DE1267182B - Process for the flotation of sylvine from crude potash salts containing clay-like constituents - Google Patents

Description

Process for the flotation of sylvine from clay-like constituents Potash Crude Salts The invention relates to a process for the flotation of sylvine Potash crude salts containing clay-like components, in which the crushed crude salt Pre-classified into two grain fractions and after conditioning at least one fraction a multi-stage, preferably two-stage flotation is abandoned.

The invention particularly relates to an improved method for Separation and concentration of the non-metallic sylvin components from sylvinite salts, the small but undesirable amounts in their naturally occurring form contain insoluble clay-like minerals that form sludges that increase the concentration the sylvene content of such salts by flotation and other common extraction processes affect. Sylvin (KCI) comes in larger quantities in North America, for example on the deposits of the Permian Basin, particularly in the area around Carlsbad in New Mexico, before.

The sylvinite salts come from the corresponding geological layer dismantled in the usual way and initially broken or roughly crushed. In the Concentration of the potassium fractions of such sylvinite salts by flotation, it is common to carry out a desludging process beforehand, which consists in the coarsely ground salt washed by sprinkling to remove most of the unwanted To remove sludge from it. One saturated with the components of the salt Lye is usually added to the sand and the coarser particles of the crushed salt added, and a turbidity is thus produced. The one made in this way Turbidity is then subjected to various vigorous stirring processes, which are called Beriese-Itings- or washes are known to remove the mud from the salt crystals of the sand and to free the coarser particles of salt, whereupon the remaining sludge is slurried or suspended in the liquor. Thereupon the cloudiness before the Flotation treated and classified in conventional equipment suitable for this purpose, such as B. with cyclones, screen classifiers, fixed or moving sieves, classifying cones, Bowl classifiers, hydraulic separators and the like coarser as well as those made up of finer particles after the treatment by the above Classification was obtained, conditioning with anti-sludge agents (Inhibitors), collectors, foaming agents and foam regulating agents subjected and the conditioned pulp obtained in this way prior to the recovery of the finished product first or flotation pre-expander stage and a second or purification stage (rich foamer stage) given up. The additional non-slimming agents used were during of the conditioning added to avoid impairment by the remaining sludge to prevent that in the sludge after the end of the desludging process lagged behind. The complete removal of the mentioned sludge by usual mechanical methods have proven impractical.

There is another difficulty with the aforementioned method in the disruptive influence of the remaining sludge on the flotation process, the contained in substantial amounts, especially in the pulp with finer particles and the flotation and thus the extraction of the coarser particles of the sylvine components prevented to a considerable extent even if during conditioning an appropriate inhibitor is used.

According to the invention, it has now been found that by separate treatment of the fine trilbe removed from the classifying device and by separate treatment of the sludge contained therein with a suitable inhibitor and by direct application of the fine sludge which still contains the sludge treated with the inhibitor , in the purification-flotation stage (rich foaming stage) there is a sufficient amount of collector and foam-regulating reagents in the concentrate of the pre-foaming stage, which was obtained from the pulp of coarser particles treated in the pre-foaming stage, and that this excess foam-regulating agents are sufficient to effectively condition the fine pulp and thus to bring about an excellent recovery of the sylvine content from this and also from the coarser pulp.

By bypassing the pre-foaming stage, the finer turbidity fraction the efficiency of the froth flotation in terms of obtaining the coarser particles the proportion of sylvin is significantly increased. In addition, omitting the pre-expander stage leads to in the specified manner to a substantial reduction in the achievement of a effective separation of the sylvine components from the gangue required amount of reagents. Other objects and advantages of practicing the present invention will emerge from the description below.

The inventive method is characterized in that only the fraction of larger grain size is conditioned and only this one pre-flotation stage is abandoned, whereas you, fraction of smaller grain size together with the concentrate the pre-flotation stage is given up directly to a post-flotation stage.

