With biofuel ferment
A solution potash mine operator likely would not want to become a producer of biofuels. However, it would be mutually beneficial for both the miner and such a biofuel maker to become closely associated. Here’s why ….
Ferments are one path to making biofuels, and a potash mine can provide an inexpensive means of isolating the desired products from a ferment. A strong brine is the key aspect. ..Keep in mind the ferment products will be present only in dilute solution.
Two types of ferments may be involved, to solvents being the more obvious, and ethanol the most widely known. Butanol, 2,3.butanediol, and acetone (propanone) are some others. Here, by mixing the ferment liquid with a saturated NaCl brine in some proportion, and likely in small batches, the solvent floats atop the brine. This minor layer of concentrated product is readily decanted and the solvents distilled. As the volume is small, so is the amount of heat required compared with heating the entire ferment liquid. Smaller capacity distilling apparatus costs less.
The other type of ferment yields organic acids to be made into biofuels. Here also a strong brine is useful in isolating them. The most likely acids are butanoic, propanoic and acetic (ethanoic), maybe some hexanoic acid. ..If present as their calcium salts, any hexanoate, then butanoate, are least soluble and may be filtred out.
The butanoic can be contacted with a hot catalyst to yield its ketone: PPK [dipropyl ketone], which is practically insoluble in water, fairly energy dense, and a fuel for both EC or gasoline engines, blending well with gasoline.
{note: _these ferments also produce CO2 made from the annual plantstuff being fermented. This is a recycling of CO2 that the plants took from the air during their growth. Such recycling does not augment aerial levels of carbon dioxide — only CO2 with fossil-C does.}
CaAcetate_ up to ~35 degrees C it is so close in solubility with NaCl that another means of isolating it is needed. Simplest is adding NaCarbonate to drop CaCarbonate leaving NaAcetate behind, which later is useful to the potash miner in reducing costs of crystallising KCl from the upwelled brine. __The scenario here is as follows:
1. Crystallise KCl from upwelled brine until KCl to NaCl ratio is something like 1:6 or 1:5;
2. Then transfer the brine from the crystalliser, adding NaAcetate to it. Here an NaCl solution of the acetate coming from the fermenter may be used. Now send this brine to a solvent extraction column, an inlet near the top;
3. Solvent rising in the column removes KAcetate so brine exiting at the bottom is wholly NaCl; it may be downwelled or sent back to the fermenter;
4. Solvent is ethanol, maybe methanol or perhaps some other chemical;
5. Doing the above keeps the upwelled brine less long in the crystalliser, upping its throughput. Also, the K product obtained is more valuable than ordinary KCl.
At this point the miner has a few options for the solvent exiting the top of the column — [a] distil the solvent leaving KAcetate as the product; or [b] instead, contact it with CO2, to drop the carbonate out, or bicarbonate if any water is present. Oddly, some freed acetic is said to cling to a KAcetate molecule (says an old British patent). ..Solvent may then be distilled off, and at higher temperature acetic acid vapour. This KAcetate then recycled if acetic acid is the wanted product.
{_Of course, what is claimed in a patent is not always reliably workable in practice, and could be the case here. However, adding a little ammonia to the solvent before contacting the solution with CO2 should provide a catalytic effect._}
Another brine:__ The solution mine might also have a brine mainly KCl but with more NaCl than wanted in a commercial fertiliser. Adding KBicarb to it would drop out NaBicarb sufficient to correct that situation. Heating NaBicarb converts it into the carbonate.
Products
If butanoate is produced in the ferment, this would be the fermenter’s, presuming this entity is separate from the miner.
{{ CaButanoate is not obviously a fuel itself — yet can be in making cement, using it where otherwise limestone would be introduced. High heat destroys the Ca salt to yield lime (CaO), one CO2, and burnable gases. As it is a biofuel, not fossil-C, no C.tax should apply, which may be a concern of the cement maker.}}
Electrolysis of butanoate yields hexane, itself a fuel, and which can be made into a gasoline by passing over some catalyst which creates branching. This has been used in petroleum refining for over a century.
K:bicarbonate would be more valuable as a fertiliser than KCl to certain overseas buyers, as it is really two products in one. Added to a strong NaCl brine precipitates NaBicarbonate, leaving KCl in solution. Heating the bicarb creates NaCarbonate (soda). So then the importer has fertiliser KCl plus soda that can be readily sold to industrial users, or to a packager marketing washing soda. Clearly, such an overseas importer would be willing to pay rather more for K.Bicarbonate than for ‘muriate of potash’ which is the name KCl carries as a fertiliser.
{While it may be tempting to ship K.Carbonate from a mine due to it weighing 30% less than the bicarb, it is very deliquescent, attracting moisture, so can’t be sent as dry bulk product.}
To sum up, a solution potash mine would have somewhat lower operating costs per tonne of product, due to greater utilisation of crystalliser capacity, were it coupled with a biofuels fermenter outfit. Potassium products having higher value per tonne than the usual fertiliser potash may be made, products especially attractive in particular overseas markets. Meanwhile, the fermenter will have lower operating costs due to this synergistic association with the potash miner.