A systematic study has been made of the factors which influence compressibility in cake filtration. A fully automated dead-end pressure filtration rig was designed, constructed and assembled at Loughborough and used to provide accurate data for an experimental matrix. The parameters investigated included pressure, feed concentration, time, surface charge, size and shape of the particulate material and scale of filtration. A proven electrical resistance measuring technique was used to determine transient solids concentrations through a filtering cake/suspension and subsequently interpret filtration performance. The particulate materials calcite and zinc sulphide dispersed in water were used to span a range of filter cake compressibility. The initial results from experiments using calcite were found to be reproducible and generally followed the expected trends. More compressible materials, such as zinc sulphide, were subsequently filtered at different pHs to investigate the influence of surface charge. Filter cells of different filter sizes were used to examine the influence of scale on filtration. Several curious observations were made such as sudden increases in filtrate rate at apparently stable process conditions and lower concentration measurements near the base of the cake. The importance of considering all scale-up parameters and their relation to each other is highlighted in the work. Further points such as the definition of compressibility over a narrow range of pressure and the structure of the filter cake have been discussed. The results were analysed with the use of conventional and new filtration theories. The conventional and modem theories generally gave good predictions of cake height for all the materials tested but for unstable/compressible suspensions the prediction of the concentration profile was less accurate. The use of the maximum solids concentration value at the base of the cake has been suggested to reduce this error and so help prevent filter under sizing. Results indicating retarded packing compressibility have been discussed along with volume-time data which suggest an influence of scale on filtration. Scale-up constants were found to vary considerably in some cases. Large changes in cake resistance were seen for small changes in cake concentration suggesting a need to use other structural characterising parameters as well as macroscopic cake concentration values. The Koenders and Wakeman model gave good predictions of the first linear part of the volume-time relationships for stable suspensions. Conclusions are drawn on the influence of each of the studied parameters on the filtration of compressible materials.

This thesis investigates the constant pressure cake filtration of interacting cellulose fibre/TiO2 (rutile) mixtures, and involved experimental studies using an automated pressure filtration apparatus. The influence of suspension composition, filtration pressure and solution environment on filtration has been discussed in relation to cake properties such as average cake porosity and specific resistance. To help interpret the filtration results, sedimentation data were also obtained. The average porosities of filter cakes formed from pure rutile and fibre suspensions in deionised water were approximately 0.6 and 0.75, respectively, and a steady and progressive increase in porosity with fibre fraction was generally observed. With filtrations at 450 kPa, the average specific cake resistances for pure fibre and rutile in deionised water were approximately 9.4x1013 and 4.2x1012 m kg-1 respectively, with the variation of specific resistance with solids composition showing a minimum. Similar trends were observed at other tested filtration pressures with suspensions in deionised water but not with filtrations of suspensions in 0.2 M NaCl and 0.1 M CaCl2 solutions. The minima in average specific cake resistance with solids composition for feeds in deionised water was attributed to rutile-fibre interactions. Abrupt transitions in cake structure were evident part way through some filtrations, and resulted in unexpected filtrate flow behaviour. This is an interesting phenomenon, and not only were the changes in cake structure relatively reproducible, but also the nature of the change could be altered by changes in filtration pressure, solids composition and/or solution environment. The study of fibre/particle binary filtration behaviour, in particular the porosity and specific cake resistance trends, were substantiated by relevant theoretical treatment and modelling analysis. With the porosity trends, an additive porosity concept seemed to represent the data better than interparticle penetration models. With the specific cake resistance trends, a semi-empirical equation was proposed which appeared to represent a wide range of binary mixture filtration data. A mathematical framework was also developed in an attempt to understand the underlying physical mechanisms which led to filter cake restructuring, and possible explanations were postulated.

