4 replies to this topic

[Natural FAL]

Hi. How are you guys out there?

I come across that the vacuum pump technology can do better work than steam ejector.
Steam ejector mainly for old plant, new plant all normally come with vacuum pump.

What is the disadvantages & advantages between the both?
What is the common failure of the vacuum pump & steam ejector?

I heard from my lecturer, the vacuum pump need to take care of inlet temperature & liquid carried over to pump will trip the operation. A lots of mechanical part need to take care.
He prefer on steam ejector operation, more stable & reliable for distillation column used.

Any comment?
Thanks for clearing my doubt here.

[djack77494]

Natural,
This is much too complex a topic for a simple discussion here. Both technologies have their advantages and disadvantages. Like all situations where there is a choice of technologies, look over existing installations. Where you see that a particular technology "dominates" than either: (1) that technology is better in that application, (2) that is an older technolgy that was prefered in the past, but has now been superceded, or (3) the engineers didn't know what they were doing. As we know, (3) is virtually impossible, so you are left to decide between (1) and (2).

My experience is that steam ejectors truly do dominate when large systems must be evacuated to moderate vacuum levels (say 10 to 25 mmHg [a]). They are important (i.e. they are contenders) outside this range in moderate size systems, and sometimes even in smaller systems. Try to at least mentally identify the advantages and disadvantages of each and then assess whether your system is likely to fall one way or the other. You will have to be able to do this in order to make an informed decision. Oftentimes, you will have a situation where a particular technology would just plain be unacceptable. That helps narrow down your choices.

[Jiten_process]

Hi natural

i would say it depends on the level of vacuum, you can choose both the system and compare the utility cost and capital cost. and try to use the optimum soln.

one another point is when you use multistage rotating vacuum pump (liquid ring) you can get some flexibility in variation (or say increase) in air leakage rate because of virtue of it's almost flat operating curve. Where as steam jet ejectors are bit sensitive w.r.t. air lekage load, steam pressure fluctuation, vapor load etc.

In my plant there was 3 stage steam jet ejectors used for vacuum upto 750mmhg.

[USR]

hi...well its true that a vacuum pump require a lot of attention and maintenance than an ejector....especially because an ejector does not have any moving parts like a vacuum pump....ejectors are very popular when dealing with corrosive gases that may damage the vacuum pumps...the cons of an ejector is that it consumes large quantities of steam...the growing steam cost has made them less popular...and the fact that vacuum pumps use considerably less energy compared to an ejector....

[joshhamilton]

I think you are right USR, the vacuum pump lets n equipment, say condenser run more efficiently and has a greater payback in steam savings/energy. But why do operators perfer the eductor and the engineers prefer the pump? because of mechanical parts? the eductor wears out over time....