[Stoves] The PROTOS Plant Oil Cooker

[Keith Addison]

>When peter and I talked about oil-water emulsion, we were thinking of stoves
>and not an internal combustion engine.

I know, it's basically the same problem though. I said it wasn't a 
how-to, but it's an approach.

>Has anybody tried to make a wick stove using vegetable oil? We tried the
>kerosene wick stove with vegetable oil, but discovered that vegetable oil
>would not rise up the wicks.

Work has been done on this in India, but I don't have the reference, 
sorry. It needs a special wick, wide (about half an inch), loosely 
woven and fitting loosely in the burner, with less distance to the 
reservoir beneath. Better if the reservoir is as high or higher than 
the wick, like a doughnut, with the wick in the middle. Not so easy 
to do. We made some rough prototypes that worked quite well, but 
rather than new designs what we really wanted was to modify existing 
stoves (though designs that local metalworkers could fabricate would 
be useful). But there doesn't seem to be an easy way of converting 
kerosene wick stoves to use vegetable oil, or not that we've found 
yet. You might have some success with blending vegetable oil with 
kerosene in an ordinary wick stove.

Biodiesel also doesn't like climbing a wick, though it's better at it 
than vegetable oil.

Kerosene pressure stoves (roarers) are an easier problem than wick 
stoves. Biodiesel works very well in roarers at 100% without any 
modification. We use a roarer burning pure biodiesel to pre-heat the 
used cooking oil for the biodiesel process (BUT no open flames once 
the methanol enters the picture, we use an electric immersion heater 
to maintain the temperature during processing). We're planning a 
series of tests with roarers burning mixes of biodiesel, vegetable 
oil and maybe kerosene too, but we haven't done it yet, this summer 
hopefully. Some proportion of vegetable oil should be possible.

I seem to recall mention on the list of a project in Swaziland (?) 
that had a small cooking stove that could burn vegetable oil, IIRC. 
I'll try a search, but not now, have to rush.

