We studied the processes of desulfurization of phosphoric acid obtained by wet process from washed and roasted concentrate and subsequent purification of acid from bivalent and trivalent metals and fluorine via partial ammonization (at pH of 2 to 4). Purified ammoniated slurry containing 16.96% P2O5, 8.06% N, 0.09% CaO, 0.58% MgO, 0.004% Fe2O3, 0.031% A12O3, 0.78% SO3 and 0.52% F was fabricated by the removal of precipitates at the stages of desulfurization and partial ammonization. The rheological properties of ammoniated slurry with 40% moisture were studied. When the temperature is increased from 40 to 800C, both the density and viscosity decrease from 1.395 to 1.365 g cm–3 and from 80.8 to 48.7 cP, respectively. Ammoniated suspension with pH of 5.5 and 8.5 was applied to prepare mono- and diammonium phosphates with the ratio P2O5:N of 52:14 and 48:18, respectively. The sludge obtained after desulfurization and ammonization processes can be used as a slow-release fertilizer.
Enterprises producing phosphate fertilizers encounter a very serious problem associated with phosphogypsum piled up in huge amounts. To date, about 7 billion tons of phosphogypsum have been piled up all over the world with an average release of 180 million tons, and its utilization remains challenge. The process of phosphogypsum conversion of Kyzylkum phosphorite from JSC “Ammophos-Maxam” with soda ash of UE “Kungradsky soda plant” was studied in the work. The study was carried out in a wide range of concentration (10-20%) and stoichiometric norm (100-110%) of Na2CO3 at a temperature of 80°C and a time of 30 minutes. It was revealed that an increase in the concentration and stoichiometric norm of Na2CO3 leads to an increase in the degree of conversion of phosphogypsum into CaCO3 and Na2SO4 up to 97.07%. The following is optimal: the concentration of Na2CO3 is 20% and the stoichiometric norm is 105%, at which the degree of conversion is ⁓96%. As a result, the target product Na2SO4 was obtained with a purity of 94% and calcium carbonate - 96.25%. This solution allows producers of phosphate fertilizers to recycle phosphogypsum into products with high demand.
Complex, nitrogen-phosphate fertilisers are applied before seeding, with seeding and extra nutrition, while single phosphoric ones are the most effective under autumn ploughing. In that case, enriched superphosphate, more concentrated than single superphosphate, was obtained using phosphoric acid gypsum slurry semiproduct produced by the interaction of thermo concentrate with sulphuric acid and recycled phosphoric acid in accordingly dihydrate operation (60-80°C). However, the mix of sulphuric and phosphoric acids was not used those are usually applied in conventional ways for enriched superphosphate production. Phosphate raw material (PRM) is dosed into phosphoric acid gypsum slurry (PAGS) upon weight ratio of PAGS: PRM equal from 100: 15 to 100: 40 that provides a condition for slurry fluidity. Interaction of the components was
Original Research Article
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