111111111111111111111111111111111111111111111111111111111111111111111111111
US006173840Bl
(12) United States Patent
Pruszko et al.
(10) Patent No.:
(45) Date of Patent:
US 6,173,840 Bl
Jan. 16,2001
(52) U.S. CI. 209/214; 209/3; 209/218;
209/11
(51) Int. CI? B03C 1/00; B07B 1/00;
B03B 1/00
(73) Assignee: Environmental Projects, Inc., Casper,
WY(US)
(21) Appl. No.: 09/027,043
(22) Filed: Feb. 20, 1998
Related U.S. Application Data
(60) Provisional application No. 60/038,759, filed on Feb. 21,
1997.
4,054,513 * 10/1977 Windle 209/223.1
4,214,984 * 7/1980 MacElvain 209/214
4,236,640 12/1980 Knight 209/587
4,277,329 * 7/1981 Cavanagh 209/223.1
4,294,690 * 10/1981 Kollenz 209/214
4,324,577 * 4/1982 Sepehri-Nik 209/214
4,341,744 * 7/1982 Brison 423/206
4,363,722 12/1982 Dresty, Jr. et al. 209/3
4,375,407 * 3/1983 Kronick 209/8
4,375,454 * 3/1983 Imperto et al. 209/214
4,388,179 6/1983 Lewis 208/177
4,512,879 4/1985 Attia et al. 209/3
4,609,109 * 9/1986 Good 209/223.1
4,668,591 * 5/1987 Minemura et al. 209/223.1
4,737,294 * 4/1988 Kukuck 209/223.1
4,772,383 * 9/1988 Christensen 209/223.1
4,781,298 * 11/1988 Hemstock et al. 209/214
4,814,151 * 3/1989 Beuke 423/206
4,874,508 10/1989 Fritz 209/214
4,902,428 * 2/1990 Cohen 209/214
4,943,368 7/1990 Gilbert et al. 209/2
5,238,664 * 8/1993 Frint et al. 423/206.2
(List continued on next page.)
Primary Examiner-Donald P. Walsh
Assistant Examiner-Daniel K Schlak
(74) Attorney, Agent, or Firm---8heridan Ross Pc.
Under 35 U.S.c. 154(b), the term of this
patent shall be extended for 0 days.
(54) BENEFICIATION OF SALINE MINERALS
(75) Inventors: Rudolph Pruszko, Green River, WY
(US); Roland Schmidt, Lakewood;
Dale Lee Denham, Jr., Arvada, both of
CO (US)
( *) Notice:
(58) Field of Search 209/3, 4, 7, 9,
209/10, 11,214,218,223.1,225,226,
227,908
U.S. PATENT DOCUMENTS
References Cited
(57) ABSTRACT
Processes for purification of saline minerals using magnetic
separation are disclosed. In particular, saline minerals can
include trona, borates, potash, sulfates, nitrates and chlorides.
The magnetic separation can include high intensity
magnetic separation which can be conducted at greater than
about 20,000 Gauss and up to greater than about 50,000
Gauss. Other embodiments of the invention include calcination
of a saline mineral in an inert atmosphere or in an
oxygen-containing atmosphere at a high temperature prior to
magnetic separation. A further embodiment of the invention
includes pre-alignment of particles on a surface to align the
particles of high magnetic force during a magnetic separation
step. Also disclosed are various embodiments of magnetic
separation which include subjecting an ore to a preliminary
magnetic field prior to magnetic separation.
8 Claims, 9 Drawing Sheets
Uhlig.
Koren 209/223
Cavanagh et al. 241/24
Haseman .. 241/24
Laurila 209/214
Mayer et al. 209/111.8
Fraas 209/214
Coglaiti 209/12.2
Seglin et al. 23/63
Lee et al. 209/8
Sproul et al. 423/206.2
Frangiskos 209/3
Boom et al. 209/39
Noll 209/214
3/1921
5/1955
6/1961
2/1962
4/1966
10/1966
5/1968
9/1970
4/1972
1/1975
3/1975
2/1976
6/1976
* 11/1976
1,371,825
2,708,034
2,990,124
3,022,956
3,246,753 *
3,276,581
3,382,977 *
3,528,766 *
3,655,331 *
3,860,514
3,869,538 *
3,936,372 *
3,966,590
3,990,642
(56)
10
Feedstream/
:~ ~16__26
~24
US 6,173,840 Bl
Page 2
U.S. PATENT DOCUMENTS
5,470,554 * 11/1995 Schmidt et al. 423/206.2
5,651,465 * 7/1997 Schmidt et al. 209/12.2
5,736,113 * 4/1998 Hazen et al. 423/206.2
5,911,959 * 6/1999 Wold et al. 423/206.2
* cited by examiner
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2
SUMMARY OF THE INVENTION
One embodiment of the invention is a process for recovering
a saline mineral from an ore which contains saline
mineral and impurities. The method includes separating a
first portion of impurities from the ore by magnetic separation
which includes subjecting the ore to a magnetic flux
density of greater than about 20,000 Gauss. In a preferred
embodiment, the saline mineral selected from trona, borates,
potash, sulfates, nitrates and chlorides, and most preferably
is trona. In other embodiments, the process includes such a
method of magnetic separation of impurities, wherein an
impurity selected from shortite and pyrite are separated. In
these embodiments, at least about 25% of the impurity and
up to more than 75% of the impurity is removed.
In a further embodiment of the present invention, a
process is provided for recovering saline mineral from an
ore which includes saline mineral and impurities. The
method includes calcining the saline mineral in an inert
atmosphere and the separating a portion of the impurities
from the ore by magnetic separation. In a preferred
embodiment, the inert atmosphere is any nonoxygencontaining
atmosphere and can be selected from carbon
dioxide, nitrogen, and water vapor. In an alternative
embodiment, calcination is conducted in an oxygencontaining
atmosphere at a temperature of greater than about
1500 C. and subsequently separating a portion of the impurities
by magnetic separation. A further embodiment of the
present invention includes a process for the purification of
saline minerals in an ore which includes saline mineral and
50 impurities by magnetic separation in a first magnetic field,
wherein the first magnetic field has positions of higher
intensity and lower intensity. The process includes prealigning
the ore on a surface with respect to one or more of
said positions of higher intensity of said first magnetic field
before separation. The process further includes separating a
portion of the impurities from the ore by magnetic separation
in the first magnetic field.
In a further embodiment of the present invention, a
process is provided for removing magnetic impurities from
an ore which contains a saline mineral and magnetic impurities
and has a particle size of less than 100 mesh. The
process includes subjecting the ore to a magnetic flux
density of greater than about 20,000 Gauss whereby magnetic
impurities are separated from the saline mineral. This
process can include recovering greater than about 25 wt. %
of the magnetic impurities and up to greater than about 75
wt. % of the magnetic impurities.
beneficiating trona or soda ash that generally comprises the
step of density separation, and optionally includes electrostatic
separation and/or magnetic separation. U.S. Pat. No.
5,470,554 is incorporated herein by reference in its entirety.
5 The resulting product can have trona or soda ash purities on
the order of 97-98% or more. Although this process works
quite satisfactorily, there is always a desire to reduce the
number of steps, and thereby reduce the costs, associated
with separation processes. In addition, there is always a
10 desire to improve the recovery of beneficiation processes.
As such, it can be appreciated that it would be desirable
to be able to beneficiate trona or soda ash utilizing a low cost
dry beneficiation process to obtain trona or soda ash purities
of about 97-98% or higher and recoveries on the order of
15 90-95%. Accordingly, it is an object of the present invention
to provide a dry process for the beneficiation of trona or soda
ash resulting in higher purities and lower costs than many
existing dry beneficiation processes, and which is simpler
and less expensive than known wet beneficiation processes.
FIELD OF THE INVENTION
CROSS-REFERENCE TO RELATED
APPLICATIONS
BACKGROUND OF THE INVENTION
1
BENEFICIATION OF SALINE MINERALS
The present invention relates to the beneficiation of saline
minerals and, more specifically, trona, by methods of magnetic
separation.
This application claims priority from U.S. Provisional
Application Ser. No. 60/038,759, filed Feb. 21, 1997,
entitled "BENEFICIATION OF SALINE MINERALS."
Many saline minerals are recognized as being commercially
valuable. For example, trona, borates, potash and
chlorides are mined commercially. After mining, these minerals
need to be beneficiated to remove naturally occurring
impurities. 20
With regard to trona (Na2C03.NaHC03 .2H2 0), highpurity
trona is commonly used to make soda ash, which is
used in the production of glass, paper and other goods.
Naturally-occurring trona, or crude trona, is found in large 25
deposits in the western United States, such as in Wyoming
and California, and also in Egypt, Kenya, Botswana, Tibet,
China, Venezuela and Turkey. The largest deposit of trona in
the world is located in the Green River Basin in Wyoming.
Crude trona ore from Wyoming is typically between about 30
80% and about 90% trona, with the remaining components
including shortite, pyrite, quartz, dolomite, mudstone, oil
shale, kerogen, mica, nahcolite and clay minerals.
Many areas of the glass and paper making industries
require soda ash produced from trona having a purity of 99% 35
or more. In order to obtain such a high purity, wet beneficiation
processes have been used. Such processes generally
involve crushing the crude trona, solubilizing the trona,
treating the solution to remove insolubles and organic
matter, crystallizing the trona, and drying the trona which 40
may subsequently be calcined to produce soda ash.
Alternatively, the crude trona can be calcined to yield crude
sodium carbonate, which is then solubilized, treated to
remove impurities, crystallized and dried to produce sodium
carbonate monohydrate or calcined to produce soda ash. 45
While the above-described wet processes can produce with
high purity, they tend to be time consuming and expensive
to perform, and therefore result in a product which is much
more expensive than products produced using known dry
processes.
Not all industries which use trona or soda ash require such
a highly purified form. For example, certain grades of glass
can be produced utilizing soda ash having less than 97%
purity. For this purpose, U.S. Pat. No. 4,341,744 discloses a
dry beneficiation process which is less complex and less 55
expensive than the above-described wet beneficiation process.
Such a dry beneficiation process generally includes
crushing the crude trona, classifying the trona by particle
size, electrostatically separating certain impurities, and
optionally magnetically separating other impurities. Such a 60
process can yield trona or soda ash having up to 95% to 97%
purity with a 60-74% recovery, depending on the quantity
and type of impurities present in the crude trona ore.
There are uses for trona or soda ash, for example in certain
applications in the glass industry, requiring a purity of at 65
least 97%, yet not needing a purity over 99%. To accomplish
this, U.S. Pat. No. 5,470,554 discloses a dry method for
US 6,173,840 B1
3
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph of the magnetic properties of pyrite from
trona calcined at low temperature.
FIG. 2 is a graph of the magnetic properties of pyrite from
trona calcined at low temperature and washed with hydrochloric
acid.
FIG. 3 is a graph of the magnetic properties of pyrite from
uncalcined trona.
FIG. 4 is a graph of the magnetic properties of pyrite from
an ore body other than trona from Climax, Colo.
FIG. 5 is a graph of the magnetic properties of pyrite from
an ore body other than trona from Vulcan, Colo.
FIG. 6 is a graph of the magnetic properties of pyrite from
an ore body other than trona in Argentina.
FIG. 7 is a graph of the magnetic properties of shortite
from a non-magnetic fraction of uncalcined trona.
FIG. 8 is a graph of the magnetic properties of shortite
from a magnetic fraction of uncalcined trona.
FIG. 9 is an illustration of a design for an open gradient
magnetic separator.
DETAILED DESCRIPTION
The present invention is a dry beneficiation process for
recovering saline minerals from an ore containing the saline
mineral and impurities, and takes advantage of previously
unrecognized characteristics of such ore. As used herein and
in the mineral processing industry, the term "saline mineral"
refers generally to any mineral which occurs in evaporite
deposits. Saline minerals that can be beneficiated by the
present process include, without limitation, trona, borates,
potash, sulfates, nitrates, chlorides, and preferably trona.
