Conical vs Double Disk Refining Technology Evaluations and the Effects on Energy Consumption and Physical Paper Properties of High Yield Southern Softwood, TAPPICon25

As the paper industry ages, many mills look not only to update their machinery, but also to gain an understanding of the newer technology. An example of this is pulp refining technology. Two of the most widely used refiner technologies used globally are categorized by the shape of the machinery, mainly conical refiners, and double disk refiners. Although double disk refiners dominate in North America, an emerging presence or at least interest in the newer flow through conical refining design is of recent interest.

This paper attempts to investigate the similarities and differences seen between some of the newest conical and double disk refiner technology, namely Valmet’s OptiFiner PRO and DD6700 series refiners on the influence of high yield southern softwood for the purpose of unbleached linerboard and kraft bag production. Energy efficiency and good strength development are high on the list as the industry focuses on reducing the carbon footprint and achieving more strength with less fiber. A good fundamental understanding of refining technologies and pilot techniques to include one pass versus batch mode evaluations will be presented.

Energy input versus typical linerboard properties development will be shared along with relevant fiber development properties for freeness, fiber morphology, and water retention values (WRV). Some diverging properties were seen because of the experimental conditions chosen but did not reach statistical significance until much higher energy on fiber had been accumulated. Traditional specific edge load (SEL) theory was the basis for setting up the comparison of the refining technologies while other refining theories such as C-factor theory were later considered in the analysis to account for refiner geometry and the number and intensity of impacts to explain the results.

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