Macleod M.,FPInnovations Paprican |
Dougall I.A.N.,Tembec Inc. |
Appita Journal | Year: 2010
Profiles of tensile strength along bleached kraft fibrelines have a common shape - a relatively steep decrease between pilot-plant reference pulp and its corresponding mill-made brownstock, then a much shallower one in bleaching, and a steeper one again across the pulp drying machine. The absolute level of tensile strength at any mill location depends primarily on original wood fibre morphology and on the mill's equipment and fibreline operations. Alone, pulp drying causes a loss of 1 km or more of breaking length in softwood kraft pulps, and is located in final drying. In a Flakt dryer, sheet solids content and tensile strength are inversely and linearly related through all but the first few decks. The best ways to counteract this phenomenon are to begin with as slender fibres as possible (e.g. by wood species, and by maximizing juvenile wood and earlywood), and to produce the pulp in a digester system known to preserve tensile strength during pulp-making.
Mahmood T.,FPInnovations Paprican
Journal of Environmental Engineering | Year: 2010
Studies undertaken at two aerated stabilization basins (ASBs) treating industrial effluents showed that the benthal solids characteristics varied substantially with location in three dimensions. The top 15-30 cm layer of the deposited solids was found to be the most active biodegradation zone with relatively little activity in the deeper layers. Ammonia and phosphate were present in high concentrations throughout the benthal solids and thus are not believed to limit biological growth and its associated benthal solids degradation kinetics. The nutrient concentrations were particularly higher in the downstream cells than those in the upstream cells. Implementing a suitable strategy to recycle these nutrients could result in minimized discharge and cost savings when treating nutrient-deficient industrial wastewaters. Dewatering properties of the benthal solids also substantially varied from one cell of an ASB to another. The selection and dose optimization of the dewatering polymers should therefore be completed separately for individual cells (or major zones) within an ASB system. Insights provided in this paper could be instrumental in proposing remedies to enhance in situ degradation of benthal solids and to better design and operate ASBs treating industrial effluents. © 2010 ASCE.
Zhang H.,Tianjin University of Science and Technology |
Zhang H.,University of New Brunswick |
Yuan Z.,FPInnovations Paprican |
Ni Y.,University of New Brunswick
Holzforschung | Year: 2011
High-yield pulp (HYP) has found wide applications in many paper grades. Usually, the strength properties of HYP must be improved and its freeness fine-tuned before sending it for paper machining, by means of refining at a low consistency, which requires energy. In this study, the possibility of avoiding refining of HYP was investigated by adding low percentages of refined and bleached wheat straw pulp (BWSP) to a HYP-containing mixture. The results show that the strength properties of a HYP and a hardwood kraft (HWKP) mixture can be improved with approximately 10% refined BWSP. In this manner, refining energy of 20 kWh t-1 is needed, and the pulp quality is improved to a similar level to that obtained from the same pulp mixture refined with an energy input of 70 kWh t-1. This approach also works for 100% HYP. The practical implication is that only a small percentage of refined BWSP is needed to improve the strength property of a HYP or HYP/HWKP mixtures, so that less refining energy is required in the low-consistency refining process. © 2011 by Walter de Gruyter Berlin New York.
Holmvall M.,Randnter |
Uesaka T.,Mid Sweden University |
Drolet F.,FPInnovations Paprican |
Lindstrom S.B.,KTH Royal Institute of Technology
Journal of Fluids and Structures | Year: 2011
The transfer of a microscopic fluid droplet from a flat surface to a deformable stochastic fibre network is investigated. Fibre networks are generated with different levels of surface roughness, and a two-dimensional, two-phase fluid-structure model is used to simulate the fluid transfer. In simulations, the Navier-Stokes equations and the Cahn-Hilliard phase-field equations are coupled to explicitly include contact line dynamics and free surface dynamics. The compressing fibre network is modelled as moving immersed boundaries. The simulations show that the amount of transferred fluid is approximately proportional to the contact area between the fluid and the fibre network. However, areas where the fluid bridges and never actually makes contact with the substrate must be subtracted. © 2011 Elsevier Ltd.
Gelinas V.,FPInnovations Paprican |
Vidal D.,FPInnovations Paprican
Powder Technology | Year: 2010
We have developed a direct imaging method for measuring particle shape distributions. It consists of a series of advanced automated algorithms that analyze 3D Atomic Force Microscopy (AFM) images of diluted pigment suspensions deposited onto glass cover slips. The method was applied to determine particle shape distributions of 10 different clay pigments from Brazil and Georgia, US. We found that the aspect ratio varies significantly and monotonically with particle diameter. The method gives generally lower average aspect ratios than those mentioned in previously published data, but still ranks pigments similarly. It was determined that Georgia clays generally have higher aspect ratios and broader shape distributions than Brazilian clays. This new direct automated AFM image analysis approach will be useful in pigment shape characterization and will provide important data for predicting coated paper performance. © 2010 Elsevier B.V.