Potential and Challenges of Analog Reconfigurable Computation in Modern and Future CMOS

In this work, the feasibility of the floating-gate technology in analog computing platforms in a scaled down general-purpose CMOS technology is considered. When the technology is scaled down the performance of analog circuits tends to get worse because the process parameters are optimized for digital transistors and the scaling involves the reduction of supply voltages. Generally, the challenge in analog circuit design is that all salient design metrics such as power, area, bandwidth and accuracy are interrelated. Furthermore, poor flexibility, i.e. lack of reconfigurability, the reuse of IP etc., can be considered the most severe weakness of analog hardware. On this account, digital calibration schemes are often required for improved performance or yield enhancement, whereas high flexibility/reconfigurability can not be easily achieved. Here, it is discussed whether it is possible to work around these obstacles by using floating-gate transistors (FGTs), and analyze problems associated with the practical implementation. FGT technology is attractive because it is electrically programmable and also features a charge-based built-in non-volatile memory. Apart from being ideal for canceling the circuit non-idealities due to process variations, the FGTs can also be used as computational or adaptive elements in analog circuits. The nominal gate oxide thickness in the deep sub-micron (DSM) processes is too thin to support robust charge retention and consequently the FGT becomes leaky. In principle, non-leaky FGTs can be implemented in a scaled down process without any special masks by using “double”-oxide transistors intended for providing devices that operate with higher supply voltages than general purpose devices. However, in practice the technology scaling poses several challenges which are addressed in this thesis. To provide a sufficiently wide-ranging survey, six prototype chips with varying complexity were implemented in four different DSM process nodes and investigated from this perspective. The focus is on non-leaky FGTs, but the presented autozeroing floating-gate amplifier (AFGA) demonstrates that leaky FGTs may also find a use. The simplest test structures contain only a few transistors, whereas the most complex experimental chip is an implementation of a spiking neural network (SNN) which comprises thousands of active and passive devices. More precisely, it is a fully connected (256 FGT synapses) two-layer spiking neural network (SNN), where the adaptive properties of FGT are taken advantage of. A compact realization of Spike Timing Dependent Plasticity (STDP) within the SNN is one of the key contributions of this thesis. Finally, the considerations in this thesis extend beyond CMOS to emerging nanodevices. To this end, one promising emerging nanoscale circuit element - memristor - is reviewed and its applicability for analog processing is considered. Furthermore, it is discussed how the FGT technology can be used to prototype computation paradigms compatible with these emerging two-terminal nanoscale devices in a mature and widely available CMOS technology.

Linjasekoittimensekoituskyvyn määrittäminen

Työn tavoitteena oli kehittää sekoituskyvyn empiirinen monimuuttujafunktio eräälle dynaamiselle linjasekoittimelle. Monimuuttujafunktio oli tarkoitus kehittää sekoittimen kierrosnopeuden, virtaavien materiaalien ja tilavuusvirtausten perus-teella. Työn kirjallisuusosassa tarkasteltiin pääosin dynaamisia linjasekoittimia ja niiden toimintaperiaatteita sekä sekoituskyvyn määrittämiseen soveltuvia mittausmene-telmiä. Sekoitettavien aineiden epähomogeenisuus määritettiin mittaamalla termoelemen-teillä sekoittimen jälkeisen virran lämpötilavaihtelut. Sekoitettavina aineina käy-tettiin kolmea erilaista seosta: vesi-vesi-, kuitususpensio-vesi- ja karboksyylime-tyyliselluloosa-vesiseoksia. Muita muuttujia kokeissa olivat neljä eri sekoittimen kierrosnopeutta, neljä eri päävirran tilavuusvirtausta ja kolme päävirran sekäsii-hen lisättävän sivuvirran suhdetta. Monimuuttujafunktiokehitettiin vain kuitususpensio-vesiajojen pohjalta muilla seoksilla tehtyjen koeajojen osittaisen epäonnistumisen vuoksi. Hallitsevaksi pa-rametriksi monimuuttujafunktiossa osoittautui sekoittimen kierrosnopeus. Osittai-nen epäonnistuminen kokeissa johtui osaksi termoelementtien käytön sopimatto-muudesta sekoituskyvyn määrittämiseen ja osaksi sekoitettavien aineiden valin-nasta. Jatkotutkimuksiaajatellen muista sekoituskyvyn mittaamiseen käytettävissä olevista menetelmistäkäyttökelpoisimmaksi arvioitiin sähkötomografia.

