GB467543A - Improvements in or relating to the manufacture of magnesium hydroxide - Google Patents

Abstract

<PICT:0467543/III/1> <PICT:0467543/III/2> In the manufacture of magnesium hydroxide from dilute brines such as ocean water, a stream of unclarified milk of lime is delivered into a stream of the brine with gentle agitation and under controlled conditions with respect to rate of flow whereby agglomerated flocks of highly hydrated magnesium hydroxide are formed and maintained, the combined stream carrying the flocks passing into a quiescent body of mother liquor to effect settling of the flocks. As shown in Fig. 1, lime to be used in the process is slaked with water in apparatus comprising a mixing vessel 6, retention vessel 8, and final mixing-tank 13. This arrangement prevents the growth of large crystals of calcium hydroxide. The slurry is diluted in a tank 19 with water or treated brine until it contains 0,3 to 0,5 lb. CaO per gallon, is subjected to hydraulic classification in tower 23 and further purified by screening in device 27. The purified slurry is then delivered to the mixing chamber 31 disposed in the settling chamber 32. Raw brine may be treated in tank 36 with the matter rejected from tower 23 and screening device 27 and with alum in tank 42, before being filtered in filter 44 and passed to the mixing chamber 31. As shown in Fig. 2, the mixing chamber is located below the level 45 of liquid in the tank 32. Milk of lime is supplied through a pipe 47, and brine through a pipe 48 to a pipe 46 surrounding the pipe 47, a baffle 49 being provided to ensure an even downward flow from the lower end of pipe 46. The distance between the lower end of pipe 47 and that of pipe 46 may be varied to ensure proper mixing of the reactants.