Mitigating pitch-related deposits at a thermomechanical pulp-based specialty paper mill

Abstract

A mill in Eastern Canada experienced significant sticky deposit formation on one of the guide rolls of the supercalendering stack in its supercalendered paper production line. To investigate, and minimize, the formation of those sticky deposits, we collected deposit samples from a supercalender stack and analyzed them for their chemical compositions, metal ion contents, and thermal properties. Acetone soluble substances, which were considered as pitch or wood extractives, were shown to account for the majority of these deposit samples. The thermogravimetric analyzer gave the result that, for the deposit sample, the mass loss due to heating in the temperature range of 50ºC–200ºC was less than 5%. Gas chromatography results showed similar chemistry for the deposit samples both before and after the thermogravimetric analyzer analysis. Throughout the mill process, a large portion of wood extractives passed through the thermomechanical pulp mill and into the paper mill with the pulp streams. Two control programs, detackification versus fixation, were compared to evaluate their ability to decrease the extractives-related deposit formation on the supercalendering stack.