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A California startup that is working on a method to produce nitrogen fertiliser at the point of use, using intermittent solar power. Works by generating nitric acid from air and water and then neutralising it to create a nitrate that can be applied to the soil. More energy intensive than the ammonia route, but it doesn't require the high pressures of the Haber process and appears to be a simpler smaller chain (nitrogen + water -> nitric acid -> potassium nitrate, rather than having to selectively oxidise ammonia). And unlike the Haber process it can be stopped and started fairly easily.
Use what is abundant and build to last
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Sounds very promissing. Their results suggest that only 1/3rd as much fixed nitrogen is needed per acre compared to ammonium nitrate, because nitric acid is liquid and can be applied regularly as a solute in water, rather than as a single batch before planting. This reduces runoff. Another advantage is avoidance of having to accumulate solid nitrates, which are an explosion hazard. Concentrated nitric acid is very corrosive. But as a dilute solution it is easy to store in stainless steel tanks. As the paper notes, calcium carbonate will neutralise it.
This development is timely. A large chunk of nitrate fertiliser production has disappeared from the world as a result of sanctions against Russia. A scalable replacement has an open market.
Last edited by Calliban (2022-10-17 03:56:28)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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Thanks to Terraformer for finding and posting this encouraging news!
Best wishes for success with topic! It is good to see Calliban's endorsement.
Small farm application of this technique might permit small farms to compete in the industrial agriculture industry.
However, there may be advantages of scale that tip the balance in favor of large operations.
(th)
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Interesting report on the use of a modified Claude process, for small scale ammonia production.
https://www.sciencedirect.com/science/a … 9921012660
This process uses a single pass, multi-stage reactor, with ammonia adsorption in chlorides or zeolites to increase conversion factor. Despite their increased expense, ruthenium based catalysts were found to be favourable, as they increased conversion factors and allowed the reactors to be more compact. The resulting small scale ammonia production is slightly less efficient in energy terms than the standard Haber-Bosch process. But at small scale, it has lower capital costs, resulting in reduced ammonia product costs. It's lower pressure and operating temperature is also more compatible with intermittent operation.
From the article:
'The high-pressure Haber-Bosch synthesis loop benefits from large scale application, with a cost scaling factor of 0.64. A dominant cost factor is the feed compressor, which amounts to over 50% of the CapEx in the ammonia synthesis loop at capacities below 10 t-NH3 d−1 (see Figure S12) [15,85]. Thus, absorbent-enhanced ammonia synthesis loops operating at the same pressure as H2 and N2 production benefit from small scale-operation.'
'On the other hand, the overall conversion is assumed to be about 89% for option c [Claude process], with a total energy consumption of 41 GJ t-NH3−1, which is due to not recycling the residual H2 and N2 after the third reaction-separation step (see supplementary information S2.3 for additional discussion). For reference, the total energy consumption of option a [Haber process] is 35 GJ t-NH3−1'.
If we wanted to produce ammonia as an industrial scale synthetic fuel, then the most energy and capital efficient option would be scaled up Haber-Bosch reactors, with energy provided by multi-GW nuclear power reactors built on site, along with a cryogenic air separation unit. However, for small scale production of fertiliser on farms, the Haber process does not appear to be cost optimal.
Last edited by Calliban (2022-11-14 22:08:25)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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