Measurement of Dispersed Air in Newsprint Pulp Suspensions, 1991 Papermakers Conference Proceedings

Two approaches for applying vibrating U-tube densitometers to the measurement of the amount of dispersed air in newsprint pulp suspensions were investigated, both in laboratory and in pilot-plant conditions, and the results compared favorably with the data from the PAPEC Process Air Measurment (PAM) commercial sensor.

In the first approach, stock density was monitored as a function of time. Density variations were attributed to changes in the content of dispersed air. To calculate absolute volume fractions of air, values were needed for densities and concentrations of fiber and fillers. In the second approach, densities were measured at two pressures; this permitted direct calculation of dispersed air content.

The results from the densitometer correlated well with those from the PAM for air contents ranging from 0 to 5 % by volume. Data from both instruments showed that the air content fluctuated by as much as +0.5 volume percent in a ten second interval in our pilot flow loop.