Improvements in recovery efficiency at Cleveland Potash

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.