Enhancement of water removal in the press section

The effectiveness of water removal on press section is very important for a paper and board machine’s functioning, efficiency and economy. Today, the most effective method for wet pressing is shoe press technology. Metso has carried out a number of studies concerning anew type of water removal method for a press section, which has also been patented. These studies include rough sketches and some test runs. These issues form the basis of this thesis. The objective of this work was to gather together information for a new and enhanced waterremoval method for a press section by studying the functioning of the device andcarrying out test runs. This method is referred to here as Hydronip. The main goal was tobuild a functional test site which fulfills all the necessary requirements and has all thenecessary information gathering devices. The design process was carried out by emphasizing the safety aspects. The goal was also to gather together information about the nip structure in running conditions, the seal function, and to carry out the nip tests with paper or board wads. This thesis consists of a theory part, the design and construction of the test site, and carrying out test runs through information gathering. The theory part consists of the principals of water removal from a press section, Hydronip construction, and the requirements for the test place. The safety aspects were taken into account especially in test runs, but also in the assembly stages. The design and construction of the test site includes the selection of equipment and surroundings that are needed for managing the test runs in the best possible way at certain premises. The test site included the equipment that was already on the premises. Some equipment could be used as it was but some equipment had to be manufactured or modified from existing equipment. A functional test site with information gathering devices was accomplished as a result of thethesis. Test runs demonstrated that the Hydronip concept is, at least on a small scale,functional. Short-term tests for seal functioning showed that the seal can be lubricatedsufficiently under different kinds of nip load situations. Wad tests demonstrated that the metal belt is durable against different sizes of external particles. The seal also endured wad tests even though the pressure impacts impaired the lubrication. MTS tests showing dry content increases, combined with a rough cost calculation and the basic function of the machine in test runs, show that with some further study Hydronip could be a promising new product for water removal from a paper or board machine’s press section.

EDTA- and DTPA-functionalized silica gel and chitosan adsorbents for the removal of heavy metals from aqueous solutions

Adsorbents functionalized with chelating agents are effective in removal of heavy metals from aqueous solutions. Important properties of such adsorbents are high binding affinity as well as regenerability. In this study, aminopolycarboxylic acid, EDTA and DTPA, were immobilized on the surface of silica gel, chitosan, and their hybrid materials to achieve chelating adsorbents for heavy metals such as Co(II), Ni(II), Cd(II), and Pb(II). New knowledge about the adsorption properties of EDTA- and DTPA-functionalizedadsorbents was obtained. Experimental work showed the effectiveness, regenerability, and stability of the studied adsorbents. Both advantages and disadvantages of the adsorbents were evaluated. For example, the EDTA-functionalized chitosan-silica hybrid materials combined the benefits of the silica gel and chitosan while at the same time diminishing their observed drawbacks. Modeling of adsorption kinetics and isotherms is an important step in design process. Therefore, several kinetic and isotherm models were introduced and applied in this work. Important aspects such as effect of error function, data range, initial guess values, and linearization were discussed and investigated. The selection of the most suitable model was conducted by comparing the experimental and simulated data as well as evaluating the correspondence between the theory behind the model and properties of the adsorbent. In addition, modeling of two-component data was conducted using various extended isotherms. Modeling results for both one- and twocomponent systems supported each other. Finally, application testing of EDTA- and DTPA-functionalized adsorbents was conducted. The most important result was the applicability of DTPA-functionalized silica gel and chitosan in the capturing of Co(II) from its aqueous EDTA-chelate. Moreover, these adsorbents were efficient in various solution matrices. In addition, separation of Ni(II) from Co(II) and Ni(II) and Pb(II) from Co(II) and Cd(II) was observed in two- and multimetal systems. Lastly, prior to their analysis, EDTA- and DTPA-functionalized silica gels were successfully used to preconcentrate metal ions from both pure and salty waters

Removal of cyanobacterial toxins by strains of probiotic bacteria

Nedbrytning av blågrönalgtoxiner med hälsobefrämjande mjölksyrebakterier Blomningar av cyanobakterier (blågrönalger) har blivit ett världsomfattande fenomen i eutrofierade vattenmiljöer. Cyanobakterier producerar toxiner, både levergifter och nervgifter, vilka utgör en hälsorisk för människan. Exponeringsrutter omfattar både dricksvatten och förorenade matvaror. Rening av dricksvatten från dessa toxiner är således av hög prioritet. Konventionella vatttenreningsprocesser är inte alltid tillräckligt effektiva mot cyanotoxiner. Därför behövs utveckling av nya effektiva biologiska metoder för vattenrening, vilka kunde komplettera de redan existerande metoderna. FM Sonja Nybom har i sin doktorsavhandling undersökt eliminering av cyanotoxiner från dricksvatten med hjälp av probioter. Probiotiska bakterier, såsom mjölksyrebakterier och bifidobakterier, finns i den naturliga tarmfloran och har även visats ha gynnsamma effekter för människans hälsa. I avhandlingen visades flera olika stammar av probiotiska mjölksyrebakterier och bifidobakterier effektivt eliminera cyanotoxiner, såsom levergiftiga microcystiner, från vatten. Elimineringen undersöktes under olika omständigheter och visades vara beroende av bland annat vattentemperatur, pH, celldensitet och närvaro av kolkälla (glukos) för bakterierna. Metaboliskt aktiva, levande bakterier krävdes för effektiv toxineliminering. En kombination av flera probiotstammar resulterade i effektivare nedbrytning av toxiner i jämförelse med enskilda bakteriestammar. Även reaktionstiden var av betydelse för effektiviteten; efter ett dygns inkubering åstadkoms nästan total nedbrytning. Sammanfattningsvis tyder resultaten på att metoder utnyttjande dessa hälsobefrämjande probiotiska bakterier kunde utvecklas till att användas vid rening av dricksvatten från cyanotoxiner samt användas som en personlig skyddsmekanism mot cyanotoxiner i mag-tarmkanalen.

