Dissertations / Theses on the topic 'Fibre flocculation'

<p>At the division of Paper Technology a forming unitconsisting of headbox, forming roll unit and reservoir systemfor suspension recirculation has been constructed, with themain purpose to experimentally study the paper forming event byvisually following the fibre flow phenomena in the formingzone.</p><p>The effect of various running parameters upon the pressuredistribution, which is in correlation to the flow phenomenaoccuring during forming, has been studied with a flush mountedpressure sensor. Some combinations of running parametersresulted in highly oscillating pressure pulses, which wereevaluated by their wavelength.</p><p>The visualisation was made with a high-speed video cameraand a pulsed laser light source. The forming zone was observedvia a mirror mounted on the forming roll, thus following aspecific small area of the forming zone. This made it possibleto follow floc motions relative to the forming roll/wire. Theflocs were found to move towards the wire due to the dewateringflow wereupon the bottom part of the floc was pinned to thewire. If the suspensionspeed is different from the wire speedthe floc will be stretched out, because the upper part of thefloc has a slightly different speed in comparison to the bottompart. If this speed difference is high enough, the flocs maysplit and thus contribute to fragmentation.</p><p>The floc-floc interaction has been studied in a Couetteapparatus. It has been observed that voids in the suspensionplay a central role for the floc break-up process. The reasonis belived to be that voids induce movement inside thesuspension, which is a prerequisite for floc break-up. Thefloc-floc relative movements have been found to obey simplelaws of rack-and-pinion principles.</p>

<p>A flow loop system for study of fibre flocculation insuspensions has been developed. The system is designed tosimulate the flow conditions in a paper machine headbox. It isequipped with a radial distributor feeding a step diffuser pipepackage, after which the flow is contracted in a 2-D nozzle.The flow system is also equipped with a secondary flowcontraction with an area reduction ratio of 2:1 after theheadbox nozzle, mimicking accelerations that may take placeduring forming. The flow system is equipped with heating andcooling devices for the study of temperature effects on fibresuspension flocculation. An online dosage device for the studyof chemical effects on fibre suspension flocculation is alsoincluded. The maximum flow velocity in the system is 16m/s.</p><p>Flowing fibre suspensions were studied using a high speedCCD video camera and transmitted infra-red laser light pulseillumination. Images were taken either separately before andafter or along the secondary contraction. Images of fibreflocculation were evaluated by power spectrum analysis, and themean floc size and the flocculation index were calculated. Aconcept of mean floc area reduction, based on power spectrum,has been introduced to characterise the fibre network insuspensions. By comparingthe fibre flocculation before andafter the secondary contraction, or by following the fibreflocs along the secondary contraction, floc rheologyinformation can be obtained. The effects of chemical additivesand fibre surface modification can also be studied by comparingthe corresponding fibre flocculation.</p><p>For a bleached softwood kraft pulp suspension at a fibreconcentration of 5 g/l, the fibre flocs along the secondarycontraction have been manually evaluated, and the resultsconfirm that the power spectrum analysis is applicable. Ca 1/5of the flocs were broken into two by the contraction. The meanfloc size increases in MD while in CD it decreases during theflow contraction. Both the floc aspect ratio and the flocorientation in MD increase during the flow contraction. The netfibre floc area is decreased and the fibre flocs areconcentrated by the flow contraction, which is confirmed by anincrease of gray value of the flocs in the light transmissionimages. The dewatering of fibre flocs may thus have alreadybeen started in the suspension before reaching the wires in theforming zone.</p><p>Some physical influences on fibre suspension flocculationhave been investigated. The results confirm that fibreconcentration and fibre length are the dominating factorsaffecting fibre suspension flocculation. Increasing absoluteflow velocity has an insignificant effect on fibre flocs in theflow contraction. Suppressing turbulence, by increasingsuspension viscosity via a decrease of medium temperature,shows a clear effect on reducing fibre suspensionflocculation.</p><p>Some chemical influences on fibre suspension flocculationhave also been investigated. A retention aid, flocculant,cationic polyacrylamide, C-PAM, increases fibre suspensionflocculation by a bridging mechanism, and a formation aid,class II, anionic polyacrylamide, A-PAM, decreases fibresuspension flocculation by suppressing turbulence. Fibresuspension flocculation can also be reduced by surfacemodification with carboxymethyl cellulose, due to a reductionof the friction between fibres. The amount of fibre dispersiondepends on the ionic form of the grafted CMC, due to theelectrostatic repulsion between negatively charged groups onthe grafted CMC moieties. Xyloglucan, a non-ionic polymer,which is strongly adsorbed on cellulosic fibre surfaces, showsa similar influence on reduction of fibre suspensionflocculation by decreasing the friction between fibres.</p><p>The fibre flocculation data in the flow loop system werealso compared with the corresponding paper formation data inthe sheets produced on a pilot paper machine, both with andwithout chemical additives. The results show that the fibresuspension flocculation is well correlated with the paper sheetformation: when the fibre suspension flocculation is increased,the corresponding paper sheet formation deteriorates,especially in the large scale range.</p>

