Compressor selection
Compressor selection
(OP)
Hi all, We have an application to boost/compress commercial nitrogen from ~580 psi inlet pressure to ~590 psi(10psi boost)in a closed circuit for heat transfer application. Operating Temp is ~150-210 deg F. The inlet volume is 800 ICFM at 580psi Can any one suggest what are the options and who makes and which will be most durable and maintenance free units?
Also can I have an approx idea of theoretical BHP need in this application? (I had way off conflicting figures given by some vendors) Thanks in advance ....Raj
Also can I have an approx idea of theoretical BHP need in this application? (I had way off conflicting figures given by some vendors) Thanks in advance ....Raj





RE: Compressor selection
OK, assuming it is inlet conditions then that converts to 37.4 MMSCF/day. Your lift is only 1.017 compression ratios, but the job is still 1500 hp.
I think I would look at an axial compressor to do this since you can't get a blower with that kind of pressure rating.
David
RE: Compressor selection
a compressor for an application so described is rare, rare indeed.
btw, icfm is inlet cubic feet per minute at the compressor inlet.
an axial flow compressor may not be applicable at these pressures.
good luck!
-pmover
RE: Compressor selection
What the heck are you talking about? He provided inlet pressure and temperature (range), outlet pressure, gas being compressed, and a way to calculate mass flow rate. I don't know what might have been missing. I'm usually the first to complain when someone asks a question without providing enough information and I think RMSINT did a reasonable job of stating his problem.
Also, I've seen axial machines with ANSI 600 discharge flanges so I don't think 580 psig is a stretch. At the low ratios and big volume I would look at a dynamic machine instead of a PD machine. If you could find a dynamic blower that would work at 580 psig that would be ideal, but I'm not familiar with any of those.
David
RE: Compressor selection
Could you give some precisions about the application in itself? (type of HX, purpose of application, description of the loop etc)
Thks
Rgds
Wimple
RE: Compressor selection
Thanks David for the valuable answers.
ICFM stands for Inlet Cubic Feet/ Minute
Regards
Raj
RE: Compressor selection
My understanding has always been that compressor manufacturers use ICFM as conditions upstream of equipment in front of the compressor inlet. So, in an air compressor ICFM is at the air inlet of the unit, or skid boundary, and ACFM is at the compressor flange after inlet piping, inlet filter, inlet valve, etc.... The difference in value is due to pressure drop and temperature rise across that equipment.
RE: Compressor selection
My confusion was that in the case of air compresors, ICFM is reasonably close to SCFM and most of the time you can safely ignore the difference. I've never seen that term applied to a 570 psig compressor inlet and wanted to clarify. For communication, mostly I see SCF or nm3 for elevated pressures. If a particular calc requires ACF (like compressor hp) then the coversion is done at that time from SCF. It doesn't matter generally as long as there is clarity.
David
RE: Compressor selection
I agree ICFM is not appropriate in this case and understand the confusion. I wrote that, but must have deleted it when editing my response before posting. I don't agree that ICFM is close to SCFM in air compressors (except if you're at STP) - did you mean ICFM is reasonably close to ACFM? I agree you can often ignore the difference there.
RE: Compressor selection
David
RE: Compressor selection
I guess there is no distinction in this case. In the case of the air compressor the distinction is two different inlet points with different conditions - skid boundary (upstream of filter, inlet valve,...) and compressor flange (downstream of that equipment). P&T will be different, although it may be negligible in terms of cfm. This is the way air compressor mfrs often distinguish between ICFM and ACFM.
RE: Compressor selection
RE: Compressor selection
David's estimation (pl see the reply on 8/3/09) is ~ 1500 HP.
You have indicated 50HP. How can be so different?
By the way can you please recommend some blower companies who make it for such high pressure inlet conditions?
Raj
RE: Compressor selection
Rgds
Wimple
RE: Compressor selection
David,
my purpose for for stating "alternatives to the process such that the end result can be achieved" expand beyond just the compressor boundaries and conditions stated by OP. there are many applications & situations in which rotating machinery selection and the process conditions are modified/changed (slightly in this case ?) to be the best fit and perhaps avoid additional equipment/machinery. since reading the posting again, the OP notes a closed loop and a heat transfer application. whether or not the overall process can be changed, we do not know; hence, my question.
for the compression ratio and HP initially stated, it is rare for an IFC (likely a 1 or 2 stage AFC) at the stated conditions. yes, a dynamic machine is likely more appropriate.
hope this clarifies my initial posting . . .
good luck!
-pmover
RE: Compressor selection
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RE: Compressor selection
I am not still clear abut the HP need being so different in two responses David and dcasto.
Is there review from David on this?
RE: Compressor selection
Dcasto is correct as well.
thats it
rgds
wimple
RE: Compressor selection
I went to the Spencer Web site and on the custom applications I found:
I think they stop well below the 580 psig this application requires.
I'm really curious about what parameter we are looking at differently. 800 ACFM at 570 psig and 200F is 37 MMSCF/day. Even at 1.017 ratios, the masses involved in moving that many molecules takes more than 50 hp. What are you seeing that I'm not.
David
RE: Compressor selection
I wonder if I had stated the same N2, is equivalent to
~ 26000 cfm at 1 Bar (SCFM), or ~120,000 lbs of N2 per hour would it make any difference?
Since this become too custom project the parameters been looked into to get modified to be within more of common standard ranges available in compressor/blower industry.
RE: Compressor selection
No Mechanical losses included.
Rgds
Wimple
RE: Compressor selection
I ran a 70% polytropic eff and got 50HP. I assume a custom unit could get that efficency. Sundyne would be another good choice
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Sundynes typically run in the 50% range of eff, so it could be a 70 HP unit.
RE: Compressor selection
I went ahead an put in the JGR/4 (the program picked 7-3/8R cylinders with a 7-inch bore) and got 286 hp. I'm not sure that Ariel can really handle sub 1.1 ratios.
I tried it in Coolware and Rotosize, but no screw is going to work with that suction pressure.
The Sundyne looks like a good machine, too bad they don't have a calculator but I don't know of any centrifugal machines that do. My experience says that if a PD machine is between 200 and 500 hp then a dynamic machine will be a lot higher hp than 70 hp. I'd love to see RMSINT submit this application to a centrifugal compressor vendor and see what driver they recommend.
David
RE: Compressor selection
Most typical systems run about 25 psi differential and 2 MMSCFD. They have a 25HP driver.
Sundyne will size them up.
The oldest system I used a Swearingen as in Swearingen of RotoFlow and Unranium Centrifuge (multi-stage compresssor).