From Graham Lamming's site on the eco GL biodiesel processor, which by the way is a sealed processor that is vented:
"The GL Eco Processor vent - suck or blow?
The no.1 question people ask me is...
Is air more likely to be sucked in or blown out of this vent?
Neither! There is as much suck as there is blow, so nothing goes in or out of the vent. You can't have air going in both directions at once.
So if nothing goes in or out of the vent can I just close it off?
NO! The vent MUST be open to ensure the whole process runs at atmospheric pressure at all times.
If by accident the methanol were to boil due to a faulty thermostat, for example, you would not want a pressure cooker full of hot oil, caustic soda and methanol."
I think Biolandy, that you are confusing the term sealed - it doesn't mean that nothing can go in or out of the reactor, otherwise you wouldn't be able to get your oil and chemicals in.
It means that the reactor is one whole unit, sealed but vented. You add your oil via a connected pipe, you add your methanol and chemicals via another pipe that mixes through a venturi joint.
It is THE SAFEST way to make biodiesel. Because of the hazards involved in exposure to the chemicals you want to limit the time that those chemicals are exposed to the air you breathe. Best not to have a reactor where you take the lid off to pour the chemicals in, or a reactor with no lid.
The only open vessels ideally should be the tank where you heat and dry your oil and the settling tank, where you bubble the biodiesel to get the last of the excess methanol out. The reactor shouldn't be an open vessel.
The most dangerous reactors out there are open vessel reactors that people flog off on ebay - basically an old oil drum with a central heating pump attached to it and an immersion heater - £400 please. I'm not kidding, this cr*p is often the stuff people think is safe and it isn't.
GL reactors have been around for long enough now for people to know that sealed vented units made from metal, not plastic are the safest way to home brew. Graham Lamming is so kind he even publishes the diagrams, instructions and parts lists for free
GL's Eco-System state diagram
If there was the problem with them that you think there is then someone would have twigged by now. GL reactors are the basis for the majority of homebrew reactors out there - go on vegetableoildiesel's forum and ask.
But please don't make out that it's a lack of understanding of basic physics.
I don't claim to know all of the physics involved, but the people who have vast knowledge of the technical and practical aspects of designing and building a safe plant have explained these points over and over again on that forum.
I think you'll be hard pressed to find many people on there recommending anyone makes homebrew biodiesel with an open reactor or one with a lid on it. Maybe there's a couple of them who are in the first stages of methanol poisoning that would agree though.
