Hydrothermal carbonization (HTC)

[Gerrit]

Here is a diagram of how I would contain the outflow from the pressure relief valve. Keep in mind it is not to scale.

 

It looks neat.

 

What's the reason for not streaming the steam directly into the water body? Wouldn't the steam be cooled/condensed virtually instantly as the water absorbs its heat? Would that be too turbulent an interface?

[Turtle]

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..."

 

acknowledged. again, my remarks were meant to clarify the pressure relief mechanics of the pressure cooker someone mentioned; i.e. how it's done.

 

 

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?

 

i agree. As we see no evidence of cooling apparatus in our only two photos of the setup. we are still guessing. :clock:

 

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?

 

Good thinking! In the setup I drew & described, the containment vessel could also include a heat exchanger in the form of copper coils of pipe connected to the home hotwater tank. Then again, how often would you use the setup? Are we now talking alternative energy source? see ' wood gas ' ? :cup: :hihi: :cup:

[Gerrit]

Turtle wrote:

"Good thinking! In the setup I drew & described, the containment vessel could also include a heat exchanger in the form of copper coils of pipe connected to the home hotwater tank. Then again, how often would you use the setup?"

 

I would see it hooked up to a larger water storage tank in the basement that would then be drawn upon as needed to heat the house or a greenhouse in winter.

 

Some people heat their houses with wood from an outside furnace. Of course, the high pressure set-up for carbonization would be much more expensive than a wood furnace, and what is the value of the carbon char produced anyway?? Will people pay carbon credits to a home-owner? What is the value of the carbonized material for soil improvement? Too many questions...

[Turtle]

I would see it hooked up to a larger water storage tank in the basement that would then be drawn upon as needed to heat the house or a greenhouse in winter.

 

Some people heat their houses with wood from an outside furnace. Of course, the high pressure set-up for carbonization would be much more expensive than a wood furnace, and what is the value of the carbon char produced anyway?? Will people pay carbon credits to a home-owner? What is the value of the carbonized material for soil improvement? Too many questions...

 

No worries; all we have is time.

 

in thinking over my proposed setup along with your observations, i realized that the relief system presumes its use only in a situation where no relief results in an explosion. that is all well and good, and my system accomplishes its purpose.

 

now however, because you mentioned cooling, and the reaction is exothermic, then we can cool and control pressure in the reaction vessel while utilizing the heat as you suggest. we simply wrap the reaction vessel itself in copper tubing which is connected to whatever heat storage/use mechanism you care.

 

this would be a thermostatically and pressure controlled active heat exchanger, which is to say if the pressure or temperature in the reaction vessel rises above a set limit, a pump is turned on and coolant is pumped through the coils around the reactor until the the temp and/or pressure drops to nominal and then the pump stops.

 

the value of the carbon in this case seems in particular that it is nano-structured. yes, no? bucky ball stuff. carbon nano-tubes & buckminsterfulerenes...the new black gold. the value of a thing is what you give it. :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.

 

It looks neat.

 

What's the reason for not streaming the steam directly into the water body? Wouldn't the steam be cooled/condensed virtually instantly as the water absorbs its heat? Would that be too turbulent an interface?

 

Sorry; I missed this question earlier. No particular reason when I drew it I guess. I suppose I wasn't considering any mixing and thinking only in terms of the pressure reactions. The idea is more or less to prevent an explosion and/or release of reactants to the air. :rotfl: ;)

[Gerrit]

Turtle,

 

I think it's time we clarified a few details about the potential of this process with the researchers, before we take this too much further. I've drafted an e-mail to them as follows. Please give me your input.

 

Dear Mr. Markus Antonietti,

 

As members of the Petra Terra listserve of the Hypography.com Science Forum, we are excited by your work with carbonizing biomass for the purposes of building terra preta soils. We have read several articles on your work with the hydrothermal carbonization of plant material. After some discussion, we have a few questions for clarification purposes:

 

1. Types of materials that can be used: you mention that your process focusses on annual fast-growing plant materials. Thus, should we assume that woody or lignified plant materials are too dense for use in the 200 degree C steam pressure vessel? If they can be used, to what extent do they have to be ground/milled?

