Living with a Greasecar ...help me fight condensation

Ok folks I'm at a loss here. I'm having a hard time understanding what's going on here and am turning to the collective minds here..... Ok, get ready for a long story, though I'll try to keep it short. I'm running a centrifuge (CF from here on out) and love it. Back in the summer I was getting condensation in the hose coming out of the CF going into my "clean barrel". The hose in question is a 3/4" hose that only has a small amount of oil in it, so there's lots of air in the hose, 7/8 of the volume I'd guess. I called the CF folks and they said they hadn't come across this issue before. They said I should remove the two plugs on the lid of the CF allowing airflow through. That didn't do anything really. I then put a plastic "T" on the hose right at the CF out fitting. This did the trick. I'd actually see vapor leaving the "T".
Cool................until yesterday. I have condensation again. My questions are: 1) Why 2) How to avoid it. I don't know the actual temp of the oil flowing through the hose but I'm sure it's 100 - 130 degrees F higher than ambient temps right now. After everything cooled down yesterday I tried using a hair drier to warm the hose and filtered again. No condensation. So I have two ideas: 1) Put a gate valve at the output of the HOSE, keeping the hose full of oil all the time thus having no air space in the hose at all. The only draw back is when I adjust the flow of oil into the CF I"d have to match that flow at the output hose or I'd overflow the CF. 2) Heat tape on the hose to warm it up. If I take option #1 I'm afraid I'd move the point of condensation from the hose (where I can see it and know it exists) to the "clean barrel" where I couldn't see it. The volume of air to volume of oil ratio is waaaay different when we're talking about an empty 35 gallon barrel though. Here's a pic for reference. This pic doesn't reflect the plastic "T" I installed or the reinforced hose I just recently switched over to after my BP oil spill.

I hope all that makes sense....

Condensation happens when the temperature drops, so I say the (short term) key is keeping things warm. Maybe insulate your aluminum centrifuge pot (aluminum is a great heat conductor) and as you mentioned use one of those heat tapes to jack the centrifuge temps up a bit?

But here is my question: how is the moisture getting in in the first place? Seems like that would be the logical place to attack first. I was under the impression (not real familiar with greasecars, so bear with me) that lye was added to the grease to prevent this?

A Nitrogen purge when the rig is not in use?

Jensenman, you are thinking bio-diesel. I'm running straight veggie oil. I have no clue where the water is coming from. I'm assuming and guessing that the air that's in the hose is humid. So when the hot oil warms the air the water condenses but I really don't know. The oil isn't wet. I have done a water test before and after that hose. Before the hose it passes with flying colors, after the hose it fails miserable. Triumph, tell me more of what you speak. But know this, the whole rig is open to the atmosphere through vents....

I was thinking maybe you could put nitrogen in the lines when the system is not in use, thereby getting rid of air with moisture in it. But, with the entire system open to the air with vents, that goes out the window.

You have to, somehow, minimize temperature cycling in your garage. Or, somehow, when you process the veggie oil, IMO.

Hmmm. The water has to be getting inside your system somehow. It's either included in the oil you are getting or being introduced during the cleaning process. If the oil has no water in it during the cleaning process, there should be no water in the (colder) tubing, water that's not present can't condense.

Is there any way you can heat the feedstock oil past 212 degrees while it's open to the atmosphere? Your water should boil away at that point and I am assuming you are pretty close to sea level.

Also, assuming there is no water in your feedstock oil, go over your rig step by step and try to think of where water could find its way in. Vents are all well and good, but they can work both ways: both remove and introduce atmospheric moisture. Maybe that's how it's getting in.

The point is, if there is water in the oil before it hits the centrifuge then it will of course condense out as the temperature drops. Meaning you are seeing the symptom, not the disease.

Another looong shot: moonshiners for years used a coiled copper tube over the mash tank to condense alcohol out of the heated mash. Can you add something similar to the top of the centrifuge? Warm moist air would rise to the top, then the water would be condensed out and drip out of the end of the tube.

The answer is that you live in MI.

Warm air has lots of moisture in it. Cool air does not. The dew point is the physical point where the temperature is correct to condensate. Right now, that point is on the inside wall of the tube, so it condensates on the walls of the tubing.

