ZZKD instrument co.,ltd is specialized in distillation and extraction equipment, rotary evaporator
, glass reactor
, short path distillation
are our main products.
The short path distillation kit process can be divided into the following four steps:
1. Molecules diffuse from the main body of the liquid phase to the evaporation surface:
2. Under normal circumstances, the diffusion speed in the liquid phase is the most important factor to control the molecular distillation speed. The thickness of the thin liquid layer should be minimized and the flow of the liquid layer should be strengthened.
The evaporation rate increases with the increase in temperature, but the separation rate sometimes decreases with the increase in temperature.Therefore, based on the thermal stability of the processed material, a more economical and reasonable distillation temperature should be selected.
3. Molecules fly from the evaporation surface to the condensation surface.
4. Molecules condense on the condensation surface:
As long as there is a sufficient temperature difference between the hot and cold sides (generally 70~100°C) and the condensation surface is smooth, the condensation step can be completed in an instant, so it is very important to choose a reasonable condenser.
Therefore, it can be concluded that the conditions for short path distillation are:
1. The pressure of the residual gas must be very low so that the mean free path length of the residual gas is a multiple of the distance between the distiller and the condenser surface.
2. Under saturation pressure, the mean free path length of vapor molecules must be the same order of magnitude as the distance between the evaporator and the condenser surface.
Under these ideal conditions, evaporation occurs from residual gas molecules without any obstacles.All vapor molecules reach the surface of the condenser, and the evaporation rate reaches the highest possible value at the temperature.The evaporation rate is proportional to the pressure, so the amount of distillate from molecular distillation is relatively small.
In short path distillation, the distance between the condenser and the heating surface is about 20-50mm, and when the pressure of the residual gas is 10-3mbar, the mean free path length of the residual gas molecules is about twice as long.The short path distiller is fully able to meet all the necessary conditions for molecular distillation.