Hydrothermal carbonization (HTC)

[Gerrit]

The reason I was interested n excess energy, was that I was hoping that it would provide another product to make the whole process that much more 'useful.'

 

Whatever, there is still the question of input energy to get the whole thing started. The soup has to reach 200 C before exothermy happens. Maybe he feels that after the first batch is made, that the energy/steam remaining in this first boiler could then be transferred to a second boiler, to get it up to speed, instead of merely allowing that energy to dissipate into the atmosphere?

 

Thus a two-boiler system would be optimum. One cooking and one being filled for next batch.

[malcolmf]

The reason I was interested n excess energy, was that I was hoping that it would provide another product to make the whole process that much more 'useful.'

The process heat is always useful, but you only get copious amounts from carbohydrate-rich feedstocks. But beware of by-products. They may define the best early niche applications but they can take your eye off the prize, which is 100% recovery of carbon followed by permanent sequestration. This reduces greenhouse gases by more than ANY bioenergy application. What the new information does is alter my view of the best niches and the prospects for farming biomass. It makes the food processing chain (with its mountain of waste) a potential major user, and algae and the grass family look rather attractive feedstocks.

Whatever, there is still the question of input energy to get the whole thing started.

No different to pyrolysis. You can either burn feedstock (like traditional charcoal making) or an external fuel (like modern charcoal making and more efficient).

The soup has to reach 200 C before exothermy happens.

Pyrolysis has to reach 400. This is no big deal. An electric oven does not need much to reach 200 and an autoclave (on which this technology might be based) is more efficient than an oven.

Maybe he feels that after the first batch is made, that the energy/steam remaining in this first boiler could then be transferred to a second boiler, to get it up to speed, instead of merely allowing that energy to dissipate into the atmosphere? Thus a two-boiler system would be optimum. One cooking and one being filled for next batch.

Yes, that's always an option and it increases the speed at which you can process feedstock. Also, I don't see heat dissipation as a problem. Applications based on Turtle's heat exchanger and a well-insulated cooker would dissipate usefully, e.g. to a process such as drying, a house or a polytunnel. I see the kit as having a standard fitting to which you could plumb in any heating circuit.

 

Where's our resident engineer?

 

M

[Gerrit]

You wrote: "An electric oven does not need much to reach 200 C"

 

The oven is quick, because it's just heating air. But if it had to bring 10,000 liters of water to a boil, and then double that to bring the soup to 200 C, you're talking about a pile of input energy/heat. Unless the exothermic heat produced by the carbonization process is directed immediately to heating the next batch, the expense could easily become prohibitive.

[palmtreepathos]

I find this all very interesting as well, and will be digging out my old pressure cooker since he makes it sound so easy to make, and less polluting for the air than my current method of making charcoal. Maybe someday we will heat the house with a boiler that also serves to take your organic trash and make char for the garden, COOL!

 

INTERVIEWER:What, then, is so special about your

process?

ANTONIETTI: What’s special about it is that it goes

back to the basics, although it still incorporates

modern methods. Hydrothermal carbonization really

just means boiling off the water, which makes

the process so easy that it can even be done in a

non-chemical environment, anywhere, even in the

agricultural regions of the Third World.

 

http://www.mpg.de/english//illustrationsDocumentation/multimedia/mpResearch/2007/heft/pdf23.pdf

[Turtle]

I find this all very interesting as well, and will be digging out my old pressure cooker since he makes it sound so easy to make, and less polluting for the air than my current method of making charcoal. Maybe someday we will heat the house with a boiler that also serves to take your organic trash and make char for the garden, COOL!

 

 

I recommend not trying this with a pressure cooker!! They are not, imo, capable of containing the reaction when it goes exothermic. Using a home-use pressure cooker for hydrothermal carbonization is just asking for an explosion.

 

Yes, that's always an option and it increases the speed at which you can process feedstock. Also, I don't see heat dissipation as a problem. Applications based on Turtle's heat exchanger and a well-insulated cooker would dissipate usefully, e.g. to a process such as drying, a house or a polytunnel. I see the kit as having a standard fitting to which you could plumb in any heating circuit.

 

Where's our resident engineer?

