6,092,665 Beneficiation of saline minerals

Patent Number/Link:

6,092,665

Jui. 25, 2000

[11]

[45]

111111111111111111111111111111111111111111111111111111111111111111111111111

US006092665A

Patent Number:

Date of Patent:

United States Patent [19]

Schmidt et ai.

FOREIGN PATENT DOCUMENTS

3816061 8/1989 Germany 423/206.2

Primary Examiner-Tuan N. Nguyen

Attorney, Agent, or Firm---8heridan Ross P.e.

A process is provided for recovering a saline mineral from

an ore containing the saline mineral and impurities. In one

aspect, the process generally includes the steps of separating

a first portion of impurities from the ore by density

separation, electrostatically separating a second portion of

impurities from the ore, and magnetically separating a third

portion of impurities from the ore. The process can further

include the steps of crushing the ore and dividing the

crushed ore into a plurality of size fractions before the

above-referenced separating steps. In another aspect, the

process includes the steps of calcining the ore and subsequently

separating a first portion of impurities by density

separation. Indirect heating may be utilized for the calcining

process and, preferably, calcining gases are recycled and

utilized for heating fluidizing another portion of ore. Water

vapor may be condensed from the calcining gas and utilized

for other purposes.

ABSTRACT

3/1975 Sproul et al. 423/206.2

7/1982 Brison et al. 209/127.1 X

3/1983 Imperto et al. 423/206.2

7/1990 Gilbert et al. 209/40 X

11/1995 Schmidt et al. 209/131 X

7/1997 Schmidt et al. 423/206.2 X

3,869,538

4,341,744

4,375,454

4,943,368

5,470,554

5,651,465

[57]

Related U.S. Application Data

[54] BENEFICIATION OF SALINE MINERALS

[75] Inventors: Roland Schmidt, Lakewood; Dale L.

Denham, Louisville, both of Colo.;

Ralph B. Tacoma, Green River, Wyo.;

Allen H. Moore, Parker; Allan L.

Thrner, Lakewood, both of Colo.

[73] Assignee: Environmental Projects, Inc, Casper,

Wyo.

[21] Appl. No.: 08/737,871

[22] PCT Filed: May 25,1994

[86] PCTNo.: PCT/US94/05918

[56] References Cited

U.S. PATENT DOCUMENTS

[63] Continuation-in-part of application No. 08/066,871, May

25, 1993, Pat. No. 5,470,554.

[51] Int. CI? B03B 1/00

[52] U.S. CI. 209/3; 209/11; 209/39;

209/127.1; 209/214; 423/206.2

[58] Field of Search 209/3, 12.1, 12.2,

209/17, 30-37, 39, 40, 127.1, 128, 131,

214, 11; 423/121, 206.2; 241/19, 24, 25

§ 371 Date: JuI. 3, 1997

§ 102(e) Date: JuI. 3, 1997

[87] PCT Pub. No.: W094/27725

PCT Pub. Date: Dec. 8, 1994

3,244,476 4/1966 Smith 423/206.2 X 38 Claims, 1 Drawing Sheet

HEATER

CALCINED

TRONA ORE

HIGH-EffiCIEHCY

PARTICUlATE

SCRUBBER

HIGH

PURIlY

WATER

PARTICUlATE

WATER

COMBUSTION

GASES

ANAL PRODUCT

FUEL

HIGH

HIGH-EmCIENCY 2ND STAGE LpURITY

~ PARTICULATE CONDENSER I -WATER

SCRUBBER

~ ITO STACK

COMBUSTION

GASES

~ SLUSH PROCESS I II I

(- 200 MESH)

d•

•'JJ.

~..... ~=.....

~Ul

FINAL PRODUCT

DENSITY I I MAGNETIC

SEPARATION r--I SEPARATION I(+

65 MESH)

MAGNETIC

SEPARATION

(65 X200 MESH)

STEAM

BOILER ~FUEL r

FLUIDIZED BED

REACTOR

1ST STAGE I--PARTICULATE

CONDENSER I - WATER

I 'CALCINING

GASES CALCINED

TRONA ORE

- I

RAW....--_

O~ CR~SH I

-6 MESH

FRESH GAS a

HEATER

...0. \ =\C

...N.

6,092,665

BENEFICIATION OF SALINE MINERALS

REFERENCE TO RELATED APPLICATIONS

This application is filed under 35 U.S.c. §371 based on 5

PCT/US94/05918, filed on May 25, 1994, which is a CIP of

U.S. patent application Ser. No. 066,871, filed on May 25,

1993, now U.S. Pat. No. 5,470,554.

FIELD OF THE INVENTION

ciation processes typically do not consistently produce such

a purity. Consequently, these industries generally use trona

purified by the more expensive and complex wet beneficiation

processes.

Accordingly, it is an object of the present invention to

provide a dry 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.

The present invention relates generally to the beneficiation

of saline minerals and, more specifically, trona. The

invention further relates to a dry process for recovering

saline minerals from an ore containing saline minerals and

impurities.

BACKGROUND OF THE INVENTION

Many saline minerals are recognized as being commercially

valuable. For example, trona, borates, potash and

sodium chloride are mined commercially. After mining,

these minerals need to be beneficiated to remove naturally

occurring impurities.

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 and paper. Naturallyoccurring

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 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

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, crystallizing

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 monohydrate.

Not all industries which use trona require such a highly

purified form of trona. For example, certain grades of glass

can be produced utilizing trona 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 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 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. The lower resulting purities of known dry processes

is partially due to the presence of impurities, such as

shortite and halite, which have similar electrostatic and

magnetic properties as the trona. Further, halite has a similar

density as the trona and, therefore, is difficult to remove even

utilizing known wet density separation processes.

There are uses for trona, for example, in certain applications

in the glass industry, requiring a purity of at least 97%,

yet not needing a purity over 99%. The known dry benefi-

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 and impurities. In one aspect of the

15 present invention, the process generally includes separating

a first portion of impurities from the ore by a density

separation method, electrostatically separating a second

portion of impurities from the ore, magnetically separating

a third portion of impurities from the ore.

In one embodiment, the density separation step can

include air tabling or dry jigging to separate impurities

having a different density than the saline mineral. In another

embodiment, the process of the present invention is used for

25 beneficiating trona from an ore containing trona and impurities.

In this embodiment, the first portion of impurities

removed by the density separation step comprises shortite.

In another embodiment of the present invention, a process

is provided for the production of purified soda ash for

30 production of caustic soda by the lime-soda process. The

process generally includes the steps of separating a first

portion of impurities from a trona-containing ore by a

density separation method, electrostatically separating a

second portion of impurities from the ore, magnetically

35 separating a third portion of impurities from the ore. The

product of the above-mentioned separation processes is used

to produce caustic soda. The process further includes solubilizing

aluminum hydroxide in bauxite by contacting the

bauxite with the caustic soda to produce a solution and

40 recovering alumina from the solution.

In another aspect of the present invention, a process is

provided which includes calcining the saline mineral prior to

density separation. The process generally includes calcining

the ore to alter the apparent density of the saline mineral and

45 separating a first portion of impurities from the calcined ore

by density separation to produce a recovered saline mineral.

This process is particularly suitable for separating impurities

which have densities similar to the density of the saline

mineral prior to calcination, but which have different appar-

50 ent densities after calcination. In one embodiment, the saline

mineral comprises trona and the first portion of impurities

comprises halite. The process also improves the separation

of a saline mineral from other impurities by widening the

difference in apparent densities between the saline mineral

55 and such other impurities.

In yet another aspect of the present invention, a process is

provided for effectively removing impurities from about a

-65 mesh size fraction. The process generally comprises the

steps of sizing the ore to generate about a -65 mesh fraction

60 and about a +65 mesh fraction and separating iron from the

-65 mesh fraction to produce a first recovered portion. In

one embodiment, the separating step comprises a wet separation

process, such as the slush process. In another

embodiment, the separating step comprises magnetic sepa-

65 ration. In addition to iron, shaley components, such as

dolomitic and oil shales, may also be removed during the

separating step. Preferably, a second portion of impurities is

6,092,665

3 4

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

5 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.

10 Consequently, the process according to the present invention

is much cheaper and less complex. Any known density

separation technique could be used for this step of the

present invention, including air tabling or dry jigging.

As discussed above, density separation is conducted by

15 subjecting an ore to conditions such that materials of different

densities 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,

20 in the case of beneficiating trona, trona is recovered in the

lighter stream. The purity of a saline mineral recovered from

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

25 higher purity, but the rougher stage process will also have a

reduced yield because more of the desired saline mineral

will report 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

30 be of higher value because it can be used in other applications

where high purity saline minerals are required.

In the case of beneficiating trona, for example, the weight

recovery (weight of trona recovered/weight of trona in the

feed stream) from the density separation step is between

35 about 65% and about 95%. More preferably, the weight

recovery is between about 70% and about 90% and, most

preferably, the weight recovery is about 80%.

In an alternative embodiment, the impurity stream from

40 density separation can go through one or more scavenger

density separation step(s) to recover additional trona to

improve the overall recovery. The scavenger separation is

similar to the above-described density separation step. The

scavenger step recovers a portion of the impurity stream

45 from the rougher pass having the saline mineral in it and

combines that portion with the above-described recovered

stream to increase the overall yield from density separation

or recycles it to 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

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

55 above-described density separation process in that impurities

are removed from the stream by density separation. In

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 has a

density of 2.14, 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

65 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,

DETAILED DESCRIPTION OF THE

INVENTION

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of one embodiment

of the present invention.

separated from the +65 mesh fraction to produce a second

recovered portion, and the first and second recovered portions

are combined to produce a recovered saline mineral.

In another aspect of the present invention, a novel process

for calcining saline minerals is provided. The process generally

comprises heating the saline mineral in a calcining

vessel above its calcining temperature with a heat source to

calcine the saline mineral, wherein said heat source is not in

direct fluid communication with said saline mineral. The

saline mineral may comprise, for example, trona. In one

embodiment, the heating step includes heating a fluid (e.g.,

steam) and bringing the fluid into thermal communication

with the calcining vessel (e.g., utilizing a steam coil heat

exchanger positioned within the interior of the vessel). In

another embodiment, the calcining gases produced by the

calcining process are recycled back to the vessel inlet, such

as to provide a medium for fluidizing. To accomplish this, at

least a portion of calcining gas must be removed from the

process stream to accommodate for the gas produced by the

calcining process.