You, the finer fraction of the salt is in the form of a very finely divided one (highly diluted) turbidity, in addition to the desired sylvin content contained therein contains most of the remaining sludge, that of the coarser fraction was separated. The "undersize" or the fine particles are expedient from the sludge through a hydroseparator or similar classification plant separated at which the overflow a high percentage of the remaining sludge and contains a relatively low percentage of the sylvine components. The lower course the hydro separator or a similar device contains one high percentage of the Sylvi # n components abandoned to the device and a relative low percentage of sludge.

The "oversize" and the coarser particles of the salt yield a slurry high density, from the still further, however, minor amounts "undersize" particles, d- h. Particles of a size of about 0.20 mm or finer, and sludge during the subdivision into the different particle sizes or during the classification of the particles of the high density pulp can be segregated if the pulp through a number of such devices as cyclones, Stirring devices and / or fixed sieves or the like. Is passed. The separated fine particles and the remaining sludge are then given to a hydro separator together with the originally separated fine fraction.

The coarser turbidity, high density, is then reduced by adding sludge regulators, Collectors, frothers. and foam control reagents immediately prior to the introductory one Flotation process conditioned, the above and as usual as a pre-expander was designated. So far, the partially desludged has been removed from the hydro separator preserved underflow, which contains the finer parts, the coarser desludged, high solids slurry, just before the previous one Action level supplied again.

In the process according to the invention, this step and the fine, partly desludged turbidity becomes after the addition of suitable inhibitors directly to the rich frother stage, which is the second flotation stage for the coarser sludge content, represents, supplied.

The action stage and the pre-expander stage are therefore only applied to the high-density pulp containing the coarser or oversized grain fraction, and the conditioning agents, which have an affinity for the sylvine components, are only added to this pulp according to the invention. Suitable cationic collectors for achieving the concentration of the desired sylvine components from the sylvinite salt are surface-active agents, such as water-soluble amine salts, such as the quaternary ammonium salts, e.g. B. cetyl pyridine bromide, heptadecylamine hydrochloride; the water-soluble salts of monoalkyl-substituted guanidines in which the alkyl substituent is a normal, primary, aliphatic radical having 6 or more carbon atoms, e.g. B. dodecylguanidine hydrochloride and the salts by acid addition to normally primary, secondary or tertiary aliphatic amines which are saturated or olefinically unsaturated form and contain 8 to 22 carbon atoms. However, primary amines are preferably used. Examples of the amine salts mentioned above are stearylamine hydrochloride, laurylamine hydrochloride, octylamine hydrobromide, myristylamine hydrochloride, pentadecylamine hydrochloride, octylamine hydrochloride and like salts of margarylamine, myristoleylamine, palmitoleylamine, oleylamine and linoleylamine.

The above-mentioned collectors are added to the coarser pulp directly or in connection with oils which are immiscible with water, such as heating oil, kerosene or pine oil, or a commercially available foamer such as methyl isobutylcarbitol, which interact with the above-mentioned amine salt flotation agents. In addition, in some cases it is desirable to use certain dilute inorganic acids or alkalis to properly adjust the pH of the conditioned pulp so that the highest possible concentration of the particular mineral desired, e.g. H. the sylvin, is obtained.

In the above-mentioned pre-expander stage, which follows the conditioning of the coarser pulp, substantial amounts of the buoyant sylvine components are separated from the gangue, for example, and flotation cells used within the pre-expander stage appear on the surface in the form of a foamy pulp concentrate, which is produced as a concentrate of the pre-expander stage (pre-expander concentrate ) referred to as. The Vorschäumerkonzentrat contains the broad spectrum of coarser Sylvinteilchen that were originally present in the salt, of course, with the exception of the sludge 'of the previously in the upstream Entschlammungsstufe from or together with the Unterkomteilchen for separate treatment before reintroduction and mixing in the following Reichschäumer - or Purification stage had been segregated.

In addition, the sylvin particles are also missing in the pre-expander concentrate, which have not floated up in the pre-expander stage and therefore together with the Gait or the outflows of the pre-expander stage are discharged; such misalignments however, according to the invention, they are very low.

