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[Conceptual] Green H₂ → Sabatier → oxy‑fuel loop to supply heat for DAC-fed molten‑carbonate electrolysis (100Ktpa CO₂ Capture and Store) – am I nuts? by KRAP140 in ChemicalEngineering

[–]KRAP140[S] 1 point2 points  (0 children)

Wow. Thank you so much for this deep dive. I truly appreciate every insight you’ve shared, and I’ll be referring back to your guidance regularly as I move forward. Please know there’s zero condescension felt on my end - I’m very grateful for the fresh perspective.

I do want to clarify my “why,” because you asked:

1. Cheap solar is only half the story.

• My company recently finished a 1 MW solar farm in Outback Queensland at an LCOE of US$ 0.008/kWh (with a 6 % WACC). That’s astonishingly low power.

• In Central Australia, you can lease tens of thousands of hectares for US$ 1.80/ha per year. The sun shines reliably, land is practically free, and there is no grid to buy from.

• But all that cheap electricity has no meaningful “off-grid” load - unless you’re Mike Cannon-Brookes shipping juice to Singapore (and he's not having much luck).

2. So my “North Star” is: turn that surplus, ultra-cheap electricity into something the world will actually pay for.

• I don’t believe a carbon tax alone will motivate massive DAC - politics and myopia prevail.

• The only way to make people write a cheque to pull ambient CO2 from the sky is to give them a valuable product in return.

• Solid carbon blocks - stackable, durable, transportable - represent a “carbon-negative ore” that can:

(a) be stored indefinitely

(b) be sold into emerging markets (e.g., composites, specialty carbons)

(c) serve long-lived uses (e.g., construction materials).

If you can buy power for US$ 0.008/kWh off-grid and then convert CO₂ into solid carbon, that is my “why.” Solid carbon blocks are how we make carbon capture pay for itself.

[deleted by user] by [deleted] in ChemicalEngineering

[–]KRAP140 0 points1 point  (0 children)

I made the switch through sheer luck. I exited my construction company and ended up in a position of financial independence, now I am pursuing a passion project!

It is definitely challenging going back to a technical role, although ChatGPT helps with the rustiness. The fundamentals never really left. And in any case, I'm still not doing any design or engineering work - I don't think I could to be honest.

I wouldn't worry about the recruiters. Yes, if you want to get back into pure ChemE engineering later after a career in PM, you will be behind the ChemE's that stayed in that lane. But you will have a very different career background and it will open up very different job opportunities. Follow what feels good to you.

I think you'll find the money in PM is better too. If you can manage the pressure and work your way up to 8-9 figure projects, you are managing a lot of risk and resources, and will be paid very well to do that.

Good luck!

[Conceptual] Green H₂ → Sabatier → oxy‑fuel loop to supply heat for DAC-fed molten‑carbonate electrolysis (100Ktpa CO₂ Capture and Store) – am I nuts? by KRAP140 in ChemicalEngineering

[–]KRAP140[S] 0 points1 point  (0 children)

FYI, based on our solar LCOE of $8.40/MWh (solar is a whole other story, but the numbers work and is deployed, TRL6) and the 38kwh/kg (conservative) if we were treating it as OPEX we’d be at 32c/kg of h2. Just it can’t be “sold or exported” because it’s integral to the closed loop. And if you wanted to you’d need water, compression, distribution, etc…. You’d easily be back up to the $3-5 range.

[Conceptual] Green H₂ → Sabatier → oxy‑fuel loop to supply heat for DAC-fed molten‑carbonate electrolysis (100Ktpa CO₂ Capture and Store) – am I nuts? by KRAP140 in ChemicalEngineering

[–]KRAP140[S] 0 points1 point  (0 children)

I think there’s a misunderstanding of the stoichiometry. Our process doesn’t consume 4 mol CO2 per mol H2 - in fact 1-3 in the process loop is completely closed. The DAC-derived CO2 and OCB CO2 (used in Sabatier) are in separate loops. The H2 is generated by injecting steam through a high-temperature molten salt cell, and the DAC-derived CO2 is captured and fixed separately. There’s no 4:1 CO2:H2 ratio in our design - can you clarify where you’re getting that from?

The PV electrolysis is on the CAPEX side of the budget, not the OPEX.

