Fischer–Tropsch - Page 1
Forum section: electronics / general

author: abebarker
author_rank: Contributor
timestamp: June 04, 2015, 08:10:36 am
content: I'm surprised to not see this technology not mentioned any where in the forum. It's cutting edge technology from 1925 Germany. The ability to make gasoline or diesel fuel from carbon monoxide or even carbon dioxide. I think it is at least worth knowing about. It's another item for the alternative fuels tool box.http://en.wikipedia.org/wiki/Fischer–Tropsch_processThe US military has been playing around with it since the current president is not an oil baron (Could the previous one be said to have a conflict of interest?). The Air Force has built a couple pilot plants and certified that it will work in jets. The navy wants to install plants aboard carriers to manufacture jet fuel by pulling CO2 out of the water.http://www.nrl.navy.mil/media/news-releases/2012/fueling-the-fleet-navy-looks-to-the-seas

author: matseng
author_rank: Frequent Contributor
timestamp: June 04, 2015, 08:14:13 am
content: Is that the same process that Audi is using in their much hyped "breakthroughs" with synthetic e-diesel and e-benzine?

author: abebarker
author_rank: Contributor
timestamp: June 04, 2015, 08:17:59 am
content: Yes it is. Everybody is jumping on the band wagon.

author: m100
author_rank: Regular Contributor
timestamp: June 04, 2015, 01:59:20 pm
content: I saw the title and broke out in a cold sweat thinking it was the Haber–Bosch process that I did in O level ChemistryPhysicsChemistryIt'd be handy if they could use this at a coal or gas fired power station, still quite a lot of heat disappearing up those chimneys along with the CO2

author: LukeW
author_rank: Frequent Contributor
timestamp: June 04, 2015, 02:11:14 pm
content: It's not cheap and not environmentally friendly - but useful if you can't get any access to any oil. It's not a clean alternative, it's just the same, at best, as ordinary fossil fuel combustion. Generally it has only been developed in countries like South Africa and Germany during WW2, where geopolitical considerations cut off the access to oil. Otherwise it just has limited economic attractiveness.On a large aircraft carrier I guess it makes sense, to use process heat/power from the ship's nuclear reactors to generate fuel for the aircraft fleet using atmospheric CO2, so that fuel does not need to be carried.

author: LabSpokane
author_rank: Super Contributor
timestamp: June 04, 2015, 06:31:08 pm
content: I see new F-Tprojecthalf-baked idea come across my desk once a week or so. The only commercially viable projects are used to turn coal (SASOL process) and natural gas (Shell process) into liquid gasoline as well as a bunch of other co-products. They are huge as well as hugely expensive. It takes a massive economy of scale to make F-T economically viable, as well as generation of high-value co-products for chemical processes. F-T doesn't work unless you get "all the squeal out of the pig" as one of my clients so aptly puts it.It's worth noting that the SASOL process exists primarily due to the embargo on South Africa during Apartheid.Using F-T on much of anything else is an economic loser. Everyone wants to use syngas from wood and garbage to put into a F-T reactor. My advice is to run as fast and as far away from such things as possible. To date, there is no good, commercial process to clean the syngas (H and CO and other stuff) well enough to not poison the catalyst. Don't be fooled by a bench-scale reactor. Using bottled CO and H from your local gas supplier is totally different from getting the syngas from a gasification process.As far as doing it on a small scale, forget it. The only practical scale is 50,000 bbl/day and up.The most recent plant is Shell's Pearl GTL plant in Qatar. It cost just shy of $20B to develop and was originally budgeted around $3B or so, if I recall correctly. So, even the world's foremost experts find F-T hard. The Pearl GTL plant is also the size of a small city.http://www.shell.com/global/aboutshell/major-projects-2/pearl/overview.htmlThe most recent Shell GTL (gas-to-liquids) project planned for the US Gulf coast was cancelled. Henry Hub gas is currently $2.63, which is CHEAP and the project wouldn't work. That should give you a metric for just how hard it is (and about the worries of a fracking bubble cutting the natural gas supply).The Navy's CO2 to jet fuel process is based on it being easier to process water using nuclear-generated electricity than getting an oiler ship into a combat zone or the actual economics of the fuel. It's about combat-readiness, not a favorable energy/cost analysis.

