Wet Oxidation of Paper Mill Evaporation Concentrates

Tämän työn tarkoituksena oli tutkia lämpötilan pH:n ja vetyperoksidin vaikutusta kuorimoveden haihdutuskonsentraatin märkähapetuksessa. Kirjallisuusosassa esitellään massan ja paperin valmistusta sekä kuorintaprosessi. Lisäksi tarkastellaan kuoren kemiallista koostumusta, jäteveden ja prosessiveden käsittelymenetelmiä sekä märkähapetuksen periaatteita. Kokeellinen osa käsittää erään suomalaisen paperitehtaan kuorimoveden haihdutuskonsentraatin märkähapetuskokeet. Hapetuskokeet tehtiin useammassa eri lämpötilassa, pH:ssa ja vetyperoksidikonsentraatiossa. Em. muuttujien vaikutusta tutkittiin kemialliseen hapenkulutukseen (COD), biologiseen hapenkulutukseen (BOD), välittömästi saatavana olevan biologiseen hapenkulutukseen (IABOD), orgaaniseen kokonaishiileen (TOC) ja tanniini/ligniini pitoisuuteen. Koetulokset osoittivat, että korkeimmat COD- ja TOC-reduktiot saavutettiin H2O2-katalysoidulla märkähapetuksella jäteveden alkuperäisessä pH:ssa (60 % reduktio COD:lla ja 45 % reduktio TOC:lla lämpötilassa 170 °C ja 0.2 g H2O2/g COD). Toisaalta, parhaat tulokset biohajoavuuden paranemisen suhteen saavutettiin emäksisissä olosuhteissa, jossa 170 °C:ssa saavutettiin BOD/COD-arvo 76 %. Emäksisissä olosuhteissa saavutettiin lähes täydellinen tanniinin reduktio lämpötila-alueella 130-170 °C, mutta näissä lämpötiloissa orgaanisen kuorman alenemista ei havaittu.

Supersaturation-controlled crystallization

Identification of product requirements and quality, together with the management of production are key issues in chemical engineering. Quality control of crystalline products is part of the quality of many industrially manufactured products like paper, paintings, medicines and fertilizers. In most crystallization cases, quality is described with the size, polymorph, shape and purity of the crystal. The chemical composition, hydrodynamics and driving force, together with the operating temperature are in a key position when the properties of a crystalline product are controlled with the crystallization process. This study concentrates on managing the identified properties of a crystalline product with the control of a driving force. The controlling of the driving force can be based on the change of solubility or the change of concentration. Solubility can be changed with temperature, pressure and an antisolvent. The concentration of crystallizing compound, the solute can be changed with the evaporation of the solvent and with the addition of a reagent. The present study focuses on reagent addition and temperature change as methods of changing the level of the driving force. Three control structures for direct control of supersaturation are built, one for cooling crystallization and two for reactive crystallization. Closed loop feedback control structures are based on the measurement of the solute concentration with attenuated total reflection - Fourier transform infrared spectrometer. The details of the reagent feed are analyzed with experimental studies and with results of computational fluid dynamic simulations of the inert particle pulse in the premixer and inert particle injection to the mixing tank. Nucleation in conditions of controlled reactive crystallization is analyzed with Nielsen’s equation of homogeneous nucleation. The resulting control systems, based on regulation of supersaturation, can be used to produce the desired polymorph of an organic product. The polymorph composition of product crystals is controlled repeatably with the decision of a set value of supersaturation level.

Specific surface charging of latex, clay and mineral oxide particles in aqueous, non-aqueous and mixed solvent systems

En djupare förståelse för växelverkan mellan partiklar i suspensioner är av betydelse för utvecklingen av en mängd olika industriella produkter och processer. Till exempel kan nämnas pigmentbaserade färger och bestrykning av papper. Genom att öka kontrollbarheten kan dessa lättare optimeras för att uppnå förbättrade produktegenskaper och/eller sänkta produktionskostnader. Av stor betydelse är även en förbättrad möjlighet att minska produktens miljöpåverkan. I avhandlingen studerades jonstyrkan och jonspecificiteten inverkan i olika akvatiska suspensioner innehållande olika elektrolyter. De partiklar som avhandlingen omfattade var metalloxider, leror samt latex. Jonstyrkan studerades från låga (c <10-3M) till och med höga (c> 10-1M) elektrolytkoncentrationer. Vid koncentrationer under 0.1 M var partikelladdningen styrd av pH och jonstyrkan. Vid högre elektrolytkoncentrationer påverkade även jonspecificiteten partikelladdningen. Jonspecificiteten arrangerades i fenomenologiska serier funna i litteraturen samt med Born modellen definierad i termodynamiken. Överraskande höga absoluta zeta-potential värden erhölls vid höga elektrolytkoncentrationer vilket visar att den elektrostatiska repulsionen har betydelse även vid dessa förhållanden. Vidare studerades titanoxidsuspensioners egenskaper i akvatiska, icke-akvatiska och blandade lösningssystem under varierande koncentration av oxal- och fosfatsyra. Vid lågt vatteninnehåll studerades även suspensioner med svavelsyra. Konduktiviteten i suspensioner med lågt vatteninnehåll ökade med tillsatt oxal- eller fosforsyra vilket är en omvänd effekt jämfört med svavelsyra eller akvatiska suspensioner. Den omvända effekten skiftade gradvis tillbaka med ökad vatteninnehåll. En analys av suspensionernas adsorption i höga etanolkoncentrationer gjordes med konduktiviteten, pH och zeta-potentialen. Viskositet studerades och applicerades framgångsrikt i viskositet/ytladdningsmodeller utvecklade för akvatiska suspensioner.

