2 replies to this topic

[musrey]

Need a manufacturer recommendation for a compressor to move 8000 ICFM of methanol vapor at 15.7 psia and 155 F to a dsicharge pressure of 60 psia.

Any simple way to factor cost versus compression ratio bwteen 4:1 and 2:1 ?

[Art Montemayor]

I don’t have the Thermophysical Properties of methanol handy at the moment. However, I know the vapor pressure of methanol at 155 oF is 880.4 mm Hg or 17.0244 psia. Therefore, your methanol vapor has some superheat and can be dealt with as a vapor and compressed.

I presume that your acronym “ICFM” means Inlet cubic feet per minute”. If so, this means you have a stream of 11.5 Million cubic feet per day at suction conditions. This is a very large vapor stream of methanol and you probably will require a machine such as a screw-type compressor. However, knowing the properties of methanol, I fear that you won’t be able to tolerate an oil-flooded model. This means that you will have to employ a “dry” screw and suffer the internal leakage and inherent inefficiencies. A lobe-type compressor is more of a blower and you probably won’t get the 3.82 compression ratio you seek. A centrifugal compressor is an overkill and you won’t find one that small in capacity. A reciprocating compressor is an overkill in cost for the discharge pressure you need. I think you are probably facing a dry screw compressor application. There is no “simple” way to factor the cost of such a compressor with respect to the compression ratio. The machines are pre-designed and have standard “frames” built to suit a capacity range. The cost of the machine is primarily based on the manufacturer and the firm quote that you can extract from him/her.

I’ve never tried to compress a methanol vapor and I fear you are going to have a tough application controlling the lubrication of the machine, its cooling, and capacity controls. Finding adequate seals might be another problem. You may wind up with a prototype machine in a new application and have to pioneer the results.

Compressors manufacturers that I would recommend you consult with would be Howden, Mycom, and any Lysholm licensee. These are very specific and specialized machines and I wouldn't try any make that doesn't have at least a 20 year track record.

Sorry I can’t help you out with experience in this application.

[djack77494]

Might be simpler to condense the vapors and pump them up to the desired pressure. Both those tasks would be quite easy, and I'd think they would be attractive IF you do not need the methanol in vapor form. Even if you want a vapor, perhaps you can come up with an easy way to produce it.
Good luck,
Doug