ECH51PracticeExam1_08

# Data given 1 mol 00224 m 3 h stp l r a 0791 g ? cm 3

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Data given: 1 mol =0.0224 m 3 H STP L , r A = 0.791 g ë cm 3 , A = 58.0 g ê mol Problem 3 The flowchart of a steady-state process to recover crystalline potassium chromate ( K 2 CrO 4 ) from an aqueous solution of this salt is shown in Fig 1. The feed stream (#1) is 4500 kg/hr of a solution that is one third K 2 Cr0 4 by mass. It is mixed with a recycle stream #6 and then fed to an evaporator unit. The vapor stream #3 leaving the evaporator is pure water. The liquid stream #4 leaving the evaporator contains 49.4% by mass K 2 CrO 4 . It is fed into a crystallizer/filter where it is cooled (causing crystals of K 2 CrO 4 to come out of solution) and then filtered. Stream #5 leaving the crystallizer/filter unit is a filter cake suspension consist- ing of the filter cake (pure K 2 CrO 4 crystals) and some residual solution that contains 36.4% K 2 CrO 4 by mass. The mass flow rate of the filter cake suspension is m ° 5 = m ° crys + m ° res where m ° crys is the mass flow rate of filter cake and m ° res is the mass flow rate of the residual solution in the filter cake suspension. The flow rate m ° crys accounts for 90% of the total mass of stream #5. The solution that passes through the filter ( stream #6) is recycled back to the evaporator; it contains 36.4% by mass K 2 CrO 4 . ECH51PracticeExam1_08.nb 3

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Figure 3 Calculate the rate of evaporation, the rate of production of crystalline K 2 CrO 4 , the feed rates to the evaporator and crystallizer, and the recycle ratio (mass flow rate of recycle)/(mass flow rate of fresh feed) Problem 4 Titanium dioxide, TiO 2 is a white pigment used in the paint and paper industries. A new pigment plant processes
• Fall '13
• Brian
• Fluid Dynamics, stream, Mass flow rate, Orifice plate

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