Reduction of alkali loss in  an ash leaching system, TAPPI JOURNAL July 2017

ABSTRACT: There are many points in a kraft mill where the alkaline compounds are purged from the process. Several effluents, solid waste, and air emissions contain alkali, which leads to the necessity of chemical makeups to maintain the liquor balance. The main loss of alkali at the Veracel mill is present in the wastewater from the recovery boiler; more precisely, it is from the ash leaching system, which represents 80% of the total losses. 


To minimize the alkaline losses while keeping the chloride level in the recovery cycle under control, a project was developed at Veracel. Key actions were taken by adjusting the control loops of the ash leaching system, mainly on he slurry density and purge control. These adjustments led to a decrease in alkali losses and to an increase of treated ash, and kept the chloride level of the recovery boiler dust at 2.6%.

Application: This research demonstrates how alkaline losses can be reduced by automation solutions in the ash leaching system.

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