archives@tulane.edu / N/A / 1 / Savannah Steadman

The mechanism of how pulsatile flow affects flux behaviour in crossflow micro-filtration was investigated. The effects of pulsatile flow were sub-divided into shear effects and backflushing effects. A servo-valve hydraulic piston pump was applied to generate pulsatile flows in the membrane module with particular waveforms. Four types of fluid pulsation with specific flow-rate and pressure waveforms were produced for experimental tests. Two parameters, /dVcf\dt/ maxand Pmin, were examined independently for their effect during pulsatile flow, which was estimated by comparing the cake resistance during steady flow and pulsatile flow at the same mean crossflow velocity, trans-membrane pressure and membrane resistance. Filtration tests for all the pulsatile flows with clean water confirmed that pulsatility only affects cake depositions. Without particles, no flux improvement was obtained. The results for the microfiltration of 0.5g/1 silica suspension showed that for pulsatile flows without backflushing (i.e. no negative transmembrane pressure peak), the fluid pulsation decreased cake resistance when the shear related parameter /dVcf\dt/max exceeded a critical value for each given waveform. When the instantaneous transmembrane pressure reached negative values, i.e. back-flushing occurred, the cake resistance was reduced for all pressure waves tested. Cake resistance was reduced more for more negative P min. With two of the waveforms tested, the cake resistance was almost completely eliminated. In contrast, the shear affected cake resistance reduction differently for each waveform. Comparing cake reduction results for different pulsatile waveforms, it was found that, for the square wave, the cake resistance reduction was higher for both shear and backflushing effect tests, while for the short spike waveform, the cake resistance reduction was lower. The flux waveforms were seen to follow the variations in transmembrane pressure. The flux response time was longer than the time required for the pressure changes, but was not dependent on the direction of the pressure change.

In this study, Smiles?? sorptivity-diffusivity numerical analysis is demonstrated to offer a comprehensive description of dead-end constant-pressure compressible cake filtration for water treatment. In addition to providing an insight on filtration performance and cake behaviour in terms of cake hydraulic permeability and compressibility in good agreement with the results derived using Ruth??s conventional cake filtration theory, the sorptivity-diffusivity model can be used to gain further information on depth-dependent local cake properties and extend our knowledge on the effect of feed suspension conditions (including solution composition, coagulant dosage and mixing) on the characteristics of the particulate assemblages (including size, structure and strength). Feed suspension conditions and primary particle properties exert significant effect on the characteristics of particles in suspensions and the resultant particulate assemblages. In the non-coagulated latex systems, an increase in ionic strength resulted in a suppression of the electric double layer of latex particles as indicated by a significant drop in the zeta potential of the feed suspension which lead to a dramatic reduction in cake hydraulic permeability. In the non-coagulated montmorillonite systems, feed suspensions with high ionic strength (1 M Na+, 50 mM Ca2+ and 50 mM Fe2+) were associated with larger suspended solids which appeared to form assemblages with nematic structures that are denser yet more permeable when compared to those with low ionic strength (0.1 M Na+, 1 mM Ca2+ and 2 mM Fe2+) which appeared to form highly ??cross-linked?? voluminous honeycomb type gel of very low permeability. Pre-coagulation of latex and montmorillonite suspensions with Al-based coagulants (alum and ACH) both resulted in formation of very large flocs which subsequently formed highly permeable solid assemblages. In the latex systems, the ratio of optimal alum to ACH dose was approximately 5:1 on a total coagulant mass basis and 1.3:1 as Al while the ratio of optimal alum to ACH dose was as high as 22:1 on a total coagulant mass basis and 6:1 as Al in the montmorillonite systems. Although both alum and ACH resulted in comparable filtration performances, the distinction in Al concentration and results of local cake properties analysis indicated the presence of different cake structures presumably due to the formation of different Al species.