 

2. What is the cost of the catalysts per unit of output as used in the process? In the article "Back to Black", you mention catalysts of iron ions and iron oxide nanoparticles. Elsewhere there is mention of a PH conditioner - citric acid.

 

3. It takes a certain amount of heat to get the process started. At a certain point, an exothermic reaction takes over. What is the net energy output/dry weight of biomass?

 

Any suggestions for more questions before I send this off?

[Turtle]

Turtle,

 

I think it's time we clarified a few details about the potential of this process with the researchers, before we take this too much further. I've drafted an e-mail to them as follows. Please give me your input.

 

Dear Mr. Markus Antonietti,

 

As members of the Petra Terra listserve of the Hypography.com Science Forum, we are excited by your work with carbonizing biomass for the purposes of building terra preta soils. We have read several articles on your work with the hydrothermal carbonization of plant material. After some discussion, we have a few questions for clarification purposes:

 

1. Types of materials that can be used: you mention that your process focusses on annual fast-growing plant materials. Thus, should we assume that woody or lignified plant materials are too dense for use in the 200 degree C steam pressure vessel? If they can be used, to what extent do they have to be ground/milled?

 

2. What is the cost of the catalysts per unit of output as used in the process? In the article "Back to Black", you mention catalysts of iron ions and iron oxide nanoparticles. Elsewhere there is mention of a PH conditioner - citric acid.

 

3. It takes a certain amount of heat to get the process started. At a certain point, an exothermic reaction takes over. What is the net energy output/dry weight of biomass?

 

Any suggestions for more questions before I send this off?

 

Looks like a fine introductory letter. Mail away. :Glasses:

[malcolmf]

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

I noticed the same thing and worried the same worry. However some of the source text suggests that the process works on intact biomass and a photo on the Max Planck website shows a catalyst being added to a vessel containing solid biomass. I suppose it might be a blender rather than a cooker. To be investigated.

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.

I doubt that it is problematic even if it is necessary. After all, wood is ground and pelleted, requiring relatively little energy and still producing an economical fuel; coal is pulverised for burning in a power plant, ditto. And there would be copious energy from preceding batches if this were an ongoing process.

 

M

[malcolmf]

Dear Mr. Markus Antonietti

 

I hope you have not sent this off yet. Antonietti is a German academic. Some German academics are sticklers for proper titles. If he is "Professor Doctor", or whatever, he may not take kindly to being addressed on a particular field by a title less than his status in that field, dismissing the sender as either insulting or not worthy of a response. Find out first. It should be in Back in the black.

 

Also that should be Terra Preta not Petra Terra, who is probably somebody's girlfriend :)

M

[malcolmf]

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?

 

It is addressed in Back in the black, if indirectly. The chemical reactions must in theory release one third of the energy in the biomass. This calorific value is often measured as energy per unit weight. Materials vary. Straw, for example, contains 15 GJ/t gross or 12.8 GJ/t net. I think we can use the gross (or Higher Heating Value) figure because the energy in any vapourised water will be recovered over time by natural or designed condensation, as long as the system remains closed.

 

So the by-product energy from straw would be 5 GJ/t. Some of that would be used to run the process. Being pessimistic, lets say 3 GJ/t is left over. 3 GJ would replace a 2kW (output) greenhouse heater for slightly over 415 hours, or about 1/25th of the annual space and water heating of an average house in the UK.

 

You can start to draw practical conclusions from this. For example, the waste from a garden could probably not do much except heat a small greenhouse, but the waste from a farm could do a lot by way of heating buildings, drying crops, and heating polytunnels. The most fitting form of heating would seem to be underground storage and circulation. In temperate climates like northern Europe HTC-heated polytunnels might create a serious carbon-negative low-miles alternative to the import of exotic fruit and vegetables.

 

And that is before we figure out what the best output is: the so-called topsoil (I wonder how good it is) from 5 hours cooking or the bio-coal from 12 hours. From a global warming viewpoint the topsoil would reduce more carbon, and sequester it permanently. However the bio-coal might make up a shortfall in energy for a particular application.

