Consists of combination ejector and liquid-ring pump:
Problem: Abbott Laboratories needed a vacuum system for a batch distillation process used in the manufacture of an anti-convulsant known as Depakene. Production is about 6000 lb/ yr. System was to handle 10 lb/hr of air at a suction pressure of 2 Torr.
Abbott wanted a vacuum system that was reliable and also one that used a minimum amount of energy. Another requirement was a low level installation. Since Abbott had been purchasing ejectors from one vendor and liquid-ring vacuum pumps from another, company also desired to purchase both from one vendor, if possible, so as to achieve single-source responsibility.
Solution: After considering various alternative, plant installed a 4-stage combination system consisting of a liquid-ring vacuum pump and a 2-stage steam-jet ejector unit. Materials of construction were all 316 stainless steel. The liquid-ring vacuum pump provides the Initial and major reduction in pressure down to 28″ Hg vacuum. The two ejector stages further decrease this pressure to 2 Torr.
Results: This combination system has been shown to have a utility cost only two-thirds as great as one in which a conventional 4-stage ejector system is used. Hence, utility cost is reduced by 33%. No significant maintenance has been needed on vacuum system since it was installed in June 1978.
By: Javed Aslam – Corporate Engineering, Abbott laboratories, North Chicago, Illinois and Gordon H. Weyermuuer, Editorial Director