sCO2 is also used for the production of aerogel: https://en.m.wikipedia.org/wiki/Aerogel
Supercritical CO2 is heavy like a liquid, with weird and useful properties
41–50 of 57 posts
Re: Supercritical CO2 is heavy like a liquid, with weird and useful properties
#42"GE has built a prototype which is small enough to fit on a desktop" - The linked page (https://tinyurl.com/y2s9z69d) claims 10 MW output - This is several orders of magnitude "north" from the reality (~ 15 kW).
Re: Supercritical CO2 is heavy like a liquid, with weird and useful properties
#43Earlier quoted context omitted.
Let's guess. I'm going to say they are dissolving the 'precursors' into the co2, pumping it through the bed of particles with sufficient vigor to achieve 'fluidized' [1] state. As the supercritical co2 rises through the bed, the particles are dumping heat into it, ultimately flashing to vapor and leaving the solute (or at least the metallic part of it) behind as a thin film on the particle that did the trick. This of…
Almost! Except for the flashing CO2 to vapor, I actually just had a filter at the top to keep particles from flying out but the reactor itself was at 5000PSI and I just used a backpressure regulator for the exhaust stream which was very little since basically every byproduct was a gas. But in backstory, I invented a process, particle supercricial fluid deposition (UMass Amherst previously demonstrated deposition onto…
Thank you very much!
Exciting read!
Re: Supercritical CO2 is heavy like a liquid, with weird and useful properties
#44Some molten salt reactor designs were planned first with helium turbomachinery and later with supercritical CO2. Also GE tried to sell gas turbines for ship propulsion. You get back some efficiency with a CO2 turbine running with the waste heat. Ship owners still like their diesels. Really long time between overhauls.
> Also GE tried to sell gas turbines for ship propulsion. Pretty common for warships though, or at least that's my understanding. The Arleigh Burke class [0] is powered by GE gas turbines, for instance. Though the requirements list for "large surface combatant engine" and "huge cargo vessel engine" are probably more than a bit different. 0: https://en.wikipedia.org/wiki/Arleigh_Burke-class_destroyer
Yes. They pay little for fuel. Also afaik they do not use the waste heat. Though probably with the logistics train to some places the fuel can probably be expensive at times.
There used to be passenger ships with turbines too. They changed the engines to regular diesels at some point. https://en.m.wikipedia.org/wiki/GTS_Finnjet
Re: Supercritical CO2 is heavy like a liquid, with weird and useful properties
#45I guess supercritical CO2 can be a decent refrigerant as well. https://www.greenbuildingadvisor.com/article/a-heat-pump-usi...
AFAIU it's quite common in supermarket/warehouse refrigerators and freezers. Apparently upfront cost is slightly higher, but the refrigerant is cheap and there's no risk the next iteration of the F gas legislation will make your investments a dead end. And of course the environment friendliness is important to businesses that are concerned about their image.
Re: Supercritical CO2 is heavy like a liquid, with weird and useful properties
#46Earlier quoted context omitted.
> Also GE tried to sell gas turbines for ship propulsion. Pretty common for warships though, or at least that's my understanding. The Arleigh Burke class [0] is powered by GE gas turbines, for instance. Though the requirements list for "large surface combatant engine" and "huge cargo vessel engine" are probably more than a bit different. 0: https://en.wikipedia.org/wiki/Arleigh_Burke-class_destroyer
Yes. They pay little for fuel. Also afaik they do not use the waste heat. Though probably with the logistics train to some places the fuel can probably be expensive at times. There used to be passenger ships with turbines too. They changed the engines to regular diesels at some point. https://en.m.wikipedia.org/wiki/GTS_Finnjet
I think they actually do reuse the waste heat in a way, not via steam, but by being recuperated.
Re: Supercritical CO2 is heavy like a liquid, with weird and useful properties
#47Earlier quoted context omitted.
Does cavitation depend on temperature in like submarines too?
CO2 is super weird. In a CO2 tank it's actually two-phase, CO2 gas and liquid in a steady state equilibrium that is exclusively a function of the temperature. Since the outlet was connected to the HPLC pump inlet, if the temperature between the tank and the pump head was exactly equal, when the pump piston draws liquid in it every so slightly reduces the pressure, which results in the liquid CO2 boiling inside the pu…
Excellent use of the HPLC pump, we used to order them by the pallet.
Here's the phase diagram:
https://en.wikipedia.org/wiki/File:Carbon_dioxide_pressure-t...
I'm no engineer, but I like to work with engineers that are good at not just established "engines" but imaginary ones too.
I always thought any engineer should be able to understand this well-established graph just by looking at it, regardless of whether they had any ChE background.
Engineers already exposed to material phase behavior sometimes still take a little while, but there's not much there, it's a pretty straightforward graph.
