Hydrothermal carbonization (HTC)

[malcolmf]

Hi all

This might rattle a few assumptions.

Hydrothermal carbonization is another way to extract carbon from biomass, an alternative to pyrolysis / charcoal making. If pyrolysis is "baking biomass in the absence of air", then HTC is "pressure cooking biomass till it boils dry". For details see Magic Coal from the Steam Cooker, from the Max Planck Institute in Potsdam.

 

This is a serious contender for saving the planet.

• Even lower tech than char-making.
  
• Exothermic, i.e. it gives off energy. As with pyrolysis, some of this energy can power the process while the remainder can be put to useful work and get carbon credits as bioenergy (space heating, etc.). Presumably there is also enough steam kinetic energy at scale for some electricity generation.
  
• No emissions. Just a risk of entertaining lab explosions until you understand how much energy is released.:umno:
  
• Carbon conversion efficiency near 100% in all cases as opposed to pyrolysis 60% in a high-tech retort and something around 20-30% or worse in a low-tech backyard, and 10% for composting.
  
• Operates in water so efficiency is not affected by the moisture content of input biomass: trumps pyrolysis here.
  
• Product controllable by length of cooking: 5 hours produces carbon-rich topsoil, 12 hours produces a kind of coal.
  
• Only "kind of" because the product is nano-porous. It is not known whether the porosity would offer a terra preta type of environment to soil organisms, but it would almost certainly offer the same water and nutrient retention properties.
  

The Institute calculates that Germany's easily accessible waste biomass would balance out about 10% of the country's carbon emissions, allowing it to exceed its current Kyoto target with room to spare. Governments could be slavering at the chops for this once it becomes better known.

 

The link is a must-read. Enjoy.

 

M

[Turtle]

Hi all

This might rattle a few assumptions.

Hydrothermal carbonization is another way to extract carbon from biomass, an alternative to pyrolysis / charcoal making. If pyrolysis is "baking biomass in the absence of air", then HTC is "pressure cooking biomass till it boils dry". For details see Magic Coal from the Steam Cooker, from the Max Planck Institute in Potsdam.

 

The link is a must-read. Enjoy.

 

M

 

sounds great! thanks malcom.:) someone could make a killing making home units. a killing might be what i get if i tried it on my own without instructions at home. :lol: :)

 

I see the article mentions a requirement of a catalyst, but it is never named? Do you know what it is? :cup: :umno:

[Turtle]

...And their reaction is an exothermic one, meaning that heat is created spontaneously. In fact, during one of the experiments, the reaction chamber exploded because too much energy was released. ...

:eek: :eek:

 

No worries! The Tortuga 2007 Home Hydrothermal Carbonizer is equipped with a pressure relief valve & vent stack making it safer than your home water heater. We offer as well, plans for an optional capture tank to connect to the relief. ;)

 

...Robert Schlögl’s new methanol catalysts

in Berlin....

 

It's not clear if methanol is the catalyst, or if the catalyst makes methanol? :o

 

The carbonized pinecone still retains its original form, but it is no longer a pinecone, but rather, strictly speaking, a nanoproduct.

 

...

 

But it gets even better, because Antonietti’s process does much

more: inside the steam cooker, biomass is not abruptly converted to coal. Instead, gradual processes take place that form intermediate products that are at least as useful as the end product carbon. ...

 

I wonder if the process might find employment as a method of preparing plant specimens for study? What might we learn from examining a carbon nanosphere 'cast' -so to speak - of plants? Maybe learn something we don't know? :shrug: :cup:

[Gerrit]

WOW! Deal me in!

 

The name of the catalyst? They might have given it away. Check out the photo at the top of the article referred to above. Note the labelled plastic bottle on the work-bench. It is fitted with a squirt. Could that be it? Can anybody magnify it enough to read the label?

 

The label might merely read "catalyst", but sometimes brilliant minds overlook the obvious.

 

Gerrit

[Gerrit]

Can't give you the web page since I'm a newbie, but Antonietti et al give more information on their methodology (including their catalyst) in "New Journal of Chemistry" 2007, 31, 787-9.

Title: "Back in the black: hydrothermal carbonization of plant material as an efficient chemical process to treat the CO2 problem"

 

Gerrit

[Turtle]

WOW! Deal me in!

