5,736,113
Apr. 7, 1998
United States Patent [19]
Hazen et al.
[54] METHOD FOR BENEFICIATION OF TRONA
[75] Inventors: Wayne C. Hazen, Denver; Roland
Schmidt, Lakewood; Dale Lee
Denham, Jr., Louisville, all of Colo.
[73] Assignee: Environmental Projects, Inc., Casper,
Wyo.
IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII~IIIIIIIIIIIIIIII111111111111
US005736113A
[11] Patent Number:
[45] Date of Patent:
4,375,454 3/1983 Imperto et al 423/206.2
4,512,879 4/1985 Attia et al 209/3
4,943,368 7/1990 Gilbert et al. .. 209/2
5,470,554 1111995 Schmidt et al 423/206.2
OTHER PUBUCATIONS
Perry, Chilton and Kirkpatrick, "Electrostatic Separation",
Chemical Engineers Handbook, 4th Ed. (1963), pp. 21-67 to
21..,.70, no month.
2(i Claims, No Drawings
Primary Examiner-Steven Bos
Attorney, Agent, or Firm-Sheridan Ross P.e.
Disclosed is a method for beneficiating trona from a feedstream
containing trona and impurities by a dry separation
method, namely, electrostatically separating a first portion of
impurities from the trona at a temperature between about 25 °
e. and about 45° C. The disclosed beneficiation of trona
method may also include separation ofimpurities from trona
by other dry separation methods, such as density separation,
magnetic separation and size separation, and/or by wet
separation methods.
[21] Appl. No.: 583,879
[22] Filed: Jan. 11, 19%
[51] Int. CI.6 COlD 11/00; C22B 26/10;
B03C 7/00
[52] U.S. CI 423/206.2; 209/127.2
[58] Field of Search 4231206.2; 209/9,
209/127.2
[56] References Cited
U.S. PATENT DOCUMENfS
3,655,331 4/1972 Seglin et aI 423/206.2
3,802,556 4/1974 Fricke et aI 209/9
3,835,996 9/1974 SingewaId et aI 209/9
4,341,744 7/1982 Brison et aI 4231206.2
[57] ABSTRACT
5,736,113
1
METHOD FOR BENEFICIATION OF TRONA
FIELD OF THE INVENTION
The present invention relates generally to the beneficia- 5
tion of sodium carbonate and, more particularly, trona.
BACKGROUND OF THE INVENTION
Many saline minerals are recognized as being commercially
valuable. For example, trona, borates, potash and 10
sodium chloride are mined commercially. After mining,
these minerals typically need to be beneficiated to remove
naturally occurring impurities.
With regard to trona (Na2C03.NaHC03.2HzO), trona is
commonly used to make soda ash, which is used in the 15
production of glass and paper. Naturally-occurring trona, or
crude trona, is found in large deposits in the western United
States, such as in Wyoming and California, and also in
Egypt, Kenya, Botswana, Tibet, Venezuela and Turkey.
Crude trona ore from Wyoming is typically between about 20
80% and about 90% trona, with the remaining components
including shortite, halite, quartz, dolomite, mudstone, oil
shale, kerogen, mica, nahcolite and clay minerals.
The glass and paper making industries generally require 25
soda ash produced from trona having a purity of 99% 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, crystal-
30 lizing the trona, and drying the trona which 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 mono- 35
hydrate.
Not all industries which use trona require such a highly
purified form of trona. For example, certain grades of glass
can be produced using trona having less than 97% purity.
For this pmpose, U.S. Pat No. 4,341,744 discloses a dry 40
beneficiation process which is less complex and less 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 45
magnetically separating other impurities. Such a process can
yield trona having up to about 95% to 97% purity, depending
on the quantity and type of impurities present in the crude
trona ore.
There are uses for trona, for example, in certain applica- 50
tions in the glass industry, requiring a purity of at least 97%,
yet not needing a purity over 99%. The known dry beneficiation
processes typically do not consistently produce such
a purity. Consequently, these industries generally use soda
ash purified by the more expensive and complex wet ben- 55
eficiation processes.
Commonly-assigned U.S. Patent application Ser. No.
08/066,871, filed May 25, 1993, now U.S. Pat No. 5,470,
554, which is incorporated herein by reference in its entirety,
discloses a dry process for beneficiating saline minerals and 60
which achieves purities on the order of about 97% or more.
The disclosed process significantly enhances the saline
mineral recovery process by producing a low cost, high
purity product However, dry processes may have difficulty
in producing higher purities due to the problem of process- 65
ing fines and/or removing interstitial impurities by a dry
process.
