Asolution of sugar in water is to be concentrated from 5 wt%sugar to 20%sugar. The solution is at about 45°C when it is fed continuously to a bubble column. Air at 45°C with a dew point of 4°C is bubbled through the column and emerges saturated. The humidification of the air may be considered adiabatic.

Use the psychrometric chart to solve the following problems:

(a) What are the absolute humidities of the entering and exiting air?

(b) How many kilograms of dry air must be fed per kilogram of the entering sugar solution? What is the corresponding volume of the entering wet air? (Use the chart for the latter problem as well.)

(c) Suppose that instead of feeding the air through a sparger (a device that resembles a showerhead and releases the gas into the liquid as tiny bubbles), the air enters the column through a simple pipe. Speculate on the probable changes that would occur in the two outlet streams and briefly explain your reasoning.

Transcribed Image Text:

Air, saturated with water 5 wt% Sugar solution BUBBLE COLUMN 20 wt% Sugar solution Air T= 45°C dew point = 4°C