 

The name of the catalyst? They might have given it away. Check out the photo at the top of the article referred to above. Note the labelled plastic bottle on the work-bench. It is fitted with a squirt. Could that be it? Can anybody magnify it enough to read the label?

 

The label might merely read "catalyst", but sometimes brilliant minds overlook the obvious.

 

Gerrit

 

i zoomed in on both photos to look at the label; it just is blocky pixels at 200%. :hihi: good call on checking the background though. got me looking closer too; see in the photos the coil of tubing hanging from the ceiling? a dime to a dollar that is the relief-valve vent they added after the explosion. :P the coil is to give a condensing effect & then ...woops!...right out the wall they run the outlet. looking closer, the lady is actually touching the relief valve in both photos. last thing to attach and first to remove for a run.

 

is there a chemist in the house‽ chemist‽ I don't begin to know what are catalysts and what are not. i'm just the plumber. :)

[Turtle]

Can't give you the web page since I'm a newbie, but Antonietti et al give more information on their methodology (including their catalyst) in "New Journal of Chemistry" 2007, 31, 787-9.

Title: "Back in the black: hydrothermal carbonization of plant material as an efficient chemical process to treat the CO2 problem"

 

Gerrit

 

acknowledged. you can come back and edit the link into your post when you get the privilege. this is the neatest thing since button shoes!! did you read what the catalyst was yet? the only one i know for sure is platinum. :P you can copy & past a quote from the work into a post if you have a mind to. since button shoes i tell you! :hihi: :)

[Gerrit]

Here's an extract from "Back in the black":

 

A renaissance in such experiments was started with reports on the low temperature hydrothermal synthesis of carbon spheres (200 °C) using sugar or glucose as precursors.14,15 Recently, our group has found that the presence of metal ions can effectively accelerate the hydrothermal carbonization of starch, which shortens the reaction time to several hours and directs the synthesis towards various metal/carbon nanoarchitectures, such as Ag@carbon nanocables,16 carbon nanofibers17 and spheres.13,16 Iron ions and iron oxide nanoparticles were shown to effectively catalyze the hydrothermal carbonization of starch and rice grains under mild conditions (200 °C), and gave exciting nanostructures.18 It was also revealed that the presence of ternary components in complex biomass (such as orange peel or oak leaves) seriously alters decomposition schemes.19 Unexpectedly, an improvement in properties of the carbonaceous structures for certain applications was found, i.e. smaller structural size of carbon dispersions and porous networks, higher hydrophilicity of the surfaces, and higher capillarity.

For completeness, it must also be mentioned that, beyond coalification, the conversion of biomass under hydrothermal conditions is a widely examined process. These approaches aim for the recovery of liquid,20,21 or gaseous22,23 fuel intermediates (like glucose, 5-hydroxymethylfurfural, methane, hydrogen etc.) from biomass, while the solid residues were, up until now, mostly treated as undesirable side products.

However, the described acceleration of HTC for coalification by a factor of 106–109 under rather soft conditions, down to a scale of hours, also makes it a considerable, technically-attractive alternative for the sequestration of carbon from biomass on large and ultra-large scales. Finally, to summarize the outcome of the optimization trials, catalyzed HTC required only the heating of a biomass dispersion under weakly acidic conditions in a closed reaction vessel for 4–24 h to temperatures of around 200 °C. This is indeed an extremely simple, cheap and easily scalable process. Besides that, HTC has a number of other practical advantages. HTC inherently requires wet starting products or biomass, as effective dehydration only occurs in the presence of water, plus the final carbon can be easily filtered from the reaction solution. This way, complicated drying schemes and costly isolation procedures can be conceptually avoided. In addition, under acidic conditions and below 200 °C, most of the original carbon stays bound to the final structure. Carbon structures produced by this route—either for deposit or materials use—are therefore the most CO2-efficient.

Once activated, HTC is a spontaneous, exothermic process. It liberates up to a third of the combustion energy stored in the carbohydrate throughout dehydration (due to the high thermodynamic stability of water, but see ref. 5).

[malcolmf]

I see the article mentions a requirement of a catalyst, but it is never named? Do you know what it is?

 

Hi Turtle

 

Still following up references. A difficulty is that key papers, in which catalysts would be specified precisely, are in German.

 

One catalyst that has definitely been used is citric acid, no doubt for the "weakly acidic conditions" mentioned in Back in the black. That source mentions no other. A different source says there are two components, but not what number two is. However we can infer from Back in the black that it provides the metal ions.