In yet another embodiment, water vapor may be removed

from the calcined gas to reduce significantly the amount of

gas emitted from the system. For example, water may be

condensed from the calcining gas utilizing a scrubber, which

also aids in removal of particulates from the gas stream.

The 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 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. Deposits of trona ore are located at several locations

throughout the world, including Wyoming (Green

River Formation), California (Searles Lake), Egypt, Kenya, 50

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. %) 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 (1-5 wt. %)

and the bulk of the remainder comprises shale consisting

predominantly of dolomite, clay, quartz and kerogen, and 60

traces of other impurities. Other samples of trona ore can

include different percentages of trona and impurities, as well

as include other impurities.

In the first aspect, the present process includes removing

a first portion of impurities from an ore containing saline

minerals by a density separation method. Density separation

methods are based on subjecting an ore to conditions such

6,092,665

5 6

higher magnetic susceptibility than trona. By practice of the

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

5 90 wt. % of the shale from the material being treated by

magnetic separation.

As noted above for the density and electrostatic separation

steps, the impurity stream from the rougher pass of the

magnetic separation process can go through one or more

10 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

15 the overall yield 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.

It should be appreciated that the above-identified process

steps could be performed in any order. Preferably, however,

the density separation is performed first, followed by electrostatic

separation and finally magnetic separation.

25 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

30 (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

partially act as the crushing medium, thus requiring less cost

35 in obtaining grinding media. 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, improved 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

45 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

50 100 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

55 general, the narrower the range of particle size within a

fraction, the higher the efficiency of removal of impurities.

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 between 3 and 10 fractions has been

60 found to be acceptable. Preferably, the number of fractions

is between 4 and 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

65 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).

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 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

comprise as much as 90% shortite. Such shortite may be

acceptable, for example, for certain applications in the glass

industry. The acceptability of the shortite in the glass industry

will depend upon the consistency and the relative lack of

iron in the product. In addition, for some trona deposits,

potentially valuable heavy minerals may be present. Such

minerals can be separated in the method and recovered.

The present invention further includes removing a second

portion of 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. The electrostatic 20

separation of the present invention can be accomplished by

any conventional electrostatic separation technique. U.S.

Pat. No. 4,341,744 discloses standard electrostatic separation

processes suitable for use in the present invention in col.

4, line 62 through col. 6, line 32, 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.

As noted above for the density separation step, the impurity

stream from the rougher pass of an electrostatic separation

process can go through a scavenger step to improve

the overall recovery. The scavenger step recovers a saline

mineral-containing portion of the impurity stream from the

rougher pass through electrostatic separation and combines

it with the above-described recovered stream to increase the

overall yield of the electrostatic separation step or otherwise

cycles it to other steps in the process. Furthermore, the 40

recovered stream from the rougher 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.

For example, electrostatic separation can be used to

separate trona from impurities having a higher electrical

conductivity, such as shale, mudstone or pyrite. It 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. By

practice of the present invention, utilizing electrostatic separation

can remove at least about 10 wt. %, more preferably,

about 50 wt. %, and most preferably, about 90 wt. % of the

more conductive mineral impurities from the is material

being treated by electrostatic separation.

The present process further includes a magnetic separation

step which subjects the ore to conditions such that

materials of different magnetic susceptibilities separate from

each other into a recovered stream and an impurity 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 that can be removed during

the magnetic separation step include shale which has a

6,092,665

In yet another embodiment of the present invention, the

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

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 is it 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 electrostatic and magnetic separation

steps. De-dusting can be particularly important before

electrostatic separation because the dust can otherwise interfere

with effective electrostatic separation. Such a

de-dusting step can 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 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.

The present invention provides a process for the separation

of saline minerals from an ore utilizing a dry beneficiation

technique, resulting in a high purity product, typically

greater than 85% purity, produced at low cost

compared to wet beneficiation processes. Utilizing the

above-described process, trona having about 98.8% purity

from an ore containing 90% trona has been obtained, compared

to less than about 97% purity for the prior art dry

beneficiation processes. The purity of recovered product can

be greater than about 97%, preferably greater than about

97.5%, and more preferably greater than about 98%. In

addition, by utilizing selective mining techniques and lower

weight recoveries for the separation steps, higher purities

can be obtained.

Utilizing the process of the present invention, recoveries

of greater than about 55% can be obtained. More preferably,

recoveries are greater than about 65% and, most preferably,

greater than about 75a. In the case of trona, the resulting

trona product can be used in many applications, especially

those requiring a purity of about 97.5% or greater, such as

in certain areas of the glass industry.

In the second aspect of the present invention, a process is

provided whereby impurities having the same or similar

density, magnetic properties and/or electrostatic properties

as a saline mineral in an ore can be effectively removed. As

used herein, the term "saline minerals" has the same meaning

as it is used in the description of the first aspect of the

present invention. The process recognizes and relies on the

fact that the apparent density of saline minerals, such as

trona, changes during calcining, while the apparent densities

of many impurities remain relatively constant during calcining.

A reduction in apparent density of the saline mineral

allows the impurities to be removed utilizing density

separation, even if the pre-calcined density of the trona is the

same as or similar to that of the impurity.

Accordingly, the second aspect of the present invention

comprises a process for recovering a saline mineral from an

ore containing the saline mineral and impurities. A schematic

diagram of a process embodying the second aspect of

the present invention is illustrated in the accompanying

FIGURE. The process may be performed utilizing each of

the illustrated process or, alternatively, bypassing some of

5 the illustrated processes. The process generally comprises

the steps of calcining the ore to alter the apparent density of

the saline mineral and separating a first portion of impurities

from the calcined ore by density separation to produce a

recovered saline mineral. As noted above, the impurities

10 may have a density which is similar to the density of the

un-calcined saline mineral, but which is sufficiently different

than the apparent density of the calcined saline mineral to be

readily susceptible to density separation.

The calcining step can be performed utilizing any appro-

15 priate calcining process. For example, direct heating utilizing

a rotary kiln or fluidized bed reactor can be utilized. In

a preferred embodiment, the calcining step is performed

utilizing an indirect heating process in a calcining vessel

such as a fluidized bed reactor at a temperature of at least

20 about 120° C. In the indirect heating process, the combustion

gases from the heat source are not in direct fluid

communication with the ore containing the saline mineral,

but rather provide heat to the ore by conduction through, for

example, heating coils, as described in more detail below. In

25 one embodiment, the calcining occurs at least about 140° C.

with a 20 minute residence time within a fluidized bed

reactor. Other calcining times and temperatures may also be

utilized as is known in the art.

The density separation step is based on subjecting the ore

30 to conditions such that materials of different apparent densities

physically separate from each other. In the case of

beneficiating uncalcined trona, having a density of about

2.14, density separation is relatively effective in removing

shortite, having a density of about 2.6; dolomite, having a

35 density of about 2.8-2.9; and pyrite, having a density of

about 5.0, as described above in more detail. On the other

hand, density separation of uncalcined trona is generally not

effective in separating impurities having a density close to

that of uncalcined trona, such as halite, which has a density

40 of about 2.17.

Therefore, in accordance with the second aspect of the

present invention, it has been discovered that the calcining

process reduces the apparent density of saline minerals. In

the case of trona, the apparent density reduces to less than

45 about 2.0. It is believed that such reduction in apparent

density is caused by the formation of voids within the trona

particles without a significant change in the particle size.

Thus, when a calcined trona particle is subjected to density

separation, such as on an air table, the particle will behave

50 approximately as if it were a particle of the same shape with

a uniform actual density lower than the actual density of

calcined trona. With such a reduction in the apparent density

of calcined trona, impurities such as halite can be separated

utilizing density separation methods based upon differences

55 in apparent density. Furthermore, the density separation of

other impurities, such as shortite, dolomite and pyrite is

significantly improved due to the larger difference between

the apparent densities of the trona and these impurities. The

density separation step may remove as much as 50%,

60 preferably 75%, and more preferably 90%, of these impurities.

The resulting purity of the trona is preferably at least

about 95%, and more preferably about 98%.

As noted above in more detail, the density separation step

is preferably a dry process; however, wet density separation

65 processes such as heavy media separation may be used as

well. Any known density separation technique could be used

for this step of the invention, including air tabling or dry

6,092,665

jigging. Further details of the density separation step are set

forth above in the description of the first aspect of the

invention.

In one embodiment of the second aspect of the invention,

as noted above, the step of heating the ore for calcining 5

includes indirect heating which comprises the steps of

heating a fluid and bringing the heated fluid into thermal

communication with the ore in the calcining vessel. This

step can be accomplished utilizing a heat source which

provides the heated fluid to coils positioned within the 10

interior of the calcining vessel. In one embodiment, the heat

source is a steam boiler and the fluid is steam. Alternatively,

the fluid may comprise oil or any other appropriate medium.

The step of heating the fluid can comprise the steps of

combusting an energy source to produce heat and combustion

gas, transferring at least a portion of the heat to the fluid, 15

and directing at least a portion of the combustion gas

through a combustion gas outlet which is not in direct fluid

communication with the calcining vessel.

The utilization of indirect heating for calcining the saline

mineral provides significant benefits in that it significantly 20

reduces the amount of gas flowing through the fluidized bed

because no combustion gas flows through the bed. In this

manner, a significantly lower amount of particulates from

the ore are entrained and need to be removed from exhaust

gas from the calcining operation. More specifically, the 25

amount of gas required for fluidization is about 80% less

than the amount of gas produced during the combustion

necessary to produce sufficient heat for the calcining process

(e.g., utilizing natural gas in a steam boiler). Accordingly, by

utilizing a source of gas for fluidization which is different 30

than the combustion gases, a smaller amount of fluidizing

gas can be used. Further, the smaller amount means that the

fluidizing gas will flow at lower velocities, thereby potentially

reducing particulate entrainment even further. In

addition, less fluidizing gas means that less gas needs to be

scrubbed for particulates before emission, thereby reducing 35

the costs of the calcining process.

