RELIABLE CONSISTENCY MEASUREMENT WITHOUT REBUILDING YOUR PULP-MILL - A MILL EXPERIENCE

Consistency measurement is infinitely more an art than a science; most instrument technicians would say it is more like a dart game! There a re several different instrument manufacturers, with a variety of measu rement methods and all claim to be able to measure and produce repeata ble measurements of consistency. (Most have a disclaimer stating the a pplication must have adequate installation conditions to maintain lami nar flow and low flow velocities.) This paper addresses the trials run on an existing hardwood unbleached medium-consistency (3-4.5%) kraft pulp stock line with high flow velocities and turbulent flow. The cons istency was measured with a blade-style sensor, and the process was un able to be run on automatic-consistency control. Results of the trial showed that repeatable manual-consistency samples could be obtained (a n average repeatability of 2.9% was measured over 1 year of sampling). It was also shown that compensation curves can be created in the dist ributed control system to give a reliable, compensated continuous cons istency measurement for dependable automatic-consistency control (the loop was able to put on automatic control).