Titanium dioxide, which is the most common white pigment in paint, can be produced from the titanium mineral, rutile, by chlorination to TiCl4, followed by oxidation to TiO2. To purify the insoluble titanium dioxide, it is washed free of soluble impurities in a continuous, countercurrent system of thickeners with water. Two hundred thousand kg/h of 99.9 wt% titanium dioxide pigment is to be produced by washing, followed by filtering and drying. The feed contains 50 wt% TiO2, 20 wt% soluble salts and 30 wt% water. The wash liquid is pure water at a flow rate equal to that of the feed on a mass flow basis.
Titanium dioxide, which is the most common white pigment in paint, can be produced from the titanium mineral, rutile, by chlorination to TiCl4, followed by oxidation to TiO2. To purify the insoluble titanium dioxide, it is washed free of soluble impurities in a continuous, countercurrent system of thickeners with water. Two hundred thousand kg/h of 99.9 wt% titanium dioxide pigment is to be produced by washing, followed by filtering and drying. The feed contains 50 wt% TiO2, 20 wt% soluble salts and 30 wt% water. The wash liquid is pure water at a flow rate equal to that of the feed on a mass flow basis. Use the McCabe-Smith method to determine the number of ideal stages required if the underflow is variable as follows:
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