Particle Technology
PRY317B
Assignment 3.
Due date: 26/04/2022
Lecturer: Prof. R.K.K.Mbaya
Total marks 50
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QUESTION1 (10 marks)
Drying process is important in chemical and food industries explain why?
QUESTION2 (15 marks)
A wet solid is to be dried in a tray dryer under steady-state conditions from a free moisture content
of X1 = 040 kg H2O/kg dry solid to X2 = 0.02 kg H2O/kg dry solid. The dry solid weight is 99, 8
kg dry solid and the top surface area for drying is 5.8 m2. The drying-rate curve can be represented
by figure shown below, calculate the time for drying using graphical integration in the falling rate
period.
QUESTION3 (5 marks)
Give a brief explanation why membrane technology is an important process in water treatment
QUESTION4 (20 marks)
An engineer wants to design a reverse-osmosis plant to recover 33% of the seawater feed water
as portable water. The permeate pressure is a 1/6 of the feed side pressure. The total spiral wound
membrane surface area is 250000 m2 for a single stage crossflow. Calculate the salt passage and
water permeance given the characteristic of the feed water, permeate and final brine as in table
below.
Feed
Permeate
Brine
(retentate)
Flow rate
130,35 m3
Concentration
40000 ppm
500 ppm
65000 ppm
Pressure
150 atm