|(Jan-March 2002 (Page 62)
Published in "Indian Chemical Engineer" Vol 44
New Delhi-based Everest Transmission claims to have successfully developed Mechanical Vacuum Booster to replace steam ejector. Steam ejectors are used in Vacuum pumping applications such as in vapour extraction, chemical processing, evaporative cooling, Vacuum distillation, vegetable oil deodorization, Vacuum refrigeration, drying, etc. In spite of fact that steam ejectors have relatively high energy consumption and poor overall efficiency, they are popular in Vacuum applications because of their simple operational procedures. Considering their disadvantages, Mechanical Vacuum Booster comes as an efficient alternative. The major advantages of Mechanical Boosters are:
i. Mechanical Vacuum Boosters are more energy efficient.
ii. They require minimum auxiliary equipment. On the contrary, steam ejectors need large condensers, cooling towers, re-circulation pumps, etc.
iii. Mechanical Vacuum Boosters are dry pumping system. Therefore do not pollute water and atmosphere.
iv. Startup time for them is very low, which is ideal for batch process operation where immediate startup and shut down are essential for energy conservation.
Being dry pump, Mechanical Vacuum Boosters meet many of the ideal pump requirements. Firstly, it does not use any pumping fluid. Hence, it pumps vapour or gases with equal ease. Small amounts of condensed fluid can also be pumped. Secondly, it has very low pump friction losses. Therefore, it needs relatively low power for high volumetric speeds.
The Vacuum booster can be used to generate Vacuum upto the range of 10 Torr and still maintain high volumetric speed at such low pressure.
Use of electronic control devices such has variable frequency drive (VFD) allows modifying Vacuum boosters operating characteristics to conform to the operational requirements of the backing pumps. Hence, they can be easily integrated into all existing pumping setups to boost their performance.
The operating costs for mechanical Vacuum systems are low. Hence, it has very short pay back period. For example, when operating in the range of 5-10 Torr, the operating cost of mechanical pumping system would be about one tenth of the equivalent steam ejector system.