<p>The adsorption of cationic polyacrylamide (C-PAM) and silicananoparticles onto a model surface of silicon oxide wascompared with the adsorption of C-PAM to fibres and theirinfluence on flocculation of a fibre suspension. An increase inionic strength affects the polyelectrolyte adsorption indifferent ways for these two systems. With the silica surface,an increase in the ionic strength leads to a continuousincrease in the adsorption. However, on a cellulose fibre, theadsorption increases at low ionic strength (1 to 10 mM NaCl)and then decreases at higher ionic strength (10 to 100 mMNaCl). It was shown that the adsorption of nanoparticles ontopolyelectrolyte-covered surfaces has a great effect on both theadsorbed amount and the thickness of the adsorbed layer. Theresults showed that electrostatic interactions were thedominating force for the interaction between both the fibresand the polyelectrolytes, and between the polyelectrolytes andthe silica particles. Furthermore, at higher NaClconcentrations, a significant non-ionic interaction between thesilicon oxide surface/particles and the C-PAM was observed.</p><p>The adsorption rate of C-PAM onto fibres was rapid andquantitative adsorption was detected in the time range between1 and 8 s at polyelectrolyte addition levels below 0.4 mg/g.Conversely, an increase in the amount of added polymer leads toan increased polymer adsorption up to a quasi-static saturationlevel. However, after a few seconds this quasi-staticsaturation level was significantly lower than the level reachedat electrostatic“equilibrium”. The adsorbed amountof charges at full surface coverage after 1 to 8 s contact timecorresponded to only 2 % of the total fibre charge, whereasafter 30 minutes it corresponded to 15 % of the total fibrecharge. This shows that a full surface coverage at shortcontact times is not controlled by surface charge. Based onthese results, it is suggested that a combination of anon-equilibrium charge barrier against adsorption and ageometric restriction can explain the difference between theadsorption during 1 to 8 s and the adsorption after 30 minutes.With increasing time, the cationic groups are neutralised bythe charges on the fibre as the polyelectrolyte reconforms to aflat conformation on the surface.</p><p>The addition of a high concentration of C-PAM to a fibresuspension resulted in dispersion rather than flocculation.This behaviour is most likely due to an electrostericstabilisation of the fibres when the polyelectrolyte isadsorbed. Flocculation of the fibre suspension occurred at lowadditions of C-PAM. A maximum in flocculation was found ataround 50 % surface coverage and dispersion occurred above 100% surface coverage. It was also shown that for a given level ofadsorbed polymer, a difference in adsorption time between 1 and2 seconds influenced the flocculation behaviour. An optimum inflocculation at 50 % surface coverage in combination with theimportance of polymer reconformation time at these shortcontact times showed that the C-PAM induced fibre flocculationagrees with La Mer and Healy’s description of bridgingflocculation.</p><p>A greater degree of flocculation was observed with theaddition of silica nanoparticles to the fibre suspension thanin the single polyelectrolyte system. Flocculation increased asa function of the concentration of added nanoparticles until0.5 mg/g. At higher additions the flocculation decreased againand this behaviour is in agreement with an extended model formicroparticle-induced flocculation. An increase in flocculationwas especially pronounced for the more extended silica-2particles. This effect is attributed to the more extendedpolyelectrolyte layer, since the adsorbed amount wasessentially the same for both silica particles.</p><p>Finally it was found that fines from the wood fibres had asignificant effect on the flocculation. When fines were added,a greater degree of flocculation was detected. Furthermore, itwas also more difficult to redisperse the fibres with polymerin the presence of fines.</p><p><b>Keywords:</b>Adsorption, bridging, cationic polymers,cellulose fibres, electrosteric stabilisation flocculation,ionic strength, nanoparticle, polyelectrolyte, reconformation,retention aids and silica</p>

