Applying automatic chemical control from stock prep to the machine

摘要

Controlling consistency in the pulping and bleach plant sectors is done according to certain well-defined standards, and gives accurate and reliable results. Consistency remains an essential and basic parameter that must be controlled to ensure process performance. At the paper machine, white water consistency control has been accepted as an industry standard. This control strategy is well known and has proven efficient and beneficial. Now, we are advancing wet end control to the next level. Combining retention aid control and charge demand control with coagulant or fixative in the thick-stock area provides additional benefits. Retention aid control by Whitewater consistency was developed in parallel with charge demand control. The advances in charge control are mainly thanks to sustained efforts of Mutek Analytic, an international lab instrument supplier. Developing this type of control has lead the industry to a much better understanding of charge demand and the impact of charge variation on retention aid efficiency. It is important to understand that all chemicals used in the pulp and paper manufacturing process affect paper machine runnability and performance. Chemicals used for bleaching often carry over to the wet end, disturbing the final performance of retention aid, dye, coagulant and wet/dry strength chemicals. This paper attempts to impart further understanding in the area of wet end chemistry control. New results are presented for both retention control and charge control, and to bridge the gap between the two control concepts.