 

Thoughts?

 

M

[Gerrit]

Is this even better than hydrothermal carbonization? It's faster...

 

Flash Carbonization™ process

 

Research at the University of Hawaii (UH) has led to the discovery of a new Flash Carbonization™ process that quickly and efficiently produces biocarbon (i.e., charcoal) from biomass. This process involves the ignition of a flash fire at elevated pressure in a packed bed of biomass. Because of the elevated pressure, the fire quickly spreads through the bed, triggering the transformation of biomass to biocarbon. Fixed-carbon yields of up to 100% of the theoretical limit can be achieved in as little as 20 or 30 minutes. (By contrast, conventional charcoal-making technologies typically produce charcoal with carbon yields of much less than 80% of the theoretical limit and take from 8 hours to several days.) Feedstocks have included woods (e.g., leucaena, eucalyptus, and oak), agricultural byproducts (e.g., macadamia nutshells, corncobs, and pineapple chop), wet green wastes (e.g., wood sawdust and Christmas tree chips), various invasive species (e.g., strawberry guava), and synthetic materials (e.g., shredded automobile tires). Results of these tests are described in a series of technical, peer-reviewed, archival journals paper that can be obtained by request to Prof. M.J. Antal.

 

We are now testing a commercial-scale, stand-alone (off-the-grid) Flash Carbonization™ Demonstration Reactor ("Demo Reactor") on campus (see photos below). The first successful test occurred on 24 November 2006. A canister full of corn cobs was carbonized in less than 30 min. This test proved that the Flash Carbonization™ process can be scaled-up to commercial size.

 

Recently HNEI received a two-year $215,000 research grant from the Consortium on Plant Biotechnology Research (CPBR) for "Flash Carbonization™ Catalytic Afterburner Development." The CPBR funding will enable us to make progress towards the elimination of smoke and tar from the reactor's effluent. We are also initiating studies of the use of the Flash Carbonization™ process for the disposal of waste tires.

[Gerrit]

According to Dr. Antanl from Hawaii U.:

 

"Our Flash Carbonization process takes minutes (not hours) and

realizes the theoretical yield of carbon from many feedstocks with no

catalysts. Also, as a result of the findings of one of my recent graduate

students (Sam Wade), we can engineer a Flash Carbonization reactor so that

there is absolutely no danger of explosions. This is why our State Boiler

Inspector has given us a permit to operate our Demonstration Reactor on

campus."

[malcolmf]

Is this even better than hydrothermal carbonization? It's faster...

 

Flash Carbonization™ process

 

You'll find another link in the list of charcoal links that I posted to the original forum and then the charcoal-making subforum.

 

FC's advantages are speed and carbon extraction efficiency. However it is hi-tech and patented, which seem to limit it to high added value applications, and thus make it less likely to spread as far as having an impact on climate. Like HTC, there is no data on how suitable its product is for the agri-char approach to carbon sequestration. No good if the porosity collapses due to the pressure, or the residues that encourage micro-organisms are destroyed, for example.

 

The main difference between all pyrolysis methods and HTC is in the impact of moisture (in biomass and ambient) on their efficiency. Water is the basis of HTC, whereas it makes pyrolysis less productive, very much less when using fresh, undried material. You can use HTC at maximum efficiency direct from the harvest. Don't underestimate this parameter.

 

M

[Gerrit]

Malcolm,

 

I like the idea of HTC too as to its product and its simplicity. But at this point, we have too many questions: how finely divided the feed stock has to be, the filtration of the product is not necessarily an easy process and what about the catalysts - being ions and nanoparticles, it is doubtful that they are recoverable.

 

Maybe we just have to be patient...?

[malcolmf]

Malcolm,

 

... at this point, we have too many questions: how finely divided the feed stock has to be, the filtration of the product is not necessarily an easy process and what about the catalysts - being ions and nanoparticles, it is doubtful that they are recoverable.

