Effects of Surface Properties and Wood Modification into Direct Printing on Wood

Building industry is a high volume branch which could provide prominent markets for wood based interior decoration solutions. Competition in interior decoration markets requires versatility in appearance. Versatility in wood appearance and added value could be achieved by printing grain patterns of different species or images directly onto wood. The problem when planning wood printing’s implementing into durable applications is basically how to transfer a high quality image or print sustainably onto wood, which is porous, heterogeneous, dimensionally unstable, non-white and rough. Wood preservation or treating, and modification can provide durability against degradation but also effect to the surface properties of wood which will effect on printability. Optimal adhesion is essential into print quality, as too high ink absorbance can cause spreading and too low ink absorbance cause pale prints. Different printing techniques have different requirements on materials and production. The direct printing on wood means, that intermedias are not used. Printing techniques with flexible printing plates or in fact non-impact techniques provide the best basis for wood printing. Inkjet printing of wood with different mechanical or chemical surface treatments, and wood plastic composite material gave good results that encourage further studies of the subject. Sanding the wood surface anti-parallel to the grain gave the best overall printing quality. Spreading parallel to the grain could not be avoided totally, except in cases where wood was treated hydrophobic so adhesion of the ink was not sufficient. Grain pattern of the underlying wood stays clearly visible in the printed images. Further studies should be made to fine tune the methods that already gave good results. Also effects of moisture content of wood, different inks, and long-term exposure to UV-radiation should be tested.

Role of oxidation-reduction cycle of iron in direct leaching of zinc concentrate

Direct leaching is an alternative to conventional roast-leach-electrowin (RLE) zinc production method. The basic reaction of direct leach method is the oxidation of sphalerite concentrate in acidic liquid by ferric iron. The reaction mechanism and kinetics, mass transfer and current modifications of zinc concentrate direct leaching process are considered. Particular attention is paid to the oxidation-reduction cycle of iron and its role in direct leaching of zinc concentrate, since it can be one of the limiting factors of the leaching process under certain conditions. The oxidation-reduction cycle of iron was experimentally studied with goal of gaining new knowledge for developing the direct leaching of zinc concentrate. In order to obtain this aim, ferrous iron oxidation experiments were carried out. Affect of such parameters as temperature, pressure, sulfuric acid concentration, ferrous iron and copper concentrations was studied. Based on the experimental results, mathematical model of the ferrous iron oxidation rate was developed. According to results obtained during the study, the reaction rate orders for ferrous iron concentration, oxygen concentration and copper concentration are 0.777, 0.652 and 0.0951 respectively. Values predicted by model were in good concordance with the experimental results. The reliability of estimated parameters was evaluated by MCMC analysis which showed good parameters reliability.

Simulation of hydrogen peroxide direct synthesis in a microreactor

A set of models in Aspen plus was built to simulate the direct synthesis process of hydrogen peroxide in a micro-reactor system. This process model can be used to carry out material balance calculation under various experimental conditions. Three thermodynamic property methods were compared by calculating gas solubility and Uniquac-RK method was finally selected for process model. Two different operation modes with corresponding operation conditions were proposed as the starting point of future experiments. Simulations for these two modes were carried out to get the information of material streams. Moreover, some hydrodynamic parameters such as gas/liquid superficial velocity, gas holdup were also calculated with improved process model. These parameters proved the proposed experimental conditions reasonable to some extent. The influence of operation conditions including temperature, pressure and circulation ratio was analyzed for the first operation mode, where pure oxygen was fed into dissolving tank and hydrogen-carbon dioxide mixture was fed into microreactor directly. The preferred operation conditions for the system are low temperature (2°C) and high pressure (30 bar) in dissolving tank. High circulation ratio might be good in the sense that more oxygen could be dissolved and fed into reactor for reactions, but meanwhile hydrodynamics of microreactor should be considered. Furthermore, more operation conditions of reactor gas/liquid feeds in both of two operation modes were proposed to provide guidance for future experiment design and corresponding hydrodynamic parameters were also calculated. Finally, safety issue was considered from thermodynamic point of view and there is no explosion danger at given experimental plan since the released reaction heat will not cause solvent vaporization inside the microchannels. The improvement of process model still needs further study based on the future experimental results.

