Sizing a new dessicant dryer

[foodprojengr]

We just had a new 150 hp rotary screw air compressor installed with a 350 cfm dessicant dryer which includes a heater, blower, and dew point monitor.

There was some confusion on the rfq I initially sent out and the vendor claims he thought I intended the dryer to be sized to our average capacity. We did an air audit 1 1/2 years ago that showed our average air capacity was 255 cfm and our maximum was 867 cfm. We currently have a 200hp compressor and a 1000 cfm dryer, both of which are oversized for our operation here.

We intended to run our new compressor and dryer primarily, with our older units as backup, so I don't want to be put in a position where we have to run the old dryer because the new one is too small, then we won't have true redundancy.

My sales rep is telling me that if we exceed the dryer's capacity it will increase the dew point and as long as it doesn't go above ambient temperature, we won't have a problem with our plant supplied air.

Does that make sense? I hate to do this b/c of the hassle and additional expense, but I'm thinking I should have this sent back for a larger dryer. How would you size the dryer in this situation and do you think it's reasonable to think we'll be ok with the smaller dryer, given that we rarely get below 20F here in Savannah?

Thanks in advance.

Dave

 

[zdas04]

What is the technology of the dryer? Some sorts can easily let dew point drift a bit to give you additional capacity, others can't.

David

 

[foodprojengr]

It's a pneumatech heat reactivated dryer with a spencer vortex regenerative blower, what else would be helpful in identifying the technology to answer your question?

 

[zdas04]

I've used Pneumatech Mole Sieve driers in natural gas service and to get more gas through them I only had to increase the regen heat (nearly up to the max allowed) to get to a dryer starting point. This wasn't terribly effective for my application because I had to use natural gas for regen gas and it was pretty expensive to vent.

TSA (Temp Swing Adsorption) units can be hard to get REALLY dry, but by jacking up the heat you can do a lot. I'd look into your regen temp, max allowable, and how you heat the regen air. There may be spots in there to improve processes to get more capacity.

David