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Патент USA US3096044

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July 2, 1963
A
K. SCHMIDLAPP
3,096,034
METHOD AND APPARATUS FOR PURIFYING POTASSIUM
SALT-CONTAINING MATERIALS
Filed Dec. 28, 1960
INVEN TOR.
IWSQW‘L»
WW1
United States Patent 0 an» ce
sagas-354
Patented July 2, 1963
1
2
3,096,034
ers, whereby large quantities of waste Waters are pro
duced which it is sometimes di?icult to dispose of. Vari
ous other modi?cations of dry and wet clay separation
Kurt Schmidlapp, Neuhof, Kreis Fuld'a, Germany, as
signor to Wintershall Aktiengesellschaft, Kassel, Ger
have been proposed all of which, however, are quite in
volved, and uneconomical, and at best only of limited
METHOD AND APPARATUS FOR PURIFYING
POTASSIUM SALT-CONTAINING MATE
many
Filed Dec. 28, 1960, Ser. No. 79,073
16 Claims. (Cl. 241-14)
effectiveness. Thus, frequently one has to resort to the
old method of manually separating the larger clay par
ticles from the crushed raw material and to’ attempt in this
manner to keep during subsequent working up of the
The present invention relates to the working up of po 10 potassium salts the content of clay constituents at a
tassium salts-containing raw material and particularly
manageable low level. It may be noted that in order
to the separation of sludge~forming clay constituents from
to be effective, the separation of clay or sludge-forming
the crude potassium salts or potassium salts containing
constituents should be carried out to such an extent that
raw materials so as to facilitate the further processing of
no more than 1.5% by weight, and preferably less, of
15 the sludge-forming constituents remain in the potassium
the material.
Natural potassium salt deposits contain clay-like and
salt-containing fraction.
other water insoluble accompanying materials all of which
will be referred to herein as clay constituents. These
It is therefore an object of the present invention to
overcome the above-discussed di?iculties in the separation
water insoluble and sludge-forming clay constituents
of sludge-forming constituents from the main body of
cause great difficulties in the working up of the potassium 20 potassium salts-containing raw materials.
salts, for instance by ?otation processes. Clay constituents
It is another object of the present invention to provide
of sylvitic hard salt deposits may amount to about 2%
a simple and economical method for the effective separa
of the weight thereof and the amount of clay constituents
tion of sludge-forming constituents such as clay from
in other sylvitic raw materials may exceed 10%.
the potassium salts-containing portion of raw materials,
These sludge-forming impurities cause considerable 25 for instance sylvitic minerals. Other objects and advan
di?iculties during formation of hot potassium salt solu
tages of the present invention Will become apparent from
tions. The hot solution is contaminated with ?nely sub
a further reading of the description and of the appended
divided sludge-forming insoluble particles which tend to
claims.
remain in suspension and frequently can be caused to
With the above and other objects in view, the present
thicken and to form a sediment only with the assistance 30 invention contemplates in a method of separating sludge
of auxiliary precipitating agents.
Nevertheless, fre
quently it is extremely di?icult to free the hot solution
from sludge particles remaining in suspension and this
will result upon cooling of the hot potassium solution in
the recovery of ?nely granulated low-purity end products.
In addition, even when it is possible adequately to
separate the sludge from the major portion of the hot
forming constituents from crude potassium salt containing
the same, the steps of subjecting the sludge-forming con
stituents containing crude potassium salt to a series of
successive impact comminutions at varying impact velo
cities, with the impact velocity of the ?rst and last impact
comminution steps being smaller than the impact velocity
of the intermediate impact comminution.
solution further diiiiculties arise in the separation of the
Surprisingly, it has been found that according to the
sludge cake from the adhering residual salt solution. The
present invention the content of sludge-forming constit
sludge may contain bentonite and may display thixotropic
uents of the crude potassium salt containing material
tendencies. Thus, potassium containing solution will be
can be reduced down to about 1.5% or even lower
bound by the sludge cake and losses of potassium will be
by continuously passing the raw material through a series
incurred due to the unsatisfactory separation of solution
of successively arranged impact comminutors operating
from the sludge cake.
45 at predetermined rotational speeds, whereby the material
Separation by ?otation is also unfavorably in?uenced
is sifted or screened while passing from one impact com
by sludge-forming constituents of the raw material, since
minutor to the next. It has been found that in each of
sludge particles will be retained in the concentrate frac
these impact comminutions the material will be broken
tions and will reduce the purity thereof. Furthermore,
down into clay or the like particles of relatively large size
the ?nely subdivided sludge particles impair the effective 50 and potassium salt-containing particles of relatively
ness of ?otation improving agents. In addition, the pres
ence of the ?nely subdivided sludge particles will stabilize
and prevent easy destruction of the foam formed on the
liquid leaving the ?otation process. Thus, an excess of
smaller size so that- the clay particles can be separated
from the potassium salt containing particles by screening
prior to subjecting the thus separated larger clay-contain
sludge-forming particles will not only render the ?otation
process uneconomical but, in fact, will make it impossible
ing particles to the next impact comminution.
The present invention requires certain relationships be
to carry out such process.