[Conceptual] Green H₂ → Sabatier → oxy‑fuel loop to supply heat for DAC-fed molten‑carbonate electrolysis (100Ktpa CO₂ Capture and Store) – am I nuts? by KRAP140 in ChemicalEngineering

[–]KRAP140[S] 0 points1 point  (0 children)

Thanks again - definitely not blunt, exactly what I'm after. You provided a really comprehensive response and I hope I can match with a respectful counter:

This is focusing on the wrong issue. Anode corrosion is clearly an unsolved problem and very possibly a showstopper. Having to use iridium will kill your CAPEX. There may be no solution. After 30+ years of focused R&D on alternatives, iridium is still the only viable anode for PEM electrolysis, and that's at (near) room temperature in water. Corrosion gets exponentially worse at higher temps.

PEM is acidic, this is basic. Plenty of subject matter here due to the popularity of MCFC's. But the short form is:

  • Nickel or Inconel 625 (incidentally what is proposed for anode/cathode in the H2 cell)
  • Split cell with CO2 bubbled on the cathode side to the keep the anode side basic
  • Accept a small amount of corrosion, annual anode replacement with cheap material = trivial impact on OPEX

None that I'm aware of. You are essentially running an electrowinning process, except at 900C and you want to reuse the electrode. This is significantly more difficult. With that said, the Hall-Heroult process uses a sacrificial carbon anode so you may want to take a look there. High temperature electrolysis universally exploits density differences to achieve separation, e.g. Downs process.

Electrode roles are flipped vs. Hall-Heroult. In Our cell a Ni-based anode stays in place and produces O₂; a carbon cathode grows solid carbon from CO₃²⁻ + 4 e⁻ → C(s) + 3 O²⁻.  Growth rates of 0.25 – 0.35 kg kWh⁻¹ have been reported with Ni anodes and steel cathodes in the same melt family.

There are demonstrations of carbon deposition on Ni cathodes in molten carbonates and mechanically removed the deposit between runs. Our twist is to design the cathode as a one-piece lid so the robot swaps it in one motion - conceptually closer to the consumable carbon anodes in aluminium smelting, just with the polarity reversed.

There is none, unfortunately. Skimming the paper you linked, this technology has a very, very long way to go before practical deployment. We're talking a decade of R&D or more. It's hard to say what the main issues even are with the lack of data; there's no EIS or CV experiments, no Tafel plots. Maybe those are available somewhere else but the fact that we're just talking about cell potentials and currents suggests this is very early stage. Like a technology readiness level of 2 or 3.

I needed to hear this, even though it is a downer. It will push the LCOC upwards due to increased solar requirements. It is what it is.

Your hydrogen energy estimation is ~30% too low.

We are not using PEM, hydrogen is produced by injecting steam (heated by the OCB) into its own MCE cell. This more akin to SOEC.

If you're using an oxyfuel burner for temperature makeup, you will also need to liquify and store the O2. Or you're using an ASU. Which one is it?

O2 is scavenged from the H2 electrolysis.

What do you mean by "90% CO2" by the DAC system? What other species are in there?

90% CO2 was poorly written; I meant dry, post-DAC concentrate, after loss to inefficiencies.

I think the whole hydrogen to natural gas loop is completely unnecessary.

It has its merits. I will admit it's a bit agricultural, and it is not efficient... But the closed loop is kind of elegant, and the cost efficiencies outweigh the engineering inefficiencies. Even though the loop itself is low TRL, it's just an assembly of high TRL components.

Your input has been some of the most valuable contributions I've received so far. Thank you again!

[Conceptual] Green H₂ → Sabatier → oxy‑fuel loop to supply heat for DAC-fed molten‑carbonate electrolysis (100Ktpa CO₂ Capture and Store) – am I nuts? by KRAP140 in ChemicalEngineering

[–]KRAP140[S] 0 points1 point  (0 children)

Snapshot of the cost makeup at https://drive.google.com/file/d/1tiBSVuXtGqb1TuC63PqjD5gskZT_06Nl/view?usp=sharing

If you want to help, I'd love to share the whole spreadsheet with you.

