complementary efforts to improve the economic viability of enzymatic hydrolysis through process integration and reactor design are also considered, where membrane-confinement shows significant promise despite the associated technological challenges. Significant advancements in enzyme technology towards the economic conversion of lignocellulosic biomass should be expected within the next few years as systematic research in enzyme activities conforms to that of traditional reaction engineering.

Enhancement of Interphase Transport in Mini-/Microscale Applications Using Passive Mixing

Structured mini-/microscale reactors continue to receive attention from both industry and academia due to their low pressure drop, high heat and mass transfer rates, and ease of scale-up relative to conventional reactor technology. Commonly considered for reactions such as hydrogenations, hydrodesulfurization, oxidations, and Fischer–Tropsch synthesis, the performance of these systems is highly dependent on mixing and the interfacial area between phases. While existing literature describes the initial flow patterns generated by a broad range of two-phase contactors, few studies explore the dynamic impacts of downstream passive mixing elements. Experimental and computational methodologies for characterizing two-phase flow pattern transitions, pressure drop, and heat and mass transfer are discussed, with relevant examples for serpentine and Venturi-based passive mixing designs. The efficacies of these two configurations are explored in the context of pressure drop, conditions leading to significant interface renewal, and design considerations for optimizing mass transfer. Challenges associate with the characterization of multiphase flow through these systems are highlighted, and strategies suggested for both experimental and computational analysis of dynamic flow patterns and fluid–fluid interactions.

Transport Phenomena in Two-Phase Liquid-Liquid Micro-Reactors

Micro-reactors offer distinct advantages over batch reactors currently used within the pharmaceutical and fine chemical industries. Their high surface area-to-volume ratios allow for increased heat and mass transfer, which is important for controlling reaction selectivity. In addition, micro-reactors are compatible with continuous processing technology, circumventing the time delays inherent to batch systems. Rapid mixing of reactants within micro-reactors is, however, limited by the inherent difficulty of generating turbulence at reduced geometry scales. Several different passive mixing strategies have been proposed in order to produce eddy-based secondary flows and chaotic mixing. This study examines the effectiveness of these strategies by comparing the energy-density normalized heat and mass transfer coefficients for a selection of industrial micro-reactors. First single, then two-phase liquid-liquid experiments were conducted. Pressure drop measurements were obtained to calculate friction factors and to verify the presence of eddy-based secondary flows. A hot heat exchange fluid and temperature measurements were used to estimate the internal convective heat transfer coefficients within each structure. Volumetric mass transfer coefficients were also determined for the mutual extraction of partially miscible n-butanol and water. Semi-empirical correlations for the reactors’ friction factor and Nusselt number as well as a description of the overall mass transfer coefficient based on energy dissipation are presented.Copyright

Coupled Transport Phenomena in Corrugated Photocatalytic Reactors

Abstract Corrugated reactors are known for their use in applications requiring UV-exposure, whereby media flowing within the corrugated channel react with a photo-active catalyst impregnated on the surface ( i.e. TiO 2 ). The performance in these systems is dependent on catalyst properties and reactivity for a given light source, in conjunction with the coupled transport of reactants within the media and photons falling incident to the catalyst surface. Experimental and computational analyses of local mass transfer and radiation patterns for a broad range of corrugation angles, depths, and non-idealities introduced during manufacture ( i . e . fold curvature) are thus integrated to the design and optimization of these systems. This work explores techniques for determining incident energy distributions on the surface of corrugated reactor geometries with non-ideal cross-sectional profiles, and the local and overall mass transfer rates obtained using computational fluid dynamics and experimental analysis. By examining the reaction kinetics for the photo-degradation of 4-chlorophenol over a TiO 2 catalyst, the effects of surface area, energy incidence with photon recapture, and local mass transfer on overall reactor performance are presented to highlight optimization concerns for these types of reactors.

Monitoring of Anti-Caking Solution Preparation and Loading duringLoadout Treatment of Potash Using FT-NIR

Fourier transform near-infrared spectroscopy is presented as a novel method for monitoring anti-caking reagent preparation and loading ratio on granular potash samples during loadout. Using commercial anti-caking agents and granular samples obtained from an operational loadout facility, amine weight percent in the anti-caking solution was determined between 0 and 7 wt% to an accuracy of ± 0.1 wt%, while the loading ratio was determined between 0 and 4.3 lb/ton to within an accuracy of 0.1 to 0.3 lb/ton, depending on the sample heterogeneity. These errors are comparable to current analysis techniques, with minimal sample preparation and an analysis time of seconds. FT-NIR is thus presented as a novel monitoring method for these applications within the potash processing industry

NIR-Based Simultaneous Measurement of Amine Loading and Degree ofNeutralization during Flotation Reagent Preparation for Potash Processing

A continuous spectroscopy-based monitoring approach of the amine reagent preparation prior to flotation processing was investigated. The process involved the neutralization of a long carbon chain amine, C16-C20, with hydrochloric acid. Current methods of monitoring the degree of neutralization, controlling the HCl addition, and monitoring the amine content were based on pH measurements, with out-of-line sample lab-validation carried out using titration-based methods. Industry feedback indicated this method was prone to error and had resulted in challenges in process control. This work demonstrates a novel method of measuring both amine content and degree of neutralization using a mini-fluidic reactor and FT-NIR system equipped with a flow-through heated transmission cell. Analysis of the spectral response for wavenumbers in the range of 4,258-4,400 cm-1 yielded amine content and degree of neutralization measurements accurately to within ± 0.065 wt%, and ± 6.0% margin of errors, respectively. This led to monitoring intensification to increase KCl recoveries in flotation processing.

Limestone's performance as a solid adsorbent for HF and HCl generated in refrigerant destruction applications

The viability of two solid adsorbents, limestone and cement powder, for use in a flow-through packed-bed column for HCl and HF gas neutralization following refrigerant destruction was studied. Neutralization tests performed at 408 K using 5% HCl in N2 and 5% HF in N2, showed that limestone had a significantly higher adsorption capacity for both HF and HCl. ∼49% of fed HCl, and between 7.8%–16.2% of fed HF gases were adsorbed by 7 g of limestone for a gas flow rate of 6.67×10−6 m3/s (STP) over 30 to 180 minutes. Effective diffusivities (De) of HCl and HF into the limestone particles were 1.5×10−9 and 2.2×10−9 m2/s, respectively, indicating that a solid diffusion mechanism dominance would limit the suitability of this method as a solid adsorbent in the tested form. Under these conditions, complete particle conversion times were 227 hours for HCl-limestone and 154 hours for HF-limestone. Considering the long conversion times observed, shorter conversion times would require micron-scale particle sizes, suitable for entrained flow but not for a packed-bed arrangement. A Na2CO3/Limestone slurry used to neutralize the reactor effluent proved efficient within this system, and may be a more suitable alternative for acid neutralization involving HF.