So set me straight. I am using the Appleseed method. Mine is a simple single out single in with a vent tube. It is all new components including a NEW 50 gallon WH. I have lately been reading about the venting aspects of the Appleseed and had some questions.

I've read that while filling up with the methoxide, the vent is to be opened. After that the vent is to be closed and left totally sealed while mixing, is this right? What type of pressure build up occurs at this time? I have not read any info as to what is happening, pressure wise, at this time. I know that when I mix the KOH and methanol initially, my carboys bulge out due to the pressure. I have to keep venting so the carboy won't explode. Because of this I am leary on totally sealing the processor for any time. I have always just left the vent tube open leading to the outside. What am I missing out on? How much methoxide/methanol escapes?

Hmmm... wouldn't you know it. Right after posting I stumble upon some posting by Dodgeram, Tilly and Rick stating insignificant methanol loss if vent is left open. What about letting it run some time sealed, opening the vent hose to relive any pressure, then sealing it and repeat however many times it takes?

I dunno if others do it also but I keep mine closed while the actual reaction is taking place only. At all other times it is open.
You can leave it open also, as there is insignificant methanol/heat loss.

artesp,

If you close the valve and do not heat while mixing, there will be a slight vacuum on the tank. I strongly suspect that leaving the valve open during mixing increases mixing time some. I do not know how much. Experience has shown that if the valve is closed and you have the heat powered, then it may pressurize to a couple of psi. If you leave the heat on while mixing, and the thermostat fails in the closed position, then it could build up some pressure until either the pressure relief opened or the plastic lines failed.

You do not, for any reason, want to leave the valve closed when the tank is empty. In a properly functioning appleseed, the only time there is a possible risk of over pressurizing the plastic lines or the tank is if the heating element is activated when the tank is empty and the vent closed.

In my latest Appleseed Design (scroll down for the updated version) I replace the valve with a 12" long vertically mounted pipe. I feel that the small risk of possible personal injury from having a fire in the tank with the vent closed outweighs the increased mixing times caused by not having the valve.

I've also addressed mixing and feel that an eductor mounted inside the Appleseed more than overcomes any increase in mixing times caused by not sealing the tank during mixing.

Install a reflux condenser on the tank top and vent the tank during the reaction through this device. it's very easy to make with a 5 foot piece of 1/4" copper tubing.

Hello artesp
The simple answer is if you have a heating element in the reactor there should not be a valve on the vent. The vent should be as big in diameter as possible and as straight as possible so that in the event of a reactor explosion the reactor is vented into a safe place and is less likely to blow the plastic hoses off. This has been reported to have occurred several times with the resulting spray of oil/methanol covering everything in the area.
Many tests by numerous people have shown that there is virtually no methanol vented during the reaction as long as the heater is not on. In fact the reported loss usually amounts to 50ml (1.7 oz) or less which would be less than the measuring error most people would have when measuring out the 8 gal of methanol used to react 40 gal of oil.
No one has ever demonstrated that there is an increased mixing time if the vent is left open. As Rick correctly points out there will be a slight vacuum form during the reaction if the vent is closed which indicates the minimal air movement will be into the reactor not out of it.

It would seem to me that you would lose lots of methanol if you leave the vent open during the reaction.

quote:

It would seem to me that you would lose lots of methanol if you leave the vent open during the reaction.

This was my opinion for a long time, but testing showed no measurable loss. Unless you are actively heating or actively putting air into the system, its a fixed volume of fluid/gas that doesn't exchange anything through the vent.

And then the sure-fire way to be sure is to just have ANY length of vertical pipe between the Appleseed and the outside. Even if its not a condenser, per-say, it will act as one and any condenser methanol vapor will roll back down.

Mine also acts as a good back-up for when I overfill...which I do a lot. rather than blow oil and methanol, outside, it just rolls up the clear tube, I see its overfull, and I stop. And if I don't see it right away, it just rolls down the line to the next vented item...which happens to be the settling tank, and the under-reacted oil just falls in there.

I agree with Tilly that a valve in the vent line is not a good idea, just use some form of condenser or vertical pipe like the others have suggested and you will be good to go, I see no need to EVER have the vent valved off and I even process with vacuum.
My vent line goes up through my condenser and into my methanol recovery collection vessel. I routinely process between 150F and 160F and have only ever noticed an ounce or so of methanol collect.
You can see my collection setup in this picture;

You can see the bottom of the condenser feeds into the carboy via the 1/2" pipe, the 1/2" pipe to the left goes to the vacuum pump. The rubber stopper is the safety, the vacuum will seal the stopper but any pressure will pop it out. There is no valve between the collection vessel and the reactor.
Jon

I should add that I also run my heater to maintain my reaction temperature throughout the process and it makes no difference in the amount of methanol that evaporates.
Also before even considering using a heater in your reactor you MUST have a safety to ensure the heater can never come on when its not submerged in oil...
Jon

So you're pulling vacuum while processing, and still no significant methanol vapor loss. I don't know what your batch size is, but if I lost an ounce of methanol in my typical 27L of methanol added, that would only be .11% loss. My measurement error is surely more than that.

quote:

I see no need to EVER have the vent valved off

I've said it before anytime anybody says they see no reason because my processing technique has a reason. I fill the processor with WVO using vacuum and empty the last little bits with pressure. No valve, no vacuum and no pressure.

Now, I could redesign my system to incorporate the methanol collection vessel like you have and use the same vacuum to fill with oil too, but as set up, my vent is closed to fill with oil, and then opened to heat the oil and never closes again until its done and emptied. Then I fill it with oil again so it rarely sits empty at all.

