Process intensification: From optimised flow patterns to microprocess technology

This thesis is focused on process intensification. Several significant problems and applications of this theme are covered. Process intensification is nowadays one of the most popular trends in chemical engineering and attempts have been made to develop a general, systematic methodology for intensification. This seems, however, to be very difficult, because intensified processes are often based on creativity and novel ideas. Monolith reactors and microreactors are successful examples of process intensification. They are usually multichannel devices in which a proper feed technique is important for creating even fluid distribution into the channels. Two different feed techniques were tested for monoliths. In the first technique a shower method was implemented by means of perforated plates. The second technique was a dispersion method using static mixers. Both techniques offered stable operation and uniform fluid distribution. The dispersion method enabled a wider operational range in terms of liquid superficial velocity. Using dispersion method, a volumetric gas-liquid mass transfer coefficient of 2 s-1 was reached. Flow patterns play a significant role in terms of the mixing performance of micromixers. Although the geometry of a T-mixer is simple, channel configurations and dimensions had a clear effect on mixing efficiency. The flow in the microchannel was laminar, but the formation of vortices promoted mixing in micro T-mixers. The generation of vortices was dependent on the channel dimensions, configurations and flow rate. Microreactors offer a high ratio of surface area to volume. Surface forces and interactions between fluids and surfaces are, therefore, often dominant factors. In certain cases, the interactions can be effectively utilised. Different wetting properties of solid materials (PTFE and stainless steel) were applied in the separation of immiscible liquid phases. A micro-scale plate coalescer with hydrophilic and hydrophobic surfaces was used for the continuous separation of organic and aqueous phases. Complete phase separation occurred in less than 20 seconds, whereas the separation time by settling exceeded 30 min. Fluid flows can be also intensified in suitable conditions. By adding certain additives into turbulent fluid flow, it was possible to reduce friction (drag) by 40 %. Drag reduction decreases frictional pressure drop in pipelines which leads to remarkable energy savings and decreases the size or number of pumping facilities required, e.g., in oil transport pipes. Process intensification enables operation often under more optimal conditions. The consequent cost savings from reduced use of raw materials and reduced waste lead to greater economic benefits in processing.

Modeling reaction kinetics and mass transfer in ozonation in water solutions

This dissertation is based on four articles dealing with modeling of ozonation. The literature part of this considers some models for hydrodynamics in bubble column simulation. A literature review of methods for obtaining mass transfer coefficients is presented. The methods presented to obtain mass transfer are general models and can be applied to any gas-liquid system. Ozonation reaction models and methods for obtaining stoichiometric coefficients and reaction rate coefficients for ozonation reactions are discussed in the final section of the literature part. In the first article, ozone gas-liquid mass transfer into water in a bubble column was investigated for different pH values. A more general method for estimation of mass transfer and Henry’s coefficient was developed from the Beltrán method. The ozone volumetric mass transfer coefficient and the Henry’s coefficient were determined simultaneously by parameter estimation using a nonlinear optimization method. A minor dependence of the Henry’s law constant on pH was detected at the pH range 4 - 9. In the second article, a new method using the axial dispersion model for estimation of ozone self-decomposition kinetics in a semi-batch bubble column reactor was developed. The reaction rate coefficients for literature equations of ozone decomposition and the gas phase dispersion coefficient were estimated and compared with the literature data. The reaction order in the pH range 7-10 with respect to ozone 1.12 and 0.51 the hydroxyl ion were obtained, which is in good agreement with literature. The model parameters were determined by parameter estimation using a nonlinear optimization method. Sensitivity analysis was conducted using object function method to obtain information about the reliability and identifiability of the estimated parameters. In the third article, the reaction rate coefficients and the stoichiometric coefficients in the reaction of ozone with the model component p-nitrophenol were estimated at low pH of water using nonlinear optimization. A novel method for estimation of multireaction model parameters in ozonation was developed. In this method the concentration of unknown intermediate compounds is presented as a residual COD (chemical oxygen demand) calculated from the measured COD and the theoretical COD for the known species. The decomposition rate of p-nitrophenol on the pathway producing hydroquinone was found to be about two times faster than the p-nitrophenol decomposition rate on the pathway producing 4- nitrocatechol. In the fourth article, the reaction kinetics of p-nitrophenol ozonation was studied in a bubble column at pH 2. Using the new reaction kinetic model presented in the previous article, the reaction kinetic parameters, rate coefficients, and stoichiometric coefficients as well as the mass transfer coefficient were estimated with nonlinear estimation. The decomposition rate of pnitrophenol was found to be equal both on the pathway producing hydroquinone and on the path way producing 4-nitrocathecol. Comparison of the rate coefficients with the case at initial pH 5 indicates that the p-nitrophenol degradation producing 4- nitrocathecol is more selective towards molecular ozone than the reaction producing hydroquinone. The identifiability and reliability of the estimated parameters were analyzed with the Marcov chain Monte Carlo (MCMC) method. @All rights reserved. No part of the publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of the author.

