Dry air before compressor pump?

[johansen]

Heat doesnt push moisture out, quite the opposite. Air at 100deg F holds 10x more water than air at 30deg F, for reference.

Its clear you dont understand what im describing.

The 200+F air coming out of thr compressor will heat up the dessicant and push all of that moisture out, into the cooling coils and into the tank.

When the dessicant cools down it regains its ability to absorb moisture.

The three tubes have to get cycled through the system.

 

[Cole2534]

Its clear you dont understand what im describing.

The 200+F air coming out of thr compressor will heat up the dessicant and push all of that moisture out, into the cooling coils and into the tank.

When the dessicant cools down it regains its ability to absorb moisture.

The three tubes have to get cycled through the system.

You are correct, I wasn't reading that properly. You're using the heat of compression to regenerate the saturated desiccant bed.

That process is exactly how we regen the mole sieve beds at our NG processing facilities, it's proven to be effective.

 

[FredC]

Not to hijack, but I got a surplus Ingersoll Rand T30 which has a heat exchanger coil in the line between second stage and tank. It was used to operate dampers in a HVAC system on a large building. This coil receives air at the top, hooks to tank at bottom, has no drain on coil. Looking at brochures this is not standard equipment. What does it do? Dry the air?

This is where I added a heat exchanger and drain. Between the 2nd stage and the tank, the air goes in above 220F and comes out at ambient air temperature. In the summer that is a at least a 120F drop. After the cooler is where I added a water collector with auto drain. Sems like the most cost efficient place to get a large quantity of water out, it only takes a very small fan on the coils to accomplish this. I have to believe the refrigerated dryer inside the building is using less power, is doing a more efficient job, and will last longer since the bulk of the water has already been removed before the air gets in the building.

 

[TaperPin]

Here's an interesting snippet on this, from the Engineer's Toolbox- https://www.engineeringtoolbox.com/water-content-compressed-air-d_1275.html

That‘s a great article - just looking at the charts it’s clear to see it’s much much easier to get water out of the compressed side with temperatures that are readily attainable.

I‘ve never felt the need for a two stage compressor since my air needs are only 120 psi max, but that same chart seems to showsthe higher pressures out of a two stage pump would end up drier than a lower pressure single stage if all the dewatering efforts were the same. Interesting - It makes complete sense, but hadn’t even crossed my mind until now.

Along other lines, it also just dawned on me that a refrigerated drier that transfers heat via cool air flowing between finned coils is also very much dehumidifying the ambient air as it passes over the evaporator. I’m thinking of routing the air inlet to the compressors to the air stream after the coils. It won’t be very cold, but it will have less moisture than general ambient air with only the cost of routing a supply duct to the inlet filters.

 

[EPAIII]

The technique I described above did work in cities like New Orleans and Miami where humidity was a big problem. I can't prove that every part of it was absolutely necessary nor can I say what percentage of the moisture each part eliminated. I do know IT WORKED.

Oh, I was born in New Orleans and lived there for over 20 years. I have been to Houston many times and presently live in Beaumont, Texas which is about an hour's drive east of Houston and closer to the Gulf. New Orleans has at least twice the humidity of either of these Texas cities. And New Orleans is where I developed my compressed air systems. They work there and as far as I know that is the worst humidity in the country or very close to it.

Air compressors, at least the larger, industrial ones usually have air intakes that are threaded for standard pipe sizes. So it is easy and inexpensive to pipe the intake to an air conditioned space, even if the compressor is located in an outside shed. And, after the first foot or so, which should be metal pipe due to heat and vibration, PVC pipe is more than adequate for the task. The room where the compressor sits does not need AC although it does not hurt and may even prolong the compressor's life. Just the point where the air is taken from.

The OP is correct in that an ideal installation will draw air from the outside. If you were located in a cold place, the air would generally be dry and also more dense and the process of compressing it will become more efficient. What you do in Houston is completely beyond me.

metalmagpie

 

[Bakafish]

I have a tiny Jun-Air 6-4 silent compressor and an SMC IDG3H-02 membrane type air dryer. This dryer uses bypass air to separate the moisture, so it basically always leaks when pressurized so it needs a seperate valve to keep it from draining the tank when not in use. It's not a big problem for where I intended to use it, as that application (NSK 3000 spindle) has a solenoid controlled valve that only opens when in operation and I can put it upstream of that, but I've been wondering if I put this unit between the compressor stage and the tank would I be able to pre-dry all the stored air? That line is at atmospheric pressure when the pump is off, so I'd only be losing air to the bypass during filling and not have to set up additional valving. I would only lose a little efficiency on the refill and in theory have dry air in the tank and for all of my other usage.

Would this work, or am I missing something?

 

[Lewie]

:-) Or just move to Albuquerque. :-) The RH runs from the single digits ( I've seen it as low as 3 % ) to the upper teens most of the time. It rarely get to the 20 or 30 pct.
...lewie...

 

[TaperPin]

I put this unit between the compressor stage and the tank would I be able to pre-dry all the stored air?

No. That water separator only removes moisture that’s ready to condense at whatever temperature/pressure the air is at. At the higher temps coming off the compressor head much of the water is not ready to condense yet. If you were to have a cooler after the pump but before the tank then your filter would work.

The catch is that the unloader is designed for short section of tubing between pump and tank check valve and it may not work fast enough with heavy air usage. The fix is to change the location of the check valve so it’s on the pump side of the cooler, not the tank side.