This study presents quantitative results on the effect on individual fiber length during fiber flocculation. Flocculation was induced by a cationic polyacrylamide (cPAM). A high speed camera recorded 25 second video clips. The videos were image-analyzed and the fiber length and the amount of fiber in each sample were measured. Prior to the flocculation process, fibers were fractionated into short and long fibers. Trials were conducted using the unfractionated fiber, short fiber, and long fiber. The short and long fibers were mixed in several trials to study the effect of fiber length. The concentration of cPAM was varied as well as the motor speed of the impeller (RPM). It was found that the average fiber length decreased more rapidly with increasing motor speed. Increasing the concentration of cPAM also led to a greater decrease in average fiber length. A key finding was that a plateau was reached where further increasing the amount of cPAM had no effect. Hence, fibers below a critical length resisted flocculation even if the chemical dose or shear was increased. This critical length was related to the initial length of the fiber.

The retention of process colloids in the paper web is essential for papermaking process efficiency and product quality. Fines (fibre fragments) and fillers strongly affect the optical, surface and mechanical properties of paper. A very efficient flocculation aid system to deposit fine material (colloids) on fibres (collectors) consists of a polymer used in conjunction with anionic microparticles. The objective of this thesis is to elucidate the mechanism of fines retention with poly(electrolyte)-montmorillonite flocculant systems. Two main subjects are addressed. Firstly, polymer transfer between colloidal particles and collectors was characterised and modelled, and the influence on the papermaking process was evaluated. Secondly, the role of anionic microparticles in a dual flocculation aid was investigated. The influence on the flocculation kinetics and the adsorption behaviour of dissolved and colloidal compounds were studied.<br>The hetero-flocculation of wood fibres and fines induced by polymer and microparticles was analysed in a stirred tank reactor. The deposition of fines on fibres in the presence of polymer is transient. This is attributed to polymer transfer between surfaces upon particle detachment, which leads to the formation of an electro-steric barrier. The resulting polymer layers have limited bridging abilities. A mathematical model describing the simultaneous particle deposition and polymer transfer was developed and validated. The kinetics is determined by three rate constants: a deposition rate constant (k1), a detachment rate constant (k2) and a polymer transfer coefficient (beta). The influence of shear, salt concentration and polymer chemistry on the kinetics was quantified.<br>Microparticles act as bridging agents between adsorbed polymer layers. They provide a stronger bond than single polymer layers. Bond strengthening occurs irrespective of the bridging ability of the adsorbed layers towards cellulosic surfaces. The mechanism is explained in terms of charge densities and polymer layer conformations. The de-layering of montmorillonite is crucial for its efficiency.<br>Finally, the efficiency of montmorillonites as white water scavengers was quantified using model wood colloids and polymers. Dissolved and colloidal substances adsorb on montmorillonites following a low-affinity Langmuir isotherm. Dissolved polymers form molecular monolayers, while colloids adsorb as particles. Montmorillonite was found an efficient scavenger for colloidal material.<br>Montmorillonite used in conjunction with a poly(electrolyte) has three effects in improving fines retention. It augments the bond strength as a bridging agent between adsorbed polymer layers, it allows the retention of colloids coated with inactive polymer layers and finally it scavenges the dissolved and colloidal substances, which would otherwise decrease the poly(electrolyte) efficiency.

