Transesterfication Process Page
Biodiesel is made through a chemical process called transesterfication whereby the glycerin is separated from the fat or vegetable oil. This process involves an alcohol (usually methanol) and a catalyst (sodium or potassium hydroxide) which break down the fatty acids. Your oil is made up of fatty acids connected to a glycerin molecule. Transesterfication forms biodiesel and glycerin because the alcohol replaces the glycerin molecule in the oil. The technical definition of biodiesel is fatty acid methyl ester, transforming one type of ester into another Transesterfication is quite simple. One need not be a chemist to make biodiesel, though it certainly helps. Many such people have outlined reliable and proven biodiesel production recipes. In this process the vegetable oil or animal fat reacts with alcohol, like methanol, and a catalyst, like lye (which helps the reaction take place). By volume, these reactants are about 75% vegetable oil or animal fat, 22% alcohol and a little lye. Once together, they are mixed thoroughly for about an hour and then left to settle. The heavy glycerin settles to the bottom and biodiesel sits on top. Oftentimes producers water wash the biodiesel to ensure that it's clean. The optimal conditions for transesterfication and the forming of fatty acid methyl ester is chemical mix, time and temperature. You get the chemical mix (the ratio of Sodium or Potassium Hydroxide and Methanol Alcohol) requirement using a test method known as titration. Titration functions as a ph test and a way to find out how much NaOH/KOH (the catalysts) and Methanol Mix (refered to as Methoxide) you add to your waste vegetable oil to neutralize the free fatty acids. The Free Fatty Acid content chages the pH towards the acid range, the Methoxide compound needs to bring the chemical pH back towards the base or neutral range. If you use virgin oil which is unused oil then there is a base amount of catalyst you use. This base amount is 3.5grams/liter for NaOh (and 7.5grams/liter for KOH). If using WVO your titration results are added to this base amount. This will give you the required chemistry in the processor to encourage the formation of the methyl ester known as BioDiesel. In the processor conversion requirements you set the chemical conditions based upon the titration numbers (this gives you the proper chemistry for methyl ester formation). You can speed the process up by increasing the processor temperature. Caution: Remember that Methanol boils off at 168 degrees farenheight. This means that you cannot increase the processor temperature any higher than to within 18 degrees of this critical temperature point. But you can if you presurize the processor.Once again: CAUTION: Pressurizing the processor is extremely dangerous and can be catastrophic. This is not a good practice and should be avoided. Since the optimum temperature range for transesterfication is from 100 degrees to 140 degrees farenheight, this is the temperature range that you must maintain your processor at. The best performance is achieved at about 135 to 140 degrees farenheight. Since mixing your NaOh/KOH and Methanol generates residual heat, then adding the methoxide brew to your processor will generate some heat of it's own - you will find that transesterfication will progress just fine. In practice is is best to pre-heat the WVO prior to introduction of the methoxide mixture. In most cases, this is done pprior to filling the processor by using an in-line heater/heat exchanger. In other cases, the WVO is heated right in the processor tank. Many times hot water/immersion heater elements are used. The elements are switched off when the methoxide mixture is introduced into the processor.Using an electric immersion heater, or a heater that utilizes an open flame is extremely dangerous in a BioDiesel Processor. Methyl Esters are extremely flammable, Methanol vapors are more dangerous still. An electric element is subject to failure in any normal water heater, and the risk of explosion is extreme because an element failure will result in an electrical arc. this will cause a gas bubble, which will most likely contain a methaol vapor - which will result in an explosion. Keep, all heaters out of the processor tank, and if you must heat the processor contents, do it outside of the processor by inserting a thermal heat exchanger in-line (between the recirculation pump) and the processor. This way the oil mixture will be heated prior to reinsertion into the processor. Processing times are as varied as the different design schemes being used. Suffice it to say that a transesterfication processor takes about 12 to 20 hours for total conversion at about 80 degrees farenheight. If you increase the processing temperatures to 140 degrees farenheight, this processing time requirement for 99.9% conversion will shorten to around 45 to 65 minutes ( a radical reduction in time for processing). If you have any comments or questions we would be glad to address them. Following is our eMail address, please feel free to provide your inputs. Our eMail address is:: AZBioFuels@phoenixcomputerlabs.com Thanks,
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