Recovery of carboxylic acids from aqueous streams by extraction and back extraction

Separation of carboxylic acids from aqueous streams is an important part of their manufacturing process. The aqueous solutions are usually dilute containing less than 10 % acids. Separation by distillation is difficult as the boiling points of acids are only marginally higher than that of water. Because of this distillation is not only difficult but also expensive due to the evaporation of large amounts of water. Carboxylic acids have traditionally been precipitated as calcium salts. The yields of these processes are usually relatively low and the chemical costs high. Especially the decomposition of calcium salts with sulfuric acid produces large amounts of calcium sulfate sludge. Solvent extraction has been studied as an alternative method for recovery of carboxylic acids. Solvent extraction is based on mixing of two immiscible liquids and the transfer of the wanted components form one liquid to another due to equilibrium difference. In the case of carboxylic acids, the acids are transferred from aqueous phase to organic solvent due to physical and chemical interactions. The acids and the extractant form complexes which are soluble in the organic phase. The extraction efficiency is affected by many factors, for instance initial acid concentration, type and concentration of the extractant, pH, temperature and extraction time. In this paper, the effects of initial acid concentration, type of extractant and temperature on extraction efficiency were studied. As carboxylic acids are usually the products of the processes, they are wanted to be recovered. Hence the acids have to be removed from the organic phase after the extraction. The removal of acids from the organic phase also regenerates the extractant which can be then recycled in the process. The regeneration of the extractant was studied by back-extracting i.e. stripping the acids form the organic solution into diluent sodium hydroxide solution. In the solvent regeneration, the regenerability of different extractants and the effect of initial acid concentration and temperature were studied.

Haihdutusnopeuksien määritys glysiinin alipainekiteytyksessä

Alipainekiteytyksessä tasalaatuisen lopputuotteen valmistamiseksi kiteytysolosuhteiden vaikutus liuottimen haihtumisvuohon ja kiteiden ominaisuuksiin on huomioitava. Kandidaatin työn tavoitteena oli selvittää, miten glysiinin alipainekiteytyksessä vesiliuoksesta kiteytysolosuhteet (lämpötila ja paine) vaikuttavat liuottimen haihtumisvuohon ja syntyvien kiteiden polymorfiaan. Haihdutuskokeet suoritettiin puhtaalle vedelle ja alipainekiteytyskokeet glysiinin 95 % kylläiselle vesiliuokselle lämpötiloissa 40 °C, 50 °C ja 60 °C ja paineissa 40 mbar, 60 mbar ja 80 mbar. Kiteyttimenä käytettiin suljettua, virtaushaitoilla, sekoittimella ja ohjausputkella varustettua reaktoria johon oli kytketty alipainepumppu ja termostaatti paineen ja lämpötilan ohjaamiseksi. Nesteen määrä haihdutuskokeissa oli 2 kg ja alipainekiteytyskokeissa 1,2 kg. Osa alipainekiteytyskokeista saaduista kiteistä analysoitiin jauheröntgendiffraktioanalysaattorin (PXRD, engl. powder x-ray diffraction) avulla. Kaikki PXRD-laitteella analysoidut alipainekiteytyskokeissa saadut kiteet osoittautuivat glysiinin γ-polymorfiksi. Kiteytysolosuhteilla oli selkeä vaikutus haihtumisvuohon, mutta vaikutusta glysiinikiteiden polymorfiaan ei havaittu koealueella.