Your relative humidity in MI right now is probably nearly 90%, with ambient temps in the 30's. In the summer, you were probably more like 70% humidity with temps in the 70's.

The differential between the warm moist conditions in the tube and the cool outside of the tube are creating the condensation on the moist side (inside).

Insulate the tubing. When the tubing is the same temp as the air inside the tube, it won't condensate anymore. You already proved this with the hair dryer.

BTW, you should also tightly wrap the insulation with a moisture barrier (and seal the joints). If you don't, condensation will form in the insulation. Maybe soggy insulation won't matter...

Next, install a second "tee" near the clean barrel, with a clear nipple and a drain cock pointing down. Water will settle in the tee (because oil is lighter than water) where you can see it, and can be bled off occasionally.

You could also put a water separator before the clean barrel. This would be wise (though not necessary), because some moisture is going to transfer to the clean barrel simply because it is in the form of humidity in the air. But no point in doing that until after you insulate.

If you set the clean barrel vertically, the water will settle to the bottom, and can be bled off through a drain cock near the bottom.

Here's a better system- accept that water will enter the system. Add another step. After CFing the oil to the clean barrel, funnel it through a separator funnel. Large barrel with a taper, funnel shaped bottom and a drain cock at the bottom. Water will settle to the bottom- bleed off.

SVreX has hit on it, I do believe. Not sure where you will find a reasonably priced funnel shaped container though. You could always just stand the 'catch tank' on end and put your fuel drain tap, say, 3" above the bottom with a second condensate drain tap on the very bottom to bleed off water.

As SVreX says. Insulate the tubing. The stuff Lowes or HD sell for house plumbing should work.

You can make a separator funnel out of a plastic 55 gal barrel.

Go to any tractor supply company, and they will have fittings designed to be installed in a plastic tank. Usually has threads that go through the hole with rubber gaskets and jam nuts on both sides.

Install the fitting in the bottom of the barrel.

Mount the barrel on a rack or table, install a piece of clear tubing on the fitting with a valve at the end. You will be able to see the water level in the tube. Drain into a bucket.

Would work best if the barrel was tipped, and the fitting was installed at the low corner.

BTW- you had water in your fuel before too. It was smaller quantities, and you just didn't notice it.

You were filtering it out in the onboard water separator in your truck.

Had to be, in an open to the atmosphere system.

Add the funnel separator to your system and everything will be happy.

Use a drying media to dry the oil before it enter the clean holding tank. The drying media has a bunch of crystals like in a beef jerky container, as the oil passes through the media it will lose it's moisture. You need to find out what type of drying media to use for oil and what size of drying container you'd need, it is like a see through container with colored crystals in it.

Here’s my thoughts after reading the above.
I may just do the copper coil because it makes it look even more like a still, that’s what everyone calls it so I should make it fit the part. I think the issue is with humidity and temps. The humidity is about 70% right now, but it’s cold. When I introduce warm air won’t that cause the moisture that’s in the air to collect on that cold hose, just like the (much higher) humid air in the bathroom collects on the cold mirror after a shower? As far as insulating the hose, I’m not sure what that would do. Let’s say I’m filtering right now. The air inside the hose is 150 degrees. Then the rig sets for a few days. That hose will be ambient temp the next time I use it and I suppose I’d have the same problem. There’s no water in the oil before filtering. The test I run even find emulsified water down to a few hundred parts per million. The oil I tested before the hose passed with flying colors. The sample after the hose had visible drops of water in it, some as large as 1/8”. Here’s what I have been thinking. Get an old computer fan and duct it so it’s pulling air out of the CF lid. Since the CF, that hose and the finished barrel share the same air won’t pulling air through them stop this from happening??? I’d also like to be clear that I’m not knocking anyone’s suggestions by any means. I’m at a loss and lack the knowledge to really understand what’s going on here. As a group I’m sure we can figure it out. I’d also like to say thank you all for taking an interest in my goofy ideas and helping me out…….I’ve been thinking about a grease-powered challenge car…….

