In many cases of vacuum distillation applications, where the desired vacuum level is not achieved because of system inefficiency, it ultimately affects the product quality. Installation of booster pumps, which is comparatively a cheap proposition, often helps in improving the vacuum level under such circumstances.
Distillation at reduced pressures is a widely used process in the chemical industry, specially used in extraction or purification of essential oils, deodourisation of evanaspatifor vegetable oils and purification and drying of chemicals.
Let us take a look at the advantages of low-pressure distillation process over atmospheric pressure distillation.
- Use of lower process temperatures: Under vacuum, there is a reduction in boiling points. Hence, thermally sensitive substances can be processed easily.
- Shorter time of thermal exposure of the distillant: The reduction in thermal exposure time enables the processing of thermally sensitive items, such as vitamins and hormones, whose properties are adversely affected by extensive exposure to heat
- Increase in relative volatility: Materials become more volatile under vacuum, and therefore more evaporation takes place, resulting in higher production rates.
- Fractional distillation under vacuum leads to easier separation of components of a mixture.
- Change in position of the azeotropic point at reduced pressure: This enables separation, under reduced pressure or vacuum, of hard to separate materials.
- Reduction of energy consumption by lowering of the boiling point under vacuum.
- Oxidation losses of the feed stock are reduced under good vacuum conditions.
- Reduction in stripping steam requirements for de-odourisation process of oil due to increased specific volumes (of steam) at low pressures and enhanced agitation and stirring of the oil.
What’s happening in terms of vacuum pumps? PROCESS has tracked down the current trends and latest developments. Read more in Range of Applications for Vacuum Engineering is Growing Constantly
Ideal vacuum pump
In order to ensure satisfactory operation of the distillation process, it is essential that suitable vacuum pumps are used. Although, there is no single perfect pump, the ideal characteristics of the vacuum pump required for distillation process are described hereafter.
- Low energy input for a given volumetric pumping capacity.
- The pump should be of dry type, i.e., it should not use any pumping fluid such as water, oil, steam etc., these fluids interfere with the purity of the product and limit ultimate vacuum level.
- The ideal pump should have minimum number of stages to achieve the desired vacuum levels.
- No environmental pollution should be caused by the pumpfs operation. Hence, there should be no material pollution due to stripping or disposal of pump fluids. Noise pollution should be at the minimum level.
- The pump should have high volumetric pumping capacity at low pressures.
- The pump should have low maintenance requirements.
- The condensation of the vapours within the pump should be minimum, so as not to affect its performance.
- The pump should have high vapour handling capacity.
- It should be able to pump out little amount of liquids, in case condensation occurs inside the pump.