The purity of saline minerals within an ore depends on the
deposit location, as well as on the area mined at a particular
deposit. In addition, the mining technique used can significantly
affect the purity of the saline minerals. For example,
by selective mining, higher purities of saline minerals can be
achieved. Regarding the saline mineral trona, deposits are
located at several locations throughout the world, including
Wyoming (Green River Basin), California (Searles Lake),
Egypt, Kenya, Venezuela, Botswana, Tibet, China and Turkey
(Beypazari Basin). For example, a sample of trona ore
from Searles Lake has been found to have from about 50%
to about 90% by weight (wt. %) trona and a sample taken
from the Green River Basin in Wyoming has been found to
have from about 70 wt. % to about 92 wt. % trona. The
remaining 8 wt. % to 30 wt. % of the ore in the Green River
Basin sample comprised impurities including shortite,
pyrite, shale consisting predominantly of dolomite, clay,
quartz and kerogen, and traces of other impurities. Other
samples of trona ore can include different percentages of
trona and impurities, as well as include other impurities.
Particular aspects of the present invention will be
described in the context of the saline mineral trona. Such
descriptions are not intended to limit the general applicability
of the present invention to only trona. Moreover, as
discussed herein, trona is often processed by calcination to
produce soda ash (Na2C03 ). It should be noted that, unless
specifically indicated otherwise, use of the term trona herein
can refer to both trona (i.e., Na2C03.NaHC03 .2H20) and
trona which has been processed by calcination to form soda
ash. In addition, it should be recognized that descriptions of
other processing steps herein (e.g., magnetic separation)
should be construed to include processing of calcined and
uncalcined trona. More particularly, it should be noted that,
4
in preferred embodiments, calcined trona is used for magnetic
separations and density separations described herein.
It has now been discovered that saline minerals, such as
trona, do not have a constant distribution of impurities
5 throughout the saline mineral particles. That is, crushed
saline mineral ore particles have a variety of impurity
contents ranging from no impurities in some particles to
almost total impurities in other particles. It is believed that
this characteristic of saline minerals was not previously
10 recognized. Therefore, until the recognition of the present
invention, there has been no suggestion or teaching to
conduct aspects of the present process. It has been discovered
that the impurities in saline mineral ores, such as trona
containing ores, are typically concentrated in a relatively
15 small percentage of the particles, while the rest of the saline
mineral particles can be of relatively high purity. For
example, under microscopic examination, most of the particles
of crushed trona after calcination are almost completely
white (i.e., substantially white), indicating highly
20 pure trona, while others are distinctly yellowish-brown,
indicating the presence of interstitial impurities. Such particles
can be selectively separated (e.g., manually sorted) to
yield a high purity fraction (e.g., about 97% or more saline
mineral) and a low purity fraction (e.g., less than about 97%
25 saline mineral).
It can be appreciated that, while the above-described
manual sorting process produces a suitable product, the
process can be impractical for high volume separation. The
process of the present invention, however, includes all
30 methods for selectively separating high and low purity
products whether manual or automated. That is, more
commercially-viable processes for separating the high purity
saline mineral from the low purity saline mineral also fall
within the scope of this invention. Thus, the process of the
35 present invention includes a process for selectively separating
a low purity fraction having more than about 3%
impurity content from a high purity fraction having less than
about 3% impurity content. Such separation is based upon
differences in the properties of the particles at the level of
40 impurities present in the particles.
In a preferred embodiment of the present invention, the
step of separating impurities from an ore containing saline
mineral and impurities includes the step of ultra-high magnetic
separation. The ultra-high magnetic separation step
45 subjects the ore to conditions such that materials of different
magnetic susceptibilities (e.g., trona and shale) separate
from each other into a recovered stream and an impurity
stream. In accordance with the present invention, the ultrahigh
intensity of the magnetic flux during the magnetic
50 separation step is at least about 20,000 Gauss, preferably at
least about 30,000 Gauss, and more preferably at least about
50,000 Gauss. It should be noted that 10,000 Gauss is
equivalent to 1 tesla and these units can be used interchangeably.
Such ultra-high magnetic fluxes are in contrast to the
55 above-described standard intensity magnetic separation at
less than about 20,000 Gauss because such standard intensities
are not sufficient to separate particles having both
magnetic (e.g., shale) and non-magnetic (e.g., saline
mineral) components. In order to generate such an ultra-high
60 magnetic flux, superconducting electromagnetic field generators
can be utilized. For example, an open gradient
superconducting magnet can be used. It should be appreciated
that other types of magnetic separators may be used, as
long as the required ultra-high magnetic flux can be
65 obtained. For example, it is recognized that some rare earth
magnets can now achieve a magnetic flux of up to about
28,000 Gauss. With regard to the beneficiation of trona,
US 6,173,840 B1
5 6
intensity separation as described herein. Alternatively, water
can be added to such a stream to dissolve the small crystals
therein. In addition, the liquid medium can be an alcohol or
other suitable medium.
In a further aspect of the present invention, it has been
surprisingly found that during high intensity magnetic
separation, as described above, impurities not previously
recognized as being susceptible to magnetic separation can
be separated. In one such embodiment, this process includes
10 subjecting a saline mineral containing ore to high intensity
magnetic separation, whereby the impurity shortite is separated
from the saline mineral. In another such embodiment,
the impurity pyrite is separated. In this process, at least about
25 wt. % of the impurity is separated, more preferably at
15 least about 50 wt. %, and most preferably at least about 75
wt.%.
As noted above, magnetic separation at under about
20,000 Gauss is known. It has been appreciated, however,
that there are limits on the effectiveness of such processes.
20 It has previously been thought that at 20,000 Gauss the
primary separation is between liberated impurities and trona
containing particles. As noted above, it has now been
identified that impurities in saline mineral are typically not
evenly distributed throughout the saline mineral particles.
25 However, it has been determined that, in performing a
magnetic separation on crushed trona ore using a 20,000
Gauss magnetic field, no appreciable separation or difference
in magnetic susceptibilities between high and low
purity particles occurred. At 23,000 Gauss, an identifiable
30 difference in magnetic susceptibility was noted between the
high purity particles and the low purity particles. In a
subsequent test, a 28,000 Gauss magnetic field was found to
give remarkable separation between the high purity particles
and the low purity particles. The high purity particles were
35 subsequently subjected to density separation at a 2.3 specific
gravity cut-off. The resulting purity of the product was on
the order of about 97%-98%, and the recovery was as high
as about 90%-95%. Therefore, in addition to discovering
that crushed trona ore actually comprises a large percentage
40 of high purity particles, it has also been discovered that a
high purity, high recovery trona product can be obtained by
subjecting crushed trona ore to ultra-high intensity magnetic
separation. (See, for example, Examples 1, 4 and 8.) Such a
process provides significant advantages because acceptable
45 purity levels and recoveries can be achieved without the
significantly greater expense associated with recrystallization
processes. It should be noted that high intensity magnetic
separation processes are more effective at separating
pyrite from trona ore having a wide size fraction (e.g., 6x20
50 mesh or 20x100 mesh) than, for example, density separations
such as air tabling. Therefore, a dry separation process
using only high intensity separation could be more useful
than a dry separation process using density separation when
the desired product must be low in pyrite so long as
55 moderate amounts of shortite can be tolerated. For example,
it is contemplated by the present inventors that some amount
of shortite may be desirable in soda ash in certain
applications, such as the production of glass. Alternatively,
high intensity magnetic separations can be conducted in
60 combination processes which also include density
separations, electrostatic separations or recrystallization
processes.
In a further aspect of the present invention it has been
surprisingly found that saline mineral particles of -100 mesh
65 can be efficiently separated by high intensity magnetic
separation, as described above. It is generally recognized
that conventional magnetic separation for such small partypical
impurities that can be removed during the magnetic
separation step include shale and impure trona with interstitial
dolomite and paramagnetic clay-type materials, which
have higher magnetic susceptibilities than pure trona. In
addition, other impurities may be separated by the present 5
process due to their association with the magnetic impurities.
As noted, any type of high intensity magnetic separator is
suitable for use in the present invention. More particularly,
either dry or wet high intensity magnetic separators can be
used. Dry separation refers to any process in which dry
particles are subjected to a high intensity magnetic field for
separation of magnetic impurities. Wet separation refers to
any process in which magnetic impurities are separated
from, e.g., crystals of a saline mineral in a saturated brine in
a high intensity magnetic field. Alternatively, the wet
medium can include other liquids, such as an alcohol.
Suitable high intensity magnetic separators can be of any
known design. For example, magnetic separators can be of
a type wherein a feedstream is fed in free fall in proximity
to a high intensity magnet so that magnetic particles tend to
migrate toward the magnet and non-magnetic particles do
not. In this manner, as the particles are collected on either
side of a splitter, the magnetic particles will physically
separate from the non-magnetic particles. With particular
regard to FIG. 9, a particular apparatus is illustrated. The
feedstream 10 is fed to a dropoff point 12 in free fall. At the
dropoff point 12, the feedstream is in close proximity to the
magnet 14. As the feedstream 10 falls, the magnetic particles
16 migrate toward the magnet 14 and the non-magnetic
particles 18 do not migrate toward the magnet 14. After the
particles are separated and fall further toward the splitter 20,
the magnetic particles 16 fall on one side of the splitter,
while the non-magnetic particles 18 fall on the other side of
the splitter 20. The horizontal distance between the dropoff
point 12 and the magnet 14 defines the gap width 22. The
horizontal distance between the splitter and a point on the
magnet face which is closest to the arc of the feedstream
defines the splitter gap width 24. The magnet angle 26 is
defined by the angle between the bottom surface of the
magnet and the horizontal. In an alternative high intensity
magnetic separator design for dry separations, particles can
be fed onto a matrix, such as a steel wool or wire mesh
screen matrix in proximity to a high intensity magnet. Such
a matrix can be made of any metal, such that in the presence
of a magnetic flux, the metal can act as a magnet. The metal
can be in any configuration having a high surface area such
as a wool or screen. The magnetic particles in the feed
stream will become attached to the matrix, whereas nonmagnetic
particles will migrate through the matrix and be
removed from the bottom of the matrix. This apparatus
design is particularly well suited for fine particles, such as
feedstreams having a particle size of less than 100 mesh.
In a further apparatus design for use with wet high
intensity magnetic separations, a matrix in a vessel filled
with a liquid is provided. The matrix is subjected to the
magnetic field of a high intensity magnet. The liquid can be,
for example, a saturated brine solution of a saline mineral.
For example, such a liquid can be from a saturated brine
recrystallization process, such as is described in PCT application
PCT/US96/00700, which is incorporated herein by
reference in its entirety. Such a stream can include the entire
size range of crystals generated by the process or can be
generated by separating large crystals from insoluble impurities
and smaller crystals on a size separation basis. The
resulting stream of a saturated brine solution with insoluble
impurities and small crystals can be treated by wet high
US 6,173,840 B1
7 8
density separation effect. For example, it has been found
that, in order to get adequate density separation using an air
table, the particle size distribution ratio should be about 3.0
or less, preferably about 2.8 or less, and more preferably
5 about 2.2 or less.
As discussed above, density separation is conducted by
subjecting the ore to conditions such that materials of
different densities separate from each other. The mineral
stream having materials of varying densities is separated by
10 a rougher pass into a denser and a lighter stream, or into
more than two streams of varying densities. Typically, in the
case of beneficiating trona, the separation is made at a
specific gravity of about 2.3, and trona is recovered in the
lighter stream. The purity of a saline mineral recovered from
15 density separation can be increased by reducing the weight
recovery of the recovered stream from the feed stream. At
lower weight recoveries, the recovered stream will have a
higher purity, but the rougher pass will also have a reduced
yield because more of the desired saline mineral will report
20 to the impurity stream. Such a "high purity" process may be
beneficial in that it requires less subsequent processing (e.g.,
separation) of the ore and, in addition, may be of higher
value because it can be used in other applications where high
purity saline minerals are required.
