Seasonal impacts on the performance of AQ and AQ/penetrants

Abstract

The performance of AQ and AQ/penetrant appears to vary depending upon the time of year in which the mill trials are conducted. Mill data have shown that increased amounts of white liquor are required during the late winter through the early spring months for mills employing standard kraft cooking and for mills using digest-er additives in the cooking process. Seasonal white liquor variation was found to be 0.7% effective alkalai (EA) on wood for the standard kraft process. Seasonal liquor variation was found to be 0.8% and 0.4% EA on wood for mills employing AQ and AQ/penetrants, respectively. These seasonal changes may account for as much as 95% of the expected benefit associated with using a digester additive. Thus, when summer or fall mill operating conditions are used in a laboratory study or as a baseline for a comparative mill study, the performance of the digester additive would be reported as substandard or nonfunctional for trials conducted in the late winter or early fall.