Naturally occurring barium sulphate is converted into water–soluble form by heating with carbon, thus reducing the sulphate to barium sulphide (BaS). The resulting reaction mixture, “barium black ash”, contains 65% w/w soluble BaS and is to be leached with water. Black ash is to be fed to a tube mill at 100 tonnes per day, together with the overflow from the second of a cascade of thickeners, and the effluent from the mill is fed to the first thickener. All the barium is dissolved in the mill. The strong solution leaving the first thickener contains 20% w/w BaS by weight. Each thickener delivers a sludge with 1.5 kg liquid per kg of insoluble solid. Both liquids leaving each thickener are to have the same BaS concentration. BaS lost with the final sludge should not exceed 1 kg per day. How many thickeners are needed?
Naturally occurring barium sulphate is converted into water–soluble form
by heating with carbon, thus reducing the sulphate to barium sulphide
(BaS). The resulting reaction mixture, “barium black ash”, contains 65%
w/w soluble BaS and is to be leached with water. Black ash is to be fed
to a tube mill at 100 tonnes per day, together with the overflow from the
second of a cascade of thickeners, and the effluent from the mill is fed to
the first thickener. All the barium is dissolved in the mill. The strong
solution leaving the first thickener contains 20% w/w BaS by weight.
Each thickener delivers a sludge with 1.5 kg liquid per kg of insoluble
solid. Both liquids leaving each thickener are to have the same BaS
concentration. BaS lost with the final sludge should not exceed 1 kg per
day.
How many thickeners are needed?
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