<p>Cake filtration is a unit operation to separate solids from fluids in industrial processes. The build up of a filter cake is usually accompanied with a decrease in overall permeability over the filter leading to an increased pressure drop over the filter. For an incompressible filter cake that builds up on a homogeneous filter cloth, a linear pressure drop profile over time is expected for a constant fluid volume flow. However, experiments show curved pressure drop profiles, which are also attributed to inhomogeneities of the filter (filter medium and/or residual filter cake).</p><p>In this work, a mathematical filter model is developed to describe the relationship between time and overall permeability. The model considers a filter with an inhomogeneous permeability and accounts for fluid mechanics by a one-dimensional formulation of Darcy's law and for the cake build up by solid continuity. The model can be solved analytically in the time domain. The analytic solution allows for the unambiguous inversion of the model to determine the inhomogeneous permeability from the time resolved overall permeability, e.g. pressure drop measurements. An error estimation of the method is provided by rewriting the model as convolution transformation.</p><p>This method is applied to simulated and experimental pressure drop data of gas filters with textile filter cloths and various situations with non-uniform flow situations in practical problems are explored. A routine is developed to generate characteristic filter cycles from semi-continuous filter plant operation. The model is modified to investigate the impact of non-uniform dust concentrations.</p>

Cake filtration is a unit operation to separate solids from fluids in industrial processes. The build up of a filter cake is usually accompanied with a decrease in overall permeability over the filter leading to an increased pressure drop over the filter. For an incompressible filter cake that builds up on a homogeneous filter cloth, a linear pressure drop profile over time is expected for a constant fluid volume flow. However, experiments show curved pressure drop profiles, which are also attributed to inhomogeneities of the filter (filter medium and/or residual filter cake). In this work, a mathematical filter model is developed to describe the relationship between time and overall permeability. The model considers a filter with an inhomogeneous permeability and accounts for fluid mechanics by a one-dimensional formulation of Darcy's law and for the cake build up by solid continuity. The model can be solved analytically in the time domain. The analytic solution allows for the unambiguous inversion of the model to determine the inhomogeneous permeability from the time resolved overall permeability, e.g. pressure drop measurements. An error estimation of the method is provided by rewriting the model as convolution transformation. This method is applied to simulated and experimental pressure drop data of gas filters with textile filter cloths and various situations with non-uniform flow situations in practical problems are explored. A routine is developed to generate characteristic filter cycles from semi-continuous filter plant operation. The model is modified to investigate the impact of non-uniform dust concentrations.

Previous membrane researches undertaken over the years to develop general deadend filtration models made use of an approach that combined all three classical fouling mechanisms, namely, pore blocking, pore constriction and cake filtration. More recently researchers have modified and adapted this modelling approach for a cross flow side-stream membrane bioreactor (MBR) system. Literature also reveals that there have been numerous recent experimental studies conducted on rotating membrane bioreactor (RMBR) systems. Some of these studies have resulted in the creation of RMBR models of the membrane fouling process as well. However, simulation and modelling of the fouling in RMBRs is still a nascent topic to date due to poor understanding and great complexity of the system hydrodynamics involved. Even when models are developed, they are either too complex to be useful at operational level, or not comprehensive enough to express all possible operational scenarios. In many cases they are simply too difficult to calibrate and thus ending up being more suited as research tools rather than for direct process control. As such, further research is required in this area. The research reported in this thesis consists of the development and