In addition to the sylvin content, it contains that obtained from the pre-expander stage Pre-expander concentrate still contains fine particles of gangue contained in the foam of the pre-expander concentrate be carried mechanically. This lag in pace is of course a Contamination of the sylvin content. To avoid these undesirable impurities remove, the pre-expander concentrate is a second flotation process, which is called Cleaner or rich foamer is referred to, subjected. As known, speak the coarser fractions of the pre-expander concentrate generally do not have one Flotation in the second or purification stage. Thus, between the previous An intermediate screening is carried out in the pre-expander stage and the cleaning stage.

A sieve cloth (screen lining) is used, the mesh size of which is large enough to contain both the desired fractions of the sylvine concentrate as to let through the gait particles of the same size; on the other hand, the mesh size should however, be so small that the remaining and coarser fractions of the Sylvinkonzentrates is prevented. The recovered, less coarse fractions of the Pre-expander concentrates are then used together with that from the above-mentioned hydro separator obtained, consisting of fine sludge, the lower reaches of the rich foaming stage are abandoned. The remainder of the gangue rocks in this second flotation stage in a similar manner removed as in the previous pre-expander flotation stage. In the Reich foamer stage one works without further addition of collector and foam regulating flotation reagents into the concentrate of the pre-expander stage or the finer pulp that is in this stage flows in because it was found that collectors and foam regulators in the pre-expander concentrate Reagents are present in an amount sufficient to keep the underflow out the hydroseparator effluent pulp within the high foamer stage condition and an excellent extraction of the desired mineral, namely des Sylvins to ensure from this.

As mentioned earlier, it is common to have the disturbing influence of the still sludge located in the turbidity on the collector effect, especially the coarser one Particles to be prevented by adding one in the conditioning stage an inhibitor-regulating reagent is used.

In the present case, this regulating float is the finer one Added slurry after it was removed from the hydroseparator as an underflow and immediately before this turbidity, consisting of the finer particles and the rest Sludge that is fed to the flotation cells of the rich frother stage. Such inhibitors are for example starch, dextrin, the polyglycols and their esters and water-soluble ones Acrylonitrile polymers in which at least one nitrile group is caused by alcoholysis to the corresponding ester and / or by alcoholic hydrolysis to the corresponding Salt has been converted. Examples of such polymers are those from Dow Chemical Co. under the trade names NP-10 and NP-20 sold products that were essentially consist of water-soluble acrylonitrile polymer, in which one partially, however incomplete saponification of the reactive carboxyl groups was carried out. These polymers have a relatively high molecular weight, which can be compared with larger Designation numbers increased.

The above-mentioned acrylonitrile polymers are used successfully as a regulating flotation agent in conjunction with the polyglycols mentioned and their esters, e.g. B. methoxypolyethylene glycol with a molecular weight of about 750 (MPG-750) or a polymer is used which consists essentially of mannose units, such as mannogalactan, which is obtained, for example, from the endosperm of guar seeds.

Because, as already stated, the coarser sylvin particles float more poorly than finer particles due to the increased ratio of mass to surface, the presence of sludge in the turbidity, which tends to hinder the floating of the fine sylvin particles in the turbidity, has a particular effect detrimental to the coarser particles, d. H. those whose grain size is 1.19 or more. As a result, the fact that the finer pulp with the remaining sludge contained therein is only added after the pre-expander flotation stage leads to a significantly increased flotation efficiency for the coarser fraction of the sylvine content, which is obtained in the pre-expander flotation stage and represents the above-mentioned pre-expander concentrate. If the sludge flowing down from the hydroseparator in the underflow, which contains varying amounts of remaining sludge, would be added to the coarser sludge that was conditioned with reagents before the pre-expander stage - as was the case with the previously known extraction processes - then the (in the sludge) present the flotation of the coarser fractions of the sylvine components and therefore partially destroys the purpose of the pre-expander flotation stage. So far, this disruptive influence of the sludge has been counteracted in part by using increased amounts of inhibitors, collectors and foam-regulating floats and by keeping the density of the underflow of the hydro separator as high as possible with regard to the solids.

