Disc Filter External Models in an Integrated Simulation Environment

Työssä tutkittiin kiekkosuodattimeen liittyviä ulkoisia simulointimalleja integroidussa simulointiympäristössä. Työn tarkoituksena oli parantaa olemassa olevaa mekanistista kiekkosuodatinmallia. Malli laadittiin dynaamiseen paperiteollisuuden tarpeisiin tehtyyn simulaattoriin (APMS), jossa olevaan alkuperäiseen mekanistiseen malliin tehtiin ulkoinen lisämalli, joka käyttää hyväkseen kiekkosuodatinvalmistajan mittaustuloksia. Laitetiedon saatavuutta suodattimien käyttäjille parannettiin luomalla Internetissä sijaitsevalle palvelimelle kiekkosuodattimen laitetietomäärittelyt. Suodatinvalmistaja voi palvella asiakkaitaan viemällä laitetiedot palvelimelle ja yhdistämällä laitetiedon simulointimalliin. Tämä on mahdollista Internetin ylitse käytettävän integroidun simulointiympäristön avulla, jonka on tarkoitus kokonaisvaltaisesti yhdistää simulointi ja prosessisuunnittelu. Suunnittelijalle tarjotaan työkalut, joilla dynaaminen simulointi, tasesimulointi ja kaavioiden piirtäminen onnistuu prosessilaitetiedon ollessa saatavilla. Nämä työkalut on tarkoitus toteuttaa projektissa nimeltä Galleria, jossa luodaan prosessimalli- ja laitetietopalvelin Internetiin. Gallerian käyttöliittymän avulla prosessisuunnittelija voi käyttää erilaisia simulointiohjelmistoja ja niihin luotuja valmiita malleja, sekä saada käsiinsä ajan tasalla olevaa laitetietoa. Ulkoinen kiekkosuodatinmalli laskee suodosvirtaamat ja suodosten pitoisuudet likaiselle, kirkkaalle ja superkirkkaalle suodokselle. Mallin syöttöparametrit ovat kiekkojen pyörimisnopeus, sisään tulevan syötön pitoisuus, suotautuvuus (freeness) ja säätöparametri, jolla säädetään likaisen ja kirkkaan suodoksen keskinäinen suhde. Suotautuvuus kertoo mistä massasta on kyse. Mitä suurempi suotautuvuus on, sitä paremmin massa suodattuu ja sitä puhtaampia suodokset yleensä ovat. Mallin parametrit viritettiin regressioanalyysillä ja valmistajan palautetta apuna käyttäen. Käyttäjä voi valita haluaako hän käyttää ulkoista vai alkuperäistä mallia. Alkuperäinen malli täytyy ensin alustaa antamalla sille nominaaliset toimintapisteet virtaamille ja pitoisuuksille tietyllä pyörimisnopeudella. Ulkoisen mallin yhtälöitä voi käyttää alkuperäisen mallin alustamiseen, jos alkuperäinen malli toimii ulkoista paremmin. Ulkoista mallia voi käyttää myös ilman simulointiohjelmaa Galleria-palvelimelta käsin. Käyttäjälle avautuu näin mahdollisuus tarkastella kiekkosuodattimien parametreja ja nähdä suotautumistulokset oman työasemansa ääreltä mistä tahansa, kunhan Internetyhteys on olemassa. Työn tuloksena kiekkosuodattimien laitetiedon saatavuus käyttäjille parani ja alkuperäisen simulointimallin rajoituksia ja puutteita vähennettiin.

Wavelet Filter Parameterization for Compression of Spectral Images

Vaatimus kuvatiedon tiivistämisestä on tullut entistä ilmeisemmäksi viimeisen kymmenen vuoden aikana kuvatietoon perustuvien sovellutusten myötä. Nykyisin kiinnitetään erityistä huomiota spektrikuviin, joiden tallettaminen ja siirto vaativat runsaasti levytilaa ja kaistaa. Aallokemuunnos on osoittautunut hyväksi ratkaisuksi häviöllisessä tiedontiivistämisessä. Sen toteutus alikaistakoodauksessa perustuu aallokesuodattimiin ja ongelmana on sopivan aallokesuodattimen valinta erilaisille tiivistettäville kuville. Tässä työssä esitetään katsaus tiivistysmenetelmiin, jotka perustuvat aallokemuunnokseen. Ortogonaalisten suodattimien määritys parametrisoimalla on työn painopisteenä. Työssä todetaan myös kahden erilaisen lähestymistavan samanlaisuus algebrallisten yhtälöiden avulla. Kokeellinen osa sisältää joukon testejä, joilla perustellaan parametrisoinnin tarvetta. Erilaisille kuville tarvitaan erilaisia suodattimia sekä erilaiset tiivistyskertoimet saavutetaan eri suodattimilla. Lopuksi toteutetaan spektrikuvien tiivistys aallokemuunnoksen avulla.