ADVANCED NUMERICAL METHODS FOR SIMULATING MICROBUBBLE IN AN AERATED MIXING TANK

Fluid mixing in mechanically agitated tanks is one of the major unit operations in many industries. Bubbly flows have been of interest among researchers in physics, medicine, chemistry and technology over the centuries. The aim of this thesis is to use advanced numerical methods for simulating microbubble in an aerated mixing tank. Main components of the mixing tank are a cylindrical vessel, a rotating Rushton turbine and the air nozzle. The objective of Computational Fluid Dynamics (CFD) is to predict fluid flow, heat transfer, mass transfer and chemical reactions. The CFD simulations of a turbulent bubbly flow are carried out in a cylindrical mixing tank using large eddy simulation (LES) and volume of fluid (VOF) method. The Rushton turbine induced flow is modeled by using a sliding mesh method. Numerical results are used to describe the bubbly flows in highly complex liquid flow. Some of the experimental works related to turbulent bubbly flow in a mixing tank are briefly reported. Numerical simulations are needed to complete and interpret the results of the experimental work. Information given by numerical simulations has a major role in designing and scaling-up mixing tanks. The results of this work have been reported in the following scientific articles: ·Honkanen M., Koohestany A., Hatunen T., Saarenrinne P., Zamankhan P., Large eddy simulations and PIV experiments of a two-phase air-water mixer, in Proceedings of ASME Fluids Engineering Summer Conference (2005). ·Honkanen M., Koohestany A., Hatunen T., Saarenrinne P., Zamankhan P., Dynamical States of Bubbling in an Aerated Stirring Tank, submitted to J. Computational Physics.

Flash Memory Cells Reliability Parameters Investigation

The present work is a part of the large project with purpose to qualify the Flash memory for automotive application using a standardized test and measurement flow. High memory reliability and data retention are the most critical parameters in this application. The current work covers the functional tests and data retention test. The purpose of the data retention test is to obtain the data retention parameters of the designed memory, i.e. the maximum time of information storage at specified conditions without critical charge leakage. For this purpose the charge leakage from the cells, which results in decrease of cells threshold voltage, was measured after a long-time hightemperature treatment at several temperatures. The amount of lost charge for each temperature was used to calculate the Arrhenius constant and activation energy for the discharge process. With this data, the discharge of the cells at different temperatures during long time can be predicted and the probability of data loss after years can be calculated. The memory chips, investigated in this work, were 0.035 μm CMOS Flash memory testchips, designed for further use in the Systems-on-Chips for automotive electronics.

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.

Vaahdonestokemikaalin syöttötapahtuman tehostamisen vaikutus märkäosan toimintaan