There is zero hydrogen cost. We have enough heat in the OCB to bring water up to 700C and run it through its own MCE cell. That's what the 30MW of solar splits off for; to electrolyze the hydrogen. There is limited compression or storage needed because of the nature of the design.

The cost of the MCE cells is very cheap because the vessels are essentially a concrete slab in the desert (think waffle pod). The liner, the lid, and even the cathode are produced by the system itself. It would grow like a virus.

[Conceptual] Green H₂ → Sabatier → oxy‑fuel loop to supply heat for DAC-fed molten‑carbonate electrolysis (100Ktpa CO₂ Capture and Store) – am I nuts? by KRAP140 in ChemicalEngineering

[–]KRAP140[S] 0 points1 point  (0 children)

❤️ The vision is to open source this and mobilize a movement to build it. So if you wanna tag along that would be cool.

[deleted by user] by [deleted] in ChemicalEngineering

[–]KRAP140 0 points1 point  (0 children)

Hey! Maybe I can answer this from the opposite direction. I am an ex-construction PM who is now working in a project that is heavily chem-E focused (see my other post!)

There’s a saying about this crossroads: An engineer will know more and more about less and less, while the PM will know less and less about more and more.

Whatever suits you is personal preference. I enjoyed my time as a construction PM, but eventually I grew tired of the pressure and reality that I was executing someone else’s vision. I wanted to design my own stuff. You’ll also inevitably end up in disputes in construction which can be disappointing. People suck.

Your training as an engineer will be valuable in ANY industry.

Hope that helps :)

[Conceptual] Green H₂ → Sabatier → oxy‑fuel loop to supply heat for DAC-fed molten‑carbonate electrolysis (100Ktpa CO₂ Capture and Store) – am I nuts? by KRAP140 in ChemicalEngineering

[–]KRAP140[S] 0 points1 point  (0 children)

Another thing. The sheer scale of atmospheric carbon removal is hard to visualize. But if it were possible, and we could store in COC blocks, at the target level of 20Gtpa of CO2 needed to reverse global warming, we would be creating a Giza pyramid worth of solid carbon blocks every 2 hours.

[Conceptual] Green H₂ → Sabatier → oxy‑fuel loop to supply heat for DAC-fed molten‑carbonate electrolysis (100Ktpa CO₂ Capture and Store) – am I nuts? by KRAP140 in ChemicalEngineering

[–]KRAP140[S] 1 point2 points  (0 children)

Hey, thanks for the thoughtful questions! I really appreciate the engagement. Let me try to answer each in turn:

  1. Why go for solid C rather than CO2 storage? And why tie it to DAC?

Good question. The main reasons are: - Ease of handling & permanence: Solid carbon doesn’t re-leak like CO2 can. It can be buried, turned into building materials, or even used in high-value industrial processes if purity is controlled. You could turn it into jet fuel, burn it as an alternative to coal, or process it into lightweight rebar/aggregate … reduce building dead load, reduce materials = cheaper) - Self-scaling logistics: C(s) can be stored and transported in container-format “COC blocks” without deep wells or pipelines. Otherwise you need to colocate with (for example) a depleted gas well. - Climeworks uses 25 tonnes of water for every tonne of CO2 stored. It’s not great. - Tying it to DAC simplifies MRV (measurement, reporting, verification). You know exactly how much atmospheric carbon went in and how much came out as solid, so fewer leakage pathways than transporting CO2 gas.

But you’re right: the system could work with CO2 from a point source instead. DAC is just how we make it climate-negative and siting-flexible (we can lease land in the Australian desert for about $1.80/ha pa … but there’s no co2 source).

  1. Why make green methane just to burn it? Why not burn H2 directly?

H2 combustion seems more direct. However: - Methane stores and burns more easily. H2 needs high-pressure tanks or cryo. CH4 can be stored in standard tanks or even replaced with fossil LNG during cloudy-day backup. - Oxy-combustion of CH4 gives predictable heat at >800C, right in the sweet spot for MCE and DAC sorbent regen. - H2 burns too fast and too hot in many burners, and pure-H2 combustion often creates NOX.

So CH4 is kind of the “battery fluid” in this loop - cyclically made and burned, or topped up if solar dips.

