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V-I
POTASH PROCESSING TECHNOLOGY
Ibrahim Gundiler
Introduction
Potash ores must be beneficiated to remove halite (NaCO, clays, and other insoluble
material to produce mdcetable products. Silvinite (KCl + NaCl) and langbeinite (K2S0•
. 2MgS0 4 ) are the two ore types currently mined in the Carlsbad Potash Distric The
average K20 grade of silvinite ores is abow 14-16% and that of langbeinite aboUl 8-10%
(Austin and Bcder, 1993).
Sylvinite ores are generally beneficiated by flotation of sylvite (KCl) in saturated
brine solutions using cationic collectors (pr::nary aliphatic amines) and frothers. The
product, muriate of potash, contains 60% E._Q and it is marketed in different size grades.
Presence of clay minerals, however, may interfere with the flotation process. Clay
minerals preferentially absorb the flotation reagents, causing excessive reagent consumption
and hindering the recovery of sylvite. Therefore, they are removed prior to flotation
by scrubbing and desliming (Scroggin, 1978). Flotation of clay minerals remaining in the
pulp is further suppre,."ed by using a starch or cellulose derivative and some fuel oiL
Ores with much hight msoluble and clay content, i.e. 6-7%, are hCleficiated by
dissolution and selecuve crystallization from the resulting brines (Case, 1978; Zandon,
1985).
Langbeinite is mined in only two locations in the world. It has been mined continuously
in the Carlsbad district since 1940 ane'. Dtermittently in the Stebnik: mine in the
Ukraine since the 1930s (Rempe, 1982). La::lgoeinite is much less soltDle thar, either
sylvite or halite. Most often, it can be upgraded to 22% KzO levels by selective dissolution
of the more soluble minerals. However, polyhalite (K2S0•. MgSO•. 2CaSO•.
2H20), a frequent impurity, has solubility similar to langbeinite and may be difficult to
remove.
Alternatively, because langbeinite has higher specific gravity (S.G. 2.8:3 than either
sylvite (S.G. 1.99) or halite (S.G. 2.16), it can be separated from mixed ores using
heavy-media separation processes in coarse sizes (landon, 1985). Langbeinite fmes can
be further beneficiated using anionic collectors (fatty acids) in conventional f Aion
circuits. The world's first langbeinite flotation circuit and a heavy-media circm were
installed at !MC's Carlsbad plant during the mid-60s, but the details of these operations
have not been disclosed.
Excellent reviews on potash resourc~:, and potash processing are available in the
readily accessible literature (Williams-Stroud et al., 1994; Sullivan and Michael, 1986;
Zandon, 1985). There"bre, only a brief review of the recent advances in basic theory and
processing technology, as it pertains to the Carlsbad District, is given in this report.
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