In order to overcome the above-described and very
tween the rotational speeds of the individual impact com
minutors through which the material passes. The rota
tional speed increases from the ?rst to the second step and
serious di?'iculties in the recovery of potassium salts from
raw materials including sludge-forming constituents, at 60 is then reduced again in subsequent impact comminution
tempts have been made to separate the sludge-forming
steps, as will be more ‘fully described below.
constituents of the raw material from the potassium con
By comminuting the raw material in a hammer mill, it
taining remainder thereof prior to ?otation or hot dissolu
will not be possible to form the fractions of considerably
tion of the potassium containing fraction. Thus, it has
increased or reduced clay content. For instance, by sub
been attempted to separate coarse clay particles by hand 65 jecting the crude potassium salt containing 2.5% insoluble
from the crushed raw material.
According to a rather
expensive method, the dry comminuted material is sub
jected to electrostatic separation. The wet methods of
clay separation are modi?ed ?otation processes with sludge
thickening devices such as counter current wash-thicken 70
constituents to comminution in a conventional hammer
mill having a rotational speed of 29 meters per second at
its peripheral beater portion, the material may be com
minuted into particles of varying sizes ranging up to 4 mm.
Upon sepmation of the thus comminuted material into
...~.
.
3,096,034
.
4
various size ranges, the following percentage of clay was
tain on the one hand clay particles which contain only a
very small percentage of potassium salt and on the other
found in the respective particle sizes:
hand potassium salt enriched particles which contain
only very little clay.
TABLE I
Particle size, mm.:
clziiiivliéigiftent
-It is important to note that, as shown in Table IlA, when
impact comminution for instance with the Andreas im
075-1
_
11-73
pact breaker shown in U.S. Patent No. 2,889,119 is carried
0.6-0.75
12-24
out at considerably higher impact velocities for instance
0.54m
10-91
at a circumferential velocity of the impact comminutor
0.4-0.5
_
9-46
10 of 60 meters per second, that under such conditions maxi~
0.3-0.4
_
12.67
mum concentration will be shifted to a relatively smaller
0.2-0.3
8-44
particle size such as between 0.4 and 0.75 mm. so that it
o.1_o.2
___
10.19
is not possible thereafter to separate the clay enriched
O.6—0.1 _
10.99
particles from the remainder in an economical manner.
0.06
___ 12.27
It is therefore important according to the present inven
tion to so adjust the circumferential speed or velocity of
Obviously, the above-described process is not suitable
the
impact comminutor that with reducing particle size
for effectively reducing the clay content of the crude
of the material which is fed into the impact comminutor
potassium salt. In contrast thereto sequentially arranged
the further comminution will still result in larger particles
impact comminutors, preferably at least 3, and most
preferably 4, impact comminutors with sifting of the 20 of increased clay content and smaller particles of reduced
1-4
5
-
clay content. For instance, the impact velocity during the
second comminution may begreater than during the ?rst
comminution, while in subsequent comminution steps
material while it passes from one impact comminutor to
the next and with a de?nite relationship between the rota
tional speeds of the individual impact comminutors, will
the impact velocity may again be reduced in order to
achieve the desired result.
result in a selective breakdown of the material into larger
predominantly clay containing particles and smaller potas—
sium salt enriched particles.
Thus, according to the present invention, it is possible
TABLE IIA
Impact velocity, m./sec.:
to comminute the raw material for instance to a‘ maximum
particle size of 4 mm. while at the same time carrying out
Percent1
15
an effective clay separation with small, economically 30
feasible loss of potassium salt. The process of the present
88
25
_
30
___
invention will result in a product containing not more than
40
about 1.5% and preferably only about 1.2% of insoluble
constituents, which product is eminently suitable for
further puri?cation by ?otation or the like.
Surprisingly, it has been found that the somewhat plastic
60 ___
_
70
38
___
__
3
0.5
1‘Percent clay content of larger particles (greater than
3 mm.).
The dependency of the loss of potassium salt on the
clay constituents will offer more resistance to comminu
tion in an impact comminutor than the potassium salt
constituents of the raw material. This is particularly
impact velocity is shown in Table HI with one raw ma
terial, by way of example:
'
TABLE III
40
so when the impact velocity is relatively low. Thus, it is
Impact veloctiy, m./sec.:
possible to separate the sludge-forming clay constituents
K20 percent1
to a considerable extent in dry form fromthe more brittle
15
0.85
salt and to enrich the clay content of certain particle sizes
while the clay content of other particle sizes is reduced.
For instance, by subjecting a raw material having a 45
maximum particle size of 40 mm. and containing 2.5%
20
_ 0.61
35'
_________ __ 0.35
insolubles to impact comminution in an'impact breaker
40
______ ._ 0.29
25
30
_______ __ 0.51
____
‘_ 0.43
such as disclosed in US. Patent 2,889,119 to Andreas, at
1 Percent lost with clay enriched fraction.
an impact velocity of 24 m./sec., it will be found that the
For best separation of the raw material used according
clay content of the various size fractions will be as 50
to Table III, the selective comminution of the same and
follows:
separation of the clay constituents from the residue will
TABLE 11
be carried out in four impact comminution steps at impact
Clay in percent
Particle size, mm.:
by weight
velocities as indicated in Table IV:
Up to 4
20.52
TABLE IV.