If you remove the fine If turbidity does not give up any pre-expander stage, a considerable reduction is achieved the amount required to effectively separate the sylvin content from the gangue of flotation reagents.

A third flotation stage can and should be expedient the sylvinite salts. This third or post-frother flotation stage (Post-purification step) is carried out in the same way as that described so far Flotation process. The Sylvin concentrate is obtained in the post-foaming stage and removed.

The foam flotation methods used in the present invention are customary Processes that can also be carried out with the usual flotation cells. While the method described here is particularly useful for concentration and extraction of sylvin from the sylvinite salts found in the Carlsbad, New Mexico, can of course be dismantled with the same success also apply to similar occurrences containing potassium chloride, using the Schaurn swimming method can be processed, such. B. in the occurrences in the vicinity of Trona, California, and Bonneville, Utah. The drawing is a schematic family tree to further explain the present invention. It also includes for comparison purposes References to the method best known in this field to date.

As shown in the family tree, in which the same numbers mean the same processes and process steps, the mined raw salt is first comminuted in the customary manner using customary comminution and grinding devices by first pre-comminuting it and then using a hammer mill, ball mill, rod mill or the like. Like. Abandoned to expose the sylvine components of the salt. The crushing and milling is normally done with essentially dry salt. The mill discharge 2 obtained in this way is then mixed with a lye which is saturated with the constituents of the crude salt in an amount sufficient to form a pulp, which is then vigorously stirred in various ways in a washing device 4, whereby substantial amounts of the present Sludge can be dissolved from the salt crystals and suspended in the lye. Following this preliminary washing process, the sylvinite turbid water devices are abandoned. While the classification, as indicated in the graph, can be carried out in various ways, the sludge obtained from the initial washing process is fed into the cyclones 6 , in which the crushed sylvinite salt is initially and essentially divided into two fractions one of which is "undersized," d. H. with a grain size of about 0.20 mm or finer, and the second contains particles with a grain size of over 0.20 mm. The former or first fraction contains both undersized sylvin particles and a substantial amount of sludge. This first fraction is passed into a bowl classifier 12 as a suspension. The overflow of the bowl classifier reaches a hydro separator 8, from which a high concentration of sludge and very small amounts of sylvine suspended in the liquor are removed as overflow and fed to the liquor recovery device.

At the same time, the larger pulp is made up of oversized particles, i.e. H. with a size of more than 0.20 mm initially obtained from the cyclones 6 , placed in a quadruple rake classifier 18 to remove the coarsest parts from the pulp. The coarser pulp, which normally has a high density and contains the so-called oversized particles, is then applied to the conditioning device 20 for the subsequent flotation. The undersized particles in the overflow from the quad screen classifier 18 are added to the fine sludge from the cyclone overflow and fed to the bowl classifier 12. The coarser particles or grains of sand obtained in the bowl classifier 12 are then fed to the conditioning devices 20 for subsequent flotation.

The conditioning of the coarser pulp consists of the addition of sludge-preventing reagents, collectors, foaming and foam-regulating reagents, i. H. an acidic addition salt such as the product sold by Armor & Co. under the trade name "Armac TD", which consists of the water-soluble acetate salts of the normal hexadecyl, octadecyl and actadecenyl amines in proportions of 30 to 25 to 45 parts by weight and which cooperate with them Reactants such as heating oil, kerosene, pine oil and methyl isobutyl carbitol (MIBC). The conditioning stage is ended by stirring the pulp with the stated reagents in the conditioning devices 20 for at least 20 seconds. The stirring process is carried out either mechanically or by introducing a stream of air or another non-reactive gas.

According to the invention, only 50 ... 115 g of amine reagent per ton of solid are in the mill discharge, i. H. per ton of broken sylvinite salt that was fed to the washing device 4 at the beginning, and only 15 ... 25 g of flotation oil reagent (e.g. the product no. 634 from Allied Chemical and Dye Co, used in the manufacture of cresol as Crude by-product is obtained) are required per ton of solid in the mill discharge for the conditioning stage20.

