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Changing Times in Tissue, Tissue360º Spring/Summer 2021
Changing Times in Tissue, Tissue360º Spring/Summer 2021
Journal articles
Magazine articles
Effects of agitator blade scaling on mixing in dissolving tanks, TAPPI Journal April 2022
ABSTRACT: Hard calcium carbonate scale often forms on the agitators in smelt dissolving tanks. The effects of this scale on mixing are not well understood. While mixing in tanks has often been modeled in the literature, there have been no studies involving agitator scaling. To better understand the impact of agitator scaling on hydrodynamics and tank concentrations, a steady state, three-dimensional (3D) model has been developed for a smelt dissolving tank at a kraft pulp mill. In this work, four cases are compared: an agitator with no scaling, mild scaling, moderate scaling, and extreme scaling. The extreme scaling case is representative of scale buildup on a dissolving tank agitator that was significant enough that the agitator had to be stopped and cleaned. The reduction in the agitator fluid jet velocity is relatively small for the mild and moderate scaling cases, but it becomes more significant for the extreme scaling case, for which the results indicate that the mixing of the smelt with the weak wash is likely poor and that there would thus be a risk of smelt pooling.
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Comparative study of guar gum and its cationic derivatives as pre-flocculating polymers for PCC fillers in papermaking applications, TAPPI Journal April 2022
ABSTRACT: In this work, gums from guar seeds were evaluated as a potential precipitated calcium carbonate (PCC) filler pre-flocculant to induce functional filler in papermaking applications. In recent years, guar has been conidered one of the promising wet-end additives due to its abundance, rich source of hemicellulose content, and bio-degradability. However, application of guar gum in filler pretreatment methods for producing high ash paper has scarcely been reported. In this paper, the flocculating ability of three types of guar gum was established with charge analysis and turbidity (NTU) of the system at 1% and 5% for each gum: native gum (NG) having a degree of substitution (DS) of 0, and cationic gums having a DS value of 0.07 (CL) and 0.15 (CH). It was interesting to observe that even at a 5% dose of G, the charge density of PCC did not deviate much from the initial values. The system carried a weak negativeharge, resulting in an unstable colloidal suspension that led to PCC-PCC particle bridging. On the other hand, the operative mechanism of CL and CH during adsorption and PCC flocculation was predicted to be charge neutralization and electrostatic-patch formation, accompanied by particle bridging. Note that CL, with a maximum 47.5% eduction in residual turbidity of PCC at a 1% dose, was much more efficient in doing so than the other two gums; NG had a 40% maximum reduction in residual turbidity at a 5% dose and CH had a maximum 30% reduction at a 1% ose. Later on, floc formation and structure were correlated with optical and field emission scanning electron microscopy (FE-SEM) images. In the next set of trials, paper properties were determined by varying the different gum dosages from 0.2% to 5% at a constant dose of 20% filler. It is also noteworthy to mention that with 1% CL (low DS) dose, PCC retention increased by 39%, which also enhanced the tensile, tear, burst, and opacity properties by 11%, 19%, 5%, and 4.4%, respectively, without significantly affecting the bulk properties. Further, wide-angle X-ray diffraction (XRD) analysis nd Fourier transform infrared (FTIR) analysis revealed that pre-flocculating PCC with a 1% gum dose did not induce any change in crystalline transformation. Based on observation, it was found that cationic gums with low DS values re a better choice for maximizing the strength of paper while maintaining bulk and high opacity when pre-flocculaion is adopted to increase the filler retention in paper.
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Editorial: Impacts from using recycled pizza boxes in furnish: TAPPI Journal’s runner-up to 2021 Best Research Paper, TAPPI Journal August 2022
ABSTRACT: The runner-up to the 2021 TAPPI Journal Best Research Paper was “Incorporation of post-consumer pizza boxes in the recover Fiber Stream: Impact of grease on finished product quality."
