Question

In an orange peel industry, a fresh orange peel containing 80% water and 20% dried orange peel is dried for an hour. The orange peel going out from the dryer has a composition of: 60% orange peel and the rest is water. It is known that in the dryer, there is an evaporation of water with the rate of 100 kg water/hour (% in this problem is in weight %) a) Draw a block diagram for the process, completed with all the known variables. b) The inflow rate of orange peel going into the dryer (kg/hour) c) The output flow of orange peel leaving the dryer (kg/hour)

Answer 1

Let the inflow rate of peel = X kg/hr

Outflow of peel from dryer = Y kg/hr

Part a

Block diagram

Part b and part c

Overall mass balance

X = 100 + Y

X - Y = 100

Multiply by 0.80

0.80X - 0.80Y = 80.............eq1

Water balance

X * 0.80 = 100 + Y * 0.40

0.80X - 0.40Y = 100.................eq2

Solve eq1 and eq2 simultaneously

Eq2 - eq1

0.40Y = 20

Y = 20/0.40 = 50 kg/hr

X = 100 + Y = 100 + 50 = 150 kg/hr

The inflow rate of orange peel going into the dryer = 150 kg/hr

The output flow of orange peel leaving the dryer = 50 kg/hr

We can check our answer

Mass balance of orange peel

X*0.20 = Y*0.60

150*0.20 = 50*0.60

30 = 30

Our answer is correct