Regression-based techniques for statistical decision making in single-case designs

The present study evaluates the performance of four methods for estimating regression coefficients used to make statistical decisions regarding intervention effectiveness in single-case designs. Ordinary least squares estimation is compared to two correction techniques dealing with general trend and one eliminating autocorrelation whenever it is present. Type I error rates and statistical power are studied for experimental conditions defined by the presence or absence of treatment effect (change in level or in slope), general trend, and serial dependence. The results show that empirical Type I error rates do not approximate the nominal ones in presence of autocorrelation or general trend when ordinary and generalized least squares are applied. The techniques controlling trend show lower false alarm rates, but prove to be insufficiently sensitive to existing treatment effects. Consequently, the use of the statistical significance of the regression coefficients for detecting treatment effects is not recommended for short data series.

Randomization tests for ABAB designs: Comparing-data-division-specific and common distributions

Monte Carlo simulations were used to generate data for ABAB designs of different lengths. The points of change in phase are randomly determined before gathering behaviour measurements, which allows the use of a randomization test as an analytic technique. Data simulation and analysis can be based either on data-division-specific or on common distributions. Following one method or another affects the results obtained after the randomization test has been applied. Therefore, the goal of the study was to examine these effects in more detail. The discrepancies in these approaches are obvious when data with zero treatment effect are considered and such approaches have implications for statistical power studies. Data-division-specific distributions provide more detailed information about the performance of the statistical technique.

Sidelobe elimination for generalized synthetic discriminant functions by a two-filter correlation and subsequent postprocessing of the intensity distributions

One of the most important problems in optical pattern recognition by correlation is the appearance of sidelobes in the correlation plane, which causes false alarms. We present a method that eliminate sidelobes of up to a given height if certain conditions are satisfied. The method can be applied to any generalized synthetic discriminant function filter and is capable of rejecting lateral peaks that are even higher than the central correlation. Satisfactory results were obtained in both computer simulations and optical implementation.

Using computational fluid dynamics to predict head losses in the auxiliary elements of a microirrigation sand filter

It is often assumed that total head losses in a sand filter are solely due to the filtration media and that there are analytical solutions, such as the Ergun equation, to compute them. However, total head losses are also due to auxiliary elements (inlet and outlet pipes and filter nozzles), which produce undesirable head losses because they increase energy requirements without contributing to the filtration process. In this study, ANSYS Fluent version 6.3, a commercial computational fluid dynamics (CFD) software program, was used to compute head losses in different parts of a sand filter. Six different numerical filter models of varying complexities were used to understand the hydraulic behavior of the several filter elements and their importance in total head losses. The simulation results show that 84.6% of these were caused by the sand bed and 15.4% were due to auxiliary elements (4.4% in the outlet and inlet pipes, and 11.0% in the perforated plate and nozzles). Simulation results with different models show the important role of the nozzles in the hydraulic behavior of the sand filter. The relationship between the passing area through the nozzles and the passing area through the perforated plate is an important design parameter for the reduction of total head losses. A reduced relationship caused by nozzle clogging would disproportionately increase the total head losses in the sand filter

Development of a Filter Aid Proportioning, Mixing, and Feeding System for a Polishing Filter

The purpose of this work was to study the characteristics of the most commonly used filter aid materials and their influences on the design of proportioning, mixing, and feeding system for polishing filter family. Based on the literature survey and hands-on experience a system was designed with defined equipment and capital and operating costs. The system was designed to serve precoating and bodyfeeding applications and is easily extended to be used in multiple filter processes. Also a test procedure was carried out where influences of flux and filter cloths to accumulated cake were studied. Filter aid is needed in challenging conditions to improve filtration efficiency and cleaning, and thus extend the operating life of the filter media. Filter aid preparation and feeding system was designed for the use of two different filter aids; precoat and bodyfeed. Precoating is used before the filtration step initiates. If the solids in the filterable solution have a tendency to clog the filter bag easily, precoat is used on the filter bag to obtain better filtration efficiency and quality. Diatomite or perlite is usually used as a precoating substance. The intention is to create a uniform cake to the overall surface of the filter cloth, with predetermined thickness, 2 – 5 mm. This ensures that the clogging of the filter cloth is reduced and the filtration efficiency is increased. Bodyfeed is used if the solids in the filterable solution have a tendency to form a sticky impermeable filter cake. The cake properties are enhanced by maintaining the permeability of the accumulating cake by using the filter aid substance as bodyfeed during the filtration process.