Likewise, the required quantities of MPG-750, NP-10 and MIBC are only around 55 ... 100 g / t, 2.5 ... 100 g / t and 20 ... 25 g / t mill discharge. In addition, if NP-20 is optionally used, the amount normally used is no more than 1134 g / t mill output. Thus, the total amount of flotation agents that is added according to the invention during the conditioning stage is between 12.7 and 267.6 g / t of the mill discharge. The effect of the collectors, frothers and foam-regulating reagents added in this way is immediately used in the pre-expander flotation stage 22, which follows the conditioning.

As has been customary up to now, in the pre-expander stage all buoyant sylvine components are separated from the gangue and appear in the flotation cells used within the pre-expander stage as a foamy pulp on the surface. The foam obtained in this way, which is the pre-expander concentrate, contains all the coarser sylvin particles that can be obtained, i.e. H. Sylvine particles with a grain size greater than 0.05 mm that were originally present in the sylvinite salt, with the exception of the very fine particles that were removed in the preliminary desludging and washing processes, and with the exception of the few particles that were either not in the pre-expander stage float up, but are discharged together with the pace in the outflows of the pre-expander stage, or which are so large and coarse that they do not respond in a characteristic way to the flotation processes used in the rich frother stage. For this reason, various methods have been used in order to avoid a loss of non-buoyant, but coarse particles in the high foaming stage. A method which is preferably used, as indicated here, is the use of screens 24 in which the mesh size of the screen lining is so large, i. H. greater than 0.60 mm, so that the larger and coarser sylvin particles (as retention) are obtained, but in contrast to this, the finer fractions of the pre-expander concentrate go through for processing in the rich frother stage 26 . The coarser fractions obtained by sieving 24 are then dewatered in a suitable manner, and the coarse sylvine fractions are obtained in this way.

The finer fractions of the coarser pulp, which are fed to the rich frother stage 26 from the sieves 24, are added (before the rich frother stage 26) to the underflow coming directly from the hydroseparator 8 and consisting of fine pulp. At 15, before it is fed into the Reichschäumer flotation device, an above-described regulating inhibitor flotation agent is added to this underflow, which consists of fine-grained fractions and remaining clay sludge, in order to reduce the disruptive effect of the remaining sludge on the flotation of the sylvine fractions, in particular on coarser particles particles with a grain size of 1.19 mm or larger, which are present in the turbidity of the underflow, are to be picked up.

The concentration of the water-soluble acrylonitrile polymer used as the regulating flotation reagent is about 2 ... 50 g / t sylvinite mill discharge.

The sylvine fractions obtained via the flotation cells of the high-foaming stage26 are then expediently given to a third post-frothing or post-purification stage, in which all of the remaining sludge and all aqueous components are removed in order to obtain high-concentration sylvine fractions as a finished product 30 .

With the aid of the schematic representation of the drawing, it can be seen that in the conventional methods previously used, the underflow of the hydraulic separator 8 is fed to the conditioning devices 20, where it is mixed with the coarser pulp contained therein. After conditioning, in which the regulating inhibitor flotation agent is also added, this pulp is fed to the pre-foamer stage 22 and then to the sieving 24 before it reaches the rich foamer stage 26. Thus, the less coarse fractions of the pre-expander concentrate treated with flotation reagents as well as the underflow of the hydroseparator 8, which contains the fine fractions and the remaining sludge, are given up to both the pre-expander stage 22 and the high-expander stage 26, as already mentioned above.

The invention is further illustrated by the following examples.

EXAMPLE 1 In a large-scale operational test, four tons of a larger amount of sylvinitroh salt, which was mined in the area of Carlsbad, New Mexico and contains about 22.9% K20 (corresponds to 36.25% sylvine), are or . -mills crushed in a closed circuit with vibrating sieves. The mill discharge obtained in this way (in four separate samples) is subjected individually and one after the other to a washing process in order to carry out a first desludging after adding a saturated lye to form a pulp. The saturated lye used here is produced from a different amount of crushed sylvinite salt by stirring it with water at room temperature until no more sylvinite salt dissolves. The lye is thus saturated with the components of the crude salt. It is produced in the course of the present process and, as described in more detail below, recycled. Their specific gravity is around 1.240. The initial washing or desludging process takes about 30 minutes.

