No description available.

Diss. (sammanfattning) Stockholm : Tekn. högsk., 2004. / Härtill 7 uppsatser. I häftet felaktigt ISBN: KTH/FTP/R--2004/37--SE.

During the production of paper in paper mills, detrimental wood resin is released into the water circuit of the mill during the pulping process of the wood into fibres. This wood resin, termed pitch, can detrimentally deposit on the paper and on the paper machine equipment. The deposits mark the paper or can lead to a tear of the paper web involving a loss of output and a reduction in paper quality. Furthermore, the wood resinous compounds in paper mill effluents need to be reduced in order to minimise their toxic effects on water organisms. Talc has been the benchmark for many years as a mineral additive in pitch control. Since the papermaking process has changed over the years, the concept of mineral addition needs to be redefined and adopted towards the new circumstances. By understanding the fundamentals behind the adsorption of wood resin compounds from aqueous systems on to talc new mineral additives can be developed. A model for the determination of the aspect ratio of platy and rod-like particles has been developed, based on commonly available characterisations such as particle size, specific surface area and shape. It was found that the adsorption capacity of a mineral is directly proportional to its specific surface area, but only within its mineral family. Including the effect of surface hydrophilicity and hydrophobicity allowed fine tuning of the adsorption capacity of newly developed calcium carbonate grades. Furthermore, size exclusion effects, in porous, high surface area modified calcium carbonate, were seen to hinder complete coverage of the surface area by wood resin. With increasing pH, the adsorption efficiency of talc for colloidal wood resin was found to decrease. Under these alkaline conditions, which are common in modern paper making processes, talc preferentially adsorbed dissolved species. The use of the newly developed surface treated and modified calcium carbonates allowed more efficient adsorption of the colloidal fraction and, therefore, represent an efficient alternative to talc in pitch control. An increase in temperature led to an increased adsorption capacity of talc. This observation indicates the type of interaction tat controls the adsorption of hydrophobic pitch particles onto talc, i.e. the entropically favoured release of water from the hydrophobic talc surface as well as the hydrophobic methylene backbone of the hemicellulose.

Sustainable agriculture is a crucial factor to be considered in order to meet the growing demand for food production. The need for low cost and highly functional materials to provide the most efficient cultivation process has led the agriculture industry to consume petrochemical and mineral based material in an enormous amount. Thus, disposal of the used mulch materials has become a serious environmental issue. In this work, the possibility of using wood pulp fibre in two distinct applications in agriculture is investigated. First, agricultural mulching is the subject of the study and second, we focus on using wood pulp fibre as growing medium in greenhouses. Mulching in agriculture is an essential practice in order to have high crop yield, healthy products, and more efficient cultivation process. Over the years, agricultural mulch has been made out of a variety of materials. The most common of all is plastic mulch due to its low price and high functionality. However, the problems associated with applying and removing the enormous load of plastic and their disposal have made it an option far from ideal. Therefore, there is a need to develop mulches based on biodegradable materials. Paper-based mulch is one of the candidates, In the first chapter of this work, with a review of previous works in this area, we attempt to develop a new spray-able mulch based on wood pulp fibre. A novel foam forming method is utilised to deposit wood pulp fibres in combination with other chemicals as an evenly distributed fibre network on a porous bed. Currently available paper based-mulch is of a very high basis weight. In first part of this work, application of a foam formed low basis weight paper-based mulch is investigated. Whereas, in the second chapter, the use of wood pulp fibres in a similar function as “rockwool” in soilless greenhouse farming is investigated. Rockwool is named after fibres made of melted minerals at temperatures as high as 2000°C. Rockwool is used as blocks for seeds growth and propagation and as an alternative for soil in greenhouses. The feasibility of microenvironment control of the rockwool blocks in crop production plus its low cost have made is popular. However, their disposal has always been an environmental issue. The biodegradability of wood pulp fibres is a great advantage over mineral fibres used in rockwool. In the second chapter of current work, we study the possibility of using wood pulp fibres as carriers for agriculturally beneficial chemicals. Specifically, we focus on binding and release properties of small organic molecules from wood pulp fibres. The goal is to achieve an understanding of the capability of wood pulp fibres to be used in building biodegradable growing medium blocks in greenhouses. / Thesis / Master of Applied Science (MASc)

