ABB introduced the KPM Retention Measurement System
, which monitors and can be used to control paper and board machine retention. Available in two options, the KRA unit measures whitewater and headbox total consistency as well as ash consistency, and the KRT unit measures total consistency only. Gaining access to continuous whitewater total consistency in- formation can help stabilize retention by controlling retention aid flow(s) accordingly. Ash consistency measurement from headbox stock enables control of ash content during sheet breaks, when ash information from the scanner is not available. The mill chose to go with both total consistency and ash content measurement in the KPM KRA system.
The mill added the KPM KRA Retention Measurement System, which also includes the KPM KC9-A optical consistency sensor and sampling systems. The system was installed on the headbox and whitewater silo on the H-2 paper machine in early 2018 and calibrated to ensure accurate measurement and control.
For the headbox unit, the sample is taken from the re- circulation line immediately after the headbox. Line pressure with strong velocity is used to move the sample through the KPM KRA unit to discharge into a sample funnel, where the actual stock sample can be collected for use in initial and ongoing calibration. The sample is then returned to the wire pit of the paper machine.
For the whitewater silo unit, the sample is taken off the bottom of the silo and uses gravity to feed the sample to the KPM KRA unit in the basement. In order to get correct measurement results, the sample goes through a dearation vessel to remove entrained air since large amounts of it will negatively affect sensor performance. The sample then flows through the KPM KC9-A sensor into a collection funnel and is returned to paper machine wire pit using a sample return pump.