Does a Liquid Ring Compressor Need an Aftercooler?

[KernOily]

Hi guys. Dumb question here from an oil patch engineer. Does a liquid ring compressor use an aftercooler, or does the liquid ring fluid (water in my case) take away the heat of compression?

My application is oilfield gas at 0 psig suction and 40 psig discharge, rate about 300 Mscfd. Owner desires to remove an existing sliding vane unit and replace it with a liquid ring machine. I have experience with liquid ring machines in vacuum service but not when used as a compressor.

I know a discharge separator is required but beyond that I'm in the dark, and I've not found much help on the web yet.

Thanks guys! Pete

 

[zdas04]

There is a reason that there isn't much information on the web--primarilly it is a dumb idea. In Kern County, the atmospheric pressure is mostly around 14 psig. That means you are going from 14 psia to 54 psia--3.8 compression ratios. The liquid ring is "good" to around 2.5. You are going to boil your seal water, and blow what doesn't boil out the back of the compressor.

I don't like liquid rings above about 5 psig discharge. They're ok below that, but not wonderful.

I'd do your project with a flooded screw.

David

 

[rmw]

David,

Other than that what didn't you like about the idea?

DernOily,

A liquid ring compressor has to have an external heat exchanger to carry away the heat of compression or otherwise the liquid seal ring fluid temperature will continue to rise. When water is that fluid, then the steam tables dictate where it will start to boil off and be carried out with the gas being compressed.

So, even if there weren't the limitations mentioned by David, you wuld have other issues to deal with. Take his advice.

rmw

 

[jamesbanda]

In my experience i've not seen a liquid ring compressor or vacuum pump with out a cooler. It depends on to what extent you purge your system out..

Heating = input from pump
cooling = top up cold fluid
heating > cooling => cooler required or the system will get hot.

i've seen a liquid ring used for a dirty fluid service as we believe the tollerances were less sensitive that a screw compressor.

Good luck hope this helps

 

[KernOily]

Guys thanks for the replies - I appreciate your time.

This application will use once-through seal water, so I will not have the issue of water heating during seal water recycle. The water will be removed from the discharge separator and sent off to another destination.

I am checking on the compression ratio issue and verfiying the required discharge pressure.

Thanks!

 

[jamesbanda]

Just a quick note.. follow the recommendations from the vendor on piping and runs etc.. i've done a project recently that the piping was screwed up and the system did not work..

we had to re-pipe later.. so follow the compressor vendors recommendations.. then you'll be fine.. and get a startup procedure from them

 

[KernOily]

"follow the recommendations from the vendor on piping and runs etc.."

Right on - will do. Thanks for the heads-up! Pete