Multiphase pumping with twin-screw pumps is a relatively new technology that has been proven successful in a variety of field applications. By using these pumps to add energy to the combined gas and liquid wellstream with minimal separation, operators have been able to reduce capital costs while increasing overall production. In many cases, such as subsea operations, multiphase pumping is the only viable option to make remote wells economic. Despite their many advantages, some problems have been encountered when operating under conditions with high gas volume fractions (GVF). Twin-screw multiphase pumps experience a severe decrease in efficiency when operating under wet-gas conditions, GVF over 95%. Field operations have revealed severe vibration and thermal issues which can lead to damage of the pump internals, requiring expensive maintenance. The research presented in this thesis seeks to investigate two novel methods of improving the performance of twin-screw pumps under wet-gas conditions. The first involves increasing the viscosity of the liquid stream. We propose that by increasing the viscosity of the liquid phase, the pump throughput can be increased. Tests were conducted at high GVF using guar gel to increase the viscosity of the liquid phase. Along with results from a multiphase pump model the pump behavior under wet-gas conditions with increased liquid viscosity was evaluated. The experimental results indicate that at high GVF, viscosity is not a dominant parameter for determining pump performance. Possible reasons for this behavior were proposed. These results were not predicted by current pump models. Therefore, several suggestions for improving the model’s predictive performance were suggested. The second method is the direct injection of liquid into the pump casing. By selectively injecting liquid into specific pump chambers, it is believed that many of the vibration issues can be eliminated with the added benefit of additional pressure boosting capacity. Since this method requires extensive mechanical modifications to an existing pump, it was studied only analytically. Calculations were carried out that show that through-casing liquid injection is feasible. More favorable pressure profiles and increased boosting ability were demonstrated.

Multiphase pumping with twin-screw pumps is a relatively new technology that has been proven successful in a variety of field applications. By using these pumps to add energy to the combined gas and liquid wellstream with minimal separation, operators have been able to reduce capital costs while increasing overall production. In many cases, such as subsea operations, multiphase pumping is the only viable option to make remote wells economic. Despite their many advantages, some problems have been encountered when operating under conditions with high gas volume fractions (GVF). Twin-screw multiphase pumps experience a severe decrease in efficiency when operating under wet-gas conditions, GVF over 95%. Field operations have revealed severe vibration and thermal issues which can lead to damage of the pump internals, requiring expensive maintenance. The research presented in this thesis seeks to investigate two novel methods of improving the performance of twin-screw pumps under wet-gas conditions. The first involves increasing the viscosity of the liquid stream. We propose that by increasing the viscosity of the liquid phase, the pump throughput can be increased. Tests were conducted at high GVF using guar gel to increase the viscosity of the liquid phase. Along with results from a multiphase pump model the pump behavior under wet-gas conditions with increased liquid viscosity was evaluated. The experimental results indicate that at high GVF, viscosity is not a dominant parameter for determining pump performance. Possible reasons for this behavior were proposed. These results were not predicted by current pump models. Therefore, several suggestions for improving the model’s predictive performance were suggested. The second method is the direct injection of liquid into the pump casing. By selectively injecting liquid into specific pump chambers, it is believed that many of the vibration issues can be eliminated with the added benefit of additional pressure boosting capacity. Since this method requires extensive mechanical modifications to an existing pump, it was studied only analytically. Calculations were carried out that show that through-casing liquid injection is feasible. More favorable pressure profiles and increased boosting ability were demonstrated.