An improved defoamer dosage procedure and a more efficient dosing point to the approach system were studied in this thesis. Their influence on paper machine wet end operations was investigated. The improved defoamer dosing procedure was examined at UMP-Kymmene Tervasaari PM8. Air content and its controlling methods at the paper machine were studied in the literature survey. Also the influence of dissolved gases and entrained air in the papermaking furnish were introduced. Feeding methods – a TrumpJet chemical mixer and traditional feeding devices – were reviewed. The defoamer’s functioning methods were studied. The influence of the use of defoamers was estimated based on the main selected wet end operations. In the experimental part, defoamer mixing with a traditional feeding method and two improved mixing stages were compared based on the air content profiles in PM8’s approach system. The reference dosage procedure was PM8’s old dosing system. The first dosage procedure in the comparison involved two TrumpJet chemical mixers installed on the bottom wire trays. The second element of comparison involved the improvement brought by a third TrumpJet chemical mixer installed on the top wire tray. This second comparison of the efficient defoamer feeding concept was made at a higher production speed of PM8. The air content control situation was also studied at the higher production speed. In addition the connection between the defoamer and air content was observed and a mill-scale system was studied. The economical benefits of the new dosing procedure were also reviewed. Air content profiles of short circulation were measured in the reference situation and the two comparison points of the study. These air content measurements proved the main gas load is introduced to PM8's paper furnish from the white water tray. Thick stock air content was not essential when the air volume flow was considered. The improved defoamer dosing procedure made lower dosage amounts possible. Compared with the traditional feeding system, the new defoamer feeding concept made only few direct improvements to the wet end operations and the produced paper itself. The lower defoamer need was noticed to have a positive influence on hydrophobic sizing and paper defects. The surfaces of the white water tanks and the operation of pumps were assessed based on the density variations of the suspension. The temperature in the white water silo was stated to have a significant influence on the air content measured in the first centrifugal cleaning stage.

Kuplakokojakauman hallinta happidelignifioinnissa

Työn tarkoituksena oli uutta kuvantamistekniikkaa hyödyntäen tutkia erilaisten tekijöiden vaikutusta kaasun dispergoitumiseen kemikaalisekoittimessa, kun kaasua sekoitetaan keskisakeaan massaan. Lisäksi työssä pyrittiin selvittämään, kuinka paljon kuitususpensioon tuotettu kaasufaasin kuplakokojakauma vaikuttaa happidelignifioinnin tulokseen. Kaasumaisten aineiden käyttäytymistä keskisakeissa kuitususpensiossa ei tarkkaan tunneta. Mikäli kaasumaisen hapen käyttäytymisestä saadaan uutta tietoa, tarjoaa tämä muun muassa uusia mahdollisuuksia kaasua sekoittavien laitteiden tuotekehityksessä. Työn kokeellinen osuus koostui kahdesta osasta, joista ensimmäisessä osassa selvitettiin sekoittimen roottorin pyörimisnopeuden, reaktorin kaasutilavuuden sekä suspension sakeuden vaikutusta muodostuvaan kaasun kuplakokojakaumaan. Työn jälkimmäisessä osassa arvioitiin yksivaiheisten keskisakeudessa tehtyjen happidelignifiointien perusteella suspensioon tuotetun kaasun kuplakokojakauman merkitystä happidelignifiointitulokseen. Kuplakokojakaumat määritettiin reaktoriin kiinnitetyllä kameralla kuvatuista valokuvista, joita otettiin sekoitustapahtuman aikana. Työn tuloksien perusteella sekoituksen voimakkuudella oli suurin vaikutus suspensioon muodostuvan kuplakokojakauman kannalta. Roottorin kierrosnopeuden kasvaessa kaasun keskimääräinen kuplakoko pieneni sekä havaittujen kuplien lukumäärää kasvoi huomattavasti. Myös suspension sakeuden kasvattamisen havaittiin vaikuttavan kuplakokoon pienentävästi. Happidelignifioinneissa saavutettiin paras kappareduktio, kun kaasun kuplakoko oli mahdollisimman pieni. Käytetty kuvantamistekniikka on tiettävästi ensimmäinen menetelmä, jolla saadaan reaaliaikaista tietoa vain muutamien kymmenien mikrometrien kokoisten kaasukuplien käyttäytymisestä oikeassa prosessitilanteessa.

