[Production Version] Daily Question 2018-07-03 (Short Answer)

As the liquid mixture flows over the heating plate and is heated, light and heavy molecules escape from the liquid surface into the gas phase. Due to the different mean free paths of these light and heavy molecules, they travel different distances after escaping from the liquid surface. If a condensation plate is placed appropriately, the light molecules reach the condensation plate and are condensed and removed, while the heavy molecules do not reach the condensation plate and are carried away along with the mixture. The pressure difference between the boiling film and the condensation surface is the driving force for the flow of steam; even a slight pressure drop can cause steam to flow. Operating at 1 mbar requires a very short distance between the boiling surface and the condensing surface; distillers built on this principle are called short-path distillers.

It is a new type of high-efficiency evaporator that uses a special mechanical device inside the tube to force the raw material to form a film evenly on the heating surface, enabling falling-film evaporation under high vacuum.

Short-path distillation utilizes the size of the molecular free path to achieve separation; a condensation surface is placed at a certain distance from the evaporation surface, allowing the substances that reach this surface to be separated. Film evaporation simply causes the evaporation process to form a film on the evaporation surface, thereby accelerating the rate of evaporation. Of course, short-path distillation also takes place by forming a film on the evaporation surface.

A distiller constructed based on the principles of molecular distillation

Short-path distillation utilizes the size of the molecular free path to achieve separation; a condensation surface is placed at a certain distance from the evaporation surface, allowing the substances that reach this surface to be separated. Film evaporation simply causes the evaporation process to form a film on the evaporation surface, thereby accelerating the rate of evaporation. Of course, short-path distillation also takes place by forming a film on the evaporation surface.

It is a new type of high-efficiency evaporator that uses a special mechanical device inside the tube to force the raw material to form a film evenly on the heating surface, enabling falling-film evaporation under high vacuum.

A short-path distiller is a thermal separation technique that operates at pressures ranging from 1 to 0.001 mbar; its low boiling temperature makes it highly suitable for heat-sensitive substances with high boiling points.

Distillation is a unit operation in chemical engineering used to separate mixed liquids; it is divided into atmospheric distillation and vacuum distillation. It relies on the different volatilities of the various components in the mixture to achieve separation. In other words, when the saturated vapor pressure of the light component to be separated is higher than the pressure in the system, separation becomes possible. Therefore, the lower the pressure in the system (the higher the vacuum level), the easier the separation. Molecular distillation builds upon conventional distillation by introducing the concepts of saturated vapor pressure and average molecular free path; it allows the light component molecules that have separated from the liquid phase to be captured and accumulated as quickly as possible. This is achieved by ensuring that the distance between the heating surface and the condensing surface is equal to or less than the escape free path of the light component molecules, but greater than the average molecular free path of the heavier components. To obtain good separation results, the condensing area must be larger than the evaporation area. However, due to constraints imposed by the design of the equipment, actual devices cannot meet the ideal conditions for molecular distillation; they can only approximate or simulate it, which is why such devices are referred to as short-path distillers.

It is a new type of high-efficiency evaporator that uses a special mechanical device inside the tube to force the raw material to form a film evenly on the heating surface, enabling falling-film evaporation under high vacuum.

A short-path distiller is designed based on the principles of molecular distillation; it is a model that simulates molecular distillation. Since the distance between its heating surface and cooling surface is very small, the resistance is low, which is why it is called a short-path distiller.