Influence of multi-phase phenomena on semibatch crystallization processes of aqueous solutions

Crystal properties, product quality and particle size are determined by the operating conditions in the crystallization process. Thus, in order to obtain desired end-products, the crystallization process should be effectively controlled based on reliable kinetic information, which can be provided by powerful analytical tools such as Raman spectrometry and thermal analysis. The present research work studied various crystallization processes such as reactive crystallization, precipitation with anti-solvent and evaporation crystallization. The goal of the work was to understand more comprehensively the fundamentals, phenomena and utilizations of crystallization, and establish proper methods to control particle size distribution, especially for three phase gas-liquid-solid crystallization systems. As a part of the solid-liquid equilibrium studies in this work, prediction of KCl solubility in a MgCl2-KCl-H2O system was studied theoretically. Additionally, a solubility prediction model by Pitzer thermodynamic model was investigated based on solubility measurements of potassium dihydrogen phosphate with the presence of non-electronic organic substances in aqueous solutions. The prediction model helps to extend literature data and offers an easy and economical way to choose solvent for anti-solvent precipitation. Using experimental and modern analytical methods, precipitation kinetics and mass transfer in reactive crystallization of magnesium carbonate hydrates with magnesium hydroxide slurry and CO2 gas were systematically investigated. The obtained results gave deeper insight into gas-liquid-solid interactions and the mechanisms of this heterogeneous crystallization process. The research approach developed can provide theoretical guidance and act as a useful reference to promote development of gas-liquid reactive crystallization. Gas-liquid mass transfer of absorption in the presence of solid particles in a stirred tank was investigated in order to gain understanding of how different-sized particles interact with gas bubbles. Based on obtained volumetric mass transfer coefficient values, it was found that the influence of the presence of small particles on gas-liquid mass transfer cannot be ignored since there are interactions between bubbles and particles. Raman spectrometry was successfully applied for liquid and solids analysis in semi-batch anti-solvent precipitation and evaporation crystallization. Real-time information such as supersaturation, formation of precipitates and identification of crystal polymorphs could be obtained by Raman spectrometry. The solubility prediction models, monitoring methods for precipitation and empirical model for absorption developed in this study together with the methodologies used gives valuable information for aspects of industrial crystallization. Furthermore, Raman analysis was seen to be a potential controlling method for various crystallization processes.

Continuous Counter-current Solvent Extraction of Magnesium and Calcium from Lithium-rich Brine

Solvent extraction of calcium and magnesium impurities from a lithium-rich brine (Ca ~ 2,000 ppm, Mg ~ 50 ppm, Li ~ 30,000 ppm) was investigated using a continuous counter-current solvent extraction mixer-settler set-up. The literature review includes a general review about resources, demands and production methods of Li followed by basics of solvent extraction. Experimental section includes batch experiments for investigation of pH isotherms of three extractants; D2EHPA, Versatic 10 and LIX 984 with concentrations of 0.52, 0.53 and 0.50 M in kerosene respectively. Based on pH isotherms LIX 984 showed no affinity for solvent extraction of Mg and Ca at pH ≤ 8 while D2EHPA and Versatic 10 were effective in extraction of Ca and Mg. Based on constructed pH isotherms, loading isotherms of D2EHPA (at pH 3.5 and 3.9) and Versatic 10 (at pH 7 and 8) were further investigated. Furthermore based on McCabe-Thiele method, two extraction stages and one stripping stage (using HCl acid with concentration of 2 M for Versatic 10 and 3 M for D2EHPA) was practiced in continuous runs. Merits of Versatic 10 in comparison to D2EHPA are higher selectivity for Ca and Mg, faster phase disengagement, no detrimental change in viscosity due to shear amount of metal extraction and lower acidity in stripping. On the other hand D2EHPA has less aqueous solubility and is capable of removing Mg and Ca simultaneously even at higher Ca loading (A/O in continuous runs > 1). In general, shorter residence time (~ 2 min), lower temperature (~23 °C), lower pH values (6.5-7.0 for Versatic 10 and 3.5-3.7 for D2EHPA) and a moderately low A/O value (< 1:1) would cause removal of 100% of Ca and nearly 100% of Mg while keeping Li loss less than 4%, much lower than the conventional precipitation in which 20% of Li is lost.

On the Properties and Cosmology of Q-balls

The properties and cosmological importance of a class of non-topological solitons, Q-balls, are studied. Aspects of Q-ball solutions and Q-ball cosmology discussed in the literature are reviewed. Q-balls are particularly considered in the Minimal Supersymmetric Standard Model with supersymmetry broken by a hidden sector mechanism mediated by either gravity or gauge interactions. Q-ball profiles, charge-energy relations and evaporation rates for realistic Q-ball profiles are calculated for general polynomial potentials and for the gravity mediated scenario. In all of the cases, the evaporation rates are found to increase with decreasing charge. Q-ball collisions are studied by numerical means in the two supersymmetry breaking scenarios. It is noted that the collision processes can be divided into three types: fusion, charge transfer and elastic scattering. Cross-sections are calculated for the different types of processes in the different scenarios. The formation of Q-balls from the fragmentation of the Aflieck-Dine -condensate is studied by numerical and analytical means. The charge distribution is found to depend strongly on the initial energy-charge ratio of the condensate. The final state is typically noted to consist of Q- and anti-Q-balls in a state of maximum entropy. By studying the relaxation of excited Q-balls the rate at which excess energy can be emitted is calculated in the gravity mediated scenario. The Q-ball is also found to withstand excess energy well without significant charge loss. The possible cosmological consequences of these Q-ball properties are discussed.