1-4
39.34
0.75-1
0.5——0.6
_____.
10.50
_____________________________ __
_
6.70
0.4-0.5
___
_
___-..
0.3-0.4
___
0.2-0.3
___---
0.l-—0.2
0.06—0.1
0.06
5.13'
2.19
___-
___
Preferred
1n./sec.
6.28
___
____._
_
Impact
velocity
mJsec
7.13
_
1.31
________________________________ __
0.90
100.00
Thus, it can be seen that the clay content of the larger
particles will increase while the smaller particles will show
a reduced content of sludge-forming clay constituents.
'If the mixture resulting from such impact comminution
is now classi?ed by size, for instance by screening, it will
be possible to separate the larger particles of increased
clay‘ content from the smaller particles of reduced clay
content. By repeating this process at suitably arranged
60
First impact comminution __________________ __
17-27
18—'22
Second impact comminution_____
26-38
30-36
Third impact comminution ____ __
Fourth impact comminution ________________ __
20-30
20-30
22-26
22-26
Considering the upper limit of the preferred range of
impact velocity for the ?rst impact comminution and the
lower limit of the preferred range of impact velocity for
the second impact comminution, it will be apparent that
preferably the impact velocity of the second impact com
70 minution will be at least about 35% greater than the im
pact velocity during the ?rst impact comminution.
Most of the clay will be found in the coarse fractions of
0.5 mm. or larger particle size and it is possible in this
manner to remove without di?iculty for instance up to
impact comminution velocities, it will ‘be possible to ob 75 60% of the initial clay content of the raw material,
3,096,034
5
6
This surprising result can be further improved by spray
ing or wetting with ?nely subdivided polar or non-polar
liquids, for instance water or salt solutions, or by treating
minal portion. However, screening and wetting may also
be carried out in separate devices, by passing the particles
after screening over a vibrating table or the like and to
spray or steam the material while it is intensively moved
during passage across the vibrating table. It is desirable
the material for a short period of time with warm air of
100% relative humidity. As polar liquids, aliphatic and
aromatic alcohols, esters, ketones, ether and mixtures
to closely control the amount of liquid which is imparted
to the material and this is more easily accomplished by
thereof may be used, and as non-polar liquids, for instance
non-polar liquid hydrocarbons, such as benzene, or car
bon tetrachloride. Apparently, by such treatment a sur
steaming.
without appreciable softening of the clay and in this man
ner the plastic qualities of the clay are increased compared
with the potassium salt-containing mineral constituent
potassium salt enriched smaller particles of the individual
which remains brittle.
essing.
After completion of the last impact comminution step,
face impregnation of the clay constituents takes place 10 preferably the fourth impact comminution, the clay en
riched fraction is withdrawn from the process while the
impact comminution steps are collected ‘for further proc
Consequently, upon subjecting
the thus wetted raw material to impact comminution there
>
Comparison experiments which vwere carried out with
the same raw material by hand separation and by selec
tive impact comminution according to the present in
will be an even more eifective separation into somewhat
plastic clay particles and brittle potassium salt enriched
particles.
vention at the rate of 250 tons per hour gave the results
It was then found that lesser quantities of liquid will be
shown in Table VI:
needed for the above purpose when the liquid is applied 20
TABLE VI
in vapor form than when liquid is sprayed directly on to
the material.
Clay separation by—
Table V illustrates a result obtained by application of
0.3% Water in the form of a spray or in the form of satu
rated steam:
TABLE V
Particle size, mm.
Untreated,
percent
insoluble
66. 6
10. 6
5. 6
4. O
3. 0
4. 2
68. 5
10.3
6. 1
2. 9
2. 9
4. 5
insoluble
‘
Separated clay mineral, t/h ________________ __
Sprayed with Steamed with
3% water,
saturated
percent
steam, percent
insoluble
Manual
Selective
separation impact corn~
25
3
3.15
13. 1
16. 14
34. 1
45
percent insoluble ________________________ __
1. 2
0.91
K20 loss in separated clay, percent ________ __
0.29
0.33
Insolubles in clay mineral, percent-..
Clay removal (on clay mineral), perce
30
82. 4
6. 1
3.8
1. 9
1. 5
2. 0
minution 1
Residual clay in potassium salt fraction,
1 According to the present invention.
As shown above, the fully automatic selective impact
comminuation according to the present invention will
6. 0
4. 8
2. 8
achieve a lesser residual clay content in the crude potas
sium salt than can be achieved by manual separation,
while, for all practical purposes, the loss of K20 in the
Table V shows the remarkably favorable clay enrich
ment in the coarse fraction of the Wetted clay containing
clay fraction is the same in both cases. Furthermore, and
this is most important, manual separation of 250 tons per
potassium salt mineral and the better separation accom
plished in this manner. It is interesting to note that the
hour requires about 35 IWOI‘KCI'S which, of course, are not
needed by proceeding in accordance with the present in
clay content of the coarse fraction of above 3 mm. will
vention.
increase only by 1.9% upon spraying with water, how
The effect of the present invention on subsequent salt
ever, by steaming the increase will amount to 15.8%.
