Choose the Right Vacuum Pump
The need to operate under vacuum is widespread throughout the chemical process industries (CPI). Distillation, drying, flash cooling, stripping, and evaporation are among the unit operations that frequently take place at less than atmospheric pressure.
In many process applications, the overriding consideration is the amount of vacuum (or degree of evacuation) required. Of the five major types of vacuum producing devices discussed here, the ejector can achieve the greatest degree of evacuation: down to 5 micrometers of Hg absolute. Dry pumps and rotary piston pumps can each evacuate to 10 micrometers Hg; once-through oil pumps can reach 500 micrometers Hg; and liquid ring pumps can go down to 10 mm Hg.
Aside from its vacuum producing ability, each of the five types has its own set of attractions and drawbacks. Many of these depend on the
particular application.
Ejectors are workhorses
The simplest and probably most widely used vacuum producer is the ejector (Figure 1)....