 

So, the Earth will be saved by pressure cooking lemons with a bit of rust thrown in. Plus the occasional forest. :)

 

The usual definition of a catalyst is that it is not changed by the reaction. I hope that it is recoverable from the solution and does not contaminate the carbon product. Otherwise there might be acidification and metal toxicity issues if the product becomes topsoil.

 

M

[Gerrit]

Before we get too excited, what is a "biomass dispersion?"

 

From the article "Back to Black": "catalyzed HTC required only the heating of a biomass dispersion under weakly acidic conditions in a closed reaction vessel for 4–24 h to temperatures of around 200 °C."

 

Does this mean that any substance used in the HTC process must first be ground up and milled to an extremely fine - perhaps colloidal - state in order for the process to work? If so, this would probably entail a prohibitive amount of energy and machinery costs in the preparation process, at least in the case of woody products.

 

Gerrit

[Turtle]

Before we get too excited, what is a "biomass dispersion?"

 

From the article "Back to Black": "catalyzed HTC required only the heating of a biomass dispersion under weakly acidic conditions in a closed reaction vessel for 4–24 h to temperatures of around 200 °C."

 

Does this mean that any substance used in the HTC process must first be ground up and milled to an extremely fine - perhaps colloidal - state in order for the process to work? If so, this would probably entail a prohibitive amount of energy and machinery costs in the preparation process, at least in the case of woody products.

 

Gerrit

 

i think 'biomas dispersion' means mixed with water. No mechanical processing is required other than sizing the biomass material to fit into the reaction chamber is what I get from the article. Re-read the bits about the whole pinecone I quoted above. :D :rolleyes:

[Gerrit]

Catalysts:

From the "Back to the Black" article: "Iron ions and iron oxide nanoparticles were shown to effectively catalyze the hydrothermal carbonization of starch and rice grains.."

 

On the 'net, I see that there are companies out there who sell nanoparticles. But those particles are awfully small...I wonder if they can be recovered since I think they have magnetic properties...?

 

The other big catch in this business of setting up a pressure cooker for producing carbon, is that incident of the explosion...Once the process becomes exothermic and takes off on its own, what pressures do our vessel have to contain?

 

According to Antonetti, this process overall is much simpler technology than pyrolysis for gas production. Although he's not giving out enough information for me to go ahead and try something, I will keep my eyes peeled for further developments.

[Turtle]

Catalysts:

From the "Back to the Black" article: "Iron ions and iron oxide nanoparticles were shown to effectively catalyze the hydrothermal carbonization of starch and rice grains.."

 

On the 'net, I see that there are companies out there who sell nanoparticles. But those particles are awfully small...I wonder if they can be recovered since I think they have magnetic properties...?

 

The other big catch in this business of setting up a pressure cooker for producing carbon, is that incident of the explosion...Once the process becomes exothermic and takes off on its own, what pressures do our vessel have to contain?

 

According to Antonetti, this process overall is much simpler technology than pyrolysis for gas production. Although he's not giving out enough information for me to go ahead and try something, I will keep my eyes peeled for further developments.

 

Good stuff Geritt. Keep it comin'. :)

 

On the explosion factor, the photos in the article posted at post #1 are telling. First, the whole setup is clearly in a small isolated shed. Keep in mind this is experimental setup and a proven commercial unit ought be no more dangerous tha your hotwater tank for explosion.

 

Most importantly, is the pressure relief setup I described in earlier posts. Look at the coil of tubing in both photos that is attached to the vessel and hanging from the ceiling.

 

Understand that in another incarnation I was a plumber and I have installed & serviced hundreds of hotwater tanks in both commercial and residential settings. So it looks to me that they have 3/4" continuous copper pipe there, which is the standard pressure relief valve discharge pipe size for hotwater tanks of capacity to 52 gallons. While not clear in the photo, I suspect they have simply used an off the shelf relief valve for hot water tanks as well. ;)

 

Notice how everything equipment-wise looks all "scientificy'? Except the plumbing parts. I suspect they have gone not with calculations, but with the reasoning "if it's good enough for a 52 gallon hotwater tank, it ought to work for this little vessel.

 

That's all I got. :cup:

[Gerrit]

re: 200 degrees (Centigrade) and steam. I'm glad you know what you're doing. I just picked this up from the 'net.

