I think the main thing to look at is the acid regeneration cost. It (acid regen) has to go through a third party company. This generally cuts into a profits in a major way.
I can tell them how to acid regen. Simply vacuum the stuff into evap and precip later.
I realize LHD of earth is not expensive. Clay, however, would be a caution, winter and summer. Whatever costs you calculate you can generally multiply it by three for clay. Bond work index for clay is low, about 7 to 10 kwh per tonne, but it depends on how fine you want to grind it.
Clay by definition is inherently fine to begin with. I don't see why they need to grind it. They must need surface area bad. Clay is defined as stuff that is 0.002 mm to begin with. 2 microns. 1/12,700 of an inch. They don't even make mesh sizes in Tyler standard screen that fine. You need to grind that? I think they mean a dispersal grind, or a separation into natural particulates. But that forms a slime, which means one would need a slime bucket. Or something.
Other people make alumina for those smelters too. The Orbite thingie is to (try to) compete with the alumina makers. A thing the Guyanese are looking to do too. And they have the world's best low silica bauxite by the county.
This HCL thing has been around for a while. This is from 1946.
pubs.acs.org 
This from 1981. Patent abandoned. But it demonstrates prior art.
freepatentsonline.com
"Extraction of aluminum from clays by means of acids, such as hydrochloric, sulfuric, or nitric acids, is well known. Generally, the clay is initially ground, and then calcined at temperatures of about 650° to 850° C., followed by leaching with about 6 to 10 normal solutions of acid at ambient pressure and boiling temperature. Aluminum is thus readily leached from the clay. However, the leached residues are difficult to separate from pregnant solutions because of the presence of slimes resulting from submicron-size clay dusts on the surfaces of the ground clay particles.
Prior art attempts to overcome this problem have generally involved formation of pellets by agglomeration of the ground clay. For example, U.S. Pat. No. 4,246,239 discloses formation of pellets by mulling the clay, extruding it and then recompacting the pellets by rolling them in a rotating drum for 30 minutes or more. Such processes, however, involve relatively complicated and time-consuming procedures. Moreover, the pellets formed thereby still tend to produce slimy residues, apparently due to scrubbing and attrition of large particles on reactor walls and breakup of poorly formed agglomerates.
It has now been found, according to the present invention, that these problems may be largely overcome by means of a process in which the raw clay, after initial crushing to a suitable particle size, is treated with water in the form of a fine mist and in an amount sufficient to form a dense, smooth surface on the individual particles but not sufficient to cause agglomeration of these particles. However, submicron-size dusts are thereby agglomerated on the surfaces of the larger particles. The misted clay is then dried at a temperature, and for a time, sufficient to cause the particles to shrink and harden. In addition, the drying causes the fine, submicron-size clay dusts to become firmly attached to the surfaces of the larger clay particles. This combination of misting and drying steps results in a feed material that is readily calcined and leached according to conventional procedures, with minimum formation of slimes in the leaching process, as illustrated in the examples below.
In the process of the invention, the raw clay is initially crushed to a particle size suitable for leaching. This will generally be a particle size ranging from about minus 20-mesh to about minus 14-mesh. Optimum particle size will depend on the specific clay, subsequent drying and calcing conditions, and specific leach solution employed, and is best determined experimentally. As mentioned above, the resulting particles are characterized by the presence of submicron-size dusts on their surfaces.
The crushed clay is then subjected to agitation in the presence of water in the form of a fine mist in order to consolidate the submicron-size dusts and form a dense, compacted surface on the individual clay particles. The amount of water thus employed is, however, limited to that necessary to thoroughly moisten the particle surfaces, without causing agglomeration of the clay particles into larger aggregates. Again, the optimum amount of water will depend on the specific type of clay, as well as particle size and water content of the crushed clay and leaching process steps, and is best determined experimentally. Generally, however, for a kaolin clay, the resultant water content of the clay particles will be about 18 to 20 percent.
Agitation of the crushed clay during misting may be by any conventional means insuring adequate contact of mist with the particle surfaces. A particularly preferred means has been found to consist of tumbling of the crushed clay on an inclined rotating disk, while simultaneously applying the mist. The mist is also formed by conventional means such as airless or air atomizing spray nozzles, and preferably consists of water particles about 10 to 40 microns in diameter." |
