A gas stream containing 3 mol% Ammonia (NH3) in Air is to be passed to a packed absorption columnat a rate of 5 kg s1. The column is to use Water (H20) as the solvent to reduce the ammonia content in the air leaving the column to 0.01 mol%. The gas and water streams can be assumed to be at 25 °C.The column operates at 1 bar pressure.
y = Hx
What the liquid rate of solvent is under normal operating conditions.
Where the Henry's Law constant, H = 1.3 (mole frac NH3 in gas) (mole frac NH3 in liquid)1
From pilot scale experiments the Overall Mass Transfer Coefficient, KG, has been found to remain constant with a value of 200 × 10--6 kmol m² s-1
Using the protocol outlined on Page 55 of the gas absorption notes, specify an absorption column to achieve the required separation using 1 inch Raschig Rings (See Table 1 in attached data sheets).
Your Design Specification must clearly show the following:
Any assumptions made must be stated clearly.
What the minimum liquid rate for the column is.
Confirmation that the wetting rate of your column falls within the acceptable range.
Based on the assumption of operating at 60% of the flooding gas flow rate, what the diameter of the column should be in meters.
The values of HTU, NTU and thus the total height of packing required in the column.
The relationship that describes the equilibrium between Ammonia and Water at these conditions is given by:
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