Method Development for Evaluating Pitch Dispersing Agents Used in the Kraft Pulping Process

Abstract: Depending on wood species and the extractives of the wood, the paper and pulp processes might suffer from problems caused by the formation of pitch deposits from calcium soaps. BIM Kemi is a specialty chemical producer supplying the pulp and paper industry with dispersing agents, which prevent these problems. The objective of this thesis was to develop an in-house laboratory method for evaluating novel pitch dispersing agents. The resulting method aimed to be quantitative, have a high repeatability and higher accuracy than the current method used at BIM Kemi, which suffered from statistical variations and subjective interpretation. A filtration method and a plastic film method were developed in conditions simulating the kraft process and tested on birch pitch. The filtration method captured the aggregated pitch deposits when removing the filter, and the weight of the deposits could then be quantified and compared. The plastic film method captured pitch deposits on the film, which was scanned for image-analysis to quantify area and amounts of deposits that had attached. Both methods quantitively compared a reference test to a product test in order to evaluate the efficiency of the product in the methods. This thesis shows that a promising method for evaluating dispersing agents was filtration with a filter bag in polyester material. It gave quantitative results and had the lowest standard deviation of all method set-ups.