Vacuum hydrous pyrolysis?

  • Thread starter gfought
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  • #1
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Main Question or Discussion Point

i have searched the web over looking for some kind of chart for hydrous pyrolysis.
im not extremly smart but i grasp the concept.
but still not real sure, know water boils in a vacuum at lower temps,
so is that the same for most organics.
say i create a vacuum tank, containing water and organics, and applied heat,?
would the organics gasify at lower temps?
and if so is there somewhere i could get a chart
showing thermal decomp of differnt organics degree/psi over time?
everything contains hydrogen,
could it be collected this way?
 

Answers and Replies

  • #2
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gfought,

Welcome to PF!

I am sure you have read this:

http://en.wikipedia.org/wiki/Hydrous_pyrolysis

The technology of converting high nitrogen content animal waste into hydrocarbons, specifically oil, is an emerging technology with potentially large economic implications. Full scientific reports and detailed studies are likely going to be proprietary and hence not generally available to the public. General descriptions of particular processes with vague hints for publicity are released primarily to encourage funding and encourage speculative investment.

If you read the article referenced, you should note that the processes mentioned involves Heat and Pressure. There is no reason to expect that any of the processes would be meliorated by reducing the pressure (especially to the point of a near vacuum).

Steam Cracking is not a new concept, being first patented in 1891 in the Russia. To gain a better idea about the general process, you might read through this:

http://en.wikipedia.org/wiki/Cracking_(chemistry)

Just to "run the numbers", the US consumes roughly 21 million barrels of oil per day. At 159 liters per barrel and 0.873kg/liter, the weight of the crude oil consumed per day = 2.9 Billion kg/day.

There are roughly 61 million pigs in the US on any given day with an average food consumption of ~3kg per day per pig. Assuming the pig offal is approximately 4kg per day per pig (higher than food intake due to water intake), this implies there is roughly 244 million kg of pig offal available per day for potential conversion to oil via some yet to be determined industrial process that we will assume could approach a 20% yield of offal to oil. So, 244 million kg of offal based on the 20% assumption might yield 49 million kg of oil, or roughly 350,000 barrels of oil/day.

350,000/21,000,000 = 1.67% of the current US daily consumption. Obviously this could be extended to other domesticated animal offal, and quite possibly human offal; however, even with the rather optimistic 20% yield and no discussion about the energy consumed to gather the offal or convert it, the projected production of oil from offal would fall far short of our current demand for oil, though it has the potential to be the single largest "renewable" source of energy to date.

Anyway, back to your OP.

showing thermal decomp of differnt organics degree/psi over time?
everything contains hydrogen,
could it be collected this way?
Actually it is not the collection of hydrogen that is important per se, though it has the potential to emerge in the future as an alternative to hydrocarbons. Organic hydrocarbons are economically important because they have a high energy content and are convenient to store. While pure hydrogen has a high energy content, it is expensive, dangerous and difficult to store when compared to hydrocarbons.

The importance of pressure and heat in the presence of specific catalysts is fundamental in the conversion of organic material in general, attempting to convert a particular type of organic material to a specific family of hydrocarbons is a complex process that is first done in a laboratory and then possibly refined until it is economically viable through engineering.

Fish
 
  • #3
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thanks for the welcome fish
now couple things i dont agree with, but stop me if im wrong
you said hydrocarbons are the future, but hydrocarbons as just hydrogen and carbon right?
which after you use the hydrogen you have carbon, and its useless.
that and hydrogen autoignigtion temps are 997 degrees compares to gas at 475
i found something called outgassing, basicly vacuum pressure falls below vapor pressure,
which makes it release vapor, so it would help in both pyrolysis and hydrous pyrolysis
ok so i dont have a lab, what happens if i boil water? i get hydrogen and oxygen right?
 
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  • #4
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but stop me if im wrong
you said hydrocarbons are the future, but hydrocarbons as just hydrogen and carbon right?
STOP. Actually, what I said is:

"it is not the collection of hydrogen that is important per se, though it has the potential to emerge in the future as an alternative to hydrocarbons."

which after you use the hydrogen you have carbon, and its useless.
I think you fail to understand some rather key concepts about both energy and chemistry. While the heat of combustion of pure hydrogen is roughly three times as high as that of typical gasoline, the energy costs associate with storing the hydrogen are orders of magnitude higher than the costs associate with storing hydrocarbons.

