Paper is comprised of quasi-randomly distributed fibres, fines and different additives. The properties of paper depend on the type of fibres used, their uniformity of distribution, the amount and type of fines and fillers. It is difficult to predict how a particular component will behave in a mixture. This will depend on the form of material introduced (flocculated or dispersed) and on what kind of interactions will take place. These factors can be controlled by various wet-end strategies based on known colloidal behaviour of various additives. Thus, applying this knowledge to papermaking, one should be able to predict and control final structures of paper, which will be reflected in optical and mechanical properties. / A thorough understanding of the effects of different materials, such as fines and fillers, on optical and mechanical properties of paper can only be obtained from a systematic study. Therefore, this research focused on elucidating the relationship between the nature and amount of fines and fillers and paper properties. The studies were mainly limited to papers made from thermomechanical pulps (TMP), although occasionally comparisons with other pulps were made as well.

Oxygen-alkaline pulping is a sulphur-free chemical pulping process, which has a potential to replace the kraft process as an environmentally more viable alternative. However, there are some drawbacks to the process, which have so far prevented it from commercialization. The penetration of oxygen into the structure of wood chips and rather severe degradation of carbohydrates are the main problems that result in high reject contents and low pulp strengths. In this study, wood chips, after presoaking in a 0.2% solution of alkali, were mechanically treated in a compression screw feeder with the aim to facilitate the penetration of oxygen. Mechanically pretreated wood chips produced oxygen alkali pulps with screened yields that were almost 13% higher than those without mechanical treatment. At the same time, the total yields of both pulps were comparable. To improve the strength of the oxygen-alkaline pulps, the pH of the pulping liquor was kept constant between 7 and 8 throughout the pulping process. This resulted in a pulp that has a viscosity 3 times greater than that of the control oxygen-alkaline cook, thus indicating an improvement in strength properties.

Drying Doctor, a multiple technique simulator of the paper drying process, has been developed at the Pulp and Paper Research Centre, McGill University. This thesis examines the different approaches to the modeling of this process, provides a rigorous validation of the simulation program and demonstrates its utility with four containerboard machines of Norampac Inc. / Several features differentiate this simulator from others. When heavy grades of paper are produced or when high intensity drying processes are used even with thin sheets, substantial thickness direction gradients of moisture content and temperature develop across the sheet, demonstrating the necessity of a fully microscale model such as employed by Drying Doctor. / Using industrial and laboratory data for a variety of paper grades and drying processes, 31 uncalibrated simulations for machine speed showed a standard deviation of only 3.4% from known speeds. Through simulation of modified operating conditions such as steam pressure, spoiler bars, pocket air conditions and addition of the high intensity drying process, Yankee air impingement dryers, substantial production rate increases for the industrial partner's papermachines through use of the Drying Doctor simulator were shown possible.

Air drying of paper by pure impingement, pure through flow and by combination of impingement and through flow was studied. For the combined process the inlet and both outlet air flow rates were held constant throughout drying, thereby providing results appropriate for analysis of the complex and interacting kinetics. / Pure impingement drying rate curves were quantified with three parameters which were related to drying process conditions: constant drying rate, critical moisture content and the exponent for a power law relationship over the falling rate period. The Churchill - Usagi asymptotic approach model was tested and found not applicable. / For pure through drying the constant drying rate period disappears at higher drying intensities leaving two drying rate periods, the increasing rate and falling rate periods. A theoretically based exponential relationship was obtained for the increasing rate period, where up to 47% of the drying may occur. Drying rate curves were quantified with no subjective judgements, using five parameters: moisture contents at the end of the increasing rate and constant rate periods, constant drying rate, and exponents for the increasing and falling rate period relations. A universal normalized drying rate curve was obtained. Through drying rates are the same with or without impinging jets. / In combined impingement and through air drying, an adiabatic process, removal of impingement boundary layer humidity by through flow makes both components of the process nonadiabatic. Relative to pure impingement drying, impingement water removal rates are sensitively reduced by through flow. Because critical moisture content is intrinsically lower for through drying than impingement drying, through flow water removal rate curves can be strikingly different from pure through drying, with addition of a unique feature, a secondary increasing rate period when paper temperature is driven up by the falling rate period of impingement water removal. Parameters for quantitative representation were determined, analyzed and related to drying process conditions. / Of two prior models for the combined impingement and through air drying of paper, trends assumed by Randall (1984) are now found contrary to actual rates while the Crotogino and Allenger (1979) model has the trends correct but over predicts the drying rates now measured. Results of the pilot plant work of Burgess et al. (1972) are consistent with the comprehensive model now developed to predict drying time and drying rate for combined impingement and through flow air drying of paper.

