Process and plant for the production of potassium chloride from carnallite

Abstract

The application provides a process and equipment for producing potassium chloride by using carnallite as raw material. The process of the application comprises the following steps: crushing, washing, grinding, crystallization and positive flotation. Through optimization of process parameters and process flow, the application realizes the industrial continuous production of potassium chloride from carnallite on a scale of million tons, and the production efficiency is high, and the quality of the potassium chloride product, such as purity, whiteness and crystal particle size, is obviously improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of mineral extraction, and particularly relates to a process and equipment for producing potassium chloride with carnallite as raw material. BACKGROUND

[0002] Potassium chloride is an essential raw material for producing agricultural compound fertilizer, and is also an important raw material for chemical industry, metallurgy, medicine, food industry and the like. Raw materials for producing potassium chloride mainly include sylvine and carnallite. Carnallite has a chemical composition of KCl·MgCl2·6H2O, and is relatively abundant in resources, but the potassium content is usually lower than that of sylvine, and the processing energy consumption is higher, so the proportion in the production of potassium chloride is not large at present.

[0003] Common methods for producing potassium chloride from carnallite include positive flotation method, reverse flotation-cold crystallization method, controlled speed crystallization method, cold decomposition hot melt crystallization method, cold decomposition crystallization method, cold crystallization-positive flotation method, etc., among which the reverse flotation-cold crystallization method is the most commonly used process for producing potassium chloride from carnallite at home and abroad. The cold crystallization-positive flotation process is a new technology developed in recent years, which utilizes the control of the supersaturation of the carnallite decomposition system to achieve the purpose of growing potassium chloride crystal particles at normal temperature. However, the current cold crystallization-positive flotation process still has problems such as poor crystallization effect, low recovery rate of potassium chloride, and low purity of the obtained potassium chloride product. SUMMARY

[0004] The purpose of the present application is to provide a cold crystallization-positive flotation process and equipment for producing potassium chloride from carnallite, which can improve the crystallization effect, increase the recovery rate of potassium chloride, and increase the purity of the obtained potassium chloride product.

[0005] Therefore, in one aspect of the present application, a process for producing potassium chloride from carnallite is provided, comprising the following steps:

[0006] Crushing: crushing the mined carnallite to a particle size of less than or equal to 20 mm;

[0007] Washing: washing the crushed carnallite from the crushing step with system mother liquor to remove soil;

[0008] Grinding: grinding the carnallite from the washing step to a particle size of less than 1 mm;

[0009] Crystallization: mixing and conveying the carnallite particles from the grinding step with system mother liquor and make-up water into a crystallization unit at a mass ratio of 1:4-6.5:0.2-0.35, preferably 1:4-6:0.25-0.35, to perform crystallization, to produce a crystallizer bottom stream containing potassium chloride crystals;

[0010] Positive flotation: the crystallizer underflow from the crystallization step is fed to a positive flotation unit, a positive flotation reagent is added, potassium chloride froth is floated, the potassium chloride froth is filtered to obtain a crude potassium filter cake, the crude potassium is further purified, preferably by water washing, to obtain a refined potassium.

[0011] In one embodiment of the present application, the process of the present application is carried out at room temperature.

[0012] In one embodiment of the present application, the washing step comprises the following sub-steps:

[0013] Filter washing sub-step, wherein the broken-down carnallite from the breaking step is washed with the recycled mother liquor from the filter desliming sub-step, the particles having a size greater than or equal to 1 mm are separated and sent to the grinding step; and the remaining part is sent to the filter thickening sub-step;

[0014] Filter thickening sub-step, wherein the material from the filter washing sub-step is passed through a solid-liquid separation device, preferably a thickener, to separate the particles having a size less than 1 mm, which are directly sent to the crystallization step, and to send the remaining part to the filter desliming sub-step;

[0015] Filter desliming sub-step, wherein the earth from the mother liquor is removed by filtration; the filtered mother liquor is recycled to the filter washing sub-step, while the filter desliming sub-step is supplemented with system mother liquor, if necessary.

[0016] In one embodiment of the present application, in the filter washing sub-unit, the amount of carnallite and recycled mother liquor is adjusted according to the earth content in the raw ore, while washing and removing the earth from the raw ore, the liquid-solid ratio is as low as possible.

[0017] In one embodiment of the present application, the grinding step is preferably carried out using a rod mill.

