Note: Descriptions are shown in the official language in which they were submitted.
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K~LI UND SALZ ~KTIENGESELLSCHAFT. 3500 Ka66el
Priedrich-Ebert-StraBe 160
Crude potash 6alts, which are almost entirely of oceanic origin, often
contain argillaceous or sludge-forming components which generally exert
a very disruptive effect on the processing of the crude 6alts. This
phenomenon occurs both in the case of the classical processing methods,
6uch as hot dissolution and flotation, as well as in the case of the
electrostatic 6eparating processes, which have gained in popularity in
recent years.
A general revie~ of the electrostatic method of separation is given in
"Chem-Ing-Tech" 53 (1981), Nr . 12, p . 916 .
Usually, the clay admi~ture6 act non-specifically and non-selectively
during electrostatic 6eparation, i.e. they distribute themselves amongst
all the fractions, but in general they display a tendency to concentrate
more on the potash minerals. At low clay contents thi6 can frequently
be tolerated; but given higher proportions of clay, and particularly
when higher ~rade products, such as KCl with a minimum content of 60%
~2 are to be produ~ed, specif~c ceparation of the clay cannot be
avoided.
There has been no lack of attempts to modify the charge characteristics6pecifically of the clay minerals.
A procedure according to Ger~an patent application AS 10 52 921 which
employs the "conducti~ity method" has never been used industrially
because of the high cost6 involved.
In German patent PS 17 ~8 708, the crude 6alt is treated with one or
more aliphatic amines containing 8 to 22 carb~n atoms, and ~ith one or
more aliphatic carboxylic acids contain~n~ 8 to 22 carbon atoms, and
then 6eparated at approxiately 70-C. Laurylamine, in particular, is
used in very large amounts between 100 and 1,000 g/t in this process.
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,
The concentrate 6till contains 4.9 to 6.3% insoluble matter, so that it
is not possible to achieve the purity of a KCl standard product of 60%
K20 .
According to German patent PS 20 07 677, conditioning is carried out
with lactic acid in combination with halo carboxylic acids; the clay is
precipitated out at the positive electrode and the low-clay crude salt
at the negative electrode. This fraction is then further processed
using one of the classical methods such as flotation.
According to German patent PS 20 52 993, conditioning is carried out
with dinitrophenol by itself or together with halo carboxylic acids, and
a clay-rock salt fraction is collected at the positive electrode and a
sylvine-kieserite fraction is collected at the negative electrode. Here
again, the valuable fraction is further processed by flotation.
According to German patent PS 31 27 946, in addition to fatty acids,
ammonium acetate or pyrogenic silica can be used as the conditioning
agent, and the separations are carried out in an inhomogeneous
electrostatic field. The low-clay concentrates are further treated in a
hot solution process.
In a further development, German patent PS 32 16 735 describes a
complicated electrostatic multi-stage process using double conditioning
of the salts with fatty acids/salicylate acid as well as fine-grained
silica. Although in this method it is not possible to completely force
the clay into the rock salt residue, nevertheless some of the potash can
be recovered as a ~low-clay product containing 60% K20, while part of the
potash still has to be treated by classical proces6ing methods.
This review of the current state of the art shows how difficult it is to
process crude argillaceous salts, and it also shows that so far no
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optimal solution has been found. Clay-specific reagents hinder the
necessary triboelectric charging of the sylvine in relation to the other
components of the concentrate containing the sylvine, and thus they make
it difficult to carry out further electrostatic preparation of these
concentrates. In particular, it has so far proved impossible to find
any reagents and processes which can separate carnallite
(KCl.MgCl2.6H20) from sylvine. In order to obtain maximum concentrates
of potassium chloride, it has so far always proved necessary to fall
back on the wet process so that the undesired MgCl2 can be dissolved and
thus removed. The goal of developing a process which is drv all the way
through to the end product, was therefore not achieved. In each case,
the end product had to undergo additional drying.
A process has now been found by means of which crude argillaceous salts,
in particular also hard salts, can be electrostatically separated; this
is done by 8rinding the salts to a grain size of less than 2 mm, mixing
the salts with an organic substance acting as a conditioning agent, and
treating them with air at a given temperature and humidity level; then,
following triboelectrical charging of the salts, they are fed to a free-
fall separator having a certain field strength of, for example, 4,000
V/cm which separates them into 3 fractions; the middle range fraction is
reground and recycled and added together with the crude salt feed.
Then the crude salt is conditioned with alkylammonium salicylate, whichresults in clay being precipitated along with other undesired components
at the positive electrode and the valuable material is precipitated at
the negative electrode.
The valuable material accumulating at the negative electrode is sylvineor sylvine and kieserite.
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At the positive electrode, the carnallite also precipitates out together -
with sodium chloride.
