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Very cool! It sounds like your sorbent requires calcium to precipitate calcium carbonate from sea water. What would be the source of this calcium? Hopefully it

by pmat 5y ago

Very cool! It sounds like your sorbent requires calcium to precipitate calcium carbonate from sea water. What would be the source of this calcium? Hopefully it won't come from reducing lime!

marcuslima 5y ago
The calcium all comes from dissolved calcium bicarbonate - we trigger precipitation by shifting bicarbonate to carbonate ions, which are insoluble. Essentially we acceelrate the oceanic carbonate cycle
- LeifCarrotson 5y ago
  I understand that calcium salts and bicarbonate ions are common in the ocean, and are increasingly common as the oceans become more acidic, but have no idea how common that is. How much seawater do you need to get one kg of CaCO3 precipitate?
  - marcuslima 5y ago
    We're actually working on figuring this out. Our current calculations assume we need to process a huge amount of seawater (11,000 tonnes per tonne of CO2), if the CO2 is the limiting factor (2000 umol). However our R&D suggests undersaturated seawater re-absorbs CO2 from the air surprisingly quickly. Might be able to get this 10x lower
    - twic 5y ago
      Is it surprising? Carbon dioxide equilibrates between salty water and air fast enough to keep every single terrestrial animal on the planet alive, after all.
    - ephbit 5y ago
      Wow .. 11,000 tonnes of seawater per tonne of CO2 is indeed huge. Assuming that the new process stochiometrically generates CaO according to the amount of CO2 taken up from the ocean you'd produce 1.27 tonnes of CaO per tonne of CO2. (molar masses of CO2 and CaO: 44 g/Mol and 56 g/Mol) Cementa website states [1] an annual output of 2.7 million tonnes of cement. So in order to produce what is only a portion of Sweden's (a comparatively small country) annual demand for cement, Heimdal's process would require processing of ~ 23 billion tonnes of seawater. That's 23 billion cubic metres or 23 cubic kilometres per year or ~ 730 litres of seawater per second. [1]: https://www.cementa.se/en/about-cementa https://www.cementa.se/en/about-cementa
      - liketochill 5y ago
        .73 m^3/s of seawater is only a pipe of 1m diameter with water traveling at 1 m/s. Not that big a pipe in the grand scheme of things!
        ephbit 5y ago
        True. Not that big. But let's not forget that it's not about merely pumping the water around. All this water must be processed. And I figure the process is a little more involved than simple reverse osmosis for seawater desalination. In the desalination business 1 m diameter pipes with water traveling at 1 m/s and the resulting volumetric flow rate isn't a big thing .. but I'd guess for more complex processes it indicates huge/expensive apparatuses.

by pmat 5y ago

Very cool! It sounds like your sorbent requires calcium to precipitate calcium carbonate from sea water. What would be the source of this calcium? Hopefully it won't come from reducing lime!

marcuslima 5y ago

The calcium all comes from dissolved calcium bicarbonate - we trigger precipitation by shifting bicarbonate to carbonate ions, which are insoluble. Essentially we acceelrate the oceanic carbonate cycle

LeifCarrotson 5y ago
I understand that calcium salts and bicarbonate ions are common in the ocean, and are increasingly common as the oceans become more acidic, but have no idea how common that is. How much seawater do you need to get one kg of CaCO3 precipitate?
- marcuslima 5y ago
  We're actually working on figuring this out. Our current calculations assume we need to process a huge amount of seawater (11,000 tonnes per tonne of CO2), if the CO2 is the limiting factor (2000 umol). However our R&D suggests undersaturated seawater re-absorbs CO2 from the air surprisingly quickly. Might be able to get this 10x lower
  - twic 5y ago
    Is it surprising? Carbon dioxide equilibrates between salty water and air fast enough to keep every single terrestrial animal on the planet alive, after all.
  - ephbit 5y ago
    Wow .. 11,000 tonnes of seawater per tonne of CO2 is indeed huge. Assuming that the new process stochiometrically generates CaO according to the amount of CO2 taken up from the ocean you'd produce 1.27 tonnes of CaO per tonne of CO2. (molar masses of CO2 and CaO: 44 g/Mol and 56 g/Mol) Cementa website states [1] an annual output of 2.7 million tonnes of cement. So in order to produce what is only a portion of Sweden's (a comparatively small country) annual demand for cement, Heimdal's process would require processing of ~ 23 billion tonnes of seawater. That's 23 billion cubic metres or 23 cubic kilometres per year or ~ 730 litres of seawater per second. [1]: https://www.cementa.se/en/about-cementa https://www.cementa.se/en/about-cementa
    - liketochill 5y ago
      .73 m^3/s of seawater is only a pipe of 1m diameter with water traveling at 1 m/s. Not that big a pipe in the grand scheme of things!
      - ephbit 5y ago
        True. Not that big. But let's not forget that it's not about merely pumping the water around. All this water must be processed. And I figure the process is a little more involved than simple reverse osmosis for seawater desalination. In the desalination business 1 m diameter pipes with water traveling at 1 m/s and the resulting volumetric flow rate isn't a big thing .. but I'd guess for more complex processes it indicates huge/expensive apparatuses.