Safety study of hydrogen peroxide direct synthesis

Kandidaatintyön johdantokappaleessa esitellään vetyperoksidi ja mihin sitä käytetään teollisuudessa. Työssä vertaillaan antrakinoniprosessia ja suoraa prosessia sekä selvitetään nykyisin enemmän vetyperoksidituotantoon käytetyn antrakinoniprosessin ongelmakohdat ja osoitetaan, miksi suora synteesi vetyperoksidin tuotannossa olisi parempi vaihtoehto. Kandidaatintyön käsittelee suurilta osin turvallisuusongelmia, joita esiintyy suoran synteesin yhteydessä. Kirjallisuudesta on etsitty ratkaisuja näihin ongelmiin, kuten membraaniprosessin käyttöä räjähdysvaaran välttämiseksi. Pienemmän reaktorin eli ns. mikroreaktorin käyttö tuo mukanaan monia etuja vetyperoksidin tuotantoon. Tällöin prosessi on turvallisempi ja sitä on helpompi hallita. Mikroreaktorissa voidaan käyttää korkeampia lämpötiloja ja paineita kuin makroreaktorilla ilman, että räjähdysvaara prosessissa kasvaisi. Mikroreaktorin sisällä olevat mikrokanavat luovat turvallisen ympäristön synteesille. Aspen plus – simulointiohjelmalla mallinnettiin ja simulointiin suoran prosessin kriittisiä virtoja mikroreaktorissa. Tarkoituksena oli löytää virrat, joissa kulkee mahdollisesti räjähtävä kaasuseos. Kaasumaiset prosessivirrat ovat kriittisimmät vetyperoksidin suorassa synteesissä, koska ne aiheuttavat todennäköisemmin räjähdyksen kuin nestemäiset prosessivirrat. Kaikkein eniten prosessiturvallisuutta uhkaavat ainevirrat ennen ja jälkeen mikroreaktoria.

Kuivatusmenetelmien vaikutus heatset offset- ja syväpainetun SC-paperin laatuun

Työssä tutkittiin heatset offset- ja syväpainetun SC-paperin painojäljen laatua, kun koepaperikoneella valmistetun SC-paperin valmistuksessa käytettiin eri kuivatus-menetelmiä. Erityisesti kiinnostus kohdistui eri kuiva-ainepitoisuuksissa käytetyn ilmakuivatuksen aiheuttamiin painojäljen laatuvaikutuksiin. Painojäljen lisäksi työssä tarkasteltiin pohjapaperin ominaisuuksia kuivatuksen jakalanteroinnin jälkeen. Perinteisen sylinterikuivatuksen kuivatuskapasiteettia voidaan nostaa kuivattamalla paperia kuuman ilman avulla, jolloin paperin haihdutusnopeus nousee yli viisinkertaiseksi sylinterikuivatukseenverrattuna. Ilmakuivatus voidaan sijoittaa välittömästä kuivatusosan alkuun ennen ensimmäistä kuivatussylinteriä tai korkeampaan kuiva-ainepitoisuuteen sylinterikuivatuksen keskelle. Kuivattua paperia tarkasteltaessa kuuman ilman avulla kuivatun paperin ominaisuudet poikkesivat huokoisuuden ja öljynabsorption suhteen sylinterikuivatusta paperista sekä heatset offset- että syväpainopaperilla. Kalanterointi tasoitti koepisteiden välisiä muutoksia. Kalanteroidusta paperista havaittiin, että ilmakuivatuksen sijoittuminen välittömästi puristimen jälkeen kasvatti paperin molempien pintojen opasiteettia. Vastaavasti paperin tiheys kasvoi, kun paperia kuivattiin kuumalla ilmalla sekä ennen sylinterikuivatusta että sylinterikuivatuksen keskellä. Yhteistä ilmakuivatuksen käytölle kaikissa koepisteissä oli paperin huokoisuuden pieneneminen. Heatset offsetpainoprosessissa käytettävä kostutusvesi asettaa paperin kuitu-karhenemiselle vaatimuksia. Tutkimuksessa havaittiin, että puristimen jälkeen sijoitettu ilmakuivatus pienensi paperin taipumusta karhentua painoprosessissa. Muiden ominaisuuksien osalta paperin kuivatus kuuman ilman avulla yhdessä sylinterikuivatuksen kanssa ei jättänyt paperiin sellaisia jälkiä, jotka näkyisivät heatset offset- ja syväpainetun SC-paperin painojäljessä verrattuna kokonaan yksiviira-vientisesti sylinterikuivattuun paperiin.