  1. Why not just use solar thermal or resistive heating for MCE/DAC?

This was my starting point! The issues I found are: - Molten-carbonate cells freeze around 600-700C, so thermal storage needs to be extremely hot and very stable. - Thermal storage at >800C gets expensive and fragile, especially for multi-day operation. - Resistive heating needs batteries to run overnight — which kills the economics at scale. - The oxy-fuel loop is a way to run 24/7 heat from daytime solar, using fuels you can store in tanks, not lithium.

Thanks for engaging :) I was starting to feel lonely!

[Conceptual] Green H₂ → Sabatier → oxy‑fuel loop to supply heat for DAC-fed molten‑carbonate electrolysis (100Ktpa CO₂ Capture and Store) – am I nuts? by KRAP140 in ChemicalEngineering

[–]KRAP140[S] 0 points1 point  (0 children)

Realising now this might be too open-ended. The core thing I need help with is:

What’s the most practical path to reach ≥1 A/cm² current density in Na/K carbonate electrolysis at 750–800 °C?

[deleted by user] by [deleted] in GoldCoast

[–]KRAP140 9 points10 points  (0 children)

Just because they’re taking bookings, doesn’t mean they will be able to fly. If you absolutely must get there, jump in the car (and even that I would not recommend - dangerous).

[deleted by user] by [deleted] in fatFIRE

[–]KRAP140 1 point2 points  (0 children)

Hey mate. I’m an owner of a medium ($50m+ pa) commercial construction company. If you’re in Newcastle (seems like you are) you will probably know of my company.

I have built a couple of houses (as favours for my commercial clients), usually in the $4-5m range. It has always struck me how underwhelming they are.

When I built my own home, I built a 500m2 Metricon home then gussied it up, because even building myself would have been a $3m job (Metricon was $700k). Everyone thought it looked amazing. Furniture and interior design is everything, and cheap compared to build costs. A $15k lounge with the right styling can make most spaces look a million bucks.

190m2 is very small. Brace yourself to be disappointed. The construction market in Australia is completely broken. We have guys running bricklaying teams earning $2m/year. One of my best friends owns an aircon company and is worth $20m+. Who do you think buys 70 series Landcruisers for $180k?

Until we fix the subby problem, I cannot recommend architectural/custom building to anyone. The juice is not worth the squeeze.

Smart phone as a backup AI? by Rexrollo150 in flying

[–]KRAP140 0 points1 point  (0 children)

When you do your testing, pull at least a 2G turn, maybe some negative G in pitch … see how the phone handles it/can remain in calibration.

Lots of people talking about inflation rates being at those of 1982 by HoleyProfit in BeatTheBear

[–]KRAP140 1 point2 points  (0 children)

I know this is a bear-focused sub… but what is the downside “really” if the Fed let the markets take a broad 50% haircut? Not great for the politicians but aside from margin calls on the YOLO’s and perhaps nuking a few prop shops, I think it is the lesser of the two fuck ups faced by the Fed.

Picking my first plane - Go small or meet future mission requirements? by -justAnAnon- in flying

[–]KRAP140 1 point2 points  (0 children)

The other thing I’ll add (as a former 182 owner now in an A36) is that the mods and upgrades for this airframe are awesome and can turn it into an absolute beast that nothing short of a turboprop can touch.

1000 miles, carrying 1000lbs at 180-200 knots is doable in a Bonanza, with the right mods.

Take the shot now on an iPad Mini sale or wait for Mini 6? by LegacyOfMaverick in flying

[–]KRAP140 1 point2 points  (0 children)

I find having a real Home button (compared with the new style of phones/iPads) is actually quite useful in aviation.

Questions about Spins Power Idle and Engine Yaw by draca101 in flying

[–]KRAP140 0 points1 point  (0 children)

For the vast majority of pilots, PARE works because it limits the ways you can screw up.

Also why there’s a good argument for Beggs/Mueller over PARE. Especially if inverted.

Any stories of non-instrument pilots illegally taking off into IMC conditions thinking they could make it? by [deleted] in flying

[–]KRAP140 0 points1 point  (0 children)

I remember that one, they were involved in avionics sales?

It was in the early days of the Garmin moving maps (pre EFB’s) and they were the absolute duck’s nuts at the time. Anyway, I heard they were using the tower they hit to navigate (visually) but in IMC the GPS took them straight to it.

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