In an alternative embodiment, the impurity stream from
density separation can go through one or more scavenger
density separation step(s) to recover additional saline mineral
to improve the overall recovery. The scavenger separation
is similar to the above-described density separation
30 step. The scavenger step treats the impurity stream from the
rougher pass and recovers a portion of the saline mineral
therefrom. The recovered scavenger portion is combined
with the above-described recovered stream to increase the
overall recovery from density separation, or recycles it to
35 other steps in the process, with or without further size
reduction.
In a further alternative embodiment, the recovered stream
from the rougher pass density separation can go through one
40 or more cleaning density separation steps to further remove
impurities from the recovered stream and improve the purity
of the final product. The cleaning step is similar to the
above-described density separation process in that impurities
are removed from the stream by density separation. In
45 both scavenging and cleaning passes, the feed stream into
those passes can undergo further size reduction, if desired,
for example, to achieve higher liberation.
With regard to the beneficiation of trona, which, prior to
calcination, has a density of 2.14 and after calcination has an
50 apparent density of about 1.5, impurities that are removed
during the density separation step of the present invention
include shortite, having a density of 2.6, dolomite, having a
density of 2.8-2.9 and pyrite, having a density of 5.0. Each
of these is separable from the trona ore because of differ-
55 ences in density from trona. By practice of the present
invention, of the total amount of shortite, dolomite, pyrite
and, if present, potentially valuable heavy minerals in the
trona ore, the density separation step can remove at least
about 10 wt. % and more preferably, about 50 wt. %, and
60 most preferably, about 90 wt. % of the heavy impurity.
In an alternative embodiment, impurities removed during
the density separation process can be recovered as a product
for commercial use. For example, in the beneficiation of
trona, the impurities removed during the air tabling step can
65 comprise as much as 90% shortite. Such shortite may be
acceptable, for example, for certain applications where it can
be used for neutralization of acids or removal of sulfur from
ticles is not effective. It is believed that static charges on the
particles prevent effective separation between magnetic and
non-magnetic particles. In addition, it is believed that such
small particles do not efficiently separate because of a weak
magnetic force. However, such small particles can be effectively
separated by high intensity magnetic separation. High
intensity magnetic separators using a matrix, such as steel
wool, are believed to be particularly effective for such small
particles. Without intending to be bound by theory, it is
believed that the metal matrix functions to physically break
up associations between magnetic and non-magnetic particles.
In addition, it is believed that the metal matrix is able
to dissipate static charges which otherwise hold such particles
together. In this aspect of the invention, at least about
25 wt. % of magnetic impurities are separated from the -100
mesh particles, more preferably at least about 50 wt. %, and
most preferably at least about 75 wt. %.
Other processes may be utilized to practice the present
invention to selectively separate high and low purity portions
instead of ultra-high intensity magnetic separation. For
example, the process of selectively separating low purity
saline mineral from high purity saline mineral comprise
performing colorimetric separation. More specifically, for
example in the separation of trona, the low purity particles
may be separated based upon their darker color than the high 25
purity particles utilizing an automated colorimetric sorting
process. Such a process may utilize a video imager in
conjunction with appropriately-timed blasts of pressurized
gas to deflect the darker colored particles away from the high
purity particles.
The impurity stream from the selective separation step,
such as ultra-high intensity magnetic separation, can go
through one or more scavenger steps to improve the overall
recovery. The scavenger step recovers a portion of the
impurity stream from the rougher pass through magnetic
separation and combines it with the above-described recovered
stream or recycles it to the process with or without
further size reduction to increase the overall recovery of the
magnetic separation step. Furthermore, the recovered stream
from magnetic separation can go through one or more
magnetic cleaning steps to further remove impurities from
the recovered stream and improve the purity of the final
product.
The present process may further include removing impurities
from the ore containing saline minerals by a density
separation method. Density separation methods are based on
subjecting an ore to conditions such that materials of different
densities physically separate from each other.
Thereby, certain impurities having a different density than
the desired saline mineral can be separated. The density
separation step of the present invention is most preferably a
dry process; however, wet density separation processes,
such as heavy media separation, can be used as well. In dry
density separation processes, the need for processing in a
saturated brine solution, solid/brine separation, and drying
of the product is eliminated. Consequently, dry processes
according to the present invention tend to be cheaper and
less complex than wet processes. Any known density separation
technique could be used for this step of the present
invention, including air tabling or dry jigging.
During such dry separation steps, it is important to
maintain a narrow particle size distribution with a particular
fraction. That is, the ratio of the largest particle within a
fraction of the smallest particle within that fraction should
be relatively small. Without such a small ratio of particle
size distribution, the differences in particle sizes could tend
to dominate the separation process, thereby reducing the
US 6,173,840 B1
9 10
three size fractions of 6 mesh by 20 mesh, 20 mesh by 100
mesh, and minus 100 mesh, the two larger size fractions are
preferably treated using an apparatus in which particles free
fall while subject to a high intensity magnet and are col-
5 lected on either side of a splitter. Such an apparatus is also
known as an open gradient magnetic separator ("OGMS").
The smallest size fraction is preferably treated by a high
intensity magnetic separator having a metal matrix.
In yet another embodiment of the present invention, the
10 ore is dried prior to the separation processes set forth above.
The drying step removes surface moisture from the ore to
better enable the ore to be separated. Drying can be accomplished
by any conventional mineral drying technique,
including rotary kiln, fluid bed or air drying. The ore can be
dried to less than about 2%, and preferably less than about
15 1% surface moisture content. During the drying process, it
is preferred that the saline mineral is not raised to such a
temperature for such a period of time that it is calcined. In
the case of trona, the drying temperature should remain
below about 40 degrees centigrade to avoid calcination.
In still another embodiment of the present invention, a
de-dusting step is added to the basic beneficiation process to
remove fines before the selective separation step (e.g.,
magnetic separation). Such a de-dusting step can be conducted
before, during or after one or more of the crushing
25 and sizing steps, but preferably before the electrostatic
separation, magnetic separation and density separation
steps. The fines produced during the processing of trona are
relatively high purity trona and are useful in several industrial
applications. For example, trona recovered by
30 de-dusting can have a purity of greater than about 94%,
preferably greater than about 96% and more preferably
greater than about 98%. Fines can be collected in de-dusting
steps by use of a baghouse, or other conventional filtering
device, and sold as purified trona without further processing.
35 In a further aspect of the present invention, the magnetic
separation achieved by any magnetic separation step of the
present invention, including high intensity magnetic separation
and conventional intensity magnetic separation, can
be improved by subjecting the ore that is being processed to
a preliminary magnetic field prior to separation and subse-
40 quently separating a portion of impurities from the ore by
magnetic separation. Without being bound by theory, it is
believed that by subjecting particles being processed to a
preliminary magnetic field before physical separation of
magnetic from non-magnetic particles, the magnetic tractive
45 force on particles during magnetic separation is greater. In
this manner, more efficient separations can be achieved
during magnetic separation steps.
The term "preliminary magnetic field" refers to a magnetic
field to which a feed stream being processed is sub-
50 jected prior to physical separation of magnetic from nonmagnetic
particles. A feed stream being processed can be
subjected to a preliminary magnetic field using conventional
apparatus known to those in the art. For example, a feed
stream can be transported along a conveyor belt and sub-
55 jected to a magnetic field during linear transport on the
conveyor belt. Subsequently, particles will reach the end of
the conveyor belt and drop off of the conveyor belt while
being subjected to the primary magnetic field for separation.
In this embodiment of the present invention, the preliminary
magnetic field typically has a magnetic flux density of
60 greater than about 2000 Gauss, more preferably greater than
about 5000 Gauss, and most preferably greater than about
20,000 Gauss. Further, the step of subjecting particles to a
preliminary magnetic field is conducted for at least about 1
second, more preferably at least about 30 seconds, and most
65 preferably at least about 60 seconds. The positive effect of
a preliminary magnetic field can be further enhanced by
increased temperatures. More particularly, the process is
flue gases. In addition, for some trona deposits, potentially
valuable heavy minerals may be present. Such minerals can
be separated by the method and recovered.
It should be appreciated that the above-identified process
steps could be performed along with other process steps. For
example, such other process steps can include low or standard
intensity magnetic separation, electrostatic separation,
or any other suitable separation technique. In addition, the
above-identified process steps could be performed in any
order. Further, calcination can be conducted at any point in
the sequence of process steps and preferably is conducted
prior to any magnetic or density separation steps.
In a further embodiment of the present invention, the
saline mineral-containing ore can be crushed to achieve
liberation of impurities prior to the separation steps. The
crushing step of the present invention can be accomplished
by any conventional technique, including impact crushing
(e.g., cage or hammer mills), jaw crushing, roll crushing,
cone crushing, autogenous crushing or semi-autogenous
crushing. Autogenous and semi-autogenous crushing are
particularly beneficial because the coarse particles of ore 20
partially act as the crushing medium. Moreover, because
saline minerals are typically soft, these methods are suitable
for use in the present process. In addition, these two crushing
methods allow for the continuous removal of crushed material
and high grade potentially saleable dust.
In general, crushing to smaller particle size achieves
better liberation of impurities and thus improves recovery.
However, if the particle size after crushing is too fine, there
may be adverse effects upon subsequent separation steps. In
addition, over-crushing is not needed for many applications
of the present invention and merely increases the costs
associated with the crushing step. It has been found that
acceptable liberation for the present process can be achieved
by crushing the ore to at least about 6 mesh. Preferably, the
particle size range after crushing is from about 6 to about
100 mesh and, more preferably, from about 6 to about 65
mesh.
In another embodiment of the present invention, the ore is
sized into size fractions prior to the separation steps. Each
size fraction is subsequently processed separately. In
general, the narrower the range of particle size within a
fraction, the higher the efficiency of removal of impurities.
This is particularly true if air tabling is used as a density
separation step, wherein small particle size distribution
ratios are desired. On the other hand, a larger number of
fractions will increase the efficiency, but may increase the
cost of the overall process. The use of from 1 to 10 fractions
has been found to be acceptable. Preferably, the number of
fractions is from 4 to 10 and, more preferably, the number
of fractions is 8. Any conventional sizing technique can be
used for the present process, including screening or air
classification. For dividing into 8 fractions, the fractions
typically have the following particle size ranges: 6 to 8
mesh; 8 to 10 mesh; 10 to 14 mesh; 14 to 20 mesh; 20 to 28
mesh; 28 to 35 mesh; 35 to 48 mesh; 48 to 65 mesh (Tyler
mesh). Utilizing these fractions, the particle size distribution
ratio for each fraction is about 1.42. It should be noted that
a smaller number of size fractions, including only one size
fraction (such as 6 meshx100 mesh or 6 meshxO) or two size
fractions (such as 6 mesh by 20 mesh and 20 mesh by 0), can
be used for high intensity magnetic separations. Without
intending to be bound by theory, it is believed that the effects
of particle size are reduced under high intensity magnetic
separator apparatus designs. Thus, high intensity magnetic
separation can be conducted on a size fraction from 6 or 8
mesh by 20, 65 or 100 mesh.
In a further embodiment, the different size fractions can
be treated with high intensity magnetic separations using
different equipment. For example, in the instance of using
US 6,173,840 B1
11 12
EXAMPLES 1-8
Eight tests were performed on trona-containing ore in
accordance with the present invention. The tests were performed
on samples generated from ore mined from the
Green River Basin in Wyoming. The ore received was
crushed to nominal 50 mesh. The ore was screened into size
fractions, and the 20x35 fraction was used as the supply for
the eight tests. Referring to Table 1, the original 20x35
fraction comprised 94.01% soluble matter (i.e., trona) and
5.99% insoluble matter (i.e., impurities). The 20x35 fraction
was subjected to standard magnetic separation utilizing a
rare earth separator at its maximum intensity of less than
about 20,000 Gauss. The standard magnetic separation step
65 resulted in removal of 3.0% of the weight of the original
sample in a magnetic fraction, and the remaining nonmagnetic
fraction comprised 95.7% trona.
magnetic separation. For example, in a preferred
embodiment, the magnetic separation is conducted by feeding
ore onto a conveyor belt which then transports the ore
toward one end of the conveyor belt. The magnet creating
the first magnetic field is positioned in the rollers at the end
of the belt towards which the ore is transported. In this
manner, there will be one or more positions along the length
of the roller which have higher or maximum intensity of
magnetic force compared to other portions of the roller.