 

Hardly killer questions, Gerrit. Dispersion and filtration are trivial processes compared to most in modern bioenergy. I've checked on the catalysts:

• Assuming that iron will suffice for the metal ions (as in the Max Planck experiments), iron plays a major role in the production of plant chlorophyll and in several enzyme systems. Its absence produces the plant disease called chlorosis. A first search finds no mention of iron overdose in soil. So in practice it might be better NOT to recover iron from HTC topsoil production; indeed, the process might be particularly applicable to reclaiming chlorotic soils.
   
  
• Citric acid occurs naturally as a fundamental part of the Krebs cycle, the fuel delivery mechanism of living cells. You are suffused with it! As such it is environmentally benign, although it may be beneficial as a nutrient to micro-organisms. One potential drawback is that it can reduce the availability of metals (like iron) to plants, depending on soil pH, by the process known as chelation. However I assume this effect is transient because citric acid is quickly mineralised in soil.
  

 

The big unknown as far as I am concerned is simply whether HTC topsoil is any good. Is it terra preta nova? How does it compare with the productivity of ancient terra preta and modern char-amended soil as measured by nutrient productivity (via both cation exchange capacity and nutrient retention), water retention, N2O emission reduction, and micro-ecosystem production? If it fails there, it is nothing but another (albeit efficient) biofuel production technology. If it is near equal or better ;)

 

M

[Gerrit]

Dr. Antonietti has answered my questions (below). Gerrit

 

 

Dear Gerald,

 

1) It works with all the biomass, but at different conditions. Lignified cellulose relies on "melting" (it is a plastified melting...) which occurs for pure cellulose beads at around 215 °C, it is a slight increase of conditions.

Mixed with other stuff it occurs and around 190 °C, so branches vanish completely in the lower range. This depends on "purity". We work with 2 cm pieces max. with only little loss in efficiency. It is like boiling vegetable soup.

 

2) It depends what you want. For "soil applications", you prefer a "hydrophilic coal", and you need not catalyst at all, only weakly acidic conditions.

Fe, Cu, and Ag are only needed when you do "engineering carbons", i.e. with much higher structural density. But iron is not a problem: 4 % of the earth crust is made of ironoxides, and any red soul is full of it. Sounds maybe strange, but red soil works perfect as a catalyst. No cost, no removal...

 

3) Talking glucose, starch, and saccharides, this is easy: 70 - 80 % of the energy stored in the plant goes into the carbon, about 20 - 30 % are liberated in the process. This is really a lot of heat: If you treat 1 kg of sugar, you get about 500 g of coal, but energy as you would have 200 g of the sugar! Close to a shell...

 

Biomass is more complex, no energy again from fats, amino acids, and lignin. This gives a factor which can reduce energy gain to 5 - 10 %, i.e. the process is essentially for free, but not more.

 

Thanks, indeed, for the interest.

Markus Antonietti

 

Gerald Van Koeverden schrieb:

Dear Dr. Markus Antonietti,

 

As members of the Petra Terra listserve of the Hypography.com Science Forum, we are excited by your research work in carbonizing biomass for the purposes of building terra preta soils. We have read several articles on your work with the hydrothermal carbonization of plant material. After some discussion, we have a few questions for clarification purposes:

 

1. Types of materials that can be used: you mention that your process focusses on annual fast-growing plant materials. Thus, should we assume that woody or lignified plant materials are too dense for use in the 200 degree C steam pressure vessel? If they can be used, to what extent do they have to be ground/milled?

 

2. The catalysts: What is the cost of the catalysts per unit of output as used in the process? In the article "Back to Black", you mention catalysts of iron ions and iron oxide nanoparticles. Is it practical to recover them for re-use?

 

3. Net energy output: It takes a certain amount of heat to get the process started. At a certain point, an exothermic reaction takes over. What is the net energy output/dry weight of biomass?

Looking forward to your kind assistance. I will post your answers on the Petra Terra list-serve.

 

Gerald van Koeverden

[malcolmf]

Excellent work Gerrit.

"Boiling vegetable soup". I like that!

Worries over dispersion and filtration disappear.

Excess energy seems to come only from such feedstocks as fruit, roots, leaves, grasses etc, not from wood or animal remains.

M