Liquid ring compressor?

Vacuum pumps are a particular form of compressor, with an extremely high compression ratio. They take gas at VERY low pressure and raise it to atmospheric pressure.

I saw something about it a couple years ago, and have forgotten most of the details. But, the basic scheme is just like a Gast carbon-vane pump except that the seal is maintained by a liquid that is slung outward by centrifugal force, allowing the pump to handle dirt to some degree. How they clean the fluid to prevent it from totally jamming up is not clear.

But, Google shows :

We used liquid ring pumps to withdraw and compress digester gas (wet dirty methane). The pumps will draw a vacuum on the intake side and discharge to a pressure higher than atmosphere on the outlet. They work with dirty corrosive gases and don't complain.

Here's a pretty good description...

They are used (amongst other things) as condenser air extraction pumps in power stations.

They don't wear out. The working fluid can be water and is replenished automatically as a side effect of pumping half psi steam in with the air.

The condenser air extraction pipes are in the centre of the condenser tube-nests, where the incondensibles migrate to. The pumps pick up a mixture of air and steam. The excess water from the pumps is simply returned to feedwater and the damp air is vented.

Steam air ejectors are used initially to pull the vacuum before starting the turbine, but the rotary pumps are used to maintain the vacuum.

Mark Rand RTFM

why would you want one

I rebuild about 2 or 3 a year which have run 24/7 for 6-10 years pulling vacuum on gas wells.

I had one. I sold it on eBay a while back though. Here's a picture:

Best wishes,

Chris