Spraying took ?ve minutes while steaming was completed 45 ?otation is shown in Table V-II which clearly indicates a
better K20 yield at higher concentration and with lesser
in three seconds, which, of course, further increases the
advantages of steaming over spraying.
requirements of ?otation agents than by manual separa
It is also possible and sometimes advantageous to carry
out the ?rst surface treatment, be it by steaming or spray
tion of clay constituents:
ing, below ground for instance during tilting and empty
ing of the miner’s Wagon, whereby this thus introduced
moisture will bind simultaneously undesirable dust.
50
.
TABLE VII
Method of clay separation
Amount of
?otation
agent, g./t.
Of course, the wetting must not be carried out beyond
the introduction of a certain upper percentage of mois
ture. This maximum percentage is in the neighborhood 55 No separation crude salt containing
of about 0.5% of the weight of the treated material, above
1.85% Water insolubles correspond
which the plasticity of the clay is increased beyond desir
ing to 2.5% clay substance ________ __
A further increase in the selective separation effect can
be accomplished by the incorporation of a polar Wetting
Yield,
percent
K20
75
57. 3
S4. 6
40
58. 3
90. 2
32
59. 0
91. 6
Manual separation crude salt con
taining 1.31% water insolubles cor
able limits and makes it di?icult to separate the same from
the potassium salt increased fraction during the subse
quent screening process.
Concentration,
percent
K20
responding to 1.6% clay substance-
60
Repeated impact comminution (four
times) crude salt containing 0.84%
water insolubles corresponding to
0.9% clay substance _______________ __
agent, for instance a fatty acid amine in the aqueous wet
The clay enriched residue of the ‘last impact comminu
After the ?rst impact comminution step, the'oversize 65 tion is removed and may be used for instance as back
?lling. However, at least a portion thereof may also be
clay enriched particles will be retained on the screen while
used for granulating potassium salts. In the latter case
the smaller particles of reduced clay content will pass
separation of the clay constituents may be carried out
through the same. After subsequent impact comminu
selectively by varying ‘the rotational speed of the impact
tion, screening is carried out in similar manner, whereby
the clay enriched over?ow particles are Wetted by spray
comminutors, since in this case it is not necessary to con
ing or steaming in order to increase the selectivity of the
trol and carefully limit the K20 losses in the clay fraction
subsequent impact comminution step.
which subsequently is used for granulating potassium
It has been found to be advantageous to insert at the
salts.
terminal portion of the sieve or screen a blind bottom to
If the clay enriched residue of the process of the pres
ting liquid.
carry out wetting while the material passes over this ter 75 ent invention is to be further processed into a fertilizer,
3,096,084
8
together with other constituents, then the clay fraction
devices, i.e., the number of wetting devices and the loca:
may be further comminuted by additional impact com
minution of the same at higher rotational speeds, prefer
ably between 25 and 70 meters per second, whereby it is
advantageous during such further comminution of the
clay fraction to heat the impact comminutor with hot air,
Further processing may be carried out for instance in ac
tion of the same, depends to some extent on the particu
lar raw material and on the degree of comminution
cordance with the method described in German Patent
No. 1,022,241.
achieved in the individual impact comminutors. '
'
Screen 19 is provided with two screening surfaces so
that the material reaching screen 19 from'impact com
minutor 18 will be divided into three fractions of which
the ?nes will pass via chute 25 to elevator 32, while
the intermediate fraction may optionally pass via chute
The impact comminution of the raw material or of the 10 28 to elevator 32 or via chute 27 to the last impact com
minutor 20. The coarse fraction, i.e., the over?ow from
the upper screen 19, will then pass via chute 26 to im
pact comminution is carried out in an impact crusher or
pact comminutor '20.
a
breaker per se known in the art, one type of such impact
The material which reaches impact comminutor 2G is
breaker is for instance describedrin US. Patent No.
15 high in clay content and includes only a very small, por
2,889,119 to Andreas.
'
>
tion of the original potassium salt. Thus, the material
The novel features which are considered as character
which is passed through comminutor 20 serves no longer
istic for the invention are set forth in particular in the
for the recovery of potassium salt therefrom. It is fur
appended claims. The invention itself, however both as
larger particle, fraction resulting from the preceding im
ther comminuted in comminutor 29,’ preferably until at
to its construction and its method of’ operation, together
with additional objects and advantages thereof, will be 20 least 85% of the material reaches a ?neness of 1.5 mm.
or below and during comminution in impact comminutor
best understood from the following description of speci?c
20, hot air is introduced via blower 30 and conduit 31,
embodiments when read in connection with the accom
paying drawing, in which the FIGURE shows a schematic
illustration of a preferred arrangement according to the
present invention.
Referring now to'the drawing, it is schematically shown
that the broken raw material as mined is conveyed under
ground in haulage vehicles 1 to conveyor 3 and passes
since the residual moisture of the material wouldother
wise prevent ?ne crushing of the same.
.
