EFEITO DO DIOXIDO DE CARBONO SOBRE A ESTABILIDADE DA FASE Ca2Fe2O5 APLICADA NO PROCESSO DE DEGRADAÇÃO FOTOCATALITICO DO AZUL DE METILENO

Solid samples containing a Ca2Fe2O5 phase were synthesized using the Pechini method. The samples were characterized using X-ray diffraction, thermogravimetric analysis, differential thermal analysis, X-ray fluorescence, nitrogen adsorption/desorption isotherms, and scanning electron microscopy. The stability of the Ca2Fe2O5 phase was evaluated in the photocatalytic degradation of methylene blue (MB) in aqueous solution in the presence of bubbling gas (air, N2, or CO2). The presence of CO2 is known to suppress MB degradation. After the photocatalytic test, changes were observed in the crystalline phase of all systems. These results suggest the low stability of the Ca2Fe2O5 phase in aqueous systems and the significant effect of CO2 on the photocatalytic activity of the Ca2Fe2O5 phase.

OBTAINING ZnO IMMOBILIZED OVER DIFFERENT SUBSTRATES BY HYDROTHERMAL TREATMENT FOR PHOTOCATALYSIS APPLICATION

The aim of this work is to systematically explore the effect of the synthesis conditions of ZnO structures, immobilized on different substrates by hydrothermal treatment, in its photocatalytic activity. A circumscribed central composite design of experiments was used to analyze the effects of reagents stoichiometry, reaction time and temperature, covering a wide range of these variables. The substrates used were etched glass, copper and zinc foils. The photocatalytic activity of the as-obtained ZnO samples was evaluated through photocatalytic degradation of rhodamine B (RhB) in aqueous solution under UV irradiation. Zinc foils presented the best immobilized film quality and the maximum dye removal was 80% in one hour of UV exposure.

Täystehokonvertterin tehohäviöt ja hyötysuhde

Diplomityössä perehdytään tuuliturbineissa käytettyjen täystehokonvertterien tehohäviöihin ja hyötysuhteeseen. Täystehokonvertterissa generaattorin tuottama sähköteho tasasuunnataan hyvällä hyötysuhteella aktiivisella geenraattorisillalla konvertterin välipiiriin ja edelleen vaihtosuunnataan aktiivisella verkkovaihtosuuntaajasillalla siirtoverkkoon. Työn tarkoituksena on antaa yleiskuva tehohäviöiden jakautumisesta ja yksinkertaistaa niiden laskentaa. Häviömekanismit ja häviöiden määräytyminen esitellään pääkomponenttitasolla. Tehohäviöiden osalta keskitytään erityisesti muuntajateräksestä valmistettujen sinisuotimien ja du/dt-suotimien rautahäviöihin. Ongelmana rautahäviöiden määrittämisessä on korkeilla taajuuksilla tapahtuvat häviöt, joiden laskentaan ei ole yleensä saatavilla tarvittavia materiaaliparametrejä. Tehohäviöiden laskentaa varten toteutettu laskentasovellus on esitelty periaatteellisina vuokaavioina ja sovelluksella saatavia tuloksia on esitetty ja vertailtu mitattuihin tuloksiin.