Elintarvikekelpoisten painovärien vertailu offsetpainatuksessa

Tässä diplomityössä tutkittiin kolmen eri painovärivalmistajan elintarvikekelpoisia arkkioffsetpainovärisarjoja ja verrattiin niitä keskenään. Tavoitteena oli löytää optimaalinen elintarvikekartonkipakkausten painamiseen soveltuva arkkioffsetpainoväri. Työn kirjallisessa osassa selvitettiin yleisesti offsetpainatusprosessia, painovärien koostumusta ja elintarvikekelpoisten painovärien eroavaisuutta verrattuna perinteisiin offsetpainoväreihin. Kirjallisuusosassa tuotiin esille myös niitä tekijöitä, joilla elintarvikekelpoisuus määritellään. Näistä yksi tärkeä osa-alue on migraatio-ongelmat, joka on lainsäädännön kannalta ajankohtainen. Kokeellista osaa varten koepainovärejä painettiin taivekartongille arkkioffsetpainokoneella. Painetuista arkeista tehtiin mittauksia, joissa käytettiin densitometrisia, kolorimetrisia, kromatografisia ja aistinvaraisia menetelmiä. Näillä pyrittiin tuomaan esille eroavaisuuksia tutkittavana olleiden painovärien välille. Koeajojen ja mittausten perusteella analysoitiin painatuksen laatua, painettavuutta, painovärien elintarvikekelpoisuutta ja kestävyyttä. Työn tulosten perusteella ei voida suoraan osoittaa, että jokin painovärisarja olisi toimivampi kuin toinen. Yksi johtopäätös olikin, että painovärien koostumusta ja painatusprosessia on mahdollista modifioida monella tavalla, jolloin voidaan parantaa joitakin painovärin ominaisuuksia. Yleisesti kokeet osoittivat, että perinteinen aistinvarainen tapa testata painovärin elintarvikekelpoisuutta on hyvin subjektiivinen ja antaa arveluttavia tuloksia. Koetuloksista oli kuitenkin havaittavissa, että uuden sukupolven vähemmän migraatiota aiheuttavat painovärit ovat elintarvikekelpoisempia kuin aikaisempien kehitysasteiden painovärisarjat.

Improvement of Surface Strength of Paper

Offset printing is a popular printing method that is especially suitable for large and fast print jobs. Newspapers, magazines and books are typical examples of products printed with offset method. In high volume printing production high efficiency is essential. Offset printing uses tacky inks that cause serious stress to the paper surface. Dusting and linting are terms that describe how loose and weakly bonded particles are removed from the paper surface in the printing process. The removed particles accumulate in the process causing deteriorating print quality. This forces the printing operators to stop production for washing and cleaning. Time and money are lost. Dusting and linting tendency of paper can be decreased by improving the surface strength of paper. In the present work a method to increase the surface strength of paper was studied. In the literature part offset printing method and challenges related to offset printing are presented. A review of new methods for surface sizing of paper is also presented. The experimental part presents trials where an apparatus for improving paper surface strength was tested and developed in mill scale. Laboratory work supporting the actual mill scale operations is also presented. The acquired results provide a solid base of information to make decisions on how to proceed with research in the present field of study.

Studies in offset ink setting

The offset printing process is complex and involves the meeting of two essentially complex materials, printing ink and paper, upon which the final product is formed. It can therefore be expected that a multitude of chemical and physical interactions and mechanisms take place at the ink-paper interface. Interactions between ink and paper are of interest to both the papermakers and ink producers, as they wish to achieve better quality in the final product. The objective of this work is to clarify the combined influence of paper coating structure, printing ink and fountain solution on ink setting and the problems related to ink setting. A further aim is to identify the mechanisms that influence ink setting problems, and to be able to counteract them by changing properties of the coating layer or by changing the properties of the ink. The work carried out for this thesis included use of many techniques ranging from standard paper and printability tests to advanced optical techniques for detection of ink filaments during ink levelling. Modern imaging methods were applied for assessment of ink filament remain sizes and distribution of ink components inside pigment coating layers. Gravimetric filtration method and assessment of print rub using Ink-Surface-Interaction-Tester (ISIT) were utilized to study the influence of ink properties on ink setting. The chemical interactions were observed with the help of modified thin layer chromatography and contact angle measurements using both conventional and high speed imaging. The results of the papers in this thesis link the press operational parameters to filament sizes and show the influence of these parameters to filament size distribution. The relative importance between the press operation parameters was shown to vary. The size distribution of filaments is important in predicting the ink setting behaviour, which was highlighted by the dynamic gloss and ink setting studies. Prediction of ink setting behaviour was also further improved by use of separate permeability factors for different ink types in connection to filtration equations. The roles of ink components were studied in connection to ink absorption and mechanism of print rub. Total solids content and ratio of linseed oil to mineral oil were found to determine the degree of print rub on coated papers. Wax addition improved print rub resistance, but would not decrease print rub as much as lowering the total solids content in the ink. Linseed oil was shown to absorb into pigment coating pores by mechanism of adsorption to pore walls, which highlights the need for sufficient pore surface area for improved chromatographic separation of ink components. These results should help press operators, suppliers of printing presses, papermakers and suppliers to papermakers, to better understand the material and operating conditions of the press as it relates to various print quality issues. Even though paper is in competition with electronic media, high quality printed products are still in demand. The results should provide useful information for this segment of the industry.

