Many of us have who follow biofuel have been convinced that biobutanol (or mixed heavy alcohols made from cellulose) is the future of this alternative fuel; and that this will supplant ethanol rather quickly, once the technology becomes widespread.
Jeff Baker posted comments to a blog a few months ago - which if true (and recent new information adds to its credibility) makes any planned switchover from ethanol to butanol less obvious and less sensible than it was seeming to be... especially since we find recently the full extent of what the Chinese are now doing with so-called "hydrous ethanol" and how successful it has been reported to be ... [side note] It’s official: China became the World's largest car market in January: Largely due to the plunge in American car sales, China overtook the U.S. in monthly vehicle sales in January 2009 for the first time - this to be the world’s No. 1 auto market for the month.... Back to Baker's comments, paraphrased and updated with my annotations, which indicates that China may continue to outpace us - due to the technology of bioethanol: There is a special relationship between ethanol and water, and neither butanol nor gasoline have this feature of infinite solubility .... however, capitalizing on this feature requires more extensive modifications to the IC engine of the vehicle than we may have expected. There are always tradeoffs. Butanol will mix with 7 to 9% water. Gasoline will mix with pre-bonded 4% hydrous ethanol. This is too little to get the benefit of full steam expansion. NOTE: It is the expansion of a liquid to a gas which propels automobiles, and technically it is NOT the heat of combustion (except as it is used for expansion). This is a critical fact to remember. Any heat not being used to expand a liquid to a gas is watsed. With hydrous ethnaol the waste heat can be drastically curtailed. The risk to avoid is flame quenching - and it is H2 that comes to the rescue there. Liquid ethanol will combust with up to 50% water mixed in, maybe more if a constant engine speed is permitted. Above 50% water, hydrous ethanol needs to be vaporized (not a big problem) and possibly reformed (bigger problem) ... however, more water can be more efficient as a fuel, up to a point and and in terms of Carnot efficiency. When the fuel contains LOTS of water, there can be a big jump in Carnot and it can actually exceed the theoretical limit. But mixing two good solvents is also more corrosive, and demands a re-engineered engine. Ethanol’s compatibility with water is the very thing that makes it superior (or should we say "can make it superior"). This is what Phil Ratte (ME U of Minn) says about ethanol in solution with water: "From 1981 to 1989, I worked with Herb Hansen, who had been an engineer on a WW II submarine, and a former captain of a nuclear submarine. We developed two prototype cars, a Ford Pinto Station Wagon and a Mitsubishi Sedan, that ran as well on 65 proof ethanol (2/3 water and 1/3 ethanol) as they did on unleaded regular gas." IOE the mileage obtained was similar, but of course, modifications must be made first. How is that possible after you have diluted the low BTUs of ethanol even further, down to 26,000 BTUs? It’s because ethanol is extremely volatile and has and has a very high vaporization rate and flame speed AND can be reformed easily, freeing some small amount of H2. This is facilitates by splitting water vapor and ethanol into hydrogen and CO and oxygen, either inside the combustion chamber or in the intake. This need to do in situ reforming may make also make ethanol the fuel of choice for HV electron augmentation (Brian Ahern's concept). Dongfeng, a major Chinese auto maker is introducing a car that runs on 65% ethanol and 35% water. This is a modified IC engine equipped with a fuel processing device. Possibly it involves a vaporizer combined with a water-splitting device, possibly using RF in a modified Kanzius approach. Dongfeng claims that some hydrogen is formed, enough to maintain the high flame speed and avoid quenching when so much water is in there ... here is the original story on another blog: http://www.autobloggreen.com/2008/01/03/dongfeng-investigating-hydrous-ethanol/ The Chinese are therefore using ethanol in a more efficient way than we are- Doubly efficient in fact ! When you leave 35% of the water in solution with ethanol at the refinery, you reduce the distillation energy at the same time you extend the fuel .... but additionally the highest tech method of alcohol dehydration, which is membrane based, has the potential to ELIMINATE DISTILLATION altogether, but the holdup with that technique in the past is that it does allow some water to pass. Curiously membrane enrichment is usually most efficient with this very same 65/35 ratio of ethanol to water ! Eliminating distillation is HUGE for ethanol ! A double whammy. Are you listening GM? Again the Chinese report that some hydrogen can be separated to maintain the burn. That would be hydrogen on demand from hydrous ethanol. Gasoline and butanol cannot do what ethanol can do with water due to solubility issues. Bottom line: This is (could be) that the highest use of ethanol- i.e. is to keep it diluted with most of the original water. This could be the future of all liquid biofuels - if and when it becomes cellulosic-based and with full membrane (non-distillation) enrichment. Jones
