Dissolution reaction of potash fertilizer with moisture

This paper presents the solubility analysis of potash fertilizer at thermod ynamic equilibrium. The Pitzer equations applicable to a KCl-NaCl-MgCl2-H2O system are developed to describe the interaction between the aqueous ions. The equilibrium constant method is used to analyze the dissolution reactio n equilibrium. A critical relative humidity around 52% is obtained which ch aracterizes the moisture-potash interaction mechanism as adsorption or cond ensation. Three distinct stages of dissolution exist for typical potash pro ducts that depend on moisture and temperature, with surface brine saturated with three salts (sylvite, halite and carnallite), two salts (sylvite and halite), and single salt (sylvite), respectively. At high relative humiditi es (i.e., RH > 75%), dissolution depends on the temperature, and moisture c ontent may exceed 3% and dissolution of sylvite can increase without a limi t.