Additional jet vacuum cooling saves Pfizer $100,000. Combination system gives flexibility, avoids downtime, cooling-coil cost.
Problem: Process changes boosted cooling requirements at the Groton, Connecticut, plant of Pfizer, Inc. Various organic acids, antibiotics, synthetic medicinals and vitamins are produced in non-stop operation. Cooling water is needed continuously for processing equipment, condensers, water jackets and coils.
To add more cooling-coil area to existing vessels would require plant shutdown, with loss of production time, and considerable expense.
A 4-stage steam jet vacuum cooling unit which can produce 3200 gpm of 45Â°F water was added to the existing system. An original 900-ton unit had been augmented by installation of two 1,500-ton coolers which are operated in parallel, and later supplemented by a third 1500-ton unit. Some output from 3 parallel-connected, 1500-ton machines is used as feed for new equipment.
In jet vacuum cooling, water enters a chill tank. Steam at high velocity entrains water vapor from chill tank, producing a high vacuum which causes the water to boil. Combined stream of motivating steam and water vapor is condensed by cold river water in barometric condenser.
Energy released as water vapor expands causes turbulence that breaks up water so that there is a very close approach to equilibrium between temperature and pressure. Heat required for boiling comes from water itself, along with a small amount from container.
Sensible heat of water is used to supply latent heat of vaporization. This loss of heat causes temperature of water to drop. Repetition of process through 4 stages provides required temperature reduction. Chilled water is removed by pump.
Combined system operates on process controller feedback demand. Except for pump controls, which are electronic, all controls are by direct pneumatic signal.
Results: Availability of lower temperature water, made possible by 4-stage cooler, canceled need for additional cooling-coil area. This eliminated production downtime and installation costs. The integrated system provides flexibility in cooling-water temperature.