validation of a RMBR system fouling model that incorporates all three classical fouling mechanisms. This thesis work is divided into two main sections. On top of a literature review that thoroughly describes the background theory and general information on MBRs along with their state of the art, the first section of the thesis also explains the specific methodologies used to accomplish all the main tasks carried out in this research work. The first step of these methodologies involves the setting-up of a rotating MBR system process based upon the FUV-185-A15R Flexidisks membrane module that was developed by Avanti Membrane Technology (USA). This system was used to collect the majority of the data used in this thesis. Since some of these data outputs were compared against non-rotating MBR systems, a similar setting-up process for a bespoke static square MBR system was carried out as well. Using synthetic wastewater in conjunction with activated sludge, mixed liquor suspended solids in both MBR system bioreactors were increased in levels over time to desired levels (i.e. by periodic excess sludge wasting). Trans-membrane pressure (TMP)-stepping fouling data was then acquired from operations of these membrane ultrafiltration processes. This data was obtained by measuring the flux decline or TMP increase. Following data collection, a dynamic fouling model for this RMBR system was then created in Matlab (using the Genetic Algorithm function). To do this, hydrodynamic regimes such as air scouring and rotating shear effects along with all the three classical fouling mechanisms were included in the mathematical fouling model that was created from first principles. For the purpose of comparison, a similar fouling model was created without incorporating the rotational effects for the static square MBR system. This included modelling of the hydrodynamics as well. Finally, both these models were validated and calibrated using the data that were collected from both laboratory-based MBR systems. The second phase of the thesis explores the numerous outputted results produced via model simulations which were then discussed and analysed in great detail. Results from this research indicate that the mathematical models give a decent portrayal and description of the fouling mechanisms occurring within a rotating MBR system. It was found that the rotational mechanisms in terms of fouling prevention accounted for only twelve percent of cake removal with the rest being accomplished through the air scouring mechanism. However, it was found that although the slowly rotating spindle induced a weak crossflow shear, it was still able to even out cake build up across the membrane surface, thus reducing the likelihood of localised critical flux being exceeded, which would lead to dramatic loss of flux. Furthermore, when compared against the static MBR system, the study concluded that a rotating MBR system could increase the flux throughput by a significant amount. In conclusion, RMBR systems appear to represent alternative viable solutions when compared against the traditional static MBR systems that currently dominate the industrial and municipal marketplace. In future, RMBR systems may become the systems of first choice once there is a better understanding of the rotational processes, and once research and design into this sector broadens. Future study areas should thus focus on: whether the forces acting on an activated sludge particle during rotation have a significant effect on the fouling or the shear hydrodynamic regimes; whether activated sludge and benchmark models could be created for rotating MBRs whilst including the shear effects and hydrodynamic regimes; whether model predictive control using these developed RMBR models would enhance efficiency gains within an operational plant; and, whether the real measured soluble microbial products (SMP) concentrations could be used to create an even better SMP predictive model that accurately explains fouling behaviour.