Journal articles
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Edge crush testing methods and box compression modeling, TAPPI Journal August 2022
ABSTRACT: While multiple test procedures have been developed to assess the inherent compressive strength of corrugated materials (edge crush test, ECT), limited work has explored the appropriateness of each in the context of box compression modeling. This study incorporates a variety of real-world samples, highlighting the varying challenges different ECT methods face in measuring the intrinsic compressive resistance of combined corrugated board. We examine each of these methods as inputs for different types of models, as well as discuss the propagation of measurement variation through the modeling effort. By highlighting the cases in which a given ECT method no longer proves to be an optimal parameter in box compression strength modeling, we explore how we might better measure this material property.
Journal articles
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The Creep Properties of Paper, TAPPI Journal August 2022
ABSTRACT: The creep proprties of alpha-pup handshetts were determined at various constant tensile loads and relative humidities for the purpose of clarifying the prerupture mechanical behavior of paper.
Journal articles
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SetPoint: It’s All About the Knowledge, Tissue360º Fall/Winter 2022
SetPoint: It’s All About the Knowledge, Tissue360º Fall/Wint
Journal articles
Magazine articles
Prepare to Expect the Unexpected, Tissue360º Fall/Winter 2022
Prepare to Expect the Unexpected, Tissue360º Fall/Winter 202
Journal articles
Magazine articles
A model black liquor formulation for use in development and evaluation of membranes for concentrating weak black liquor, TAPPI Journal February 2022
ABSTRACT: As part of a larger program to develop robust membranes for concentrating weak black liquor prior to the evaporation step, several commercially available membranes were tested for suitability in this application. Given the variation in kraft black liquor for various wood species, the mill-to-mill variations, and the challenges of obtaining fresh samples, the need became apparent for a synthetic reference black liquor that would allow any membrane developer to test a new prototype membrane and compare the results with others. We present a formulation for a model black liquor (MBL) similar to real kraft black liquor in the composition of the major species that can be formulated from readily available reagents. The MBL was tested with two commercial membranes and resulted in similar levels of lignin retention as the real black liquor. It also showed similar viscosity behavior to real black liquor as a function of solids content.
Journal articles
Magazine articles
Experiments and visualization of sprays from beer can and turbo liquor nozzles, TAPPI Journal February 2022
ABSTRACT: Industrial scale swirl-type black liquor nozzles were studied using water as the test fluid. Simple water spraying experiments were found to be very beneficial for studying and comparing nozzles for black liquor spraying. These kinds of experiments are important for finding better nozzle designs. Three nozzle designs were investigated to understand the functional differences between these nozzles. The pressure loss of nozzle 1 (“tangential swirl”) and nozzle 3 (“turbo”) were 97% and 38% higher compared to nozzle 2 (“tan-gential swirl”). Spray opening angles were 75°, 60°, and 35° for nozzles 1, 2, and 3, respectively. Video imaging showed that the nozzles produced sprays that were inclined a few degrees from the nozzle centerline. Spray patter-nation showed all the sprays to be asymmetric, while nozzle 2 was the most symmetric. Laser-Doppler measure-ments showed large differences in spray velocities between nozzles. The spray velocity for nozzle 1 increased from 9 m/s to 15 m/s when the flow rate was increased from 1.5 L/s to 2.5 L/s. The resulting velocity increase for nozzle 2 was from 7 m/s to 11 m/s, and for nozzle 3, it was from 8 m/s to 13 m/s. Tangential flow (swirl) directed the spray 6°•12° away from the vertical plane. Liquid sheet breakup mechanisms and lengths were estimated by analyzing high speed video images. The liquid sheet breakup mechanism for nozzle 1 was estimated to be wave formation, and the sheet length was estimated to be about 10 cm. Sheet breakup mechanisms for nozzle 2 were wave formation and sheet perforation, and the sheet length was about 20 cm. Nozzle 3 was not supposed to form a liquid sheet. Nozzle geometry was found to greatly affect spray characteristics.