Evaluation of a Capillary-Coriolis Instrument for On-Line Viscosity and Density Measurements of Kraft Black Liquor, 1997 Process Control, Electrical & Info. Conference Proceedings

A capillary-coriolis instrument featuring sealed pressure diaphragms connected to a differential pressure cell was evaluated as an on-line viscometer and density meter for kraft black liquor. The instrument was installed in a pilot plant where liquor could be circulated in a flow loop with the solids concentration, temperature, and flow rate of the liquor closely controlled. Measurements were made under laminar flow conditions for liquors with solids concentrations ranging from 42% to 75%, and temperatures up to 140° C, with particulates included in the liquor in some cases. The accuracy and precision of the instrument were determined by comparison with lab measurements of viscosity and density made under laboratory conditions. The instrument capabilities, limitations, repeatability, and response time were determined for a wide range of operating conditions. An experimental test in an industrial pulping mill has been arranged to determine reliability and durability in an industrial environment for an extended period of time, and to determine the best use of the instrument for monitoring and control purposes.