Methods to test gas tightness of packages

One of the primary goals for food packages is to protect food against harmful environment, especially oxygen and moisture. The gas transmission rate is the total gas transport through the package, both by permeation through the package material and by leakage through pinholes and cracks. The shelf life of a product can be extended, if the food is stored in a gas tight package. Thus there is a need to test gas tightness of packages. There are several tightness testing methods, and they can be broadly divided into destructive and nondestructive methods. One of the most sensitive methods to detect leaks is by using a non destructive tracer gas technique. Carbon dioxide, helium and hydrogen are the most commonly used tracer gases. Hydrogen is the lightest and the smallest of all gases, which allows it to escape rapidly from the leak areas. The low background concentration of H2 in air (0.5 ppm) enables sensitive leak detection. With a hydrogen leak detector it is also possible to locate leaks. That is not possible with many other tightness testing methods. The experimental work has been focused on investigating the factors which affect the measurement results with the H2leak detector. Also reasons for false results were searched to avoid them in upcoming measurements. From the results of these experiments, the appropriate measurement practice was created in order to have correct and repeatable results. The most important thing for good measurement results is to keep the probe of the detector tightly against the leak. Because of its high diffusion rate, the HZ concentration decreases quickly if holding the probe further away from the leak area and thus the measured H2 leaks would be incorrect and small leaks could be undetected. In the experimental part hydrogen, oxygen and water vapour transmissions through laser beam reference holes (diameters 1 100 μm) were also measured and compared. With the H2 leak detector it was possible to detect even a leakage through 1 μm (diameter) within a few seconds. Water vapour did not penetrate even the largest reference hole (100 μm), even at tropical conditions (38 °C, 90 % RH), whereas some O2 transmission occurred through the reference holes larger than 5 μm. Thus water vapour transmission does not have a significant effect on food deterioration, if the diameter of the leak is less than 100 μm, but small leaks (5 100 μm) are more harmful for the food products, which are sensitive to oxidation.

The evaluation of hazardous gas components caused by the thermal degradation of plant oils and animal fats

Neste Oil has introduced plant oils and animal fats for the production of NExBTL renewable diesel, and these raw materials differ from the conventional mineral based oils. One subject of new raw materials study is thermal degradation, or in another name pyrolysis, of these organic oils and fats. The aim of this master’s thesis is to increase knowledge on thermal degradation of these new raw materials, and to identify possible gaseous harmful thermal degradation compounds. Another aim is to de-termine the health and environmental hazards of identified compounds. One objective is also to examine the formation possibilities of hazardous compounds in the produc-tion of NExBTL-diesel. Plant oils and animal fats consist mostly of triglycerides. Pyrolysis of triglycerides is a complex phenomenon, and many degradation products can be formed. Based on the literature studies, 13 hazardous degradation products were identified, one of which was acrolein. This compound is very toxic and dangerous to the environment. Own pyrolysis experiments were carried out with rapeseed and palm oils, and with a mix-ture of palm oil and animal fat. At least 12 hazardous compounds, including acrolein, were analysed from the gas phase. According to the experiments, the factors which influence on acrolein formation are the time of the experiment, the sphere (air/hydrogen) in which the experiment is carried out, and the characteristics of the used oil. The production of NExBTL-diesel is not based on pyrolysis. This is why thermal degradation is possible only when abnormal process conditions prevail.