It is well known that the calcining process produces

calcining gas having a significant amount of water vapor.

For example, calcining three moles of trona produces five

moles of water and one mole of carbon dioxide. In order to 40

reduce the amount of calcining gas exiting the system, the

process may further comprise the step of condensing at least

a portion of the water vapor from the calcining gas by, for

example, cooling the calcining gas. Such condensation step

will reduce the calcining gas volume by as much as %ths, 45

thereby reducing the amount of calcining gas which must be

treated. In addition to reducing the volume of gas exiting the

system, the condensing step also has a scrubbing effect on

the calcining gas by removing particulates from the calcining

gas. It is believed that the amount of particulates 50

removed is proportional to the amount of gas removed (i.e.,

as much as %ths or more). It is estimated that the particulate

emission from a process for calcining trona ore in a directfired

rotary calciner is typically about 6 lbs/ton of feed. By

practice of the present process, including indirect calcination

55 and condensing water from calcining gas, the particulate

emissions from calcination of trona ore can be less than

about 3 lbs/ton of feed, more preferably less than about 1.5

lbs/ton of feed and most preferably less than about 1 lbs/ton

of feed.

In a preferred embodiment, the condensing step for con- 60

densing water from gas produced during calcining comprises

two stages. In the first stage, a small amount (e.g., less

than about 5%) of the water vapor within the calcining gas

is condensed to significantly reduce the particulate content

of the gas. The first stage can be performed utilizing a 65

water-cooled condenser, such as a tubed condenser. In the

second stage, as much as 80% of the water vapor is

condensed. Because of the reduction in particulate content

resulting from the first stage, the water condensed from the

second stage is essentially distilled water grade. A third stage

may be added to further scrub particulates from the gas. For

example, a high-efficiency venturi scrubber or electrostatic

precipitator may be used.

The water which is removed during the condensing steps

can be utilized for other processes. For example, the condensed

water may be cooled (e.g., using air coolers) and then

recycled and used as the cooling medium to condense

further water vapor from the calcining gas by bringing the

cooled water into thermal communication with the precondensed

calcining gas. Further, the condensed water could

be utilized for wet separation processes in other areas of the

facility such as for treating fines, as described below. The

condensed water may also be treated and utilized for almost

any other appropriate purpose, such as for general water

usage in the facility (e.g., for cleaning, drinking water, etc.).

Calcining gas which is produced during the calcining

process may be removed from the calcining vessel through

a calcining gas outlet, and at least a portion of the calcining

gas (proportional to the amount of CO2 produced in the

calcining process) may be expelled through a stack. The

expelled gas is preferably heated prior to exiting through the

stack to inhibit condensation and plume formation at the

stack outlet. For example, the expelled gas can be mixed

with hot combustion gas from heating fluid for indirect

calcination.

Another portion of the calcining gas may be recycled back

to the inlet of the calcining vessel and utilized for heating

and fluidizing additional ore for calcining. Preferably, this

gas is recycled after the above-noted condensation step,

thereby resulting in dry CO2 as the heating and fluidizing

medium. The recycled gas may be heated (e.g., by steam

coils) in order to bring the gas up to a temperature prior to

entry into the calcining vessel. In one embodiment, the

recycled gas temperature is between about 1200 C. and about

2000 c., and is preferably about 1400 C. This recycling of

gas is beneficial in that it utilizes latent heat within the

calcining gas as part of the energy required for calcining,

rather than heating ambient temperature gas up to calcining

temperature. Further, such recycling reduces the gas requirements

and emissions of the process by eliminating the need

for fresh gas.

In another embodiment of the second aspect of the present

invention, the process further includes removing a second

portion of impurities by a magnetic separation method such

that materials of different magnetic susceptibilities separate

from each other into a recovered stream and an impurity

stream. With regard to the beneficiation of trona, typical

impurities that can be removed during the magnetic separation

step include shaley components, such as dolomitic

shale and oil shale, iron associated with the shaley

components, complex iron silicates, iron-bearing

carbonates, as well as other impurities having different

magnetic susceptibilities. Such shaley components typically

have a higher magnetic susceptibility than trona. Further

details of the magnetic separation step are set forth above in

the description of the first aspect of the invention.

It should be appreciated that the magnetic separation step

could be performed at any point in the separation process.

For example, magnetic separation may occur prior to calcining

and/or prior to the density separation step.

Furthermore, the ore may be subjected to density separation

prior to calcining to remove some impurities and then

subjected to another density separation step after calcining

to remove more impurities. Other separation techniques,

such as electrostatic separation, could also be incorporated

into the second aspect of the invention.

In another embodiment of the present invention, the saline

mineral-containing ore is crushed to achieve liberation of

6,092,665

impurities prior to the calcining step. Preferably, the ore is

crushed to at least about 6 mesh during the crushing step.

Further details of the crushing step are set forth above in the

description of the first aspect of the invention.

After crushing, fines are preferably removed from the ore. 5

In one embodiment, particles having a size less than about

200 mesh are removed and processed separately from the

remaining size fractions. Such fines are removed because

they are typically not processable utilizing dry separation

processes, such as air tabling. The about -200 mesh fraction 10

subsequently can be treated utilizing a wet separation

process, such as the slush process. The slush process generally

comprises mixing the calcined trona fines in a saturated

brine solution at between 40° C. and 80° C. to convert

the anhydrous sodium carbonate to monohydrate form. The

slurry is then heated to between 112° C. and 120° C. under 15

pressure to convert back to anhydrous form. The slurry is

then cooled, causing the sodium carbonate to crystallize

back to the monohydrate form. The crystallization process

squeezes out impurities and forms coarse sodium carbonate

particles. The particles are then screened and washed to 20

remove impurities. Subsequent calcining of the particles

converts the sodium carbonate back to anhydrous form.

In addition to processing the -200 mesh fraction as

discussed above, saline mineral particles falling between

about 65 mesh and about 200 mesh are typically not able to 25

be readily separated from impurities in that size fraction

utilizing conventional dry density separation processes, such

as air tabling. This aspect includes separately processing the

65x200 fraction to remove iron and shale. Surprisingly, it

has been found that iron impurities are concentrated in about 30

the -65 fraction of saline mineral-containing ore and in

particular, trona-containing ore. Thus, by removing the -65

fraction and processing it separately, a significant portion of

the iron is removed from the ore. The 65x200 fraction can

be wet processed, as described above, or can be magneti- 35

cally separated to remove shaley components and iron

associated therewith. After separating the impurities, the

65x200 fraction can be recombined with the beneficiated

larger size fractions, or it can be used for a different purpose

more suited to its particle size and purity.

The +65 mesh particles are sized into size fractions before 40

the density separation step. 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 during the density separation

step. On the other hand, narrow size fractions requires 45

a large number of fractions which may increase the cost of

the overall process. Further details of the sizing step are set

forth above in the description of the first aspect of the

invention.

The number of size fractions required for a particular 50

separating step depends in part on the difference in properties

between the minerals sought to be separated. For

example, in the density separation step, the larger the

difference between the densities of the saline mineral and the

impurity, the smaller the number of size fractions required 55

(i.e., the larger the allowed size variation within a particular

fraction). In the case of beneficiating trona, the calcining

step increases the difference between the apparent density of

the trona and at least some of the impurities. Accordingly, it

is believed that the process according to the second aspect of

the invention will allow the use of between 3 and 10 size 60

fractions. In one embodiment, the process utilizes as few as

5 size fractions, each having a wider range of particle size

within the fraction. Such reduction in the number of fractions

decreases the cost of the overall process. In addition,

or alternatively, it is believed that the process according to 65

the second aspect of the present invention may be utilized to

produce a higher grade product and/or higher recoveries.

It has been found that the above-identified processes for

beneficiating trona are also particularly adaptable for use in

the production of caustic for use in alumina production. By

transporting beneficiated and calcined trona ore to alumina

processing facilities and producing caustic from the beneficiated

trona, the total cost for caustic can be significantly

below that of caustic currently used in the alumina industry.

For this application, the trona-containing ore is beneficiated

and the resulting beneficiated trona is calcined to produce

soda ash (Na2C03 ). The soda ash is then converted to caustic

soda by conventional processes at an alumina plant and can

then be used in conventional alumina processing. For

example, the Bayer process can be used in which caustic

soda is mixed with bauxite to solubilize the aluminum

hydroxide in the bauxite to produce a sodium illuminate

solution. Alumina hydrate can be precipitated from the

solution and calcined to remove water therefrom.

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.

EXAMPLES 1-8

Eight samples of trona-containing ore from Bed 17 of the

Green River Formation in Wyoming were beneficiated in

accordance with the first aspect of the present invention.

Each of the samples was crushed to -10 mesh on a roll

crusher. The samples were allowed to air dry until they

attained a constant weight (about 24 hours). The samples

were subsequently screened at 20 mesh, 35 mesh, 65 mesh

and 150 mesh Tyler. Each of the four 150 plus size fractions

was then subjected to electrostatic separation to generate a

conductive and non-conductive stream. The non-conductive

stream resulting from the electrostatic separation regime for

each of the size fractions was subjected to high intensity

magnetic separation to generate a magnetic and nonmagnetic

stream. The resulting non-conductive/nonmagnetic

streams from each of the size fractions were then

subjected to a density separation step. A heavy liquid separation

was used for density separation in these examples.

The heavy liquid used was a mixture of acetylene tetrabromide

and kerosene. Since the saline mineral being beneficiated

was trona, having a specific gravity of 2.14; the major

impurity was shortite, having a specific gravity of 2.6; and

other impurities having a specific gravity lighter than 2.0

were present, density separations were made at specific

gravities of 2.0 and 2.3 to generate a 2.0x2.3 fraction which

is the trona fraction.

The data generated from the foregoing beneficiation processes

is shown in Tables 1-8. As can be seen from the

Tables, the purity of trona recovered ranged from 95.3 in

Example 2 to 98.8 in Example 3 (shown as soluble % in

2.0x2.3 S.G. separation). In addition, the effectiveness of the

density separation in improving trona purity can be seen by

comparing the Soluble % in the "Plus 65 mesh trona" line

(before density separation) with the Soluble % in the "2.0x

2.3 S.G." line (after density separation).

6,092,665

13 14

TABLE 1 TABLE 2

Weight Percent Weight Percent

Bene- Assay Bene- Assay

Frac- Sam- ficiated Insoluble Soluble Frac- Sam- ficiated Insoluble Soluble

Fraction tion pIe Product % Distr. % Distr. 10 Fraction tion pIe Product % Distr. % Distr.