[0018] In one embodiment of the present application, the crystallization unit in the crystallization step comprises a decomposition crystallizer, a solid-liquid separation device, a fine crystal tank and a recrystallizer.

[0019] In the decomposition crystallizer, the carnallite particles from the grinding step are contacted with the system mother liquor and make-up water in a mass ratio of 1:4-6.5:0.2-0.35, preferably 1:4-6:0.25-0.35, to crystallize potassium chloride. The formed potassium chloride crystals are discharged with the underflow of the decomposition crystallizer. At the same time, the overflow of the decomposition crystallizer is fed to the solid-liquid separation device.

[0020] In the solid-liquid separation device, solid-liquid separation is carried out to form an underflow containing potassium chloride crystals and an overflow. The underflow of the solid-liquid separation device is fed to the recrystallizer for further crystallization, while the overflow of the solid-liquid separation device is recycled to the fine crystal tank. Preferably, the solid-liquid separation device is a thickener.

[0021] In the fine-grain tank, overflow from the solid-liquid separation device is mixed with make-up water, and the mixed liquid is circulated to the decomposition crystallizer. The overflow from the solid-liquid separation device contains finer potassium chloride grains, and after the overflow enters the fine-grain tank, the make-up water (fresh water) dissolves the potassium chloride crystals in the overflow to form an unsaturated solution of potassium chloride, which enters the decomposition crystallizer to dissolve the ground ore that enters therein.

[0022] In the recrystallizer, the grains in the underflow from the solid-liquid separation device continue to grow. The potassium chloride grains that grow in the recrystallizer are discharged with the underflow of the recrystallizer. By using the recrystallizer, the fine crystals in the overflow of the decomposition crystallizer are further grown, thus improving the efficiency of extracting potassium chloride. The underflow of the decomposition crystallizer and the underflow of the recrystallizer are collectively referred to as crystallizer underflow, and the crystallizer underflow is transported to the direct flotation step. In an embodiment of the present application, the proportion of potassium chloride grains with a diameter greater than 0.15 mm in the underflow of the decomposition crystallizer and the underflow of the recrystallizer is more than 70%.

[0023] Since the crystallizer underflow contains a certain amount of mother liquor, after the underflow of the decomposition crystallizer and the underflow of the recrystallizer are discharged, the amount of liquid in the decomposition crystallizer and the recrystallizer decreases. For this reason, the decomposition crystallizer and the recrystallizer can be supplemented with liquid by the system mother liquor.

[0024] In an embodiment of the present application, the direct flotation unit includes a conditioning tank, a flotation machine, and a coarse potassium filter.

[0025] In the conditioning tank, the crystallizer underflow is mixed with the system mother liquor and sent to the flotation machine.

[0026] In the flotation machine, direct flotation reagents are added, and potassium chloride froth is floated.

[0027] In the coarse potassium filter, the potassium chloride froth is filtered to obtain a coarse potassium filter cake and a system mother liquor; preferably, the filtration is belt filtration.

[0028] In an embodiment of the present application, the underflow from the flotation machine is filtered to obtain a system mother liquor and tail salt; preferably, the filtration is belt filtration.

[0029] In an embodiment of the present application, the direct flotation reagents used in the direct flotation step can be fatty amine cationic collectors, such as dodecylamine, octadecylamine; or alkyl sulfonate anionic collectors.

[0030] In an embodiment of the present application, at least a part of the system mother liquor from the coarse potassium filter is circulated to the decomposition crystallizer, and another part is circulated to the direct flotation unit, wherein the system mother liquor circulated to the direct flotation unit accounts for more than 70% of the system mother liquor from the coarse potassium filter.

[0031] In another aspect of the present application, there is provided an apparatus for carrying out the process of the present application, said apparatus comprising the following units: a crushing unit; a washing unit; a grinding unit; a crystallization unit; a direct flotation unit.

[0032] In one embodiment of the present application, the washing unit comprises the following sub-units: a filtration washing sub-unit; a filtration thickening sub-unit; a filtration desliming sub-unit.

[0033] In the present application, the term "system mother liquor" refers to the liquid discharged from the system, such as the liquid separated from the coarse potassium filtration process, the liquid separated from the tail salt filtration process, and the historically retained liquid discharged from the system. The "system mother liquor" is a saturated solution of magnesium chloride.