Printed low-voltage organic transistors on plastics and paper

The main advantage of organic electronics over the more widespread inorganic counterparts lies not in the electrical performance, but rather in the solution processability that opens up for low-cost flexible electronics (e.g. displays, sensors and smart tags) fabricated by using printing techniques. Replacing the commonly used laboratory-scale fabrication techniques with mass-printing techniques is, however, truly challenging, especially when low-voltage operation is required. In this thesis it is, nevertheless, demonstrated that low-voltage organic transistors can be fully printed with a similar performance to that of transistors made by laboratory scale techniques. The use of an ion-modulated type of organic field effect transistor (OFET) not only enabled low-voltage operation and printability, but was also found to result in low sensitivity to the surface roughness of the substrate. This allows not only the use of low-cost plastic substrates, but even the use of paper as a substrate. However, while absorption into the porous paper surface is advantageous in a graphical printing process, by reducing the spreading and the coffee-stain effect and by improving the adhesion, it provides great challenges when applying thin electrically active layers. In spite of these difficulties we were able to demonstrate the first low-voltage OFET to be fabricated on paper. We have also shown that low-cost incandescent lamps can be used for sintering printed metal-nanoparticles, and that the process was especially suitable on paper and compatible with a roll-to-roll manufacturing process.

Paper for printed electronics and functionality

Mass-produced paper electronics (large area organic printed electronics on paper-based substrates, “throw-away electronics”) has the potential to introduce the use of flexible electronic applications in everyday life. While paper manufacturing and printing have a long history, they were not developed with electronic applications in mind. Modifications to paper substrates and printing processes are required in order to obtain working electronic devices. This should be done while maintaining the high throughput of conventional printing techniques and the low cost and recyclability of paper. An understanding of the interactions between the functional materials, the printing process and the substrate are required for successful manufacturing of advanced devices on paper. Based on the understanding, a recyclable, multilayer-coated paper-based substrate that combines adequate barrier and printability properties for printed electronics and sensor applications was developed in this work. In this multilayer structure, a thin top-coating consisting of mineral pigments is coated on top of a dispersion-coated barrier layer. The top-coating provides well-controlled sorption properties through controlled thickness and porosity, thus enabling optimizing the printability of functional materials. The penetration of ink solvents and functional materials stops at the barrier layer, which not only improves the performance of the functional material but also eliminates potential fiber swelling and de-bonding that can occur when the solvents are allowed to penetrate into the base paper. The multi-layer coated paper under consideration in the current work consists of a pre-coating and a smoothing layer on which the barrier layer is deposited. Coated fine paper may also be used directly as basepaper, ensuring a smooth base for the barrier layer. The top layer is thin and smooth consisting of mineral pigments such as kaolin, precipitated calcium carbonate, silica or blends of these. All the materials in the coating structure have been chosen in order to maintain the recyclability and sustainability of the substrate. The substrate can be coated in steps, sequentially layer by layer, which requires detailed understanding and tuning of the wetting properties and topography of the barrier layer versus the surface tension of the top-coating. A cost competitive method for industrial scale production is the curtain coating technique allowing extremely thin top-coatings to be applied simultaneously with a closed and sealed barrier layer. The understanding of the interactions between functional materials formulated and applied on paper as inks, makes it possible to create a paper-based substrate that can be used to manufacture printed electronics-based devices and sensors on paper. The multitude of functional materials and their complex interactions make it challenging to draw general conclusions in this topic area. Inevitably, the results become partially specific to the device chosen and the materials needed in its manufacturing. Based on the results, it is clear that for inks based on dissolved or small size functional materials, a barrier layer is beneficial and ensures the functionality of the printed material in a device. The required active barrier life time depends on the solvents or analytes used and their volatility. High aspect ratio mineral pigments, which create tortuous pathways and physical barriers within the barrier layer limit the penetration of solvents used in functional inks. The surface pore volume and pore size can be optimized for a given printing process and ink through a choice of pigment type and coating layer thickness. However, when manufacturing multilayer functional devices, such as transistors, which consist of several printed layers, compromises have to be made. E.g., while a thick and porous top-coating is preferable for printing of source and drain electrodes with a silver particle ink, a thinner and less absorbing surface is required to form a functional semiconducting layer. With the multilayer coating structure concept developed in this work, it was possible to make the paper substrate suitable for printed functionality. The possibility of printing functional devices, such as transistors, sensors and pixels in a roll-to-roll process on paper is demonstrated which may enable introducing paper for use in disposable “onetime use” or “throwaway” electronics and sensors, such as lab-on-strip devices for various analyses, consumer packages equipped with product quality sensors or remote tracking devices.