Electrostatic and Magnetic Separation of

Trona-containing Waste Rock; Sample 1

Trona-containing Waste Rock; Sample 2

10 x 20 mesh

15 10 x 20 mesh

conductive stream 86.4 41.7 93.8 44.6 6.2 21.2

magnetic stream 2.0 1.0 67.3 0.7 32.7 2.6 conductive stream 57.6 27.6 87.7 40.9 12.3 8.3

non-conductive/ 11.6 5.6 24.6 69.5 4.4 30.5 14.0 magnetic stream 3.7 1.8 68.1 2.0 31.9 1.4

non-magnetic non-conductive/ 38.7 18.6 49.4 19.1 6.0 80.9 36.9

stream 20 non-magnetic

stream

Total 100.0 48.3 90.5 49.8 9.5 37.7

20 x 35 mesh Total 100.0 47.9 60.4 48.9 39.6 46.6

20 x 35 mesh

conductive stream 56.9 12.1 91.9 12.6 8.1 8.0 25

magnetic stream 9.5 2.0 83.6 1.9 16.4 2.7 conductive stream 30.0 3.7 81.3 5.0 18.7 1.7

non-conductive/ 33.6 7.1 31.3 83.2 6.8 16.8 9.8 magnetic stream 15.9 2.0 62.9 2.1 37.1 1.8

non-magnetic non-conductive/ 54.1 6.6 17.7 46.7 5.2 53.3 8.7

stream non-magnetic

30 stream

Total 100.0 21.2 88.2 21.3 11.8 20.5

35 x 65 mesh Total 100.0 12.3 59.6 12.4 40.4 12.2

35 x 65 mesh

conductive stream 28.6 3.9 91.5 4.1 8.5 2.7

magnetic stream 19.1 2.6 87.0 2.6 13.0 2.8 35 conductive stream 45.8 9.1 82.8 12.8 17.2 3.9

non-conductive/ 52.2 7.1 31.3 85.3 6.9 14.7 8.6 magnetic stream 13.5 2.7 69.3 3.2 30.7 2.0

non-magnetic non-conductive/ 40.7 8.1 21.6 47.7 6.5 52.3 10.4

stream non-magnetic

stream

Total 100.0 13.6 87.4 13.6 12.6 14.1 40

65 x 150 mesh Total 100.0 20.0 66.7 22.5 33.3 16.3

65 x 150 mesh

conductive stream 50.8 3.7 87.8 3.7 12.2 3.7

magnetic stream 8.9 0.7 82.7 0.6 17.3 0.9 conductive stream 22.0 1.6 82.9 2.2 17.1 0.7

non-conductive/ 40.3 2.9 12.9 77.4 2.6 22.6 5.4 45 magnetic stream 20.1 1.5 74.3 1.8 25.7 0.9

non-magnetic non-conductive/ 57.9 4.2 11.2 42.0 3.0 58.0 6.0

stream non-magnetic

stream

Total 100.0 7.3 83.2 6.9 16.8 10.0

Minus 150 mesh 9.6 77.4 8.4 22.6 17.7 50 Total 100.0 7.3 57.5 7.1 42.5 7.6

Plus 65 mesh trona 19.9 80.1 18.1 19.9 32.4 Minus 150 mesh 12.5 43.6 9.2 56.4 17.3

Trona Prod., 22.8 100.0 79.7 20.7 20.3 37.8 Plus 65 mesh 33.4 31.6 17.8 68.4 56.0

Calc. trona

Trona + 32.4 79.0 29.2 21.0 55.5 Trona Prod., Calc. 37.6 100.0 32.7 20.8 67.3 62.0

minus 55 Trona + minus 50.1 35.5 30.0 64.5 79.3

150 Calc. 150 Calc.

Sample Calc. 100.0 87.8 100.0 12.2 100.0 Sample Calc. 100.0 59.2 100.0 40.8 100.0

Heavy Liquid Density Separation of Plus 65 Mesh Heavy Liquid Density Separation of Plus 65 Mesh

Non-Magnetic/Non-Conductive Sample 1 Non-Magnetic/Non-Conductive Sample 2

<2.0 S.G. 0.2 0.0 <2.0 S.G. 6.0 2.0

2.0 x 2.3 S.G. 19.0 3.8 3.4 0.1 96.6 29.8 2.0 x 2.3 S.G. 63.0 21.0 4.7 1.7 95.3 49.1

>2.3 S.G. 80.8 16.1 98.3 18.0 1.7 2.5 >2.3 S.G. 31.0 10.3 92.3 16.1 7.7 6.9

Total 100.0 19.9 80.1 18.1 19.9 32.4 65 Total 100.0 33.4 31.6 17.8 68.4 56.0

6,092,665

15 16

TABLE 3 TABLE 4

Weight Percent Weight Percent

Bene- Assay Bene- Assay

Frac- Sam- ficiated Insoluble Soluble Frac- Sam- ficiated Insoluble Soluble

Fraction tion pIe Product % Distr. % Distr. 10 Fraction tion pIe Product % Distr. % Distr.

Electrostatic and Magnetic Separation of Electrostatic and Magnetic Separation of

Trona-Containing Waste Rock; Sample 3 Trona-containing Waste Rock; Sample 4

10 x 20 mesh 15 10 x 20 mesh

conductive stream 26.1 13.2 30.1 50.8 69.9 10.0 conductive stream 11.7 6.4 11.3 22.3 88.7 5.9

magnetic stream 4.4 2.2 4.6 1.3 95.4 2.3 magnetic stream 6.3 3.5 3.0 3.2 97.0 3.5

non-conductive/ 69.5 35.2 58.8 2.4 10.8 97.6 37.3 non-conductive/ 82.0 45.0 68.3 1.9 26.3 98.1 45.6

non-magnetic 20 non-magnetic

stream stream

Total 100.0 50.6 9.7 63.0 90.3 49.6 Total 100.0 54.8 3.1 51.8 96.9 54.9

20 x 35 mesh 20 x 35 mesh

conductive stream 24.9 4.0 25.0 12.7 75.0 3.2 conductive stream 15.4 2.2 14.3 9.5 85.7 1.9

magnetic stream 5.8 0.9 5.6 0.7 94.4 1.0 magnetic stream 10.8 1.5 5.4 2.5 94.6 1.5

non-conductive/ 69.3 11.1 18.5 3.0 4.3 97.0 11.7 non-conductive/ 73.8 10.3 15.7 2.6 8.3 97.4 10.4

non-magnetic non-magnetic

stream 30 stream

Total 100.0 16.0 8.6 17.7 91.4 15.9 Total 100.0 14.0 4.7 20.3 95.3 13.8

35 x 65 mesh 35 x 65 mesh

conductive stream 12.3 1.3 21.3 3.7 78.7 1.1 35 conductive stream 18.7 1.4 11.1 4.9 88.9 1.3

magnetic stream 4.0 0.4 6.6 0.4 93.4 0.4 magnetic stream 2.1 0.2 10.5 0.5 89.5 0.1

non-conductive/ 83.7 9.1 15.2 4.1 4.8 95.9 9.5 non-conductive/ 79.2 6.0 9.2 3.8 7.1 96.2 6.0

non-magnetic non-magnetic

stream stream

Total 100.0 10.9 6.3 8.8 93.7 11.1 Total 100.0 7.6 5.3 12.5 94.7 7.5

65 x 150 mesh 65 x 150 mesh

conductive stream 27.5 1.8 8.2 1.9 91.8 1.8 conductive stream 17.9 1.1 7.0 2.3 93.0 1.0

magnetic stream 3.9 0.3 4.4 0.1 95.6 0.3 45 magnetic stream 4.4 0.3 2.5 0.2 97.5 0.3

non-conductive/ 68.7 4.4 7.4 3.6 2.0 96.4 4.6 non-conductive/ 77.7 4.6 6.9 3.0 4.2 97.0 4.6

non-magnetic non-magnetic

stream stream

Total 100.0 6.5 4.9 4.0 95.1 6.7 50 Total 100.0 5.9 3.7 6.7 96.3 5.8

Minus 150 mesh 16.0 3.2 6.6 96.8 16.8 Minus 150 mesh 17.7 1.6 8.7 98.4 18.0

Plus 65 mesh trona 55.4 2.8 19.8 97.2 58.4 Plus 65 mesh trona 61.3 2.2 41.7 97.7 66.6

Trona Prod., Calc. 59.8 100.0 2.9 21.9 97.1 63.1 Trona Prod., Calc. 65.9 100.0 2.3 45.9 97.8 78.7

Trona + minus 75.9 2.9 28.4 97.1 79.9 Trona + minus 83.6 2.1 54.6 97.9 84.6

150 Calc. 150 Calc.

Sample Calc. 100.0 7.8 100 92.2 100 Sample Calc. 100.0 3.2 100.0 96.8 100.0

Heavy Liquid Density Separation of Plus 65 Mesh Heavy Liquid Density Separation of Plus 65 Mesh

Non-Magnetic/Non-Conductive Sample 3 Non-Magnetic/Non-Conductive Sample 4

<2.0 S.G. 0.2 0.1 <2.0 S.G. 0.4 0.0

2.0 x 2.3 S.G. 96.1 53.2 1.2 8.2 98.8 57.1 2.0 x 2.3 S.G. 98.6 60.5 2.0 37.3 98.0 61.2

>2.3 S.G. 3.7 2.1 44.5 11.7 55.5 1.4 >2.3 S.G. 1.0 0.6 23.3 4.4 76.7 5.3

Total 100.0 55.4 2.8 19.8 97.2 58.4 65 Total 100.0 61.3 2.2 41.7 97.7 66.6

6,092,665

17 18

TABLE 5 TABLE 6

Weight Percent Weight Percent

Bene- Assay Bene- Assay

Frac- Sam- ficiated Insoluble Soluble Frac- Sam- ficiated Insoluble Soluble

Fraction tion pIe Product % Distr. % Distr. 10 Fraction tion pIe Product % Distr. % Distr.