Hajupäästöjen tutkiminen Saint-Gobain Rakennustuotteet Oy:n Hyvinkään lasivillatehtaalla

Hajupäästöillä tarkoitetaan tavallisesti teollisen toiminnan aiheuttamia hajuaineiden päästöjä ympäristöön. Suomessa ympäristölainsäädäntö ei varsinaisesti kiellä hajuaineiden päästöjä mutta edellyttää kuitenkin, ettei niistä aiheudu merkittävää viihtyvyyshaittaa. Tässä työssä tutkittiin hajupäästöjä Saint-Gobain Rakennustuotteet Oy:n Hyvinkään lasivillatehtaalla. Tavoitteena työssä oli selvittää, mikä on tehtaan aiheuttamien päästöjen hajuvaikutus, ja mitä hajuyhdisteitä valmistusprosessissa muodostuu. Lisäksi työssä selvitettiin miten hajupäästöjä pystyttäisiin vähentämään. Työn kokeellisten tutkimusten aikana kerättiin tietoa hajun esiintymisestä valitulta tarkasteluajanjaksolta sekä mitattiin mm. tehtaan savukaasujen hajupitoisuutta ja koostumusta. Mittauksissa kaasunäytteiden hajupitoisuudeksi saatiin 170 HY/m3, joka kuvaa suhteellisen mietoa hajua. Näytteistä analysoidut haihtuvat orgaaniset yhdisteet olivat suurelta osin peräisin lasivillan valmistuksessa käytetystä sideaineesta, jota lisätään tuotteen joukkoon kuidutusvaiheessa. Ympäristöstä otetuista näytteistä ei kuitenkaan havaittu piipun yhdisteitä, mikä viittaisi siihen, että mittausjaksonaikana tehtaan päästöjen leviäminen ympäristöön on tapahtunut melko pieninä pitoisuuksina. Lisäksi on mahdollista, että ulkoilmassa yhdisteissä tapahtuu kemiallista muutuntaa ja hajontaa, jonka seurauksena yhdisteet muuttuvat. Tehtaan hajuhaitat vaikuttaisivat tutkimustulosten mukaan johtuvan savupainumaksi kutsutusta ilmiöstä. Savupainumaan vaikuttavat kaasun lämpömäärä sekä ympäristön olosuhteet ja topografia. Hajuhaittojen poistamiseksi olisi muodostuvia hajuyhdisteitä pystyttävä vähentämään 95-100 %.

Explosion-proof requirements for Electrical Machines in Chemical, Oil and Gas Industry in Russia and CIS Countries

One of the main industries which form the basis of Russian Economical structure is oil and gas. This industry is also playing a significant role for CIS countries. Oil and gas industry is developing intensively attracting foreign investments. This situation is providing sustainable development of machinery production for hazardous areas. Operating in oil and gas areas is always related with occurrence of explosion gas atmospheres. Machines for hazardous areas must be furnished with additional protection of different types. Explosion protection is regulated with standards according to which equipment must be manufactured. In Russia and CIS countries explosion-proof equipment must be constructed in compliance with GOST standards. To confirm that equipment is manufactured according to standards’ requirements and is safe and reliable it must undergo the approval procedure. Certification in Russia is governed by Federal Laws and legislation. Each CIS country has its own approval certificates and permissions for operating in hazardous areas.

