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August » 2010 » Biodiesel is Good

Archive for August, 2010

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Don’t Be a Primitive Pete

August 26th, 2010

Galen Bowen – Senior Mechanical Engineer

I remember back in high school shop class we were shown a film on featuring a very intrepid, creative, and foolish animated fellow named Primitive Pete.  He always figured out wrong ways to use tools, ignored safe practices, and generally created an entertaining and deadly environment in his immediate vicinity.

There’s a fine line between foolishly using something in a wrong and dangerous manner (the Primitive Pete method) and ingeniously using something for a new, outside-the-box purpose (Brilliant Bob?).  Making biodiesel is one endeavor which provides many an opportunity to wind up on either side of this tremendously important fine line.

Of course, the reason that we make BioPro processors is to provide a third option.  Using a well-constructed, safely designed processor allows people who don’t have the time, interest, or inclination of a Brilliant Bob to still make biodiesel without being a Primitive Pete.   To those people, I offer a heartfelt thanks, as they’re the ones that allow our company to exist.

For those those Brilliant Bobs out there, though, who want to make their own system, I want to take a couple paragraphs to discuss the pitfalls of one of the most potentially hazardous parts of the system, where being a Primitive Pete could result in you becoming a Deceased Dan.

I’m talking about heating.  You’ve gotta have it for making biodiesel.  I’ll leave all the chemical reasons for this to my brother in the Chemistry blog, but suffice to say, you need to heat up your stuff.

In most home-built systems, the target temperature in the reactor vessel is around 130-140F (as hot as possible while having a margin of safety below the point at which methanol’s vapor pressure exceeds that of the atmosphere.)  Since many homebuilt systems make use of a water heater as a reactor vessel (while certainly not ideal, it’s a pretty darn good idea, considering that you’ve got a nice sealed steel vessel with insulation already in place), the next logical ‘brilliant’ idea is to make use of a water heater element to heat your mixture.  After all, the water heater is built to use one, they put out lots of heat, they are cheap and readily available.  Sadly, this idea falls on the Primitive Pete side of the line, and has some real potential to make you a Deceased Dan.

The primary problem is the heat density of the element.  This is a measure of how much heat is being put out divided by the amount of surface area.  Think of a seat warmer in a luxury car vs. a soldering iron.  They might each put out a similar amount of heat, but which would you rather sit on?  The soldering iron has a much higher heat density; because of its small surface area it has to achieve a much higher temperature in order put out a given amount of heat.

The maximum heat density that can be used for heating a fluid is a function of a number of factors including the following:

Thermal conductivity of the fluid. Can it take away heat from the heater element as fast as the heater can put it out?  If not, the heater element will keep getting hotter and hotter.

Movement of the fluid. Is the fluid moving over the element?  This will increase convection, the movement of heat away from the element as cool fluid moves in to replace the hot fluid right next to the element.

Combustibility of the fluid. Can the fluid burn?  (Or can particles in the fluid burn?).  If yes, and the element gets hot enough, then a layer of charred fluid or particles will begin to build up on the element.  This has a snowball effect, as it becomes increasingly difficult for the fluid to cool off the element through this growing layer of charred gunk.  The element gets hotter and hotter, which not only will cause it to burn out, but more importantly creates a genuinely dangerous situation.

Flammability/volatility of the fluid. If the element is ever not submerged, will it get hot enough to ignite vapors from the fluid? (resulting in fire or explosion)

With these above factors considered the maximum heat density that can typically be used for heating in biodiesel reactions is around 23-30 Watts/sq inch. By comparison, water heater elements are typically in the range of 75-150 Watts/sq inch. Water heater elements can deliver such dense heat because water has high thermal conductivity, and is non volatile, non flammable, and non combustible.  When making biodiesel, on the other hand, you’ve got oil, which has low thermal conductivity and is combustible, and you usually have some tiny combustible particles if you’re using recycled restaurant oil.  Right there you’ve got potential for burned out elements and possible fire hazard.  Add methanol to the mix, which is flammable and quite volatile, you’ve got a recipe for disaster.  (Not to mention the fact that these elements usually come with a natural rubber gasket that will not stand up to biodiesel and will begin to leak in time.)