Electrostatic and Magnetic Separation of Electrostatic and Magnetic Separation of

Trona-Containing Waste Rock; Sample 5 Trona-Containing Waste Rock; Sample 6

10 x 20 mesh 15 10 x 20 mesh

conductive stream 23.0 10.9 37.8 48.0 62.2 7.4 conductive stream 28.3 14.1 18.0 47.7 82.0 12.2

magnetic stream 5.2 2.5 3.8 1.1 96.2 2.6 magnetic stream 4.4 2.2 2.8 1.1 97.2 2.2

non-conductive/ 71.9 34.2 56.2 3.0 11.9 97.0 36.3 non-conductive/ 67.3 33.4 57.3 2.1 13.2 97.9 34.5

non-magnetic 20 non-magnetic

stream stream

Total 100.0 47.6 11.0 61.0 89.0 46.4 Total 100.0 49.7 6.6 62.0 93.4 49.0

20 x 35 mesh 20 x 35 mesh

conductive stream 21.3 3.7 25.7 11.0 74.3 3.0 conductive stream 17.5 2.7 21.4 10.8 78.6 2.2

magnetic stream 10.2 1.8 5.2 1.1 94.8 1.8 magnetic stream 6.7 1.0 3.8 0.7 96.2 1.0

non-conductive/ 68.5 11.9 19.5 3.5 4.8 96.5 12.5 non-conductive/ 75.8 11.6 19.9 3.0 6.5 97.0 11.9

non-magnetic non-magnetic

stream 30 stream

Total 100.0 17.3 8.4 16.9 91.6 17.4 Total 100.0 15.3 6.3 18.1 93.7 15.1

35 x 65 mesh 35 x 65 mesh

conductive stream 19.8 2.2 17.0 4.4 83.0 2.0 35 conductive stream 13.0 1.1 16.2 3.5 83.8 1.0

magnetic stream 5.9 0.7 7.4 0.6 92.6 0.7 magnetic stream 6.0 0.5 6.7 0.7 93.3 0.5

non-conductive/ 74.3 8.4 13.8 4.6 4.5 95.4 8.7 non-conductive/ 81.0 7.1 12.3 2.8 3.8 97.2 7.3

non-magnetic non-magnetic

stream stream

Total 100.0 11.3 7.2 9.5 92.8 11.4 Total 100.0 8.8 4.8 7.9 95.2 8.9

65 x 150 mesh 65 x 150 mesh

conductive stream 19.7 1.6 11.0 2.1 89.0 1.6 conductive stream 16.5 1.3 6.6 1.6 93.4 1.3

magnetic stream 3.4 0.3 3.8 0.1 96.2 0.3 45 magnetic stream 4.2 0.3 3.6 0.2 96.4 0.3

non-conductive/ 76.8 6.4 10.5 4.4 3.3 95.6 6.7 non-conductive/ 79.3 6.1 10.5 2.2 2.5 97.8 6.3

non-magnetic non-magnetic

stream stream

Total 100.0 8.3 5.7 5.5 94.3 8.6 50 Total 100.0 7.7 3.0 4.3 97.0 7.9

Minus 150 mesh 15.5 4.0 7.2 96.0 16.3 Minus 150 mesh 18.5 2.2 7.7 97.8 19.1

Plus 65 mesh trona 54.5 3.4 21.2 96.5 64.3 Plus 65 mesh trona 52.1 2.4 23.5 97.6 60.1

Trona Prod., Calc. 60.8 100.0 3.5 24.5 96.6 72.0 Trona Prod., Calc. 58.3 100.0 2.4 26.0 97.6 71.3

Trona + minus 76.3 3.6 31.7 96.4 80.5 Trona + minus 76.8 2.3 33.7 97.7 79.2

150 Calc. 150 Calc.

Sample Calc. 100 8.6 100 91.4 100 Sample Calc. 100.0 5.3 100.0 94.7 100.0

Heavy Liquid Density Separation of Plus 65 Mesh Heavy Liquid Density Separation of Plus 65 Mesh

Non-Magnetic/Non-Conductive Sample 5 Non-Magnetic/Non-Conductive Sample 6

<2.0 S.G. 0.3 0.2 <2.0 S.G. 0.4 0.2

2.0 x 2.3 S.G. 92.6 50.4 2.5 14.6 97.5 53.8 2.0 x 2.3 S.G. 98.8 51.5 2.0 19.4 98.0 53.3

>2.3 S.G. 7.1 3.9 20.2 9.1 79.8 10.5 >2.3 S.G. 0.8 0.4 52.5 4.1 47.5 6.8

Total 100.0 54.5 3.4 21.2 96.5 64.3 65 Total 100.0 52.1 2.4 23.5 97.6 60.1

6,092,665

19 20

TABLE 7 TABLE 8

Weight Percent

5 Bene- Assay

Bene- Assay

Frac- Sam- ficiated Insoluble Soluble

Fraction tion pIe Product % Distr. % Distr.

Fraction tion pIe Product % Distr. % Distr. 10 Electrostatic and Magnetic Separation of

Trona-Containing Waste Rock; Sample 8

Electrostatic and Magnetic Separation of

10 x 20 mesh

Trona-Containing Waste Rock; Sample 7

conductive stream 18.8 6.2 35.0 23.6 65.0 4.5

10 x 20 mesh 15 magnetic stream 1.3 0.4 28.7 1.4 71.3 0.4

non-conductive/ 79.9 26.5 40.9 4.4 12.6 95.6 27.9

conductive stream 0.0 0.0 0.0 0.0

non-magnetic

stream

magnetic stream 15.8 5.0 34.1 16.5 65.9 3.6

non-conductive/ 84.2 26.3 34.6 9.7 24.9 90.3 26.5 Total 100.0 33.2 10.5 37.6 89.5 32.7

non-magnetic 20

20 x 35 mesh

stream conductive stream 13.6 3.0 45.7 15.0 54.3 1.8

magnetic stream 2.1 0.5 40.9 2.1 59.1 0.3

Total 100.0 31.3 13.6 41.3 86.4 30.2 non-conductive/ 84.3 18.9 29.2 6.3 12.9 93.7 19.5

20 x 35 mesh

non-magnetic

stream

conductive stream 0.0 0.0 0.0 0.0 Total 100.0 22.4 12.4 30.0 87.6 21.6

magnetic stream 8.0 1.7 29.3 4.8 70.7 1.3 35 x 65 mesh

non-conductive/ 92.0 19.3 25.3 7.7 14.5 92.3 19.9

conductive stream 10.0 1.1 50.2 5.9 49.8 0.6

non-magnetic magnetic stream 3.2 0.3 48.9 1.8 51.1 0.2

stream 30 non-conductive/ 86.7 9.3 14.4 6.9 7.0 93.1 9.6

non-magnetic

Total 100.0 21.0 9.4 19.2 90.6 21.2

stream

35 x 65 mesh Total 100.0 10.8 12.6 14.7 87.4 10.4

65 x 150 mesh

conductive stream 0.0 0.0 0.0 0.0 35

magnetic stream 11.4 2.2 23.7 5.1 76.3 1.9

conductive stream 12.7 1.5 22.1 3.6 77.9 1.3

magnetic stream 2.5 0.3 32.0 1.0 68.0 0.2

non-conductive/ 88.6 17.0 22.3 6.4 10.6 93.6 17.8 non-conductive/ 84.8 10.0 15.4 3.6 3.9 96.4 10.6

non-magnetic non-magnetic

stream stream

Total 100.0 11.8 6.7 8.5 93.3 12.1

Total 100.0 19.2 8.4 15.7 91.6 19.6 Minus 150 mesh 21.9 3.9 9.2 96.1 23.2

65 x 150 mesh Plus 65 mesh trona 54.7 5.5 32.5 94.5 57.0

Trona Prod., Calc. 64.7 100.0 5.2 36.4 94.8 67.6

conductive stream 0.0 0.0 0.0 0.0

Trona + minus 86.6 4.9 45.6 95.1 90.8

150 Calc.

magnetic stream 6.5 0.9 21.1 1.9 78.9 0.8 45 Sample Calc. 100.0 9.2 100.0 90.8 100.0

non-conductive/ 93.5 13.6 17.8 7.6 10.0 92.4 14.0 Heavy Liquid Density Separation of Plus 65 Mesh

non-magnetic Non-Magnetic/Non-Conductive Sample 8

stream <2.0 S.G. 0.3 0.2

2.0 x 2.3 S.G. 97.0 53.1 2.0 11.5 98.0 57.3

Total 100.0 14.5 8.5 12.0 91.5 14.8 50 >2.3 S.G. 2.7 1.5

Minus 150 mesh 14.0 8.7 11.8 91.3 14.2 Total 100.0 54.7 5.5 32.5 94.5 57.0

Plus 65 mesh trona 62.7 8.2 49.9 91.9 78.1

Trona Prod., Calc. 76.3 100.0 8.1 60.0 91.8 77.5

Trona + minus 90.2 8.2 71.8 91.8 92.4

55 EXAMPLE 9

150 Calc.

Sample Calc. 100.0 10.3 100.0 89.7 100.0 An ore sample containing trona, recovered from Bed 17

Heavy Liquid Density Separation of Plus 65 Mesh of the Green River Formation in Wyoming, was beneficiated

Non-Magnetic/Non Conductive Sample 7 using the process described below and the results are rep-

60 resented by the data in Table 9. The ore was a commercially

<2.0 S.G. 0.2 0.1 available trona-containing material identified as T-50, avail-

2.0 x 2.3 S.G. 93.0 58.3 4.2 23.8 95.8 62.2 able from Solvay Minerals S.A., Green River, Wyo. The

>2.3 S.G. 6.8 4.3 63.0 26.1 37.0 15.9 T-50 material has a trona purity of about 95% and a size

range of 20x150 mesh Tyler.