Epäpuhtausmetallien talteenotto sinkkiprosessissa

There are small amounts of valuable metals, such as indium, gallium and germanium, in zinc process solutions. Their solvent extraction was studied in this work in sulphate solutions containing zinc and other metals present in industrial solutions. It was discovered, that a commercial bis(2-ethylhexyl)phosphate (D2EHPA) extractant can be used to extract indium and gallium. Indium was extracted separately at a higher acid concentration than gallium. Zinc was co-extracted faster than gallium and almost as much as gallium at the same pH. However, the scrubbing of zinc was possible using a dilute sulphuric acid and a short contact time while gallium losses were small. Both indium and gallium were stripped with sulphuric acid. Germanium was extracted with 5,8-diethyl-7-hydroxydodecane-6-oxime with the commercial name of LIX 63. Unlike other metals in the solution the extraction of germanium increased with different extractants as the acidity increased. Germanium extraction isotherm was measured for a 125 g/L sulfuric acid solution. The loaded organic phase was washed with pure water. It removed the co-extracted acid and part of the germanium and extracted impurities such as iron and copper. Germanium was stripped using a NaOH solution. A process model utilizing own experimentally determined extraction, scrubbing and stripping isotherms was made with HSC Sim software developed by Outotec Oyj. The model based on McCabe–Thiele diagrams was used in sizing the necessary amount of stages and phase ratios in a recovery process. It was concluded, that indium, gallium and germanium can be recovered in the process from a feed where their concentrations are low (<300 ppm). In an example case the feed contained also more than 20 g/L zinc and 2–8 g/L iron, aluminium and copper. The recoveries of indium, gallium and germanium were more than 90 % when 1–3 stages were used in each extraction, scrubbing and stripping section. Since the number of stages is small mixer-settlers would be well suited for this purpose.

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.

Memristive Computing

Memristive computing refers to the utilization of the memristor, the fourth fundamental passive circuit element, in computational tasks. The existence of the memristor was theoretically predicted in 1971 by Leon O. Chua, but experimentally validated only in 2008 by HP Labs. A memristor is essentially a nonvolatile nanoscale programmable resistor — indeed, memory resistor — whose resistance, or memristance to be precise, is changed by applying a voltage across, or current through, the device. Memristive computing is a new area of research, and many of its fundamental questions still remain open. For example, it is yet unclear which applications would benefit the most from the inherent nonlinear dynamics of memristors. In any case, these dynamics should be exploited to allow memristors to perform computation in a natural way instead of attempting to emulate existing technologies such as CMOS logic. Examples of such methods of computation presented in this thesis are memristive stateful logic operations, memristive multiplication based on the translinear principle, and the exploitation of nonlinear dynamics to construct chaotic memristive circuits. This thesis considers memristive computing at various levels of abstraction. The first part of the thesis analyses the physical properties and the current-voltage behaviour of a single device. The middle part presents memristor programming methods, and describes microcircuits for logic and analog operations. The final chapters discuss memristive computing in largescale applications. In particular, cellular neural networks, and associative memory architectures are proposed as applications that significantly benefit from memristive implementation. The work presents several new results on memristor modeling and programming, memristive logic, analog arithmetic operations on memristors, and applications of memristors. The main conclusion of this thesis is that memristive computing will be advantageous in large-scale, highly parallel mixed-mode processing architectures. This can be justified by the following two arguments. First, since processing can be performed directly within memristive memory architectures, the required circuitry, processing time, and possibly also power consumption can be reduced compared to a conventional CMOS implementation. Second, intrachip communication can be naturally implemented by a memristive crossbar structure.