Only watching your house burn down somehow isn’t as funny as watching Primitive Pete, blackened by an explosion, with chirping birds circling his head.

If you must use an immersion heater, spring for one with an appropriate watt density.  They’re a couple orders of magnitude more expensive than a water heater element that you get from the hardware store, but they’re also a couple orders of magnitude safer.  Cough up the extra dough to get one with Incoloy or stainless elements so that it doesn’t corrode and short out in your tank.

Better yet, use a blanket heater.  These have an even lower watt density (typically they are available in 5-10 watts/sq inch).  They adhere to the outside of your vessel, and conduct heat through the vessel wall to heat your fluid.  Of course, you need a vessel with a conductive wall, such as a metal drum or metal tank to use these.  It’s a bit complicated if you’re using a water heater tank, since these have insulation you have to clear away on the outside, and some have a liner on the inside which is not very conductive.  The picture below shows the blanket heaters on the bottom of a BioPro 190.

A blanket heater is intrinsically safer, not only because of the lower watt density, but also because you’re not making any direct contact between your heater and your flammable fluids.   And if you do happen to overheat your blanket heaters, (say, by running them with an empty tank), they won’t get glowing hot.  They burn out.  While burnt out heaters might not make you a Happy Hank, it beats being a Primitive Pete.

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Titrating Accurately

August 18th, 2010

Daniel Bowen, Senior Chemical Engineer

 

 

Let’s discuss titrations.  In nearly any biodiesel tutorial, one of the first things that people learn is “how to titrate oil”.  Typically, these tutorials would have you:


  1. Carefully make a 1 gram per liter solution of distilled water and either potassium or sodium hydroxide. (for my examples here we will use sodium hydroxide)  This will henceforth be called the caustic solution.
  2. Dissolve a 1 ml sample of oil into about 10 ml of isopropyl alcohol.
  3. Add some ph indicator.
  4. Slowly add the caustic solution until the ph indicator shows a basic solution.
  5. The number ml of the caustic solution used shows the number of grams of NaOH needed to neutralize the free fatty acids present in the oil.  This quantity is then added to base amount of NaOH that is always use in processing to give you

a total quantity of base needed per liter of oil to be processed.

This is all well and good, except that all of the following steps depend on the accuracy of step 1.  If anything throws off the accuracy of your carefully prepared 1 gram per liter solution of NaOH, then the whole thing is bunk. Not only that, but there is no way to even tell if you did step one correctly.  And even if you did do it right, the fact that a caustic solution will degrade rather quickly with time means that the next time you use this carefully prepared solution, it will be of a slightly different strength than the time before.  (Incidentally, the two primary sources of sodium hydroxide degradation involves its reacting with glass to form sodium silicate, and its reacting with carbon dioxide to form sodium carbonate. Therefore an airtight dark plastic container is typically ideal for NaOH solution storage.)

The following is a simple way to test the strength of your caustic solution prepared in step one.  This will allow you to have confidence in the accuracy of your titration every time.  This is true even if your caustic solution is mis-measured or degraded.

  1. Purchase a stock solution of .0100N HCl (hydrochloric acid) or KHP (potassium hydrogen phthalate).  These stock solutions are very carefully measured to be exactly what is claimed on the bottle.  The .0100N represents .01 moles of solute (HCl or KHP) per liter of solution.  These types of stock solutions can be found from most chemical suppliers.
  2. Mix 10 ml of this .0100 N solution with a drop of ph indicator (phenol red or phenolphthalein) and 10 ml of distilled water.
  3. Titrate this solution with your caustic solution carefully counting the exact number of ml needed to get a color change.
  4. Divide 4 by this number to find the real strength of your caustic solution in grams of NaOH per liter of water.
  5. Don’t try to change the concentration of your caustic solution to try to make it come out at exactly 1. Just titrate your oil as you normally would with this solution.  Take the result of your titration and multiply it by the real strength number that you obtained in step 4.

