Reduction of Paper Pulp Fluctuations in Tissue Paper Making Machine

Abstract

The subject of the research is a paper for sanitary-hygienic purposes. The objects of the study are a pulper infeed system and a round grid perforated forming device. The purposes of the work are to identify sources and reduce fluctuations of 1 m2 of pulp for sanitaryhygienic paper, which decrease the structural irregularities of the paper web in longitudinal and transverse directions. The methodology of the study is to investigate the flow pulsation of the pulp, the fluctuations of the pulp web at the Yankee cylinder (without crepe), to verify the tensile strength of the paper web in longitudinal and transverse directions for identification of a correlation between the pulsation, the vibration of the pulp and the strength of the paper web. The trials were made during the production of sanitary-hygienic paper with the mass 17–18 g/m2 at a steady working speed of the machine 5 m/s. Pulsations of paper pulp in the low-frequency spectrum of 0.14–1.35 Hz prevail in the mass-intake device. The rectangular paper samples 432×230 mm2 were created for examination of structural irregularities of the paper web. The length 432 mm was taken in the longitudinal direction of paper movement in the machine. It was equal to 0.125 mm in the circumference of the round grid screen cylinder. The width of the paper web in the commodity bobbin was 230 mm. The samples were made from a single sheet of paper sequentially without intermediate cuts at 5 m/s speed of the machine. It was determined that the frequencies of fluctuations of the masses of sanitary paper samples coincide by 86 % with the pulsation frequencies of the pulp and depend on other factors by 14 %. The major frequency was 1.45 Hz. The amplitude of the deviation of the mass at this frequency from the arithmetic mean was 0.026 g. The tensile strength of the paper web in the machine direction was 5.6 times greater than in the transverse direction. It was caused by unregulated rotation frequency of the holey roll and clogging of its holes. The significant change of speed of the pulp flow on the short cylindrical part of the vacuum chambers initiated synchronically low frequency pulsation of the pulp and fluctuations of masses of the paper samples, therefor, the paper web in the machine. The irregularities of the structure of the paper web create the frequent paper breaks and reduced quality of the commodity products.