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you have a mixture of quartz and pyrite (FeS) particles, that range in size from

ID: 511918 • Letter: Y

Question

you have a mixture of quartz and pyrite (FeS) particles, that range in size from 10 to 300 micro m. The SG of quartz is 2.65 and the SG of pyrite is 5.1. You wish to investigate several

different mechanical unit operations to remove or separate these particles.

Design a gravity sedimentation tank to clean these particles from a 6.3 m^3/s water stream. The tank is rectangular, measuring 3 m wide and 2 m deep. The dirty water is

introduced at one end of the tank, with clean water flowing out of the other end. How

long must this tank be?

b)You wish to separate the quartz and pyrite. One method is to use hydraulic

classification. What would be the size range of the pure quartz fraction?

c) You would like to vary the liquid medium density to obtain two pure fractions of pyrite and quartz.

What liquid medium density would achieve this?

Explanation / Answer

a). In 1 sec, the volume of water stream cleaning the sedimentation tank = 6.3 m3

Volume of the sedimenation tank = Volume of the water stream crossing the tank in 1 sec

Length * Width * Depth = 6.3 m3

Length * 3 * 2 = 6.3

Length = 6.3 / (3*2)

Length = 1.02 m

b). Size range of the quartz particles should be between 10 to 300 micro m

c). Liquid medium density to obtain two pure fractions of pyrite and quartz should be in the range of 2.65 and 5.0

so that quartz is washed off and pyrite particles being heavier are left behind.