Phospho-gypsum is a by-product of the phosphoric acid industry and consists of 65-70 % gypsum, 25-30 % water and 5-10 % impurities, i.e. phosphoric acid and its salts, hydrofluoric acid and its compounds, R2O3 (Al2O3+ Fe2O3), quartz, apatite, alkali, organic matter, and others. The P2O5 and F impurities are found in three different forms in Phospho-gypsum compound: on the surface of gypsum crystals as water soluble compounds (H3PO4, Ca(H2PO4)2•H2O, H2SiF6), substituted in the lattice of gypsum crystals (effectively solid solutions of CaHPO4•2H2O, SrSO4 or Na2SiF6) and as insoluble compounds, i.e. apatite and quartz. These impurities, particularly hydrofluoric acid and its salts, contaminate an environment. Soluble phosphates {H3PO4 and Ca(H2PO4)2•H2O} and soluble fluorides had maximum influence on the fall of compressive strength of plaster. CaHPO4•2H2O had small influence, but with the present of Ca(OH)2 it had great influence on the plaster properties. The most impurities in Phospho-gypsum can be found in the particle size fractions above 160 and below 25 µm. There are more than few plants (those of Onoda in Japan, Giulinichemic GmbH , Knauf in Germany, etc.) where the impurities are eliminated by washing Phospho-gypsum with water or separating off coarse and very fine particles. Up to 4 m3 of water is necessary for 1 ton of Phospho-gypsum. The Phospho-gypsum mixtures are also eliminated by using a combined method when Phospho-gypsum is washed with a smaller amount of water, and the rest of the acid mixtures are neutralized by adding the following additives: Ca(OH)2, CaCO3, K2CO3, KOH, Portland cement, NH4OH, etc. The acid impurities are not fully eliminated from the Phospho-gypsum crystals. The insoluble phosphates {Ca3(PO4)2, Ca5(PO4)3OH} and fluorides (CaF2 andCaSiF6) did not influence the plaster properties. The objective of the work is to investigate the neutralization process of the acid impurities of dehydrate Phospho-gypsum into lime suspension. Market Survey Phosphoric acid production scenarios in India, there are 11 no. of phosphoric acid manufacturing units located in 7 States namely Andhra Pradesh, Gujarat, Kerala, Maharashtra, Orissa, Tamil Nadu and West Bengal. The total production of phosphoric acid is about 1.2 Million Tons during the year 2009-2010. The 3 Generation of Phospho-gypsum Phospho-gypsum is generated from filtration process in phosphoric acid plants where insoluble gypsum (and other material) are separated from the product i.e. phosphoric acid as efficiently as possible. Depending on the source of rock phosphate about 4.5 -5 Tons (dry basis) of Phospho-gypsum (by-product Phospho-gypsum) is generated per ton of phosphoric acid (as P2O5) recovered. The quality & quantity of Phospho-gypsum generation depends upon the quality of the phosphate rock, process route used to produce phosphoric acid, calcium sulphate generated either in di-hydrate (CaSO4.2H2O) or the hemi-hydrate (CaSO4.1/2 H2O) form. Phosphogypsum generation in the Country is about 11 Million Tons per annum (based on the assumption that 5 Tons of Phospho-gypsum generated per ton of phosphoric acid production). International practices of Phospho-gypsum management & handling Phosphogypsum contains three types of impurities that are considered to be potentially harmful such as residual acidity, fluorine compounds, trace elements including radioactivity.