Hi Ryan,
My batch size is currently 100L using 22L of methanol.
I don't actually process while under vacuum. I use the vacuum to load the reactor, add methoxide, add acid, methanol recovery and for drying the oil. I use around 5Hg of vacuum to draw in the methoxide over about a 1/2 hour period and still only lose about an ounce.
Jon

Well, before this goes on and on let me state. I do respect everyone's input. Not really the input I was looking for. They are pretty much opinions and "this is what I do." While I trust your opinions and procedures I can't tell my wife, "...uh, because that's what they do."

I have noticed a clear liquid that I can assume is methanol that collects when my vent tube gets a sag in it. I have to be careful of this and keep an eye on it and make sure the tube has a constant upward angle.

On my next batch I plan to add an air pressure gauge up top. I will close the vent and note the pressure increase if any. If need be, I will relieve the pressure as the process goes on. What ranges would be WELL BELOW safety measures? I guess I should have worded it with that in mind.

Hmmm...
It seems you already have the answer to your question and you would now like someone to justify valving off your reactor?
Or, is your question what is a safe amount of pressure in the reactor?
If the latter is your actual question then be prepared for more opinions and speculation as know one here could know how much pressure your setup could safely take...
What exactly is it you want to tell your wife?
Jon

A water heater tank will more than handle normal operating pressures. Most/all have a working pressure of 150psi and a burst pressure of 300 psi. Look at what the TP-valve you took off the new water heater was rated for: that's the working psi. Most are 150psi, I think a few brand new ones are now 175psi. (ADDED: that isn't to say the rest of your plumbing can take those pressures, but the tank will.)

What the bigger issue is with keeping the vent closed is the abnormal operating pressures: explosion. Accidentally lighting off even a small explosion inside the steel tank can cause a pressure wave that will either a) exceed the burst pressure, or b) not exceed the burst pressure, but occur faster than the replacement 5psi TP-valve that you should have on your Appleseed can react. What can happen in case b) is a fitting, usually anywhere there is a plastic line to steel line adapter, can blow off and spray WVO, methanol, and/or biodiesel all over the place.

This will occur faster than you can possible hope to see the pressure increase and manually open the valve. Accidents usually happen fast. Slow accidents are nicer, but far less common, for some reason, than the fast ones!

quote:

On my next batch I plan to add an air pressure gauge up top.

If you turn off the heat before adding the methoxide like is recommended everywhere, then you will need a vacuum gauge. (FACT, not opinion)

If your equipment is operating properly and you leave the heat on while mixing, against everyone's recommendations, then it might go as high as 2psi. (Fact, not opinion)

If you have multiple equipment and procedural failures and leave the heat on while mixing, it is possible for the pressure to reach unsafe levels. (FACT, not opinion)

Safe maximum pressure is an opinion. Opinions range between 0psi and 30psi.

quote:

I have noticed a clear liquid that I can assume is methanol that collects when my vent tube gets a sag in it. I have to be careful of this and keep an eye on it and make sure the tube has a constant upward angle.

You can eliminate the sags by supporting the tubing. zip tie it to something like a pvc pipe or a 2x2 wooden stick. (Suggestion)

Ryan,

That makes sense. I can fore go the gauge expense then. I was thinking that normal operating pressures were a concern and forgetting the "abnormal operating pressures". Sounds like vent or no vent an "abnormal operating pressures" explosion would be messy.

Jon,

I don't have the answer, never really wanted to valve off my reactor just read its supposed to benefit/help the conversion, and don't worry what I tell me wife.

I just believe there is always something new to learn.

Rick,

Makes sense as well on the operating pressures. For the record, I heat to 130' turn off element and add methoxide. For some reason my mixture at this point gains another 8 - 10 degrees so it tops out at about 140' for the remainder of the process.

I have my WH at one end of the garage and the fuse panel at the other end. I was able to wire it 220v with a switch in its path. I turn off both the fuse panel circuit and the manual switch at the heater when not in use. It takes me about 30 - 40 minutes to heat 30 gallon of oil this way.

quote:

off element and add methoxide. For some reason my mixture at this point gains another 8 - 10 degrees

That's normal. It stops going up in temp when you stop adding methoxide. It can not cause a pressure increase since you need the valve open while adding the methoxide.

Hello artesp

quote:

Originally posted by artesp:
Sounds like vent or no vent an "abnormal operating pressures" explosion would be messy.

It certainly could be. There is no guarantee that the vent line will be big enough in diameter to prevent the overpressure that will occur in an explosion from popping plastic hoses even if it is open and does not have a valve. The safest thing to do is to permanently remove the wires going to the heater in the reactor and heat the oil in a container that will never have methanol or methanol vapors in it.

The TP valve on a water heater is designed to respond to the slow increase of pressure and water volume that will occurs if the thermostat fails and excessive heating occurs to water, not for the sudden increase in pressure and large volume of gas generated during a methanol explosion. Unless the safety valve installed in your reactor is specifically designed to handle explosions then it may not be providing you much safety.

quote:

I don't have the answer, never really wanted to valve off my reactor just read its supposed to benefit/help the conversion

There is an absolute wealth of misinformation on the internet concerning biodiesel production. I am personally convinced that I get better results when I intone "The happy Biodiesel Warriors Transesterfying Chant" while mixing. I have no numbers or meaningful test results to support this conviction.

quote:

For some reason my mixture at this point gains another 8 - 10 degrees so it tops out at about 140' for the remainder of the process.

The transesterfying chemical reaction is exothermic (it gives off heat} This rise in temperature has been noted by forum members a number of times.