Rheological behavior of magnetic pulp fiber suspensions

This paper is focused on the rheology of magnetic pulp suspensions in absence and presence of an external magnetic field. Magnetic fibers were prepared by the lumen loading method using bleached eucalyptus fibers and cobalt ferrite (CoFe2O4) nanoparticles. The effect of mass consistency, temperature, concentration of magnetic fibers, and magnetic field strength on yield stress and apparent viscosity of the suspensions were investigated. In the absence of an applied field, a dependence of yield stress with consistency, as well as with the percentage of magnetic fibers present in the suspension, was found. In flow tests, all the suspensions exhibited shear-thinning behavior, showing that the viscosity is only affected by the consistency of the suspension. On the other hand, magnetorheological measurements show a negative effect of the applied magnetic field on the viscosity of the suspension.

Beating of Eucalyptus Pulp Fibers under Neutral and Alkaline Conditions – A Valley Beater Study

Beating is one of the most important and complicated processes that influences paper production and paper quality from both a process and a paper property standpoint. With increasing costs, environmental regulations and competitiveness in the today’s global market, paper and board producers revisit existing production process to decrease production costs. New approached with additives such as new developed in-situ precipitated paper fillers materials have the potential to reduce production cost and increase profit margins. For this research bleached eucalyptus Kraft pulp adjusted to a pH of 7.5, 11.0 and 12.3, and laboratory manufactured in-situ precipitated calcium carbonate with a filler level based on oven dry fiber content of 20.9% and 41.7% and a pH of 7.5, and commercial produced precipitated calcium carbonate filler of 10% and 20%. All pulp suspensions were beaten for 80 minutes with samples taken at the unbeaten level and 20 minutes increments. The beating curve over 80 minutes beating time show that pulp suspensions with in-situ produced filer material have a higher dewatering ability with increasing filler content compared to the pulps with commercial PCC and different pH values. Viscosity slightly decreases for pulp suspension with commercial and in-situ produced filler content. Pulp suspension at a pH of 12.3 showed a significant decrease in viscosity over the 80 minutes beating time, superseding the filler containing pulp suspensions. Basis weight decreased over beating time for all pulp suspensions, which can be explained with an increased fines production during beating and lower fiber retention during handsheet forming. The breaking length index increase for all pulp suspensions till 40 minutes of beating time for the filler containing pulp suspensions. Tear index and burst index curves based on beating time are similar for all pulp suspensions with a maximum at 40 minutes beating for the tear index and 60 minutes beating for the burst index. High filler containing pulp suspension showed the lowest tear index.

ELIMINATION OF ADHESIVE IMPURITIES OF THE RECOVERED PAPER IN FLOTATION PROCESS

The article presents results of the elimination of sticky impurities from recovered paper in laboratory flotation of three pulp suspensions with different whiteness, obtained directly from the production line before entering flotation. A combination of commercial agents releasing undesirable substances from recovered paper and means for regulation and stabilization of froth and modified micronized bentonit was used. In the flotation purification of pulp suspension with a whiteness of 53%, the combination of Prodeink Extra, Prodeink AS10 and Hydrocol OT reduced the macrostickies content by 58%, the ash content decreased from 18.5% to 4.5%, the whiteness increased from 53% to 56.4% and the residual color content was reduced from 385 ppm to 294 ppm. The pulp suspension with a whiteness of 64% showed a reduction in the content of macrostickies by 66%, a reduction in the ash content by 23.2%, an increase in whiteness by 1.4% and a reduction in the residual color content from 245 ppm to 194 ppm. The pulp suspension with a whiteness of 68.3% showed a decrease in the content of macrostickies by 58.1%, the ash content decreased from 35.7% to 6.3%, the whiteness increased by 1.1% and the content of residual color decreased from 157 ppm to 117 ppm.

Experimental Study and Computational Fluid Dynamics Modeling of Pulp Suspensions Flow in a Pipe

Eucalyptus and Pine suspensions flow in a pipe was studied experimentally and numerically. Pressure drop was measured for different mean inlet flow velocities. Electrical impedance tomography (EIT), was used to evaluate the prevailing flow regime. Fibers concentration distribution in the pipe cross section and plug evolution were inferred from EIT tomographic images. A modified low-Reynolds-number k–ε turbulence model was applied to simulate the flow of pulp suspensions. The accuracy of the computational fluid dynamics (CFD) predictions was significantly reduced when data in plug regime was simulated. The CFD model applied was initially developed to simulate the flow of Eucalyptus and Pine suspensions in fully turbulent flow regime. Using this model to simulate data in the plug regime leads to an excessive attenuation of turbulence which leads to lower values of pressure drop than the experimental ones. For transition flow regime, the CFD model could be applied successfully to simulate the flow data, similar to what happens for the turbulent regime.