[0034] The present application realizes the industrial continuous production of potassium chloride from carnallite on a million-ton scale by optimizing the process parameters and process flow, has high production efficiency, and significantly improves the quality of potassium chloride product such as purity, whiteness, and crystal particle size. In addition, by combining direct flotation and reverse flotation, the washing step after flotation is reduced on the basis of maintaining high purity, the operation steps are simplified, energy consumption is reduced, and the defect of reducing the size of potassium chloride crystal particles caused by washing operation is avoided. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a flow chart of the process according to one embodiment of the present application.

[0036] Figure 2 is a structural schematic diagram of a decomposition crystallizer according to the present application. DETAILED DESCRIPTION

[0037] Embodiments of the present application will be described in detail below with reference to the accompanying drawings. Those skilled in the art will understand that the following description is merely for the purpose of specifically illustrating the technical solutions of the present application, and is not intended to limit the scope of the present application in any way.

[0038] Figure 1 is a flow chart of the process according to one embodiment of the present application. The process generally includes a crushing step, a washing step, a grinding step, a crystallization step, and a direct flotation step. The process is carried out at room temperature.

[0039] In the crushing step, the mined carnallite is crushed to a particle size of less than or equal to 20 mm, such as less than or equal to 20 mm, less than or equal to 15 mm, less than or equal to 10 mm, or less than or equal to 5 mm.

[0040] In the washing step, the crushed carnallite from the crushing step is washed with system mother liquor to remove the clay. The washing step comprises the following sub-steps: filter washing, filter thickening and filter desliming. In the filter washing sub-step, the crushed carnallite from the crushing step is washed with the recycled mother liquor from the filter desliming sub-step to separate the particles having a size greater than or equal to 1 mm, which are sent to the grinding step, and the remaining part, which is sent to the filter thickening sub-step. In the filter thickening sub-step, the material from the filter washing sub-step is passed through a solid-liquid separation device, preferably a thickener, to separate the particles having a size less than 1 mm, which are directly sent to the crystallization step, and the remaining part, which is sent to the filter desliming sub-step. In the filter desliming sub-step, the clay is removed from the mother liquor by filtration. The filtered mother liquor is recycled to the filter washing sub-step. If necessary, the filter washing sub-step is supplemented with system mother liquor. In the filter washing sub-unit, the amount of carnallite and recycled mother liquor is adjusted according to the clay content of the raw ore, in order to wash away the clay from the raw ore while minimizing the liquid-solid ratio.

[0041] In the grinding step, the carnallite particles having a size greater than or equal to 1 mm from the washing step are ground to a size less than 1 mm. In one embodiment of the application, the grinding step is preferably carried out using a rod mill.

[0042] In the crystallization step, the carnallite particles from the grinding step are mixed with system mother liquor and a certain amount of make-up water and fed to a crystallization unit, where crystallization takes place, resulting in a crystallizer underflow comprising potassium chloride crystals, which is fed to a positive flotation unit for positive flotation.

[0043] The crystallization unit can comprise a decomposition crystallizer, a solid-liquid separation device, a fine crystal tank and a recrystallizer.

[0044] In the decomposition crystallizer, the carnallite particles from the grinding step are contacted with system mother liquor and make-up water in a mass ratio of 1 :4-6.5:0.2-0.35; preferably 1 :4-6:0.25-0.35, on the one hand to decompose the ore and on the other hand to crystallize the potassium chloride under the action of magnesium chloride. The formed potassium chloride crystals are discharged with the underflow of the decomposition crystallizer. At the same time, the overflow of the decomposition crystallizer is fed to a solid-liquid separation device.

[0045] In the solid-liquid separation device, solid-liquid separation takes place, resulting in an underflow comprising potassium chloride crystals and an overflow. The underflow of the solid-liquid separation device is fed to a recrystallizer for further crystallization, while the overflow of the solid-liquid separation device is recycled to a fine crystal tank. Preferably, the solid-liquid separation device is a thickener.

[0046] In the fine-grain tank, overflow from the solid-liquid separation device is mixed with make-up water, and the mixed liquid is circulated back to the decomposition crystallizer. The overflow from the solid-liquid separation device contains finer potassium chloride grains, and after the overflow enters the fine-grain tank, the make-up water (fresh water) dissolves the potassium chloride crystals in the overflow to form an unsaturated solution of potassium chloride, which enters the decomposition crystallizer for dissolving the ground ore that enters therein.