The objective of this project was to study systematically the NSSC-AQ pulping process in order to improve the penetration of anthraquinone and sodium sulfite in wood and to simulate the mass transfer and delignification processes. / In a heterogeneous reaction system, such as wood pulping, two main factors control the overall reaction rate: liquor penetration and chemical diffusion. As a first step, some wood characteristics affecting liquor impregnation were evaluated: 1) fiber hydraulic radius, 2) air, steam and water content, 3) wood elasticity and compressibility. Secondly, impregnation and pulping experiments were performed while varying the pre-steaming, compression and soaking time. Finally, experimental profiles were compared to computer simulated results. The two most commonly used species by the pulp industry were chosen for this study: 1) black spruce sapwood and heartwood as well as 2) trembloid poplar sapwood. / Impregnation of sulfite-AHQ liquor in wood blocks was simulated by a three-dimensional "Control Volume Finite Difference Method (CVFDM)". To de-couple the pressure and velocity fields, typical to convection-diffusion problems, a mass balance around individual control volume was performed using Poiseuille's capillary flow equation. The pulping kinetic differential equations were included into the CVFDM model to simulate a three-dimensional delignification pattern in the wood. / In general, the progression of the anthraquinone impregnation was slow and non-uniform in comparison to sulfite which penetrated rapidly and uniformly during pulping. Furthermore, delignification uniformity was related to the initial chemical profiles observed after impregnation. This confirms the importance of chemical pre-treatment for high yield pulping in order to minimize uneven delignification for chips thicker than 3mm. Results showed that, in most cases, computer simulated profiles were similar to experimental anthraquinone and sulfite impregnation patterns.

Microparticulate retention aids, consisting of a high molecular weight polymer used in conjunction with inorganic microparticles, are widely used to improve the process colloid retention in papermaking. Such additives are generally introduced to the paper stock prior to the web formation, so that fines and fillers are flocculated and retained into the forming web. This study investigated the mechanism of fines and filler retention under the high shear typical of papermaking. Retention and drainage were optimized using the newly built Laboratory Twin Former. The variables of interest include the concentrations of a cationic polyacrylamide polymer (CPAM) and bentonite, and their residence times with the furnish. The former variables provide information for optimal bridging efficiency between the furnish components, while the latter variables indicate the appropriate location for adding the retention aid to reach maximum retention. The experimental results indicated that the bridging theory well predicts a maximum retention when only CPAM is used. For the microparticulate system, a longer residence time of bentonite in the furnish is preferable so that the fines retention improves by allowing sufficient time for colloids coagulation and by promoting bentonite deposition on the polymer coated fines. We also studied the mechanism of fines retention and quantified the drainage rate at the jet impingement region, with and without retention aids. By individually varying the jet velocity and the jet angle, the two velocity components of the jet, i.e. VjetX and VjetY were controlled. The slice opening and the wire velocity were kept constant. For the range investigated, the drainage force proportional to V jetY had little effect on fines retention or drainage. A high shear impact on the wire by increasing the jet velocity, and consequently by augmenting VjetX relative to the wire speed, reduced the fines retention and restricted the drainage rate.

Although many improvements in the manufacturing of musical instruments have been made recently, one aspect that has often been overlooked is that of the acoustic consistency of the final manufactured product. The aim of this thesis is to create a method in which a soundboard can be frequency matched to a brace in order to meet a set standard after assembly. A simple analytical model is created in order to study the effect of the plate's stiffness and brace thickness on the combined system. The assumed shape method is used in the analysis. Results show that by adjusting the thickness of the brace in order to compensate for the stiffness of the plate, one of the natural frequencies can be adjusted to meet a certain value. However, matching multiple natural frequencies cannot be done with a rectangular brace. Therefore modifications to the shape of the brace are suggested.

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