Solvent Recovery Process Design: Choosing the Ideal Coolant
Which coolant (water or refrigerant) will enable the highest percentage recovery of the solvent?
Given the economic value of the solvent, a process is being designed for its recovery. Two fluids are available for use as coolant in the condenser: water at 25 ˚C and refrigerant at −30 ˚C. The condenser outlet temperature can be assumed to be equal to the coolant temperature. Which coolant (water or refrigerant) would facilitate the highest percentage recovery of the solvent in this scenario?
Final Answer:
The refrigerant would enable the highest percentage recovery of the solvent in this scenario due to its lower temperature relative to the water. Cooling the gas below the solvent's boiling point makes condensation, and therefore recovery, of the solvent more effective.
Explanation: In this scenario, it's important to note that the lower the temperature of the coolant, the higher the percentage recovery of the solvent. This is due to the principle of condensation of gaseous solvent into liquid when the gas is cooled, especially when its temperature is lowered to a point below the boiling point of the solvent. Since the refrigerant's temperature of -30˚C is lower than the water's temperature of 25˚C, the refrigerant would facilitate a higher percentage recovery of the solvent (in this case, a solvent with vapor pressure similar to benzene). This would be possible only as long as the refrigerant's temperature is still below the boiling point of the solvent.
Using the refrigerant as the coolant in the condenser would therefore make the process more effective and ultimately economically beneficial due to the higher recovery of the valuable solvent.