Dans les procédés de coagulation/filtration, la récupération des agrégats dans la phase liquide est une étape cruciale pour l'efficacité de la séparation. Une problématique liée à la filtration est qu'en réponse à la contrainte appliquée, le dépôt formé en surface du filtre peut s'effondrer, impliquant une diminution de sa porosité et perméabilité. L'objet de ce travail a été d'étudier les mécanismes de restructuration de dépôts à travers une approche expérimentale multi-échelle afin d'améliorer la maîtrise de leurs propriétés de filtration. Les propriétés mécaniques et structurales de dépôts obtenus à partir de dispersions colloïdales de silice (Ludox et Klebosol) agrégées par un polycation Al137+ ou un cation divalent Ca2+ ont été analysées par DPAN et MET. Ces investigations ont permis de décrire l'effondrement d'un dépôt suivant un mécanisme de restructuration général contrôlé par la force des liaisons. L'étude menée sur l'impact de la restructuration sur les propriétés de filtration des dépôts a montré que la compressibilité et la perméabilité d'un dépôt dépendent principalement de la résistance à la rupture des liaisons interparticulaires plutôt que des propriétés fractales initiales des agrégats.

<p>High temperature filtration in combustion and gasification processes is a highly interdisciplinary field. Thus, particle technology in general has to be supported by elements of physics, chemistry, thermodynamics and heat and mass transfer processes. This topic can be addressed in many ways, phenomenological, based on the up stream processes (i.e. dust/aerosol formation and characterisation) or apparatus oriented.</p><p>The efficiency of the thermochemical conversion process and the subsequent emission control are major important areas in the development of environmentally sound and sustainable technology. Both are highly important for combustion and gasification plant design, operation and economy. </p><p>This thesis is divided into four parts:</p><p>I. High temperature cleaning in combustion processes.</p><p>II. Design evaluations of the Panel Bed Filter technology.</p><p>III. Biomass gasification</p><p>IV. High temperature cleaning of biomass gasification product gas</p><p>The first part validates the filter performance through field experiments on a full scale filter element employed to a biomass combustion process and relates the results to state of the art within comparable technologies (i.e. based on surface filtration). The derived field experience led to new incentives in the search for a simplified design featuring increased capacity. Thus, enabling both high efficiency and simplified production and maintenance. A thorough examination of design fundamentals leading to the development of a new filter geometry is presented.</p><p>It is evident that the up-stream process has significant influence upon the operation conditions of a filter unit. This has lead to a detailed investigation of some selected aspects related to the thermochemical conversion. Furthermore, the influence of fuel characteristics upon conversion and product gas quality is discussed.</p><p>The last part discusses the quality of biomass gasification product gas and requirements put upon the utilisation of this gas in turbines, diesel engines or other high temperature applications. Filtration experiments conducted on product gas derived from wood gasification are reported and discussed.</p>

Commercial Magnafloc 1011and in-house synthesized Al-PAM were used as flocculants for model tailings, laboratory extraction tailings and tailings from paraffin froth treatment unit. The polymers were tested for their flocculation ability in settling and filtration. For model tailings, both polymers showed excellent ability to improve the settling and filtration performance. Magnafloc 1011 is found sensitive to overdosing, but Al-PAM is not sensitive to the dosage within the tested range. For the laboratory extraction tailings, both polymers showed excellent ability to enhance settling. Al-PAM performed very well as a filtration aid. The moisture of the cake obtained from tailings derived from a low fines ore was 6.6 1.2wt% and that from a high fines ore was 16.9 0.8wt%. However, Magnafloc 1011 was found not effective as a filtration aid. For the froth treatment tailings, Al-PAM improved the settling and filterability dramatically. Although the moisture of the cake obtained was 42.5wt%, no free water is seen visually in the cake. The solid cake is self-supportive and remains intact. This class of Al-PAM polymers can provide an alternative approach for oil sands tailings disposal that can potentially eliminate tailings ponds. / Chemical Engineering