[0047] In the recrystallizer, the grains in the underflow from the solid-liquid separation device continue to grow. The potassium chloride grains that grow in the recrystallizer are discharged with the underflow of the recrystallizer. By using the recrystallizer, the fine crystals in the overflow of the decomposition crystallizer are further grown, thus improving the efficiency of extracting potassium chloride. In this context, the underflow of the decomposition crystallizer and the underflow of the recrystallizer are collectively referred to as the crystallizer underflow, and the potassium chloride grains with a diameter greater than 0.15 mm account for more than 70% of the crystallizer underflow. The crystallizer underflow is delivered to the direct flotation step. Figure 1

[0048] Since the crystallizer underflow contains a certain amount of mother liquor, after the underflow of the decomposition crystallizer and the underflow of the recrystallizer are discharged, the amount of liquid in the decomposition crystallizer and the recrystallizer decreases. For this reason, the decomposition crystallizer and the recrystallizer can be supplemented with liquid by the system mother liquor, while fully utilizing the system mother liquor and avoiding the use of fresh water to cause "crystal explosion" in the crystallization process, which affects the growth of crystal nuclei and leads to the production efficiency of potassium chloride. "Crystal explosion" refers to the process of adding fresh water to separate the crystals into more fine grains, which causes the number of crystal nuclei to rapidly increase, which is not conducive to the further growth of the crystal nuclei.

[0049] In the direct flotation step, the crystallizer underflow from the crystallization step is delivered to the direct flotation unit, a direct flotation reagent is added, and potassium chloride froth is floated out, which is filtered to obtain a crude potassium filter cake.

[0050] The direct flotation unit can include a slurry tank, a flotation machine, and a crude potassium filter. In the slurry tank, the crystallizer underflow is mixed with the system mother liquor and sent to the flotation machine. In the flotation machine, a direct flotation reagent is added, and potassium chloride froth is floated out. In the crude potassium filter, the potassium chloride froth is filtered, and the crude potassium filter is preferably a belt filter. The crude potassium filter cake is obtained by the crude potassium filter, and the filtrate is used as the system mother liquor. The underflow from the flotation machine is filtered to obtain the system mother liquor and tail salt; preferably, the filtration is belt filtration.

[0051] In the direct flotation step, the direct flotation reagent used can be a fatty amine cationic collector, such as dodecylamine, octadecylamine; or an alkyl sulfonate anionic collector.

[0052] ​In the positive flotation step, at least a portion of the system mother liquor from the crude potassium filter is recycled to the decomposer crystallizer, and another portion is recycled to the positive flotation unit, wherein the system mother liquor recycled to the positive flotation unit accounts for more than 70% of the system mother liquor from the crude potassium filter.

[0053] The crude potassium filter cake from the positive flotation unit is further purified by washing with water to obtain refined potassium, which is then dried and packaged to obtain potassium chloride product.

[0054] Figure 2 A schematic diagram of the decomposition crystallizer according to the present invention is shown.

[0055] Carnallite particles from the grinding step enter the decomposition crystallizer, where they come into contact with the system mother liquor and makeup water. The decomposition crystallizer includes a central cylinder; a mixing device within the central cylinder; a coarse particle settling zone below the central cylinder; a guide cylinder coaxial with the central cylinder and with a larger diameter; a fine particle settling zone below the guide cylinder; a fine crystallization zone outside the guide cylinder; an underflow outlet at the bottom of the decomposition crystallizer; and a crystallizer overflow outlet at the top of the decomposition crystallizer. The axial and radial forces generated by the mixing device are controlled so that over 70% of the potassium chloride crystals settling to the bottom of the decomposition crystallizer have a diameter greater than 0.15 mm. Simultaneously, fine particles flow with the liquid through the central cylinder, guide cylinder, fine particle settling zone, and fine crystallization zone. During this process, the fine particles continue to grow and settle to the bottom of the decomposition crystallizer. The formed potassium chloride crystals are discharged with the underflow from the decomposition crystallizer. Simultaneously, the overflow from the decomposition crystallizer is transported to a solid-liquid separation device.

[0056] The present invention will be further described below through specific embodiments. It should be understood that these embodiments are merely exemplary and do not constitute any limitation on the scope of protection of the present invention. Unless otherwise specified, the reagents, materials and instruments used in the following embodiments are commercially available.