Dans les procédés classiques d'extraction de la cellulose pour la fabrication de la pâte à papier à partir de bois, les hémicelluloses sont dégradées et sont brûlées pour alimenter l'usine en énergie. En incluant une étape préalable d'extraction de ces polysaccharides, ils pourraient alors être réintroduits en aval du procédé, après cationisation, en tant qu'agent de renfort dans la pâte à papier. Dans ce travail, la cationisation de deux hémicelluloses modèles commerciales de type galactomannane et xylane a été effectuée par éthérification avec un époxyde cationique en solution aqueuse basique, avec des degrés de substitution de 0,1 à 1,3. Les paramètres prépondérants de la réaction sont la concentration des espèces et la quantité d'agent éthérifiant, tandis que la température et le temps de réaction influent principalement sur le rendement massique. Un plan d'expérience a permis de modéliser l'interaction entre les quantités de soude et d'époxyde et d'optimiser les conditions en fonction du DS avec une efficacité de réaction de 50%. La cationisation a également été appliquée à deux hémicelluloses extraites au FCBA. La mise en oeuvre de la réaction en absence de solvant a permis d'atteindre une efficacité de réaction de 70 à 90% et de réduire considérablement les quantités de réactif utilisées et d'effluents à traiter. Parmi la gamme de DS, les dérivés cationiques de DS 0,3 ont donné les meilleures propriétés après ajout dans la pâte à papier, le galactomannane étant plus efficace que le xylane. Enfin, la réticulation des chaînes du xylane extrait a permis d'augmenter les propriétés physiques du papier de 15% supplémentaires / With current paper pulp processes, hemicelluloses are decomposed during the extraction of cellulose fibres. By including a previous step of hemicellulose extraction, these compounds could be reused as additives in the paper pulp, instead of cationic starch. In this work, two model galactomannan and xylan hemicelluloses were cationized in aqueous solution under basic conditions by etherification with a cationic epoxide. Degrees of substitution from 0.1 to 1.3 were obtained. Species concentration and epoxide amount appeared as preponderant parameters of the reaction. With an experimental design, the interaction between sodium hydroxide and epoxide amounts was modelized, and reactional conditions were optimized depending on the desired DS with a reaction efficiency of 50%. Then, cationisation was applied to two hemicelluloses extracted in FCBA. The reaction was also carried out in absence of solvent with a reaction efficiency of 70-90%, by minimising reagents consumption and effluents. Cationic derivatives with DS 0.3 gave the best performance to increase the paper resistance when they were added in paper pulp, galactomannan being more efficient than xylan. Chain reticulation allowed increasing mechanical properties of paper of 15% for the extracted xylan

The press-section of a paper machine holds several different types of press rolls. One of the many press roll variants is the Valmet produced press roll, ViscoNip. This press roll utilizes an extended nip in order to increase the amount of water removed. The extended press nip in ViscoNip is special since it is controllable by a pressurized polyurethane press shoe. The press shoe runs through the body of the press roll. Due to limits of the current production process, new manufacturing methods and construction solutions are needed. In cooperation with another thesis, the current design and manufacturing process was reviewed and a plan intended to improve the current solution was formulated. The plan was to, by working together in a project, perform a product development process intended to create concepts able to utilize new methods of manufacturing. By using established methods of concept generation, such as Brainwriting 6-3-5, 11 concepts were created. Some of these concepts involved a redesign of the press shoe, leading to a need for construction and performance analysis. With the other thesis focusing on researching new possible and available manufacturing solutions. The work of this thesis fully committed to the structural and mechanical performance evaluation of the new concepts. This was performed by creating a model of the technical application using Finite Element Modelling in ABAQUS. The model included a hyperelastic material model for the polyurethane material as well as cohesive zone modelling to account for partitioning of the part. The model was then used to simulate the different concepts as they were subjected to a challenging load case. The results of which were used as the basis for structural and performance analysis. The analysis showed proof of sufficient structural stability and mechanical performance for all evaluated concepts. Then, in cooperation with the other thesis, a final concept choice was made. All in all, three different redesigned concepts were deemed as having potential for further development. The current solution was also deemed as having potential for future development but only when new manufacturing methods or techniques were considered.

The press-section of a paper machine holds several different types of press rolls. One of the many press roll variants is the Valmet produced press roll, ViscoNip. This press roll utilizes an extended nip in order to increase the amount of water removed. The extended press nip in ViscoNip is special since it is controllable by a pressurized polyurethane press shoe. The press shoe runs through the body of the press roll. Due to the limits of the current production process, new manufacturing methods and construction solutions are needed. In cooperation with another thesis, the current design and manufacturing process was reviewed and a plan intended to improve the current solution was formulated. The plan was to, by working together in a project, perform a product development process intended to create concepts able to utilize new methods of manufacturing. By using established methods of concept generation, such as Brainwriting 6-3-5, 11 concepts were created. Some of these concepts involved a redesign of the press shoe, leading to a need for construction and performance analysis. The other thesis focusing on the structural and mechanical performance evaluation of the new concepts. The work of this thesis focusing on researching new possible and available manufacturing solutions. The new concepts were analyzed with new and possible manufacturing methods to fulfill all the requirements. With all data, a document was created and market research was made to get feedback from more knowledgeable in the subject. Moreover, sequence analysis between the concepts with the current and those new manufacturing methods was made to further explain which manufacturing method that could solve the main problem. All in all, one different redesigned concept was deemed as having potential for further development. The current solution was also deemed as having potential for future development but only when new manufacturing methods or techniques were considered.

No description available.