Insulating the hose will move the condensation point out of the oil. Just like a cold beer can condensates on the outside, you have warm humid air in a hose. The hose is cold therefore it condensates. If you insulate it then the hose will be warm and like a warm beer, no condensation. For condensation to occur there has to be a temperature difference, insulation will move that point outside the hose. Probably into the insulation itself. There will probably be some condensation when starting the process, but once the hose comes up to temperature it should stop.

No, I'm not an engineer, no I didn't stay at a Holiday Inn Express last night. There is a fair chance I don't know what I'm talking about.

3 years experience in a chemical plant building and constructing stills, condensors, distillation columns, decanters, and other similar processing equipment up to 10000 gallons in size.

Yes, we made biodiesel.

But you are welcome to disagree with me if you want to.

Your above example of the ambient temp in the tube after several days of non-use is missing the point. You will be heating the inside of the tube. The exterior will still be cold. You need to protect the heated area from the unheated area.

The water is NOT coming from your oil. It is coming from THE AIR.

Your computer fan idea is kind of silly. A fan cannot blow air out one end if it does not pull it in the opposite. In other words, it will be pulling fresh air into the system from somewhere else.

Unless, of course, you are trying to create a vacuum. You will need something significantly more efficient than a computer fan to accomplish this (and it won't work. Condensation still happens in a vacuum).

The only way to avoid introducing moist air to the system is to have a sealed system. Sealed system + heat = BOOM.

Forgot to mention...

Most oils are hygroscopic. That means they absorb water.

Starting with water-free oil then exposing it to heat and humidity in the air is pretty normal to end up with water in the oil.

Alright Paul. I'm eager to discuss this with you since you have some experience. I agree that the water is coming from the air, but more specifically I think it's coming from the air in the tube since the oil fresh out of the CF is dry. So here's the question, how to I stop it from happening? My idea about the computer fan was to get air circulating. The CF, the hose and the "clean" barrel share the same air. The barrel is vented to the atmosphere so I was thinking I'd have a draft and that might stop it from happening. I have no idea if it'll work, I'm just grasping at straws here. The kicker is. Other CF users may or may not be experiencing this. Most folks use PVC pipe. Either the pipe insulates better or (I fear) they just don't see the condensation. But the problem is, the greasers aren't as quick to brain storm to solve a problem. Would making a "trap" similar to the one under the sink help? That way the oil would stop air flow through the system? Maybe one at each end of the hose?????

Can you tell I'm grasping here?

Greasers?

I didn't think veggie oil was hygroscopic. But as many will attest I've been wrong before and I'll be wrong again. I'm thinking that your heated oil goes into the CF, gets flung around to separate particles and in the process either water is introduced there or, if oil is hygroscopic, it starts coming out of suspension. You see it next in the (cooler) drain hose.

I had another brain wave (or fart, perhaps): what about running your drain from the CF to the 'clean' barrel through a sink trap type of arrangement? I would think the water would settle to the bottom of said trap, then you could drain it off before it hits the clean barrel. It would need to be clear so you could see what's going on; maybe you could adapt a water separator like those for compressed air systems?

I guess what I'm trying to say is water is a part of the process. It's normal and, like you said, it's all the same air.

Consider what is going on inside the CF- You are breaking the oil into small droplets and flinging it through the air. These droplets have a lot of surface area (which increases the ability to absorb water). Then, the droplets are flung against a (cold) metal surface at high speed. The force of the droplets through the filter creates friction and heat, then they mist against the cold metal of the canister.

Picking up moisture from the air is normal.

The only thing that has changed is that you now have optimal conditions for moisture in the air. The temps and humidity levels are just right.

So, you are seeing more water. Did you ever test for water before in the final product? I'll bet it was there, just in smaller quantities that you didn't notice.

Is there a reason to not consider a separator? De-watering is a normal final stage of biodiesel processes.

My concern is that if you include a trap, it will not remove the water (because it's all the same air), and you create the potential for a sealed heated system, which could under the right (or wrong) conditions create a catastrophic condition.

You need the vent. That means you are working with ambient air.

Your setup is the first one I've seen with the collector tank horizontal. Most are vertical, which enables the easy installation of a bleed valve at the bottom to drain off the water.