PRODUCTION OF BORAX FROM SOLID ORES

The crush feed is dissolved in hot water,the siliceous gangue whch accompanies it is removed by thickening and filtration,after which the product is cropped by distillation and dried..In an attempt to obtain better borax yield and because of solubility and water conservation reasons,the process is operated in a cyclic manner..This leads to a build up of and the need to eliminate certain impurities some of which are water soluble..The ore is dissolved in a recycled weak hot mother liquor,the solution and suspended solid being passed through vbrating screens to remove the larger particle before the liquor is piped to the main gangue seperation stage which is a batttery of of six thickners.Hot dissolution is necessary because of the moderately low solubility of boraX,IN COLD WATER 5g at 20degree C rising to 191g at 100.In order to avoid pre-mature crystallization in pipe-lines and equipment,the liquors are maintained at around 100degree C during processing..This applies equally to
the gangue seperation step which are approximately about 230feet in diameter..They are operated in sequence,counter current and thickner pulp or underflows is piped to sealed tailing ponds..The clarified liquor overflow is filtered and the borax recovered as either the decahydrate or pentahydrate in struthers wells vacuum crystallizers..crystal is seperated from mother-liquor by centrifuging and the product is then dried in rotary dryers..

Borax[sodium tetraborate decahydrate NA2B4O7.10H20]  contains 47% of water..In an attempt to reduce the water content at the same time conserve energy the pentahydrate can be produced by cropping the crystals at above the transition point of 60.8 degree C.This is done without any significant increase in energy cost,water consumption is theoretically reduced also,however some liquor bleed is necessary in order to eliminate impurities..Careful routing of make-up water from all points of intoduction to final discharge via the thickner system maximizes utilization and reduces consumption..

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