For ages, it has been possible to easily separate and enrich
miscible liquids into "rough" components - or even to enrich
atomic elements isotopically using only spin - simple centrifugal
methods. But until recently the basic spin-process was seldom
considered as a substitute for the more energy-intensive
enrichment processes like distillation. That can change with three
types of spin-hybrids.
1) spin plus filtration (or osmosis)
2) spin plus magnetization (or e-field polarization)
3) spin plus a "binder"
In general, the energy required to spin-separate a liquid into
components (like whole milk) ranges from less than one percent to
ten percent of what would be required to distill. Even so-called
ultra-centrifugation is usually only a fraction.
Some recent success in finding a combinatory enrichment
technique - which is efficient in the enrichment of peroxide from
dilute mixtures (which will be reported on later) got me to
thinking about the possibility of using something similar to this
for biofuels - even though the density gradient is much less
accommodating. The multiple goals of this would be to avoid
distillation, expedite continuous (non-batch) fermentation, and
thereby to enrich directly from a fermenting mash in one step -
returning the dilatants immediately to a continuous - not a
batch - process.
The first use would be "on the farm." A farmer with as little as
20 acres should be able to devote a tenth of that to making and
refining all of the tractor fuel, home heating fuel and
transportation fuel needed, by growing and cutting grass or cane.
There have been objections voiced that this would somehow "deplete
the soil" but there are parts of the world where farm-land has
been intensively farmed by humans for 6000 years and is still
productive. Even fully depleted-soil (watered sand) will grow
grass or cane. It is a hollow argument.
Given that single-celled yeasts and engineered bacteria are now
available to ferment cellulose biowaste (hay) quickly; then all
that is needed for energy self-sufficiency is to convert the same
into diesel-like methyl and ethyl esters, with mixed alcohols and
up to 15% water - but without using lots of extra energy to boil
it. Perhaps it is time to look at schemes to enrich the *mixed
biofuel content* of a "mash" to a level which is burnable in an
unmodified ICE [using a compact "turnkey" machine] and which does
not require distillation. There are a number of advanced proposals
out there, but the most exciting is one which can enrich in both
biodiesel esters and ethanol at the same time. Biodiesel and
ethanol are far from mutually exclusive and can even be "brewed"
in the same mash synergistically and then enriched together and
burned in an unmodified diesel engine (in theory).
The tornado-like "vortex" itself, which gives this forum a certain
unique "personality" (screwy <g>?) is one basic centrifugation
method, and possessing a possible advantage over 2-D spin-only.
That advantage being a spin-elutriation method using a indigenous
binder.
"Elutriation" is the separation of (finer or lighter) particles or
colloids from coarser or heavier particles, or from a liquid,
often by means of an upward and outward stream of fluid so that
the lighter particles are carried upward and then "slagged". It
can be combined with centrifugation, especially when a colloidal
"binder" is used. The binder, if it is colloidal, can remain in
the mixed fuel and be burned. A binder is a reagent which will
favor attachment to one molecule over another by as much as
million-fold, and many of them are hydrophobic - and thus can
dramatically aid the de-watering effort - in a hybrid process.
That binder can, in theory be made in situ from the very yeast
which accomplishes the fermentation, by ultrasonic or other
pulverization methods.
The first large-scale use of spin-centrifugation was non-military,
and a bit less mundane than uranium enrichment. Historically, the
first centrifuge seems to have been built late in the last century
by de Laval, a Swedish engineer whose design is still used chiefly
for cream-separation from whole milk (cream being lighter). The
"gold-panning" technique is part of an older spin-elutriation
lineage, along with "winnowing" but wasn't industrialized until
later. That one also has elements of elutriation - as does
milk-cream and the mixed biofuel scheme envisioned here.
For getting the active heavy metal isotopes for the bomb which
ended WWII, it was necessary to enrich uranium in its
fissile-isotope, which is found in nature in only seven parts per
thousand. The bulk of that separation was done in a gas centrifuge
process in which a U-fluoride gas is rotated at high speed in a
porous tube, so that the slightly more massive molecules -
uranium-238 concentrate near the outer edge and are expelled
preferentially while the lighter molecules of U235 are
concentrated near the axis - but slowly, very slowly.
Several hundred stages of centrifugation are needed to effect the
required degree of enrichment, since we are dealing with a
mass/density (specific gravity) difference of only three parts per
292 (counting the fluorine) - or about 1 percent. The number of
stages in any enrichment cascade is directly related to the
mass/density variability and other factors. Cream is actually not
very different in density from whole milk, but is not completely
miscible and will separate on its own - so it is easier - and that
is a direct analogy with the hybrid biofuel process envisioned -
since the fat (or binder) is hydrophobic.
Centrifugation is based somewhat on Stoke's Law in which the
particle "sedimentation velocity" increases with increasing
diameter of the chamber, increasing difference in density between
the two phases and decreasing viscosity of the continuous phase.
There is zero "sedimentation" however, in a two part miscible
liquid like water and alcohol, but that can be changed with a
binder which "prefers" alcohol - and is also combustible in
itself. BTW - cream is about 25 parts per thousand lighter than
milk - which tiny difference is comparable to the range which is
often exploited in isotope separation and about what would be
involved in enriching a mixed biofuel - if other techniques are
employed to encourage sedimentation.
Anyway, most of this is well-known and hundreds of US chemists are
plodding away on various parts of the problem... but if anything
can be added by the comments of an outside observer - it would be
that few efforts seem to be aimed directly on the easiest "quick
and dirty" approach (in this case "quick and green"). American
chemists, like their German mentors of the previous century - have
an ingrained fear and dread of anything which is not extremely
precise. They are not adept at finding a lowest common denominator
or even the cheapest approach.
If the product is going to be burned, however, there is little
real need for precision, and it can be counter-productive for
cost. Consequently, this type of hybrid mixed-biofuel process,
involving both cheap ethanol and mixed esters - for use on the
small farm is (most-likely) something which we will see coming out
of India or Asia, maybe Eastern Europe.
Hopefully -- it will be sooner rather than later.
Jones
