Ash Content of Containerboard. Problems and Solutions

This article covers the study of the nature of ash content of containerboard from waste paper, as well as fractional composition of ash. With increasing use of waste paper with white top layer and deterioration of conditions of collecting and storing waste paper at the storing fields, there is an increase in mineral impurities in the incoming waste paper. This fact leads to increased load on cleaning equipment and accelerated wear of working parts of sorters and mills. Ash content includes all mineral impurities without any division into fractions or sources of occurrence. Reducing the total ash content of products becomes quite difficult, because suppliers of cleaning equipment guarantee the efficiency of removing only those mineral contaminants, the size of which is greater than the a certain value (70…100 microns). Standard methods for determining ash content of paper and cardboard do not imply the possibility of determining the fractional composition. To solve this problem, the authors applied a method for determining the fractional composition of granular materials in a certified laboratory. The method of sample preparation for analysis was developed by the authors independently. Based on the results of the research, it was possible to identify the volume of the ash fraction that can be separated by means of cleaning equipment. This volume is mainly quartz sand of various degrees of grinding, and the other part of ash content is the filler, calcium carbonate, which cannot be effectively removed from the technical process due to the small particle size. To determine the content of calcium carbonate, qualitative and quantitative research methods were used - treatment with hydrochloric acid followed by washing and weighing of the resulting sludge. This test methodology and the results of the research work can serve as a basis for the need to install additional or upgrade the existing cleaning equipment. Unfortunately, at present there are no studies concerning abrasive ability of the main filler – calcium carbonate, and its influence on service life of the corrugator. Also, at the moment there are no data concerning critical size of ash particles, which lead to accelerated wear of the rolls. At the same time, determination of critical particle size is important from the point of view of setting up and upgrading of cleaning equipment of the stock preparation department of a typical paper mill processing waste paper raw materials. For citation: Zhirnov D.N., Dernova E.V., Gorazdova V.V., Dulkin D.A. Ash Content of Containerboard. Problems and Solutions. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 5, pp. 184–194. (In Russ.). https://doi.org/10.37482/0536-1036-2023-5-184-194