What is the methanol effect on biodiesel?
Sunday, September 5th, 2010 at
12:41 pm
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Tagged with: methanol
Filed under: Biodiesel
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Methanol is an additive used to improve burn performance. Adding it beyond optimum can cause pre-ignition, which will kill performance of the engine, and possibly damage the engine. Under-injecting methanol isn’t so harmful, but the improvement in fuel burn will be limited.
methanol is part of the catalyst (along with a caustic) to convert vegetable oil to biodiesel. IT IS NOT added to biodiesel to make it burn better of anything like that.
Look up transesterification process.
There is no need to add methanol in your biodiesel it will make your fuel to be more expensive. Adding methanol will improve the fuel ignition and might damage the engine due higher flash point and higher engine temperaure. Just use the biodiesel as it is.
Methanol is used to disperse the NaOH so that the NaOH does not turn all of an oil molecule into soap (glycerin) but just a section in the middle leaving two esters of shorter chain length.
In properly prepared bio-diesel, the methanol is removed in the washing process as like all alcohols, methanol has an affinity for water. In commercial bio-diesel production, it is recovered for reuse. If there are any methanol left in the fuel, it is corrosive to the seals, fuel hoses and fittings and will dissolve any rubber in the system, otherwise it’s a source of oxygen and helps the combustion be more complete.
The idea is to use as little methanol as possible while still minimizing the production of glycerin, hence the calculations that are required and the monitoring of ph level for completeness of reaction and of specific gravity to determine the average chain length of the resulting bio-diesel. Waste vegetable oil will require more methanol than unused vegetable oil as the chain lengths of waste vegetable oil are more varied. Think of the NaOH as the knives to chop up the oil to the right lengths and of methanol as the spacer between the knives. You should err on the side of having too much during the reaction so that the resulting bio-diesel is more homogenous in chain lengths but remember that you have to try and remove as much as possible during the wash process and unless you can distill the methanol from the waste water for reuse, it’ll cost you more.