All best

Keith


>Yours
>A.D.Karve
>
>----- Original Message -----
>From: Keith Addison <keith at journeytoforever.org>
>To: Discussion of biomass cooking stoves <stoves at listserv.repp.org>
>Sent: Tuesday, May 01, 2007 7:42 PM
>Subject: Re: [Stoves] The PROTOS Plant Oil Cooker
>
>
> > Hello A.D., Peter
> >
> > >Dear Peter,
> > >In Indian cookery, deep-frying in boiling vegetable oil is quite common.
>The
> > >temperature of boiling oil is 250 C. I have never observed the oil
>getting
> > >pyrolysed into carbon and volatile matter at that temperature, even when
>the
> > >same oil is used again and again, as is often done here.  However, your
> > >suggestion of using a water-oil emulsion is interesting and worth trying.
> > >Have you any suggestions as to how one forms a stable emulsion of water
>and
> > >oil?
> >
> > If you talk about water in diesel fuel all the diesel buffs yell
> > "Aarghh!" But addition of water to the diesel process decreases
> > combustion temperatures and lowers NOx emissions, and a lot of work
> > is being done with water-fuel emulsions, with some big names
> > involved..
> >
> > What works with emulsifying petroleum diesel fuel might also work
> > with vegetable oil, or at least indicate a direction
> >
> > Try a search for "Fuel Emulsions" here, to give you an idea (though
> > technical information requires a subscription):
> > http://www.dieselnet.com/search
> > Site Search
> >
> > There's also this:
> > http://www.epa.gov/otaq/models/analysis/emulsion/emulbibl.pdf
> > Bibliography of Water-Fuel Emulsions Studies, October 11, 2001, U.S.
> > Environmental Protection Agency, Office of Transportation and Air
> > Quality. Following is a list of studies that are being considered for
> > inclusion in work being done by EPA to assess the effects of
> > water-fuel emulsions on emissions of oxides of nitrogen (NOx),
> > hydrocarbons (HC), and particulate matter (PM).
> >
> > This is from dieselnet.com:
> >
> > "In emulsion systems, water is mixed with diesel fuel and the mixture
> > is supplied through one injection nozzle. Depending on the method of
> > mixing, either phase can be dispersed in the other. As mentioned
> > before, in order to minimize water contact with internal engine
> > surfaces, diesel fuel should form the continuous phase in which water
> > should be dispersed in the form of small droplets. Water-in-fuel
> > emulsions will also minimize the potential corrosion problems in the
> > fuel system. Due to the differences in density and other physical
> > properties, water-fuel emulsions are not stable. ... Unstabilized
> > emulsions separate quickly and must be prepared on-line in the engine
> > fuel injection system immediately before the injection. This type of
> > system involves two tanks, one for fuel, another for water, followed
> > by two pumps and a mixing device. In one laboratory study, mixing was
> > carried out as a two stage process [De Vita 1989]. First, the liquids
> > were mixed in a premixer, where the internal phase (water) was
> > injected through nozzles into the continuous phase (fuel) swirling
> > through a cylindrical chamber. The mixture was then fed, through a
> > gear pump, to an emulsifier. The emulsifier was a static mixing
> > device featuring a system of nozzles and channels, where the blend
> > drops dimensions were decreased due to jet diffraction, impact,
> > friction, and high pressure rates. The homogeneous emulsion was fed
> > to the engine fuel injector. ... Stabilized emulsions involve mixing
> > of fuel and water with the addition of small quantities (typically
> > 1-3% of the fuel) of chemicals which facilitate the formation of
> > emulsion (emulsifiers) and prevent or delay separation once the
> > emulsion is prepared (stabilizers). ... Emulsions must remain stable
> > for a sufficient period of time to prevent separation in the fuel
> > tank. In practical terms the required stability period must be at
> > least several days, preferably several weeks."
> >
> > Companies like Lubrizol, Caterpillar, Aquazole, Clean Fuels
> > Technology, A-55 et al probably have more stable solutions than that.
> >
> > Biodiesel brewers using used cooking oil as a feedstock find that the
> > longer the oil has been cooked, and the higher the cooking
> > temperatures, the higher the level of Free Fatty Acids will be, and,
> > almost certainly, the higher the water content of the oil, which is
> > of concern because water interferes with the biodiesel process and
> > should be removed first.
> >
> > This is what one Biofuel mailing list member said about water removal:
> >
> > >Water in vegetable oil can exist as free water, which will
> > >eventually settle to the bottom of a vessel; as suspended droplets,
> > >which may settle if the oil is heated, or the droplets are
> > >coalesced; and as water in solution with other impurities in the
> > >oil. Free water is the easiest to remove. The droplets are removed
> > >most efficiently by coalescing and draining. Suspended droplets that
> > >cannot be coalesced and water in solution are more problematic.
> > >
> > >Boiling off the water is more difficult than it appears on the
> > >surface. Colligative properties of solutions (and some mixtures) can
> > >make removal of the last traces of water almost impossible. Water
> > >mixed with oil will not boil at the same temperature and pressure as
> > >pure water. As water is removed, more heat or lower pressure will be
> > >required to remove more water. If the oil contains salts or
> > >semi-soluble fatty acids, distillation is even more difficult.
> > >
> > >As the percentage of water in the solution decreases (its molar
> > >fraction) its vapor pressure will continue to drop. Lowering
> > >pressure in the system alone may be insufficient to sustain
> > >vaporization when the solution becomes concentrated (the molar
> > >fraction of the solute greatly exceeds that of the solvent). Results
> > >will vary depending upon the nature of the water-soluble impurities
> > >in the oil. Few solutions are ideal, in terms of Raoult's law, and
> > >in used vegetable oil, there is no way to know what solutes are in
> > >the oil.
> >
> > Sorry, that's not exactly a how-to, is it? Hope it helps though.
> >
> > Best wishes
> >
> > Keith Addison
> > Journey to Forever
> > KYOTO Pref., Japan
> > http://journeytoforever.org/
> >
> >
> >
> >
> > >Yours
> > >A.D.Karve
> > >
> > >----- Original Message -----
> > >From: Peter Verhaart <pverhaart at iprimus.com.au>
> > >To: Discussion of biomass cooking stoves <stoves at listserv.repp.org>
> > >Sent: Monday, April 30, 2007 4:08 PM
> > >Subject: Re: [Stoves] The PROTOS Plant Oil Cooker
> > >
> > >
> > > > I still believe all vegetable oils will decompose thermally, into
>carbon
> > > > and vapours, making them unsuitable for pressurised burners such as
> > > > Primus. The temperature would be in excess of 200 C.
> > > > It would be nice if these oils could be emulsified with a tiny amount
>of
> > > > water. The steam resulting from heating the emulsion in the burner
>could
> > > > form a spray of small droplets that burn completely. In this way the
> > > > oils would not be exposed to temperatures causing decomposition inside
> > > > the burner.
> > > >
> > > > Peter Verhaart