Thus, in order for the ore to be pre-aligned such that it is
primarily contacted with the portion of the roller having a
higher intensity magnetic field, it is necessary for the ore to
be aligned in the direction of travel of the belt in alignment
with the one or more positions of higher intensity. In this
embodiment, the step of pre-aligning can be accomplished
by a variety of means. For example, in the above example in
which an ore feed stream is fed onto a belt which is
transported toward a first end of the belt, pre-alignment can
be accomplished by subjecting the ore, for alignment purposes
only, to a second magnetic field in the vicinity of the
portion of the belt at which the ore is fed onto the belt. In this
manner, as ore particles are fed onto the belt and are settling
to a static position, magnetic particles will tend to migrate
and settle in alignment with one or more magnets placed
under the belt at the position desired for alignment. Thus, as
the ore is subsequently transported toward the end of the belt
toward the first magnetic field for purposes of magnetic
separation, the magnetic particles will be aligned with the
desired position of higher intensity of the first magnetic
field. Alternatively, alignment can be accomplished by
simple mechanical means of feeding the ore onto the belt at
one or more discrete locations across the width of the belt
such that as the belt is advanced, a line of ore is laid down
on the belt. Thus, alignment is accomplished by aligning the
discrete feed discharge point with the one or more positions
of higher intensity of the first magnetic field.
The foregoing process including pre-alignment of ore on
a surface for magnetic separation can be used alone or in
conjunction with other aspects of the present invention.
The foregoing description of the present invention has
been presented for purposes of illustration and description.
Furthermore, the description is not intended to limit the
invention to the form disclosed herein. Consequently, variations
and modifications commensurate with the above
teachings, and the skill or knowledge of the relevant art, are
within the scope of the present invention. The embodiment
described hereinabove is further intended to explain the best
mode known for practicing the invention and to enable
others skilled in the art to utilize the invention in such, or
other, embodiments and with various modifications required
by the particular applications or uses of the present invention.
It is intended that the appended claims be construed to
50 include alternative embodiments to the extent permitted by
the prior art.
conducted at temperatures of at least about 1000 c., more
preferably 1500 c., and most preferably 2000 C.
In a further embodiment of the present invention, a saline
mineral can be calcined prior to magnetic separation. More
particularly, in one aspect of this embodiment, the saline 5
mineral is calcined in an inert atmosphere prior to separating
impurities from the ore. In a second aspect of this
embodiment, the saline mineral is calcined in an oxidizing
atmosphere at a temperature of greater than about 1500 C.
prior to separating impurities from the ore. In this embodiment
of the present invention, it has been surprisingly found 10
that by calcination under the conditions identified above
(i.e., an inert atmosphere or an oxidizing atmosphere at high
temperature), the subsequent magnetic separation is more
efficient than in the absence of such calcining conditions.
As used herein, reference to the term "inert atmosphere" 15
refers to a non-oxidizing atmosphere (i.e., an atmosphere
substantially free of oxygen). More particularly, an inert
atmosphere is any non-oxygen containing atmosphere and in
particular, can comprise carbon dioxide, nitrogen, or water
vapor. In a further preferred embodiment, carbon dioxide
used for providing an inert atmosphere for calcination 20
purposes can be carbon dioxide which is recycled from an
exhaust stream from the calcination process. For example, in
the instance of calcination of trona, the byproducts of
calcination include carbon dioxide and water. Thus, the
water can be condensed from the exhaust stream and the 25
carbon dioxide recycled for use as the calcination gas, for
example, in a fluidizing bed.
When using an inert atmosphere in this embodiment, the
calcination temperatures typically range between about 430
C. and about 4000 c., more preferably between about 1000 30
C. and about 3500 c., and most preferably between about
1500 C. and about 2600 C.
In the aspect of this embodiment of the present invention
in which an oxidizing atmosphere is used during calcination,
the atmosphere most typically includes air but can include
other oxygen containing gases as well. Further, the calcina- 35
tion temperature in this aspect of the invention is at least
about 1500 c., more preferably at least about 2500 c., and
most preferably at least about 5000 C.
Subsequent to the calcination step as described above, the
saline mineral containing ore is then subjected to magnetic 40
separation. Such magnetic separation can include high intensity
magnetic separation as generally described herein, or
conventional intensity magnetic separation as described
herein and otherwise described in the art. In a further
preferred embodiment, the process of calcining saline min- 45
eral in an inert atmosphere or in an oxidizing atmosphere at
a high temperature followed by magnetic separation can also
include the step of subjecting the calcined ore to a preliminary
magnetic field prior to magnetic separation, as generally
described above.
A further embodiment of the present invention includes a
process for the purification of saline mineral by magnetic
separation in an ore comprising saline mineral and impurities.
In this embodiment, the magnetic separation is conducted
in a first magnetic field having positions of higher 55
intensity and lower intensity. The process includes prealigning
the ore on a surface with respect to one or more of
the positions of higher intensity of the first magnetic field
before separation of impurities and separating a first portion
of impurities from the ore by magnetic separation in the first
magnetic field. In this manner, higher efficiency of magnetic 60
separation is achieved because the ore is conducted through
the first magnetic field at the positions of highest magnetic
intensity. Therefore, magnetically susceptible particles are
subject to a higher magnetic tractive force and thereby are
more readily separated.
The manner in which the step of pre-aligning is conducted
will depend, in large part, upon the apparatus used for
US 6,173,840 B1
13 14
TABLE 1
Analysis of Original 20 x 35 Fraction from Trona Ore
Weight Water Insol. Water Soluble
Product
% of % of % of Assay Dist.
Feed Prod. * Spl. ** % Prod. *
Dist.
Spl**
Assay
%
Dist.
Prod.
Dist.
Spl.**
1.3
98.7
100.0
1.3
98.7
100.0
NOTE: The feed to the superconductor was processed with the International Process Systems RE
Belt Magnet, giving the following results:
3.0 3.0 60.3 30.2 30.2 39.7
97.0 97.0 4.31 69.8 69.8 95.7
100.0 100.0 5.99 100.0 100.0 94.01
Magnetic
Non-Mag.
Feed Calc.
*Feed to Separation as 100%
**Original Sample as 100%
The effectiveness of the 28,000 Gauss magnetic separation
in improving trona purity (i.e., compared to only using
20,000 Gauss magnetic separation) can be seen by comparing
the Water Soluble Assay % in the "Non Mag" row (i.e.
before density separation) to the Water Soluble Assay % in
the "Feed Calc" row.
The data generated from the foregoing beneficiation processes
is shown in Table 2. As can be seen from the Table,
the purity of trona in the final product (shown as Water
20 Soluble Assay %-2.3 Float) ranged from 97.20 in Tests 1
and 2 to 98.17 in Test 4. In addition, the recoveries (i.e., the
amount of final product divided by the amount of the
original sample, shown as Weight % of Spl.-2.3 Float) for
the whole process ranged from 67.1 in Test 4 to 95.0 in Test
25 1.
The non-magnetic fraction from the previous step was
then divided into seven (7) samples to be used in eight (8)
tests (test 8 was performed on the output from test 7). Each
of the eight (8) tests included a two-step separation process:
(1) magnetic separation at 28,000 Gauss; and (2) density
separation at 2.3 specific gravity on the non-magnetic fraction
from the previous step. The density separation was
performed with a heavy liquid which simulates density
separation with commercial air tables. The heavy liquid used
was a mixture of acetylene tetrabromide and kerosene.
Each of the first seven tests had essentially identical feed
compositions, and the input to the eighth test was the output
from the seventh test. The major difference between the tests 30
was the depth of the impurity cut. In general, the deeper the
cut, the higher the purity and the lower the recovery.
TABLE 2
Data From Second Series of Super Conducting Magnetic Separations
Feed 20 x 35 Mesh Non-Magnetic Ore
Weight Fe as Fe203 Water Insol. Water Soluble
Test #/ % of % of % of Assay Dist. Assay Dist., Dist. Assay Dist., Dist.
Product Feed Prod. Spl. % % % Prod. Spl. % Prod. Spl.
Test 1
Magnetic 1.0 0.9 1.44 17.1 57.3 13.0 9.1 42.7 0.4 0.4
Non-Mag. 100.0 99.0 96.1 82.9 3.74 87.0 60.7 96.26 99.6 98.3
2.3 Float 98.9 98.0 95.0 0.069 2.80 64.4 44.9 97.20 99.5 98.2
2.3 Sink 1.1 1.1 1.0 90 22.6 15.8 10 0.1 0.1
Feed Calc. 100.0 97.0 0.082 100.0 4.26 100.0 69.8 95.74 100.0 98.7
Test 2
Magnetic 1.3 1.3 1.27 19.7 50.4 15.3 10.7 49.6 0.7 0.7
Non-Mag. 100.0 98.7 95.7 80.3 3.66 84.7 59.1 96.34 99.3 98.1
2.3 Float 99.0 97.7 94.8 0.069 2.80 64.1 44.7 97.20 99.2 98.0
2.3 Sink 1.0 1.0 0.9 90 20.6 14.4 10 0.1 0.1
Feed Calc. 100.0 97.0 0.084 100.0 4.27 100.0 69.8 95.73 100.0 98.7
Test 3
Magnetic 7.3 7.1 0.53 42.5 19.0 32.6 22.7 81.0 6.2 6.1
Non-Mag. 100.0 92.7 89.9 57.5 3.10 67.4 47.1 96.90 93.8 92.6
2.3 Float 99.0 91.8 89.1 0.057 2.25 48.5 33.9 97.75 93.7 92.5
2.3 Sink 1.0 0.9 0.9 90 18.9 13.2 10 0.1 0.1
Feed Calc. 100.0 97.0 0.091 100.0 4.50 100.0 69.8 95.74 100.0 98.7
Test 4
Magnetic 30.3 29.4 0.20 65.1 8.88 60.2 42.0 91.1 28.9 28.5
Non-Mag. 100.0 69.7 67.6 34.9 2.56 39.8 27.8 97.44 71.1 70.2
2.3 Float 99.2 69.1 67.1 0.047 1.83 28.3 19.7 98.17 71.0 70.1
2.3 Sink 0.8 0.6 0.6 90 11.6 8.1 10 0.1 0.1
Feed Calc. 100.0 97.0 0.093 100.0 4.47 100.0 69.8 95.53 100.0 98.7
Test 5
Magnetic 12.0 11.6 0.40 49.5 14.9 41.0 28.6 85.1 10.7 10.5
US 6,173,840 B1
15 16
TABLE 2-continued
Data From Second Series of Super Conducting Magnetic Separations
Feed 20 x 35 Mesh Non-Magnetic Ore
Weight Fe as Fe203 Water Insol. Water Soluble
Test #/ % of % of % of Assay Dist. Assay Dist., Dist. Assay Dist., Dist.
Product Feed Prod. Spl. % % % Prod. Spl. % Prod. Spl.
