The manufacture and evaluation of granular potassium chloride fertilizers

Abstract

A finely divided red potassium chloride (KCl) (particle size distribution: 79% <0.5 mm, 20% 1-0.5 mm and 1% 1–2 mm) was granulated by adding eight readily available and relatively inexpensive binders using a rotating drum in the laboratory. The binders used were: urea, pulp and paper waste liquor containing lignosulphonate, urea + pulp and paper waste liquor, Borrebond powder (a commercial product containing lignosulphonate), urea + formaldehyde, ammonium sulphate, ammonium sulphate + pulp and paper waste liquor and a waste liquor containing ammonium sulphate from a Ferritin production plant. Of these, except for urea and urea + pulp and paper waste liquor which produced KCl granules having low critical relative humidity at 30°C (CRH) (<55%) and Borrebond which produced KCl granules of low crushing strength (1.1 kg for 2–3 mm granules) the other five binders produced granules with good size distributions, high crushing strengths (2.0–2.5 kg for 2–3 mm granules), CRH (65–70%) and suitable nutrient contents (K, 46–50%, Cl, 42–47%). These values are very close to those of the standard chipped KCl (crushing strength, 2.5 kg; CRH, 65–70%; K, 50%; Cl, 47%).