Vacuum ejector

PC = paraffin column DC = detergent alkylate column VE = vacuum ejector. 

Croll-Reynolds Co., Design and Application of Steam Jet Vacuum Ejectors, Croll-Reynolds Co., Westfield, N.J. 

FIG. 14 Flow diagram of the HF alkylation process. R, reactor AS, acid settler HR, HF regenerator HS, SF stripper BC, benzene column PC, paraffin column RR, rerun column AT, aluminia treater VE, vacuum ejector. 

There is little danger, in injecting a controlled amount of water into a furnace inlet, when using a properly designed metering pump. Such pumps typically have a capacity of 1 to 10 GPM and provide a set flow, regardless of the discharge pressure. The injected water flashes immediately to steam inside the furnace tubes. Vfe have retrofitted several vacuum and delayed coker heaters with condensate injection systems, with no adverse downstream effects. Water from the hot well of a vacuum ejector system is our normal source of condensate for this environmentally friendly modification. 

Figure 3.13. Crude oil vacuum tower. Pumparound reflux is provided at three lower positions as well as at the top, with the object of optimizing the diameter of the tower. Cooling of the side streams is part of the heat recovery system of the entire crude oil distillation plant. The cooling water and the steam for stripping and to the vacuum ejector are on hand control.

For sizing the vacuum ejector, air leakage is estimated at 25 Ib/hr and carbon dioxide is 34 Ib/hr. 

Steam for power via turbines drives Section 3.1 and via vacuum ejectors. Section 2.2. Thermal heating. Section 3.3, separations via evaporators. Section 4.1, distillation, Section 4.2, dryers. Section 5.6, and blowouts of lines. Section 2.7. 

The eductor or eductor-jet pump is also called an injector, a vacuum ejector, a water eductor, a steam-jet ejector, or an aspirator. Every chemistry laboratory has rrtany. 

Vacuum ejectors require a constant flow of steam regardless of gas rate. 

Vacuum distillate, 19, 22 Vacuum ejectors (energy savings), 220-222... 

FIGURE 13-4 Raising ilash-zone temperature can overload vacuum ejector. 

Motive-steam pressure that is too high will also hurt the vacuum. This is because the steam nozzle will pass more steam than the diffuser throat was designed to handle. The diffuser chokes on the extra steam and the vacuum is adversely affected. Or, the downstream condenser may be overloaded by the increased steam flow and cause back pressure against the vacuum ejector discharge. 

Martin, G.R. (1997) Understand real-world problems of vacuum ejector performance. Hydrocarbon Processing, 76 (11), 63-75. Power, R.B. (1993) Steam Jet Ejectors for the Process Industries, McGraw-Hill. Produktkatalog (2009), GEA Wiegand GmbH, Ettlingen. 

This is an example of Bernoulli s equation in action. A steam vacuum ejector (jet) works in the same way. Centrifugal pumps and centrifugal compressors also work by converting velocity to pressure. Steam turbines convert the steam s pressure and enthalpy to velocity, and then the high velocity steam is converted into work, or electricity. The pressure drop we measure across a flow orifice plate is caused by the increase of the kinetic energy of the flowing fluid as it rushes (or accelerates) through the hole in the orifice plate. 

I did not understand thermodynamics at university. It seemed to be an exotic subject with no relevance to my future as a refinery process engineer. It wasn t until I had spent many years working with steam turbines, surface condensers, steam distribution systems, and most especially vacuum ejectors that I realized that without a firm understanding of thermodynamics, I could not operate or troubleshoot such facilities with any degree of confidence. 

Expanding high-pressure steam to a low pressure through a steam nozzle used in turbines and vacuum ejectors (see Fig. 20.3) is my favorite example of an isoentropic process. 

Well, something has changed. I ve changed. Since Liz and I authored the third edition, we have both become smarter. Smarter in the sense that we have learned a lot about our misconceptions about how process equipment works. Much of our imderstanding about vacuum ejectors, centrifugal compressors, pump mechanical seals, and distillation tray hydraulics were not correct. We re both learning all the time. So we must be getting smarter. 

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