"there is actually more hydrogen in a liter of gasoline (116 grams) than there is in a liter of pure liquid hydrogen (71 grams)."

taken from: http://en.wikipedia.org/wiki/Hydrogen_economy

I would strongly advise you to read the above article.

ok so i dont have a lab, what happens if i boil water? i get hydrogen and oxygen right?
NO. You get "steam", which is water in gaseous form. Disassociating the hydrogen atoms from the oxygen atom requires electrons. How these electrons are provided and the energy input to drive the disassociation are the focus of study you reference in your OP. Hydrous pyrolysis is a process for converting organic matter into hydrocarbons, not pure hydrogen, and high pressure steam in combination with a catalyst is the method for driving this reaction. Further more, the energy released when oxygen and pure hydrogen are combined to form water is always less than the energy required to disassociate them.

I would urge you to spend some time reviewing basic chemistry and physics prior to exploring hydrous pyrolysis.


Fish
 
  • #5
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ok in the article you told me to read it states that only 4 percent of hydrogen production is producted by electrysis, and it also stated that decomposing water requires electrical or heat input
very high heat can dissociate water to hydrogen and oxygen
i understand its not easy to contain or store, but thats not my question
steam reforming, water gas shift, all priniples that have been around for a long time,
catylis is use to make the temp need to do this possible,
well a vacuum would make the temp need to lower as well,
ill do more research, and appreciate the critasim, its exactly what i need
thanks fish

gfought
 
  • #6
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ok fish check this,
i got ahead of my self and allowed a whole realm for
naysay, so ill bring it back, and set aside the issues
of storage, and efficiency of production, these are not my questions
so forget that for now,

my question was vacuum hydrous pyrolysis
with the help of fish i found my answer.
still ending in decomposing, but just called

http://en.wikipedia.org/wiki/Thermolysis

Thermal decomposition, or thermolysis, is a chemical decomposition caused by heat.
Water, when heated to well over 2000 °C, decomposes to its constituent elements:

2 H2O → 2 H2 + O2


http://en.wikipedia.org/wiki/Clausius–Clapeyron_relation

is a way of characterizing a discontinuous phase transition between two phases of matter.
On a pressure–temperature (P–T) diagram,
which is how outgassing in a vacuum works
if vacuum pressure falls below vapor pressure

http://en.wikipedia.org/wiki/Outgassing

and knowing the vapor pressure of water

http://en.wikipedia.org/wiki/Vapor_pressure_of_water

and the clapeyron relation, one could figure out how much vacuum pressure
would be needed to decompose water at given temp,

like i said fish im not extremly smart, but theres my basic physics
am i missing something?
now im not saying its possible in my garage,
but why wouldnt this work

gfought
 
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  • #7
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gfought,

If you heat water to "well over 2000C", and disassociate the molecular bonds between the oxygen and hydrogen atoms, and then return the mixture to STP the vast majority of the atoms will spontaneously recombine into water during the cooling process. This is different from "steam cracking" or "steam forming" hydrocarbons in that the hydrocarbons already contain a large number of hydrogen atoms, and the carbon atoms tend to form CO and CO2 with any spare oxygen atoms.

Attempting to use a vacuum is problematic because as you lower the pressure, the water boils to fill the vacuum. If you are creating this vacuum using a vacuum pump, you will eventually "pump all the water out". If you are thinking of using a cylinder with a movable piston to create the vacuum, you would need to start with a very small volume of water and a very large cylinder. "At standard temperature and pressure, pure steam (unmixed with air, but in equilibrium with liquid water) occupies about 1,600 times the volume of an equal mass of liquid water."

In almost all cases involving hydrocarbons, the temperature AND the pressure are critical. In a theoretical world we can do all kinds of things, but in the real world physical limitations, costs and actual results dictate things like the temperature and pressure of reaction.

So, I will agree that in THEORY we should be able to "slide" the pressure and temperature around as much as we like, but this is a silly argument because finding the pressure and temperature to force a particular reaction is the point of hydrous pyrolysis. And the point is, that it occurs at fairly high temperatures AND pressures, not at low pressure much less a vacuum.

Please understand, your OP was about using a vacuum to achieve hydrous pyrolysis. Hydrous pyrolysis is a process for decomposing organic matter and is distinctly different than "freeze drying" or "vacuum drying" where water is removed from from organic matter. Hydrous pyrolysis is a process that involves heating in the presence of water, at specific temperatures and pressures specific things happen to organic material, if you change the temperature, or the pressure, different things happen.

