[Turtle]

Originally Posted by 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

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.

[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]

Originally Posted by 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.

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.

[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]

Originally Posted by 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.

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. )

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

[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.

[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?

[Gerrit]

[quote=Turtle;182638]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]

Originally Posted by 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..."

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

Originally Posted by Gerrit

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.

Originally Posted by Gerrit

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 ' ?

[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...