Let’s look at an example:

  1. I grab an old caustic solution off the shelf and I want to use it to titrate some oil.  So first of all, I get a clean beaker and add 10 ml of distilled water and 10 ml of my .0100 N KHP solution and a drop of phenolphthalein.
  2. Then I slowly add my caustic solution while stirring until the mixture turns pink.  I find that this takes 5.3 ml
  3. I divide 4 by 5.3 to get 0.755.  This means that my basic solution really only has an equivalent of 0.755 grams of NaOH per liter.
  4. Now, if it takes 6.3 ml of this solution to neutralize the FFA in 1 ml of oil, I know that the real neutralization number is only 6.3X0.755= 4.76

Not too bad.

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Fuel Lines

August 9th, 2010

Senior Mechanical Engineer

I have a Toyota Landcruiser that is a never-ending project.  I bought it with a blown motor, and put in a Chevy 6.2l diesel, as this seemed the easiest and cheapest diesel swap.  (Got the motor out of a van I bought for $600.)  From that point, I went to a Mercedes OM606 (not enough power with the non-turbo’d version), then to a Mercedes OM617 (I think this is my favorite diesel engine of all time, but still 2998 cu cm is a bit small for hauling around a 5,000 lb FJ-60).  My current motor is a Cummins/Onan L634T.  I’ve pretty well burnt myself out on motor swaps, so I intend to stick with this one for a while.

I never really gave much thought to biodiesel resistant fuel-hoses back when I was changing my engines more regularly than I was changing my oil.  By the time my fuel hoses began to degrade, I’d be tearing them out anyway to plumb the fuel to a different motor.  However, since I’ve actually stuck with my current motor for a couple of consecutive years now, I’ve been forced to confront this gooey issue:

Gooey Fuel Line

This picture is actually from my brother’s car (he obviously is not a great deal more fastidious in this regard than I am.)  I never got a photo of the fuel lines in my truck, but they looked about the same.

I figured I’d have to order some kind of special Viton tubing from McMaster Carr at $8/foot if I would ever by rid of the above pictured phenomenon.  However, while doing some research on an excellent VW TDI forum (www.tdiclub.com), about an issue with my wife’s Passat, I noticed a thread about biodiesel resistant fuel hoses.  Turns out it’s common knowledge over there that there is a standard fuel hose available which is biodiesel resistant.  It’s SAE 30R9, and it has a flouroelastomer liner.  It’s more expensive than the regular stuff you normally buy (SAE 30R7) but it’s a lot less than buying viton tubing, it’s a lot tougher since it’s actually a reinforced hose, not just a tube, and best of all, you can get it from a typical auto parts store.   They guys behind the counter usually know it has ‘fuel injection hose,’ or ‘high pressure fuel hose’ since it’s got a higher pressure rating than the SAE 30R7.  For 5/16”, it’s usually $3-4/foot.

SAE 30R9

For the first time in a long time, my truck is not a ticking time bomb waiting to spew biodiesel all over my engine compartment from a hose which has degraded into rubber putty.

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I figured it’d be appropriate to start off with some kind of an introduction.

August 3rd, 2010

Senior Mechanical Engineer

I figured it’d be appropriate to start off with some kind of an introduction. I’ve been heavily involved with biodiesel since 2004, when my brother, my cousin and I joined up to form AGR Energy. Upon forming that company, my brother and I designed and built the first prototype of what eventually evolved into the BioPro™ 190 (now manufactured by Springboard Biodiesel). If you are familiar with the BioPro™ 190 today, you may find it entertaining to compare what it is now with what it was at first:

biopro 190 original
THEN NOW

That first BioPro™ machine may have been funny looking and awkward to use, but it also didn’t work very well. I now wish we’d kept it for posterity, but we eventually gave it to a nomadic scrap metal collector who came by our shop and gave us the equivalent of lunch money in exchange for our cherished relic.
Why is this story worth relating? Well, I think at the time that first prototype was built, I was a reasonably competent engineer and designer. Yet there were so many variables and nuances of biodiesel production to which I was completely oblivious. Making biodiesel equipment may be relatively simple when compared with, say, making liquid crystal displays (http://www.appliedmaterials.com/htmafpd/animated.html), but the whole field of biodiesel production is not nearly as well developed and established as other industrial fields, and direct experience is crucial. So hopefully amid the gripes, rants, opinions, and not-really-related-to-biodiesel posts that will probably find their way onto this blog in the future, there will also be a few helpful tips and experiences that might be new to you, or are at least of interest, and which may, hopfully, make for interesting reading.