Heat And Mass Transfer In Short-Path Distillation Process And Application Of The Process To Regeneration Of Waste Lubricating Oil

Short-path distillation is a new-type separation technology under high vacuum condition. It has the characteristics of low temperature, short exposure time and high evaporation efficiency. It is therefore especially suitable for the separation of materials with high boiling point, high heat-sensitivity and easy oxidization. In addition, it has broad application prospect in the fine chemistry processes such as food production, medicament purification, grease refinery and flavor manufacture. The wiped film short-path distiller is a kind of short-path distillation equipment with high evaporation rate. Due to the agitation of the wipers, the renewal of the liquid film surface is quickened and the performance of heat transfer and evaporation are strengthened. At the same time, however, the liquid flow in the distiller as well as transfer process mechanism in the liquid film becomes very complicated.Firstly, the principle of the short-path distillation is reviewed, which indicates the radical difference between the short-path distillation and molecular distillation. Apart from this, the technical characteristic of short-path distillation, the development of the types and structure of equipment, the industrial application as well as the current research on heat and mass transfer are presented.Secondly, base on the analysis of the evaporator in the wiped film short-path distillatory, it can be concluded that the effect of the remained inert gas inside the equipment on the evaporation process is extremely minor and the distillation resistance of volatile components mainly comes from the their diffusion in the liquid film. The heat and mass transfer models inside the liquid film are founded under the above basis to obtain the difference equations of heat and mass transfer. Difference Method is used to discretize the difference equations and their boundary conditions. Furthermore, the numerical value solution is programmed. Then, the simulation calculation was made on the basis of the mixtures of DBP (di-butyl-phthalate) and the DBS (di-butyl-sebacate) to obtain the liquid film temperature distribution, concentration distribution, as well as the evaporation rate. And the effects of the initial temperature, feed rate and initial concentration are discussed.Finally, two short-path distillation processes and one falling film evaporator are applied in the regeneration of waste lubricating oil. In the test, the diesel oil, gasoline and lubricating oil are distilled respectively, while the gelatinoid materials, asphaltene and carbon residue remain in the draft. The regenerative lubricating oil accords with the standards of base oil. And the recovery efficiency is up to 75 percent. The technology used in the test doesn't comprise processes like pickling and alkali neutralization, which would cause secondary pollution like acid draff and sulfur dioxide and so on. As a result of this, our technology is friendly to the environment. In spite of some deviation between the experiment value and simulation value, the variation trend is approximately consistent, which shows a certain reliability of our heat and mass transfer model concerning the short-path distillation process.