2
Accordingly, it is an object of the present invention to
provide a process for the beneficiation of saline minerals and
in particular, trona, resulting in higher purities than existing
dry beneficiation processes and which is simpler and less
expensive than known wet beneficiation processes. It is
another object of the present invention to provide an
enhanced wet beneficiation process which has advantages
over known wet processes.
SUMMARY OF THE INVENTION
The present invention is embodied in a process for
recovering a high-purity saline mineral from an ore containing
the saline mineral, such as trona, and impurities. The
process generally includes separating a first portion of
impurities from the trona by an electrostatic separation
method at a temperature between about 25° C. and about 45°
C. More preferably, the electrostatic separation is conducted
at a temperature between about 30° C. and about 40° C., and
even more preferably is conducted at a temperature of about
35° C.
In one aspect, the weight recovery of trona electrostatically
separated from a feedstream containing trona and
impurities according to the present invention is at least about
75%. In another aspect, the amount of iron impurities
removed from a feedstream containing trona and impurities
by conducting electrostatic separation according to the
present invention is at least about 80%. In yet another aspect,
the efficiency of iron impurities removal and trona recovery
from a feedstream containing trona and impurities according
to the present invention is at least about 65%.
In one aspect, the process includes separating a second
portion of impurities from the trona by a density separation
method which may occur before or after electrostatic separation
of the first portion of impurities from the trona at a
temperature between about 25° C. and about 45° C. The
density separation step can include air tabling or dry jigging
to separate impurities having a different density than the
trona. The second portion of impurities removed by the
density separation step may comprise shortite. In a preferred
embodiment, the density separation step occurs after electrostatic
separation.
In another aspect of the present invention, the process
includes separating a second portion of impurities by a
magnetic separation step. The magnetic separation step may
occur before or after the step of electrostatic separation at a
temperature between about 25° C. and about 45° C. In a
preferred embodiment, the magnetic separation step occurs
before electrostatic separation.
In yet another aspect· of the invention, a process is
provided for the beneficiation of trona from a feedstream of
trona having impurities. The process generally includes the
steps of sizing the feedstream of trona into a first size
fraction and a second size fraction, separating the first size
fraction into a first recovered portion and a first impurity
p~rtion by electrostatic separation at a temperature of
between about 25° C. and about 45° C., and separating the
second size fraction into a second recovered portion and a
second impurity portion by a wet separation method. In a
preferred embodiment, the electrostatic separation of the
first size fraction is conducted at a temperature between
about 30° C. and about 40° C., and more preferably at a
temperature of about 35° C. The process may furtherinclude
calcining the trona to form sodium carbonate, the calcining
step occurring after the electrostatic separation step.
In a preferred embodiment, the process includes separating
a first portion of impurities by a magnetic separation
5,736,113
3 4
as disclosed in U.S. Pat. No. 4,341,744, which is incorporated
herein by reference in its entirety. As discussed in the
above-identified patent, saline mineral ore particles are first
differentially electrified and then separated into a recovered
stream from an impurity stream by various electrostatic
separation processes, including, conduction or conduction in
conjunction with ion bombardment.
In one embodiment of the invention and as noted above,
beneficiation of trona from a feedstream of trona having
10 impurities is conducted by electrostatically separating a first
portion of impurities from the trona at a temperature of
between about 25° C. and about 45° C., more preferably at
a temperature between about 30° C. and about 40° c., and
most preferably, at about 35° C. To conduct electrostatic
15 separation within the above temperature ranges, the feedstream
of trona having impurities can be heated to the
identified temperatures prior to and/or during separation. For
example, the feedstream of trona may be heated to the
desired temperature in a standard drying oven prior to
20 differential electrification. Further, where the feedstream of
trona is transferred from a feed bin to an electrostatic
separator using a roll, both the feed bin and the roll may be
heated during electrostatic separation. In addition, the ambient
temperature during the separation can be maintained at
25 a high enough temperature to meet the above-noted temperature
requirements.
By practice of the present invention, it has been found that
electrostatic separation at a temperature between about 25°
C. and about 45° C. can remove at least about 30 wt %,
30 more preferably about 50 wt. %, and most preferably about
80 wt. % of the insoluble iron impurities from the feedstream
of trona having impurities.
It has also been found that the trona weight recovery
35 (weight of trona recovered/weight of trona in the
feedstream) from the electrostatic separation at a temperature
between about 25° C. and about 45° C. is between about
60% and about 95%, and more preferably, between about
70% and about 90%, and most preferably about 80%.
Further, it has been found that electrostatic separation at
a temperature between about 25° C. and about 45° C.
increases the efficiency of iron removal and trona recovery.