Pretreatment in membrane filtration of wood hydrolysate

Interest in recovery of valuable components from process streams has increased in recent years. Purpose of biorefinery is to utilize components that otherwise would go to waste. Hemicelluloses, for example, could be utilized in production of many valuable products. One possible way to separate and fractionate hemicelluloses is membrane filtration. In the literature part of this work membrane fouling in filtration processes of pulp and paper process- and wastewaters was investigated. Especially purpose was to find out the possible fouling compounds, after which facilities to remove or modify such components less harmful were studied. In the experimental part different pretreatment methods, mainly to remove or degrade lignin from wood hydrolysate, were studied. In addition, concentration of hemicelluloses and separation from lignin were examined with two ultrafiltration membranes; UFX5 and RC70PP. Changes in feed solution, filtration capacity and fouling of membranes were used to evaluate the effects of pretreatment methods. Changes in hydrolysate composition were observed with different analysis methods. Filtration of hydrolysate proved to be challenging, especially with the UFX5 membrane. The more hydrophilic RC70PP membrane did not seem to be fouled as severely as the UFX5 membrane, according to pure water flux measurements. The UFX5 membrane retained hemicelluloses rather well, but problems arose from rapid flux decline resulting from concentration polarization and fouling of membrane. Most effective pretreatment methods in the case with the UFX5 membrane proved to be prefiltration with the RC70PP membrane, activated carbon adsorption and photocatalytic oxidation using titanium dioxide and UV radiation. An additional experiment with PHW extract showed that pulsed corona discharge treatment degraded lignin quite efficiently and thus improved filtration capacity remarkably, even over six times compared to the filtration with untreated extract.

Line filter optimization in elevator use

The purpose of this thesis was to create design a guideline for an LCL-filter. This thesis reviews briefly the relevant harmonics standards, old filter designs and problems faced with the previous filters. This thesis proposes a modified design method based on the “Liserre’s method” presented in the literature. This modified method will take into account network parameters better. As input parameters, the method uses the nominal power, allowed ripple current in converter and network side and desired resonant frequency of the filter. Essential component selection issues for LCL-filter, such as heating, voltage strength, current rating etc. are also discussed. Furthermore, a simulation model used to verify the operation of the designed filter in nominal power use and in transient situations is included in this thesis.

Production planning development in global manufacturing company

Larox Corporation is a provider of full service filtration in solid and liquid separation. Larox develops, designs, manufactures and supplies industrial filters. By Larox’s continuous development principle, a project for more efficient production was started. At the same time production planning was taken under review. Aim for this Master’s thesis was to find software designed for production planning purposes replacement for old Microsoft Excel based method. In this Master’s thesis current way of production planning was thoroughly analyzed and improvement targets were specified and also requirements for new software were assigned. Primary requirements for new software were possibility to production scheduling, planning, follow-up and also for long-time capacity planning and tracking. Also one demand was that new software should have data link to Larox’s current ERP-system. Result of this Master’s thesis was to start using Larox’s ERP-system also for production planning purposes. New mode of operation fulfils all requirements which were placed to new system. By using new method of production planning, production planners can get more easier and reliable data than from current system.

Synthesis and characterization of Fe(III)-doped ceramic membranes of titanium dioxide and its application in photoelectrocatalysis of a textile dye

Pure and Fe(III)-doped TiO2 suspensions were prepared by the sol gel method with the use of titanium isopropoxide (Ti(OPri)4) as precursor material. The properties of doped materials were compared to TiO2 properties based on the characterization by thermal analysis (TG-DTA and DSC), X-ray powder diffractometry and spectroscopy measurements (FTIR). Both undoped and doped TiO2 suspensions were used to coat metallic substrate as a mean to make thin-film electrodes. Thermal treatment of the precursors at 400ºC for 2 h in air resulted in the formation of nanocrystalline anatase TiO2. The thin-film electrodes were tested with respect to their photocatalytic performance for degradation of a textile dye in aqueous solution. The plain TiO2 remains as the best catalyst at the conditions used in this report.

