New method for measuring potential secondary stickies in deinked pulp filtrates

Secondary stickies refer to sticky material in recycled fiber process streams, which has been dissolved in one part of process, but turned to solid phase due to changes in process conditions. The material that can later form secondary stickies is called potential secondary stickies. A new, fast, and simple method for measuring the amount of potential secondary stickies was developed to measure the purification result in the deinked pulp (DIP) filtrates. The new method, now called potential secondary stickies method, was tested with process waters from a recycled fiber (RCF) plant. The method was found to be reliable. Several chemicals and chemical combinations were tested in laboratory scale and compared as coagulation-flocculation agents in two dissolved air flotations (DAF) used as internal water treatment units at the RCF plant. With potential secondary stickies method, significant differences between the effectiveness of the chemicals were found, whereas no difference was seen in the quality of purified process water with traditional measuring methods. The measurement method was also used in mill during a two-week measuring period. As a conclusion, it can be said that this method can be used to monitor the quality and to predict the changes in DIP process water.