The efficiency (in percent) may be quantitatively measured
as follows: ((weight percent of iron assay of feedstream-
45 weight percent of iron assay of recovered product)/weight
percent of iron assay of feedstream)xpercent of trona
recoveredxlOO. In a preferred embodiment of the present
invention, conducting electrostatic separation at a temperature
of about 35° C. resulted in a reduction of the iron
50 (Fe20 3) assay by about 83% and the trona recovery was
80%, which equals an efficiency of about 65%.
The impurity stream from a first pass of an electrostatic
separation process can go through a scavenger step to
improve the overall recovery. The scavenger step recovers a
55 trona-containing portion ofthe impurity stream from the first
pass through electrostatic separation and combines it with
the recovered stream to increase the overall yield of the
electrostatic separation step or otherwise cycles it to other
steps in the process. Furthermore, the recovered streamfrom
60 the first pass of the electrostatic separation can go through
one or more electrostatic cleaning steps to further remove
impurities from the recovered stream and improve the purity
of the final product.
In an alternative embodiment, a second portion of impu65
rities may be separated from the feedstream of trona by a
density separation step. Density separation methods are
based on subjecting an ore to conditions such that materials
DEfAll.,ED DESCRIPTION
Processes of the present invention are designed to recover
saline minerals from naturally occurring ores to produce
commercially valuable purified minerals. As used 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, sodium chloride, and preferably, trona.
The purity of saline minerals within an ore depends on the
deposit location, as well as the area mined at a particular
deposit. In addition, the mining technique used can significantly
affect the purity of the minerals. For example, by
selectively mining, higher purities of saline minerals can be
achieved. Deposits of trona ore are located at severallocations
throughout the world, including Wyoming (Green
River Formation), California (Searles Lake), Egypt, Kenya,
Venezuela, Botswana, Tibet and Turkey (Beypazari Basin).
For example, a sample of trona ore from Searles Lake has
been found to have between about 50% and about 90% by
weight (wt.8) trona and a sample taken from the Green River
Formation in Wyoming has been found to have between
about 80 and about 90 wt. % trona. The remaining 10 to 20
wt. % of the ore in the Green River Formation sample
comprised impurities including shortite (1 to 5 wt. %) and
halite, and the bulk of the remainder comprises 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.
The present process is directed to processes for the 40
beneficiation of saline minerals and, in particular, the beneficiation
of trona. For purposes of discussion, preferred
embodiments of the present invention will be discussed with
reference to trona. However, it should be appreciated that the
intended scope of the present invention includes processes
for the beneficiation of saline minerals more generally.
The present process includes removing a first portion of
impurities from a feedstream of trona having impurities by
an electrostatic separation method.. Electrostatic separation
methods are based on subjecting the ore to conditions such
that materials of different electrical conductivities separate
from each other. For example, electrostatic separation can be
used to separate trona from impurities having a higher
electrical conductivity, such as shale, mudstone, or pyrite. n
should be appreciated, however, that electrostatic separation
could also be used to separate impurities that have a lower
electrical conductivity than the saline mineral being recovered.
One embodiment of the present invention for beneficiation
of trona having impurities includes the step of electrostatically
separating a first portion of impurities from the
trona which is at a temperature of between about 25° C. and
about 45° C. nhas been surprisingly found that by conducting
electrostatic separations in this temperature range significant
increases in efficiencies can be obtained.Any known
electrostatic separation technique can be used for this step of
the present invention, including differential electrification,
step, subjecting the nonmagnetic portion recovered from the
magnetic separation step to electrostatic separation at a
temperature between about 25° C. and about 45° C., which
separates the "dirty" trona from the "clean" trona.
Thereafter, the "clean" trona may be calcined to produce 5
sodium carbonate. The sodium carbonate may then be
subjected to a density separation step.
5,736,113
5
of different densities physically separate from each other.
Thereby, certain impurities having a different density than
the desired trona 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, solidlbrine separation, and drying of the
product is eliminated. Any known density separation technique
could be used for this step of the present invention,
including air tabling or dry jigging.
In one embodiment of the invention, the density or gravity
separation step may occur after the electrostatic separation
step. As discussed in U.S. patent application Ser. No.
08/066,871, filed May 25, 1993, now U.S. Pat. No. 5,470,
554, density separation is conducted by subjecting an ore to
conditions such that materials of different density separate
from each other. The mineral stream having materials of
varying densities is then separated by a first or 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, trona is recovered in the lighter stream.
With regard to the beneficiation of trona, which has a
density of 2.14, impurities that are removed during the
density separation step of the present invention include
shortite having a density of2.6, 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 differences 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. %,
more preferably about 50 wt. %, and most preferably about
90 wt. % of the heavy impurity.
The present process may further include a magnetic
separation step which subjects the ore to conditions such that
materials of different magnetic susceptibility separate from
each other into a recovered stream and an impurities stream.