Non-Mag. 100.0 88.0 85.4 50.5 2.93 59.0 41.2 97.07 89.3 88.2
2.3 Float 99.1 87.3 84.6 0.056 2.17 43.4 30.3 97.83 89.3 88.1
2.3 Sink 0.9 0.8 0.7 90 15.6 10.9 10 0.1 0.1
Feed Calc. 100.0 97.0 0.097 100.0 4.37 100.0 69.8 95.63 100.0 98.7
Test 6
Magnetic 3.5 3.4 0.91 35.3 32.2 50.1 18.2 67.8 2.5 2.4
Non-Mag. 100.0 96.5 93.6 64.7 3.30 73.9 51.6 96.70 97.5 96.3
2.3 Float 99.0 95.5 92.7 0.061 2.43 53.8 37.6 97.57 97.4 96.2
2.3 Sink 1.0 1.0 0.9 90 20.0 14.0 10 0.1 0.1
Feed Calc. 100.0 97.0 0.090 100.0 4.31 100.0 69.8 95.69 100.0 98.7
Test 7
Magnetic 8.0 7.8 0.54 45.5 18.9 35.0 24.4 81.1 6.8 6.7
Non-Mag. 100.0 92.0 89.2 54.5 3.06 65.0 45.4 96.94 93.2 92.0
2.3 Float 99.0 91.1 88.3 0.057 2.20 46.2 32.3 97.80 93.1 91.9
2.3 Sink 1.0 0.9 0.9 90 18.7 13.1 10 0.1 0.1
Feed Calc. 100.0 97.0 0.095 100.0 4.33 100.0 69.8 95.67 100.0 98.7
Test 8
Magnetic 4.4 4.3 0.30 23.8 11.3 17.6 8.0 88.7 4.4 4.0
Non-Mag. 100.0 87.6 84.9 76.2 2.67 82.4 37.4 97.33 95.6 88.0
2.3 Float 99.1 86.7 84.1 0.049 1.88 56.9 25.8 98.14 95.5 87.9
2.3 Sink 0.9 0.8 0.8 90 25.5 11.6 10 0.1 0.1
Feed Calc. 92.0 89.2 0.056 100.0 3.08 100.0 45.4 96.92 100.0 92.0
A summary of the tests results is provided in Table 3. The
Table gives the weight recovery of the overall process using
the original sample as 100% (Weight, %), the amount of
impurities in the final product (% H20 Insol), the amount of
iron as Fe20 3 in the final product (Fe2 0 3 , %), and the
amount of the original trona remaining in the final product
(Trona Dist., %).
TABLE 3
The process of Test #8 exceeds 98% purity, while still
having a recovery greater than 80%. This was accomplished
35 by performing a two-stage ultra-high intensity magnetic
separation. More specifically, the non-magnetic fraction
from test #7 was run through the ultra-high intensity magnetic
separation process a second time. The result is a
process which gives a purity almost as good as the best
results (test #4), with a satisfactory recovery.
40
Non- Distributions Based on 20 x 35 Mesh as 100%*
Summary of Non-Magnetic Product
From Superconducting Magnetic Separations
on 20 x 35 Mesh Non-Magnetic Trona Ore
*Air tabling simulated by heavy liquid separations (SG ~ 2.3) on NonMag.
**Non-Magnetic was not treated with heavy liquid.
***Calculated assay of calcined product based on assay of water insoluble
residue.
EXAMPLE 9
This example demonstrates that both pyrite and shortite
are magnetic.
Six examples of pyrite identified as P-l through P-6 and
two samples of shortite identified as S-1 and S-2 were
evaluated for magnetic susceptibility. A description of the
samples is provided below in Table 4.
TABLE 4
Pyrite From trona calcined at 1500 C.
Pyrite from trona calcined at 1500 C. and washed with
hydrochloric acid
Pyrite from uncalcined trona
Pyrite from an ore other than trona from Climax, Colorado
Trona from ore other than trona from Vulcan, Colorado
Pyrite from an ore other than trona from Argentina
Shortite from a non-magnetic fraction of uncalcined trona
Shortite from a magnetic fraction from a rare earth
magnetic separation of uncalcined trona
P-l
P-2
P-3
P-4
P-5
P-6
S-l
S-2
45
60
50
55
Weight, % H20 Fe20 3 , Trona Dist.,
% Sol*** %*** %
97.0 95.69** 0.09* * 98.7
95.0 97.20 0.069 98.2
94.8 97.20 0.069 98.0
89.1 97.75 0.057 92.5
67.1 98.17 0.047 70.1
84.6 97.83 0.056 88.1
92.7 97.57 0.061 96.2
88.3 97.80 0.057 91.9
84.1 98.14 0.049 87.9
Feed
Test #1
Test #2
Test #3
Test #4
Test #5
Test #6
Test #7
Test #8
Magnetic
From:
As can be seen from the values in Table 3, test #4 resulted
in excellent purity (98.17%), which is uncharacteristic of
most dry separation processes, while achieving moderate
recovery (67.1 %). Test #1 resulted in outstanding recovery
(95.0%) while still achieving a purity (97.2%) in excess of
97%. These two tests illustrate the excellent purities that can
be achieved by practicing the present invention.
The samples were all less than 1 mm in diameter. The
testing was done on a vibrating sample magnetometer having
a maximum field of 12 tesla. All data were gathered at
room temperature, with a time constant of 0.3 seconds and
65 ramping the magnetic field at 20 Oersted/sec. (to 0.4 tesla)
or 150 Oersted/sec. (to 2 tesla). Other than for strongly
magnetic samples (such as P-5), an appropriate background
US 6,173,840 B1
18
TABLE 7
Not Calcined in C02 at:
5 Calcined 1500 C. 3000 C. 4500 C. 600 0 C.
Water Insoluble 6.25 5.95 5.84 4.42 2.34
Assays - Non Mag.
Water Soluble 93.8 94.1 94.2 95.6 97.7
Assays - Non Mag.
10 Total Iron Assays 0.168 0.177 0.186 0.057 0.026
as Fe - Non Mag.
subtraction was performed. For the measurements on
samples P-5 and S-2, the materials were weighed and
wrapped with PTFE tape which was then formed into an
approximately spherical ball before packing into the sample
holder. The resulting ball of material was approximately 5
mm in diameter. The other samples, and also sample P-5,
were weighed into gelatin capsules and packed down with
cotton wool. The capsule was then locked into a sample
holder for measurement. The results of these tests are shown
below in Table 5 and in FIGS. 1-8. As can be seen from the
results, the magnetic properties of the samples varied from
diamagnetic through paramagnetic to weakly ferromagnetic.
17
TABLE 5
SUSCEPTI- SATURATION
MASS BILITY MOMENT
SAMPLE (g) emu/g. tesla emu/G. PROPERTY
Pl 0.1417 0.0128 paramagnetic
P2 0.1480 0.0038 paramagnetic
P3 0.1215 0.020 paramagnetic
P4 0.1135 0.032 ferromagnetic
P5 0.1263 0.058 ferromagnetic
(capsule)
P5 0.1777 0.060 ferromagnetic
(tape)
P6 0.1788 0.0056 paramagnetic
Sl 0.1357 0.00031 diamagnetic
S2 0.0784 0.0062 ferromagnetic
with hysteresis
EXAMPLE 10
The foregoing results illustrate that at higher temperatures
15 of calcination, significantly improved results in magnetic
separation is attained.
EXAMPLE 11
20 This example illustrates magnetic separation with high
intensity magnetic separation of impurities from calcined
trona which had previously been treated by two passes of
over a rare earth magnetic separator.
The initial product was prepared by calcining trona and
25 passing the calcined product over a rare earth magnetic
separator to yield magnetic fraction and a non-magnetic
fraction. The non-magnetic fraction was again passed over a
rare earth magnetic separator to yield a magnetic fraction
and a non-magnetic fraction. The non-magnetic fraction
30 from the second pass was used as the initial feed for this
experiment. The feed was tested using an OGMS superconducting
magnet set at 2 tesla. Four runs were conducted,
varying the feed rate, magnet angle and feed gap. The
parameters for each run are listed below in Table 8.
35
TABLE 9
Feed Water Insoluble Water Soluble Fe as Fe2 0 3
TABLE 8
Run Feed Rate Magnet Angle Feed Gap
Number (tph/m) (degrees) (em)
1 2.5 5 1
2 10 5 1
3 10 15 1
4 10 15 0.7
The magnetic and non-magnetic portions from each of
runs 1-4 were then analyzed for water insoluble and water
soluble contents, as well as for iron. In addition, each of the
non-magnetic and magnetic fractions from runs 1-4 were
examined to determine the mineralogy of each of the
samples. The results of the analytical testing and mineralogy
are shown below in Tables 9 and 10.
40
55
This example illustrates the effect of calcination temperature
on subsequent magnetic separation of impurities from
trona ore.
Trona ore was treated, in both air and in CO2 , by
calcination at 1500 c., 3000 c., 4500 c., or 6000 C. The trona
ore was treated by magnetic separation. A control was run on
trona with no calcining. Magnetic separation was conducted 45
on a rare earth roll magnet at about 20,000 Gauss. The
magnetic and non-magnetic fractions were then assayed for
water insoluble content (i.e., impurities) and for water
soluble content (i.e., sodium carbonate values). The magnetic
and non-magnetic fractions were also assayed for total 50
iron. The results of these experiments are shown below in
Table 6 (Calcination in Air) and Table 7 (Calcination in
CO2 ). All separations were done at same RPM and splitter
settings.
TABLE 6 Dist., Assay Dist.
Desc. % % %
Not Calcined in Air at:
Feed Sample 3.91
Calcined 1500 C. 3000 C. 4500 C. 600 0 C. 60
Run 1, 97.2 3.41 82.6
Non Mags
Water Insoluble 6.25 4.93 4.67 3.43 2.34 Run 1, Mags 2.8 24.99 17.4
Assays - Non Mag. Run 2, 91.1 3.16 75.2
Water Soluble 93.8 95.1 95.3 96.6 97.7 Non Mags
Assays - Non Mag. Run 2, Mags 8.9 10.58 24.8
Total Iron Assays 0.168 0.164 0.153 0.046 0.030 Run 3, 97.1 3.36 86.2
as Fe - Non Mag. 65 Non Mags
Run 3, Mags 2.9 17.94 13.8
Assay Dist. Assay Dist.
% % % %
96.09 0.114
96.59 97.6 0.083 86.1
75.01 2.2 0.472 13.9
96.84 91.7 0.159 87.0
89.42 8.3 0.242 13.0
96.62 97.5 0.079 87.0
82.06 2.5 0.394 13.0
US 6,173,840 B1
19
TABLE 9-continued
Feed Water Insoluble Water Soluble Fe as Fe20 3
5
Dist., Assay Dist. Assay Dist. Assay Dist.
Desc. % % % % % % %
Run 4, 97.0 3.29 83.7 96.71 97.5 0.104 86.1
10
Non Mags
Run 4, Mags 3.0 20.78 16.3 79.22 2.5 0.459 11.9
20
Mineralogy
TABLE lO-continued
Essentially all fine tan shale, minor
Shortite (less Shortite than Run 2, non-mags,
also some fine), Searlesite and dark brown
shale. Trace pyrite. Increase in dark brown
compact shale (15 to 10%)
Description
Run 4
Mags
25
This example illustrates the magnetic separation of impurities
from either trona or calcined trona using an OGMS.
Seventeen runs were conducted using a feedstream of
either trona or calcined trona calcined at 1500 C. The
30 feedstreams were either a size fraction of 6 mesh by 20 mesh
or 20 mesh by 100 mesh. The experimental setup varied the
gap width and the splitter gap width. The gap width is the
horizontal distance between the drop-off point of the feed
and the magnet. The splitter gap width is the horizontal
distance between the splitter and a point on the magnet face
35 which is closest to the arc of the feedstream. The separations
were conducted at a magnetic field strength of 4 tesla, with
a magnet angle of 11o.
The percentage of pyrite in the feed was calculated and,
for some runs, determined by analysis. In addition, the
40 percent pyrite in the non-magnetic fraction was analyzed. In
addition, the weight-percent recovery in the non-magnetic
fraction was calculated, as was the weight-percent recovery
of soluble material in the non-magnetic fraction.
The various gap and splitter gap widths as well as the
experimental results are shown below in Table 11.
The foregoing results demonstrate that at a magnet~c
strength of 2 tesla, an OGMS superconducting magnetlc
separator improved the purification of a non-magnetic fraction
from a rare earth magnetic separator with a high
recovery. Moreover, the mineralogical evaluation of the
15 sample showed that even at 2 tesla, some pyrite and shortite
showed up in the magnetic fraction. The use of high intensity
magnetic separation provided improved separation of impurities
compared to the use of rare earth magnetic separation
with the same size fraction and magnetic strength. The use
20 of an OGMS superconducting magnetic separator has the
advantage of eliminating centrifugal forces found with conventional
roll type magnetic separators. Centrifugal forces
can cause particles to report to the far side of the splitter due
to mass considerations rather than magnetic susceptibility.
