Flash Distillation P1

Question 1

What type of process is Flash Distillation

Answer 1

a single-stage phase-creation process

Question 2

What are the two typical types of flash distillation

Answer 2

1. Liquid feed partially vaporising
2. Vapour feed partially condensing
   These are both two phase mixtures

Question 3

Label a single-stage flash unit

Answer 3

Look at picture

Question 4

What do F, Tf, Pf and Q represent?

Answer 4

F= molar flow rate of feed stream
Tf= Temp of feed stream
Pf=Pressure of feed stream
Q= Rate that heat exchanger provides heat

Question 5

What does the expansion valve do

Answer 5

Permits pressure reduction

Question 6

In an isothermal flash process, what 2 intensive variables are specified

Answer 6

T and P

Question 7

what 2 intensive variables may be determined and how

Answer 7

x and y

From either the K factor equations of by reading T, x, y off a graph

Question 8

What 3 balance equations give you L,V and Q

Answer 8

vVF=L + V total mass balance
zF= xL +yV MVC Mass balance
hf F + Q = hl L +hv V Energy balance

Question 9

What variables do you have left to specify?

Answer 9

F, z, Tf, Pf

Question 10

Look at Slide Pack 2 Slide 7

Answer 10

‘The sum of the product of the mole fraction and the enthalpy’
hl(T)= sigma (xi hl,i(T)) enthalpy of pure liquid i
hv(T)= sigma(yi hv,i (T)) enthalpy of pure vapour i