High temperature filtration in combustion and gasification processes is a highly interdisciplinary field. Thus, particle technology in general has to be supported by elements of physics, chemistry, thermodynamics and heat and mass transfer processes. This topic can be addressed in many ways, phenomenological, based on the up stream processes (i.e. dust/aerosol formation and characterisation) or apparatus oriented. The efficiency of the thermochemical conversion process and the subsequent emission control are major important areas in the development of environmentally sound and sustainable technology. Both are highly important for combustion and gasification plant design, operation and economy. This thesis is divided into four parts: I. High temperature cleaning in combustion processes. II. Design evaluations of the Panel Bed Filter technology. III. Biomass gasification IV. High temperature cleaning of biomass gasification product gas The first part validates the filter performance through field experiments on a full scale filter element employed to a biomass combustion process and relates the results to state of the art within comparable technologies (i.e. based on surface filtration). The derived field experience led to new incentives in the search for a simplified design featuring increased capacity. Thus, enabling both high efficiency and simplified production and maintenance. A thorough examination of design fundamentals leading to the development of a new filter geometry is presented. It is evident that the up-stream process has significant influence upon the operation conditions of a filter unit. This has lead to a detailed investigation of some selected aspects related to the thermochemical conversion. Furthermore, the influence of fuel characteristics upon conversion and product gas quality is discussed. The last part discusses the quality of biomass gasification product gas and requirements put upon the utilisation of this gas in turbines, diesel engines or other high temperature applications. Filtration experiments conducted on product gas derived from wood gasification are reported and discussed.

The membrane bioreactor (MBR) is becoming increasingly popular for wastewater treatment, mainly due to its capability of producing high quality effluent with a relatively small footprint. However, high plant maintenance and operating costs due to membrane fouling limit the wide spread application of MBRs. Membrane fouling generally depends on the interactions between the membrane and, the activated sludge mixed liquor, which in turn, are affected by the chosen operating conditions. The present research study aimed to explore the process performance and membrane fouling in the membrane enhanced biological phosphorus removal (MEBPR) process under different operating conditions by, (1) comparing two MEBPRs operated in parallel, one with constant inflow and another with a variable inflow, and by, (2) operating the MEBPRs with different solids retention times (SRT). On-line filtration experiments were conducted simultaneously in both MEBPR systems by using test membrane modules. From the transmembrane pressure (TMP) data of the test membrane modules, it was revealed that fouling propensities of the MEBPR mixed liquors were similar in both parallel reactors under the operating conditions applied, although the fouling propensity of the aerobic mixed liquors of both reactors increased when the SRT of the reactors was reduced. Routinely monitored reactor performance data suggest that an MEBPR process with a varying inflow (dynamic operating condition) performs similarly to an MEBPR process with steady operating conditions at SRTs of 10 days and 20 days. Mixed liquor characterization tests were conducted, including critical flux, capillary suction time (CST), time to filter (TTF) and, bound and soluble extracellular polymeric substances (EPS) were quantified, to evaluate their role on membrane fouling. The tests results suggest that the inflow variation in an MEBPR process did not make a significant difference in any of the measured parameters. With decreased SRT, an increase in the concentrations of EPS was observed, especially the bound protein, and the bound and soluble humic-like substances. This suggests that these components of activated sludge mixed liquors may be related to membrane fouling. No clear relationship was observed between membrane fouling and other measured parameters, including critical flux, normalized CST and normalized TTF.

No description available.

In the developing world, there are large populations suffering from infectious diseases, many of whom are located in remote regions. With the rapid growth in microfluidic systems in recent years, complex functions of conventional diagnostic equipment have been miniaturized and integrated into small devices at the size of a credit card (so-called portable Point-of-care (POC) devices). In this thesis a novel approach to overcoming the challenge of in-field biological sample processing and preparation to produce high quality fluids that can be readily used for downstream testings is described and proof of concept experiments presented. This approach uses hydrodynamic effects and combines nanoporous membrane with microfluidic systems and to filter the cellular component of blood. Experiments presented here demonstrate successful cells filtration from whole blood. Employing hydrodynamic effects is also shown to be an effective and potentially useful technique to isolate cells and plasma within appropriate micro-architectures.