Cleaning of ceramic filter plates

In this thesis, cleaning of ceramic filter plates clogged by iron oxides was studied. Oxalic acid is considered as the most effective cleaning agent for the plates fouled by iron oxides, but when using oxalic acid, sparingly soluble calcium oxalate may be formed and it can blind the filter media. Suitability of another chemical for cleaning the plates clogged by iron oxides was studied in this thesis. The literature part was mostly about the properties of the chemical, about its reactions, industrial uses, safety issues etc. In the experimental part, the efficiency of the chemical for cleaning of the ceramic plates clogged by iron oxides was studied. Two kinds of plates were used in the experiments; the others were clogged by hematite and the others by magnetite. Both soaking and flow-through experiments were done. A suitable concentration, pH and temperature were tried to find in the experiments. Also the effect of ultrasound was studied. The efficiency of the cleaning was examined by measuring the permeability of the plates during the experiments. ICP-OES analysis was performed for determining the amount of dissolved iron in the washing solution. Some experiments were also done with oxalic acid. The results from the oxalic acid experiments were compared to the results from the experiments with the other chemical. In the experiments with the other chemical, the permeability increased more and the amounts of dissolved iron were larger. According to the results from the experiments, the method of application of the washing solutions had an impact on the washing results.

Electrochemical Characterisation of Filter Media Properties and Their Exploitation in Enhanced Filtration

Streaming potential measurements for the surface charge characterisation of different filter media types and materials were used. The equipment was developed further so that measurements could be taken along the surfaces, and so that tubular membranes could also be measured. The streaming potential proved to be a very useful tool in the charge analysis of both clean and fouled filter media. Adsorption and fouling could be studied, as could flux, as functions of time. A module to determine the membrane potential was also constructed. The results collected from the experiments conducted with these devices were used in the study of the theory of streaming potential as an electrokinetic phenomenon. Several correction factors, which are derived to take into account the surface conductance and the electrokinetic flow in very narrow capillaries, were tested in practice. The surface materials were studied using FTIR and the results compared with those from the streaming potentials. FTIR analysis was also found to be a useful tool in the characterisation of filters, as well as in the fouling studies. Upon examination of the recorded spectra from different depths in a sample it was possible to determine the adsorption sites. The influence of an external electric field on the cross flow microflltration of a binary protein system was investigated using a membrane electroflltration apparatus. The results showed that a significant improvement could be achieved in membrane filtration by using the measured electrochemical properties to help adjust the process conditions.

Counter-current Washing of Filter Cakes

The main objective of this thesis was to compare the efficiency of counter-current and co-current filter cake washing techniques. Filter cake washing is a common unit operation which is used in the chemical process industry for improving the recovery of the liquid phase or for purifying the solid phase of the filter cake. Counter-current displacement washing is more difficult to arrange and it requires additional process equipment but the advantage of counter-current method is that the consumption of wash water that is required for achieving certain filter cake purity may be considerably decreased when compared to the co-current washing method. This is true especially for materials that are difficult to wash. The literature part of this thesis consists of a review of filter cake washing in general, including the basic principles of co-current and counter-current techniques, and a description of the structure and operation of a horizontal vacuum belt filter, which is the equipment considered in the experimental part of this thesis. Also the most common cake washing models are introduced. The experiments were performed by washing wheat apatite filter cakes in a laboratory scale vacuum filter by using both co-current and counter-current washing methods. The main results of these tests were the washing curves that relate the purity of the filter cake to the amount of wash liquid used. Comparison between the obtained washing curves showed that both washing methods could be efficiently applied for achieving good washing results. The differences between the wash liquid consumptions in the co-current and counter-current washing methods were found to be surprisingly small but this is most probably explained by the relatively good washing characteristics of the apatite cakes. The washing models introduced in the literature part were compared with the results obtained from the experiments and it was found out that the studied cake washing processes could be described

High pressure compression of filter cakes

The purpose of this thesis was to investigate the compression of filter cakes at high filtration pressures with five different test materials and to compare the energy consumption of high pressure compression with the energy consumption of thermal drying. The secondary target of this study was to investigate the particle deformation of test materials during filtration and compression. Literature part consists of basic theory of filtration and compression and of the basic parameters that influence the filtration process. There is also a brief description about all of the test materials including their properties and their industrial production and processing. Theoretical equations for calculating the energy consumptions of the filtrations at different conditions are also presented. At the beginning of the experiments at experimental part, the basic filtration tests were done with all the five test materials. Filtration tests were made at eight different pressures, from 6 bars up to 100 bars, by using piston press pressure filter. Filtration tests were then repeated by using a cylinder with smaller slurry volume than in the first series of filtration tests. Separate filtration tests were also done for investigating the deformation of solid particles during filtration and for finding the optimal curve for raising the filtration pressure. Energy consumption differences between high pressure filtration and ideal thermal drying process were done partly experimentally and partly by using theoretical calculation equations. By comparing these two water removal methods, the optimal ranges for their use were found considering their energy efficiency. The results of the measurements shows that the filtration rate increased and the moisture content of the filter cakes decreased as the filtration pressure was increased. Also the porosity of the filter cakes mainly decreased when the filtration pressure was increased. Particle deformation during the filtration was observed only with coal particles.

