GB676227A - An improved process and apparatus for the production of aqueous dispersions of finely divided sulphur and dichloro-diphenyl-trichlorethane - Google Patents

Abstract

<PICT:0676227/III/1> Concentrated dispersions of finely-divided sulphur or dichloro-diphenyl trichlorethane in aqueous media are produced by continuously passing to a disc colloid mill a slurry of the solid in water containing sulphite lye as dispersing agent, the solid having a particle size larger than 50 microns and the mill having a gap between its working surfaces of from thirty thousandths to two hundred thousandths of an inch and a relative movement of the working surfaces of from 25 to 50 metres per second, passing the milled slurry containing a substantial proportion of particles of less than 5 microns size through a cyclone separator to separate an aqueous suspension of the particles of a size less than 5 microns and recycling the residue containing the larger size particles to the mill together with fresh slurry containing a proportion of particles larger than 50 microns at such a rate that the input of fresh solid is substantially equal to the output of the solid in the finished concentrate. As shown, the solid, water and sulphite lye, are delivered from 1, 2, 3 respectively to the mixing chamber 8, and the mixture passed through colloid mill 12, then through water sprayed cooling coils 13 and finally to cyclone 9 wherein the coarse particles are separated and redischarged to chamber 8, the colloidal suspension being withdrawn through constant-head device 16 to sludge separators 14. Valves 19, 20 are provided to byepass the cyclone and recycle the mixture to the mill, in starting up the operation.