Biomassahydrolysaattien puhdistus uutolla

Lignoselluloosasta koostuvasta biomassasta valmistetaan hydrolysoimalla sokereita, jotka jatkojalostetaan fermentoimalla bioetanoliksi. Bioetanolia käytetään fossiilisten polttoaineiden korvaajana esimerkiksi ajoneuvoissa. Bioetanolin valmistuksessa pyritään mahdollisimman hyvään saantoon, jotta sen valmistus olisi taloudellisesti kannattavaa. Hydrolyysin aikana syntyy sokerien lisäksi orgaanisia happoja, furaanin johdannaisia sekä fenolisia yhdisteitä. Yleisimpiä syntyviä yhdisteitä ovat muun muassa etikkahappo, furfuraali ja hydroksimetyylifurfuraali. Nämä yhdisteet haittaavat sokerien fermentointiprosessia ja pienentävät etanolin saantoa. Fermentointiprosessia haittaavien yhdisteiden poistoon hydrolysaattiliuoksesta voidaan käyttää esimerkiksi haihdutusta, membraanierotusta, adsorptiota, saostusta, sekä uuttoa. Tämän työn tarkoituksena oli tutkia leikkaussekoittimen soveltuvuutta biomassahydrolysaatin epäpuhtauksien erotukseen. Lisäksi kirjallisuusosassa on esitetty hydrolysointiprosessissa syntyviä haitta-aineita ja niiden erotusmenetelmiä.

Pressure filtration characteristics of enzymatically hydrolyzed biomass suspensions

Enzymatic hydrolysis of lignocellulosic polymers is likely to become one of the key technologies enabling industrial production of liquid biofuels and chemicals from lignocellulosic biomass. Certain types of enzymes are able to hydrolyze cellulose and hemicellulose polymers to shorter units and finally to sugar monomers. These monomeric sugars are environmentally acceptable carbon sources for the production of liquid biofuels, such as bioethanol, and other chemicals, such as organic acids. Liquid biofuels in particular have been shown to contribute to the reduction of net emissions of greenhouse gases. The solid residue of enzymatic hydrolysis is composed mainly of lignin and partially degraded fibers, while the liquid phase contains the produced sugars. It is usually necessary to separate these two phases at some point after the hydrolysis stage. Pressure filtration is an efficient technique for this separation. Solid-liquid separation of biomass suspensions is difficult, because biomass solids are able to retain high amounts of water, which cannot be readily liberated by mechanical separation techniques. Most importantly, the filter cakes formed from biomaterials are compressible, which ultimately means that the separation may not be much improved by increasing the filtration pressure. The use of filter aids can therefore facilitate the filtration significantly. On the other hand, the upstream process conditions have a major influence on the filtration process. This thesis investigates how enzymatic hydrolysis and related process conditions affect the filtration properties of a cardboard suspension. The experimental work consists of pressure filtration and characterization of hydrolysates. The study provides novel information about both issues, as the relationship between enzymatic hydrolysis conditions and subsequent filtration properties has so far not been considered in academic studies. The results of the work reveal that the final degree of hydrolysis is an important factor in the filtration stage. High hydrolysis yield generally increases the average specific cake resistance. Mixing during the hydrolysis stage resulted in undefined changes in the physical properties of the solid residue, causing a high filtration resistance when the mixing intensity was high. Theoretical processing of the mixing data led to an interesting observation: the average specific cake resistance was observed to be linearly proportional to the mixer shear stress. Another finding worth attention is that the size distributions of the solids did not change very dramatically during enzymatic hydrolysis. There was an observable size reduction during the first couple of hours, but after that the size reduction was minimal. Similarly, the size distribution of the suspended solids remained almost constant when the hydrolyzed suspension was subjected to intensive mixing. It was also found that the average specific cake resistance was successfully reduced by the use of filter aids. This reduction depended on the method of how the filter aids were applied. In order to obtain high filtration capacity, it is recommended to use the body feed mode, i.e. to mix the filter aid with the slurry prior to filtration. Regarding the quality of the filtrate, precoat filtration was observed to produce a clear filtrate with negligible suspended solids content, while the body feed filtrates were turbid, irrespective of which type of filter aid was used.