author: SeanB
author_rank: Super Contributor
timestamp: June 04, 2015, 06:56:50 pm
content: SASOL and Secunda are large cities in their own right, and they supply fuel as only a small part of the output. Largest product from them is oxygen ( hey, if you need a really honking big LOX generator you might as well make it really large and sell the excess) they pipe to the steel mills near them, electric power ( plenty of low level waste gas that they burn to make their own power to offset buying it, plus they do not have to flare it and get CO2 from the plant to use internally again), plastic feedstuffs ( I use a lot of assorted plastics made by them, they make PVC, PP, HDPE and PS amongst others) and a lot of speciality chemicals used in inks, industry and other chemical feedstuffs. Fuel is mostly alcohols and other ketones, aldehydes and aromatics they blend in the regular fuel, or sell alone. They are a large supplier of waxes as well.

author: mtdoc
author_rank: Super Contributor
timestamp: June 04, 2015, 07:02:12 pm
content: I agree with the above. It comes done to liquid fuels and long term strategic planning.Recent "flash in the pan" unconventional petroleum extraction not withstanding, the US Department of Defense has acknowledged that the petroleum era will soon come to an end. SeeHEREandHERE. The German military has issued similar reports.This is just one example of how they are preparing for the eventuality of needing to fuel jets and other military hardware without oil. Economics and environmental impacts be damned.For the rest of us, without our own nuclear power plants, well....

author: IanB
author_rank: Super Contributor
timestamp: June 04, 2015, 07:46:44 pm
content: Quote from: abebarker on June 04, 2015, 08:10:36 amBut consider the big picture. If you burn hydrocarbons you produce CO2 and H2O and get lots of useful heat energy. If you now wish to reverse that process and convert CO2 and H2O back into hydrocarbons, then you need to put all that energy back in again. You didn't so much get new fuel, rather you stored some energy you already had in a different form for later use.This process is useful if you need hydrocarbons for their particular properties (liquid, easily pumped, easily carried in vehicles like cars and planes, easily controlled and managed, will happily sit in storage until you need it, useful as feedstock for other materials like plastics).But aside from that, you could find other things to do with the same energy, such as convert it to electricity, or use it directly for manufacturing purposes.And where is your original energy going to come from? Where Fischer-Tropsch is used today, the input energy comes from coal or gas. It's useful in special situations, but it is not long-term renewable. When the required energy must come from renewable sources like solar the process will be expensive enough that it will only used for special purposes.If we want to turn water and CO2 into hydrocarbons (or cellulose), plants are already very good at this. In the longer term bio-processes will have a big part to play.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 04, 2015, 08:02:13 pm
content: Er, well... this isn't a chemistry forum, so I certainly wouldn't expect much discussion of such subjects here.I'd suggest SMDB,http://www.sciencemadness.org/But now that we're here:Quote from: abebarker on June 04, 2015, 08:10:36 amQuoteIt's almost a century old, but... okay...Quote from: m100 on June 04, 2015, 01:59:20 pmEr, it would be the other way around. Waste heat is low grade, F-T requires high grade.And a metric motherfucking shitload of itat that. (And yes, that's a technical term.)Taking whatever advantage you can of the waste heat from F-T would be nice, but it's also low grade, so you're kind of screwed.It's a lot of trouble to make a 20 m+ wide turbine to suck down a 200 degree temperature differential on tepid, low pressure steam. And a single stage has a paltry, maybe 10% efficiency (whatever Carnot says, minus real world losses), so you aren't recovering much anyway.And then you have an even larger mass of process fluid, with even lower grade heat, which means you need to be sited on a large lake, river or ocean, or you need to pump a serious amount of water through a lot more cooling towers than usual. Either way, it's more expensive than the electricity value that can possibly be produced over the entire lifetime of the plant (3-6 decades).So they don't bother.That's why most plants are 20-40% efficient. I seem to recall some newer gas or high pressure coal generators are going two stage for up to 60% (when your first stage is running red hot throughout, its waste heat becomes high enough grade to have another go at). So that's a thing.Quote from: LabSpokane on June 04, 2015, 06:31:08 pmThat'd be pretty cool, since it's otherwise, well, complete waste, and it recovers the carbon value (well, some of it). Potentially with a hazardous soup of byproducts that could be refined for rare elements.I'd be tempted to think the assorted "periodic soup" in garbage might be a catalyst all its own, but perhaps it's catalyzing the wrong direction. I haven't read much about those processes so I don't know what problems they have.I can see how feeding that kind of material directly into a conventional process would cause problems with the catalyst... all kinds of nitrogen, sulfur, chlorine and so on to cause problems.QuoteWeird place to put it; are they hedging their bets for when their oil supply runs out?QuoteThe other "nuclear sourced" fuel I commonly see proposed is iodine catalyzed thermal hydrogen. Which would be nice for hydrogen cars, if not for the hydrogen. Paired with a few carbons, it would be pretty good fuel, but we're back to the first problem, restacking carbons.I can't wait until there's an efficient and reliable electrochemical hydrocarbon catalyst. Then we can have true hydrocarbon batteries and fuel cells, and regenerate them from primary sources. (No, electricity isn't exactly a primary source, but once such a method is found, solar (photochemical or otherwise) and thermal methods should be easy to pair up. Maybe.) Supposedly there already is, but I haven't seen articles about it. (I did see the machine that claims to turn CO2 to methanol via solar and, I think, carbonate reduction, at a paltry ~2% efficiency. Which is curiously about where plants are at, so in a certain sense, it's not a step backwards.)Tim