Studying it alone should bring understanding, not of the full implications of the dynamic physico-chemical properties of course, just the states of matter that exist under the conditions indicated by the data.
Some engineers can never get this, I don't get that.
While I would prefer an engineer with an appreciation for what it takes to turn the imagination of some PhDs into apparatus capable of creating drawings like this, using commercially available components when possible, based primarily on drawings like this.
I'm no capitalist without other people's money (I personally owned two of the automated positive-displacement high-pressure [syringe] pumps), but a good capitalist to work with would have enough imagination for an intuitive understanding of the leverage used to assemble advanced equipment into money-making machines, when the majority of operators must accept the high-dollar components as unrecoverable costs.
Re: Supercritical CO2 is heavy like a liquid, with weird and useful properties
#48Earlier quoted context omitted.
CO2 is super weird. In a CO2 tank it's actually two-phase, CO2 gas and liquid in a steady state equilibrium that is exclusively a function of the temperature. Since the outlet was connected to the HPLC pump inlet, if the temperature between the tank and the pump head was exactly equal, when the pump piston draws liquid in it every so slightly reduces the pressure, which results in the liquid CO2 boiling inside the pu…
Excellent use of the HPLC pump, we used to order them by the pallet. Here's the phase diagram: https://en.wikipedia.org/wiki/File:Carbon_dioxide_pressure-t... I'm no engineer, but I like to work with engineers that are good at not just established "engines" but imaginary ones too. I always thought any engineer should be able to understand this well-established graph just by looking at it, regardless of whether they h…
I sort of agree, but I think you're too harsh. Having taught phase diagrams to freshmen, very smart freshmen, as with everything else it comes down to familiarity and practice. I tend not to look down on people for not knowing stuff they're not familiar with, I'm sure they could all get it with someone who can actually guide them through it.
But I do appreciate a simple, inexpensive design of course. But they're so hard for people to make if they don't understand the deep details of everything in the system, and once the knowledge is split between two brains then it's a lot harder to spot inconsistencies. But I also can hardly blame people for throwing in the towel on deeply researching the sheer vastness of the McMaster, Swagelok, and Digikey catalogs. Much less ASTM standards or the ASM handbook.
I work on building a lot of surprisingly easy things like electromagnets and battery charging circuits and low noise filters and precision temperature controllers and such like that in-house because it's shocking how bad and expensive stuff made commercially usually is. Just yesterday I was replacing a flow sensor in a water pump to water cool a vibrating scanning magnetometer my office mate designed. It's a fun line of work. I also do stuff on the side as a consultant along these lines to scratch the "let's make something people can use in industry" itch (http://neltnerlabs.com/).
But my biggest pipe dream for the past 9 years has been using AI tools to close the loop around synthesis and testing and predicting properties for heterogeneous catalysts. Equipment is a key part of that dream, sadly Google was uninterested (no ads?) and I've only ever found a handful of companies working on it all of which don't quite seem to get just how big a deal it is almost certain to be. At least the national labs are catching on.
Re: Supercritical CO2 is heavy like a liquid, with weird and useful properties
#49Supercritical liquids are generally weird. H2O, for example, changes from being a polar solvent to a nonpolar solvent -- you can dissolve oil in supercritical water, and even burn it if you have a source of oxygen. It's also more corrosive -- which is relevant if you're considering using supercritical water in a nuclear reactor.
> even burn it if you have a source of oxygen
How does that work? What are the combustion products? The closest reference I could find is this, https://science.nasa.gov/science-news/science-at-nasa/2014/1... , which seems to be talking about something else.
Re: Supercritical CO2 is heavy like a liquid, with weird and useful properties
#50Earlier quoted context omitted.
Excellent use of the HPLC pump, we used to order them by the pallet. Here's the phase diagram: https://en.wikipedia.org/wiki/File:Carbon_dioxide_pressure-t... I'm no engineer, but I like to work with engineers that are good at not just established "engines" but imaginary ones too. I always thought any engineer should be able to understand this well-established graph just by looking at it, regardless of whether they h…
I sort of agree, but I think you're too harsh. Having taught phase diagrams to freshmen, very smart freshmen, as with everything else it comes down to familiarity and practice. I tend not to look down on people for not knowing stuff they're not familiar with, I'm sure they could all get it with someone who can actually guide them through it. But I do appreciate a simple, inexpensive design of course. But they're so h…
> but I think you're too harsh.
What I found when I took thermo which is where you learn this stuff. Nothing really prepares you for the basic concepts before hand. So it's a steep hill to climb. I think some students get through it via rote memorization. Which means they don't actually understand it. I had to retake the first semester because I got a C-. Which was likely for the best.
I also think that thermo is somehow very deeply connected to how the universe actually works. And the next step down is a doozy. So it's difficult to explain it in terms of something familiar.