Production of <i>p</i>-Xylene from Xylene Mixture by Recycle Process (Part V)

Abstract

The overall coefficients of heat transfer through mixed xylene was measured with heat exchangers of double tubular and tank type at homogeneous or heterogeneous state at the temperatures of +5--70°C. Ethyl alcohol-dry ice or Fleon was used as refrigerant, and the temperatures as low as -70°C were applied. The overall coefficient of heat transfer was somewhat larger than 200kcal/m2•hr•°C near the room temperature, and it decreased gradually with the temperature drop, approaching 80-100kcal/m2•hr•°C at -70°C. The rate of flow and the speed of agitation had some effects on the overall coefficient of heat transfer, while the properties of refrigerant and the state of crystallization of p-xylene had practically no effects.The state of flow was observed with the slurry of mixed xylene containing 20 or 40% of p-xylene crystal. It was confirmed that the slurry behaved as a Bingham fluid in a stream line flow, and the pressure drop in a range of turbulent flow would be about 1.5 times larger than that of homogeneous system at the same rate of flow.