The use of twin-screw pumps for moving fluids is not new technology but its application to wet gas compression (high gas volume fraction [GVF]) is still considered relatively new. There are many advantages for using twin-screw pumps for oil field applications; three of the immediate improvements include reducing hardware costs, reducing well bore pressure, and producing a pressure boost to move the product to a central collection facility. While there are many advantages to using twin-screw pumps in wet gas applications, there are some problems that have been encountered while operating at high GVFs. When operating at high GVF, over 95 percent twin-screw pumps experience a severe loss of efficiency and an increase of operating temperature. A common way to increase the efficiency while operating in the high GVF range includes adding a liquid recirculation system where a portion of liquid is stored downstream of the pump and is injected into the pump inlet. These systems lower the effective GVF of the multiphase fluid below 95 percent in order to increase the pump efficiency. The first objective is to characterize the performance of a twin-screw pump fitted with a liquid recirculation system while operating under high GVF conditions. The second objective is to investigate the transient heat rise associated with high GVF operation. While traditional twin-screw pumps can be fitted with a liquid recirculation system to allow them to operate under high GVF conditions the pumps themselves are not optimized for wet gas compression and still suffer performance penalties. The results of this investigation show that the liquid recirculation system can allow the pump to operate under high GVF but the heat added to the system reduces the systems efficiency. Without a method of removing the heat generated in the pumping process the pump will not run at its optimal efficiency. The following investigation provides recommendations for further research in area of multiphase pumping using twin-screw pumps based on the characterization and transient studies provided in this thesis.

Yes / Twin screw granulation (TSG) has been applied to wet granulation, although its application in melt granulation has been more limited. This work explores potential advantages of hot melt granulation using twin screw extrusion. Four main operating and formulation parameters were investigated: screw speed, number of mixing elements, temperature, and binder percentage. Combinations of these factors were then studied to determine their impact on the quantity and characteristics of granules within the desired size range of 125 - 1000 µm. A screening design of experiments (DOE) study was used with each factor set at three levels, to investigate individual factor effects and interactions. Two types of mixing elements were studied: kneading block (KB) and chaotic elements. The type and number of mixing elements were found to be paramount in contributing to the quantity and characteristics of granules formed. Results obtained agreed with previous findings in literature on the influence of different screw elements on the characteristics of granules formed by twin screw granulation. Additionally, the study revealed the unique impact which different mixer elements have on both granule production and characteristics. Depending on the specific need or use of granules in required applications, the granulation process can be effectively designed to meet the end product quality and outcome.

Solvent-free extrusion emulsification (SFEE) is new top-down technique specially suited to high viscosity polymers (100-1000 Pa.s) for producing sub-micron (100-500 nm) particles inside a twin screw extruder (TSE) without the use of hazardous solvents. SFEE has been difficult to implement in industry due to process sensitivities and a lack of mechanistic knowledge on how the polymer-water morphology must develop prior to inversion. To devise a mechanistic explanation of the critical stages of the process, an inline orifice-plate type viscometer was developed to monitor rheological changes previously witnessed in early batch studies. The general variables of study throughout the thesis included the manner by which sodium hydroxide (NaOH) can be added as well as the NaOH content necessary, resin-to-water (R/W) ratio, and surfactant content. The last study in the thesis explores the influence of matrix viscosity, which was accomplished by crosslinking the polyester. The striated lamellae morphology of the polyester-water system, critically controlling the final particle size, depended on two factors, specifically surface energy (determined by endgroup conversion and added surfactant) and matrix viscosity. Analysis of the rheological response indicated that a higher polar surface energy contribution had the greatest influence on the morphological state, demonstrating a steeper viscosity transition due to more favourable and more rapid incorporation of water within the polyester matrix. A strong correlation was repeatedly found between particle size and this viscosity transition, which has been related to the thickness of striated lamellae through a theory of lamellae coarsening (or thinning as is more relevant to the current process). The reported lamellae coarsening model in the literature, which shows the predominant effects of interfacial energy and viscosity on lamellae thickness in a mixed phase system showed excellent correspondence to the results in this thesis. Among the variables of study in this thesis, the dissolution of the sodium hydroxide species (when added as a solid particle) and the kinetics of end-groups conversion proved to be rate-limiting phenomena to generating thinner striated lamellae. The ionic strength of the system was notably important to the viscosity change occurring in the process as water was added for the first time and subsequently influenced the particle size produced, particularly when additional surfactant was not added and the system relied exclusively on the carboxylate endgroups present. Finally, with mounting evidence that SFEE showed significant sensitivity to the matrix viscosity, a final study examined the effectiveness of SFEE in the face of ever increasing viscous force by blending a crosslinked polyester into the neat resin at different weight fractions. With higher viscosity there was a corresponding decrease in interfacial area growth between the polyester and water, resulting in increased particle size but even with a viscosity near 800 Pa.s, far above a traditional oil-in-water system, it was still found possible in this study to create nano-sized particles by SFEE. / Thesis / Doctor of Philosophy (PhD)

