Question

NaCl is crystallizing from an aqueous (water) liquid solution onto a crystal particle of pure NaCl at 18 C. Assume particle growth is controlled by mass transfer, and the particle is spherical. The aqueous solution is supersaturated at a mass fraction NaCl=0.30. If the initial particle diameter is D=0.1 mm, find D after 3600s.​

Answer 1

Explanation:

NaCl is crystallizing from an aqueous (water) liquid solution onto a crystal particle of pure NaCl at 18 C. Assume particle growth is controlled by mass transfer, and the particle is spherical. The aqueous solution is supersaturated at a mass fraction NaCl=0.30. If the initial particle diameter is D=0.1 mm, find D after 3600s.

Data:

Solubility of NaCl in water at 18 C = 0.2647 mass fraction

Density of pure solid NaCl = 2.163 g/cm3

Molecular weight NaCl = 58.45

Density of aqueous solution of NaCl = 1.20 g/cm3 (assume constant).

Density of pure water = 1.0 g/cm3

Molecular weight pure water = 18

DNaCl-water at 18 C = 1.24 x 10-9 m2/s.

Mass transfer coefficient k = 2.0 x 10-6 m/s