Zhongyu Instrument Extraction Distillation Device Molecular Distillation Tower

Zhongyu Instrument Extraction Distillation Device Molecular Distillation Tower

Selection method of extraction distillation tower type for laboratory plate tower

Choosing a laboratory plate tower suitable for extraction and distillation requires comprehensive consideration of the following factors:

1. ‌Separate requirements‌

• ‌High purity requirementsIf high-purity separation is required (such as chlorobenzene purity ≥ 99.5%), sieve tray tower or float valve tray are preferred as they have higher separation efficiency

• ‌Near boiling point or thermosensitive materialsFloating valve tray has high operational flexibility and is suitable for load fluctuations or easily degradable systems

2. ‌processing capacity‌

• ‌Small scale trial (0.1-50L/batch)The sieve tray tower (such as the Oldershaw glass tower, with a diameter of 30mm) has a simple structure and is suitable for laboratory low flow operations.

• ‌Pilot scale (50-500L/batch)Need to increase the tower diameter to 50-100mm and optimize the design of the downcomer to prevent liquid flooding

3. ‌Material Selection‌

• ‌Corrosive materialsChoose glass or stainless steel materials, such as enamel lining or 316L stainless steel

• ‌Cleaning materialsOrdinary stainless steel or glass towers can meet the needs

4. ‌operating conditions‌

• ‌Pressure and temperatureUnder normal or low pressure (such as 4kPa gauge pressure), the pressure in the sieve tray tower decreases; High temperature and high pressure conditions require a floating valve tray

• ‌reflux ratioControl the reflux ratio (such as 1:99 to 99:1) through a time relay to ensure separation stability

‌Recommended tower type‌：

• ‌Routine experimentSieve tray tower (such as Oldershaw tower), with simple structure and low cost

• ‌Complex systemFloating valve tray, with strong adaptability and high efficiency

Zhongyu Instrument Extraction Distillation Device Molecular Distillation Tower

Design principle of molecular distillation tower

Molecular distillation is a special separation technique performed under high vacuum conditions (1~1 × 10 ⁻ ² Pa), and its core principle is based on the difference in the average free path of molecular motion of different substances

1. Core principles

• ‌Molecular free pathIn a vacuum environment, light component molecules can directly fly towards the condensation surface due to their large average free path; Due to the short free path, the recombination fraction was trapped on the evaporation surface

• ‌Low temperature separationThrough high vacuum and cooling plates (temperature difference>60 ℃), separation far below boiling point is achieved to avoid degradation of thermosensitive substances

2. Equipment type

• ‌Scrap film typeBy rotating the scraper, a thin liquid film is formed, which has high mass transfer efficiency and is suitable for high viscosity materials

• ‌centrifugalUsing centrifugal force to form a film, high efficiency but complex structure, high cost

• ‌Falling film typeEarly structure, thick liquid film, low efficiency, gradually phased out

3. Key design parameters

• ‌真空度Ensure that the molecular free path is much greater than the distance between the evaporation surface and the condensation surface

• ‌temperature gradientThe temperature difference between the evaporation surface and the condensation surface needs to be significant (such as above 60 ℃) to drive molecular directional motion

• ‌Liquid film controlThin the liquid film through scraper or centrifugal force to enhance mass transfer efficiency

4. Application advantages

• ‌High purity separationSuitable for high molecular weight and high boiling point substances (such as essential oils and drug purification)

• ‌Low heat damageShort heating time (in seconds) and low-temperature operation to protect thermosensitive components