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Spotlight 2003 Abstracts

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CHARCTERIZATION OF STRUCTURAL DISTRIBUTION VARIATION IN LIGHT AND MEDIUM WEIGHT PAPER
Asif Hasan and Dr. Steven Keller

DISSOLVED SOLIDS BUILDUP WITH EFFLUENT RECYCLE IN PAPERBOARD MILLS
Ashutosh Mittal and Siddharth G. Chatterjee

SHEAR THICKENING BEHAVIOR OF CONCENTRATED CALCIUM CARBONATE SUSPENSIONS
Haowen Xu and Dr. D. Steven Keller

Abstracts

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CHARCTERIZATION OF STRUCTURAL DISTRIBUTION VARIATION IN LIGHT AND MEDIUM WEIGHT PAPER
Asif Hasan and Dr. Steven Keller ,Faculty of Paper Science Engineering, SUNY College of Environmental Science and Forestry, Syracuse, NY13210.

Non-uniformity defects may occur in paper and paperboard as a result of the hydrodynamics in the headbox and forming zone of a paper machine. Since their occurrence is related to the machine speed, streaks may appear stationary or mobile, they may be intermittent or continuous and may occur at regular or irregular intervals across the machine width. For this reason, there is substantial interest in characterizing the various forms of streaks (not limited to grammage variation), identify their location, determine their origin from the location and periodicity and provide preventive measures. A novel approach by Kellomaki, Keller , Pawlak and Sung [1] was able to separating the static and stochastic components of spatial variability data and thus provide information about the scale of features, e.g. flocs or streaks, as function of position within the data array in one direction. Due to potential for intermittence, localization of spatial variability data in 2 dimensional space is advantageous in detection and taking preventive measure. A procedure has been developed here to demonstrate continuous analysis with a movable and size adjustable sampling window that travels to encompass the data in the Machine direction in a real paper machine scenario is not only possible, but also desirable to understand the paper variability. Characterization of streaks has been furthered by a clear cut separation of the floccy from the light weight zones through a bipolar, color representation. On the other hand decision making is made simpler by appropriate thresholding of the analyzed data. An user interface to accomplish the above is underway.

1. Kellomaki, Markku., Pawlak, Joel. J., Sung, Yong-Joo., and Keller , D. Steven., “Characterization of Non-stationery Structural Non-uniformities in Paper,” in the12 th fundamental Research Symposium Keble College, Oxford, UK(2001).

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DISSOLVED SOLIDS BUILDUP WITH EFFLUENT RECYCLE IN PAPERBOARD MILLS
Ashutosh Mittal
Graduate Student (M.S.) Paper Science and Engineering, SUNY College of Environmental Science and Forestry, Syracuse, NY 13210.
Siddharth G. Chatterjee
Faculty of Paper Science and Engineering, SUNY ESF.

The present climate of increasingly stringent effluent regulations is causing recovered or secondary fiber mills to consider closure of their process water system. Over the last two decades significant efforts have been made to control water use and pollution by paper and board mills. The incentives for closing the mill water system are: reduced freshwater consumption, reduced loss of fiber, fines and filler, decreased chemical and energy consumption, and better environmental compliance. Closing of the white water system can lead to higher levels of suspended and dissolved solids, increased temperature, and reduced dissolved oxygen.

The effects of effluent closure in a linerboard mill using 100% recycled old corrugated containers were studied.  Samples were taken at various locations in the mill and critical substances i.e. calcium, magnesium, sodium, silica, chloride and sulfate were tested for at two different recycle rates. Mass balance were performed on the input and output streams and a mathematical model was developed to predict enrichment factor (EF) or dissolved solids buildup for the different species (critical substances) at increasing effluent recycle rates. The theoretical and experimental enrichment factors were found to be in good agreement.

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SHEAR THICKENING BEHAVIOR OF CONCENTRATED CALCIUM CARBONATE SUSPENSIONS
Haowen Xu and Dr. D. Steven Keller ,Faculty of Paper Science and Engineering, SUNY College of Environmental Science and Forestry, Syracuse, NY13210.

The rheological properties of dispersed concentrated suspensions of calcium carbonate were examined in order to determine the significance of transient shear thickening and its dependence on particle size distribution. A polydisperse suspension with particle size range from 0.2 to 10um was classified by centrifuge into several narrower size fractions.  The characteristics of the particle size distribution were controlled by blending concentrations of the narrower size fractions in order to affect the maximum packing values as calculated by using Lee ’s method [1]. The effect of size fraction concentration and the resulting packing factor on the rheology were studied at high solid contents using a rotational viscometer with Couette geometry. In the low shear rate region, shear thinning behavior was observed and was enhanced by increasing small fractions of blends. At shear rates within the shear thickening transition, the fine particle size fraction significantly reduces the viscosity and mitigates the onset of shear thickening within the range of shear rates measured. For blends of particles, a minimum in relative high shear rate limiting viscosity was observed in the range of 30-40% by volume of finer size particles. Transient rheological behavior in the shear thickening region was also studied in detail. From experiments conducted at constant shear rate, a reversible time-dependent antithixtropic phenomenon (shear stress increase with time) was observed when the fluid was sheared near the limits of dilatancy. Transient curves that exhibited antithixotropy were divided into three regions and described by empirical parameters. Quantitative relationships were found between these parameters and the rate of constant shear, solid contents, particle size distribution and packing. It was hypothesized that the increase of stress with time suggests the time evolution of flow-induced structures in the shear thickening transition within the shear zone. The results favor the transient cluster formation mechanism of the existing shear thickening theory.

[1] Do Ik Lee , J.Paint Technol., 42(550), 579-587 (1970).


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