Towards sustainable Iron- and steelmaking with economic optimization

The iron and steelmaking industry is among the major contributors to the anthropogenic emissions of carbon dioxide in the world. The rising levels of CO2 in the atmosphere and the global concern about the greenhouse effect and climate change have brought about considerable investigations on how to reduce the energy intensity and CO2 emissions of this industrial sector. In this thesis the problem is tackled by mathematical modeling and optimization using three different approaches. The possibility to use biomass in the integrated steel plant, particularly as an auxiliary reductant in the blast furnace, is investigated. By pre-processing the biomass its heating value and carbon content can be increased at the same time as the oxygen content is decreased. As the compression strength of the preprocessed biomass is lower than that of coke, it is not suitable for replacing a major part of the coke in the blast furnace burden. Therefore the biomass is assumed to be injected at the tuyere level of the blast furnace. Carbon capture and storage is, nowadays, mostly associated with power plants but it can also be used to reduce the CO2 emissions of an integrated steel plant. In the case of a blast furnace, the effect of CCS can be further increased by recycling the carbon dioxide stripped top gas back into the process. However, this affects the economy of the integrated steel plant, as the amount of top gases available, e.g., for power and heat production is decreased. High quality raw materials are a prerequisite for smooth blast furnace operation. High quality coal is especially needed to produce coke with sufficient properties to ensure proper gas permeability and smooth burden descent. Lower quality coals as well as natural gas, which some countries have in great volumes, can be utilized with various direct and smelting reduction processes. The DRI produced with a direct reduction process can be utilized as a feed material for blast furnace, basic oxygen furnace or electric arc furnace. The liquid hot metal from a smelting reduction process can in turn be used in basic oxygen furnace or electric arc furnace. The unit sizes and investment costs of an alternative ironmaking process are also lower than those of a blast furnace. In this study, the economy of an integrated steel plant is investigated by simulation and optimization. The studied system consists of linearly described unit processes from coke plant to steel making units, with a more detailed thermodynamical model of the blast furnace. The results from the blast furnace operation with biomass injection revealed the importance of proper pre-processing of the raw biomass as the composition of the biomass as well as the heating value and the yield are all affected by the pyrolysis temperature. As for recycling of CO2 stripped blast furnace top gas, substantial reductions in the emission rates are achieved if the stripped CO2 can be stored. However, the optimal recycling degree together with other operation conditions is heavily dependent on the cost structure of CO2 emissions and stripping/storage. The economical feasibility related to the use of DRI in the blast furnace depends on the price ratio between the DRI pellets and the BF pellets. The high amount of energy needed in the rotary hearth furnace to reduce the iron ore leads to increased CO2 emissions.

