Gravity-desliming using cascading REFLUX™ Classifiers at full-scale

Abstract

ABSTRACT A cascading sequence of two full-scale REFLUX™ Classifiers was tested using 1.0 mm top size coal. The gravity separation in the first stage gave a clean coal product down to about 0.03 mm. The second stage then deslimed this product with minimal coal loss. At volumetric feed rates up to roughly 100 m3/h (~ 50 t/h solids), 30–50 wt.% ash feeds were reliably cleaned to give product ash values less than 10 wt.% at overall combustible recoveries of 60–80 %. At higher feed rates up to 240 m3/h (~ 100 t/h solids), product ash values were in the range 8–13 wt.% at 43–67% combustible recovery. One run processed 150 m3/h of a very problematic high-slimes feed with 35 wt.% -0.038 mm slimes and 52 wt.% head ash, giving a 14 wt.% ash product at 56% combustible recovery. The deslime unit size partition Ep values increased exponentially with overflow rate, but remained less than 0.05 mm for overflow rates up to 100 m3/h. The cut point size increased with the deslime unit overflow flux. When the effects of cut point density and hindered settling were accounted for, there was good agreement with previous laboratory and pilot-scale test work.