This thesis covers a systematic examination of wet granulation in a twin screw extruder. Granulation of the excipient, (alpha)-lactose monohydrate, was done with the aid of PVP in an aqueous solution which acted as a binding agent. The influences on agglomeration by the following processing parameters were studied: screw elements design, screw rotational speed, binding solution concentration, and binder addition method. Qualitative efforts had also been made in modeling the process to gain valuable insight into how the elements affected agglomeration and granule rupture. A commercial software package PFC^2D, based on the Discrete Element Method (DEM), was used to simulate the dynamic behavior of the screw elements in the barrel. Within the optimal range of 7.5 -10wt% binder concentration, all the screw profiles were studied for their capacity to produce desirable granules suited to solid oral dosage form production. By increasing the rotational speed from 30 RPM to 80 RPM, the granules size of the conveying, discharging and chopping elements decreased whereas this operating parameter had little effect on granule size within kneading blocks. The nominal particle size produced by a screw element increased from 300(mu)m to 1mm when dispersive mixing was its dominant purpose (i.e. the kneading block), thereby meeting our criteria for a suitable granule in tab letting. Similar size development of the granules was not found with the other conveying or distributive mixing elements. In regards to particle shape, the kneading blocks produced elongated shape granules while other elements tested in this study produced smaller, more spherical agglomerates. Either shape was found effective in tabletting. Wet granulation was not feasible with more extreme concentrations of the aqueous binder (i.e. 5 wt% or 12 wt%) in this project, and the hand pre-blend method was the only approach found suitable for metering this additive into the system while maintaining steady feeding rates and output. / Thesis / Master of Applied Science (MASc)

In this work, the peroxide-initiated degradation of polypropylene (PP) in co-rotating intermeshing twin-screw extruders (COITSEs) is analyzed by means of numerical simulations. This reactive extrusion (REX) operation is simulated by implementing (i) a one-dimensional and (ii) a three-dimensional (3D) modeling approach. In the case of the 1D modeling, a REX mathematical model previously developed and implemented as a computer code is used for the evaluation of two scale-up rules for COITSEs of various sizes. The first scale-up rule which is proposed in this work is based on the concept of thermal time introduced by Nauman (1977), and the second one is based on specific energy consumption (SEC) requirements. The processing parameters used in testing the previously referred to scale-up approaches are the mass throughput, the screw rotating speed, and the peroxide concentration, whereas the extruder screw configuration and the barrel temperature profiles are kept constant. The results for the simulated operating conditions show that when the REX operation is scaled-up under constant thermal time, very good agreement is obtained between the weight-average molecular weight (Mw) and poly-dispersity index (PDI) from the larger extruders and the values of these parameters corresponding to the reference extruder. For the constant SEC approach, on the other hand, more significant variations are observed for both of the aforementioned parameters. In the case of the implemented constant thermal time procedure, a further analysis of the effect of the mass throughput and screw speed of the reference device on the scaled-up operation is performed. It is observed that when the lower mass throughput is implemented for the smaller extruder keeping a constant screw speed, the predicted residence times of extrusion for the larger extruders are lower, in general terms, than those corresponding to the reference device, and a converse situation occurs for the higher implemented value of the mass throughput. Also, in general terms, the higher increase of the reaction temperature on the scaled-up operation corresponds to the lower mass throughputs and higher screw speeds specified for the reference extruder. For the 3D modeling approach, two different case studies are analyzed by means of a commercial FEM software package. The REX simulations are performed under the assumption of steady-state conditions using the concept of a moving relative system (MRS). To complement the information obtained from the MRS calculations, simulations for selected conditions (for non-reactive cases) are performed considering the more realistic transient-state (TS) flow conditions. The TS flow conditions are associated to the time periodicity of the flow field inside the conveying elements of COITSEs. In the first case study, the peroxide-initiated degradation of PP is simulated in fully-filled screw elements of two different size COITSEs in order to evaluate scale-up implications of the REX operation. In the second case, the reacting flow is simulated for a conventional conveying screw element and a conveying screw element having a special design and corresponding to the same extruder size. For both of the analyzed cases, the effects of the initial peroxide concentration and mass throughput on the final Mw and PDI of the degraded resin are studied. The effect of the processing conditions is discussed in terms of the residence time distribution (RTD), the temperature of reaction, and the distributive mixing capabilities of the REX system. When analyzing the scale-up case, it is found that for the implemented processing conditions, the final Mws and PDIs are very close to each other in both of the analyzed flow geometries when the specified flow is close to that corresponding to the maximum conveying capabilities of the screw elements. For more restrictive flow conditions, the final Mws and PDIs are lower in the case of the screw element of the larger extruder. It is found that the distributive mixing ability of the reactive flow is mainly related to the specified mass throughput and almost independent of the specified peroxide concentration for a particular extruder size. For the analyzed screw elements, the conveying element corresponding to the small size extruder shows a slightly better distributive mixing performance. For this same case study, a further evaluation of the proposed scale-up criterion under constant thermal time confirms the trend of the results observed for the 1D simulations. In the second case study, the special type of screw element consists of screws rotating at different speeds which have different cross sections. In this case, the outer and inner diameters of both the special and the conventional type of screw elements are specified to be the same. As in the previous case study, the distributive mixing capabilities appear to be independent of the specified peroxide concentrations but dependent on the mass flow rate. It is speculated from the simulation results, from both the transient- as well as the steady-state flow conditions, that the screw element with the special design would yield lower final values of the PDI and Mw. Also, this screw element appears to have improved distributive mixing capabilities as well as a wider RTD.