EXAMPLE 12
Essentially all fine tan shale, minor
Shortite (less Shortite than Run 2, non-mags,
also some fine), searlesite and dark brown
shale. Trace pyrite.
Essentially all fine tan shale, minor
Shortite (less Shortite than Run 2, non-mags,
also some fine), Searlesite and dark brown
shale. Trace pyrite.
Mostly tan shale, subordinate dark brown
shale. Minor Shortite frequently inter grown
with dark brown shale, but also liberated.
Minor to trace northupite, fine grained
pyrite frequently inter grown with dark brown
shale. Trace Searlesite.
Essentially all fine tan shale, minor
Shortite, Searlesite and dark brown shale.
Trace pyrite.
Essentially all fine tan shale, minor
Shortite (less Shortite than Run 2, non-mags,
also some fine), Searlesite an dark brown
shale. Trace pyrite.
Essentially all fine tan shale, minor
Shortite (less Shortite than Run 2, non-mags,
also some fine), Searlesite and dark brown
shale. Trace pyrite.
Essentially all fine tan shale, minor
Shortite (less Shortite than Run 2, non-mags,
also some fine), Searlesite and dark brown
shale. Trace pyrite. Increase in dark brown
compact shale (15 to 10%)
Essentially all fine tan shale, minor
Shortite, Searlesite and dark brown shale.
Trace pyrite.
TABLE 10
Mineralogy
Run 1
Mags
Description
Run 1
Non Mags
Run 2
Non Mags
Run 3
Non Mags
Feed Sample
Run 3 Mags
Run 4
Non Mags
Run 2
Mags
TABLE 11
% Fe20 3 NM%
in feed Soluble
Size Test as as % Fe20 3 NM%wt H2O GAP SPLITTER
Material Mesh # anal. calc. inNM Rec. Rec. MM* GAPMM
Trona 6 x 20 1 N/A 0.39 0.15 89.7 96 15 16
Trona 6 x 20 2 N/A 0.31 0.19 93.5 99.4 20 18
Trona 6 x 20 3 N/A 0.34 0.11 80.6 89.8 15 32
Trona 6 x 20 4 0.31 0.32 0.1 89.7 97.4 15 16
Trona 6 x 20 5 0.31 0.37 0.12 44.9 49.5 15 25
Trona 6 x 20 6 0.31 0.38 0.13 85.1 93.5 15 22
Trona 20 x 100 7 0.82 0.97 0.2 50.6 56.9 15 24
Trona 20 x 100 8 0.82 0.47 0.23 92.3 95.4 15 21
Trona 20 x 100 9 0.82 0.94 0.35 96.7 96.5 25 18
Cal. 6 x 20 10 N/A 0.41 0.09 67.1 73.8 15 30
Trona
Cal. 6 x 20 11 N/A 0.41 0.11 81.6 87.9 15 25
Trona
Cal. 6 x 20 12 0.31 0.39 0.12 74.5 81.6 15 21
Trona
US 6,173,840 B1
21 22
TABLE ll-continued
% Fe20 3 NM%
in feed Soluble
Size Test as as % Fe20 3 NM%wt H2O GAP SPLITTER
Material Mesh # anal. calc. inNM Rec. Rec. MM* GAPMM
Cal. 6 x 20 13 0.31 0.29 0.14 88.6 95.6 15 25
Trona
Cal. 20 x 100 14 N/A 0.15 0.13 98.7 99.7 15
Trona
Cal. 20 x 100 15 N/A 0.15 0.1 95.7 97.9 15 30
Trona
Cal. 20 x 100 16 0.82 0.91 0.22 79.7 88.3 15 16
Trona
Cal. 20 x 100 17 0.82 1.1 0.24 86.6 94.2 15 15
Trona
The samples from each of the runs were weighed and
analyzed for insoluble material. The insoluble material was
analyzed by microscopic examination and by chemical
analysis. The analytical results for this example are shown in
Tables 13 and 14. These test results show that using high
intensity magnetic separation with a metal matrix makes
separations of finer size fractions possible. Conventional
technology only permits narrow size ranges to be separated
to a level of purity that was achieved with use of high
intensity magnetic separation in a matrix material using a
large size range (20x100 mesh). Also, the separation of
material of less than 150 mesh is now possible when
conventional rare earth and induced roll magnetic separation
cannot process those size fractions.
35
The next three samples were recovered by reducing the
20 magnetic field from 3 to 2 tesla, from 2 to 1 tesla, and from
1 to 0 tesla. A final magnetic sample was recovered by
shaking the unit at 0 tesla.
Run 3 was conducted to determine whether a second pass
through the magnetic separator would improve the purity of
25 the non-magnetic fraction. A feedstream of about 150 g was
used.
Run 4 was similar to Run 2, except that calcined trona was
used instead of trona. In addition, instead of ten portions of
100 g, Run 4 included five samples of 160 g. Further, the
30 magnetic samples included a division of the 5-3 tesla sample
into a 5-4 tesla and a 4-3 tesla sample.
Run 5 was conducted to confirm the results obtained from
Run 4 and determine repeatability of the test method.
Run 6 used the heavy portion of a density separation of
calcined trona. The heavy portion of such a density separation
included a large percentage of shortite, shale and pyrite.
Thus, the feed material is enriched in these impurities. A
feedstream of 200 g of this material was used. However, the
40 matrix became blocked as a result of the coarse nature of the
feed material.
Run 7 repeated Run 6 except that a higher frequency on
the vibrator was used to allow all of the feed material to pass
through the matrix.
Run 8 repeated Run 7 but less feed material (i.e., 100 g of
feed material) was used. After the first pass, the magnetic
fraction was removed from the matrix before running the
non-magnetic fraction through for a second pass.
Run 9 was conducted to evaluate the effect of magnetic
separation on very fine material. Due to the poor flow
characteristics of this feed material, the matrix became
blocked.
TABLE 12
Run Size Range
Number Type Material (Tyler Mesh)
1 T-50 Calcined Trona 100 x 150
2&3 T-50 Trona 20 x 150
T-50 Calcined Trona 20 x 150
6,7 & 8 Air Table Heavies Calcined Trona 28 x 35
9 T-50 Calcined Trona 100 x 0
These results show a separation using high intensity magnetic
separation, such as OGMS, can, with a wide size
fraction (e.g., 6x20 mesh or 20x100 mesh), produce equal or
better purification when compared to conventional magnetic
separation using multiple narrow size factions (e.g., lx8
mesh, 8xlO mesh, lOx20 mesh, etc.).
EXAMPLE 13
The feedstream was introduced at a feed rate of 25 cm3 Is. 45
The magnetic field was set at 5 tesla. The matrix material in
this test was an expanded metal matrix having a matrix size
of Y4 inch. Non-magnetic material exited the bottom of the
unit while the magnetic fraction was held in the matrix.
Run 1 was conducted to determine the effect of vibration 50
on the flow of material through the magnetic separator. The
frequency of a vibrator of the matrix was varied from 40 HZ
to 25 HZ, and then 10 HZ. Approximately 100 g of feed was
fed through at each frequency setting. The non-magnetic
fraction from each run was collected and the final magnetic 55
fraction from the total of the three settings was also collected.
Run 2 was conducted to evaluate the capacity of the
matrix and how the purity of the non-magnetic fraction was
affected as the matrix was loaded up with a magnetic 60
fraction. The magnetic separator was fed 100 g of feedstream
at a time until 1000 g had been run through the matrix
without removing any magnetic fraction from the matrix.
After the last 100 g had been run through the matrix, the
magnetic fraction was removed from the matrix by ramping 65
down the magnetic coil in tesla increments. The first sample
was produced by reducing the field from 5 tesla to 3 tesla.
This example illustrates the use of magnetic separation of
impurities from soda ash or trona using a superconducting
magnet with a metal matrix to remove impurities from a dry
feedstream.
Nine test runs were conducted in this experiment. The
feed material for each test run is described below in Table
12.
TABLE 13
Analytieal Test Results on a Soda Ash Basis
Water
Sample Feed Insoluble, (%) Water Soluble, (%) Fe as Fe20" (%) Ca as CaO, (%) Mg as MgO, (%) K as K2 0, (%) Al as A120" (%) Si as Si02 , (%) Total S as S, (%)
# Description Dist. % Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist.
Calcined Trona
la Run 1, Feed 3.06 96.94 0.115
N~
Sample
Ib Run 1, 40 HZ 25.6 1.67 14.1 98.33 25.9 0.024 5.4
Non Mags
Ie Run 1, 25 HZ 30.1 1.74 17.3 98.26 30.5 0.026 6.9
Non Mags
Id Run 1, 10 HZ 40.3 1.82 24.3 98.18 40.8 0.029 10.1
Non Mags
Ie Run 1, Mags 2.8 46.40 43.4 53.60 1.6 2.960 72.4
If Run 1, Mags 1.2 2.02 0.8 97.98 1.2 0.115 5.3 0.022 e Cleanout
4a,5a Runs 4 and 5 6.22 93.78 0.153 1.06 0.61 0.21 0.081 C/J
Feed Sample vO\
4b Run 4, 1st Non 17.8 2.82 7.4 97.18 18.6 0.080 8.4 0.59 0.17 0.04 f-l.
Mag -..l
W 4e Run 4, 2nd Non 18.4 2.99 8.1 97.01 19.2 0.059 6.4 00 Mag ~
4d Run 4, 3rd Non 18.3 3.11 8.4 96.89 19.0 0.059 6.4 0
Mag 4e Run 4, 4th Non 18.3 3.20 8.7 98.80 19.0 0.068 7.3 OJ f-l.
Mag
4f Run 4, 5th Non 18.2 3.48 9.4 96.52 18.8 0.077 8.2
Mag
4g Run 4, Mag 0 1.1 35.26 5.7 64.74 0.8 1.128 7.2 4.23 3.67 1.39 2.10 10.51 0.681
Tesla Shake
4h Run 4, 3.7 58.86 31.8 41.14 1.6 1.672 36.1 6.89 6.59 2.58 0.854
Mag 1-0 Tesla
4i Run 4, 2.0 42.26 12.3 57.74 1.2 1.069 12.4 5.03 4.48 1.80 0.562
Mag 2-1 Tesla
4j Run 4, 0.9 54.96 7.1 45.04 0.4 1.292 6.6 6.87 5.25 2.02 0.747 N
Mag 3-2 Tesla ~
4k Run 4, 1.1 5.74 0.9 94.26 1.1 0.148 0.9 0.90 0.44 0.15 0.093
Mag 4-3 Tesla
41 Run 4, 0.3 4.25 0.2 95.75 0.3 0.060
Mag 5-4 Tesla
5b Run 5, Non Mag 88.8 2.94 41.1 97.06 92.0 0.056 31.4
5e Run 5, Mag 11.2 33.33 58.9 66.67 8.0 0.977 68.6
6a,7a, Runs 6, 7, 8 40.48 59.52 0.963 8.34 3.04
8a Feed Sample
6b Run 6, Non Mag 28.2 23.01 16.2 76.99 36.2 0.235 7.3 7.64 27.2 0.34 3.2
6e Run 6, Mag 71.8 46.67 83.8 53.33 63.8 1.176 92.7 8.03 72.8 4.01 96.8
7b Run 7, Non Mag 66.9 24.39 40.1 75.61 85.2 0.249 17.8 8.20 66.6 0.33 7.5
TABLE 13-continued
Analytical Test Results on a Soda Ash Basis
Water
Sample Feed Insoluble, (%) Water Soluble, (%) Fe as Fep" (%) Ca as CaO, (%) Mg as MgO, (%) K as Kp, (%) Al as Alp" (%) Si as SiOh (%) Total S as S, (%)
# Description Dist. % Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist.
7c Run 1, Mag 33.1 73.43 59.9 26.57 14.8 2.313 82.2 8.30 33.4 8.30 92.5
8b Run 8, Non Mag 59.2 22.43 33.7 77.57 75.7 0.185 11.3 7.49 0.29
after 2nd Pass
8c Run 8, Mag after 34.4 70.99 62.1 29.01 16.5 2.194 78.4 7.95 7.88 N
1 Pass
Ul
8d Run 8, Mag after 6.4 25.41 4.1 14.59 7.9 1.540 10.2
2nd Pass
9a Run 9, 93.4 8.37 95.9 91.63 93.2 0.187 96.8
Feed Sample
9b Run 9, 6.6 5.08 4.1 94.92 6.8 0.087 3.2
Non Mag
Trona ---
2a,3a Runs 2, 3 8.34 91.66 0.221 1.47 0.66 0.23 0.35 1.89 0.147 e
Feed Sample C/J
2b Run 2, 1st Non 8.3 4.17 4.2 95.83 8.6 0.085 3.1 1.07 0.20 0.05 0.08 0.61 0.059 vO\
Mag f-l.
