Direct Contact Heat Transfer in Melt Crystallization.

Abstract

The heat transfer of melt crystallization with direct contact coolants such as gas, liquid and vaporized liquid was explored. Melt crystallization with direct contact coolants was carried out by crystallizing n-dodecanol from n-decanol - n-dodecanol mixture. The direct cooled crystallizers were capable of being operated either batch-wise or continuously. The superficial velocity of coolant: 3 × 10–6–2 × 10–4 m/s for the vaporized liquid, 1 × 10–5–1 × 10–4 m/s for the liquid and 5 × 10–2–2 × 10–1 m/s for the gas, and the hold-up of coolant: 0.02–0.9 for the liquid and 0.01–0.25 for the gas were varied. The volumetric heat transfer coefficient obtained by direct contact cooling in the melt crystallizer was varied in the range of 0.1 to 100 kW/m3K. It was roughly proportional to the 1.5 to 1.8 power of the linear velocity of coolant. The semiempirical relations for correlating the volumetric heat transfer coefficient in the direct cooled melt crystallization were presented.