Earlier work has shown the success of a 10 day sulphite based neutral deinking trial. The neutral deinking process has now been successfully introduced into several recycle mills. Evaluation of free ink content and Lab scale studies showing the potential of this technology for the Asia-Pacific Region.
The objective of this paper is to document similarity and changes in plant operations by a survey of the recycle plant process and comparison of mill data before and after conversion. The mill survey includes information on pH, brightness, ink impairing brightness measured by ERIC, ink removal efficiency, water brightness of grey water, ash content, and solids loss at flotation. In addition, a review of each mill’s operational changes in ERIC and ISO Brightness values is made after about1year of neutral deinking.
The results found all three mills able to match or to have a similar ERIC value after flotation despite a higher ink fragmentation going into flotation. Two of the three mills were able to reach or exceed their target brightness based on average mill data. The third mill averaged within one point of the target brightness and had a lower final ERIC value. Based on these three mills it can be concluded that sulphite based neutral pulper chemistry is able to operate continuously under the varied mill operating conditions typically experienced in the industry.