Water distillation equipment and molecular distillation equipment are two different principles and applications of separation technology, the main difference is reflected in the working principle, applicable scenes, equipment structure and operating conditions. The following is a comparative analysis of the two:
Working principle
Water distillation (Steam Distillation)
- Principle: By passing water vapor into the mixture to be separated, the partial pressure of the high-boiling-point components is reduced, so that they are volatilized at temperatures lower than the normal boiling point, and then condensed and separated.
- Applicable objects: mainly used to extract substances with better thermal stability, higher boiling point and insoluble in water (such as essential oils of plants, certain organic compounds).
- Key conditions: atmospheric pressure or low pressure, relying on water vapor as a carrier.
Molecular Distillation
- Principle: Separation is achieved under a high vacuum (usually below 0.001 mbar) by utilizing the difference in the mean free range of the molecules. The molecules evaporating from the surface of the liquid do not need to go through the boiling process, but escape directly to the condensation surface and condense.
- Applicable objects: Suitable for high boiling point, heat-sensitive substances (e.g. natural products, vitamins, fish oil, polymer materials).
- Key conditions: very low pressure (high vacuum), short evaporation-condensation distance (short distillation), low temperature operation.
Equipment structure and operating conditions
| Comparison item | Water distillation equipment | Molecular distillation equipment |
| Pressure conditions | Atmospheric or low pressure (no high vacuum required) | High vacuum (<0.001 mbar) |
| Temperature range | Higher (near or slightly below atmospheric boiling point) | Low temperature (significantly below atmospheric boiling point) |
| Evaporation method | Water vapor assisted evaporation | Surface free evaporation (no boiling) |
| Condensation | Conventional condenser (water-cooled or air-cooled) | Short-range condensation (condensing surface close to evaporating surface) |
| Equipment complexity | Simple (heating device + condenser) | Complex (high vacuum system, precise temperature control) |
| Power consumption | Lower energy consumption | Higher (high vacuum and low temperature) |
Application Scenarios
Water distillation
- Extraction of natural products (e.g. essential oils, spices, active ingredients of traditional Chinese medicine).
- Separation of high boiling point organic substances that are not miscible with water.
- Laboratory or small-scale production.
Molecular distillation
- Purification of high value-added thermosensitive substances (e.g. fish oil DHA/EPA, vitamin E, natural pigments).
- Polymer material removal of monomers or solvents (e.g. silicone oils, resins).
- Separation of high boiling point/high viscosity substances (e.g. petroleum residue, lubricants).
- Industrialized continuous production.
Comparison of Advantages and Disadvantages
| Equipment type | Advantages | Disadvantages |
| Water distillation | Simple and low cost equipment; easy to operate | Low efficiency; not suitable for heat-sensitive substances; may leave water residue. |
| Molecular distillation | Low temperature, high efficiency, no thermal decomposition; high purity; continuous operation. | Expensive equipment; complicated maintenance; high dependence on vacuum system. |