2c Run 2, 2nd Non 8.9 4.06 4.5 95.94 9.3 0.094 3.7 -..l
Mag W
2d Run 2, 3rd Non 9.1 4.19 4.7 95.81 9.5 0.097 3.9 00
Mag ~
2e Run 2, 4th Non 9.1 4.08 4.5 95.92 9.5 0.100 4.0
0
Mag OJ
2f Run 2, 5th Non 9.0 4.29 4.8 95.71 9.4 0.108 4.3 f-l.
Mag
2g Run 2, 6th Non 9.2 4.33 4.9 95.67 9.6 0.113 4.6
Mag
2h Run 2, 7th Non 9.2 4.36 4.9 95.64 9.5 0.116 4.7
Mag
2i Run 2, 8th Non 9.0 4.43 4.9 95.57 9.4 0.117 4.7
Mag
2j Run 9th Non 8.9 4.82 5.3 95.18 9.3 0.142 5.6
Mag N
2k Run 2, 10th Non 8.9 5.26 5.7 94.74 9.2 0.146 5.7 0'1
Mag
21 Run 2, Mag 0 2.6 40.63 12.7 59.37 1.6 1.329 15.0 4.83 3.92 1.54 2.41 12.39 0.825
Tesla Shake
2m Run 2, Mag 0 3.8 57.44 26.9 42.56 1.8 1.660 27.9 6.72 5.80 2.31 3.56 17.52 0.988
Tesla
2n Run 2, Mag 2-1 2.3 33.45 9.4 66.55 1.7 0.937 9.5 3.95 3.17 1.27 1.92 9.93 0.559
Tesla
20 Run 2, Mag 3-2 0.8 15.59 1.5 84.41 0.7 0.536 1.8 0.329
Tesla
2p Run 2, Mag 5-3 0.9 8.85 1.0 91.14 0.9 0.377 1.5 0.199
Tesla
Sample
TABLE 13-continued
Analytical Test Results on a Soda Ash Basis
Water
Feed Insoluble, (%) Water Soluble, (%) Fe as Fep" (%) Ca as CaO, (%) Mg as MgO, (%) K as Kp, (%) Al as Alp" (%) Si as SiOh (%) Total S as S, (%)
# Description Dist. % Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist.
3b
3c
3c
Run 3, Non Mag
after 1 Pass
Run 3, Non Mag
after 2nd Pass
Run 3, Mag after
2nd Pass
15.9
67.9
16.2
4.22 8.5
3.83 32.8
28.90 58.8
95.78
96.17
71.10
16.5
71.0
12.5
0.084
0.077
1.087
5.5
21.7
72.8
0.98
3.53
0.17
2.95
0.05
1.16
0.07 0.51
0.054
0.052
N
-..J
N
QIO
e
C/J
vO\
f-l.
-..l
W
00
~o
OJ
f-l.
29
US 6,173,840 B1
TABLE 14
Mineralogy of Test Samples
30
Sample # Description
Calcined Trona
1a Run 1, Feed Sample
1b Run 1, 40 HZ Non Mags
1c Run 1, 25 HZ Non Mags
1d Run 1, 10 HZ Non Mags
1e Run 1, Mags
1f Run 1, Mags Cleanout
4a,5a Runs 4 and 5
4b Run 4, 1st Non Mag
4c Run 4, 2nd Non Mag
4d Run 4, 3rd Non Mag
4e Run 4, 4th Non Mag
4f Run 4, 5th Non Mag
4g Run 4, Mag 0
Tesla Shake
4h Run 4,
Mag 1-0 Tesla
4i Run 4,
Mag 2-1 Tesla
4j Run 4,
Mag 3-2 Tesla
4k Run 4,
Mag 4-3 Tesla
41 Run 4,
Mag 5-4 Tesla
5b Run 5, Non Mag
5c Run 5, Mag
6a, 7a, 8a Runs 6, 7, 8
Feed Sample
6b Run 6, Non Mag
6c Run 6, Mag
7b Run 7, Non Mag
8b Run 6, Non Mag after
2nd Pass
8c Run 8, Mag after 1 Pass
8d Run 8, Mag after
9a Run 9. Feed Sample
9b Run 9, Non Mag
Trona
2a,3a Runs 2, 3
Feed Sample
2b Run 2, 1st Non Mag
2c Run 2, 2nd Non Mag
2d Run 2, 3rd Non Mag
Mineralogy
Mostly fine shale and shortite, minor to trace sepiolite, northupite, searlesite, fairly abundant tarnished pyrite.
Mostly fine shale and shortite, minor to trace sepiolite, northupite, searlesite. No obvious pyrite
Mostly fine shale and shortite, minor to trace sepiolite, northupite, searlesite. Trace pyrite.
Mostly fine shale and shortite, minor to trace sepiolite, northupite, searlesite. Trace very fine pyrite.
Quite different. Mostly compact but fine tan-greenish shale not powdery like fine shale in other samples. Also,
abundant fine compact dark brown shale. Abundant northupite, minor shortite, trace pyrite and searlesite.
Mostly shartite (60 to 70%) and fine tan shale with subordinate strongly magnetic "rust" particles with fused
appearing surfaces. Minor (1 to 3%) pyrite with highly tarnished surfaces, narthupite, both discrete and admixed
with shale (dolomite) and sepiolite.
Mostly fine tan shale and subordinate shortite and dark brown compact shale (appreciably mare than
in Sample #4b). Minar to trace pyrite (more than Sample #4b) and searlesite.
Mostly fine shale and much coarse shortite. Subordinate to minor dark brown particulate shale. Trace
searlesite and pyrite.
Mostly fine shale and much coarse shortite. Subordinate to minor dark brown particulate shale. Trace
searlesite and pyrite.
Mostly fine shale and much coarse shortite, but less than previous sample. Subordinate to minor dark brown
particulate shale. Trace searlesite and pyrite.
Mostly fine shale and much coarse shortite. Subordinate to minor dark brown particulate shale. Trace
searlesite and pyrite.
Mostly fine shale and much coarse shortite. Subordinate to minor dark brown particulate shale. Trace
searlesite and pyrite.
Virtually all shale, tan more abundant than dark brown. Both contain admixed northupite. Minar sepiotite and
shartite and traces of searlesite, sugary northupite and pyrite both liberated and locked with shale. Pyrite
appears fresh. Possibly more shortite than Sample #4i.
Virtually all shale, tan more abundant than dark brown. Both contain admixed northupite. Minar sepiolite and
shartite and traces of searlesite, sugary northupite and pyrite both liberated and locked with shale.
Pyrite appears fresh with slightly more tarnished pyrite. Possibly less shortite than Sample #4i.
Virtually all shale, tan more abundant than dark brown. Both contain admixed northupite. Minar sepiolite and
shartite and traces of searlesite, sugary northupite and pyrite both liberated and locked with shale. Pyrite
appears fresh.
Virtually all shale, tan more abundant than dark brown. Both contain admixed northupite. Minar sepiolite and
shartlife and traces of searlesite, sugary narthupite and pyrite both liberated and locked with shale. Pyrite
appears fresh.
Majarity is shale (both types) and ± 30% shortite and minor searlesite (more than Sample #4i). Both shales
contain admixed northupite. Also more sepiolite than Sample #4i. Traces of searlesite, sugary
northupite and pyrite both liberated and locked with shale. Pyrite appears fresh.
Majarity is shale (both types) and 40 to 50% shartite and minar searlesite (mare than Sample #4i). Both shales
contain admixed northupite. Also more sepiolite than Sample #4i. Sepiolite conspicuous causing
more tangled up lumps. Traces of searlesite, sugary northupite and pyrite both liberated and locked with shale.
Pyrite appears fresh.
Mostly fine shale and much coarse shortite. Subordinate to minor dark brown particulate shale. Trace searlesite
and pyrite.
Distinctly different from Sample #5b. Predominantly (60 to 70%) tan-greenish compact relatively coarse shale and
and 30 to 40% dark brown compact shale. Minar (2-3%) shortite and trace pyrite, fairly frequently locked with
dark brown compact shale, searlesite and sepiolite.
About 60 to 70% shortite, balance tan-greenish shale (both compact cellular and fine) and dark brown compact
shale and 1% pyrite mostly as liberated cubes, less frequently lock with dark brown shale.
About 90 to 95% shortite, balance mostly fine tan shale, 1% liberated and locked (with shortite) pyrite. Some
pyrite is tarnished. Trace searlesite.
About 60% shale, mostly tan-greenish compact, less dark brown compact, 40% shortite, 1% pyrite.
About 90 to 95% shortite, balance mostly fine tan shale. About 0.5 to 1% pyrite mostly as liberated cubes, less
commonly locked with shortite.
Mostly shartite (90 to 95%), balance mostly fine tan shale. Trace (5 to 1%) pyrite and searlesite.
Mostly compact fairly coarse tan-greenish shale (80%), 10% dark brown compact shale, 10% shortite. 1% pyrite
both relatively coarse liberated cubes, also tarnished fragments and frequently locked with dark brown
compact shale.
Predominantly shartite (80%), subardinate fine shale and northupite and minar pyrite (3 to 5%). The pyrite is
slightly tarnished and is mostly liberated but also frequently locked with shale and shartite.
Mostly fine tan shale and rather fine shortite, subordinate dark brown compact shale. Trace pyrite and
searlesite.
Predominantly shartite (60 to 70%), subordinate fine shale and about 10% strongly magnetic fused appearing
"rust". Minar searlesite, northupite and pyrite (1% ar less). Similar to Sample #1f.
Mostly shartite and shale (both fine tan an particulate dark brown), minor searlesite, narthupite, sepiolite and
pyrite.
Mostly shortite and tan fine shale. Dark brown particulate almost absent. Minor searlesite, northupite, sepiolite
and pyrite. Pyrite reduced compared to Sample #2a, 3a.
Mostly shartite and tan fine shale. Dark brown particulate almost absent, but slight increase over Sample #2b.
Minor searlesite, northupite, sepiolite and pyrite. Pyrite reduced compared to Sample #2a, 3a.
Mostly shartite and tan fine shale. Dark brown particulate almost absent, but slight increase over Sample #2b.
Minor searlesite, northupite, sepiolite and pyrite. Pyrite reduced compared to Sample #2a, 3a.
US 6,173,840 B1
31 32
TABLE 14-continued
Mineralogy of Test Samples
Sample # Description
2e Run 2, 4th Non Mag
2f Run 2, 5th Non Mag
2g Run 2, 6th Non Mag
2h Run 2, 7th Non Mag
2i Run 2, 8th Non Mag
2j Run 2, 9th Non Mag
2k Run 2, 10th Non Mag
21 Run 2, Mag 0
Tesla Shake
2m Run 2, Mag 0 Tesla
2n Run 2, Mag 2-1 Tesla
20 Run 2, Mag 3-2 Tesla
2p Run 2, Mag 5-3 Tesla
3b Run 3, Non Mag after
1 Pass
3c Run 3, Non Mag after
2nd Pass
3d Run 3, Mag after
2nd Pass
Mineralogy
Mostly shartite and tan fine shale. Dark brown particulate almost absent, but slight increase over Sample #2b.
Minor searlesite, northupite, sepiolite and pyrite. Pyrite reduced compared to Sample #2a, 3a.
