|
View my Biznik Profile!
 Kuma Biodiesel Stoves
|
Titrate the oil, using the method described below- similar to that described at biodieselcommunity.org The description below is written using KOH (potassium hydroxide) which has several advantages (see processing section), but NaOH (lye) could be used.
 You'll first need to make up a 0.1% solution of potassium hydroxide, (KOH) in distilled water (1 g KOH in 1 L distilled water). I have found that this solution gets cloudy after a week or so, but that a 1% solution does not. So I keep a 1% solution as a stock, and just dilute some 1:10 to make a new 0.1% solution when needed. If using sodium hydroxide (NaOH) make your titration solution using 0.1% NaOH. - Put 10 ml of 99% isopropyl alcohol (available at Safeway, and as Iso-Heet at auto parts stores) in a small white or clear cup. Take exactly 1 ml of your waste vegetable oil and mix into the alcohol in the cup. You can get 1 ml plastic or glass pipettes for this, or ask a pharmacist for a 1 ml diabetic syringe. If using a 10 ml syringe, you can draw the oil up to say the 5 ml line, then eject until the same part of the plunger is at the 4 ml line.
- Add 3 drops phenolphthalein (0.5% in isopropyl alcohol) and stir. (I use a plastic chopstick as a stirrer). This is an acid-base indicator that's colorless in acid and red in base. Note that phenolphthalein is light-sensitive, so store it in the dark, and don't use for more than a year. You can also use a solution of the spice tumeric, which changes color at about the same pH. To make, simply mix some tumeric with some isopropyl alcohol, let it settle, and use the liquid on top. Some also use phenol red, which is more readily available at pool supply stores, but is not as accurate.
- Carefully begin to add the 0.1% KOH solution a few drops at a time mixing as you add. Keep track of how much you're adding. Keep adding the KOH solution and mixing until the solution starts to turn a little pink. Now be sure to add slowly, a couple drops at a time, until the solution holds its pink color for about 20 seconds. That should be a pH of about 8.5 (check with your pH paper). Write down how much lye solution you've added. It should be anywhere from 0.4 ml to 5 ml, depending on how used the oil was. You may want to start by doing a "blank" titration of the alcohol without any oil added to make sure your alcohol isn't acidic. It should not take more than a few drops of lye solution to turn pink.
 The amount of KOH solution you added translates into how many grams per liter of KOH you'll need to add to your methanol for that batch of oil. You need to add 11g / liter to whatever number you got, since that's how much KOH is needed for the reaction of virgin oil. So if your titration told you to add 2 g of KOH, then you'll actually need to add 13 g KOH per liter for this batch of oil (2 g + 11 g = 13 g). Then, multiply 13 g times however much oil you're going to use. Note: If you use NaOH (lye), then the base amount is 5 g per liter instead of 11.- The methanol: The standard is to use at least 20% methanol, so for a 20 gallon batch of oil, that'd be 4 gallons of methanol. Actually, 22% methanol is now recommended to drive the reaction to completion and make the best quality fuel.
- Do some 1 liter test batches in a blender or in a pop bottle. Let them sit overnight, and in the morning you should see good separation of the biodiesel and glycerin. You can also perform the 3/27 test on that small batch to see how good of a reaction you did.
- Once you've decided on the optimal amounts of KOH and methanol to use, just scale up the amounts for however many liters you plan to process. My last batch: titration told me to use 13 g lye per liter, so I used 13 g x 188 L = 2444 g KOH. Methanol at 22% for 188 L would be 41.4 L or 11 gallons.
|