Sustainable Waste-to-Energy Production: Performance Evaluation of Distributed Generation fuelled by Landfill Gas

The environmental impact of landfill is a growing concern in waste management practices. Thus, assessing the effectiveness of the solutions implemented to alter the issue is of importance. The objectives of the study were to provide an insight of landfill advantages, and to consolidate landfill gas importance among others alternative fuels. Finally, a case study examining the performances of energy production from a land disposal at Ylivieska was carried out to ascertain the viability of waste to energy project. Both qualitative and quantitative methods were applied. The study was conducted in two parts; the first was the review of literatures focused on landfill gas developments. Specific considerations were the conception of mechanism governing the variability of gas production and the investigation of mathematical models often used in landfill gas modeling. Furthermore, the analysis of two main distributed generation technologies used to generate energy from landfill was carried out. The review of literature revealed a high influence of waste segregation and high level of moisture content for waste stabilization process. It was found that the enhancement in accuracy for forecasting gas rate generation can be done with both mathematical modeling and field test measurements. The result of the case study mainly indicated the close dependence of the power output with the landfill gas quality and the fuel inlet pressure.

Separation of Gas Bubbles from Circulation Waters and Pulp Suspensions in Open Channel Flow

The objective of this thesis was to study the removal of gases from paper mill circulation waters experimentally and to provide data for CFD modeling. Flow and bubble size measurements were carried out in a laboratory scale open gas separation channel. Particle Image Velocimetry (PIV) technique was used to measure the gas and liquid flow fields, while bubble size measurements were conducted using digital imaging technique with back light illumination. Samples of paper machine waters as well as a model solution were used for the experiments. The PIV results show that the gas bubbles near the feed position have the tendency to escape from the circulation channel at a faster rate than those bubbles which are further away from the feed position. This was due to an increased rate of bubble coalescence as a result of the relatively larger bubbles near the feed position. Moreover, a close similarity between the measured slip velocities of the paper mill waters and that of literature values was obtained. It was found that due to dilution of paper mill waters, the observed average bubble size was considerably large as compared to the average bubble sizes in real industrial pulp suspension and circulation waters. Among the studied solutions, the model solution has the highest average drag coefficient value due to its relatively high viscosity. The results were compared to a 2D steady sate CFD simulation model. A standard Euler-Euler k-ε turbulence model was used in the simulations. The channel free surface was modeled as a degassing boundary. From the drag models used in the simulations, the Grace drag model gave velocity fields closest to the experimental values. In general, the results obtained from experiments and CFD simulations are in good qualitative agreement.

Dispersion of Hybrid Electromagnetic-Spin Waves in the Slotline

The presented thesis is devoted to investigation of wave processes in hybrid ferrite / ferroelectric structures. Spin wave devices based on ferrite films have such disadvantages, as huge size of the magnetic systems, low tuning velocity, considerable power inputs for parameters control that limits possible device applications. The considered layered structures allow to overcome the disadvantages mentioned and to promote the development of novel class of tunable microwave devices. The proposed theoretical analysis is intended to construct a model of hybrid electromagnetic-spin waves. Based on the theoretical analysis the experimental investigations were carried out. The experimental resonance characteristics of ferrite / ferroelectric resonator were obtained and their tunability by means of magnetic and electric field was demonstrated.

Cuticular and Suberin Polymers of Edible Plants. Analysis by Gas Chromatographic-Mass Spectrometric and Solid State Spectroscopic Methods

