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One company has automated to the fullest possible extent the operation of the
continuous mining machine and the mobile and extendible feed conveyor, so that only
two people lre required at the mining face. Another company using a similar but more
fully controllable extendible conveyor needs four people at the face. Productivity per
mining-face operator is as much as 50 tons per man-hour with either of the$~ systems.
Continuous mining is ideal for thin ore seams. Currently, the mining height is as
low as 4.5 ft, and the equipment in use can mine as low as 4.0 ft. Immediate subsidence
occurs over the mined area. A general rule is that the surface expression of subsidence
over high extraction areas amounts to 50-75% of the thickness mined.
Mineral processing-A separate section describes potash mineral processing, but an
overview of the process that would be used for the specific langbeinite and mixed
sylvite-langbeinite ores that are common in the WIPP area is included here because that
type of plant was used in this economic evaluation. Figure 4 is a simple flow sheet that is
being used by !MC Fertilizer, Inc. to treat mixed ores. If the ore is just langbeinite, then
it is treated by a rather simple but carefully controlled leaching method to produce as
many as four final products depending on the grain-sizes of the raw ore.
If the ore is mixed, then it is ftrSt passed through a heavy media circuit to separate
the two ore minerals. The heavy fraction (langbeinite-bearing) is passed back into the
langbeinite-processing part of the plant. The sylvite fraction is concentrated by flotation.
Additional langbeinite that escaped separation in the heavy media plant is recovered by
refloation of the sylvite tailing. The recovered product is passed back in the langbeinite
circuit.
An important ability of the !MC process is to combine the fine-particle products
from both the langbeinite and sylvite circuits for additional treatment in a separate (not
shown in Figure 4) part of the plant to manufacture KzSO. product. The exact process is
held proprietary to !MC; however, the process includes a ftrSt step of hydrating the
langbeinite followed by reaction with dissolved sylvite to form KzSO. and MgClz.
Hence, three products are produced from a mixed ore: sylvite, langbeinite, and
manufactured arcanite (K.zSOJ. If the ores present within the WIPP area are mined, then
the !MC method of treating mixed ores could be utilized.
VI-5
ESTIMATION OF MINING, PROCESSING, AND CAPITAL COSTS
Total mining and processing cost was estimated on the basis of direct operating
expense exclusive of both Federal and State income taxes. Also not included are local
county taxes. However, the selling price for products was reduced 3% to account for
royalties, rentals, and resource and severance taxes that are paid to Federal and State
governments. Direct operating cost does include all costs including normal repair and
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