A repost - still trying to avoid the "blank" subject header....
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