T
It is thus apparent that the relationship between the
rotational speeds, i.e., theimpact velocities to which the
material is exposed in the series of impact comminutors,
is ‘of major importance in order to achieve the nearly
from conveyor 3 through crusher 4 into underground
complete separation of potassium salt from the sludge
hopper 5. The ?rst wetting of the raw material is pref 30
forming insoluble or clay constituents of the raw ma
erably carried out during passage of the raw material from
terial. The process of the present invention is generally
haulage vehicles 1 to crusher 4, for instance by means of
a spraying device associated with conveyor 3. The
crushed wetted and well mixed raw material is stored in
hopper 5 and hauled from there above ground by means
of haulage device 6.
.
The material now enters the crude salt comminution
carried out at ambient temperatures.
It has been found that best results according to the
present invention are achieved by arranging, for separa
tion of clay and salt between three and four impact com
minutors, preferably the four impact comminutors indi
installation and passes over screen '7 for separation into
cated in the drawing reference numerals 8, 12, 161and 18,
?nes and into material of above about 4 mm. particle
so that the rotational speed of the second impact com
size. The thus separated ?nes, as well. as the subse 40 minutor is higher than the rotational speed of the ?rst
quently separated ?nes fractions are collected on elevator
impact comminutor, and the rotational speed of the third ‘
V 32.
The over?ow from screen 7 is comminuted in ?rst
impact comminutor 8 at relatively low circumferential
speed. The crushed material leaving impact comminutor
and fourth impact comminutors is lower than the rota?
tional speed (or impact velocity) of the second impact
comminutor. .At least two impact comminutors must be
8 passes over screen 9 where it is separated in ?nes which 45 used according to the present invention, in which case
reach elevator 32 via chute 22, and into coarse material
(the over?ow of screen 9) which passes to and is wetted '
the rotational speed of the second impact comminutor
will be greater than that of the ?rst impact comminutor
on vibrating table 10. Wetting‘ may be carried out by
and, for all practical‘purposes, the maximum number of
spraying or steaming as described further above. The
impact
comminutors for sequential comminution of the
50
wetted material is then introduced into the next or sec
raw material with separation into coarse clay enriched
ond impact comminutor 12 and here again broken into a
particles and smaller potassium salt enriched particles,
_ fraction of ?nes, consisting essentially of potassium salt
will not exceed eight.
and into a coarse fraction of enriched clay or insolubles
content. From impact comminutor 12, the material
Wetting agents which may be advantageously sprayed
‘passes to screen 13, the ?nes are separated and reach 55 or steamed on to the material include saturated steam
elevator 32 via chute 23, and the coarse fraction passes
under relatively low over pressure, or aqueous salt solu
to vibrating table 14 and is again wetted, for instance by
tions containing, for instance, between 150 and 250 grams
The thus wetted'ma
per liter of magnesium chloride, or, the so-called hard’v
'terial passes to the third impact comminutor 16. Here
salt solution which accrues in the potassium salt recovery
again, the material is broken down into ?nes and a coarse 60 and which contains about 80! grams per liter of potassium
,means such as a nozzle device 15.
fraction and the ?nes are screened out on screen 17 and
‘guided to elevator 32 via chute 24. It is essential ac
I cording to the present invention that the circumferential
chloride, 100 grams per liter of sodium chloride, 1507'
grams per liter of magnesium chloride and 50 grams per ,
liter of magnesium sulfate may also be advantageously
comminutor of the series starting with impact comminu 65 used for wetting the material; prior to. further impact
comminution.
tor 8, is higher than the circumferential velocity of im
The following example'is given as illustrative only of
pact ,comminutor 8, while the circumferential speed of
the present invention howeven'without limiting the same
the third impact comminutor 16 preferably is less than
to the speci?c details of the example.
that of impact comminutor 12. The coarse fraction of
the broken mixture produced in impact comminutor V16, 70
velocity of impact comminutor 12, i.e., the ‘second impact
i.e., the over?ow of screen 17, is then introduced into the
fourth. impact 'comminutor @18 and passes ‘from there to
screen 19.
Contrary to screens 10 and 14, screen 19
is not‘coordinated with a wetting device.
However, it
may be noted that the speci?c arrangement of wetting
Example
The material as mined is broken and wetted and
thenv
conveyed to screen 7.7 250 tons per hour of such’ ma~
terial containing 1.4% insoluble which equals 1.80% clay
3,096,034
10
0
mineral are thus introduced.
Without further analysis, the vforegoing will so fully
This material has the fol
lowing particle sizes:
reveal the gist of the present invention that others can
by applying current knowledge readily adapt it for various
applications without omitting features that, from the stand
point of prior art, fairly constitute essential character
TABLE VIII
Percent
40-160 mm
18.1
4—40
14
0.6—1
0.3-0.6
24.7
15.8
11.4
15.0
0.2-0.3
istics of the generic or speci?c aspects of this invention
and, therefore, such adaptations should and are intended
to be comprehended within the meaning and range of
equivalence of the following claims.