author: IanB
author_rank: Super Contributor
timestamp: June 04, 2015, 08:31:13 pm
content: Quote from: T3sl4co1l on June 04, 2015, 08:02:13 pmMaybe not so much if you have a bunch of "stranded" gas that would otherwise be difficult to exploit. Transporting gas over large distances is expensive because of its low density. You can liquify it and put it in ships, but the economics of that will depend on the market value of the gas. Converting gas to petroleum liquids can be a way of converting a low value product into a higher value product and also making it easier to transport.

author: mtdoc
author_rank: Super Contributor
timestamp: June 04, 2015, 08:42:34 pm
content: Quote from: IanB on June 04, 2015, 08:31:13 pmTrue and it comes back to the liquid fuels at all costs argument. You can't fly planes, power ships or tanks on nat gas. Gasoline, diesel, jet fuel are necessary - even if it means that the process of converting nat gas (or coal) is net energy negative.

author: LabSpokane
author_rank: Super Contributor
timestamp: June 04, 2015, 08:49:17 pm
content: T3...,Shell locates their GTL plants at the resource, so they go to Qatar since there's huge fields of it. They have another plant in Bintulu, Malaysia. The US Gulf coast seemed like natural, but I think they soon realized that the US natural gas surplus is largely being fueled by irrational investment rather than a permanent eco/technological revolution.Shell isn't hedging their bets on Peak Oil by building GTL plants. It's just a way to get value out of a "surplus" of natural gas. The "gasoline" is a high-quality blendstock that is mixed with all the other crap that makes up gasoline. The value proposition is largely in the co-products that Sean wrote about: the paraffins, the ethanes, ethylenes, etc.The newest natural gas, combined-cycle power plants are indeed 60% efficient because of the huge temperature drop they capture between the Brayton (gas turbine) and Rankine (steam) cycles. A simple cycle natural gas turbine clocks in about 40% efficiency.As for the "quite a lot" of heat going up the stacks, no, no there isn't. Not usable heat. The flue gas going out the stack is going to be just warm enough to avoid condensation in the stack and to provide the buoyancy required by the permitting authorities - and *no more* than that. There is always the opportunity to place a heat exchanger in the gas stream to reduce the stack temperature - so there just is little to no "waste heat" in the form of un-utilized, useful work being lost out the stack.A lot of the inefficiencies in the steam cycle are related to the latent heat of vaporization of water. One has to invest energy without a return in useful work in vaporizing the water and then collapsing it back to liquid coming out of the turbine. The steam has to be collapsed because that water is then sent back to the boiler via high pressure feedwater pumps so that boiler pressure is maintained.It's the contaminants that are problem in most of the F-T "wannabe" GTL projects. They are all highly catalyst-dependent and the tars from the gasification process condense about 700F, so the whole system tends to plug up quickly. There's what I call a "trail of tears" of companies that have gone that route and failed: Choren, LanzaTech, Kior, and Range Fuels right off the top of my head. There's probably quadruple that number if you add up all the minor players that died off over the last decade. I'm not a ChemE, but the investment was well over a billion dollars, and everybody failed. Based on that, it's time to give it up and go a different direction.