In this work, the peroxide-initiated degradation of polypropylene (PP) in co-rotating intermeshing twin-screw extruders (COITSEs) is analyzed by means of numerical simulations. This reactive extrusion (REX) operation is simulated by implementing (i) a one-dimensional and (ii) a three-dimensional (3D) modeling approach. In the case of the 1D modeling, a REX mathematical model previously developed and implemented as a computer code is used for the evaluation of two scale-up rules for COITSEs of various sizes. The first scale-up rule which is proposed in this work is based on the concept of thermal time introduced by Nauman (1977), and the second one is based on specific energy consumption (SEC) requirements. The processing parameters used in testing the previously referred to scale-up approaches are the mass throughput, the screw rotating speed, and the peroxide concentration, whereas the extruder screw configuration and the barrel temperature profiles are kept constant. The results for the simulated operating conditions show that when the REX operation is scaled-up under constant thermal time, very good agreement is obtained between the weight-average molecular weight (Mw) and poly-dispersity index (PDI) from the larger extruders and the values of these parameters corresponding to the reference extruder. For the constant SEC approach, on the other hand, more significant variations are observed for both of the aforementioned parameters. In the case of the implemented constant thermal time procedure, a further analysis of the effect of the mass throughput and screw speed of the reference device on the scaled-up operation is performed. It is observed that when the lower mass throughput is implemented for the smaller extruder keeping a constant screw speed, the predicted residence times of extrusion for the larger extruders are lower, in general terms, than those corresponding to the reference device, and a converse situation occurs for the higher implemented value of the mass throughput. Also, in general terms, the higher increase of the reaction temperature on the scaled-up operation corresponds to the lower mass throughputs and higher screw speeds specified for the reference extruder. For the 3D modeling approach, two different case studies are analyzed by means of a commercial FEM software package. The REX simulations are performed under the assumption of steady-state conditions using the concept of a moving relative system (MRS). To complement the information obtained from the MRS calculations, simulations for selected conditions (for non-reactive cases) are performed considering the more realistic transient-state (TS) flow conditions. The TS flow conditions are associated to the time periodicity of the flow field inside the conveying elements of COITSEs. In the first case study, the peroxide-initiated degradation of PP is simulated in fully-filled screw elements of two different size COITSEs in order to evaluate scale-up implications of the REX operation. In the second case, the reacting flow is simulated for a conventional conveying screw element and a conveying screw element having a special design and corresponding to the same extruder size. For both of the analyzed cases, the effects of the initial peroxide concentration and mass throughput on the final Mw and PDI of the degraded resin are studied. The effect of the processing conditions is discussed in terms of the residence time distribution (RTD), the temperature of reaction, and the distributive mixing capabilities of the REX system. When analyzing the scale-up case, it is found that for the implemented processing conditions, the final Mws and PDIs are very close to each other in both of the analyzed flow geometries when the specified flow is close to that corresponding to the maximum conveying capabilities of the screw elements. For more restrictive flow conditions, the final Mws and PDIs are lower in the case of the screw element of the larger extruder. It is found that the distributive mixing ability of the reactive flow is mainly related to the specified mass throughput and almost independent of the specified peroxide concentration for a particular extruder size. For the analyzed screw elements, the conveying element corresponding to the small size extruder shows a slightly better distributive mixing performance. For this same case study, a further evaluation of the proposed scale-up criterion under constant thermal time confirms the trend of the results observed for the 1D simulations. In the second case study, the special type of screw element consists of screws rotating at different speeds which have different cross sections. In this case, the outer and inner diameters of both the special and the conventional type of screw elements are specified to be the same. As in the previous case study, the distributive mixing capabilities appear to be independent of the specified peroxide concentrations but dependent on the mass flow rate. It is speculated from the simulation results, from both the transient- as well as the steady-state flow conditions, that the screw element with the special design would yield lower final values of the PDI and Mw. Also, this screw element appears to have improved distributive mixing capabilities as well as a wider RTD.

