Potash, flotation

Flotation. Tallow amines contain small amounts of short-chain compounds, eg, the octyl, lauryl, and myristyl (C ) groups. These amines usually produce enough froth for the flotation. Small quantities of specialized synthetic alcohols, eg, Dowfroth P, are frequentiy added to the flotation system to supplement the natural frothers. The quantities of the reagents used ia potash flotation plants are Hsted ia Table 5. 

Compared to the other flotation systems, the material is much coarser in potash flotation, due to a large liberalization size of the crystals. The rather small difference in density between the mineral salt and the brine makes it possible to float much larger particles in the brine system as compared to water systems. 

The potash contains clay minerals, often as slime. This clay represents a large surface area and adsorbs the alkylamine collector. This is detrimental to the potash flotation, and therefore several methods are used to dispose of the clay. Mechanical de-sliming using hydrocyclones and hydroseparators is common practice. Slime flotation is often used. In this, the clay minerals are separated in a pre-flotation step by using a polymer and a non-ionic surfactant, for example, polyacrylamide and ethoxylated fatty acid, respectively. An alternate way is to depress the clay minerals with polymers such as sodium carboxymethyl cellulose (CMC), potato starch and lignosulfonate. 

Another category of reagents that is commonly used is known as frothers. Frothers are used to aid the formation of, and stabilize, the flotation froth. Generally, these reagents are organic heteropolar compounds. Pine oil, a widely used frother, contains aromatic alcohols. A wide range of synthetic frothers is also available. A conventional frother, MIBC (methylisobutyl carbinol), is used in potash flotation as a modifier to inhibit the formation of excessive amine froth [98]. 

Modifiers or regulators constitute another class of flotation reagents that are used to control the process. In potash flotation, slimes depressants such as starch, guar gum, dextrine, and synthetic compounds are typically used [99[. 

Uses Emulsifier for agric. frother for potash flotation in strongly electrolytic salt flotation pulps... 

Sizing. In most flotation plants, flotation concentrates, after being dried, are sized into three fractions and each serves a specific agricultural market. The fractions are coarse-, standard-, and suspension-grades of muriate of potash. Typical screen analyses are presented in Table 6 other physical characteristics are summarized in Table 7. 

Large deposits of sylvinite (42.7% KCl, 56.6% NaCl) near Carlsbad, New Mexico, account for 85% of the potassium products produced in the U.S. The potassium chloride can be separated by either fractional crystallization or flotation. Potassium chloride is also obtained from the brines of Searles Lake, California. All these sources give potash (97% potassium chloride) with a 60% K2O equivalent for fertilizer use. A chemical-grade product can be obtained to a purity of 99.9% potassium chloride. Almost all potash produced is potassium chloride. Potash is used mainly as fertilizer (88%) with a small amount (12%) used in chemical manufacture. 

Halite (NaCl) can be selectively floated using n-alkyl carboxylates (collector), heavy metal ions (activator), and a non polar oil (additional collector). This yields a concentrated dispersion of the potash. Alternatively, the potash can be selectively floated from a saturated brine solution, using n-alkyl amine as the collectors, leaving the other salts behind. The flotation steps may involve a sequence of rougher, cleaner, and re-deaner stages. Either way the collected potash would be centrifuge de watered, dried, then sized by screening. The final potassium concentrate would probably be at least about 60%,... 

In contrast to conventional flotation, in which the desirable mineral is directly floated and collected from the produced froth, reverse (indirect) flotation aims to have the undesirable minerals preferentially floated and removed, leaving behind a slurry that has been concentrated in the desirable mineral. This method has been used for the purification of iron ore and the separation of salt from potash. The next section describes some other variations on conventional froth flotation. 

Promoters or collectors provide the substances to be separated with a water-repellent air-avid coating that will adhere to air bubbles. Typical collectors for flotation of metallic sulfides and native metals are dithiophosphates and xanthates. Fatty acids and their soaps, petroleum sulfonates, and sulfonated fatty acids are widely used as collectors in flotation of fluorspar, iron ore, phosphate rock, and others. Fuel oil and kerosene are used as collectors for coal, graphite, sulfur, and molybdenite. Cationic collectors such as fatty amines and amine salts are widely used for separation of quartz, potash, and silicate minerals. 

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