High grade sodium chloride purificn. by leaching and flotation

摘要

Concn. of salt with a high percentage of NaCl, which also contains soluble and insol. impurities, comprises reducing the salt to a particle size less than 1 mm and contacting it with a soln. which is unsatd. w.r.t. the impurities, a flotation agent and finely-distributed air. In the process (a) a mashed slurry contg. flotation agent is mixed with an excess of several times of recycled soln.; (b) the slurry is passed rapidly into an annular chamber at the foot of a conical vessel, with a moving vertical central tube but no stirrer; (c) the coarsest fraction is dissolved and hydrolysed by a dwell in the bottom zone of the vessel; (d) the medium and fine particles rise into another turbulent zone in the middle of the vessel; (e) the slurry is clarified i.e. the solid is sepd. from the soln. in the top zone and the clarified soln. is discharged through an outlet pipe; (f) the pre-purified fraction sinks inside the central tube, from which fine air bubbles rise and particles of anhydrite and/or kieserite stick to these and are carried upwards, where they are removed with the froth; and (g) the purified grains are discharged at the bottom of the central tube, where a small amt. of circulating soln. enters and rises. Also claimed is the appts. used.