Green Lime - Green liquor dregs in flotation

The commonly used pH-raising substances are mined as primary raw materials from the bedrock and as such are almost too good to be used in raising the pH of mine concentrators. Most often, to raise the pH, either slaked or burnt lime is used, the production of which generates considerable carbon dioxide emissions when calcium carbonates break down into calcium oxides and carbon dioxide. Based on the patented invention of the University of Oulu and XAMK researchers, these primary raw materials were replaced with the last significant type of waste from the pulp industry, green liquor dregs.

The goal of this project is to develop the pretreatment and use of green liquor dregs as a pH regulator in the flotation process. Further development takes place with an extensive research and business consortium cooperation. It includes New Boliden's Kevitsa mine and Sotkamo Silver's silver mine as potential users. In preliminary tests, the processes of these mines have been found to be suitable for the utilization of green liquor dregs. They also correspond very well to the most typical Finnish ores. Stora Enso, Metsä Fiber and UPM are suppliers of the green liquor dregs samples. As early operators, they also have the best knowledge of the quality variations of green liquor dregs.

To ensure the functionality of the pre-treated green liquor dregs, a considerable amount of laboratory flotations and continuous pilot tests are carried out. Their purpose is to ensure the functionality of green liquor dregs compared to burnt lime, and to generate information about any necessary changes to balance the process. Studying the effect of green liquor dregs of the dosage of flotation chemicals is specially under observation.