Cutin and suberin are structural and protective polymers of plant surfaces. The epidermal cells of the aerial parts of plants are covered with an extracellular cuticular layer, which consists of polyester cutin, highly resistant cutan, cuticular waxes and polysaccharides which link the layer to the epidermal cells. A similar protective layer is formed by a polyaromatic-polyaliphatic biopolymer suberin, which is present particularly in the cell walls of the phellem layer of periderm of the underground parts of plants (e.g. roots and tubers) and the bark of trees. In addition, suberization is also a major factor in wound healing and wound periderm formation regardless of the plants’ tissue. Knowledge of the composition and functions of cuticular and suberin polymers is important for understanding the physiological properties for the plants and for nutritional quality when these plants are consumed as foods. The aims of the practical work were to assess the chemical composition of cuticular polymers of several northern berries and seeds and suberin of two varieties of potatoes. Cutin and suberin were studied as isolated polymers and further after depolymerization as soluble monomers and solid residues. Chemical and enzymatic depolymerization techniques were compared and a new chemical depolymerization method was developed. Gas chromatographic analysis with mass spectrometric detection (GC-MS) was used to assess the monomer compositions. Polymer investigations were conducted with solid state carbon-13 cross polarization magic angle spinning nuclear magnetic resonance spectroscopy (13C CP-MAS NMR), Fourier transform infrared spectroscopy (FTIR) and microscopic analysis. Furthermore, the development of suberin over one year of post-harvest storage was investigated and the cuticular layers from berries grown in the North and South of Finland were compared. The results show that the amounts of isolated cuticular layers and cutin monomers, as well as monomeric compositions vary greatly between the berries. The monomer composition of seeds was found to differ from the corresponding berry peel monomers. The berry cutin monomers were composed mostly of long-chain aliphatic ω-hydroxy acids, with various mid-chain functionalities (double-bonds, epoxy, hydroxy and keto groups). Substituted α,ω-diacids predominated over ω-hydroxy acids in potato suberin monomers and slight differences were found between the varieties. The newly-developed closed tube chemical method was found to be suitable for cutin and suberin analysis and preferred over the solvent-consuming and laborious reflux method. Enzymatic hydrolysis with cutinase was less effective than chemical methanolysis and showed specificity towards α,ω-diacid bonds. According to ₁₃C CP-MAS NMR and FTIR, the depolymerization residues contained significant amounts of aromatic structures, polysaccharides and possible cutan-type aliphatic moieties. Cultivation location seems to have effect on cuticular composition. The materials studied contained significant amounts of different types of biopolymers that could be utilized for several purposes with or without further processing. The importance of the so-called waste material from industrial processes of berries and potatoes as a source of either dietary fiber or specialty chemicals should be further investigated in detail. The evident impact of cuticular and suberin polymers, among other fiber components, on human health should be investigated in clinical trials. These by-product materials may be used as value-added fiber fractions in the food industry and as raw materials for specialty chemicals such as lubricants and emulsifiers, or as building blocks for novel polymers.

Kinetic modeling of mechanisms of industrially important organic reactions in gas and liquid phase

This dissertation is based on 5 articles which deal with reaction mechanisms of the following selected industrially important organic reactions: 1. dehydrocyclization of n-butylbenzene to produce naphthalene 2. dehydrocyclization of 1-(p-tolyl)-2-methylbutane (MB) to produce 2,6-dimethylnaphthalene 3. esterification of neopentyl glycol (NPG) with different carboxylic acids to produce monoesters 4. skeletal isomerization of 1-pentene to produce 2-methyl-1-butene and 2-methyl-2-butene The results of initial- and integral-rate experiments of n-butylbenzene dehydrocyclization over selfmade chromia/alumina catalyst were applied when investigating reaction 2. Reaction 2 was performed using commercial chromia/alumina of different acidity, platina on silica and vanadium/calcium/alumina as catalysts. On all catalysts used for the dehydrocyclization, major reactions were fragmentation of MB and 1-(p-tolyl)-2-methylbutenes (MBes), dehydrogenation of MB, double bond transfer, hydrogenation and 1,6-cyclization of MBes. Minor reactions were 1,5-cyclization of MBes and methyl group fragmentation of 1,6- cyclization products. Esterification reactions of NPG were performed using three different carboxylic acids: propionic, isobutyric and 2-ethylhexanoic acid. Commercial heterogeneous gellular (Dowex 50WX2), macroreticular (Amberlyst 15) type resins and homogeneous para-toluene sulfonic acid were used as catalysts. At first NPG reacted with carboxylic acids to form corresponding monoester and water. Then monoester esterified with carboxylic acid to form corresponding diester. In disproportionation reaction two monoester molecules formed NPG and corresponding diester. All these three reactions can attain equilibrium. Concerning esterification, water was removed from the reactor in order to prevent backward reaction. Skeletal isomerization experiments of 1-pentene were performed over HZSM-22 catalyst. Isomerization reactions of three different kind were detected: double bond, cis-trans and skeletal isomerization. Minor side reaction were dimerization and fragmentation. Monomolecular and bimolecular reaction mechanisms for skeletal isomerization explained experimental results almost equally well. Pseudohomogeneous kinetic parameters of reactions 1 and 2 were estimated by usual least squares fitting. Concerning reactions 3 and 4 kinetic parameters were estimated by the leastsquares method, but also the possible cross-correlation and identifiability of parameters were determined using Markov chain Monte Carlo (MCMC) method. Finally using MCMC method, the estimation of model parameters and predictions were performed according to the Bayesian paradigm. According to the fitting results suggested reaction mechanisms explained experimental results rather well. When the possible cross-correlation and identifiability of parameters (Reactions 3 and 4) were determined using MCMC method, the parameters identified well, and no pathological cross-correlation could be seen between any parameter pair.

