Hey guys we are currently using an aquarium pump to dry our fuel. It runs down into two small bubblers in the bottom of our 250 gallon tank. We make around 120 gallon batches, and the longest part of our process is the drying. Is it possible to speed up the drying process? Would adding another pump make it faster? It normally takes between 3-5 days to go from freshly washed (about 150 gal water to 120 gal fuel) to crystal clear.

 

Curious as to how you are measuring dryness?

 

Well we might be slightly outdated or off, but when we were taught a couple years ago by a U of I professor he told us if we could see the bottom of the tank through the fuel perfectly (clear as water) it was ready to run in our trucks.

 

You could easily still have a lot of suspended water in your bio. I have three tests, performed while I still have my bio spray drying at 140F. One is to put a sample in the fridge and do look for wisps of moisture suspended when it gets down to temp. Another is weigh-heat-weigh, where I weigh a sample, heat in microwave until around 220F, weigh again. Yet another method is the vapor test where I place a shallow container with the bio in it, such as a tea cup, and set a small square of glass on top, heat to 220F, and look for a ring of condensation around the rim. I don't think clear bio is an indicator of moisture free or soap free,for that matter.

My batches are less than half of yours, at 45 gal., but what I do to dry is circulate in my drum processor with a spray dry fitting until it reaches 140F, shut off heat and continue circulating. Takes around 2 hours depending upon ambient temperature.

Like this (except that I have a spray dry fitting screwed in which fans out the bio):



Spray dry fitting at top of photo:



Hope this helps.

 

So you just do the spraying dry process after washing the fuel and thats it? Ive never heard about spray drying but then again I should probably do some research since I havent checked in a couple years. Are you just using a water heater element in your drum to heat the fuel to 140F and continue to let it circulate?

 

Yes, after washing, it goes back into my drum processor (with a water heater element), and circulates via spray against the side of the drum to expose the heated bio to as much air as possible until it reaches 140F. It is at that point while I continue to circulate it that I begin my testing. Humidity can lengthen the drying process but here in western washington, it is not usually a big factor.

 

Whats the significance of 140F?
And thanks for the info this is very helpful.

 

140F is at the upper limit of my heating capability. More importantly however, given my set up, ambient temps, average humidity level, etc., it has proven to work for me to get to that temp. Testing done at lower temps take longer to pass moisture tests. Unscientific proof to me at lower ambient temperatures shows little steam coming from the drying process at say 125-130F, wheras when I bring it up to 140F I'll see steam rising from the drying process.

So total drying process to 140F, couple hours or so, is a routine that works for me and the set up I have.

 

By the way (and I meant to bring this up earlier), when I am at the final wash, and the bio is settling prior to transfering to drying tank, I can look down into my wash tank and see clear down through the bio to the water layer. Clear as a bell through a few wisps at the interface layer, I can easily see my bubble ring and heating element. And as clear and sparkling as it is, I am 100% sure that biodiesel is quite wet.

 

How much water are you running through your batches? We're running around 150-200 gal thru 120 gal of fuel, but its nowhere near clear after its been washed. Are you using KOH or NaOH? Just trying to figure out how come we arent gettin clear fuel after the washing stage like you are. It doesnt clear up until after a few days or air bubbling.

 

That sounds darn close, ratio-wise, to my current process. For a 45gal batch I will average 50-65gal water over 5 or so wash cycles. Now I also realize I am behind in terms of advancements in bio making. My methods and technology are probably 5-8 years old. Even my water washing method. It's considered old school. Properly set up, I could cut my water use by half. But I digress. Here's how it goes for me:

-Single stage reaction, 135F, 20% methanol, KOH, (I pre treat wvo with glycerol) My titrations average 2.5-4.

-After passing 3/27, usually 2 hours, shut down and settle 1-2 hours, empty glycerol into 2 cubies for later use.

-Pump reacted bio into wash tank with about 5 or so gallons of water in bottom for a static wash. After 2 hours or so, drain water, turn on heater, mist wash with about 10 gallons water, 120F. Settle couple hours, drain, repeat.

-After the second mist wash, the bio looks like orange juice. Keeping the heat on, I'll put the lid on the tank and bubble overnight. The next morning it should be beginning to darken and become more translucent. Settle a few hours or more. Drain, and this time I will just pour the water in with a bucket. Repeat overnight bubble.

-By now I'll do a quick shake 'em up test, (equal parts water:bio, shaken hard in a glass jar and allowed to settle 30 minutes or so). The interface layer will tell me how much remaining soap there is and is an initial guide as to when I can stop washing. (When I see no layer between the water and bio, then I'm done washing, and on to drying. If I see any white layer, I keep washing).

Now if I were to do all of this non stop from beginning to end, it would take me about 3- 4 days to completed bio. In reality, I break it up over the course of 1-2 weeks depending upon what else I have going on.

Hope this sheds some light on the matter.

 

Our process is slightly different. We react around 150*F and use NaOH, and washing is more of a one step process. We dont do any heating after the reaction and just mist wash a few times til we get about 170-200 gal thru. All in all it takes about a week for us to get fuel made, but we have the capability to start a reaction while washing/drying another, so we can make up to 250 gal a week. We've got 3 trucks and some farm equipment we try to make as much as we can. But thanks for your help it certainly sheds some light on the manner. Ill have to do some research and do some upgrades this summer.

 

If you don't already belong to this forum, here's a link to a great one:

Biodiesel & SVO Home

Some great information in all areas of biodiesel production. Like FTE, there's way more information there than I'll ever see.

 

Thats just what I was looking for. Thanks for the help I appreciate it. Looks like Ive got a lot of reading to do now.

 

Pardon me for jumping into the conversation, but another tool to help speed up the drying process while bubbling is to run a small fan across the top of your open drying tank to help the air in the room absorb moisture from the bubbling process. I run 25- 35 gallon batches with KOH, washing three times with 10 gallons of water. After I get the translucent, clear biofuel I run the bubbler and fan overnight and it dries nicely.