Application of Specialty Chemicals with Microprocessor Based Control Systems, 1990 TAPPI Conference Proceedings

The performance of specialty chemicals is critical to the smooth operation of pulp and paper mills. The importance of accurate chemical control to achieve optimum performance is discussed as well as factors that introduce variation and error into applications. A chemical feed system is introduced that overcomes the limitations of manual adjustment and conventional proportional control by performing continuous, on-line pump calibration and correction. The new chemical feed controller proportions chemical feed rate to a primary signal (such as flow) and adjusts the feed rate based on a secondary signal (such as temperature). To assure accurate feed control, the unit continually measures pump output, which can vary greatly as process conditions change, and corrects pump speed or stroke to compensate for pump output variations. Data illustrating chemical pump output variation as a function of several variables are presented. Specific examples of applications of this new feed system are discussed.