4.2 10
11-0-3
_____
10.8
What is claimed as new and desired to be secured
by Letters Patent is:
1. In a method of separating sludge-forming clay con
stituents from a particulate sludge-forming clay and potas
sium salt containing mined raw material, the steps of
100.0
About 150 tons per hour of the material pass through
screen 7 and are removed by conveyor 21. These 150 15 subjecting particulate sludge-forming clay and potassium
salt-containing mined raw material including also par
tons per hour have a particle size of less than 4 mm. 100
ticles
within the size range of between 40 and 160 mm.
tons per hour with a particle size which is generally at
without prior impact comminution to impact comminu
least 4 mm. and contains only very little of smaller par
tion at a ?rst predetermined impact velocity so as to sepa
ticles pass then into impact comminutor 8 and are there
‘rate said raw material into clay enriched larger particles
20
in selectively broken down under conditions such that
and potassium salt enriched smaller particles; recovering
substantially no clay agglomerations are formed. The
said potassium salt enriched particles from the thus
material from comminutor 8 passes on to screen 9 where
formed particulate mixture; subjecting said clay enriched
again the portion having a particle size of less than 4
larger particles to impact comminution at a second veloc
mm. is passing through the screen and is removed by
conveyor 22. The material which does not pass through 25 ity being greater than said ?rst impact velocity so as to
separate said clay enriched particles into further potas
sium salt enriched smaller particles and larger clay en
riched particles; recovering said further potassium salt
enriched particles; and subjecting the thus separated clay
screen 9 is then wetted as previously described in connec
tion with the drawing. This process is repeated several
times for instance as illustrated in the drawing, where
by the degree of separation on each screen depends of
course on the mesh Width thereof.
enriched particles to impact comminution at a third im
The ?ner the mesh 30
pact velocity being smaller than said second impact veloc
width, the purer is the potassium salt material which
is separated, however, the ‘greater is the amount of potas
sium which remains with the coarse over?ow.
ity so as to cause further separation into clay enriched
larger particles and smaller potassium salt containing par
ticles of greatly reduced clay content.
Conse
quently, when the potassium containing over?ow can
2. In a method of separating sludge-forming clay con
be utilized for other purposes, then it is generally de
stituents from a particulate sludge-forming clay and potas
sium salt containing mined raw material, the steps of
sirable to use a screen of lesser mesh width in order to
obtain a ?ne product of higher purity. However, when
it is desirable to obtain the largest possible yield calcu
lated as potassium oxide in the ?ne product then, of
course, a somewhat wider mesh will be used for the screen
subjecting particulate sludge-forming clay and potassium
salt-containing mined raw material including also particles
40 within the size range of between 40 and 160 mm. with
out prior impact comminution to impact comminution at
a ?rst predetermined impact velocity of between 17 and
ing of the respective comminuted material. In any event,
the clay concentration in the coarse material which does
not pass through the respective screens will be enriched
27 m./sec. so as to separate said raw material into clay
enriched larger particles and potassium salt enriched
so that for instance if the material which reaches screen 7
smaller particles; recovering said potassium salt enriched
contains 1.8% of clay mineral, then the coarse material 45
particles from the thus formed particulate mixture; sub
or over?ow from screen 7 will show a clay concentration
jecting said larger clay enriched particles to impact com
of 3.6%, the over?ow from screen 9 a clay concentra
minution at a second impact velocity of between 26 and
tion of 7.6%, the over?ow from screen 13 a clay con
38 m./sec. being greater than said ?rst impact velocity
centration of 20.5%, the over?ow from screen 17 a
so as to separate said clay enriched particles into further
clay concentration of 35% and the over?ow from screen
potassium salt ‘enriched smaller particles and larger clay
19, i.e., the two over?ows which are indicated by refer
enriched particles; separating said further enriched par
ence numerals 26 and 27 will show a clay concentration
ticles; subjecting said clay enriched particles to impact
of 58.0% while over?ow 26 taken ‘alone will have a clay
comminution at a third impact velocity of between 20
concentration of 63.0%. Under the given conditions,
about 1.7 tons per hour of comminuted potassium ?ne 55 and 30 m./sec. being smaller than said second impact
velocity so as to cause further separation into clay en
salt will pass through double screen 19- to conveyor 25.
The separated clay is contained in the over?ows 26 and
27, whereby over?ow ‘27 may be added to the crude salt
and reintroduced into the screening process if desired.
Under the given conditions, for instance 3.5 tons per 60
hour of clay enriched material will accrue in over?ows
26 and 27. The analysis of the combined over?ows 26
and 27 show about 34.1% insoluble substances which cor
respond to about 58% of clay substance.
riched larger particles and smaller potassium salt con
taining particles of greatly reduced clay content, and re
covering the thus formed potassium salt containing par
ticles of greatly reduced clay content.
3. ‘In a method of separating sludge-forming clay
constituents from a particulate mined raw material con
taining a potassium salt and sludge-forming clay con
stituents, the steps of subjecting particulate sludge-forming
clay and potassium salt-containing mined raw material in
Table IX gives the screen analysis of the coarse over 65
cluding also particles in the size range of between 40 and
?°W 26TABLE IX
Percent
160 mm. without prior impact comminution to impact
4 mm.