Kyoto University (京都大学)<br>0048<br>新制・課程博士<br>博士(農学)<br>甲第10879号<br>農博第1385号<br>新制||農||887(附属図書館)<br>学位論文||H16||N3890(農学部図書室)<br>UT51-2004-G726<br>京都大学大学院農学研究科森林科学専攻<br>(主査)教授 松本 孝芳, 教授 藤田 稔, 教授 西尾 嘉之<br>学位規則第4条第1項該当

The area of the digital image processing is getting more attention in the hope that it will increase the accuracy of any scientific measurements, such as in determining an object velocity, temperature, and size. While human vision is excellent to recognize and differentiate objects, it has been proven to be a poor tool when it comes to measure the object performance. One of many digital image processing applications is texture analysis whose purpose is to evaluate image patterns. The purpose of this dissertation is to investigate the use of texture analysis as a tool to micro fiber dispersion measurement. Micro fiber dispersion can be found in many applications such as in paper and industry powder engineering. Three cases related to micro fiber dispersion were investigated in this study. The first case was the experimental study of the dispersion in open water channel. Sets of synthetic fibers were put into water channel to simulate a process that can be found in papermaking industry. The research investigated the effect of three operating parameters: fluid velocity, fiber consistency, and fiber aspect ratio to fiber dispersion. Using two-factorial experimental design technique, the main and interaction effects of these parameters were evaluated. The study found that increasing fluid velocity, fiber aspect ratio, and consistency decreased the dispersion level. The study also found that the effect of individual parameters is more pronounced than the role of the interactive terms on the fiber flocculation. The second case considered was applying the fiber dispersion analysis to computer-synthesized images consisting of different arrangements of fibers. Four sets of sub-cases were presented. These sub-cases were divided based on the fiber-concentrated location and fiber distribution. The use of computer-synthesized images was found to be very useful to simulate real situation during fiber dispersion. The third case investigated the fiber distribution on a dry paper. Images for different types of paper were taken and evaluated to see the dispersion level of each type of paper. It was found that the current texture analysis was applicable to determine the dispersion level for dry papers. While three cases indicated that the texture analysis can be used to investigate the fiber dispersion, the texture analysis used here is not a perfect and universal method and may not be suitable to analyze other types of dispersions. The human vision will always be essential to determine if the texture analysis is applicable to any other problem.

Formation plays an important role in the end-use properties of paper products, but before formation can be optimized to achieve superior properties, an understanding about the causes of formation must be developed. Formation is caused by variations in the basis weight of paper that are results of fiber floc formation before and during the forming of the sheet. This project is a first step in a larger research program aimed at studying formation. By observing the effects that mechanical energy dissipation (in the form of turbulence) and retention chemical dosage have on floc formation, we may develop a better understanding of how to control formation. In this study, a rectangular cross-section flow channel was constructed to aid in the acquisition of digital images of a flowing fiber suspension. The furnish consisted of a 55:45 spruce:pine bleached market pulp mix from a Western Canadian mill. Turbulence was varied by changing the flow rate; Reynolds numbers achieved range from 20,000 to 40,000. The retention aid used was a cationic polyacrylamide with a medium charge density. Dosage of the retention aid was varied from 0 to 2 pounds per ton OD fiber. Digital images of the flowing fiber suspension were acquired with a professional digital SLR camera with a forensics-quality lens. Three separate image analysis techniques were used to measure the flocculation state of the fiber suspension: morphological image operations, formation number analysis, and fast Fourier transform analysis. Morphological image analysis was capable of measuring floc size increases seen in the acquired floc images. It was shown how floc diameter could increase simultaneously with decreasing total floc area and total floc number. A regression model relating retention aid dosage and energy dissipation was constructed in an effort to predict flocculation. The regression model was used to predict F2 (formation number squared) results from the study. The interaction effect RE was shown to have a differing effect across the retention aid dosage levels. As a result, this model and technique may prove to be a beneficial tool in optimizing retention aid applications.

