Phosphogypsum Disposal-The Pros & Cons of Wet Versus Dry Stacking

There are a number of factors that an operator should consider before pursuing wet or dry stacking of the phosphogypsum by-product from a phosphoric acid plant. In addition to process considerations, important factors include the climatologic regime, water balance considerations, hydrogeology, topography, capital cost, operating cost (and maintenance), closure costs (and handling of drainable pore water), availability (or scarcity) of a fresh water source, distance from the plant to the disposal site (and viability of dry versus wet transport methods), P2O5 recovery, impacts on the environment (from leakage, dusting, accidental spills, etc.) and applicable regulations.A review of dry/wet transport methods and dry/wet disposal methods is presented using illustrative examples from various countries worldwide, with particular emphasis on the advantages and disadvantages of wet and dry stacking in the various environments. In most instances, wet stacking is preferred over dry stacking based on economic and maintenance considerations.The author wishes to acknowledge the invaluable contributions of his former colleague and mentor, the late Dr. Anwar E. Z. Wissa, who contributed since the early seventies to improving our understanding of this important topic.