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Author: Subject: efficent conversion of wood to energy
ChemGrl5
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[*] posted on 23-12-2005 at 09:54
efficent conversion of wood to energy


We have been thinking about starting a "small scale" or (experimental), energy production facility. We currently have access to tons of wood refuse and are just in the planning stages. So we would like to inlist the help and advice of all intrested forum members. I am not a chemical engiener so all the help I can get will be appreciated. Firstly capitol is limited so starting from scratch I need help in designing the very cheapest way of processing 2-5 tons of material on a monthly basis. For example stainless tanks and pluming are very expensive and out of my price range for a start up. I need help in designing a plant to process this material in the most economical way possible, as the plant can be upgraded and expanded later. In addition I am comsidering using any fuel produced to directly produce electrical energy on site, preferably without any more refinement of the fuel produced.
I know this is alot to ask, but I know the members of this board are capable and and full of ideas. So I am requesting help from serious members only. I would like to have this project up and running in the comming year.

Thank you for your attention,
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12AX7
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[*] posted on 23-12-2005 at 13:35


Well, you need a burner and a heat engine. Burner is easy, look up a wood stove. Maybe supe it up with some insulating refractory so it operates at a higher temperature. Then you need a heat engine of some sort to turn temperature difference into voltage difference that can be sold. If you can make a 100HP+ Stirling engine, there you go. A steam engine would work but has crappy efficiency and high pressure steam is nothing to piss around with. Internal combustion is pretty much out of the question, unless you want to make a gassification plant (certainly possible).

Edit- this should be moved to technochem or misc.

Tim

[Edited on 12-23-2005 by 12AX7]




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ChemGrl5
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[*] posted on 23-12-2005 at 16:13


Thanks Tim

Right now I am trying to decide on a process. Should the wood material be processed into ethanol, methanol, or as you said gasification, and then the product used as a fuel to run a power plant of the appropriate size. All have advantages and disadvantages, and these are the things that I am trying to thik about rigt now. ethanol is a good clean fuel, methanol can be used to produce biodesiel, but does not have alot of economic value in and of itself, gasification has the added "benefit" of producing pyrolignious oil from which many other interesting products can be seperated. Gasification is the more interesting process from a chemistry standpoint but it is also the one with which I am least familiar. I am wondering now if one could use the wood to produce ethanol/methanol and then go on from there and continue the distillation process to produce gas and the pyrolignious oil and be able to produce these other chemicals as well.

So far I know we will need a hammer mill to process the wood, a pre-mix or slurry vessle, a "digester" or main reaction vessel, fermentation tank, distillation vessle, and storage for the end product. What else will be needed? Idealy i would like to be able to produce electrical power without having to do anything else to these fuels.




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[*] posted on 23-12-2005 at 17:49


I will list some assumptions, which I think are in line with yours, then make a conclusion, without doing any research:

1. Lowest capital investment
2. All off-the-shelf, proven equipment
3. Requires the fewest permits
4. Cheapest waste disposal
5. Overall cheapest
6. Least hassle to you

Do what everyone else does: Buy/build a small fuel burning, steam driven, electrical power plant.




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halogen
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[*] posted on 23-12-2005 at 18:51


"high pressure steam is nothing to piss around with"
What was that experiment where two pressurised steam filled trains were crashed together and killed a bunch of people?




F. de Lalande and M. Prud'homme showed that a mixture of boric oxide and sodium chloride is decomposed in a stream of dry air or oxygen at a red heat with the evolution of chlorine.
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[*] posted on 23-12-2005 at 20:55


I belive it was the great texas train crash and crush set up by William G. Crush to generate publicity for his company and use up two old trains they had. The Trains hit and exploded killing two young men, and women, and injuring six.

Sounds like it would have been quite a show :P .




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ChemGrl5
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[*] posted on 23-12-2005 at 22:39


Try to stick more to the point please, I need help here. In addition to the things I mentioned above I am trying to find information on if and how metal contaminants might affect the fermentation process, specificly iron. I think this will be ok. However if I use a dry distillation process to gassify the wood how will these contaminants affect the products produced?



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12AX7
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[*] posted on 23-12-2005 at 23:17


I think you're missing the point and overcomplicating this, a horrible amount.

Tell me, if you want the maximum energy out of your wood- how are you going to get it by performing operations that reduce yield and consume energy to make that product?