Mostly shartite and tan fine shale. Dark brown particulate almost absent, but slight increase over Sample #2b.
Minor searlesite, northupite, sepiolite and pyrite. Pyrite reduced compared to Sample #2a, 3a, but possibly
slight increase in pyrite over Sample #2c.
Mostly shartite and tan fine shale. Dark brown particulate almost absent, but slight increase over Sample #2b.
Minor searlesite, northupite, sepiolite and pyrite. Pyrite reduced compared to Sample #2a, 3a.
Mostly shartite and tan fine shale. Dark brown particulate almost absent, but slight increase over Sample #2b.
Minor searlesite, northupite, sepiolite and pyrite. Pyrite reduced compared to Sample #2a, 3a.
Mostly shartite and tan fine shale. Dark brown particulate almost absent, but slight increase over Sample #2b.
Minor searlesite, northupite, sepiolite and pyrite. Pyrite reduced compared to Sample #2a, 3a.
Significant increase in shartite (60 to 70%) and some increase in dark brown particulate shale compared to
Sample
#2i. Minor searlestite, northupite, sepiolite and pyrite. Pyrite reduced compared to Sample #2a, 3a, but
slight increase over Sample #2e.
Significant increase in shartite (60 to 70%) and some increase in dark brown particulate shale compared to
Sample
#2i. Minor searlestite, northupite, sepiolite and pyrite. Pyrite decreased to trace.
Mostly shale (60% tan greenish, now particulate and mostly finer and 40% dark brown particulate), trace shartite,
searlesite, sepiolit3 and pyrite. The maj arity of the pyrite occurs locked in dark brown particulate shale with a
litle more liberated pyrite.
Mostly shale (60% tan greenish, now particulate and 40% dark brown particulate), trace shortite, searlesite,
sepiolite and pyrite. The majarity of the pyrite occurs locked in dark brown particulate shale.
Roughly 1:1 mixture of tan-greenish particulate and dark brown particulate shale. Quite coarse grained. Trace
shartite (liberated), searlesite4 and pyrite mostly locked with dark brown shale and rarely liberated.
Roughly 1:1 mixture of tan-greenish particulate and dark brown particulate shale. Tan-greenish shale more
cellular as though derived from trona interslices. Quite coarse grained. Slightly more shartite (liberated),
searlesite and slightly more pyrite and sepiolite.
Shortite 40%, balance tan-greenish cellular and dark brown particulate shale. Minar pyrite (1 %) and minor to
trace searlesite and sepiolite.
Shortite 70%, balance mostly fine tan-greenish shale. Minar searlesite, northupite, sepiolite and mostly
liberated pyrite (2 to 3%).
Mostly shartite and fine dispersed tan-greenish shale. Dark brown particulate almost absent. Minor
searlesite, northupite, and sepiolite. Trace liberated pyrite.
About 70% compact tan-greenish shale, 25% dark brown compact shale, 3 to 5% shortite, 2 to 3% pyrite,
some as coarse liberated cubes and fragments and frequently finely locked with dark brown compact shale.
Trace searlestite and sepiolite.
EXAMPLE 14
40 TABLE 16
Run Size Range
Number Slurry Type Prescreened (Tyler Mesh 60
1,2 & 3 calcined trona Yes 100 x 150
4 calcined trona No 20 x 100
5 filter cake No 100 x 0
Test Parameters
Magnetic Matrix
Run Feed Rate Field Matrix Matrix Size Diameter
Number (cm3 /s) (tesla) Material (mm) (mm)
1 25 5 Square Wire 2.5 64
2 25 5 Square Wire 1.0 & 1.7 64
3 25 5 Steel Wool 110* 64
4 25 5 Square Wire 2.5 64
5 25 5 Square Wire 1.0 & 1.7 64
*Microns, not millimeters
65
45
The test material was fed into the unit and flowed through
the matrix in a 5 tesla magnetic field. No vibrator of the
apparatus was used. The non-magnetic material exited the
55 bottom of the unit while the magnetic fraction was held in
the matrix. The current was ramped down to 0, reducing the
magnetic field to o. When the magnetic field was at 0, the
matrix was flushed with water to remove any magnetic
material that was still adhering to the matrix and internal
ledges. It was necessary to preheat the magnetic separator
unit and matrix material to prevent crystals from forming in
the matrix. The recovered samples were diluted with water
to remove any crystals that formed during the run and then
filtered on 1 micron filter paper to remove insolubles.
In Run 1, a 2.5 mm square wire matrix was used.
In Run 2, a matrix composed of alternating pieces of 1.7
mm and 1.0 mm square wire material was used.
Feed Material
TABLE 15
The feed material for four test runs of this example was
produced by dissolving about 6,000 g of soda ash prepared
by calcining trona in 4 gallons of warm water. This slurry
was screened at 100 mesh to remove the +100 mesh
50
insolubles. A fifth test run slurry was made by dissolving
filter cake from a sodium carbonate recrystallization process
to make a saturated -100 mesh insolubles slurry. The feed
materials for this example are shown in Table 15.
The test parameters in terms of feed rate, magnetic field and
matrix material are shown in Table 16.
This example illustrates the use of magnetic separation
using a superconducting magnetic separator process having
a metal matrix for capture of particles wherein the feedstream
is a wet slurry.
US 6,173,840 B1
33 34
TABLE 19-continued
Mineralogy
Mineralogy of Test Samples
Essentially all fine tan shale with a small amount
of dark brown shale, traces of searlesite, fine
pyrite, etc. Slight increase in pyrite compared to
Run 1 Non Mag.
Essentially all fine tan shale, traces of
searlesite, fine pyrite, etc.
Essentially all fine tan shale, traces of
searlesite, fine pyrite, etc.
Description
Run 3 Mag
Run 3 Non Mag
10 Run 4
Run 5 Non Mag
In Run 3, the non-magnetic product from Run 2 was used
as the feed. The matrix was changed to a 110 micron steel
wool.
In Run 4, a 2.5 mm square wire material was used as a
matrix. The feed material included the +100 mesh 5
insolubles, that had previously been screened out of the
slurry in Runs 1, 2 and 3. The matrix plugged at the
beginning of the run.
Run 5 included alternating pieces of a 1.7 mm and a 1.0
mm square wire material as the matrix.
The insoluble materials recovered from the various runs
were analyzed by microscopic examination and chemical
analysis. The results of these analyses are provided in Tables
17, 18 and 19.
TABLE 17
Analytical Test Results on an Insoluble Basis
Water insoluble, Water Soluble,
(%) (%) Fe as Fe2 0 3 • (%) Ca as CaO. (%) Mg as MgO. (%) K as K2 0. (%) Total S as S. (%)
Description Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist.
Run 1 45.5 1.660 38.9 13.60 46.0 10.10 39.5 3.60 46.2 0.159 23.3
Non Mag
Run 1 54.5 2.180 61.1 13.30 54.0 12.90 60.5 3.50 53.8 0.436 76.7
Mag
Run 2 64.4 1.870 69.6 13.20 63.8 12.60 73.1 3.75 68.5 0.332 71.6
Mag
Run 3 19.9 1.320 15.2 13.50 20.2 6.89 12.4 3.43 19.4 0.161 10.7
Non Mag
Run 3 15.7 1.670 15.2 13.50 16.0 10.20 14.5 2.70 12.1 0.334 17.6
Mag
Run 4
Run 5 79.8 1.470 68.0 19.40 82.0 7.74 77.1 2.70 79.6 0.363 51.0
Non Mag
Run 5 20.2 2.740 32.0 16.80 18.0 9.11 22.9 2.74 20.4 1.380 49.0
Mag
TABLE 18
Cryo Filter Analytical Test Results on a Soda Ash Basis
Water insoluble, Water Soluble,
(%) (%) Fe as Fe2 0 3 • (%) Ca as CaO. (%) Mg as MgO. (%) Kas Kp. (%) Total S as S. (%)
Description Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist. Assay Dist.
Run 1 3.67 45.5 96.3 90.0 0.061 38.9 0.50 46.0 0.37 39.5 0.13 46.2 0.006 23.3
Non Mag
Run 1 29.09 54.5 70.9 10.0 0.634 61.1 3.87 54.0 3.75 60.5 1.02 53.8 0.127 76.7
Mag
Run 2 19.77 64.4 80.2 8.0 0.370 69.6 2.61 63.8 2.49 73.1 0.74 68.5 0.066 71.6
Mag
Run 3 1.64 19.9 98.4 90.0 0.022 15.2 0.22 20.2 0.11 12.4 0.06 19.4 0.003 10.7
Non Mag
Run 3 1.45 15.7 98.5 2.0 0.024 15.2 0.20 16.0 0.15 14.5 0.04 12.1 0.005 17.6
Mag
55
TABLE 19 TABLE 19-continued
Mineralogy of Test Samples Mineralogy of Test Samples
Description Mineralogy 60
Description Mineralogy
Run 1 Non Mag Essentially all fine tan shale, traces of
searlesite, fine pyrite, etc.
Run 1 Mag Essentially all fine tan shale, traces of
searlesite, fine pyrite, etc.
Run 2 Mag Essentially all fine tan shale, traces of
searlesite, fine pyrite, etc.
65
Run 5 Mag Roughly 1:1 mixture of mostly fine shartite and fine
tan shale and dark brown compact shale in roughly
equal amounts. Possible increase of fine pyrite
compared to other samples. Trace searlesite.
35
US 6,173,840 B1
36
These test results show that the reduction of impurities
was obtained by use of wet high intensity magnetic separation.
This eliminates or reduces the need to remove
insoluble impurities by conventional means such as filtration
from a saturated sodium carbonate solution. It also allows
the removal of these impurities found in trona without the
need to remove sodium carbonate monohydrate first to
prevent loss of crystals in a filter cake or rejection stream.
The foregoing description of the present invention has
been presented for purposes of illustration and description.
Furthermore, the description is not intended to limit the
invention to the form disclosed herein. Consequently, variations
and modifications commensurate with the above
teachings, and the skill or knowledge of the relevant art, are
within the scope of the present invention. The embodiment
described hereinabove is further intended to explain the best
mode known for practicing the invention and to enable
others skilled in the art to utilize the invention in such, or
other, embodiments and with various modifications required
by the particular applications or uses of the present invention.
It is intended that the appended claims be construed to
include alternative embodiments to the extent permitted by
the prior art.
What is claimed is:
1. A process for recovering a saline mineral from an ore
containing said saline mineral and impurities which comprises
shortite, pyrite or mixtures thereof, comprising calcining
said saline mineral in an inert atmosphere and separating
a first portion of impurities from said ore by magnetic
separation, wherein said step of calcination produces carbon
dioxide as a waste product and further comprising the step
of recycling carbon dioxide produced by said step of calcination
to provide said inert atmosphere.
2. A process, as claimed in claim 1, wherein said inert
atmosphere further comprises a composition selected from
the group consisting of nitrogen and water vapor.
3. A process, as claimed in claim 1, wherein said saline
5 mineral is calcined at a temperature between about 43° C.
and about 400° C.
4. A process, as claimed in claim 3, further comprising the
step of subjecting said saline material to a preliminary
10 magnetic field prior to said step of separating.
5. A process for the purification of a saline mineral in an
ore comprising saline mineral and impurities, which comprises
shortite, pyrite or mixtures thereof, by magnetic
separation in a first magnetic field having positions of higher
15 intensity and lower intensity, said process comprising prealigning
said ore on a surface with respect to one or more of
said positions of higher intensity of said first magnetic field
prior to separation of said impurities; and separating a first
portion of impurities from said ore by magnetic separation
20 in said first magnetic field.
6. A process, as claimed in claim 5, wherein said surface
comprises a belt and said ore is pre-aligned in the direction
of travel of said belt.
7. A process, as claimed in claim 6, wherein said step of
25 pre-aligning comprises subjecting said ore on said belt to a
second magnetic field.
8. A process, as claimed in claim 6, wherein said step of
pre-aligning comprises feeding said ore onto a portion of
30 said belt which is aligned with said one or more higher
intensity positions of said first magnetic field.
* * * * *