Abstract: In the manufacture of phosphoric acid from ore, the typical ore comprises minerals containing phosphorus and calcium along with varied amounts of other elements. Certain ores have substantial iron content which needs to be removed in order to produce quality phosphoric acid product. An improved method and associated chemical processing plant are disclosed for removing this iron. The method involves both reducing and adding oxalic acid to wet process phosphoric acid produced using an otherwise conventional manufacturing process. Iron oxalate precipitate is created which can then conveniently be separated therefrom.

Abstract: An improved riser system which comprises a connector for connecting conduits and a mooring system for mooring the connector to the floor of a body of water. The connector may include a pivoting device. The improved riser system also comprises a buoy system for supporting the connector. The buoy system is configured to provide a fixed buoyancy for the connector, the mooring system and at least a portion of the conduits and for providing variable buoyancy for placement of the connector at a predetermined water depth. The improved riser system may also include a flexible conduit made of titanium.

Abstract: A process for recovering phosphate values from phosphate ore containing phosphates and silica in which scrubbed and screened ore is subjected to a flotation process which floats finer silica particles but not heavier silica particles, and which does not tend to float phosphates, and removing the floated material thereby forming a concentrate while discarding silica fines. The concentrate is next screened to remove components of the ore which are of sizes greater than the sizes of silica particles which will be removed by said flotation, and removing from the process finer particles which are passed by the screen and predominately contain phosphates because the finer silica particles had previously been floated off, and then comminuting the material retained on said screen and reintroducing it to the process.