Reactive dissolution of sedimentary rocks in flue gas desulfurization : modeling and experimental investigation

Svavel förekommer i kol och olja och oxideras vid förbränning till svaveldioxid (SO2). Årligen utsläpps stora mängder svaveldioxid som åstadkommer sura regn, minskning av stratosfäriskt ozon och sjukdomar. Av dessa orsaker är det nödvändigt att minska utsläppen av svaveldioxid. Den teknologi som rör planering av reaktorer och processer för rökgasavsvavling (FGD) har utvecklats kraftigt och idag använder man olika typer av lösningar. De vanligaste alternativen för FGD är våtskrubber- och semitorra skrubbersystem (Spray Dry Scrubbers, SDS) och injektionsprocesser för absorbenter. SDS-processer har studerats bland annat av Ahlbeck [4] och Klingspor [5] och injektionsprocesser av Alvfors [6]. Kalksten, som i huvusak består av kalciumkarbonat, används i rökgasavsvavling på grund av sin förmåga att binda svavel i form av sulfatsalter. Den vanligaste rökgasavsvavlingsmetoden är våtskrubbning, där det sedimentära stenmaterialets upplösningshastighet är en av de faktorer som påverkar resultatet mest. Utvärdering av kalkstensreaktivitet är därför speciellt viktig vid planering och drift av anläggningar för rökgasavsvavling. Målsättningen med detta arbete var att modellera upplösningen av olika typers kalksten för att få en kvantitativ utvärdering av kvaliteten på de analyserade proverna. Därtill testades även karbonatbiprodukter från stålindustrin för att utvärdera möjligheter att använda andra råmaterial. Det transienta förloppet har analyserats, varvid upplösningshastigheten modellerades bl.a. i avseende på tid och pH. Under arbetets gång har antalet empiriska korrelationer minskats till fördel för fysikaliska modeller av diffusiva och konvektiva masstransportfenomen. En målsättning var att skapa en effektiv och snabb metod för att testa olika absorbenter för rökgasavsvavling under transienta förlopp. I arbetet användes PSD-analys, gjordes pH-mätningar och andra utvärderingar av de fysikaliska parametrar som ingår i beräkningarna. On-line mätningar för de icke-stationära variablerna tid och pH ger möjlighet att eliminera osäkerheter. Vissa modeller kan vara komplicerade. En modell för upplösningshastigheten med mer detaljerad utvärdering av parametrar och färre approximationer är därför nödvändig då man vill utvärdera reaktionshastigheten för fasta partiklar i sur miljö. Arbetet utfördes under fyra år och fem peer review-artiklar ingår i avhandlingen.