Total 100.0 62.7 8.2 49.9 91.9 78.1 65 The ore sample was first classified using a screening

process to divide the ore sample into three size fractions:

+35 mesh, 35x65 mesh, and -65 mesh. After screening, the

6,092,665

The cumulative products of the entire recovery process

are represented by the data in the third column at the end of

Table 9. The data represents the weight percentage of

non-magnetic, non-conductor material recovered from the

combined light and heavy density fractions and from the

ultra-heavy density fraction. As can be seen from the Table,

91.3% of the original sample was recovered as nonmagnetic,

non-conductive material. The trona purity of the

recovered material was determined. The trona product from

the lights plus heavies had a purity of 98.2%. The trona

product from the ultra-heavies, which contained the shortite,

had a purity of 88.9%. Comparison of these purities illustrates

the benefit of removing shortite.

individually magnetically separated utilizing an induced roll

magnetic separator. The conductors from each of the electrostatic

separation processes were not subjected to magnetic

separation. The magnetic separation process separated each

5 incoming sample into two fractions: magnetic and nonmagnetic.

The weights and weight percentages of each

magnetically separated fraction are listed in the three columns

of data in Table 9, as described above.

+35 mesh and 35x65 mesh fractions were each separated on

an air table into three density fractions: ultra-heavy, heavy

and light.

After air tabling, each of the density fractions which were

air tabled, and the -65 mesh size fraction that was not air

tabled, were electrostatically separated by a high tension

separator. To improve trona recovery, as seen in Table 9, the

light and heavy density fractions from the +35 mesh size

fraction were combined and electrostatically separated

together. Similarly, the light and heavy density fractions 10

from the 35x65 mesh size fraction were electrostatically

separated together. Electrostatic separation was further performed

on the ultra-heavy fraction from the +35 mesh size

fraction, the ultra-heavy fraction from the 35x65 mesh size

fraction, and the -65 mesh size fraction that was not air 15

tabled. Each of the above-identified electrostatic separation

processes divided the sample into three electrostatic fractions:

conductors, middlings, and non-conductors. The

respective weights and weight percentages of each electrostatic

fraction are listed in the three columns of data in Table 20

9, as noted above.

The non-conductors and middlings from each of the

above-referenced electrostatic separation processes were

TABLE 9

Density, Electrostatic and Magnetic Separation of Trona Ore, Sample 9

Weight (g, unless _----'-W""e"f.ig"'h"-.t",Pe""r",ce",n,,-t_ Purity

Separation otherwise noted) Fraction* Sample** (% trona)

SCREENING

plus 35 mesh

35 x 65 mesh

minus 65 mesh

362lb

482lb

140lb

36.8

49.0

14.2

36.8

49.0

14.2

Total 984lb

AIR TABLE SEPARATIONS

100.0 100.0

plus 35 mesh

Ull. Heavy

Heavy

Lights

Total

35 x 65 mesh

Ull. Heavy

Heavy

Lights

1605 4.2 1.5

1814 4.7 1.7

34960 91.1 33.5

38379 100.00 36.8

800 2.4 1.2

1603.5 4.7 2.3

31560 92.9 45.5

Total

minus 65 mesh

33963.5 100.0 49.0

not air tabled

HIGH TENSION ELECTROSTATIC SEPARATIONS (HI)

plus 35 mesh air table lights + heavies

Condo 190.8 7.4 2.6

Midd 230.5 8.9 3.1

Non-Cond. 2159.5 83.7 29.5

Total 2580.8 100.0 35.3

35 x 65 mesh air table lights + heavies

Condo 90.4 4.5 2.2

Midd 199.3 10.0 4.8

Non-Cond. 1709.5 85.5 40.9

Total 1999.2 100.0 47.8

plus 35 mesh air table ultra heavies

Condo 467.3 29.2 0.4

6,092,665

TABLE 9-continued

Density, Electrostatic and Magnetic Separation of Trona Ore, Sample 9

Weight (g, unless Weight Percent Purity

Separation otherwise noted) Fraction * Sample** (% trona)

Midd 188.7 11.8 0.2

Non-Cond. 943 59.0 0.9

Total 1599 100.0 1.5

35 x 65 mesh air table ultra heavies

Condo 97 12.1 0.1

Midd 106.8 13.4 0.2

Non-Cond. 595 74.5 0.9

Total 798.8 100.0 1.2

minus 65 mesh

Condo 23.4 1.4 0.2

Midd 96.9 6.0 0.9

Non-Cond. 1500.6 92.6 13.2

Total 1620.9 100.0 14.2

plus 35 mesh Non Condo from lights + heavies

HI Mag. 22.6 1.0 0.31

HI Non Mag. 2136.0 99.0 29.19

Total 2158.6 100.0 29.50

35 x 65 mesh Non Condo from lights + heavies

HI Mag. 61.1 4.1 1.67

HI Non Mag. 1438.1 95.9 39.23

Total 1499.2 100.0 40.90

plus 35 mesh Non Condo from ultra heavies

HI Mag. 11.2 1.2 0.01

HI Non Mag. 931.7 98.8 0.90

Total 942.9 100.0 0.91

35 x 65 mesh Non Condo from ultra heavies

HI Mag. 53.1 8.9 0.08

HI Non Mag. 541.7 91.1 0.78

Total 594.8 100.0 0.86

minus 65 mesh Non Condo

HI Mag. 59.9 3.5 0.46

HI Non Mag. 1649.0 96.5 12.71

Total 1708.9 100.0 13.17

plus 35 mesh HT Mid from lights + heavies

HI Mag. 15.6 7.8 0.25

HI Non Mag. 183.8 92.2 2.90

Total 199.4 100.0 3.15

35 x 65 mesh HT Mid from lights + heavies

HI Mag. 13.8 6.0 0.29

HI Non Mag. 216.9 94.0 4.48

Total 230.7 100.0 4.77

minus 65 mesh HT Mid

HI Mag. 11.8 12.2 0.02

HI Non Mag. 85.1 87.8 0.16

Total 96.9 100.0 0.18

plus 35 mesh HT Mid from ultra heavies

HI Mag. 7.6 4.0 0.01

HI Non Mag. 181.2 96.0 0.15

Total 188.8 100.0 0.15

6,092,665

TABLE 9-continued

Density, Electrostatic and Magnetic Separation of Trona Ore, Sample 9

Weight (g, unless __W-,-,-"e.·l g.",ht,-,P,-,e",rc",e",n,,-t_ Purity

Separation

35 x 65 mesh ill Mid from ultra heavies

otherwise noted) Fraction* Sample** (% trona)

HI Mag.

HI Non Mag.

Total

Recovered from lights + heavies

6.9

100.0

106.9

CUMULATIVE PRODUCTS

6.5

93.5

100.0

0.05

0.80

0.85

Primary non mag, non conductor

Scavo non mag, non conductor

Subtotal

Recovered from ultra heavies

Primary non mag, non conductor

Scavo non mag, non conductor

Subtotal

Total non mag, non conductor (inc!. - 65 mesh)

Total conductor

Total HI magnetics

Head Calc. from all test products

*Based on feed to separation as 100%

**Based on original sample as 100%

EXAMPLE 10

This example illustrates beneficiation of trona using air

tabling, electrostatic separation and magnetic separation,

and demonstrates a relationship between breadth of size

fractions and effectiveness of air tabling as the density

separation method by comparison with heavy liquid separation.

A sample of bulk trona from Bed 17 of the Green River

Formation in Wyoming was crushed to -6 mesh. The sample

was subsequently sized into size fractions of 6x10 mesh,

lOx20 mesh, 20x35 mesh, 35x65 mesh (Tyler mesh). Each

of the plus 65 mesh size fractions was then subjected to

initial density separation on an air table (Rougher Pass). The

Rougher Pass light fractions were subsequently sent through

a cleaner pass and for the 6x10 mesh fraction, the heavy

fraction was sent to a scavenger pass. The resulting separations

are shown in Table 10.1.

Each of the size fractions was then subsequently beneficiated

using either magnetic separation (in the case of 6xlO

mesh fraction) or electrostatic separation and magnetic

separation. The portions of material from each separation

reporting to various product streams are shown in Table

10.1.

The non-magnetic, in the case of the 6x10 mesh fraction,

and the non-magnetic/non-conductive fractions were then

further analyzed by conducting a second density separation

based on heavy liquid separation to identify what portion of

impurities which are separable by density separation had not

been removed in the earlier air tabling step. The results of

this analysis are shown in Table 10.2. The column entitled

">2.3 S.G., %" identifies the total amount of material

separated from the beneficiated ore by the additional heavy

81.13 98.2

7.54 94.4

88.67 98.0

1.68 85.0

0.94 95.7

2.62 88.9

91.30 97.7

5.56 55.2

3.14 80.3

100.00 94.8

30 liquid density separation step. Additionally, that column

shows subcolumns titled "Plus" and "Minus." These two

subcolumns represent a breakdown of the "Total" percentage

of material which is greater than 2.3 S.G. which falls

into either the coarser or finer portion of the particular

35 stream. For example, the 6xlO mesh fraction was broken

down into a 6x8 mesh fraction and an 8xlO mesh fraction.

Thus, by comparing the "Plus" and "Minus" subcolumns of

the ">2.3 S.G., %," it can be seen that inefficiency in the air

tabling density separation tended to be at smaller particle

40 sizes within each size fraction because most of the higher

specific gravity material left by air tabling was in the smaller

particle sizes (the "Minus" subcolumn).

The columns titled "Insoluble Assay" and "Soluble

Assay" provide data on the portion of each stream which is

45 insoluble (i.e., impurity) before heavy liquid separation

("Total" subcolumn) and after heavy liquid separation

(,,<2.3 S.G." subcolumn). Thus, for example, the purity of

products resulting from beneficiating ore using air tabling

can be seen in the "Total" subcolumn of the "Soluble Assay"

50 column for each of the different streams. This purity can be

compared with the subsequent column, having a higher

purity, which identifies the purity of the beneficiated material

with the subsequent heavy liquid separation to indicate

a theoretical purity based on perfect density separation. In

55 addition, the improvement in trona purity between the

non-magnetic/non-conductive product which was not air

tabled and the non-magnetic/non-conductive product which

was air tabled can be seen by comparing the "Total NonMagnetic/

Non-Conductive from Untabled Feed" line with

60 the "Total Non-MagneticlNon-Conductive from Cleaner

Lights" line in the "Cumulative Products" section of Table

10.2.

