Energy Savings With Embedded Solutions, 2007 TAPPI Papermakers and PIMA International Leadership Conference

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Almost the entire paper machine is devoted to the removal of water, changing the stock from about 99% water to just 5% water. The traditional approach has been to wait until the end of the process to measure the water content and see if you got it right. The industry has done surprisingly well with this approach by making incremental sensing improvements over the past 40 years. To make further significant improvements, however, measurements are required throughout the machine to determine more exactly the source of disturbances and more accurately control all of the actuators that have an impact on water content in a coordinated fashion.

Since evaporation uses about 90% of the papermaking energy but only removes about 50% of the moisture, every effort must be made to maximize mechanical water removal. The next highest priority is to reduce moisture variations, particularly in the cross direction, but also the machine direction, as this allows the machine to run closer to the upper moisture limit without breaching product specifications, saving more energy. This paper describes the energy savings associated with the different types of measurements incorporated into the embedded solutions approach to the control of water removal (and re-wetting) during papermaking. The benefits of water weight sensors embedded into forming foils, followed by moisture measurements placed throughout the wet-press and dryers, followed by measurements of coating consolidation for coated grades will be discussed.