Siiderin ja long drink -juomien sekoitusprosessin kehittäminen

Diplomityössä perehdytään Hartwall Lahden tuotantolaitoksen juomanvalmistuksen osaston siiderin ja long drink –juomien valmistusprosessin kehittämiseen. Diplomityön tavoitteena oli löytää prosessin ongelma- ja poikkeamakohtia, tutkia mahdollisia hävikkikohteita ja suorittaa laadun osalta ajoseurantamittauksia. Ongelmakohtien pohjalta laadittiin parannusehdotuksia ja niitä toteutettiin jo tämän projektin aikana. Ongelma- ja poikkeamakohtia tutkittiin ajoprosessin aikana. Hävikkitutkimus kohdennettiin aromiliuoksen annostelulinjaan, nestesokerin an-nostelulinjaan ja tuotteiden alku- ja lopputyönnöille painetankkeihin. Painetankkien osalta mahdollisia hävikkikohteita tutkittiin kokeellisen toiminnan avulla ajo-prosessin aikana. Ajoprosessin käynnistyksen jälkeen selvitettiin milloin valmis tuote on painetankkien venttiilimatriisilla. Uudet parametrit alku- ja lopputyönnöille määritettiin tuoteputken, painetankkien pohjaputkien ja venttiilimatriisin tilavuuksien avulla. Hävikkitutkimuksen tuloksena saatiin pienennettyä hävikkiä ja näin ollen syntyi kustannussäästöjä. Hiilidioksidin sitoutuvuutta tutkittiin mittauksien avulla valmistusprosessin aikana. Mittauksien perusteella havaittiin, että hiilidioksidipitoisuus laskee painetankissa. Tämä johtuu valmiin tuotteen lämpötilamuutoksista. Tuotteen lämpötilaa voidaan tasata esimerkiksi levylämmönvaihtimen avulla.

Influence of reactant absorption and dissolution in heterogeneous precipitation processes

In this research work, the aim was to investigate the volumetric mass transfer coefficient [kLa] of oxygen in stirred tank in the presence of solid particle experimentally. The kLa correlations as a function of propeller rotation speed and flow rate of gas feed were studied. The O2 and CO2 absorption in water and in solid-liquid suspensions and heterogeneous precipitation of MgCO3 were thoroughly examined. The absorption experiments of oxygen were conducted in various systems like pure water and in aqueous suspensions of quartz and calcium carbonate particles. Secondly, the precipitation kinetics of magnesium carbonate was also investigated. The experiments were performed to study the reactive crystallization with magnesium hydroxide slurry and carbon dioxide gas by varying the feed rates of carbon dioxide and rotation speeds of mixer. The results of absorption and precipitation are evaluated by titration, total carbon (TC analysis), and ionic chromatrography (IC). For calcium carbonate, the particle concentration was varied from 17.4 g to 2382 g with two size fractions: 5 µm and 45-63 µm sieves. The kLa and P/V values of 17.4 g CaCO3 with particle size of 5µm and 45-63 µm were 0.016 s-1 and 2400 W/m3. At 69.9 g concentration of CaCO3, the achieved kLa is 0.014 s-1 with particle size of 5 µm and 0.017 s-1 with particle size of 45 to 63 µm. Further increase in concentration of calcium carbonate, i.e. 870g and 2382g , does not affect volumetric mass transfer coeffienct of oxygen. It could be concluded from absorption results that maximum value of kLa is 0.016 s-1. Also particle size and concentration does affect the transfer rate to some extend. For precipitation experiments, the constant concentration of Mg(OH)2 was 100 g and the rotation speed varied from 560 to 750 rpm, whereas the used feed rates of CO2 were 1 and 9 L/min. At 560 rpm and feed rate of CO2 is 1 L/min, the maximum value of Mg ion and TC were 0.25 mol/litre and 0.12 mol/litre with the residence time of 40 min. When flow rate of CO2 increased to 9 L/min with same 560 rpm, the achieved value of Mg and TC were 0.3 mol/litre and 0.12 mol/L with shorter residence time of 30 min. It is concluded that feed rate of CO2 is dominant in precipitation experiments and it has a key role in dissociation and reaction of magnesium hydroxide in precipitation of magnesium carbonate.