Abstract Interactions between the components of papermaking suspensions (e.g. fibres, fillers, fines and polymers) have a remarkable effect on various unit processes in papermaking. The filterability of fibre suspensions, which is a crucial property for example in paper sheet forming and solid recovery, is also known to be depended on particle interactions. However, due to the complex nature of the interactions, the role of these phenomena in fibre suspension filtration is still not fully understood. The focus of this thesis was to find out how phenomena associated to fibre flocculation, fibre deflocculation and filler particle deposition affect the filterability of fibre suspensions in terms of their dewaterability and retention. It was shown that the influence of fibre flocculation on dewatering is closely related to the structure of fibre flocs. More importantly, the internal density of flocs and factors that impacted the packing structure of filter cakes, such as floc size, played a crucial role in fibre suspension dewaterability. Dense flocs with a low internal porosity particularly induces fast water flow by a mechanism termed as the “easiest path mechanism” through the large voids around the flocs. The effect of fibre suspension dispersing on dewaterability and particularly fines retention was found to be associated to the mechanism of action of the deflocculation agent. Carboxymethylcellulose (CMC), the deflocculant used in this study, had detrimental effects on the dewatering of a pulp suspension both when being adsorbed on fibre surfaces and when remained in the liquid phase. However, adsorbed CMC causes more plugging of the filter cake because it disperses the fines more profoundly. Thus the adsorbed CMC also reduces fines retention considerably more than CMC did in the liquid phase. Filler deposition and retention was found to be significantly higher on pulp fines fractions of mechanical and chemical pulp than on fibre fractions due to the higher external surface area of fines. The surface charge densities of pulp fractions also affected their ability to adsorb fillers. Cationic charges of filler particles was in turn observed to induce deposition of fillers on fibre surfaces which increased retention but also the dewaterability of a fibre suspension due to a decrease in total surface area of a suspension.

Novas tecnologias para o tratamento de água potável vêm sendo empregadas na medida em que a utilização de sais de alumínio tem apresentado correlação com doenças de envelhecimento mental nos seres humanos. Os coagulantes orgânicos de origem vegetal podem substituir de forma satisfatória estes sais no tratamento convencional de água potável. A utilização de processos combinados utilizando membranas de ultrafiltração com coagulação é uma alternativa aos métodos convencionais de potabilização. Com este cenário, o presente trabalho tem como objetivo comparar o desempenho operacional de uma planta piloto de ultrafiltração com membranas submersas para produção de água potável a partir do Lago Guaíba, utilizando o coagulante convencional poli (cloreto de alumínio) (PAC) e um coagulante orgânico oriundo da casca da Acácia Negra (Acacia maernsii) Tanfloc SG, com a análise da morfologia, massa molar de corte e permeabilidade hidráulica da membrana e com análises da água bruta e filtrada. As membranas de fibra oca de Poliéter Sulfona (PES) com massa molar de corte de 50 kDa, permearam sob pressão fixa de -500 mbar, com ação de borbulhamento em testes de 140 horas para avaliação da performance e testes de 10 horas para avaliação da qualidade de permeado. Os resultados indicaram semelhança no desempenho operacional dos dois coagulantes quanto à redução da permeância hidráulica relativa, e a qualidade do permeado indicou que mesmo com a ausência de flocos no tanque de alimentação, não houve passagem significativa de coagulante para o permeado. Os parâmetros de potabilidade indicaram o enquadramento da água produzida nos padrões organolépticos na atual Portaria 2914/2011 do Ministério da Saúde.<br>New technologies to water treatment have been applied as the aluminum salts commonly used have shown correlations with mental diseases in human beings. The organic coagulants from natural sources can satisfactorily replace those inorganic salts in drinking water treatment. The hybrid processes join ultrafiltration membranes with coagulation are alternatives to the standard potabilization. The present study compares the operational behavior of a submersed ultrafiltration (UF) pilot plant producing drinking water from Guaíba Lake, using poli (aluminum chloride) (PAC) and an organic coagulant extracted from Acacia maernsii Tanfloc SG. The membrane and the permeate were investigated. The polyether sulfone hollow fiber membranes filtered with a -500 mbar constant vacuum and air bubbles through 140 hours for performance test and for 10 hour for permeate quality verification. The results showed similarity of the relative hydraulic permeability of the two coagulants, and even with the absence of visible flocs in the membrane tank, there were no significant coagulant carryover through the membrane. The analytical data pointed that the water produced with both coagulants had concentration bellow the Brazilian organoleptic standards, according to the Portaria 2914/2011 of the Health Ministry.