[0057] Unless otherwise specified, all percentages used in this application are weight percentages.

[0058] Example 1

[0059] use Figure 1 The process shown is for processing carnallite from Laos, which contains approximately 16 wt% potassium chloride, approximately 44 wt% sodium chloride, and approximately 19 wt% magnesium chloride.

[0060] One ton of carnallite is crushed to a particle size of less than or equal to 5 mm in the crushing unit.

[0061] The crushed carnallite is washed in a washing unit comprising a filter washing, a filter thickening and a filter desliming. The solid-liquid weight ratio in the washing unit is about 1:1. The particles having a particle size of greater than or equal to 1 mm separated in the washing unit are sent to a grinding unit, and the particles having a particle size of less than 1 mm are directly sent to a recrystallizer in a crystallization unit.

[0062] In the grinding unit, the carnallite particles having a particle size of greater than or equal to 1 mm from the washing unit are ground to a particle size of less than 1 mm by a rod mill.

[0063] In the crystallization unit comprising a decomposition crystallizer, a thickener, a fine crystal tank and a recrystallizer as shown in Figure 2 The carnallite particles from the grinding step are contacted with 4.8 tons of system mother liquor and 0.28 tons of make-up water in the crystallization unit, so that the carnallite is crystallized. The potassium chloride crystals having a diameter greater than 0.15 mm in the obtained crystallizer underflow account for more than 70%. The crystallizer underflow is transported to a direct flotation unit.

[0064] In the direct flotation unit comprising a conditioning tank, a flotation machine and a coarse potassium filter, flotation is carried out with octadecylamine as a flotation agent, and potassium chloride froth is floated. The scraped potassium chloride froth is subjected to coarse potassium belt filtration to obtain a coarse potassium filter cake, and the obtained filtrate is used as system mother liquor. The underflow from the flotation machine is subjected to tail salt belt filtration to obtain system mother liquor and tail salt. 80% of the system mother liquor obtained in the direct flotation unit is recycled back to the direct flotation unit, and the other 20% is recycled back to the crystallization unit.

[0065] The obtained coarse potassium is washed to further purify, to obtain fine potassium. The fine potassium is dried to obtain 130.9 kg of potassium chloride, with a yield of 81.8%, a purity of 97.5%, and the particles having a particle size of 0.15 mm or more accounting for 70% by weight. A total of 0.4 tons of tail liquid is generated in the whole process.

[0066] Comparative Example 1

[0067] The other conditions are the same as in Example 1, except that all the system mother liquor obtained in the direct flotation unit is recycled back to the crystallization unit. The yield of potassium chloride is 65%, and the purity is 96%.

[0068] Comparative Example 2

[0069] The other conditions are the same as in Example 1, except that the recrystallizer is not included in the crystallization unit. The yield of potassium chloride is 77.6%, and the purity is 96%.

[0070] The preferred embodiments of the application disclosed above are only to facilitate the elucidation of the application. The preferred embodiments do not describe all the details of the application and limit the application to the specific embodiments described. Obviously, many modifications and variations can be made in light of the teachings above. The description is chosen and described in order to best explain the principles of the application and its practical application to thereby enable others skilled in the art to best utilize the application and get the best results from the application. The application is only limited by the claims and their full scope and equivalents.