The pulp subjected to the aforementioned washing process contains about 60 percent by weight of suspended solids. The pulp obtained is then initially divided into two fractions in a number of cyclones, one of which has a proportion of 150 / e with a grain size of about 0.20 mm or smaller and the other has a proportion of 85.9 / o , with a grain size of over 0.20 mm. The particles with "undersize," i. H. with a grain size of 0.20 mm or smaller are removed and the substantially coarser particles, i.e. H. Pulp containing particles with a grain size of more than 0.20 mm are classified again in a four-fold computer classifier. The residue obtained here and containing the undersized particles is then added to the fine sludge containing the undersized particles separated off in the cyclones at the beginning. The four samples of coarse pulp containing the oversized particles obtained from the quadruple classifier are then applied to conditioners in which each of the samples mentioned, i.e. H. the samples a) to d), reagents are added in amounts as listed in the following table I (values in g / t mill output). Table 1 Sample MPG ions test_ total NP-10 Amine MIBC Flotat Oil NP-20 addition 750 No. 634 reagents reagents a) 96.0 3.10 109.0 23.7 23.7 7.90 264 b) 61.2 5.3 74.16 20.0 20.0 18.50 197 c) 60.8 5.20 75.6 20.0 20.0 1.20 1.55 184.5 d) 55.6 8.2 74.1 20.0 20.0 4.90 181 After adding the reagents listed above, stirring in the conditioners is continued for about 8 minutes. The finer pulp obtained from the cyclones is treated separately in a bowl classifier, which is used to remove further remaining sludge. The overflow from the quadruple computation classifier is also fed into the bowl classifier and treated there in the same way. The sand residues obtained from the bowl classifier are then fed to conditioners before flotation. The overflow from the bowl classifier is then fed to a hydro separator, the remaining sludge and lye containing overflow from the separator is drained off. Then 2 ... 50 g / t mill discharge of a sludge-preventing flotation agent, namely water-soluble acrylonitrile polymer NP-10, are added to the underflow of the hydro separator and the treated pulp from this is fed into the flotation cells of the rich foaming stage. The lye in the sludge discharged behind the hydro separator is recovered and returned to the process cycle.

The conditioned pulp, on the other hand, is subjected to an initial pre-expander flotation subjected to a modified turbo-flotation machine in which practically all buoyant sylvin components contained in the turbidity of the gait, which the Outlets train, which is led as overflow, are separated.