Happidispersion karakterisointi laboratoriosekoittimessa

Työn tarkoituksena oli tarkastella uutta kuvantamistekniikkaa käyttäen happikaasun dispergointia keskisakeuksisen massasuspension joukkoon laboratoriosekoittimessa. Työssä pyrittiin tarkastelemaan muodostuvan dispersion homogeenisuutta neljästä eri kuvauspisteestä sekoittimen kannesta ja kyljestä. Samalla tarkasteltiin myös sekoittimen tehonkulutusta sekä tehonkulutuksen ja aikaansaadun dispersion välistä yhteyttä. Työn yhtenä tarkoituksena oli myös tarkastella uuden kuvantamistekniikan mahdollisuuksia tämäntyyppisissä sovellutuksissa, sillä työ kuuluu PulpVision-projektiin, jossa kehitetään massa- ja paperiteollisuuden uusia konenäkösovellutuksia. Työn kokeellinen osuus koostui sekoituskokeista, joissa tarkasteltiin neljästä kuvauspisteestä kahdella sekoittimen nopeudella mänty- ja koivususpensioihin muodostuvaa kuplakokojakaumaa. Sekoituskokeiden lisäksi tehtiin tehonkulutuskokeita, joissa tarkasteltiin sekoittimen tehonkulutusta sekoittimen täyttöasteen funktiona koivu- ja mäntysuspensioilla sekä vedellä. Työn tuloksien perusteella todettiin, että koivususpensiosta havaittujen kuplien pinta-ala oli noin puolet mäntysuspensiosta havaittujen kuplien pinta-alasta. Sekoittimen roottorin pyörimisnopeuden puolittuessa suspensioon dispergoidun hapen kuplakoko kasvoi huomattavasti. Neljästä kuvausyhteestä tarkasteltuna havaittiin pienimpien kuplien esiintyvän sekoittimen alaosassa. Mäntysuspension tehonkulutuksen havaittiin kasvavan viidenneksellä, kun sekoittimen täyttöaste kasvoi 10 %, kun taas koivususpension tehonkulutuksen kasvu oli tästä vain puolet. Kuvantamislaitteiston todettiin olevan tämänkaltaiseen sovellutukseen riittävä, varsinkin kun valonlähteenä käytetään pulssilaseria.

Kaasun dispergoituminen tehdasmittakaavaisessa keskisakean massan sekoittimessa

Työn tarkoituksena oli selvittää Proto 10 kemikaalisekoittimen kyky dispergoida kaasua keskisakean valkaistun mäntysellun joukkoon. Työssä käytettiin kuvantamistekniikkaa, jonka avulla pystyttiin näkemään sekoittimen ja putkiston sisälle sekoitustapahtuman aikana. Muodostunutta dispersiota tarkasteltiin kolmesta kuvauspisteestä, joista yksi sijaitsi sekoittimen pesässä ja kaksi putkistossa sekoittimen jälkeen. Työssä verrattiin myös laboratoriosekoittimella saatuja tuloksia teollisen mittakaavan sekoittimella saatuihin tuloksiin, sekä määritettiin tarvittava pinta-aktiivisen aineen konsentraatio, jolla saavutettiin ruskeaa massaa vastaava vaahtoaminen. Työn kokeellinen osuus koostui kolmesta osasta. Ensimmäisessä vaiheessa tutkittiin ruskeasta mänty- ja koivumassasta lingotun suodoksen vaahtoamista ja verrattiin sitä vedellä ja pesuaineella saatavaan vaahtoon. Toisessa vaiheessa suoritettiin referenssiajot laboratoriosekoittimen ja teollisen mittakaavan sekoittimen vertailua varten Quantum Mark IV laboratoriosekoittimella. Kolmannessa vaiheessa tutkittiin Proto 10 sekoittimen kykyä dispergoida kaasua mäntysellun joukkoon eri pyörimisnopeuksilla ja virtaamilla. Työn tuloksien perusteella energiankäytön kannalta paras pyörimisnopeus Proto 10 sekoittimelle on 1500 min-1. Nostamalla kierrosnopeutta yli tämän ei saavutettu merkittävää parannusta dispersion laadussa varsinkaan suuremmilla virtaamilla. Virtaamalla todettiin olevan suuri merkitys sekoitustulokseen. Laboratoriosekoittimella tehtyjen kokeiden todettiin vastaavan parhaiten teollisen mittakaavan tuloksia pyörimisnopeudella 1200 min-1.