Active Retention Control and Reduced Ash Variability using Advanced Process Control, PaperCon2017
Retention management is critical for maintaining the wet end stability of paper machines and theretention level is decided based on the paper grade being produced as well as economic objectives. Thedesired retention is achieved through the addition of chemicals such as retention aids, polymers as wellas fillers with clay content. It is also desirable to maintain a consistent ash content and limit its variabilityso as to improve the machine runnability. While high retention levels are preferred, chemical costs anddesired paper quality constrain the addition of chemicals. ABB’s advanced process control (APC) forretention solves this constrained multivariable control problem by optimally dosing the chemicals,thereby achieving the required retention and stable ash. In this paper, we present this APC scheme anddemonstrate its efficacy through results obtained from an Indonesian paper mill. The APC solution,implemented on ABB’s 800xA APC platform, was able to achieve a 10% reduction in clay dosage, 15%reduction in polymer dosage and a 20% reduction in the retention chemicals dosage, resulting insubstantially lower annual production costs. The ash content was also stabilized, which significantlyreduced the down time due to sheet breaks.
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