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Homework Statement
A Mixture of air and acetone is being vented from a solvent recovery plant. The air has to be scrubbed and this is done by absorbing the acetone into water in an absorption column. The acetone is present in small amounts and its concentration never rises above 4 mol % of the total gas mixture.
Environmental regulations require that the exit acetone from the scrubbing ( absorption column) to ba at, or below, a concentration of 0.6 mol% of the exit gas.
The number of actual plates in a column required to carry out this operation must be calculated. Sieve trays will be used with a known efficiency for an absorption operation of this type of 30%.
Because of restrictions on the plant operation the minimum water flow rate available is 0.38 kmol/s
Find
a) What is the amount of gas that can be handled by this solvent flowrate?
b) The number of equilibrium stages needed if a liquid flow rate of 1.3 times the minimum is used with the same gas flow rate.
c) The number of actual plates needed if a plate column is used.
Homework Equations
The equilibrium relationship for the acetone/water system is given by a HENRY's law in the form of
y= Hx
where H is a law constant, Y is an equilibrium mole fraction of acetone in an air/acetone mixture with x, a mole fraction of acetone in an acetone/water mixture.
In this case H has a value of 0.09
The Attempt at a Solution
Ok I start with a graph with Y and X axis
The equilibrium line = 0.04 ( from Y axis), and a slope of L/G minimum = 0.04/0.09= 0.44 ( x axis)
draw a second line from y-axis at 0.06 and meets with 0.44
I know minimum water flow rate = 0.38 k/mol
Im not sure where to go from here - please any help