Wet Gas Screw compressor 6

[mucour]

Hello,

We are considering a wet gas screw compressor for vapour recovery application. The gas is wet, water saturated and a heavy gas. Could anybody advise from the experience in their plant where they have this wet screw compressor for similar service the manufacturer that they will recommend based on the equipment's performance in terms of availability and reliability.

I know many gas screw compressor manufacturers but I want one recommended from operating experience in terms of performance.

Thank you for your help.

 

[zdas04]

Everyone has to reach their own conclusions about the data they observe. I see a lot of wellsite recips with broken valves, a lot with dscharge temperatures higher than expected (generally caused by valves being too stiff and not operating fast enough to allow the cylinder to "fill" during the suction stroke), etc.

If you are having success in an application that my data says would not result in an optimum solution then you obviously have different criteria for acceptable performance than I do.

It sounds like you are doing a good thing by going to top flight valve manufactures for their recommendations. The spread in suction pressures (at sea level) from 0 psig to 15 psig is about 100% and I've never heard of a compressor manufacturer that would recommend that kind of swing for their machines. If your normal discharge pressure is 135 psig then your ratios vary from 9 to 4.5 and you ain't doing that in one stage without jacket water cooling.

Like I said, everyone has their own criteria for success and I'm happy for you that you're satisified with recips in service that I would not expect to perform well.

David

 

[pipehead]

Heres a breakdown difference, as zdas04 has seen too, CAPX vs OPX is the key. If CAPX isn't important and fuel is, then then API recips are great. If CAPX is important and fuel isn't an issue, then screws are perfect.

In midstream, CAPX is King so no one can do an API machine. BTW, IMHO why would any one do an 100% API machine?

 

[GSTeng]

zdas04,

That is a great FAQ. I knew my little dig would get more useful information out of you.

I think you might have missed one major limitation of Screw Packages. Volume!!!! You can only make a screw compressor so big and it becomes an issue. I don't really know what the issues are (you could enlighten me if you know), but I have never seen a screw bigger than about 600HP. which means if you want to move a lot of gas you need something other than a screw compressor. Now that being said recips have their limitations on size as well, but it is much higher than a screw package.

What about Turbine compressors? I know they have a place in the O&G business, it would be interesting if you added to your Recip VS Screw with Recip VS screw VS Turbine, but now I am just making work for you. Thanks for all the good info, I know if I keep prodding you, you will have no choice but to pass along more knowledge.

 

[dcasto]

Out near McClain Texas I replaced two 300HP multi-stage turbine with two sullair units driven by cat 3408's. They were so much better, with all the bells a whistles they could get the 6 mmscfd at a deeper vacuum than the others and discharge at about 40 psig.

You are correct on volume I'm trying to get a sullair 332XXL (close on model number) to see how much I can pump. I need to go from 15 psia to 50 psia, 15 MMSCFD. It looks like at least 4 units.

 

[zdas04]

The biggest screws I know of are the Howden's at the Florida River CBM plant in Durango, CO. They're electric driven monsters (Amoco bought serial numbers 1 through 4 for that project) and best I can remember they're something like 5,000 hp. I knew the specs on them in the early '90's but they aren't coming to me right now. I think they're moving over 15 MMCF/d each but that is also a dim recollection. Howden's web page (

http://www.howden.com/en/Businesses/HowdenCompressorsLtd/Products/Compressors/Screw/OilInjected.htm)

shows their capacity range is 200-24,000 m[sup]3[/sup]/hr (170-20,300 MCF/day). That is a pretty capable capacity.

The only turbine I've ever seen is in the air plant at the same facility. It is electric drive also and I've never been certain which design parameter pushed the plant designer to choose that technology. I never had responsibility for it (though I did try to buy it for a client a couple of years ago), so I can't tell you any of its strengths or weaknesses.

David

 

[dcasto]

Thanks zdas04

 

[GSTeng]

zdas04,

Williams have a number of Trubine compressors around here. But I am not really in the loop on their good and bad points. I know that they do not like any liquids or particulates what so ever, so there goes any sort of well head application or even gathering. Williams use them in some of the main transmission stations feeding their plants. I didn't know if you had any dealing with them or not.

That is truly interesting about the Howden compressors. I need to try and get in there to have a look, All I need is an excuse!!! Thanks for the info.

 

[zdas04]

GSTeng,
Send me an e-mail (my address is on my web page), if you're in the area I might be able to set something up.



David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

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