The magnetic separation step can be accomplished by any
conventional technique, such as induced roll, cross-belt, or
high intensity rare earth magnetic separation methods.
Preferably, induced roll is used in the present invention for
the finer fractions and high intensity rare earth magnets are
used for the coarser fractions. With regard to the beneficiation
of trona, typical impurities can be removed during the
magnetic separation step include shale which has a higher
magnetic susceptibility than trona. By practice ofthe present
invention, the use of an induced roll magnetic separation
technique can remove at least about 5 wt. %, more preferably
about 50 wt. %, and most preferably about 90 wt. % of
the shale from the material being treated by magnetic
separation.
In a further embodiment of the present invention, the
trona-containing ore or trona 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
optional because the coarse particles of ore partially act as
the crushing medium, thus requiring less cost in obtaining
grinding media. Moreover, because trona is 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.
6
In general, crushing to smaller particle size achieves
better liberation of impurities and thus, improve recovery.
However, if the particle size after crushing is too fine, there
may be adverse effects upon subsequent separation steps. In
5 addition, over-crushing is not needed for many applications
of the present invention and merely increases the cost
associated with the crushing step. It has been found that
acceptable liberation of the present process can be achieved
by crushing the trona to less than about 6 mesh. Preferably,
10 a minimumparticle size of the trona prior to the electrostatic
separation at a temperature between about 25° C. and about
45° C. is about 100 mesh.
In another embodiment of the present invention, trona is
sized into size fractions prior to the separation steps. Each
15 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.
On the other hand, a large number of fractions will increase
the efficiency, but may increase the cost of the overall
20 process. The use of between 3 and 10 fractions has been
found to be acceptable. Preferably, the number of fractions
is between 4 and 10, and more preferably, the number of
fractions is 10. Any conventional sizing technique can be
used for the present process, including screening or air
25 classification. For dividing into 10 fractions, the fractions
typically have the following particle size ranges: 6x8, 8xlO,
10x14, 14x20, 20x28, 28x35, 35x48, 48x65, 65xl00 and
-100. The +100 mesh fractions may be processed by any dry
process described herein and the -100 mesh may be pro-
30 cessed by any wet method described herein, or sold without
processing as they are enriched in the sizing process.
In yet another embodiment of the present invention, the
trona is dried prior to the separation steps set forth above.
The drying step removes surface moisture from the trona to
35 better enable the trona 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 to less
than about 1% surface moisture content. During the drying
40 process, it is preferred that the trona 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° C. to avoid calcination.
In still another embodiment of the present invention, a
45 de-dusting step is added to the basic beneficiation process to
remove fines before the electrostatic separation step.
De-dusting can be particularly important before electrostatic
separation because the dust can otherwise interfere with the
effective electrostatic separation. Such a de-dusting step can
50 be conducted before, during or after one or more of the
crushing, sizing and/or 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 de-dusting can have a
55 purity of greater than about 94%, preferably greater than
about 96% and preferably greater than about 98%. Pines 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.
60 In various embodiments of the present invention, combination
dry and wet processes for the production of trona are
provided. The dry processes can include any known or
hereafter developed processes for the dry beneficiation of
ores containing trona. Such processes can include density
65 separation, magnetic separation, and/or electrostatic separation
at a temperature between about 25° C. and about 45° C.
The wet processes can include any process which includes
5,736,113
EXAMPLES 1-13
(iron assay of feed -
iron assay of;:at) X trona recovery x 100.
lronassay 0
The results show that at 35° c., the iron assay was reduced
by about 83% and the trona recovery was 80%, giving an
efficiency of about 65%. In this regard, as shown in by the
data in Table 1, in its place, the efficiency at 35° C. was much
higher than for any other temperature. The next best temperature
was 45° C. with an efficiency of about 40%.
8
wet separation method, wherein at least about 15 wt. % of
said feedstream is processed by said wet separation method.
The dry separation method is selected from the group
consisting of density separation, magnetic separation, electrostatic
separation processes as described herein, and combinations
thereof. In addition, the wet separation method
includes a dissolution and crystallization process.
Preferably, the weight percent process by said wet separation
process is at least about 20%, and more preferably at least
about 30%. In the instance of trona, this embodiment can
further include the step of calcining the trona to form sodium
carbonate.
