Level and solids profile detection in thickeners using conductivity
Solids concentration (weight % solids) profiles and the clear liquid/slurry interface level (mud-line) were determined from conductivity measurements in thickeners at Falconbridge's Strathcona mill (Ni concentrate and non-mag thickeners) and Kidd Creek Division (Cu, Zn concentrates and final tails in the concentrator and a jarosite thickener in the Zn plant). The conductivity measurement system consisted of a probe 1.5 m in length with 23 electrode cells, a 24-channel relay, a conductivity meter and a computer. A conductivity profile is collected which locates the mud-line by a sharp change in conductivity. The conductivity measurements are readily converted to solids concentration profiles using a model due to Maxwell. The results from conductivity measurements were compared with direct measurements on local samples obtained using a modified Noranda sampler. It is concluded that the conductivity technique is applicable to locate the mud-line and to estimate the solids concentration profiles in thickeners. This on-line information could improve the operational efficiency of industrial thickeners.