 

"Superheated water is unstable and boils over rapidly when pressure is reduced. It can be extremely dangerous in the event of tank rupture. In case of rupture, water at 200 degrees centigrade will transform into water at 100 centigrade and a large volume of steam at one atmosphere of pressure. This transformation is so rapid that boiler explosions have frequently resulted in the the destruction of large buildings."

 

(Pressure cookers, like we use for food, only raise the temperature about 15 degrees (Centigrade) above boiling, generating about 15 pounds of pressure.)

 

Even though it's dangerous, I hope you can do something with this.

[Turtle]

re: 200 degrees (Centigrade) and steam. I'm glad you know what you're doing. I just picked this up from the 'net.

 

"Superheated water is unstable and boils over rapidly when pressure is reduced. It can be extremely dangerous in the event of tank rupture. In case of rupture, water at 200 degrees centigrade will transform into water at 100 centigrade and a large volume of steam at one atmosphere of pressure. This transformation is so rapid that boiler explosions have frequently resulted in the the destruction of large buildings."

 

(Pressure cookers, like we use for food, only raise the temperature about 15 degrees (Centigrade) above boiling, generating about 15 pounds of pressure.)

 

Even though it's dangerous, I hope you can do something with this.

 

Just to clarify, I didn't engineer any of the hotwater tank equipment, I just installed it according to the engineers' instructions.

 

For the pressure cooker in the kitchen, there is a hole with a weighted stopper that leaks steam out continuously in order to maintain the 15#, so that's not practical for hydrothermal carbonization because the water needs to stay in for the reaction.

 

The pressure relief valve is controlled by a calibrated spring, and I honestly don't recall ever seeing the limit on the hotwater tank relief valves. They are however engineered to vent the steam of a 52 gallon hotwater tank if it overheats. The tanks are steel with a porcelain liner. (To clarify, I am not suggesting that a hotwater tank can be used for a Hydrothermal Carbonization unit; just drawing a parallel in regard to pressure relief valves to prevent explosion.)

 

Finally, I do know that if the discharge orifices into and out of the relief valve are not large enough in cross sectional area (diameter of pipe), then even if the spring is properly calibrated the tank can't vent fast enough and may still explode. (I would run across tanks I was servicing where the installer had used 1/2" or 5/8" rather than 3/4" copper pipe for the relief to save money. they knew it was wrong because they had to use a reducer coupling to make the attachment to the valve housing.:cup: )

 

I don't know how to calculate how much water at what pressure & temp exerts what force. :cup: :clock:

[Turtle]

Here is a diagram of how I would contain the outflow from the pressure relief valve. Keep in mind it is not to scale. The volume and thickness of the reaction vessel, pressure relief valve trip-limit, relief discharge pipe diameter, volume of containment vessel and stack, must all be engineered to work together.

 

Essentially, when the pressure relief valve on the reaction vessel trips, the outflow is directed to the sealed containment vessel full of water. The steam pushes the water down in the containmnet vessel and up the large-bore stack. As long as the bottom of the stack remains submerged, the relief discharge is contained and isolated from the air. As the system cools, the water in the stack drops and the containment tank refills.

 

That's a wrap. :cup: :clock:

 

[Gerrit]

You wrote:

 

"For the pressure cooker in the kitchen, there is a hole with a weighted stopper that leaks steam out continuously in order to maintain the 15#, so that's not practical for hydrothermal carbonization because the water needs to stay in for the reaction."

 

I'm not sure if this loss of water matters. From "Back in the Black", "HTC inherently requires wet starting products or biomass, as effective dehydration only occurs in the presence of water..."

 

Water is essential at the beginning, but dehydration is the end goal. As long as there is still enough water left at the end to produce the quantity of steam required to pressurize the boiler, that should be enough.

 

Besides, how did the researchers control the temperature? After they heated the soup to 200 C. exothermic reactions take over. Of course some of this heat is absorbed and used within the material to change its chemical structure. But if the rest of the internal heat was kept inside, the pressure would keep building. To maintain a steady temperature/pressure at 200, they would have to let some steam out (thus the relief valve)...or else have the whole thing bathed in water and hooked up to a radiator to keep it cool?

 

This is one aspect not addressed in the article: how much heat is a by-product of the exothermic carbonization process. Is it enough for a larger unit to heat water in a storage tank to help heat a house or greenhouse, as well as carbonize biomass?