Claims

1. A process for producing potassium chloride from carnallite, comprising the following steps: broken: The mined carnallite is crushed to a particle size of 20 mm or less; washing; Grinding: Grind the carnallite from the washing step to a particle size of less than 1 mm; Crystallization: Carnallite particles from the grinding step are mixed with the system mother liquor and makeup water at a mass ratio of 1:4~6.5:0.2~0.35 and transported to the crystallization unit for crystallization to produce a crystallizer underflow containing potassium chloride crystals; Direct flotation: The underflow from the crystallizer in the crystallization step is fed to the direct flotation unit, direct flotation reagents are added, potassium chloride foam is floated out, and the potassium chloride foam is filtered to obtain crude potassium filter cake. The crystallization unit includes a decomposition crystallizer, and at least a portion of the system mother liquor from the positive flotation step is recycled to the decomposition crystallizer, and another portion is recycled to the positive flotation unit, wherein the system mother liquor recycled to the positive flotation unit accounts for more than 70% of the system mother liquor from the positive flotation step; The washing process includes the following sub-steps: The filtration and washing sub-step involves washing the crushed carnallite from the crushing step with the circulating mother liquor from the filtration and desliming sub-step to separate particles with a diameter greater than or equal to 1 mm, which are then sent to the grinding step; the remaining portion is sent to the filtration and thickening sub-step. The filtration and thickening sub-step involves passing the material from the filtration and washing sub-step through a solid-liquid separation device to separate particles with a diameter of less than 1 mm, which are then directly sent to the crystallization step, while the remainder is sent to the filtration and desliming sub-step. The filtration and desludge removal step involves removing mud from the mother liquor through filtration; the mother liquor is then recycled to the filtration and washing step. The crystallization unit includes a decomposition crystallizer, a solid-liquid separation device, a fine crystal tank, and a recrystallizer, wherein: In the decomposition crystallizer, carnallite particles from the grinding step are brought into contact with the system mother liquor and makeup water at a mass ratio of 1:4~6.5:0.2~0.35, causing potassium chloride to crystallize out. The formed potassium chloride crystals are discharged with the underflow of the decomposition crystallizer, while the overflow of the decomposition crystallizer is transported to the solid-liquid separation device. In the solid-liquid separation device, after solid-liquid separation, a bottom flow and an overflow containing potassium chloride crystals are formed. The bottom flow of the solid-liquid separation device is transported to the recrystallizer for further crystallization, while the overflow of the solid-liquid separation device is circulated to the fine crystal tank. In the fine crystal tank, the overflow from the solid-liquid separation unit is mixed with the makeup water, and the mixed liquid is circulated to the decomposition crystallizer; In the recrystallizer, the grains from the underflow of the solid-liquid separation unit continue to grow. The potassium chloride grains that have grown in the recrystallizer are discharged with the underflow of the recrystallizer. The underflow of the decomposition crystallizer and the underflow of the recrystallizer are collectively referred to as the crystallizer underflow.

2. The process as described in claim 1, wherein the process is performed outdoors at room temperature.

3. The process as described in claim 1 or 2, wherein in the crystallization step, the mass ratio of carnallite particles from the grinding step to the system mother liquor and make-up water is 1:4~6:0.25~0.

35.

4. The process as described in claim 1 or 2, wherein in the filtration and desliming step, the system mother liquor is used to supplement the filtration and desliming step with liquid.

5. The process as described in claim 4, wherein in the filtration and washing sub-step, the amounts of carnallite and circulating mother liquor are adjusted according to the clay content in the raw ore, so as to reduce the liquid-solid ratio as much as possible while washing away the clay in the raw ore.

6. The process as described in claim 1 or 2, wherein the grinding step is performed using a rod mill.

7. The process of claim 1 or 2, wherein the crude potassium is further purified by washing with water after the positive flotation step to obtain refined potassium.

8. The process of claim 1 or 2, wherein the decomposition crystallizer comprises: Central tube; The mixing device inside the central cylinder; The coarse particle settling zone below the central cylinder; A guide tube that is coaxial with the central tube and has a larger diameter than the central tube; Fine particle settling zone below the guide tube; Fine-grained crystallization zone on the outer side of the guide tube; The bottom outlet is located at the bottom of the decomposition crystallizer; and the crystallizer overflow outlet is located at the top of the decomposition crystallizer, wherein the axial and radial forces generated by the mixing device are controlled so that more than 70% of the potassium chloride crystals that settle to the bottom of the decomposition crystallizer have a diameter greater than 0.15 mm.

9. The process of claim 1 or 2, wherein the positive flotation unit comprises a slurry conditioning tank, a flotation machine, and a coarse potassium filter, wherein: In the mixing tank, the crystallizer underflow is mixed with the system mother liquor and sent to the flotation machine; Add positive flotation reagent to the flotation machine to float potassium chloride foam; In the coarse potassium filter, potassium chloride foam is filtered to obtain coarse potassium filter cake and system mother liquor.

10. The process of claim 1 or 2, wherein the positive flotation reagent used in the positive flotation step is selected from aliphatic amine cationic collectors; or alkyl sulfonate anionic collectors.

11. The process of claim 10, wherein the aliphatic amine cationic collector is selected from dodecylamine and octadecylamine.

Images