Condensation Process In Short-Path Distiller And Test Of Erucic-Acid Recovery From Distillation Residues

As a new technology for liquid-liquid separating, short-path distillation has a very good commercial application prospect. Based on short-path distillation technology development and application, this paper introduced its theoretical basis, development and present applying situation, then, discussed the influence factors in the distillation process, the distiller structure, accessories and assistant equipment.On that basis, the tests for recovery erucic-acid from the distillation residues were conducted by using short-path distillation device and vacuum distillation device respectively. The comparison between the tests results showed that the short-path distillation has the advantages of low operating temperature and short heating time, which help promoting the product quality effectively. The erucic-acid purity in short-path distillation product reaches to about 85%, ten percent higher than that in vacuum distillation product. The percentage of decomposed material in short-path distillation products can be retained within 0.1%, while in vacuum distillation products, it is above 0.6%. With the same feed rate, short-path distillation could obtain more erucic-acid and fewer residues. The tests prove that short-path distillation technology is not only feasible for recovery the erucic-acid from the distillation residues, but very suitable for separation of those substances, like erucic-acid with attributes of high boiling point, high heat-sensitivity and easily oxidized. Therefore, as an innovation to conventional distillation technology, short-path distillation will find broad applications in production processes of the long carbon chain unsaturated fatty acid and its ramification. According to the characteristic of steam condensation process in the short-path distiller, reasonable assumptions and simplifications were made and the momentum equation and energy equation for condensate film were established. Solving the equation, we obtained the velocity and temperature distributions in the film and the expression of film thickness and average heat transfer coefficient. By making heat balance for the condensation system, the heat transfer design formulas for specified distilling load were developed. By taking into account the liquid sensible and stream latent heat released in condensation process, the heat transfer design formulas were amended. The corrected formulas were adopted for process calculation and the results agreed very well with the engineering experience values. These results possess great theoretical guidance significance for further film transfer process research and industrial design calculation.Finally, aimed at the heat transfer enhancement in condensation film, the paper analyzed and reviewed some related results in literatures, summarized several heat transfer enhanced measures for condensation, these measures include making use of surface tension, accelerating liquid removing, transforming filmwise condensation into dropwise condensation, coating porous medium on tube surface and weakening the impact of non-condensable gases. These results are valuable for further study of condenser structure and the design of energy-saving condenser.