Coagulation/flocculation/sedimentation is a common pretreatment process prior to microfiltration (MF) or ultrafiltration (UF) to alleviate membrane fouling, however there has been limited research on floatation as the pretreatment separation process. The main objective of this study is to compare sedimentation with floatation as part of the pretreatment for ultrafiltration of Ottawa River water (ORW) with relatively high natural organic matter (NOM) content. Water samples pretreated at two full-scale plants were subjected to multiple-day UF membrane fouling tests (constant flux with backwash and chemical cleaning) using an automated bench-scale UF hollow fiber membrane system. For all the experiments, the transmembrane pressure (TMP) increased sharply during the beginning of the operation (~10 h), which indicated the adsorption was significant. In the later cycles, the TMP showed a more linear constant increase, which indicated the built up of the cake layers. The total fouling index (TFI), hydraulically irreversible fouling index (HIFI) and chemical irreversible fouling index (CIFI) for floated water were much smaller than those of settled waters during both summer and winter testing. Thus, for this type of water coagulation/floatation pretreatment was superior process compared to coagulation/sedimentation, the decreased fouling appears to be linked to greater hydrophobic NOM removal by the coagulation/floatation. For all the tests, HIFI/TFIs were less than 0.1, which is to mean most of the fouling was reversible by hydraulic backwashing.Large fluctuation of backwash efficiencies with time were found for all the tested waters. Enhanced chemical backwash with 100 ppm chlorine and chemical clean with 0.1N NaOH & 200 ppm chlorine were found to be very effective at reducing fouling for pretreated ORW. As expected longer filtration cycles resulted in greater fouling but with a slightly greater degree of hydraulically reversible fouling.

Abstract This study focused on web forming at a 5–10% consistency range, termed Ultra High Consistency (UHC). The study continued work done by Gullichsen with his research groups (1981–2007) and combined it with the HC forming research done by Valmet (HC, 1999–2004). The hypothesis was that by utilizing a rotor to fluidize suspension and a wedge to eliminate the free jet and thus prevent reflocculation, web forming at UHC is feasible at commercial speeds. The research method was experimental. The bulk of the research was conducted at pilot scale. A new UHC headbox was designed and mounted on a pilot former. The key elements of the headbox are the rotor and the wedge. As fluidization forms the base for UHC forming, this was evaluated at the pilot former using image analysis. In addition, fluidization was studied using a laboratory-scale device. Besides basic paper analysis, X-ray microtomography and sheet splitting methods were utilized to analyze the sheet structure. The results show that forming is possible within the focus area, 5–10% consistency and machine speeds of 150–600 m/min, although the operation potential of the UHC former is even wider. The results demonstrate that the wedge is needed for successful UHC forming, but the rotor is not required, providing the flow rate is sufficiently high. This indicates that various forces induced by the flow itself can be adequate to fluidize suspension for forming. The critical Reynolds number of full fluidization was found to be 200–250. The Reynolds numbers were estimated utilizing the linear dependencies found between the apparent viscosity and consistency, using the maximum mean flow velocities inside the headbox, and neglecting the possible rotation of the rotor. The corresponding critical flow velocities at 10% consistency are 12 and 19 m/s for a eucalyptus and pine pulp. The velocities are on average 70 and 60% lower than those given in the literature (40–50 m/s). The results reveal that the fiber orientation of UHC sheets is planar, the floc size of the web increases with consistency, the internal bond increases linearly with the floc size, and the tensile strength appears to decrease with increasing floc size. In consequence, it is postulated that the increase in the out-of-plane strength at the expense of in-plane strength with the consistency increase results from a more flocculated structure<br>Tiivistelmä Tutkimus keskittyi rainanmuodostukseen 5–10 % sakeudessa. Sakeusalue nimitettiin ultra korkeaksi (lyhenne UHC). Tämä työ jatkoi Gullichsenin ja hänen tutkimusryhmiensä tutkimustyötä (1981–2007) ja samalla yhdisti sen Valmetin tekemään suursakeusrainaustutkimukseen (HC, 1994–2004). Työn hypoteesina oli, että käyttämällä roottoria massan fluidisoimiseen sekä ns. wedgeä eliminoimaan vapaa suihku ja estämään jälleenflokkaantuminen, rainanmuodostus UHC-sakeudessa on mahdollista kaupallisissa nopeuksissa. Tutkimusmetodi oli kokeellinen. Pääosa tutkimuksesta suoritettiin koekonemittakaavassa. Uusi UHC-perälaatikko suunniteltiin ja asennettiin koeformeille. Perälaatikon pääelementit ovat pyörivä roottori ja wedge. Koska fluidisointi muodostaa UHC-rainauksen perustan, fluidisointia evaluoitiin koekoneella käyttäen kuva-analyysiä sekä tutkittiin lisäksi käyttäen röntgenmikrotomografia ja arkin halkaisu -metodeja. Tulokset osoittavat, että rainaaminen on mahdollista määritellyllä fokusalueella, 5–10 %sakeudessa ja konenopeudella150–600 m/min, joskin UHC-formerin toimintapotentiaali on vieläkin laajempi. Tulokset osoittavat, että wedge tarvitaan onnistuneeseen UHC-muodostamiseen, mutta roottoria ei tarvita, mikäli virtausnopeus on riittävän suuri. Tämä tarkoittaa, että virtauksen aikaansaamat voimat voivat itsessään olla riittäviä massan fluidisoimiseksi rainaamista varten. Täyden fluidisaation kriittisen Reynoldsin luvun havaittiin olevan välillä 200–250. Reynoldsin luvut arvioitiin käyttäen löydettyjä viskositeetin ja sakeuden välisiä lineaarisia riippuvuuksia, päävirtauksen maksiminopeuksia perälaatikossa ja jättäen huomioon ottamatta mahdollinen roottorin pyöriminen. Reynoldsin lukuja vastaavat kriittiset virtausnopeudet 10 % sakeudessa ovat eukalyptus- ja mäntymassalla 12 ja 19 m/s. Nopeudet ovat keskimäärin 70 ja 60 % pienempiä kuin kirjallisuudessa annetut (40–50 m/s). Tulokset osoittavat, että UHC-arkeissa kuituorientaatio on tasomainen, rainan flokkikoko kasvaa sakeuden kasvaessa, palstautumislujuus kasvaa lineaarisesti flokkikoon kanssa ja vetolujuus näyttäisi laskevan flokkikoon kasvaessa. Näin ollen esitetään, että sakeuden kasvaessa tapahtuva palstautumislujuuden kasvu tasolujuuksien kustannuksella johtuu flokkaantuneemmasta rakenteesta

