An Introduction to
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For those trying to lower the production cost of biodiesel, methanol recovery is a common practice.
Excess methanol is used to push the transesterification process to completion. The excess methanol can be recovered from the glycerin by-product through the use of heat and a condenser.
How It Works:
After the biodiesel has been produced, about 70% of the methanol left over will be found in the glycerin by-product. Boiling the methanol out of the glycerin within a closed container and funneling it into a condenser can recover this portion.
Recovered methanol can be used in the next batch of biodiesel but because it is not as pure as the original, a bit more will be needed (how to calculate purity is at bottom of page) and some extra catalyst as well.
Approximately 30% of the remnant methanol is in the un-washed biodiesel. It is generally agreed upon that it takes too much energy and time to be worth reclaiming this portion. Just wash the biodiesel and
repurpose the waste.
Tips & Quick Facts:
• Methanol boils at 148.5°F (64.7°C).
• Do not heat heat the glycerin mixture in an aluminum pot as the methanol will corrode it!
• The methanol should be removed only after the glycerin has been separated from the biodiesel, otherwise it could cause a reverse reaction.
• If you intend to separate the glycerin into its different components, that should be done before the methanol is removed. (Some reactions rely on the methanol in order to take place.)
You can build your own reflux still by following the instructions on this website:
Test the Purity of the Methanol:
Methanol needs to have a purity of 95% or greater to avoid problems caused by having too much water in the batch.
To determine the purity of recovered methanol, use a hydrometer (about $25 USD) to measure the specific gravity. 200 proof is pure methanol, 0 proof is pure water... so 100 proof would be half and half. I'm sure you can calculate the rest :)
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