6,092,665

27 28

TABLE 10.1 TABLE 1O.1-continued

Data from Air Table Tests on Bulk Trona Sample Crushed to Minus 6

Mesh Data from Air Table Tests on Bulk Trona Sample Crushed to Minus 6

Weight. % of

Mesh

Product Feed Size Fraction Sample

Weight, % of

6 x 10 MESH

Rougher Pass Product Feed Size Fraction Sample

Heavies 17.7 17.7 7.9

Cleaner Pass

Lights 82.3 82.3 36.7

Feed Calc. 100.0 100.0 44.6

Scavenger Pass 15 Heavies 6.8 6.3 0.8

Heavies 2.8 3.1 0.2 Lights 93.2 85.9 10.6

Lights 97.2 17.2 7.7

Feed Calc. 100.0 92.2 11.3

Feed Calc. 100.0 20.3 7.9

Cleaner Pass 35 x 65 MESH

Heavies 1.5 1.2 0.6

Lights 98.5 81.1 36.2 Rougher Pass

Feed Calc. 100.0 82.3 36.7

10 x 20 MESH

Heavies 3.8 3.8 0.2

Rougher Pass 25 Lights 96.2 96.2 5.4

Feed Calc. 100.0 100.0 5.6

Heavies 7.6 7.6 0.9

Lights 92.4 92.4 11.4 Cleaner Pass

Feed Calc. 100.0 100.0 12.3

Cleaner Pass

Heavies 0.7 0.7 0.0

Heavies 2.5 2.3 0.3 Lights 99.3 95.5 5.3

Lights 97.5 90.1 11.1

Feed Calc. 100.0 96.2 5.4

Feed Calc. 100.0 92.4 11.4

20 x 35 MESH MINUS 65 MESH (not air tabled) 25.2

TOTAL FEED CALC. 100.0

Rougher Pass 35

Heavies 7.8 7.8 1.0

Lights 92.2 92.2 11.3

Feed Calc. 100.0 100.0 12.3

TABLE 10.2

Data from Electrostatic and Induced Roll Separations on Air Table Products

Feed Crushed to minus 6 mesh

Insoluble Soluble

Weight Percent >2.3 S.G.. % >2.3 S.G.. Dist.. % Assay, % of Assay, % of

Product Feed Sample Plus Minus Total Plus Minus Size Total <2.3 SG Total <2.3 SG

6 x 10 MESH

Not Tabled

Mag 9.0 4.0

Non Mag 91.0 40.6 0.47 0.74 1.21 100.0 100.0 100.0 3.8 2.3 96.2 97.7

Feed Calc. 100.0 44.6

Rougher Lights

Mag 12.2 4.5

Non Mag 87.8 32.2 0.17 0.86 1.03 28.7 92.3 67.6 3.2 2.3 96.8 97.7

Feed Calc. 100.0 36.7

Scavenger Lights

Mag 4.6 0.4

Non Mag 95.4 7.3 1.02 2.26 3.28 39.3 55.3 49.0 6.7 2.4 93.3 97.6

Feed Calc. 100.0 7.7

Cleaner Lights

Mag 11.6 4.2

Non Mag 88.4 32.0 0.1 0.86 0.96 16.8 91.6 62.5 3.2 2.3 96.8 97.7

6,092,665

29 30

TABLE lO.2-continued

Data from Electrostatic and Induced Roll Separations on Air Table Products

Feed Crushed to minus 6 mesh

Insoluble Soluble

Weight Percent >2.3 S.G., % >2.3 S.G., Dist., % Assay, % of Assay, % of

Product Feed Sample Plus Minus Total Plus Minus Size Total <2.3 SG Total <2.3 SG

Feed Calc. 100.0 36.2

10 x 20 MESH

Not Tabled

Condo 20.6 2.5

Mag 1.7 0.2

Non Mag/Non Condo 77.6 9.6 0.6 1.32 1.92 100.0 100.0 100.0 5.1 3.1 94.9 96.9

Feed Calc. 100.0 12.3

Rougher Lights

Condo 15.0 1.7

Mag 2.4 0.3

Non Mag/Non Condo 82.6 9.4 0.06 0.52 0.58 9.9 38.8 29.8 3.6 3.1 96.4 96.9

Feed Calc. 100.0 11.4

Cleaner Lights

Condo 9.9 1.1

Mag 2.1 0.2

Non Mag/Non Condo 88.0 9.8 0.01 0.55 0.56 1.7 42.6 29.8 3 2.5 97 97.5

Feed Calc. 100.0 11.1

20 x 35 MESH

Not Tabled

Condo 18.2 2.2

Mag 2.9 0.4

Non Mag/Non Condo 78.9 9.7 0.62 2.24 2.86 100.0 100.0 100.0 5.4 3.1 94.6 96.9

Feed Calc. 100.0 12.3

Rougher Lights

Condo 15.8 1.8

Mag 2.3 0.3

Non Mag/Non Condo 81.9 9.3 0.15 1.93 2.08 23.1 82.2 69.4 4.7 3.1 95.3 96.9

Feed Calc. 100.0 11.3

Cleaner Lights

Condo 14.2 1.5

Mag 2.8 0.3

Non Mag/Non Condo 83.0 8.8 0.1 0.71 0.81 14.6 28.8 25.7 4.4 3.1 95.6 96.9

Feed Calc. 100.0 10.6

35 x 65 MESH

Not Tabled

Condo 8.6 0.5

Mag 5.5 0.3

Non Mag/Non Condo 85.9 4.8 3.18 3.09 6.27 100.0 100.0 100.0 9.2 3.5 90.8 96.5

Feed Calc. 100.0 5.6

Rougher Lights

Condo 10.0 0.5

Mag 3.2 0.2

Non Mag/Non Condo 86.8 4.7 0.45 2.44 2.89 13.8 77.0 44.9 5.3 2.6 94.7 97.4

Feed Calc. 100.0 5.4

Cleaner Lights

Condo 13.0 0.7

Mag 4.8 0.3

Non Mag/Non Condo 82.2 4.4 0.24 1.73 1.97 6.8 50.7 28.5 4.9 2.8 95.1 97.2

Feed Calc. 100.0 5.3

CUMULATIVE

PRODUCTS

Total NMjNC from 64.7 100.0 100.0 100.0 4.6 2.6 95.4 97.4

Untabled Feed

Total NMjNC from 62.9 36.9 99.1 76.2 4.0 2.6 96.0 97.4

ROll. + Scavo

Lights 55.6 20.7 78.1 57.0 3.7 2.6 96.3 97.4

Total NMjNC from 54.9 11.3 58.9 41.4 3.5 2.5 96.5 97.5

Rou. Lights

6,092,665

TABLE lO.2-continued

Data from Electrostatic and Induced Roll Separations on Air Table Products

Feed Crushed to minus 6 mesh

Weight Percent _----'>"'2"'.3"--"-S."'G"'.,'-'I1"'0_ >2.3 S.G., Dist., %

Insoluble

Assay, % of

Soluble

Assay, % of

Product

Total NMjNC from

CI. Lights

Feed Sample Plus Minus Total Plus Minus Size Total <2.3 SG Total <2.3 SG

NOTE: The >2.3 sink products from the non mag., non condo were screened at intermediate mesh sizes to determine the

recoveries by particle size, i.e., the 6 x 10 m at 8 m, the 10 x 20 m at 14 m, the 20 x 35 m at 28 m, and the 35 x 65 mat

48 m.

EXAMPLE 11

This example illustrates beneficiation of trona using air

tabling, electrostatic separation and magnetic separation,

and demonstrates a relationship between breadth of size

fractions and effectiveness of air tabling as the density

separation method by comparison with heavy liquid separation.

A sample of bulk trona from Bed 17 of the Green River

Formation in Wyoming was crushed to -10 mesh. The

sample was subsequently sized into size fractions of 10 x20

mesh, 20x35 mesh and 35x65 mesh (Tyler mesh). Each of

the size fractions was then subjected to initial density

separation on an air table (Rougher Pass). The size fractions

were subsequently sent through a cleaner and for the lOx20

mesh fractions, a scavenger pass. The resulting separations

are shown in Table 11.1.

Each of the size fractions was then subsequently beneficiated

using electrostatic separation and magnetic separation.

The portions of material from each separation reporting

to various product streams are shown in Table 11.1.

The non-magnetic/non-conductive fractions were then

further analyzed by conducting a second density separation

based on heavy liquid separation to identify what portion of

impurities which are separable by density separation had not

been removed in the earlier air tabling step. The results of

this analysis are shown in Table 11.2. The column entitled

">2.3 S.G., %" identifies the total amount of material

separated from the beneficiated ore by the additional heavy

liquid density separation step. Additionally, that column

shows subcolumns titled "Plus" and "Minus." These two

subcolumns represent a breakdown of the "Total" percentage

of material which is greater than 2.3 S.G. which falls

into either the coarser or finer portion of the particular

stream. For example, the 10x20 mesh fraction was broken

down into a lOx14 mesh fraction and an 14x20 mesh

fraction. Thus, by comparing the "Plus" and "Minus" subcolumns

of the ">2.3 S.G., %," it can be seen that inefficiency

in the air tabling density separation tended to be at

smaller particle sizes within each size fraction because most

of the higher specific gravity material left by air tabling was

in the smaller particle size (the "Minus" column).

The columns titled "Insoluble Assay" and "Soluble

Assay" provide data on the portion of each stream which is

insoluble (i.e., impurity) before heavy liquid separation

("Total" subcolumn) and after heavy liquid separation

("<2.3 S.G." subcolumn). Thus, for example, the purity of

products resulting from beneficiating ore using air tabling

can be seen in the "Total" subcolumn of the "Soluble Assay"

column for each of the different streams. This purity can be

compared with the subsequent column, having a higher

purity, which identifies the purity of the beneficiated material

with the subsequent heavy liquid separation to indicate

a theoretical purity based on perfect density separation. In

addition, the improvement in trona purity between the

20 non-magnetic/non-conductive product which was not air

tabled and the non-magnetic/non-conductive product which

was air tabled can be seen by comparing the "Total NonMagnetic/

Non-Conductive from Untabled Feed" line with

the "Total Non-MagneticlNon-Conductive from Cleaner

25 Lights" line in the "Cumulative Products" section of Table

11.2.