Diese Arbeit stellt die nichtlineare Parameterschätzung als alternative Auswertemethode von Kuchenfiltrationsexperimenten vor. Anhand eines größeren Datensatzes werden die Vorteile dieser Methode gegenüber der verbreiteten Auswertung mittels einer linearisierten Form der Kuchenfiltrationsgleichung für den Fall konstanten Drucks gezeigt. Zur Bewertung der Anpassungsgüte werden Residuenplots erläutert und verwendet. Die Unterschiede der Ergebnisse bewegen sich im Bereich von 5 bis 15% bei der Bestimmung des spezifischen Kuchenfiltrationswiderstands, welcher der wichtigste Parameter bei der Auslegung von Filtrationsapparaten ist. Weitere Möglichkeiten der Auswertung werden aufgezeigt, die durch die nichtlineare Parameterschätzung möglich werden, darunter die Auswertung von Experimenten bei variablem Druck, die Bestimmung des Kuchenwiderstands kompressibler Feststoffsysteme sowie eine Bewertung der anfänglichen Verblockungsvorgänge am Filtermedium.:1 Introduction 2 Cake Filtration Theory 2.1 Historical Development 2.2 Derivation of the Cake Filtration Equation 2.3 Fit Procedures for Cake Filtration Data 2.4 Additional Methods for Finding the Time Offset 3 Materials and Methods 3.1 Materials 3.2 Filter Medium 3.3 Laboratory Pressure Filters 3.4 Example Dataset 3.5 Preparation of Example Dataset 3.6 Residual Plots and Chi-Squares 3.7 Bootstrapped Statistics 4 Proposed Fit Procedure 4.1 Nonlinear Regression 4.2 Region of Best Fit 5 Results and Discussion 5.1 Constant-Pressure Filtration 5.2 Hermans & Bredée Models 5.3 Residual Plots of Fit Results 5.4 Nonconstant Filtration 5.5 Compressibility Effects 5.6 Optimal Parameter Definition 5.7 The Role of the t/V-V-Diagram 6 Conclusions 7 Outlook 7.1 Constant-Flux Filtration 7.2 Inline Resistance Measurements 7.3 Parameter Estimation in Chemical Engineering A Appendix A.1 The Concentration Parameter A.2 Obsolete Fit Methods A.3 Residual Statistics A.4 Bootstrapped Statistics Data A.5 Fit Example in Microsoft Excel A.6 Experimental Data and Metadata B References / This thesis presents nonlinear parameter estimation as an alternative method for the evaluation of cake filtration experiments. A dataset of 225 constant-pressure filtration experiments is used to highlight the advantages of this method compared to the widely used evaluation method which uses a linear transformation of the cake filtration equation. The goodness-of-fit is tested through the means of residual plots, which are introduced and discussed. The difference in results for the two methods for the specific cake resistance parameter, which is the most important parameter in the dimensioning of filtration apparatused, lies between 5 and 15%. Further possibilities of evaluation are presented, which become possible through the use of nonlinear parameter estimation, such as: evaluation of filtration experiments with nonconstant pressure, the determination of cake resistances for compressible systems, and the investigation of the processes present in the beginning stages of cake filtration.:1 Introduction 2 Cake Filtration Theory 2.1 Historical Development 2.2 Derivation of the Cake Filtration Equation 2.3 Fit Procedures for Cake Filtration Data 2.4 Additional Methods for Finding the Time Offset 3 Materials and Methods 3.1 Materials 3.2 Filter Medium 3.3 Laboratory Pressure Filters 3.4 Example Dataset 3.5 Preparation of Example Dataset 3.6 Residual Plots and Chi-Squares 3.7 Bootstrapped Statistics 4 Proposed Fit Procedure 4.1 Nonlinear Regression 4.2 Region of Best Fit 5 Results and Discussion 5.1 Constant-Pressure Filtration 5.2 Hermans & Bredée Models 5.3 Residual Plots of Fit Results 5.4 Nonconstant Filtration 5.5 Compressibility Effects 5.6 Optimal Parameter Definition 5.7 The Role of the t/V-V-Diagram 6 Conclusions 7 Outlook 7.1 Constant-Flux Filtration 7.2 Inline Resistance Measurements 7.3 Parameter Estimation in Chemical Engineering A Appendix A.1 The Concentration Parameter A.2 Obsolete Fit Methods A.3 Residual Statistics A.4 Bootstrapped Statistics Data A.5 Fit Example in Microsoft Excel A.6 Experimental Data and Metadata B References

Gegenstand dieser Arbeit ist die Entwicklung und Untersuchung eines Aufbereitungsprozesses zur Gewinnung von Bitumen aus kanadischem Athabasca Ölsand, der im Tagebau gewonnen wurde. Es wird ein mechanisch-thermisches Verfahren zur Fest-Flüssig-Trennung eingesetzt. Dabei handelt es sich um vier Schritte: (1) Suspendierung des Ölsandes mit den organischen Lösungsmitteln, Toluol und n-Heptan, (2) Filterkuchenbildung, (3) Waschung des Filterkuchens mit Wechsel der Waschflüssigkeiten (gradierte Waschung) und (4) Dampfbeaufschlagung. Der Prozess stellt eine Alternative zur herkömmlichen Heißwasser-extraktion des Ölsandes dar. Die Nachteile der Heißwasserextraktion sind ökologische Probleme, ein hoher Energie- und Frischwasserbedarf. Die Ziele des Alternativprozesses sind die Minimierung des Wasser- und Energiebedarfs, Vermeidung schädlicher Abfallstoffe sowie die Maximierung der Bitumenausbeute. Als Produkte sollen feststofffreies Bitumen und rückstandsfreier, deponierbarer Feststoff gewonnen werden.