Online Ultrasound Measurements of Membrane Compaction

There are several filtration applications in the pulp and paper industry where the capacity and cost-effectiveness of processes are of importance. Ultrafiltration is used to clean process water. Ultrafiltration is a membrane process that separates a certain component or compound from a liquid stream. The pressure difference across the membrane sieves macromolecules smaller than 0.001-0.02 μm through the membrane. When optimizing the filtration process capacity, online information about the conditions of the membrane is needed. Fouling and compaction of the membrane both affect the capacity of the filtration process. In fouling a “cake” layer starts to build on the surface of the membrane. This layer blocks the molecules from sieving through the membrane thereby decreasing the yield of the process. In compaction of the membrane the structure is flattened out because of the high pressure applied. The higher pressure increases the capacity but may damage the structure of the membrane permanently. Information about the compaction is needed to effectively operate the filters. The objective of this study was to develop an accurate system for online monitoring of the condition of the membrane using ultrasound reflectometry. Measurements of ultrafiltration membrane compaction were made successfully utilizing ultrasound. The results were confirmed by permeate flux decline, measurements of compaction with a micrometer, mechanical compaction using a hydraulic piston and a scanning electron microscope (SEM). The scientific contribution of this thesis is to introduce a secondary ultrasound transducer to determine the speed of sound in the fluid used. The speed of sound is highly dependent on the temperature and pressure used in the filters. When the exact speed of sound is obtained by the reference transducer, the effect of temperature and pressure is eliminated. This speed is then used to calculate the distances with a higher accuracy. As the accuracy or the resolution of the ultrasound measurement is increased, the method can be applied to a higher amount of applications especially for processes where fouling layers are thinner because of smaller macromolecules. With the help of the transducer, membrane compaction of 13 μm was measured in the pressure of 5 bars. The results were verified with the permeate flux decline, which indicated that compaction had taken place. The measurements of compaction with a micrometer showed compaction of 23–26 μm. The results are in the same range and confirm the compaction. Mechanical compaction measurements were made using a hydraulic piston, and the result was the same 13 μm as obtained by applying the ultrasound time domain reflectometry (UTDR). A scanning electron microscope (SEM) was used to study the structure of the samples before and after the compaction.

Water treatment by multistage filtration system with natural coagulant from Moringa oleifera seeds

This study presents an evaluation of a pilot multistage filtration system (MSF) with different dosages, 131 mg L-1 and 106 mg L-1, of the natural coagulant extracted from Moringa oleifera seeds in pre-filtration and slow filtration stages, respectively. The system was comprised by a dynamic pre-filter unit, two upflow filters in parallel and four slow filters in parallel, and in one of the four filters had the filter media altered. The performance of the system was evaluated by monitoring some water quality parameters such as: turbidity, apparent color and slow filter load loss. The stages that have received the coagulant solution had better treatment efficiency compared with the steps without it. However, the direct application of the coagulant solution in the slow filter caused rapid clogging of the non-woven blanket and shorter career length.

Periodic inspection of sprayers: diagnostic to the northern of Paraná

To optimize the use of pesticides, several countries have carried out periodic inspections in agricultural sprayers. In Brazil, knowing the conditions of this machinery canguide researches and investments in guidelines for its use and maintenance. The objective of this study was to verify the state of sprayer maintenance used in the North of the state of Paraná, in Brazil. Several sprayer items were evaluated, such as: presence, status and scale of the manometer, status of the hose, status of the anti-drip component, presence of leaks, status of the bar, status of the filters, state of the spraying nozzles and errors in the targeted flow rate. Machines were named as approved when there was no failure in any item evaluated. The factor that caused the biggest level of reprove among the machines was incorrect scale of manometers, which reproved 84.55% of the machines evaluated. Other outstanding factor was the incorrect flow rate in 75.5% of the tested machines. Only one unit was approved from the total of 110 evaluated sprayers.

Kartonkijätteestä bioetanolia - Hydrolysoitujen sokerien erotus ja väkevöinti fermentointia varten