It is primarily the appropriate methyl, ethyl, propyl or butyl form of
the alkylammonium salicylate which is used as the conditioning agent.
The alkylammonium salicylate conditioning agent is used in amounts of
between 30 and 200 g/t crude salt, preferentially in an amount between
80 and 120 g/t. The relative humidity of the air is between 5 and 12~,
corresponding to a temperature of 40 to 55 C.
Since three fractions are formed during the electrostatic separation ofthe crude argillaceous salt, the Diddle fraction can be reground and
recycled back to the initial crude salt feed.
The invention is described in more detail in the following examples.
The starting material was a crude salt having the following composition:
1~.35% K20
16.09~ sylvine
1.10X carnallite
26.83~ kieserite
54.42~ rock ~lt
0.76X anhydrite
0.80~ clay minerals
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Exa Ples 1 to 3
According to the invention, the crude salt is mixed together with the
conditioning agent methylammonium salicylate, which is produced by
reacting aqueous methylamine solution with salicylic acid, in the
proportion of 100 g/t for 2 minutes in a Lodige mixer; then, while still
being stirred, it is placed for 20 minutes in the laboratory climatic
cabinet where it is exposed to alternating reIative humidities in the
ambient air. The absolute humidity of the air is 5.8 g/m3.
The results are apparent fro~ Table 1, Examples 1 to 3.
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Table 1
~herm. corld. - .Content - ( S ) ~ r~ ( S )
DOS E ~ddle neg EDos. E. neg,
C % rel. hu~ raction '
eff. amount 28, 5 36,2
~2 2,62 7,29 1~,42 7,2 67,9
. Syl~ine 3,~0 11,19 30,62 6,6 68,9
1 - Carnallite t,67 1,32 ~ 0,44 ~'~,J j~S
57 S,0 ~eserite 3,25 17,97 54,03 ~.5 72,9
Rock salt 69,45~ 68,12 1:~,45 46,9 8,5
ydrlte 0.3~ 0,80 1~03 13,9 49, ~
Clay min2rals1,52 0,60 0,43 54,2 19,5
eff. amount 26,6 34,4
K20 1,96 ~,~2 20,9; ~,0 6G,6
~. . .............. . --. ------..... .--...... .. .. .. .
Sylvfne 2,58 1~,41 32,98 4,3 7~,5
Carnallite 1,g4 0,91 0,6~ 46,9 21,0
43 10,0 ~ie5erite 3,82 17,52 55,18 3,8 70,1
2 ~k salt 89,~2 69,74 9,75 43,9 6,2
~nhydrlte 0,-6 0,?S 1,00 16,1 45,3
Clay minerals t,<8 0,67 0,~2 49,2 18,1
~ff. amount 2'~,5 2~S.9
~ 2 1,76 ~,S9 21,88 ~,0 61,1
..... . .... . ... . . ...... ~ .. .. . ... .
~ S~lvine 2,19 lt,tS 34,54 3,2 62,0
Carnalll~e 2,22 0,97 0,40 47,4 lo,s
38 12,5 Kleserlte 6,12 26,36 44,44 5,4 47,9
RDck salt ~7,69 59,29 19,35 37,9 10,3
te 0,52 0,82 0,86 16,1 32, 7
Clay minerals1,26 0,81 0,~1 37,0 14,8
~6. E. = Fraction at the positive electrode
. E. = Fraction at the negative electrode
Yield
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E~a Ple 4
In a subsequent test, salicylic acid was reacted with butylamine
(instead of methylamine) and the following result was obtained:
Table 2 (Example 4)
Content (~
pos.E. Middle neg.E. pos.E. neg.E.
fraction
effective amount13.8 44.9
K203.58 6.80 16.10 4.7 68.7
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Sylvine 4.96 10.5 25.34 4.2 69.4
Carnallite 2.64 1.00 0.56 35.4 24.4
Kieserite 4.61 17.75 51.30 2.1 74.3
Rock salt 83.67 68.64 21.28 23.3 19.3
Anhydrite 0.30 0.71 0.99 5.3 57.0
Clay minerals 3.82 1.39 0.53 39.3 17.0
In the procedure according to t~e invention the charges of all the saltminerals, with the exception of carnallite, are reversed. Sylvine,
kieserite and anhydrite are now separated at the negative electrode,
while rock salt, carnallite and the clay materials are separated at the
positive electrode. The low-clay fractions can be easily further
processed accordin~ to the e~ectrostatic separation method, as well as
by the flotation method, into high percentage potash fertilizer salt.
In addition, thære is the further advantage that the carnallite acquires
an opposite charge from sylvine, and this can considerably facilitate
subsequent treatment operations, including wet treatment.