7
dissolution and crystallization, such as those disclosed in
commonly assigned U.S. patent application Ser. No. 08/373,
955, filed Jan. 17, 1995, pending, and U.S. patent application
Ser. No. 08/544,135, filed Oct. 17, 1995, pending, both of
which are incorporated by reference in their entirety herein. 5
A wet separation method of the various embodiments of
the present invention includes a dissolution and crystallization
process. Such a process takes advantage of the fact that
the solubilization and crystallization of saline minerals
results in more pure crystals because impurities are excluded 10
as crystals are formed after solubilization. In accordance
with the wet separation processes of the present invention,
the product recovered thereby is highly pure and can contain
greater than about 97% weight (weight percentage) soluble
material, more preferably greater than about 98 wt. % 15 Thirteen splits of trona-containing ore were beneficiated
soluble material and most preferably greater than about 99 in accordance with the present invention by electrostatic
wt % soluble material. Further, such product has less than separation of impurities (e.g., Fe
2
0 3
) from trona at various
about 0.05 wt. % iron. More preferably, the iron content is temperatures between 15° C. and 75° C. More specifically,
at most about 0.02 wt. % and even more preferably at most electrostatic separation of impurities from trona was conabout
0.01 wt. %. 20 ducted at 15° C., 25° C., 35° C., 45° c., 55° C., 65° C., and
In one embodiment of the dissolution and crystallization 75° C. With regard to the samples tested, the shale and some
process, saline mineral crystals are dissolved in water or an of the trona high in impurities were removed from approxiunsaturated
saline solution. For example, in the case of mately 200 lbs of 28x35 mesh trona ore by a single pass on
trona, trona (the sesquicarbonate form of sodium carbonate) an Briez rare earth magnet. This separation was run under
or anhydrous sodium carbonate (calcined trona) can be conditions that minimized trona losses into the magnetic
dissolved. Once in solution, water is driven off, and the 25 product. The non-magnetic product was blended in a "V"
saline mineral crystallizes. For example, the water can be blender and split with a riffle splitter into charges to be used
driven off by heating the solution. However, such a process in the electrostatic separation tests.
can be expensive and time-consuming due to the energy
required to heat the water and the amount of time required The electrostatic separations were made utilizing a Carto
fully dry the crystals. 30 pco electrostatic separator having a lO-inch roll. To minimize
the variables in the tests, the revolutions per minute
In another method to perform dissolution crystallization were held constant at 100 rpm and the position of the top
in the instance of trona, trona is first calcined to produce electrode was unchanged (full pinning). The effective voltanhydrous
sodium carbonate crystals which are added to a age was evaluated visually and no benefit was observed in
saturated sodium carbonate brine solution. As anhydrous using less than the maximum attainable without arcing. Two
crystals go into solution and recrystallize, they crystalize in 35 different bottom electrodes were evaluated in the tests of
the monohydrate form if the temperature is between about splits 1-13, the first being a combination electrode consist-
35° C. and about 112° C. Accordingly, there is a continuous ing of a I-inch aluminum rod with a nichrome wire suscrystallization
process which tends to significantly reduce pended on one side, the other electrode being a very fiatthe
impurities in the crystals. Crystals can then be recovered tened hollow oval which provided a broad surface for lifting.
from the brine solution. A specific example of this process 40
is disclosed in U.S. Pat. No. 2,887,360 issued May 19, 1959 The trona splits were heated to the above-noted tempera-
(Hoelge). tures in a standard drying oven and, to minimize the cooling
of these splits during separation, the feed bin and the
In yet another embodiment of the combination wet and electrostatic separator roll were heated to slightly higher
dry process of the present invention, a process for the than the desired temperature with a heat gun. Surface
production of trona from a feedstream having impurities is 45 temperatures were measured with an infrared thermometer,
provided. The process includes the steps of separating a first and split temperatures were measured with a thermal couple.
portion of a feedstream of trona into a first recovered portion The calibration of the infrared thermometer and the therand
a first impurity portion by a dry separation method, and mocouple were checked using boiling water.
separating a second portion of the feedstream of trona into
a second recovered portion and second impurity portion by 50 The data generated from the foregoing beneficiation proa
wet separation method. The second portion may comprise cess is shown in Tables 1-2. As can be seen from the Tables,
particles having a particle size larger than about 100 mesh the recovery of trona range from 80% in Example No.3 to
and more preferably, larger than about 65 mesh. The dry 87.7% in Example No.4. In addition, the efficiency of the
separation method is selected from the group consisting of electrostatic separation process can be calculated based upon
density separation, magnetic separation, electrostatic sepa- the following equation:
ration processes as described herein, and combinations 55
thereof. In addition, the wet separation method can be a
dissolution and crystallization process. In the instance of
trona, this embodiment can further include the step of
calcining the trona to form sodium carbonate.