Tässä diplomityössä tutkittiin upotettavien membraanisuodattimien soveltuvuutta sakean hydrolysaattin suodattamiseen ja esisuodatettujen sokereiden väkevöintiä membraanisuodatuksella fermentointia varten. Työssä käytettiin kierrätyskartongista entsyymien avulla valmistettua hydrolysaattia. Sakean hydrolysaatin suodattamiseen käytettiin Kubota Membranesin upposuodatusmoduuleja ja suodatuslaitteistoa. Upposuodatusmoduulien likaantumisen vähentämiseksi suodatuksissa käytettiin ilmasekoitusta ja vastavirta-pesua. Upposuodatusmoduulilla kirkastettua hydrolysaattia väkevöitiin nanosuodatuksella ja tulosta verrattiin painesuodatuksella kirkastetun hydrolysaatin nanosuodatukseen. Konsentrointisuodatusten alussa testattiin neljää nanosuodatuskalvoa hydrolysaatin konsentrointiin. Sokereiden konsentrointiin valittiin Dow FilmTecTM NF-270 nanosuodatuskalvo sen korkean sokeriretention ja hyvän vuon perusteella. Sakean hydrolysaatin esisuodatuksessa ei upotettavien membraanimoduulien ja painesuodatuksen välillä havaittu merkittäviä eroja. Työn perusteella upposuodatusmoduulien käyttö sakean hydrolysaatin suodattamisessa on kuitenkin mahdollista. Tämä mahdollistaisi sokereiden jatkuvatoimisen erottamisen hydrolysaatista. Konsentrointisuodatuksissa molemmilla esisuodatetuilla hydrolysaateilla saavutettiin yli 10 % sokerikonsentraatio ilman suurta sokerihävikkiä. Sokeriretentio pysyi myös konsentraation kasvaessa 80 % yläpuolella.

Field-Programmable Gate Array Card for Readout and Control of Cryoelectronics

The main goal of the present Master’s Thesis project was to create a field-programmable gate array (FPGA) based system for the control of single-electron transistors or other cryoelectronic devices. The FPGA and similar technologies are studied in the present work. The fixed and programmable logic are compared with each other. The main features and limitations of the hardware used in the project are investigated. The hardware and software connections of the device to the computer are shown in detail. The software development techniques for FPGA-based design are described. The steps of design for programmable logic are considered. Furthermore, the results of filters implemented in the software are illustrated.

Fotokatalyyttinen kalvonpesu

Fotokatalyysillä tarkoitetaan spontaania kemiallista reaktiota, joka tapahtuu fotokatalyytin absorboidessa valoa. Reaktio voi tapahtua joko katalyytin pinnalla tai sen läheisyydessä, mutta fotokatalyytti pysyy reaktiossa muuttumattomana. Ominaisuuksiltaan paras ja eniten tutkittu fotokatalyyttinen materiaali on titaanidioksidi, jolla on säteilytettynä kyky hajottaa orgaanisia molekyylejä hiilidioksidiksi ja vedeksi. Fotokatalyysin käyttömahdollisuuksia tutkitaan membraanikalvojen puhdistamisessa kalvojen käyttöiän ja erotustehokkuuden parantamiseksi. Nykyisin kalvojen puhdistamiseen käytetään useimmiten kemiallista pesua, jonka tuloksena on usein haitallisia yhdisteitä sisältävä liuos. Fotokatalyyttinen puhdistus voisi olla ratkaisu ongelmaan, sillä sen avulla voitaisiin puhdistamisessa käytettävien kemikaalien ja siinä muodostuvien jätteiden määrää vähentää. Tämän työn kokeellisessa osassa tutkittiin polyvinyylideenifluoridikalvon (PVDF) kestävyyttä ja puhdistumista fotokatalyyttisissä reaktioissa. PVDF:n on todettu olevan erinomainen kalvomateriaali, koska se on termisesti stabiili ja se kestää hyvin kemikaaleja, kuten orgaanisia liuottimia, happoja ja emäksiä. Työssä todettiin PVDF-kalvon puhdistuvan UV/TiO2-käsittelyn avulla. Kalvo puhdistui parhaiten, kun käytettiin 0,425 m- % TiO2-liuosta. Puhdistumista havainnoitiin sekä puhtaan veden vuon mittauksilla että värjäämällä käsiteltyjä kalvoja ja mittaamalla niiden värinintensiteetti.

