Monday, July 4, 2011

Vacuum booster for distillation process

Distillation at reduced pressures is a widely used process in the chemical industry, specially used in extraction / purification of essential oils, deodorisation of Vanaspati / Vegetable Oils and purification & drying of chemicals. The advantages of low-pressure distillation process over Atmospheric pressure distillation are as under:

  • 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 vitamin & harmones, 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 / 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 & stirring of the oil.


Ideal Vacuum Pump :
In order to ensure satisfactory operation of the distillation process it is essential that suitable vacuum pumps are used. While there is no single perfect pump, the ideal characteristic of the vacuum pump required for distillation process are:

  • Low energy input for a given volumetric pumping capacity
  • The pump should be 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 pump operation. Hence there should be no material pollution due to stripping or disposal of pump fluids. Noise pollution should be at the minimum.
  • The pump should have high volumetric pumping capacity at low pressures
  • The pump should have low maintenance requirements
  • The condensation of the vapors within the pump should be minimum so as not to effect its
    performance
  • The pump should have high vapor handling capacity
  • Should be able to pump out little amount of liquids, in case condensation occurs inside the pump
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Vacuum Booster is a Dry pump that meets most of the ideal pump requirements. It works on positive displacement principle. As its name suggests, it is used to boost the performance of water ring / oil ring/ rotating vane / piston and in some cases even steam ejector pumps. It is used in conjunction with any one of the above mentioned pumps , to overcome their limitations. Vacuum Booster pump offer very desirable characteristics, making them the most cost effective & power efficient alternative. The major advantages are :

  • The vacuum booster is Dry Pump. It does not use any pumping fluid. Hence it pumps vapor or gases with equal ease. Small amounts of condensed fluid can also be pumped.
  • It has very low pump friction losses, hence requires relatively low power for high volumetric speeds. Typically, their speeds, at low vacuums are 20-30 times higher than corresponding vane pumps / ring pumps of equivalent power.
  • The vacuum Booster can be used to generate vacuum in range of 0.001 Torr and yet have high volumetric speeds at such low pressures. At these pressures the rotary oil and water ring pumps are not effective, as their pumping speed falls drastically when approaching the ultimate levels.
  • The vacuum Booster can be used over a wide pressure range, from atmospheric pressure down to 0.001 Torr (mm of mercury), with suitable arrangement of backup pumps.
cuum Booster

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