MEASUREMENT OF PULP RESIDENCE TIME IN A HIGH-CONSISTENCY REFINER

This paper describes a system that was developed to measure pulp resid ence lime at high consistency in a laboratory disc refiner. The techni que uses a series of fibre optic probes positioned around the inner an d outer radii of the refiner stator disc. Light is brought to each pro be through a series of small fibre optic strands positioned around a l arger central strand that picks up light reflected by material in fron t of the probe. The refiner is alternately fed with black-dyed and ble ached pulp. A change in reflectance is measured as the dyed pulp passe s the probes at the inner and outer radii. By computing the cross-corr elation between the two signals, we find the delay between them, which corresponds to the residence time in the refining zone. Measured valu es were compared to theoretical estimates based on Miles and May's the ory [1] and were always found to be larger than predicted by the theor y.