Made available in DSpace on 2014-12-17T14:08:40Z (GMT). No. of bitstreams: 1 VanessaLAG_DISSERT.pdf: 1481281 bytes, checksum: 8b61d326c9b0fb24441950affcfa1205 (MD5) Previous issue date: 2010-08-20 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Waterflooding is a technique largely applied in the oil industry. The injected water displaces oil to the producer wells and avoid reservoir pressure decline. However, suspended particles in the injected water may cause plugging of pore throats causing formation damage (permeability reduction) and injectivity decline during waterflooding. When injectivity decline occurs it is necessary to increase the injection pressure in order to maintain water flow injection. Therefore, a reliable prediction of injectivity decline is essential in waterflooding projects. In this dissertation, a simulator based on the traditional porous medium filtration model (including deep bed filtration and external filter cake formation) was developed and applied to predict injectivity decline in perforated wells (this prediction was made from history data). Experimental modeling and injectivity decline in open-hole wells is also discussed. The injectivity of modeling showed good agreement with field data, which can be used to support plan stimulation injection wells / A inje??o de ?gua ? uma t?cnica amplamente utilizada para deslocar o ?leo em dire??o aos po?os produtores e manter a press?o em reservat?rios de petr?leo. Entretanto, part?culas suspensas na ?gua injetada podem ser retidas no meio poroso, causando dano ? forma??o (redu??o de permeabilidade) e perda de injetividade. Quando ocorre essa redu??o de injetividade ? necess?rio aumentar a press?o de inje??o para manter a vaz?o de ?gua injetada. Desse modo, a correta previs?o da perda de injetividade ? essencial em projetos de inje??o de ?gua. Neste trabalho, um simulador, baseado no modelo tradicional da filtra??o em meios porosos (incluindo filtra??o profunda e forma??o do reboco externo), foi desenvolvido e aplicado para prever a perda de injetividade em po?os canhoneados (tal previs?o foi feita a partir de dados de hist?rico). Al?m disso, tamb?m foi discutida a determina??o experimental dos coeficientes do modelo e a perda de injetividade em po?os abertos. A modelagem da injetividade apresentou bom ajuste aos dados de campo, podendo ser utilizada para auxiliar no planejamento de estimula??es de po?os injetores

Made available in DSpace on 2014-12-17T14:08:53Z (GMT). No. of bitstreams: 1 AdrianoJAMB_DISSERT.pdf: 6352547 bytes, checksum: 4f7f1e181e2f04659c084a8901764e58 (MD5) Previous issue date: 2012-07-13 / Injectivity decline, which can be caused by particle retention, generally occurs during water injection or reinjection in oil fields. Several mechanisms, including straining, are responsible for particle retention and pore blocking causing formation damage and injectivity decline. Predicting formation damage and injectivity decline is essential in waterflooding projects. The Classic Model (CM), which incorporates filtration coefficients and formation damage functions, has been widely used to predict injectivity decline. However, various authors have reported significant discrepancies between Classical Model and experimental results, motivating the development of deep bed filtration models considering multiple particle retention mechanisms (Santos & Barros, 2010; SBM). In this dissertation, inverse problem solution was studied and a software for experimental data treatment was developed. Finally, experimental data were fitted using both the CM and SBM. The results showed that, depending on the formation damage function, the predictions for injectivity decline using CM and SBM models can be significantly different / A perda de injetividade, que pode ser causada pela reten??o de part?culas, ocorre geralmente durante a inje??o ou reinje??o de ?gua em campos de petr?leo. V?rios mecanismos, incluindo a exclus?o pelo tamanho (straining), s?o respons?veis pela reten??o de part?culas e bloqueio dos poros da forma??o, causando dano e o decl?nio da injetividade. A previs?o para o dano ? forma??o e a queda da injetividade ? essencial para o gerenciamento de projetos de inje??o de ?gua. O modelo cl?ssico (MC), que incorpora os coeficientes de filtra??o e de dano ? forma??o, tem sido amplamente utilizado na previs?o da perda de injetividade. Esse modelo apresenta bons resultados quando apenas um mecanismo de reten??o ? atuante. Entretanto, v?rios autores relataram discrep?ncias significativas entre o modelo cl?ssico e os dados experimentais, motivando o desenvolvimento de modelos que consideram m?ltiplos mecanismos de reten??o de part?culas, como o modelo de Santos e Barros (MSB, 2010). Neste trabalho, foi estudada a solu??o do problema inverso para diferentes modelos. A partir deste estudo, foi desenvolvido um software para o tratamento dos dados experimentais. Finalmente, os dados experimentais foram ajustados usando tanto o MC quanto o MSB. Os resultados demonstraram que, dependendo da fun??o dano ? forma??o utilizada, as previs?es dos modelos MC e MSB para a perda de injetividade podem ser significativamente diferentes