If you're looking to make a more portable product, such as alcohol or gasoline, these are acceptable losses if it works out economically. Otherwise, if you're going to burn the stuff anyway, I don't get it, why not burn bulk wood? It's very easy to set up a grate and air draft and keep a fire stoked.

Tim




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[*] posted on 23-12-2005 at 23:53


You could also make charcoal for barbeques too and if you have any alcohol you could make igniter fluid?
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ChemGrl5
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[*] posted on 24-12-2005 at 08:25


Well I my be overcomplicating this, I have a tendancy to do that. Basicly this would be a large ongoing recycling project.
I am not sure the pollution created by the straight burning of wood would go over well in my area, without installing a scrubber or something. I already have all this waste , it is a "renewable" resorce for me. So my line of thinking now is how can I use this material to spring-board a small ethanol/methanol plant, for the experience and the fun of it. Idealy sometime in the future it would break even and possibly grow, to do this goods or services have to be sold. well that can take all the fun out of experimenting, running around trying to sell stuff and all. Thats where the power plant comes in. It will be easier to sell power to the electric company than it will be to sell alcohol on the open market. Leaving me free to experiment with fermentation processes and plant design.




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[*] posted on 24-12-2005 at 09:10


To cut down on visible emissions from the burning of wood scrap you need only to employ a forced air induction combustion system. Basically you have a heat resistant`chamber that you feed your scraps into, preferably by mechanical means, auger etc. You could use an old wood chipper to reduce the scraps to the proper size. You then have blowers forcing air into the system to create a high temperature combustion. This pressurized burner will keep emissions low and efficiency high. Go take a look at the newer styles of pellet stoves for an idea of how clean this type of combustion can be. The exhaust gases are then led through a plurality of pipes, i.e., heat exchanger tubes that either pass through a boiler tank containing water or some other sort of heat exchanger. The generated steam can be used any number of ways. High pressure is not necessary but is more efficient than low pressure steam. If you are using a steam turbine you will need high pressure but I am sure that you are not willing to invest the hundreds of thousands of dollars required for that technology. You can make some serious power from an old single cylinder steam engine if your boiler is big enough. Old low pressure heat exchanger boilers are a dime a dozen in used equipment yards. They are all being replaced in industry with newer higher efficiency units due to the cost of energy these days. I would bet you could find any number of them for the cost of the scrap.

Making charcoal from the scrap is another money making scheme. Co-generation of power using the waste gasses from the cooking of the charcoal is possible but the heat input for the distillation of the wood will consume much of the energy. Possibly you could capture the waste heat for something. Making charcoal is a filthy nasty business though so if you are a clean freak, forget that shit.

One last scheme for making some cash would be to convert the scrap to wood pellets. You would need to be able to chip the scrap. Separate with magnets and metal detectors for and metallic waste. Next you grind the chips down to saw dust, mix with a binder like CMC or dextrin then press into pellets. I would recommend a California pellet mill for that type of work. You could probably cobble together most of the things you would need for maybe less than $10000. Obviously not a good business to stary if you live in Florida! Getting the contact to haul away saw dust from mills would give you a material that would be ready for pressing immediately without all the size reduction and sorting issues.

My personal opinion is to forget about making alcohol. This starting material is expensive to put into a fermentable condition. Unless you are running a state of the art facility you will be just wasting your time.
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[*] posted on 24-12-2005 at 16:20


Plurality :)

Someones been reading too many patents. I agree, fermenting wood is not an easy way to make power. You might have to treat with sulphuric acid to break it down, the alcohol content of the product will be very low. An efficient distillation system will be a nightmare. I think it will be really hard producing net energy even assuming the wood is free and limitless. Most companies that do this in order to sell ethanol as a biofuel seem to use *propane* to run the still, yeah, I cried "cheat" too but its so much cheaper than it would be to use the ethanol 'fuel' they are selling and waste burning can't be controlled well enough aparently.

I wonder how long a stirling cycle engine would take to pay for itself powering a generator? That could be run by burning wood directly and should be more efficiant than steam.
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[*] posted on 24-12-2005 at 16:54


I always thought plurality sounded better than, "a bunch of".

Has anyone ever managed to do anything useful with a stirling engine other then make a cute physics demonstration toy? I don't think they generate much torque compared to a steam device of comparable size.
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[*] posted on 24-12-2005 at 17:40


AFAIK, it's just a matter of time before we stoke up our cars and putter off with a Stirling under the hood, but I don't know what the buzz is with the technology.