Membraanin modifiointi happo- ja alkoholikäsittelyillä

Tässä diplomityössä tutkittiin alkoholilla ja orgaanisella hapolla tehtävien esikäsittelyiden vaikutusta nanosuodatuskalvon ominaisuuksiin. Työn tarkoituksena oli parantaa nanosuodatuskalvon fraktiointiominaisuuksia sekä kasvattaa monosakkaridien suotautuvuutta. Tarkasteluissa käytetty membraani oli GE Osmonicsin valmistamaa Desal-5 DL nanosuodatuskalvoa, jota modifioitiin erilaisilla maitohappo- ja isopropanoliesikäsittelyillä. Suodatukset tehtiin kahdella erilaisella laboratoriomittakaavan levysuotimella käyttäen malliaineina väkevää sokeriliuosta sekä laimeampaa sokeri-suola-liuosta. Happo- ja alkoholiesikäsiteltyjen kalvojen vuo- ja retentioarvoja verrattiin referensseinä käytettyjen vesiliotettujen kalvojen vastaaviin arvoihin. Puhtaat esikäsitellyt kalvot analysoitiin myös tarkemmin kalvoissa tapahtuneiden muutosten ymmärtämiseksi. Suodatusten ja analyysitulosten perusteella sekä alkoholi- että happoesikäsittelyt paransivat nanosuodatuskalvon ominaisuuksia parantaen sokerivuota, heikentämättä kuitenkaan kalvon fraktiointikykyä eri moolimassan omaavien sokereiden suhteen. Hapolla saavutettiin hieman alkoholikäsittelyä suotuisammat muutokset, mutta molemmilla käsittelyillä haluttujen komponenttien retentio monesti jopa parani referenssikalvoon verrattuna. Havaitut muutokset kalvoissa olivat pääosin fysikaalisia, mutta erityisesti happokäsittely muutti kalvon rakennetta myös kemiallisesti. Molemmat käsittelyt lisäsivät myös tarkasteltavan membraanin hydrofiilisuutta.

Active inverter output filtering methods

Frequency converters are widely used in the industry to enable better controllability and efficiency of variable speed AC motor drives. Despite these advantages, certain challenges concerning the inverter and motor interfacing have been present for decades. As insulated gate bipolar transistors entered the market, the inverter output voltage transition rate significantly increased compared with their predecessors. Inverters operate based on pulse width modulation of the output voltage, and the steep voltage edge fed by the inverter produces a motor terminal overvoltage. The overvoltage causes extra stress to the motor insulation, which may lead to a prematuremotor failure. The overvoltage is not generated by the inverter alone, but also by the sum effect of the motor cable length and the impedance mismatch between the cable and the motor. Many solutions have been shown to limit the overvoltage, and the mainstream products focus on passive filters. This doctoral thesis studies an alternative methodology for motor overvoltage reduction. The focus is on minimization of the passive filter dimensions, physical and electrical, or better yet, on operation without any filter. This is achieved by additional inverter control and modulation. The studied methods are implemented on different inverter topologies, varying in nominal voltage and current.For two-level inverters, the studied method is termed active du/dt. It consists of a small output LC filter, which is controlled by an independent modulator. The overvoltage is limited by a reduced voltage transition rate. For multilevel inverters, an overvoltage mitigation method operating without a passive filter, called edge modulation, is implemented. The method uses the capability of the inverter to produce two switching operations in the same direction to cancel the oscillating voltages of opposite phases. For parallel inverters, two methods are studied. They are both intended for two-level inverters, but the first uses individual motor cables from each inverter while the other topology applies output inductors. The overvoltage is reduced by interleaving the switching operations to produce a similar oscillation accumulation as with the edge modulation. The implementation of these methods is discussed in detail, and the necessary modifications to the control system of the inverter are presented. Each method is experimentally verified by operating industrial frequency converters with the modified control. All the methods are found feasible, and they provide sufficient overvoltage protection. The limitations and challenges brought about by the methods are discussed.