Phosphoric acid shipment

Economics. In contrast to NSP, the high nutrient content of TSP makes shipment of the finished product preferable to shipping of the raw materials. Plants, therefore, are located at or near the rock source. The phosphoric acid used, and the sulfuric acid required for its manufacture, usually are produced at the site of the TSP plant. As in the case of NSP, the cost of raw materials accounts for more than 90% of the total cost. Most of this is the cost of acid. 

The final product is drained off from the retort, cooled and stored in aluminium tanks in which, if necessary, it is stabilized with phosphoric acid, pyrophosphate and 8-hydroxyquinoline. The stability of hydrogen peroxide with a high percentage is very high. After being stored a year in aluminium tanks it loses hardly more than 0.5 to 1 per cent of active oxygen. In view of this, it is also suitable for shipment to tropical countries. 

Phosphoric add for shipment should be relatively free of sludge-forming solids, preferably less than 1%. To meet this requirement the acid usually must be clarified, as discussed previously in this chapter. The amount of sludge depends on the composition of the phosphate rock and the phosphoric acid production process and, in some cases, clarification is unnecessary. 

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