Assessing functional relations in single-case designs: Quantitative proposals in the context of the evidence-based movement

In the context of the evidence-based practices movement, the emphasis on computing effect sizes and combining them via meta-analysis does not preclude the demonstration of functional relations. For the latter aim, we propose to augment the visual analysis to add consistency to the decisions made on the existence of a functional relation without losing sight of the need for a methodological evaluation of what stimuli and reinforcement or punishment are used to control the behavior. Four options for quantification are reviewed, illustrated, and tested with simulated data. These quantifications include comparing the projected baseline with the actual treatment measurements, on the basis of either parametric or nonparametric statistics. The simulated data used to test the quantifications include nine data patterns in terms of the presence and type of effect and comprising ABAB and multiple baseline designs. Although none of the techniques is completely flawless in terms of detecting a functional relation only when it is present but not when it is absent, an option based on projecting split-middle trend and considering data variability as in exploratory data analysis proves to be the best performer for most data patterns. We suggest that the information on whether a functional relation has been demonstrated should be included in meta-analyses. It is also possible to use as a weight the inverse of the data variability measure used in the quantification for assessing the functional relation. We offer an easy to use code for open-source software for implementing some of the quantifications.

Assigning and combining probabilities in single-case designs: A second study

The present study builds on a previous proposal for assigning probabilities to the outcomes computed using different primary indicators in single-case studies. These probabilities are obtained comparing the outcome to previously tabulated reference values and reflect the likelihood of the results in case there was no intervention effect. The current study explores how well different metrics are translated into p values in the context of simulation data. Furthermore, two published multiple baseline data sets are used to illustrate how well the probabilities could reflect the intervention effectiveness as assessed by the original authors. Finally, the importance of which primary indicator is used in each data set to be integrated is explored; two ways of combining probabilities are used: a weighted average and a binomial test. The results indicate that the translation into p values works well for the two nonoverlap procedures, with the results for the regression-based procedure diverging due to some undesirable features of its performance. These p values, both when taken individually and when combined, were well-aligned with the effectiveness for the real-life data. The results suggest that assigning probabilities can be useful for translating the primary measure into the same metric, using these probabilities as additional evidence on the importance of behavioral change, complementing visual analysis and professional's judgments.

Hybrid LC Filter for Power Electronic Drives: Theory and Implementation

Power electronic converter drives use, for the sake of high efficiency, pulse-width modulation that results in sequences of high-voltage high-frequency steep-edged pulses. Such a signal contains a set of high harmonics not required for control purposes. Harmonics cause reflections in the cable between the motor and the inverter leading to faster winding insulation ageing. Bearing failures and problems with electromagnetic compatibility may also result. Electrical du/dt filters provide an effective solution to problems caused by pulse-width modulation, thereby increasing the performance and service life of the electrical machines. It is shown that RLC filters effectively decrease the reflection phenomena in the cable. Improved (simple, but effective) solutions are found for both differential- and common-mode signals; these solutions use a galvanic connection between the RLC filter star point and the converter DC link. Foil chokes and film capacitors are among the most widely used components in high-power applications. In actual applications they can be placed in different parts of the cabinet. This fact complicates the arrangement of the cabinet and decreases the reliability of the system. In addition, the inductances of connection wires may prevent filtration at high frequencies. This thesis introduces a new hybrid LC filter that uses a natural capacitance between the turns of the foil choke based on integration of an auxiliary layer into it. The main idea of the hybrid LC filter results from the fact that both the foil choke and the film capacitors have the same roll structure. Moreover, the capacitance between the turns (“intra capacitance”) of the foil inductors is the reason for the deterioration of their properties at high frequencies. It is shown that the proposed filter has a natural cancellation of the intra capacitance. A hybrid LC filter may contain two or more foil layers isolated from each other and coiled on a core. The core material can be iron or even air as in the filter considered in this work. One of the foils, called the main foil, can be placed between the inverter and the motor cable. Other ones, called auxiliary foils, may be connected in star to create differential-mode noise paths, and then coupled to the DC link midpoint to guarantee a traveling path, especially for the common-mode currents. This way, there is a remarkable capacitance between the main foil and the auxiliary foil. Investigations showed that such a system can be described by a simple equivalent LC filter in a wide range of frequencies. Because of its simple hybrid construction, the proposed LC filter can be a cost-effective and competitive solution for modern power drives. In the thesis, the application field of the proposed filter is considered and determined. The basics of hybrid LC filter design are developed further. High-frequency behaviour of the proposed filter is analysed by simulations. Finally, the thesis presents experimental data proving that the hybrid LC filter can be used for du/dt of PWM pulses and reduction of common-mode currents.