Compressor selection 2

[RMSINT]

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

 

[zdas04]

What is ICFM? Is it CFM at inlet conditions or something else? When I googled it the first response was "International Convention of Faith Ministries" and I didn't think that was right.

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

 

[pmover]

perhaps there are alternatives to the process such that the end result can be achieved. however, the description of the process, process conditions (i.e. flow & inlet/outlet P & T), and the desired results are needed for any assistance to be provided.

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

 

[zdas04]

pmover,
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

 

[wimple]

ACFM (Actual CFM) unit be more correct.
Could you give some precisions about the application in itself? (type of HX, purpose of application, description of the loop etc)

Thks
Rgds
Wimple

 

[RMSINT]

As mentioned by David I had just enough info for selection and calculating HP.
Thanks David for the valuable answers.
ICFM stands for Inlet Cubic Feet/ Minute
Regards
Raj

 

[ARenko]

Since David answered the question I'll just add comment on ACFM vs ICFM...

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.

 

[zdas04]

djv,
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

 

[ARenko]

David,
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.

 

[zdas04]

ICFM is the same as ACFM at inlet conditions. I guess I'm not getting your distinction.

David

 

[ARenko]

I guess I confused things by taking about an air compressor taking atmospheric air. This is different with the pressurized suction and I, like you, mostly see scf in this case. To answer your question...

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.

 

[dcasto]

by the way, its 50 HP compressor. It's a fan blower. if the polytropic efficency goes form 70% to 25%, the enrgy goes up to 140 HP. look up blowers.

 

[RMSINT]

Hi dcasto
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

 

[wimple]

Gas power is about 40-50 HP.
Rgds
Wimple

 

[pmover]

been awhile since visiting the site . . .

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

 

[dcasto]

google high pressure blowers

http://www.spencerturbine.com/products/blowers/custom-blowers-gas-boosters/default.html

 

[RMSINT]

Thanks to Dcasto for the input on this and suggestion. I will be in touch with Spenser for application assistance
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?

 

[wimple]

consider the answer HP I submitted is the correct one
Dcasto is correct as well.
thats it

rgds
wimple

 

[zdas04]

Dcasto,
I went to the Spencer Web site and on the custom applications I found:

Spencer solves air and gas handling challenges that are so difficult, sometimes the only alternative to our involvement is to change the process. When you don’t have that option, Spencer capabilities and our Engineering Edge are your best resources. High-performance blowers and gas boosters can be built to handle corrosive and toxic sulfides, halogens, acids, flue and stack gases, cyanides and ammonia. Maximum parameters include temperatures to 1100°F, housing design pressures to 1000 PSIG, operating pressures to 300 PSIG

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

 

[RMSINT]

With my limited know how tells me there can be only one theoritical BHP for this needs ,w/o considering efficiency.
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.