Potash, fertilizer-grade production

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. 

About 4%-5% of potash production is used in industrial applications. The industrial potash (chemical grade) has a different purity from fertilizer-grade potash. The composition of chemical-grade potash is given in Table 15.13 [51. 

Potassium chloride [7447-40-7] or muriate of potash (MOP) as it is known in the fertilizer industry (at about 97% purity), is the world s most commonly used potash (5). Chemical-grade potassium chloride (99.9%) is the basis for manufactured production of most potassium salts (10). 

Commercial grades of AN include solutions that contain about 83% AN and solid products. Both grades are used for direct fertilizer applications, or they are blended with other materials to form mixed solid and liquid fertilizers. High density, prilled AN is usually used for direct applications while other solid AN is mixed with phosphate and potash for multi-nutrient fertilizers. Solid AN has lost market share to urea because it has a lower nitrogen content (33-35% for AN vs. 45-46% for urea), plus it costs more per ton. In addition to direct application, AN solutions are mixed with urea to make nitrogen solution fertilizers240. 

Potassium chloride as a component in fertilizers is specified in terms of its K2O equivalent. On this basis, 100% pure potassium chloride is equated to 63.18% K2O equivalent. The approximately 96% pure potassium chloride product of the flotation separation is thus equivalent to 60.7% K2O (see Chap. 9). Chemical grades correspond to the once-crystallized, soluble product of about 99.5% KCl, and 99.95% KCl, which is the Refined, twice crystallized material. The price differential, 60-62.4% K2O equivalent at 108-112 US /tonne, and 99.95% KCl at 115-137 US /tonne (1995 prices [30]) is sufficient to cover the cost of the additional processing for Chemical grade potash. 

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