TABLE 11.1

Data from Air Table Tests on Bulk Trona Sample Crushed to Minus 10

30 Mesh

Weight, % of

Product Feed Size Fraction Sample

35 10 x 20 MESH

Rougher Pass

Heavies 13.6 13.6 4.1

Lights 86.4 86.4 26.3

Feed Calc. 100.0 100.0 30.4

Scavenger Pass

Heavies 8.2 1.8 0.3

Lights 91.8 12.5 3.8

Feed Calc. 100.0 14.3 4.1

Cleaner Pass

Heavies 3.0 2.6 0.8

Lights 97.0 83.8 25.5

Feed Calc. 100.0 86.4 26.3

20 x 35 MESH

50 Rougher Pass

Heavies 1.3 1.3 0.3

Lights 98.7 98.7 20.1

Feed Calc. 100.0 100.0 20.4

Cleaner Pass

Heavies 4.4 4.3 0.9

Lights 95.6 94.4 19.2

Feed Calc. 100.0 98.7 20.1

35 x 65 MESH

Rougher Pass

Heavies 13.0 13.0 1.1

Lights 87.0 87.0 7.4

Feed Calc. 100.0 100.0 8.5

Cleaner Pass

65 Heavies 18.0 15.7 1.3

Lights 82.0 71.3 6.1

6,092,665

33 34

TABLE 1l.1-continued

Data from Air Table Tests on Bulk Trona Sample Crushed to Minus 10

Mesh

Product

Feed Calc.

MINUS 65 MESH (not air tabled)

TOTAL FEED CALC.

Weight. % of

Feed Size Fraction Sample

100.0 87.0 7.4

40.7

100.0

What is claimed is:

1. A process for recovering a saline mineral from an ore

containing the saline mineral and impurities, said process

comprising the steps of:

(a) calcining the ore to alter the apparent density of the

saline mineral; and

(b) separating a first portion of impurities, said impurities

having an apparent density different than that of the

saline mineral in the calcined ore, from the calcined ore

by density separation to produce a recovered saline

mineral.

2. A process, as claimed in claim 1, wherein the recovered

saline mineral comprises trona.

TABLE 11.2

Data from Electrostatic and Induced Roll Separations on Air Table Products

Feed Crushed to minus 10 mesh

Weight Percent _~>",2",.3"--"-S.",G,,.•,~'/1,,,o_ >2.3 S.G.. Dist.. %

Insoluble

Assay. % of

Soluble

Assay. % of

Product Feed Sample Plus Minus Total Plus Minus Size Total <2.3 SG Total <2.3 SG

10 x 20 MESH

Not Tabled

Condo

Mag

Non Mag/Non Condo

Feed Calc.

Rougher Lights

Condo

Mag

NonMag/NonCond.

Feed Calc.

Scavenger Lights

Condo

Mag

Non Mag/Non Condo

Feed Calc.

Cleaner Lights

Condo

Mag

Non Mag/Non Condo

Feed Calc.

24.7 7.5

1.6 0.5

73.7 22.4 0.59 1.19 1.78 100.0 100.0 100.0 4.0 2.6 96.0 97.4

100.0 30.4

16.6 4.4

3.6 0.9

79.8 21.0 0.06 0.7 0.76 9.5 55.1 40.0 2.7 2.4 97.3 97.6

100.0 26.3

23.1 0.9

3.7 0.1

73.1 2.8 0.51 3.05 3.56 10.7 31.8 24.8 6.5 2.3 93.5 97.7

100.0 3.8

23.1 5.9

3.7 1.0

73.1 18.6 0.02 0.63 0.65 2.8 44.1 30.4 2.5 2.3 97.5 97.7

100.0 25.5

3. A process, as claimed in claim 1, wherein the first

portion of impurities comprises halite.

4. A process, as claimed in claim 1, wherein the apparent

density of the first portion of impurities is greater than that

50 of the saline mineral.

5. A process, as claimed in claim 1, further comprising the

step of separating a second portion of impurities by magnetic

separation.

6. A process, as claimed in claim 5, wherein said magnetic

55 separation step occurs after said density separation step.

7. A process, as claimed in claim 5, wherein the second

portion of impurities is more magnetic than the saline

mineral.

8. A process, as claimed in claim 7, wherein the second

portion of impurities comprise minerals selected from the

60 group consisting of shale, complex iron silicates or ironbearing

carbonates.

9. A process, as claimed in claim 1, wherein the purity of

the recovered saline mineral is at least about 95% after said

separating step.

10. A process, as claimed in claim 9, wherein the purity

of the recovered saline mineral is at least about 98% after

said separating step.

EXAMPLE 12

This example illustrates beneficiation of trona using air

tabling, calcination, additional air tabling, and magnetic

separation in accordance with the second aspect of the

present invention.

A 25 kilogram sample of 8xlO mesh trona from air

tabling, having a purity of about 86.5%, was calcined at 3000

F. for 3 hours and subsequently subjected to additional air

tabling. The additional air tabling rejected impurities which

could not be separated by air tabling prior to calcination. The

purity of the trona increased from 86.5% to 93.1% after one

cleaning step of air tabling. Additional magnetic separation

increased the grade to 97.8%.

EXAMPLE 13

This example illustrates the effectiveness of the second

aspect of the present invention in removing halite from

trona. A sample of calcined trona was mixed with halite to

achieve a mixture comprising about 10% halite. Air tabling

of this mixture resulted in a sharp separation yielding a 65

virtually pure halite fraction and a calcined trona product

containing less than 1% halite.

6,092,665

* * * * *

(i) combusting an energy source to produce heat and

combustion gas;

(ii) transferring at least a portion of the heat to the fluid;

(iii) directing at least a portion of the combustion gas

through a combustion gas outlet which is not in direct

fluid communication with said calcining vessel.

26. A process, as claimed in claim 25, wherein said step

of heating the saline mineral produces calcining gas, and

wherein said process further comprises the steps of:

(d) removing the calcining gas from the calcining vessel

through a calcining gas outlet; and

(e) combining at least a portion of the calcining gas with

at least a portion of the combustion gas.

27. A process, as claimed in claim 22, wherein particulates

15 are removed from the calcining gas during said condensing

step.

28. A process, as claimed in claim 22, wherein said step

of condensing at least a portion of the water comprises the

step of condensing water by cooling the calcining gas.

29. A process, as claimed in claim 28, further comprising

the step of:

(d) cooling the condensed water, wherein said condensing

step comprises bringing the cooled water into thermal

communication with the calcining gas.

30. A process, as claimed in claim 22, wherein said

condensing step comprises reducing the water content of the

calcining gas to less than about 50%.

31. A process, as claimed in claim 22, wherein said

condensing step comprises reducing the volume of the

30 calcining gas by at least about 50%.

32. A process, as claimed in claim 27, wherein said

condensing step reduces the particulate content by at least

about 50%.

33. A process for recovering a saline mineral from an ore

35 containing the saline mineral and impurities, said process

comprising the steps of:

(a) sizing the ore to generate a first fraction of about -65

mesh and a second fraction of about +65 mesh; and

(b) separating iron from the first fraction to produce a first

recovered portion comprising a recovered saline mineral.

34. A process, as claimed in claim 33, wherein said

separating step comprises a wet separation process.

45 35. A process, as claimed in claim 34, wherein said wet

separation process comprises the slush process.

36. A process, as claimed in claim 33, further comprising:

second fraction to produce a second recovered portion;

and

(d) combining the first recovered portion with the second

recovered portion to produce a recovered saline mineral.

37. A process, as claimed in claim 33, further comprising,

55 before step (a), the step of reducing a particle size of said ore

before said separating steps.

38. A process, as claimed in claim 37, wherein said

reducing step reduces to particle size of said ore to less than

about 6 mesh.

11. A process, as claimed in claim 1, further comprising,

before step (b), the step of reducing a particle size of the ore.

12. A process, as claimed in claim 1, further comprising,

before step (b), the step of de-dusting the ore to recover

fines.

13. A process, as claimed in claim 1, further comprising,

before step (b), the step of sizing the ore into between 3 and

10 size fractions.

14. A process, as claimed in claim 1, wherein a maximum

particle size before said separating step is about 6 mesh.

15. A process, as claimed in claim 1, wherein a minimum

particle size before said separating step is about 100 mesh.

16. A process, as claimed in claim 1, wherein said

calcining step comprises heating the ore to a temperature of

at least about 120° C.

17. A process, as claimed in claim 16, wherein said

heating step occurs in a fluidized bed reactor.

18. A process, as claimed in claim 1, wherein said density

separation step comprises a process selected from the group

consisting of air tabling and dry jigging.

19. A process, as claimed in claim 18, wherein said

density separation step comprises air tabling.

20. A process, as claimed in claim 1, wherein said

calcining step comprises the step of heating the saline

mineral in a calcining vessel above its calcining temperature 25

with a heat source to calcine the saline mineral, wherein said

heat source is not in direct fluid communication with said

saline mineral.

21. A process for recovering trona from an ore containing

trona and impurities, said process comprising the steps of:

(a) reducing a particle size of the ore to a size to achieve

liberation of impurities;

(b) sizing the ore into between 3 and 10 size fractions;

(d) separating impurities comprising halite from a fraction

of the calcined ore by a density separation method, the

impurities having a higher apparent density than calcined

trona.

22. A process for calcining a saline mineral, said process 40

comprising the steps of:

(a) heating the saline mineral in a calcining vessel above

its calcining temperature with a heat source to calcine

the saline mineral, wherein said heat source is not in

direct fluid communication with said saline mineral and

wherein said step of heating the saline mineral produces

calcining gas having water vapor;

(b) removing the calcining gas from the calcining vessel

through a calcining gas outlet; and

calcining gas.

23. A process, as claimed in claim 22, wherein the saline

mineral comprises trona.

24. A process, as claimed in claim 23, wherein said step

of heating comprises the steps of:

(i) heating a fluid; and

(ii) bringing the heated fluid into thermal communication

with the calcining vessel.

25. A process, as claimed in claim 24, wherein said step

of heating a fluid comprises the steps of: