The first delivery of potassium chloride product from Cleveland Potash's Bo
ulby mine on the northeast coast of England took place in 1973. The feed to
the process plant has a typical grade of 38% KCl, 51% NaCl and 11% insolub
le minerals. The flowsheet is outlined and it is noted that the KCl recover
y efficiency has declined over the past four years owing to a reduced KCl c
ontent of the mine brine used for slurry make-up, higher levels of insolubl
e clay in the ore and a greater variability of the ore. To increase the rec
overy of saturated brine in particular, from flotation tailings-a 60-m(2) h
orizontal belt vacuum filter is now being commissioned. The new filter also
serves to reduce the solid KCl content of the cake by countercurrent washi
ng. To optimize the efficiency of the belt filtration it is proposed to fir
st thicken the feed slurry by introducing classification of the coarse flot
ation tailings by cyclones in combination with the use of a thickener-clari
fier.