No description available.

La luzerne est une plante fourragère, de la famille des Fabacées, largement cultivée en France du fait de sa richesse en protéines. Industriellement, cette plante est pressée, puis séchée sur tambour rotatif. L’étape de pressage conduit à l’obtention de grandes quantités de jus, lui aussi riche en protéines. L’objectif de cette thèse a été de développer un procédé de bioraffinerie de la luzerne, applicable aux autres plantes fourragères, permettant la valorisation des toutes les fractions de la plante. La première étape consiste en un fractionnement thermo-mécanique de la luzerne entière par extrusion bi-vis. Deux fractions sont obtenues : un résidu fibreux solide en partie déshydraté, pouvant être utilisé dans la filière agro-matériaux, et un filtrat vert, riche en protéines. L’extrusion bi-vis est une alternative intéressante aux procédés classiques de déshydratation, car l’étude de l’optimisation des paramètres d’extrusion a permis de montrer qu’il est possible de récupérer la grande majorité des protéines de la plante dans le filtrat. Ce filtrat subit par la suite une séparation liquide/solide par centrifugation, permettant la récupération d’un culot vert, dont on peut extraire la chlorophylle. Le jus clarifié est ultrafiltré, puis traité par chromatographie hydrophobe, avec l’huile de tournesol comme solvant extracteur, de manière à séparer différentes protéines. L’étude plus fondamentale de la fixation des protéines sur résine a permis de modéliser le fractionnement des protéines par interactions hydrophobes. / Alfalfa is a common Legume, cultivated as a forage crop, thanks to its high protein content. In the green crop industry, alfalfa is pressed and dried on a rotative cylinder. The pressing step leads to the production of large amounts of green juice, rich in proteins. The aim of this work was to develop a biorefinery process for alfalfa, which could be adapted to other green crops, allowing the valorization of each fraction. The first step is the whole plant thermo-mechanical fractionation in the twin-screw extruder. Two fractions are obtained: a solid fibrous residue, partly dehydrated which could be valorized as an agro-material, and a green filtrate, rich in proteins. Twin-screw extrusion is an interesting alternative to usual industrial dehydration processes. Indeed, the study of the extruder parameters optimization showed that most of the alfalfa proteins can be recovered in the filtrate. This green extract is then centrifuged, in order to separate the solid particles. Chlorophyll can be extracted from the centrifugation pellet. The clarified juice is treated by ultrafiltration, and lastly fractionated thanks to hydrophobic chromatography, with sunflower oil as the solvent, in order to separate the proteins. The more fundamental study of proteins fixation on resins allowed us to modelize proteins fractionation using hydrophobic interactions.