author: LabSpokane
author_rank: Super Contributor
timestamp: June 04, 2015, 08:52:35 pm
content: Quote from: IanB on June 04, 2015, 08:31:13 pmExactly correct and well-stated.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 04, 2015, 08:55:58 pm
content: Right, storing or converting excess gas. And there are condensed methane tankers, but they're fairly special purpose, and tend to be docked at a fair distance from port, for, uh... good reasons.Also, subjects I should read up on before posting, not after...Quote from: LabSpokane on June 04, 2015, 08:49:17 pmHmm interesting, so they work *too well*?Seems like piping some steam in there to crack it would help, or something, but obviously someone would've tried that, and any number of other things too. Ah well.Tim

author: LabSpokane
author_rank: Super Contributor
timestamp: June 04, 2015, 09:10:40 pm
content: Quote from: T3sl4co1l on June 04, 2015, 08:55:58 pmWell, I should learn to describe better before I post.The way GTL works is:Feedstock -> Gasifier = Syngas + Tars + Char -> Gas cleanup = Syngas + Tars -> FT reactor + water gas shift mechanism = Liquid fuels + stuffThe tars go into the reactor, not out of the reactor. So it's a contamination problem, not a co-product problem. And you're exactly correct about the tar cracking. That's where a lot of development goes into. So you'll see guys doing plasma-arcs trying to crack the tars. But then we're back to the CAPEX and energy balance. If one just makes syngas then simply filters out the tars and char, about 1/3 of the heating value of the fuel is lost - hence the desire to crack the tars.At the end of the day, these GTL schemes really don't make a lot of sense. Garbage is best dealt with in a traditional WTE plant. The pollution issues associated with the WTE plants of the past are no more. New WTE plants are squeaky-clean, emissions-wise. Even the low-tech WTE processes are far better than burying the waste and allowing it to decompose.GTL processes using biomass are even more sketchy - even using purpose grown crops like eucalyptus and miscanthus. The scale-up just isn't there. The economic radius to transport biomass is 50 miles from the plant. This forces a practical biomass plant to be small - which drives up the price due to scaling factors.Worse yet, there really is no way to provide "alternative" liquid fuels to the world at the scale at which we currently consume dinosaurs. The world's agricultural capacity just isn't there and even if it was, the energy returns are silly. Corn ethanol has a 1.7:1 energy return. The energy world of the future will be different than the liquid-fuels world of today. It might not be worse, but it will certainly be different.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 04, 2015, 10:29:14 pm
content: Quote from: LabSpokane on June 04, 2015, 09:10:40 pmRight right, multiple passes.QuoteLike I said, I'd love to see a photosynthetic or electric process that turns humid air into gasoline vapors. Even if it's just the most basic step, like fixing it to formate or methanol, and requires a lot more water than mere humidity can offer, it would still be pretty cool. But that only possibly works if the efficiency is there, otherwise you're right back there growing crops. It also needs to be cheap; no Pt-doped TiO2 photocatalytic layer is going to work if you need to cover a few square miles with the stuff, plus atmospheric contamination, wear, etc.They say Brazil's sugar cane harvest is more efficient than our corn. I don't think anyone's bragging about corn's efficiency. As far as I know, corn is almost entirely about lobbying and subsidy. But then, I expect the same is true of Brazil's favored crop, so you can't really say one or the other is a neutral, free market development...So...nukes?...Tim

author: LabSpokane
author_rank: Super Contributor
timestamp: June 04, 2015, 11:00:50 pm
content: Quote from: T3sl4co1l on June 04, 2015, 10:29:14 pmIf you want irony, the new hot topic in Brazil is growing ... wait for it ... corn! Sugarcane in Brazil is extremely efficient but they are having to rotate crops. The reasons are varied, but disease and overworked soil are top ones.Brazil is a little different in that their ethanol facilities are also sugar facilities. They can dynamically change the process between ethanol and sugar production. Both sets of equipment are located on the same site typically. So, they chase whatever market is producing the best returns at the time.Sugarcane's efficiency is mostly due to the sugar yield per acre. The only valuable part of the corn is the kernel, whereas maybe 80% of the cane plant (stalk minus the leaves, which are called "straw") has sugars that can be extracted.The other part of Brazil's ethanol "efficiency" lies in what they *don't* do, which is install decent pollution controls on the production facilities. The skies around those mills is brown for miles and miles and miles. The sugar facilities there could never be constructed in the US or Europe. That is supposed to be changing with new environmental regulations. The state of Sao Paulo is supposed to be modeling its emissions limits after European standards, but whether that actually occurs for new plants remains to be seen.Believe it or not, Brazil's current Rousseff administration does not currently have a very cozy relationship with the sugar and ethanol producers. The sugar/ethanol industry used to have a lot of government influence, however, and I'm sure they do in congress still.What all the ethanol production has *not* translated to is cheaper fuel prices for Brazilians. 100% ethanol fuel costs just as much as the E25 ethanol/gas mix after one takes into account the BTU differences. Ethanol has also not translated into energy independence for Brazil. Key evidence of this is that the United States is Brazil's offshore petroleum refiner. Because no one wants to risk building a refinery in Brazil, crude oil in excess of what Petrobras can process is shipped to the US Gulf Coast, where it is refined and returned to Brazil in the form of liquid fuels, etc. A second piece of evidence is that Brazil continually has to alter the ethanol/gasoline blend ratio because of ethanol shortages. So, even for the most "efficient" ethanol producer in the world, biofuels have not been a silver bullet for the liquid fuels problem.As for nuclear, it really is the only remaining option to move to an electric economy. I wince every time I see a plant get decommissioned without a new one being constructed.