Solids removal in pyrolysis

Pyrolysis is a process for turning biomass into liquid fuel. The process consists of heating the biomass in inert conditions and quenching the resulting vapors into oil. The oil has many potential uses, such as heating fuel in peak heating plants. In order to broaden the application base and improve the quality of the oil, solids removal has to be addressed. The solids may also increase the probability of plugging in downstream equipment. The purpose of this research was to gain an understanding of the formation of solids in the pyrolysis process and to assess options for reducing the solid content of the oil. From literature it is known that the solids can be removed either by hot vapor filtration, liquid treatment or multiple cyclones. Hot vapor filtration decreases yield, but improves the stability of the oil while simultaneously removing solids and ash. Liquid treatment techniques are good for removing large particles but involve losses of pyrolysis liquid. Cyclones are a traditional robust technique used regularly in pyrolysis. In the experimental part of this thesis, a 2 MWfuel pyrolysis setup with 2 cyclones in series was operated and monitored. Solid and liquid samples were collected from various parts of the process for further examination. Sampling and sample treatment techniques were developed. The chemical properties of the pyrolysis char were also analyzed and assessed as a function of reactor temperature and fluidizing velocity. By measuring the particle size distributions it was noticed that there were much smaller particles collected from the second cyclone than fed into pyrolysis. The solids in the pyrolysis oil were even smaller. This was most likely caused by attrition and shrinkage. Due to better separation efficiency of the cyclones in large particles, excess attrition should be avoided.

Application of cerium oxide thin films grown by atomic layer deposition for soot removal

The objective of the thesis is to study cerium oxide thin films grown by the atomic layer deposition (ALD) for soot removal. Cerium oxide is one of the most important heterogeneous catalysts and can be used in particulate filters and sensors in a diesel exhaust pipe. Its redox/oxidation properties are a key factor in soot oxidation. Thus, the cerium oxide coating can help to keep particulate filters and sensors clean permanently. The literature part of the thesis focuses on the soot removal, introducing the origin and structure of soot, reviewing emissions standards for diesel particulate matter, and presenting methods and catalysts for soot removal. In the experimental part the optimal ALD conditions for cerium oxide were found, the structural properties of cerium oxide thin films were analyzed, and the catalytic activity of the cerium oxide for soot oxidation was investigated. Studying ALD growth conditions of cerium oxide films and determining their critical thickness range are important to maximize the catalytic performance operating at comparatively low temperature. It was found that the cerium oxide film deposited at 300 °C with 2000 ALD cycles had the highest catalytic activity. Although the activity was still moderate and did not decrease the soot oxidation temperature enough for a real-life application. The cerium oxide thin film deposited at 300 °C has a different crystal structure, surface morphology and elemental composition with a higher Ce3+ concentration compared to the films deposited at lower temperatures. The different properties of the cerium oxide thin film deposited at 300 °C increase the catalytic activity most likely due to higher surface area and addition of the oxygen vacancies.

Effects of the partial removal of wood hemicelluloses on the properties of kraft pulp

The objective of this work was to study the effects of partial removal of wood hemicelluloses on the properties of kraft pulp.The work was conducted by extracting hemicelluloses (1) by a softwood chip pretreatment process prior to kraft pulping, (2) by alkaline extraction from bleached birch kraft pulp, and (3) by enzymatic treatment, xylanase treatment in particular, of bleached birch kraft pulp. The qualitative and quantitative changes in fibers and paper properties were evaluated. In addition, the applicability of the extraction concepts and hemicellulose-extracted birch kraft pulp as a raw material in papermaking was evaluated in a pilot-scale papermaking environment. The results showed that each examined hemicellulose extraction method has its characteristic effects on fiber properties, seen as differences in both the physical and chemical nature of the fibers. A prehydrolysis process prior to the kraft pulping process offered reductions in cooking time, bleaching chemical consumption and produced fibers with low hemicellulose content that are more susceptible to mechanically induced damages and dislocations. Softwood chip pretreatment for hemicellulose recovery prior to cooking, whether acidic or alkaline, had an impact on the physical properties of the non-refined and refined pulp. In addition, all the pretreated pulps exhibited slower beating response than the unhydrolyzed reference pulp. Both alkaline extraction and enzymatic (xylanase) treatment of bleached birch kraft pulp fibers indicated very selective hemicellulose removal, particularly xylan removal. Furthermore, these two hemicellulose-extracted birch kraft pulps were utilized in a pilot-scale papermaking environment in order to evaluate the upscalability of the extraction concepts. Investigations made using pilot paper machine trials revealed that some amount of alkalineextracted birch kraft pulp, with a 24.9% reduction in the total amount of xylan, could be used in the papermaking stock as a mixture with non-extracted pulp when producing 75 g/m2 paper. For xylanase-treated fibers there were no reductions in the mechanical properties of the 180 g/m2 paper produced compared to paper made from the control pulp, although there was a 14.2% reduction in the total amount of xylan in the xylanase-treated pulp compared to the control birch kraft pulp. This work emphasized the importance of the hemicellulose extraction method in providing new solutions to create functional fibers and in providing a valuable hemicellulose co-product stream. The hemicellulose removal concept therefore plays an important role in the integrated forest biorefinery scenario, where the target is to the co-production of hemicellulose-extracted pulp and hemicellulose-based chemicals or fuels.