Reliable information about the micro-processes during filtration and dewatering of filter cakes allows more accurate statements about process development and design in any industrial application with solid-liquid separation units. Distributed particle properties such as shape, size, and material influence the formation of the porous network structure, which can show considerable local fluctuations in vertical and horizontal alignment in the cake forming apparatus. The present work relates to a wide range of particle sizes and particle shapes and presents their effects on integral, but preferably local, structural parameters of cake filtration. Current models for the relationship between particle properties and resulting porous structure remain inaccurate. Therefore, the central question focus on the model-based correlation between obtained tomographic 3D information and characteristic cake and process parameters. In combination with X-ray computed tomography and microscopy (ZEISS Xradia 510), data acquisition of the structural build-up of filter cakes is possible on a small scale (filter area 0.2 cm²) and a conventional laboratory scale (filter area 20 cm², VDI 2762 pressure nutsch). Thereby, the work focuses on structural parameters at the local level before, during, and after cake dewatering, such as porosity, coordination number, three-phase contact angle, characteristics of pores and isolated liquid regions, the liquid load of individual particles, tortuosity, and capillary length, and the corresponding spatial distributions. Seven different particle systems in the range of 20 and 500 µm, suspended in aqueous solutions with additives for contrast enhancement, served as raw materials for the filter cake formation. Image data processing from 16-bit greyscale images with a resolution of 2 to 4 µm/voxel edge length includes various operations with a two-stage segmentation to identify air, solid particles, and liquid phase, resulting in a machine learning-based automated approach. Subsequent modeling and correlation of measured parameters rely on experimentally verified quantities from mercury porosimetry, laser diffraction, dynamic image analysis, static and dynamic droplet contour analysis, as well as filtration and capillary pressure tests according to VDI guidelines. The tomography measurements provide microscopic information about the porous system, quantified using characteristic key parameters and distribution functions. By studying the cake structure concerning the local distribution of particle size and shape and the resulting porosity, segregation effects can be avoided by increasing the feed concentration of particles, whereby swarm inhibition of particles in the initial suspension strongly hinders or completely suppresses layer formation in the cake according to distributed particle properties (Publication A). In the subsequent dewatering of the filter cake to the irreducible saturation, the measurement of the local coordination number as well as the remaining liquid volumes at the particle contacts allows the determination of a discrete liquid load distribution by correlation with the respective particle volume (Publication B). The determination of the capillary length - shortest capillary for single-phase pore flow and capillary of least resistance for multiphase pore flow - provides modeling approaches for the cake formation from publication A as well as the dewatering process from publication B (Publication C). The parameter sets obtained also help to transfer and extend existing, theoretical models of multiphase pore flow to the application example of filter cake dewatering (Publication D). At the microscopic level, the measurement of the three-phase contact angle at isolated liquid volumes within the porous matrix provides a deeper understanding of the macroscopic models from publications C and D (Publication E).:List of Figures List of Tables Notation 1 Introduction 2 Multiphase Processes in Porous Media 2.1 Cake Filtration and Single Phase Porous Media Flow 2.2 Cake Dewatering 2.2.1 Particle Surface Wettability 2.2.2 Capillarity in Porous Media 2.2.3 Static Capillary Pressure 2.2.4 Dynamic Capillary Pressure 3 Acquisition of 3D Information of Porous Media 3.1 Absorption and Scattering of X-rays 3.2 X-ray Microscopy 3.2.1 Image Acquisition 3.2.2 Image Reconstruction 3.2.3 Image Quality and Artifacts 3.3 Image Post-Processing 3.3.1 Image Enhancement 3.3.2 Segmentation and Thresholding 3.3.3 Processing Binary Images 3.4 Image Measurement 4 Materials and Methods 4.1 The Solid Phase 4.2 The Liquid Phase 4.3 Suspension Stability 4.4 Experimental Design and Down-Scale for Tomography Measurements 4.5 Experimental Characterization of Filtration and Dewatering Properties 4.5.1 Cake Filtration 4.5.2 Cake Dewatering (Capillary Pressure Measurements) 5 Conclusion and Outlook Literature Publications A to E Appendix