In "brewing beer" organic matter, typically crushed barley, is heated in the presence of water to break down complex proteins into sugars suitable for consumption by yeast. If the barley and water temperature is not high enough, very little conversion occurs, if the temperature is too high, tannins are released which ruin the flavor. The typical temperature range is between 140F and 158F. This is an example of hydrous pyrolysis, and lowering the pressure would not alter the temperature required to break down the proteins. This is TYPICAL, not an exception.

A "Pressure Cooker" typically reduces cooking times tremendously. If you took three identical pot roasts and placed one in a "crock pot" with water @ 212F, one in the oven @ 300F and one in a "15psi pressure cooker" what is the difference? The one in the "crock pot" might reach an internal temperature of 195F in 8 hours, the one in the oven might reach an internal temperature of 195F in 3 hours, the one in the "pressure cooker" might reach an internal temperature of 195F in 35min, but they would all have a slightly different texture and taste, with the crock pot and pressure cooker being the "closest" to each other. In NO case would the meat "cook faster" or "better" in a vacuum.

I think the problem is you are confusing hydrous pyrolysis with boiling point and molecular disassociation. Again, I would urge you to review basic chemistry and physics, or at the very least, examine cooking to get some "real world" experience with what you are talking about.

Fish
 
  • #8
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so what your saying is i cant wrap my little brain around such a big subject,

so you can increase pressure, which increases temperature, which increases boiling point, as well as criticl point
but the tempature of decomposing stays the same?

decrease pressure, decrease temperature, decrease boiling point, decrease, critical point
yet the decomposing temperture stays the same,

i thought what was true in one aspect of physics was true everywhere.


gfought

my gf does the cooking
 
  • #9
247
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i thought what was true in one aspect of physics was true everywhere.
No, that's the problem with reality, it is generally infinitely more robust than theory. Just because you understand PV=nRT does NOT mean that chemical reactions are predicated by it.

so you can increase pressure, which increases temperature, which increases boiling point, as well as criticl point
but the tempature of decomposing stays the same?
Actually what I am saying is that the chemical reactions that are "interesting" occur in narrow regions of pressure AND temperature. If you "change" the pressure and temperature you may also change the result.

Similarly, changing the "type" of organic material can produce very different results. To return to the cooking analogy for a moment, if you took a 1kg chunk of wood, a 1kg chunk of beef and a 1kg chicken and placed all three in identical pressure cookers with the same amount of water and allowed each of them to cook for 40 minutes, you would have three very different entrees.

The key to making hydrous pyrolysis an economically viable pursuit is finding a sufficiently plentiful organic compound that can be readily converted to a usable energy source. One example of this is turning corn into ethyl alcohol. This is done by first breaking the proteins down into sugars (hydrous pyrolysis at a specific temperature and standard pressure); next allowing a specific type of yeast to consume the sugars (again, at a specific temperature and standard pressure), and finally distilling the alcohol (distilling = separating the alcohol from the water). The final step is generally achieved at standard pressure and a specific temperature; however, in this case lowering the pressure and temperature could achieve the same result because the only critical portion of this process is the relative boiling points of water and ethyl alcohol. It is typically done at standard pressure because this is the most economical method.

Turning corn into Ethyl alcohol generally consumes more energy to produce than it contains, hence it is not practical to use this method for large scale production of fuels (though it is a time-honored tradition for producing "sipping whiskey"). If there were a way to convert corn into a usable fuel that contained more energy than the process consumed, then this would be a potentially huge discovery. For instance, "corn oil" can be extracted and turned into "bio-diesel". You might consider reading through that process here:

http://en.wikipedia.org/wiki/Corn_oil

Part of this process does actually employ a vacuum.

While corn based bio-diesel is touted as a "cheap" alternative to fossil fuels, it is only "cheap" as a waste product of the cooking industry. "New" corn oil sells for slightly over $4/gallon in bulk (where as "used" corn oil might sell for as little as $0.25/Gallon from a restaurant.) Additionally, if the demand for corn were to dramatically rise, it is certain the price would rise with it.

Anyway, that is two distinctly different examples of how corn (an organic material) can be converted into fuel. Is there a third way? Almost certainly, and it is quite likely that method will involve hydrous pyrolysis as well. The real question is, "Is there a process which will have a high enough yield at a low enough cost to be economically viable?"

Fish

PS: Hydrous pyrolysis IS COOKING, so you might ask your GF about it ;-)
 

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