 

Again to clarify, I am not an engineer. That said, I agree the proper plumbing can dissipate heat, however it sounds like the 200º C (376ºF) must be sustained for a period and so it is critical the vessel is designed to maintain that temp and contain the high pressure.

 

The setup I described was intended more or less to prevent explosion. I think what is called for is some calculations of x amount of water @ yº temp and in a vessel of z volume produces a pressure p; this is beyond my capability. :cup: ;)

[Gerrit]

Turtle is right. Do not try this with a pressure cooker! They are generally rated for up to only 15 pounds of steam which is only a fraction of what you need to reach 200 C.

 

If we are going to do our own experimentation, maybe we should we looking on the web for used university lab equipment for sale? What about old boilers from steam-heat furnaces?? If anybody finds any adverts for such, please post.

[Gerrit]

Just checking an old steam engineers handbook to find that steam at 400 F, which is pretty close to 200 C, has a pressure of 250 lbs./sq.in.

 

My high pressure sprayer (air mist) actually pumps at just over 200lb./sq.in., and it just uses pipe to conduct the spray to the nozzles...

 

Whatever, I was checking stovetop autoclaves on the 'net (the cheapest boiler-type thing I could find) and they seem rated at only about 160 C.

[Fukudairafarm]

The name of the catalyst? They might have given it away. Check out the photo at the top of the article referred to above.

Gerrit

 

You don't have to look at the label, just click on the movie link at the bottom right of the last page of the PDF. You will be brought to the Max Planck Society homepage. Then you can watch the quicktime movie, where they say water is added, with a citric acid catalyst, then it is heated for 12 hours at 180 degrees C.

However, they don't give us the pressure. They only mention it is heated in an autoclave. I wonder if a pressure cooker would work?

[Gerrit]

Thanks for that tip to watch the video! It looks simple doesn't it? A dollop of lemonade with a dash of iron ions heated up to 180C...and presto - charcoal!

 

But there is a catch - the high pressure boiler required. (Go back to message #33 in this thread to see a letter I posted there from the researcher.) At 180C, the steam pressure in any boiler will build up to about 145 psi. Unfortunately, steam pressure food cookers are only rated for about 15 psi. To get the higher pressures, you need at least a stovetop autoclave.

[Gerrit]

For the do-it-yourselfer to experiment with hydrothermal carbonization, I wonder if an old hydraulic cylinder would be the ideal boiler? They are generally designed for 3,000 psi, which is way more than needed...

[mervenvs]

Hi there,

 

I would like to quote this for information:

 

The reaction was carried out in a nonstirred, 60 mL capacity Teflon-lined stainless steel autoclave, which was put in a programmable oven. In a typical procedure, 5-20 g of biomass was dispersed in 40 mL of deionized water. Ten milligrams of citric acid was added to ensure comparable acidic carbonization conditions. The autoclave was sealed and tempered at 180-250 °C (default 200 °C) for 16 h and then allowed to cool to roomtemperature. The products were filtered off, washed several times with distilled water and absolute ethanol, and finally dried in a vacuum at 60 °Cfor4h.

 

Warning: we seriously caution against repeating the experiments without additional safety measures using too high concentrations of too easily carbonizable material, as the reaction is exothermic

source: Titirici et al. Chem. Mater. 2007, 19, 4205

 

The citric acid is just used to catalyse the reaction in the beginning. Then acid is formed so the reaction is autocatalysed (this is basically a dehydration). This is just to avoid a induction time that would cost more energy that what is needed to produce the minute quantity of citric acid needed (you can press a slice of lemon to provide citric acid).

 

I have access to scientific litterature. Any question is welcome.

[mervenvs]

ooops, looks like this thread was a bit dead

[Getting A Life]

I have questions

 

With a pressure valve rated at required psi, and a reaction vessel rated above this, and a lemon tree in the yard for the odd squeeze, this would work safely?

 

What ratio water:biomass for vegetable byproduct (brassicas, herbs, toms, peppers, cucurbits etc)?

 

What temperature for creating a garden char product with resins etc intact?

 

I could put excess steam into a reservoir of water in a greenhouse each evening with such a system.

 

Or is it so dangerous one should not have such a unit in a suburb. I've seen steam boiler explosions, nasty.