Acidified dairy products are one of the oldest types of food products. Unfortunately all of them are low in dietary fibre. Thus, to improve health benefit of these products the idea of fortifying them with dietary fibre seems attractive. However dairy products enriched with Glucagel (a commercial product that is high in barley β-glucan) were found to suffer from textural defects. When the Glucagel concentration exceeded a certain value (5 g/L), dramatic phase separation was observed in set yogurt and yogurt drink with volume fraction of casein micelles greater then 0.108. To investigate interactions of β-glucan polymers and casein micelles in the milk prior to setting of yogurt, mixtures of yogurt milk and Glucagel were systematically studied. Depending on the volume fraction of casein micelles and the Glucagel concentration, a stable phase or a gel or a sedimented material could exist. The driving force for phase separation was depletion flocculation of casein micelles in the presence of β-glucan. The phase separation responsible for textural defects in yogurt systems supplemented with high amounts of Glucagel can be avoided by the reduction of β-glucan molecular weight, a process that limits the range of attraction between micelles. Incubation of Glucagel with lichenase for 90 min resulted in homogeneous (stable) yogurt systems with Glucagel concentrations as high as 10 g/L.

碩士<br>國立交通大學<br>環境工程研究所<br>82<br>On-line monitoring the state of coagulation/flocculation enables automatic control of coagulation process with respect to the condition of the chemical additive. A new method "Fiber- optic monitoring thehnique" as a tool has been employed to evaluate the state of flocculation, which is to measure the flutuating light intensity transmitted through a flowing suspension. The purpose of this study is to assess the feasibility for the application of monitoring the flocculation by using photometric dispersion analyzer (PDA), and to perform a series of batch flocculation tests with PDA under different conditions. The result shows that the fiber-optic technique is useful to monitor the state of aggregation with different coagulants and the variation of turbidity conditions, it provides a reliable index related to the floc size can be used in determing the optimum coagulant dosage. Nevertheless, it also can be used in the case of wastewater treatment. The result concludes that PDA is superior to streaming current detector in monitoring the state of flocculation.