3D-tulostettu tuuliturbiinin vaihteen pienoismalli

Työn aiheena on vaihteen pienoismallin suunnittelu ja toteutus 3d-tulostusta hyväksi käyttäen. Pienoismalli tehdään Moventas Gears Oy:n suunnittelemasta tuuliturbiinin vaihteesta. Vaihteen pienentämisestä johtuen malliin on suunniteltava uudet laakeripesät ja hammaspyörät. 3D-tulostuksen ja pienoismallin pienen koon ansiosta vaihdetta voidaan yksinkertaistaa suuresti ja näin vähentää tulostettavien osien määrää. Lisäksi työssä selvitetään, mitä ongelmia 3D-tulostus tuo valmistukseen ja suunnitteluun. Työn kirjallisessa osassa selvennetään planeettavaihteen toimintaa yleisesti sekä esitellään Exceed Series 3+ vaihdetta. Lisäksi kerrotaan 3D-tulostuksesta, sen periaatteesta, erilaisista tulostusmenetelmistä, tulostinlaitteesta ja mahdollisista ongelmista tulostuksessa. Kokeellinen osa koostuu pienoismallin suunnittelusta ja valmistuksesta. Valmistuksessa olleiden virheiden takia muutama osa jouduttiin tulostamaan uudelleen. Muutamia osia jouduttiin myös hieman jälkikäsittelemään tulostuksen jälkeen, jotta malli saatiin kasattua. Ongelmakohdaksi muodostui tulostimen ohjelmisto ja tulostustiedostot. Tulostusprosessi sujui kuitenkin hyvin. Lopputuloksena saatiin toimiva pienoismalli. 3D-tulostus toimii hyvin monimutkaisten kappaleiden tulostuksessa. Tulostuksen hinta nousi kuitenkin varsin korkeaksi. Tulostuslaitteistosta riippuen tulostuksen voisi mahdollisesti suorittaa myös halvemmallakin.

Näin opetan lisäävää valmistusta ja 3D-tulostusta: Pohdintoja uuden teknologian opetuksesta ja koulutuksesta

Additive manufacturing (shortened as AM), or more commonly 3D printing, consists of wide variety of different modern manufacturing technologies. AM is based on direct printing of a digital 3D model to a final product which is fabricated adding material layer by layer. This is from where term additive manufacturing has its origin. It is not only material what is added, but it is also value, properties etc. which are added. AM enables production of different and even better products compared to conventional manufacturing technologies. An estimation of potential of additive manufacturing can be gathered by considering the potential of laser cutting, which is one of the most widely used modern manufacturing technologies. This technique has been used over 40 years, and whole market around this technology is at the moment c. four billion euros and yearly growth is around 10 %. One factor affecting this success of laser cutting is that laser cutting enables radical improvements to products made of flat sheet. AM and 3D printing will do the same for three dimensional parts. Laser devices, which are at the moment used in 3D printing, are globally at the moment only around 1% of all laser devices used in any fabrication technology, so even with a cautious estimate the potential growth of at least 100 % is coming in next few years. Role of education is very important, when this kind of modern technology is industrially implemented. When both generation entering to work life and also generation who has been a while in work life understands new technology, its potential and limitations, this is the point when also product design can be rethought Potential of product design is driving force for wide use of additive manufacturing and 3D printing. Utilization of additive manufacturing and 3D printing is also opportunity for Finland and Finnish industry. This technology can save Finnish manufacturing industry. This technique has stron potential, as Finland has traditionally strong industrial know-how and good ICT knowledge.

Liquid transportation and distribution during (re)wetting : impact on coated papers in printing