In another embodiment of the combination of the wet and 60
dry process of the present invention, the process for the
production of saline mineral from a feedstream having
impurities is provided. This embodiment includes the steps
of separating a first portion of impurities by a dry separation
method, and separating a second portion of impurities by a
5,736,113
9 10
TABLE 1
Summary of Test Conditions and Data from Electrostatic Separations on 28 X 35 Mesh
'Iluna at Different Temperatures
Thst Conditions:
Roll: 10" Diameter, 100 RPM
Top Electrode: Unchanged for all tests, combination electrode, full pinning position, 61 degrees, Wrre 2" from roll
Bottom Electrode: Type variable (see below), 27 degrees, center of support 3.25" from roll
CondlMid Splitter: Variable (see below)
MidINon Com Splitter: Variable (see below)
Temperature Degrees C.
Thst --fu2.. Roll Splitters·· Bottom Electrode··· Best Product (Based on Fe Assay)·•••••
95-5-4- In Out Start End CondlMid MidINC Type Position TYpe % Insol.· % Fez0 3 % Rec
15 15 20 18 35 75+ Combo···· Full Non 4.29 0.082 1.6
Pinning Cond.@
2A 25 25 20 22 35 75+ Combo···· Full Non No Separation
Pinning Cond@ Products Not Saved
2 25 25 23 22 30 75 Lifting····· 45 Non 2.28 0.027 33.6
Degrees Cond.
3A 35 35 35 35 40 55 Lifting····· 45 Non No Separation
Degrees Cond. Products Not Saved
3 35 35 35 36 25 75 Combo**** Full Non 3.44 0.016 80.0
Pinning Cond.
4 45 44 47 45 25 55 Combo···· Full Non 4.18 0.063 87.7
Pinning Cond.
5 45 45 49 46 25 55 Lifting····· 45 Non 3.73 0.045 63.2
Degrees Cond
6 45 45 48 45 25 55 Combo···· ~and Non 4.80 0.Q35 70.9
~ Cood
7 55 54 59 55 25 40 Combo···· ~and Non 5.24 0.070 83.6
Y. Cood
8 65 63 fB 63 25 40 Combo···· ~and Non 12.55 0.064 1.3
~ Cood@
9 65 63 fB 62 35 75+ Combo···· ~and Non 4.10 0.045 52.5
~ Cond
10 75 72 80 65 45 75+ Combo···· y.and Non 11.63 0.052 6.5
~ Cond
11 75 72 80 65 30 75+ Combo···· Full Non 4.07 0.059 659
Pinning Cond
Feed, Average 44.73 0.085
from all tests
•Assays are based on uncalcinated trona.
••1he position of the splitters is indicated by markings on the handle, 0 is all the way left and flat, 50 is vertical, a "+" after the setting
indicates that a 1" extender was added to the splitter blade.
••*The top electrode was unchanged
····Combo indicates combination electrode which is a 1" diameter bar with a nichrome wire mounted 1" from the rod.
·····Lifting electrode is the one piece, sort of oval shaped electrode.
······Excluding Midd, for samples marked @ the Mid was the lowest iron product.
TABLE 2
Summary of Data from Temperature an Electrostatic Separation of Trona
Feed: 28 x 35 Mesh S0810 Screened in Pilot Plant, Rescreened with Sweco Screen
Test #1
Weight Dist., %
of:
Feed to 28 x 35
Water Insoluble
Dist., % of:
Water Soluble
Dist.. % of:
Fe,03
Dist., % of
Product Step Mesh Assay, %. ES Feed Sample Assay, %. ES Feed Sample Assay, %. ES Feed Sample
Eziez Rare Earth Belt Separation on 20 x 28 Mesh SW8lO
Magnetic 5.2 5.2
Non Mag. 94.8 94.8
Feed Calc. 100.0 100.0
Test # 95-5-4-1
Comuctor 12.5 119 5.44 16.3 94.56 12.3 0.135 20.5
Mi&iling 859 81.5 3.99 82.1 96.01 86.1 0.075 77.9
NonCond 1.6 1.5 4.29 1.6 95.71 1.6 0.082 1.6
NC+Midd 87.5 83.0 4.00 83.7 96.00 87.7 0.075 79.5