author: mtdoc
author_rank: Super Contributor
timestamp: June 04, 2015, 11:30:22 pm
content: It all comes back to physicist Tom Murphy'sAlternative Energy Matrix. Choose your poison...

author: eas
author_rank: Frequent Contributor
timestamp: June 05, 2015, 01:50:57 am
content: Quote from: LabSpokane on June 04, 2015, 09:10:40 pmYeah. Photosynthesis is amazing, but it isn't exactly efficient. Wikipedia says 3-6% of solar radiation actually makes it into biomass, which sounds about right based on what I remember from looking into this at more depth. For transport that can be run off electricity, PV is going to be a better use of land (or rooftops / parking lots, etc). For large transport ships, it sounds like CNG isn't exactly impractical. It's not like they can't make the room, and probably isn't any more ridiculous than the lengths they go to do burn C-grade bunker oil (think tar) in their huge piston engines.

author: eas
author_rank: Frequent Contributor
timestamp: June 05, 2015, 02:14:45 am
content: Quote from: LabSpokane on June 04, 2015, 11:00:50 pmI'm not anti-nuke, but I really don't get why people romanticize nuclear power so much. In the US, at least, the civilian nuclear power industry has been decades and decades of disappointments and failure. Blaming politics isn't going to cut it either. The industry had plenty of political cover, money and plenty of chances to get their shit together, decades worth. Perhaps I'd feel differently if I thought they were our only remaining option. I don't.

author: IanB
author_rank: Super Contributor
timestamp: June 05, 2015, 02:35:20 am
content: Quote from: eas on June 05, 2015, 02:14:45 amWell, France gets more electricity from nuclear generation than from any other source. It's really a matter of strategy and investment.If investment is actually made in nuclear power using modern technology it can be very effective. But many times the nuclear power plants are old and creaking and using old technology. Like San Onofre in California which got shut down because it was so old it became too expensive to maintain.The challenge with new nuclear is the public opposition. People hear "nuclear" and they think bombs and radiation. So the discussion becomes emotionally charged and never reaches a rational conclusion.

