{'fraction_non_alphanumeric': 0.0178988326848249, 'fraction_numerical': 0.010505836575875487, 'mean_word_length': 4.803611738148984, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Investigation of pulp dewatering – relating freeness to filtration properties

For Sweden the forest sector is of great importance and contributes significantly to the Swedish export. One of the most important products is pulp, which can be used for production of packing material, printing paper and tissue paper. Pulp is also produced in several other countries (e.g. Finland, Canada and Brazil) and the world production is around 180 million tons during 2010. There are several different methods used for pulp production, both mechanical and chemical methods can be used. Among the chemical methods the kraft process is the most common. One important product based on pulp is paper. Paper is formed by dewatering a mix of pulp and additives, to achieve a proper formation the starting pulp needs to be severely diluted, consistency as low as 0.1 % is required to form a paper of a good and even quality. The formation of the paper takes place on a wire section, where large amounts of water are removed by filtration. Further dewatering is then performed in the pressing section and finally the paper is dried. In the industry the dewatering properties of the pulp are measured using simple equipment measuring the freeness of the pulp, normally no filtration properties are measured. The goal for this study has been to investigate pulp dewatering behaviour and relate freeness measurements to measured filtration properties. The fibres used in this study are produced in a kraft process based on softwood material To investigate how the filtration properties change with the dewatering rate, the pulp was treated in a PFI-mill to change the structure on the pulp and thus the dewatering rate. The dewaterbility was measured using two industrial methods Canadian standard freeness (CSF) and Schopper-Riegler (SR). The filtration resistance of the pulp was also measured at 1 bar filtration pressure. A model for CSF from the literature was used to compare a theoretical relation between freeness values and specific filtration resistance and the relation found from the filtration experiments in this study. The range of the freeness value of the processed pulp was from 695 ml to 125 ml for CSF, which corresponds to a specific filtration resistance of 9×10 9 m/kg to 7.7×10 12 m/kg at 1 bar filtration pressure. The model for CSF indicated lower filtration resistances than the ones measured in the experiments. An important explanation for this is the difference in filtration pressure and with the following difference in compression of the filter cake. Table of