The buoyant sylvine fractions recovered represent the concentrate of the pre-expander stage (pre-expander concentrate), which is then applied to cloth sieves with a mesh size of 0.60 mm in order to remove the coarsest fractions (i.e. particles with a grain size of over 0.60 mm) possibly do not respond to the subsequent flotation in the rich frother stage. The coarsest fractions obtained in this way (as sieve residue) are dewatered in the usual way and give the desired sylvine content. The recovered lye, which is saturated with the constituents of the sylvinite salt, is returned to the cycle and, with the subsequent amounts of sylvinite salt, again forms a cloud. The other part (passage through the sieve) of the pre-expander concentrate is then passed into the flotation cells of the rich frother stage, which are similar to the cells used in the pre-expander stage. At this point, the fine pulp coming from the hydroseparator and the concentrate of the coarser pulp are mixed with one another and further quantities of gangue from this mixture due to the action of those collectors and foam-regulating reagents that are still present in the concentrate of the coarser pulp after the pre-expander stage, removed. The Sylvin concentrate obtained in this process stage is then subjected to a third flotation process, known as the post-foaming stage, in order to remove further quantities of residual gangue. The secondary rock separated here and in the Reichschäumerstufe is fed to the outflows. The sylvine fractions obtained in the post-foaming stage are then dewatered in the usual way and represent the desired sylvine fractions. Table II below lists the separation products obtained by flotation of the aforementioned samples. The designations a) to d) each correspond to the samples for which the additional amounts of flotation reagents were specified under the same designations in Table 1 above. Table II Sample Ki! O content in 1 / o K20 applications Task Kon-Departures in 1 / o centrate a) 25.24 58.60 0 '76 98.26 b) 21.88 58, 59 0.55 98.41 c) 21.66 58.45 0.46 98.65 d) 22.83 58.48 0.70 98.11 Example 2 Eight sylvinitroh salt samples according to Example 1 are washed, desludged, classified and conditioned in the manner described, but with the difference that the underflow of the hydroseparator consisting of fine sludge is mixed with the coarser sludge and conditioned together with it. The reagents used in the corresponding samples e) to 1) and the amounts added are listed in Table III below. Table IH MPG flotation test total Sample 750 NP-10 Amine MIBC No. 634 Oil NP-20 reagents added Reagents e) 150.0 5.50 129.9 25.0 20.0 331 f) 150.0 5.50 129.9 25.0 20.0 331 9) 152.9 6.07 131.2 25.0 20.9 332 h) 151.0 3.70 131.2 25.0 19.9 11.2 342 i) 150.4 5.50 134.3 25.0 22.2 337 i) 148.9 6.05 120.4 24.4 24.8 324 k) 141.5 6.84 133.8 20.8 23.2 3.85 330 1) 144.5 6.07 122.8 24.8 25.0 322 In contrast to example 1 , the regulating inhibitor reagent, namely the water-soluble acrylonitrile polymer NP-10 according to example 1, is added to the mixture of coarser and finer pulp during conditioning in an amount of 5 ... 6 g / t sylvinite mill discharge. The mixed and conditioned fine and coarse samples are fed in the manner described in Example 1 to a pre-foamer flotation stage, a screening, a rich foamer flotation stage and a post-foamer flotation stage. This gives the flotation separation products which are given in percentage values in Table IV below, in which the sample designations e) to 1), inclusive, correspond to samples e) to 1) of Table III above. Table IV K2O content in% K20 output Sample task con- exits in% centrate e) 23.03 58.35 1.27 96.59 f) 22.95 58.38 1.42 96.15 g) 21.17 58.31 1.51 95.34 h) 24.03 58.51 1.45 96.35 i) 23.01 58.31 1.30 96.50 j) 23.65 58.70 1.82 95.26 k) 24.32 58.80 2.19 94.52 1) 26.73 58.73 2.09 95.58 From the above examples, of which Example 1 describes the process according to the invention and Example 2 describes the process used so far, it can be seen that the process according to the invention achieves a significantly higher efficiency in the recovery of sylvine from sylvinite salts, with a correspondingly lower consumption of Conditioning agents is connected. This saves material in an area where costs are crucial and the amounts of substance used and treated are very large.

Claims (2)

Claims: 1. A method for flotation of sylvine from clay-like constituents containing crude potash salts, in which the crushed crude salt is preclassified into two grain fractions and, after conditioning at least one fraction, is given up in a multi-stage, preferably two-stage flotation, characterized in that only the fraction of larger grain size is conditioned and only this one pre-flotation stage is given, whereas the fraction of smaller grain size together with the concentrate of the pre-flotation stage is given directly to a post-flotation stage. 2. The method according to claim 1, characterized in that the concentrate obtained in the pre-flotation stage is separated by an intermediate classification into fractions of coarse or fine particles, the coarse fraction obtained as the end product and the fine fraction together with the smaller fraction coming from the pre-classification Grain size is subjected to post-flotation. 3. The method according to any one of claims 1 and 2, characterized in that the crushed crude salt is mixed with a saturated alkali before conditioning and that the mixture is separated into fractions of large and small grain size. 4. The method according to any one of claims 1 to 3, characterized in that a sludge-preventing reagent is added to the small particle size fraction obtained by the pre-classification before it is subjected to post-flotation d. 5. The method according to any one of claims 1 to 4, characterized in that a cationic collector is preferably used for conditioning. Publications considered: German Auslegeschrift No. 1 122 013.