I don't see what you think is bad with outright burning wood, my foundry furnace leaves no smoke and no odor when it's stoked good and hot (yellow heat at least). A good chimney will draw more than enough draught, keeping you from resorting to blowers.

Tim




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[*] posted on 24-12-2005 at 17:51


Build one of these:


http://www.nyethermodynamics.com/nt6/
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[*] posted on 24-12-2005 at 18:06


In my opinion you will most likely be puttering off on the power from a hydrogen fuel cell or even more likely a reformer type cell long before you see a practical stirling in a car.
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[*] posted on 25-12-2005 at 02:31


I would look into Gasification. There are people who actually have a small trailer they tow which is a wood gasifier that runs the vehicle from scrap wood they find on their trips. It is mentioned in the following link, which also contains many other ideas. I know Tim mentioned it already but I didn't see anyone give any links for you to look at.

http://www.green-trust.org/woodgas.htm

And another: http://www.woodgas.com/gasification.htm

You could distill off many volatiles from wood which can be used for energy, and also produce a smoke flavoring product depending upon the type of wood used, which could add a little more value to your efforts. Heating and distilling off the smoke flavored liquid is done with hickory wood to make a barbeque flavoring liquid.

[Edited on 25-12-2005 by IrC]
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[*] posted on 25-12-2005 at 08:00


Have you seen this guy's wood burning turbine? Perhaps a PTO shaft on the turbine blade to an alternator or through a worm drive reducer? Off the shelf parts.
http://www.nyethermodynamics.com/nt6/
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[*] posted on 25-12-2005 at 11:06


The concept of a very small space heater or electrical power plant is one which has fascinated me for years because of a newspaper article I read about 20 years ago: A Protestent minister living in the US Northeast heated his house for the whole year solely on junk mail, that he received. He would roll it into logs and burn it in a stove. :o

It seems that if a mad scientist could invent a user friendly system/device based on this concept he might find a sizeable market for said device.




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[*] posted on 9-1-2006 at 13:55


Crucial question : is it treated timber? If so you are going to have to deal with either toxic flue gasses or toxic ash from any combustion process.

There is one other thing you might do with your waste wood : shred it, then compress it into fake "logs" for other people to burn! You make a tidy profit from sale of these "logs" and the ash disposal problem goes away.




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[*] posted on 10-1-2006 at 02:00


I would be curious to find out what would happen if wood material was superheated in an oxygen absent chamber and the vapours condensed afterwards. The intention is basically to try and harness the energy lost when wood is burned to make charcoal, which is then burned again to release more energy. If you compare the weight of a piece of wood to a piece of charcoal the same size there is a remarkable difference. Minus the water I wonder how much of that weight is useable fuel.



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[*] posted on 10-1-2006 at 12:07


Interesting idea, but its worth noting that when wood converts to charcoal without oxygen, it actually gives out energy.

So for a given amount of timber the charcoal and burnable byproducts produce less energy when burned than the wood would :)
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[*] posted on 10-1-2006 at 12:52


Quote:
Originally posted by froot
Minus the water I wonder how much of that weight is useable fuel.


Humm well as I recall, retort method charcoal is quoted as 40% or so efficient, by weight. The composition is, roughly, (CH2O)n, with a proportion of 12 + 18 = 30. 12/30 is, of course, 0.4, or exactly 40% if the distillate is entirely water.

I'm guessing lignin and other constituents have a higher carbon content. Lignin is aromatic, no? That, plus some not-too-hydrated bits and pieces would contribute well to the residual carbon content, given the carbon compounds distilled.

BTW, you'll get a lot of water and methanol (a.k.a. wood alcohol for this reason) in the distillate. If you want to process say, a hundred pounds of logs and completely fraction all the chemicals out, I bet you can get some interesting compounds at least.

Tim




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[*] posted on 12-1-2006 at 00:12


This is almost the sam thing i was working on, but the nature gas pipe lines are not in this area.
I was going to use a wind turbine and the farm was next door to a pine forest, ever second tree the cut down, so there was going to be alot of wood. The induction furance was then going to heat it to that stage. Hay i suck at words,U2U and i will give you the schmitics.
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[*] posted on 8-2-2006 at 07:51


Don't burn wood, burn lamers!
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