___
73.8
comminution at a ?rst predetermined impact velocity so as
3-4 _____________________________________ __
22.1
to form of said raw material a mixture of clay enriched
1-3
1-1.5
O.5—1
O—0.5
__-_
_______ __
2.5
70 larger particles and potassium salt enriched smaller par
____ __
0.6
ticles; screening the thus-formed mixture so as to sepa
rate the same into said smaller and larger particles; sub
____ __
___________________________________ __
0.6
0.4
jecting the thus separated clay enriched larger particles to
impact comminution at a second velocity being greater
100.0
than said ?rst impact velocity so as to form a second mix
3,096,034
ll
12
ture of clay enriched larger particles and of potassium salt
enriched smaller particles; screening the thus formed
type which has a rotor which throws material against an
impact member of the crusher, said ?rst impact crusher
second mixture so as to separate the same into said last
including means for rotating said rotor thereof at a pre
formed smaller and larger particles; subjecting the thus
determined speed for crushing said particulate raw ma
terial into a relatively coarse clay enriched fraction and
' last formed separated clay enriched larger particles to im- '
pact comminution at a third impact velocity being smaller
into arelatively line potassium salt enrichedfraction; feed
than said second impact velocity so as to form a further
means for feeding said particulate raw material to'said
?rst impact crusher; a second impact crusher of the same
mixture of clay enriched larger particles and potassium
salt enriched smaller particles; screening the thus formed
further mixture so as to separate the same into said
further formed smaller potassium salt enriched particles
and clay enriched larger particles; and recovering said
separated potassium salt enriched smaller particles formed
in said several impact comminution steps.
4. In a method of separating sludge-forming clay con
type as and operatively. connected to said ?rst impact
crusher, said second impact crusher including means for
rotating the rotor of said second crusher at aspeed greater
than said predetermined speed for further crushing said
relatively coarse clay enriched fraction into a further
clay enriched relatively coarse fraction and a potassium
enriched relatively ?ne fraction; a third impact crusher
stituents from a particulate mined raw material contain
of the same type as said ?rst impact crusher and opera
ing a potassium salt and sludge-forming clay constituents,
tively connected to said second impact crusher, said third
impact crusher including means for rotating the rotor
thereof at a speed which is less than the rotational speed
of said rotor of said second impact crusher for separat
ing the further clay enriched fraction from said second
impact crusher into a relatively ?ne potassium salt en
riched fraction and a relatively coarse clay enriched
fraction; screening means operatively associated with each
' the steps of subjecting particulate sludge-forming clay and .
potassium salt-containing mined raw material including
also particles in the size range of between 40 and 160 mm.
without prior impact comminution to a ?rst impact com
minution at a ?rst predetermined impact velocity so as to
form of said raw material a mixture of clay enriched
larger particles and potassium salt enriched smaller par
of said impact crushers for separating the relatively coarse
from the relatively ?ne fraction formed in the respective
impact crushers; conveying means for passing the thus
separated relatively coarse fraction produced in said ?rst
and second impact crushers to the second and third im
greater than said ?rst impact velocity so as to form a sec
ond mixture of clay enriched larger particles and of potas 30 pact crushers, respectively; and collecting means for col
lecting the relatively ?ne potassium salt enriched fractions
sium salt enriched smaller particles; screening after said
produced by said impact crushers.
second impact comminution the mixture of larger and
ticles; screening the thus-formed mixture so as to separate
the same into said smaller and larger particles; subjecting
the thus separated clay enriched larger particles to a
second impact comminution at a second velocity being
smaller particles formed thereby so as to separate the
same into smaller and larger particles; subjecting the thus
' separated clay enriched larger particles to impact coin-'
minution at a third impact velocity being smaller than
12. In a device according to claim 11, wetting means
operatively associated with at least one of said screening
means for wetting at least one of said clay enriched frac
tions prior to introduction of the same into the subsequent
said second impact velocity so as to form a further mix
impact crusher.
ture of clay enriched larger particles and potassium salt
enriched smaller particles; screening the thus formed
13. In a device according to claim 12, a last impact
crusher of the same type as said ?rst impact crusher, said
further mixture so as to separate the same into said
further formed smaller potassium salt enriched particles
_ and clay enriched larger particles; and recovering said
separated potassium salt enriched smaller particles formed
in said several impact comminution steps.
5. A method according to claim 4 wherein prior to the
last impact comminution said potassium’ salt containing
particles are treated with low pressure steam so as to form
‘
last impact crusher being adapted to receive the coarse . ,
fraction from the screening means associated with said
third impact crusher for further comminution of said’
fraction, said last impact crusher including blower means
for contacting said coarse fraction during comminution
of the same with hot air.
14. ‘In a method of separating sludge-forming clay con
stituents from. a particulate mined raw material contain
ing a potassium salt and sludge-forming clay constituents,
the steps of subjecting particulate sludge-forming clay and
6. A method according to claim 4, wherein said clay
enriched particles obtained by impact comminution at 50 potassium salt-containing mined raw material including
also particles in the size range of between 40 and 160 mm.
said third velocity, after separation from. the potassium
without prior impact comminution to impact comminu
salt enriched fraction, are subjected to at least one further
tion at a ?rst predetermined impact velocity so as to sepa
impact comminution at an impactvelocity of between 25
rate said raw material into clay enriched larger particles
and 70 m./sec.
and potassium salt enriched smaller particles; recovering
7. A method according to claim 6, wherein during said
said potassium salt enriched smaller particles from the
further impact comminution of said clay enriched particles
thus formed particulate mixture; subjecting said clay en
the same are contacted with hot air so as to dry said
a thin layer of. water on said particles.
particles.