Feed Calc. 100.0 94.8 4.18 100.00 95.82 100.0 0.082 100.0
Test # 95-4-2A
5,736,113
11 12
TABLE 2-continued
Summary of Data from Temperature an Electrostatic Separation of Trona
Feed: 28 X 35 Mesh S9810 Screened in Pilot Plant, Rescreened with Sweco Screen
Weight Dis!., %
of: Water Insoluble Water Soluble Fea03
Test #1 Feed to 28 X 35 Dis!.. % of: Dis!., % of: Dis!., % of
Product Step Mesh Assay, %* ES Feed Sample Assay, %* ES Feed Sample Assay, %* ES Feed Sample
Conductor 0.0 0.0 Everything going to non conductor, products not saved
Middling 0.8 0.8
NonCond. 99.2 94.0
Feed Calc. 100.00 94.8
Test # 95-5-4-2
Conductor 3.8 3.6 14.03 11.9 8597 3.5 0.550 24.4
Middling 63.3 60.0 5.10 71.5 94.90 629 0.090 65.5
NonCond 32.9 31.2 2.28 16.6 97.72 33.6 0.027 10.2
NC +Midd 96.2 91.2 4.14 88.1 95.86 96.5 0.068 75.6
ca
Feed Calc. 100.0 94.8 4.52 100.0 95.48 100.0 0.087 100.0
Test # 95-5-4-3A
Conductor 4.9 4.7 Everything going to middling and conductor, products not saved
Middling 81.2 77.0
Non Cond 13.9 13.2
Feed Calc. 100.0 94.8
Test # 95-5-4-3
Conductor 4.1 39 14.27 12.7 85.73 3.7 0.491 34.2
Middling 16.9 16.0 7.84 28.6 92.16 16.3 0.162 46.1
NonCond. 79.0 74.9 3.44 58.7 96.56 80.0 0.D15 19.7
Feed Calc. 100.0 94.8 4.63 100.0 95.37 100.0 0.059 100.0
Test # 95-5-4-4
Conductor 1.0 09 15.01 3.1 84.99 09 0.660 7.4
Middling 11.9 11.3 8.43 20.9 91.57 11.4 0.223 30.3
NonCond 87.1 82.6 4.18 76.0 95.82 87.7 0.063 62.3
Feed Calc. 100.0 94.8 4.79 100.0 95.21 100.0 0.088 100.0
Test # 95-5-4-5
Conductor 9.8 9.3 9.78 20.8 90.22 9.3 0.300 34.0
Middling 27.6 26.2 4.85 28.9 95.15 27.5 0.106 33.5
NonCond 62.6 59.4 3.73 50.4 96.27 63.2 0.045 32.5
Feed Calc. 100.0 94.8 4.63 100.0 95.37 100.0 0.087 100.0
lest # 95-5-4-6
Conductor 5.3 5.0 12.18 11.5 87.82 4.9 0.431 27.9
Middling 24.4 23.2 6.65 28.8 93.35 24.2 0.141 41.9
NonCond 70.3 66.6 4.80 59.7 95.2 70.9 0.035 30.2
Feed Calc. 100.0 94.8 5.62 100.0 94.38 100.0 0.082 100.0
lest # 95-5-4-7
Conductor 2.2 2.1 12.42 4.8 87.58 2.0 0.540 12.6
Middling 14.5 13.8 6.80 17.6 93.20 14.3 0.165 25.4
NonCond 83.3 79.0 5.24 77.6 94.76 83.6 0.070 62.1
Feed Calc. 100.0 94.8 5.62 100.0 94.38 100.0 0.094 100.0
Test # 95-5-4-8
Conductor 76.6 72.6 4.75 76.9 95.25 76.6 0.110 89.8
Middling 22.0 20.8 4.13 19.2 95.87 22.1 0.039 9.2
NonCond 1.5 1.4 12.55 39 87.45 1.3 0.064 1.0
Feed Calc. 100.0 94.8 4.73 100.0 95.27 100.0 0.094 100.0
Test # 95-5-4-9
Conductor 5.7 5.4 8.80 11.2 91.20 5.5 0.304 20.5
Middling 42.0 39.8 4.42 41.2 95.58 42.0 0.104 51.7
NonCond 52.3 49.6 4.10 47.6 95.90 52.5 0.045 27.8
Feed Calc. 100.0 94.8 4.5 100.0 95.5 100.0 0.085 100.0
Test # 95-5-4-10
Conductor 7.8 7.4 6.16 11.1 93.84 7.7 0.224 21.2
Middling 85.1 80.7 3.55 69.8 96.45 85.8 0.072 74.3
NonCond 7.1 6.7 11.63 19.1 88.37 6.5 0.052 4.4
Feed Calc. 100.0 94.8 4.33 100.0 95.67 100.0 0.083 100.0
Test # 95-5-4-11
5,736,113
13
TABLE 2-continued
Summary of Data from Temperature an Electrostatic Separation of 1hma
Feed: 28 X 35 Mesh S0810 Screened in Pilot Plant, Rescreened with Sweco Screen
14
Test #1
Weight Dis!., %
of:
Feed to 28 X 35
Water Insoluble
Dis!., % of:
Water Soluble
Dist.• % of: Dist., % of
Product
Conductor
Middling
NonCond.
Feed Calc.