In many industrial applications, such as the printing and coatings industry, wetting of porous materials by liquids includes not only imbibition and permeation into the bulk but also surface spreading and evaporation. By understanding these phenomena, valuable information can be obtained for improved process control, runnability and printability, in which liquid penetration and subsequent drying play important quality and economic roles. Knowledge of the position of the wetting front and the distribution/degree of pore filling within the structure is crucial in describing the transport phenomena involved. Although exemplifying paper as a porous medium in this work, the generalisation to dynamic liquid transfer onto a surface, including permeation and imbibition into porous media, is of importance to many industrial and naturally occurring environmental processes. This thesis explains the phenomena in the field of heatset web offset printing but the content and the analyses are applicable in many other printing methods and also other technologies where water/moisture monitoring is crucial in order to have a stable process and achieve high quality end products. The use of near-infrared technology to study the water and moisture response of porous pigmented structures is presented. The use of sensitive surface chemical and structural analysis, as well as the internal structure investigation of a porous structure, to inspect liquid wetting and distribution, complements the information obtained by spectroscopic techniques. Strong emphasis has been put on the scale of measurement, to filter irrelevant information and to understand the relationship between interactions involved. The near-infrared spectroscopic technique, presented here, samples directly the changes in signal absorbance and its variation in the process at multiple locations in a print production line. The in-line non-contact measurements are facilitated by using several diffuse reflectance probes, giving the absolute water/moisture content from a defined position in the dynamic process in real-time. The nearinfrared measurement data illustrate the changes in moisture content as the paper is passing through the printing nips and dryer, respectively, and the analysis of the mechanisms involved highlight the roles of the contacting surfaces and the relative liquid carrier properties of both non-image and printed image areas. The thesis includes laboratory studies on wetting of porous media in the form of coated paper and compressed pigment tablets by mono-, dual-, and multi-component liquids, and paper water/moisture content analysis in both offline and online conditions, thus also enabling direct sampling of temporal water/moisture profiles from multiple locations. One main focus in this thesis was to establish a measurement system which is able to monitor rapid changes in moisture content of paper. The study suggests that near-infrared diffuse reflectance spectroscopy can be used as a moisture sensitive system and to provide accurate online qualitative indicators, but, also, when accurately calibrated, can provide quantification of water/moisture levels, its distribution and dynamic liquid transfer. Due to the high sensitivity, samples can be measured with excellent reproducibility and good signal to noise ratio. Another focus of this thesis was on the evolution of the moisture content, i.e. changes in moisture content referred to (re)wetting, and liquid distribution during printing of coated paper. The study confirmed different wetting phases together with the factors affecting each phase both for a single droplet and a liquid film applied on a porous substrate. For a single droplet, initial capillary driven imbibition is followed by equilibrium pore filling and liquid retreat by evaporation. In the case of a liquid film applied on paper, the controlling factors defining the transportation were concluded to be the applied liquid volume in relation to surface roughness, capillarity and permeability of the coating giving the liquid uptake capacity. The printing trials confirmed moisture gradients in the printed sheet depending on process parameters such as speed, fountain solution dosage and drying conditions as well as the printed layout itself. Uneven moisture distribution in the printed sheet was identified to be one of the sources for waving appearance and the magnitude of waving was influenced by the drying conditions.

Development of a process for the direct synthesis of hydrogen peroxide in a novel microstructured reactor

Microreactors have proven to be versatile tools for process intensification. Over recent decades, they have increasingly been used for product and process development in chemical industries. Enhanced heat and mass transfer in the reactors due to the extremely high surfacearea- to-volume ratio and interfacial area allow chemical processes to be operated at extreme conditions. Safety is improved by the small holdup volume of the reactors and effective control of pressure and temperature. Hydrogen peroxide is a powerful green oxidant that is used in a wide range of industries. Reduction and auto-oxidation of anthraquinones is currently the main process for hydrogen peroxide production. Direct synthesis is a green alternative and has potential for on-site production. However, there are two limitations: safety concerns because of the explosive gas mixture produced and low selectivity of the process. The aim of this thesis was to develop a process for direct synthesis of hydrogen peroxide utilizing microreactor technology. Experimental and numerical approaches were applied for development of the microreactor. Development of a novel microreactor was commenced by studying the hydrodynamics and mass transfer in prototype microreactor plates. The prototypes were designed and fabricated with the assistance of CFD modeling to optimize the shape and size of the microstructure. Empirical correlations for the mass transfer coefficient were derived. The pressure drop in micro T-mixers was investigated experimentally and numerically. Correlations describing the friction factor for different flow regimes were developed and predicted values were in good agreement with experimental results. Experimental studies were conducted to develop a highly active and selective catalyst with a proper form for the microreactor. Pd catalysts supported on activated carbon cloths were prepared by different treatments during the catalyst preparation. A variety of characterization methods were used for catalyst investigation. The surface chemistry of the support and the oxidation state of the metallic phase in the catalyst play important roles in catalyst activity and selectivity for the direct synthesis. The direct synthesis of hydrogen peroxide was investigated in a bench-scale continuous process using the novel microreactor developed. The microreactor was fabricated based on the hydrodynamic and mass transfer studies and provided a high interfacial area and high mass transfer coefficient. The catalysts were prepared under optimum treatment conditions. The direct synthesis was conducted at various conditions. The thesis represents a step towards a commercially viable direct synthesis. The focus is on the two main challenges: mitigating the safety problem by utilization of microprocess technology and improving the selectivity by catalyst development.