How to pump liquid from vacuum to atmosphere

[ekajsemaneht]

Greetings,

The application is a wiped film evaporator (~1.2-1.5 kg/hr throughput). The concentrate and the distillate gravity feed round bottom flasks. I'm not worried about the cold-trap waste. The evaporator volume is under vacuum (~0.003Torr).

I want to pump the liquid from the discharges to a larger vessels for continuous operation. My experience is only with pumping fluids from atmosphere, or positive head, to a higher pressure. In the configuration that I want, there is a risk of atmosphere leaking into the vacuum. I'm just wondering what the state of the art is... I know there are methods. In fact, I've seen a jacketed, spur gear pump doing it. However, rather than buying something I'd rather piece components together myself.

Finally, on the gear pump I've seen - the discharge had a gooseneck shaped pipe. I wonder if this isn't acting as a type of manometer preventing atmosphere from bubbling in.

Any tips on pump types that are used in this application would be great. Also, any thoughts on the gooseneck outet pipe.

Thanks.

 

[Rx7man]

I think you might be right about the function of the gooseneck.
When operating at very low pressures, cavitation (essentially boiling of the liquid) is going to be your biggest enemy, so low speed, positive displacement pumps are probably the only ones that will be reliable.. and of course you'll want a good check valve in the system as well.

Hopefully someone else has some more specific experience