EFFECTS OF HOT DISPERSION ON THE PROPERTIES OF DEINKED PULP

摘要

From a literature review, it is apparent that although hot dispersion is an integral unit of the deinking process, there has been no systematic study of the effects of pulp consistency and operational temperature on the physical and optical properties of the resulting paper. In this study, we used a mill-site hot dispersion system to treat computer forms and examined the effects of different operational temperatures and pulp consistencies on resultant handsheet properties. Operational temperatures were controlled at 90, 100, 110, and 115 degrees C and pulp consistencies at 19%, 32%, 35%, and 36%. The pulp freeness was measured, and the tensile strength, burst index, tear strength, stiffness, brightness, whiteness, opacity, and light scattering coefficient of the handsheets were parameters of interest. Results indicated that when operated at consistencies of >32%, the temperature effects were more significant than the consistency effects. At 110 degrees C, the highest pulp freeness, handsheet tear strength, whiteness opacity, and light scattering were obtained. When operating at 100 degrees C, the highest handsheet tensile strength, stiffness, and coefficient of absorption were obtained; at 90 degrees C, the highest handsheet burst index was produced; and at 115 degrees C, the highest handsheet brightness was engendered. With regard to consistency, at 35%, the highest handsheet burst index was reached. All other properties examined showed no significant correlation with pulp consistency. In summary, hot dispersion should be operated at temperatures of 100-110 degrees C, and consistencies of >32%.