Average
Feed
Step Mesh Assay, %* ES Feed Sample Assay, %* ES Feed Sample Assay, %* ES Feed Sample
5.5 5.2 9.09 11.3 90.91 5.2 0.409 24.9
28.9 1:1.4 4.43 28.8 95.57 28.9 0.103 32.8
65.6 62.2 4.07 60.0 9593 659 0.059 42.4
100.0 94.8 4.45 100.0 95.55 100.0 0.091 100.0
4.73 95.27 0.085
*Note: Assays are based on uncalcined trona; they would be about 30% higher for calcined trona.
The foregoing description of the present invention has 20
been presented for purposes of illustrating the 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 25
described herein above is further intended to explain the best
mode known for practice in the invention and to enable those
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 30
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 beneficiation of trona from a feedstream 35
of trona having impurities comprising electrostatically separating
a first portion of impurities from said trona, wherein
said trona is maintained at a temperature of between about
25° C. and about 45° C. throughout said step of electrostatically
separating. 40
2, A process, as claimed in claim 1, wherein said step of
electrostatically separating is conducted at a temperature
between about 30° C. and about 40° C.
3. A process, as claimed in claim 1, wherein said step of
electrostatically separating is conducted at a temperature of 45
about 35° C.
4. A process, as claimed in claim 1, further comprising
separating a second portion of impurities from said trona by
density separation.
5. A process, as claimed in claim 4, wherein said density 50
separation step occurs after said electrostatically separating
step.
6. A process, as claimed in claim 1, further comprising
magnetically separating a second portion of impurities from
said trona. 55
7. A process, as claimed in claim 6, wherein said magnetically
separating step occurs before said electrostatically
separating step.
8, A process, as claimed in claim 1, further comprising,
before said electrostatically separating step, reducing a par- 60
ticle size of said trona to less than about 6 mesh.
9. A process, as claimed in claim 1, wherein said feedstream
has a minimum particle size before said electrostatically
separating step of about 100 mesh.
10. A process, as claimed in claim 1, further comprising, 65
before said electrostatically separating step, sizing said trona
into size fractions.
11. A process, as claimed in claim 1, further comprising,
before said electrostatically separating step, drying said
trona to remove surface moisture therefrom.
12. A process, as claimed in claim 1, further comprising,
before said electrostatically separating step, de-dusting said
trona to recover fines.
13. A process, as claimed in claim 1, further comprising
calcining said trona to produce sodium carbonate.
14. A process, as claimed in claim 13, wherein said
calcining step occurs after said electrostatically separating
step.
15, A process, as claimed in claim 1, further comprising
scavenging a recovered portion from said first portion of
impurities; and
recycling said recovered portion to said step electrostatically
separating.
16. A process, as claimed in claim 1, further comprising
calcining a portion of trona to form sodium carbonate; and
separating a second portion of impurities from sodium
carbonate by a wet separation method.
17. A process, as claimed in claim 1, wherein the weight
recovery of said trona from said electrostatically separating
step is about 80%.
18. A process, as claimed in claim 1, wherein the weight
removal of iron impurities is at least about 50%.
19. A process, as claimed in claim 1, wherein the efficiency
for removing iron impurities and recovering said
trona is at least about 80%,
20. Aprocess for beneficiation of trona from a feedstream
of trona having'impurities comprising:
(a) sizing said feedstream into a first size fraction and a
second size fraction;
(b) separating said first size fraction into a first recovered
portion and a first impurity portion by electrostatic
separation, wherein said first size fraction is maintained
at a temperature of between about 25° C. and about 45°
C. throughout said step of electrostatic separation; and
(c) separating said second size fraction into a second
recovered portion and second impurity portion by a wet
separation method.
21. A process, as claimed in claim 20, wherein said
separating said first size fraction is at a temperature between
about 30° C. and 40° C.
22. A process, as claimed in claim 20, wherein said
separating said first size fraction is at a temperature of about
35° C.
23. A process, as claimed in claim 20, further comprising
the step of calcining said trona to form sodium carbonate.
5,736,113
15
24. A process, as claimed in claim 23, wherein said
calcining step occurs after said separating by electrostatic
separation step.
25. A process, as claimed in claim 20, further comprising
separating said first impurity portion into a third recovered 5
portion and a third impurity portion by a wet separation
method including a dissolution and crystallization process,
and wherein at least about 15 weight percent of said feedstream
is processed by said wet separation method.
16
26. A process, as claimed in claim 23, wherein said
calcining step occurs before step (c), and wherein said wet
separation step (c) comprises the steps of:
(i) converting said sodium carbonate to monohydrate
crystals in a sodium carbonate brine solution; and
(ii) separating at least a portion of said monohydrate
crystals from insoluble impurities.
* * * * *