author: LabSpokane
author_rank: Super Contributor
timestamp: June 05, 2015, 04:19:57 am
content: Quote from: eas on June 05, 2015, 02:14:45 amI'm just looking at what MWe are going offline versus what's replacing them. I don't care what the renewables-only fans say, we need baseload and load following. I'm not a nuclear industry insider, so I won't speculate as to the internal workings of the industry.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 05, 2015, 07:50:52 am
content: Quote from: LabSpokane on June 04, 2015, 11:00:50 pmYuck! As I recall, they burn the "straw" part, too. Leave it in the field. Not quite slash and burn, but also not the nicest.It bugs me because they're losing heat right up the stack. That soot and smoke could be burned. Is it that hard to stoke bagasse? In an automated process, maybe, I don't know...QuoteI remember when E85 was introduced here. It came in at a surprisingly competitive price (back when gas was $2.50ish (the first time), I think?). Don't recall passing a station with it when gas peaked over $4.something, but the ones I've seen more recently, it hasn't been competing at all.The only way you can drum up widespread adoption of something like that is by heavily subsidizing it, then restricting the original until people are screwed with the new stuff and you ramp the price back up (which arguably satisfies certain global warming people doubly). Obviously, they weren't willing to go that far, not just yet anyway. (Perhaps equally apparent, they didn't have the capacity to go there, either?)Quote from: eas on June 05, 2015, 02:14:45 amThe record is surprisingly good for what mess it's created in some places:http://en.wikipedia.org/wiki/List_of_nuclear_power_accidents_by_countrythe worst offender being Russia(/former USSR), really.Inventing nuclear power has been messy, especially under military control. Several excellent scientists died in the course of early experiments (Slotkin and others). Early reactors were unstable and deadly (SL-1). The general area of Hanover, WA is an EPA Superfund wasteland, and likely to stay that way for oh about the next 100,000 years or so. But that pales in comparison tohttp://en.wikipedia.org/wiki/Lake_Karachayand nearby areas, which contain almost as much material as Chernobyl released over a huge area.Operating nuclear power stations has not been messy. The commercial record since, oh, 1965, and not counting plutonium-proliferating relics like Chernobyl (an inherently unstable graphite-moderated design), has been quite good. The accidents have been very expensive, from time to time, and occasionally messy, but fatalities have been negligible.The worst incident in the US was TMI, but to be fair, it did exactly what it was supposed to. Gas was released, but no fallout, and all the contained materials have been/are being dismantled and stored with other waste. (Ah, not that anyone has decided what to do with our mounting piles of waste...)After Russia, and early US development, Japan is surprisingly a big part of the record. It seems they tend to push things much farther; smarter than the Russians did, but still dangerous in the end.The biggest fear people have is that they don't know anything. There's no education, because, why would people want to know about something they already think is impossibly dangerous?The biggest hazard, in my opinion, is that failures quickly ramp up in severity. Whereas most human endeavor escalates gradually, which provides a nice negative feedback mechanism for squishy brains to learn from. If you want to eliminate high level nuclear accidents, you need to design systems to fail or decay gracefully, to generate that negative feedback, and incentiveize safety rather than punish for accidents and cost.The biggest hazard is the incessant and inevitable force to improve investor yield. Nuclear power shouldn't be considered an investment opportunity. It should be infrastructure, you know, that "non sexy" thing. It should be made as solid and reliable as possible, then kept to those standards. If it starts making more money than usual, that should be seen as a warning sign if anything!And really, this isn't exclusive to anything. It applies to all things of greater than personal human scale: coal and other power plants, dams, building construction... even driving a car (which is still greater than personal human scale because your legs can't push two tons at highway speeds, can they?). All of which have catastrophic problems for someone or other when they go bad.Tim

author: LabSpokane
author_rank: Super Contributor
timestamp: June 05, 2015, 02:46:34 pm
content: Quote from: T3sl4co1l on June 05, 2015, 07:50:52 amThe black soot is the product of inefficient combustion technologies in conjunction with a lack of emissions controls. The older Brazilian boilers are based on a grate technology that is just a metal grate with air blown up through it. It's cheap, but doesn't consume all the carbon. Pollution control in Brazil is typically a wet-scrubber, which is just a tower that sprays water and possibly a reagent that the flue gas goes through. It can remove sulfur, but doesn't do well at all with particulate. In the US and Europe, particulate control is done using electrostatic precipitators or baghouses. The bag house is basically a gigantic vacuum cleaner. The flue gas is pushed through thousands of fabric bags. Baghouses are amazingly effective for how simple they are. Particulate removal rates are over 99%.As for the ethanol, I think it could be great if it was consumed at the source. Ethanol makes little sense in Florida, but could be great in Iowa. A fuel with a 1.7:1 energy return needs to be consumed at the source to make any sense at all.======Just a note:And I don't mean to be too critical about Brazilian ethanol. I think the energy return is on the order of 7:1, if I recall correctly, which is on the order of deepwater petroleum. But, even in ideal circumstances, Brazil cannot power its entire economy off biofuel. So, this whole notion of biofuels as a total replacement for what we consume today in petroleum, is just a fantasy.

author: SeanB
author_rank: Super Contributor
timestamp: June 05, 2015, 03:31:00 pm
content: A quck note about catalysts. The synthol plants typically use nickel, because it is cheap. Needs to run hotter than alternatives like Pt and Pd, but it is much cheaper, plus it is not nearly as susceptible to poisoning by metal ions as the noble metals. You want to run in a very pure stream, with very low levels of anything other than CO, H2, H2O, C, as any metals like lead or mercury ( both of which are naturally present in pretty much everything, and which are in coal, but are very high in things like municipal waste) will reduce catalyst efficiency very severely. Ni catalyst can be rejuvenated relatively easily by simply heating it up further to drive off the impurity, which you can do a few times before you ri[p it all out and electrorefine it. The noble metals are typically used as a thin film ( like in your cat converter in the car, you need around 1000 to get a gram of Pt or Pd out of the scrap) so you cannot reform them, you have to acid strip them off the matrix ( or strip the matrix off the noble metal in some cases) then basically refine them again to metal.