Wet air containing 4.0 mole% water vapor is passed through

Problem 4.20

Wet air containing 4.0 mole% water vapor is passed through a column of calcium chloride pellets. The pellets adsorb 97.0% of the water and none of the other constituents of the air. The column packing was initially dry and had a mass of 3.40 kg. Following 5.0 hours of operation. The pellets are reweighed and found to have a mass of 3.54 kg. (a) Calculate the molar flow rate (mol/h) of the feed gas and the mole fraction of water vapor in the product gas. (b) The mole fraction of water in the product gas is monitored and found to have the value calculated in part (a) for the first 10 hours of operation. but then it begins to increase. What is the most likely cause of the increase? If the process continues to run, what will the mole fraction of water in the product gas eventually be?

                                                               Step by Step Solution

Step 1 of 2

a)

Let’s draw the flow chart of the given process as follows.

 = Molar flow rate of wet gas

 = Molar flow rate of product gas

 = Mole of water adsorbed per hour.

 = Mole fraction of water vapor in product.

From the given,

Mass of column packing before adsorption = 3.40 kg

Time of adsorption = 5.0 hrs

Mass of column packing after adsorption = 3.54 kg

Let’s calculate the moles of water adsorbed per hour as follows.

The molar flow rate of water adsorbed is 97.0% of the water in the wet air.

Let’s calculate the molar flow rate of wet air;

The overall mole balance equation for the given process is as follows.

Substitute the known values in the above equation.

Write mole balance equation with respect to water.

Therefore, the molar flow rate of the feed gas and the mole fraction of water of water vapor in the product gas is  .

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