'
8. A method according to claim 4 wherein the material
‘to be treated is wetted at least once after the ?rst and
before the last impact comminution.’
9. A method according to claim 4 wherein a wetting
' agent is applied to the material to be treated at least once
riched larger particles to impact comminution at a sec
ond velocity being at least about 35% greater than said
?rst impact velocity so as to separate said clay enriched
particles into further potassium salt enriched smaller par
ticles and larger clay enriched particles; recovering said
further potassium salt enriched particles; and subjecting
the thus separated clay enriched particles to impact com
after the ?rst and before the last impact comminution.
10. A method according toclaim 4 wherein a liquid is 65 minution at a third impact velocity being smaller than said
second impact velocity by at least about 15%,v so as to
applied to the surface of the separated clay enriched larger
cause further separation into clay enriched larger particles
vparticles formed in the, last of said second impact com
and smaller potassium salt containing particles of greatly
minutions prior to subjecting said particles to impact com
reduced clay content.
minution at said third impact velocity; and wherein said
15; ‘In a method of separating sludge-forming clay con
' liquid is applied in a quantity equal to about 0.5% of the 70
'weight of said larger particles.
stituents from particulated sylvitic hard salt deposits as a
11. In a device for separating sludge-forming clay con
. raw material containing a potassium salt and sludge-form
ing clay constituents, the steps of subjecting particulate
prising crude potassium salts and sludge-forming clay
sludge-forming clay and potassium salt-containing mined
constituents, in combination, a ?rst impact crusher of the 75 raw material including also particles in the size range of
stituents from a particulate mined raw material com
3,096,034
13
14
between 40 and 160 mm. without prior impact comminu
tion to impact comminution at a ?rst predetermined im
respective second impact comminution so as to separate
the same into smaller and larger particles; subjecting the
pact velocity so as to separate said raW material into clay
separated clay enriched larger particles formed in the last
enriched larger particles and potassium salt enriched
smaller particles; recovering said potassium salt enriched
smaller particles from the thus formed particulate mix
ture; subjecting said clay enriched larger particles to im
of said second impact comminutions to impact comminu
tion at a third impact velocity being smaller than said
second impact velocities so as to form a further mixture
of clay enriched larger particles and potassium salt en
riched smaller particles; screening the thus formed further
pact comminution at a second velocity being at least about
35% greater than said ?rst impact velocity so as to sepa
mixture so as to separate the same into said further formed
rate said clay enriched particles into further potassium 10 smaller potassium salt enriched particles and clay enriched
salt enriched smaller particles and larger clay enriched
larger particles; and recovering said separated potassium
particles; recovering said further potassium salt enriched
salt enriched smaller particles formed in said several im
particles; and subjecting the thus separated clay enriched
pact comminution steps.
particles to impact comminution at a third impact velocity
being smaller than said second impact velocity by at least 15
about 15%, so as to cause further separation into clay
enriched larger particles and smaller potassium salt con
taining particles of greatly reduced clay content.
16. In a method of separating sludge-forming clay con
stituents from a particulate mined raW material contain 20
ing a potassium salt and sludge~forming clay constituents,
the steps of Wetting particulate sludge-forming clay and
potassium salt-containing mined particulate raw material
including also particles Within the size range of between
References Cited in the ?le of this patent
UNITED STATES PATENTS
139,782
Goodhart ____________ __ June 10, 1873
256,073
368,900
1,147,211
Taggart ______________ __ Apr. 4, 1882
Ryerson ______________ __ Aug. 23, 1887
Coleman et al. ________ _. July 20, 1915
2,023,247
2,464,212
Senseman ____________ __ Dec. 3, 1935
Carter ______________ __ Mar. 15, 1949
v2,609,150
Bludeau _____________ __ Sept. 2, 1952
25
2,789,772
2,826,370
2,889,119
WilliarnSen __________ __. Apr. 23, 1957
Weston ______________ __ Mar. 11, 1958
Andreas ______________ __ June 2, 1959
screening the thus-formed mixture so as to separate the 30
20,115
Great Britain ______________ __ of 1913
40 and 160 mm. ; subjecting said Wetted raw material With
out prior impact comminution to a ?rst impact comminu
tion at a ?rst predetermined impact velocity so as to form
of said raw material a mixture of clay enriched larger
FOREIGN PATENTS
particles and potassium salt enriched smaller particles;
same into said smaller and larger particles; subjecting the
thus separated clay enriched larger particles to a plurality
of successive second impact comminutions at second ve
locities being greater than said ?rst impact velocity so as
to form successive mixture of clay enriched larger par
ticles and of potassium salt enriched smaller particles;
screening after each of said second impact comminutions
the mixture of larger and smaller particles formed in the
76,400
Germany _____________ __ July 27, 1894
697,309
Germany _____________ __ Oct. 10, 1940
OTHER REFERENCES
Dana’s Manual of Mineralogy, fourteenth edition, pp.
180, 186 and 323.
Handbook of Chemistry, by Lange, ninth edition, pp.
1101 and 1102.
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