Abstract: Alkali metal polyphosphates consisting substantially of hollow spheroidal particles with an apparent density of less than 350 g/l are made. To this end, an alkali metal orthophosphate solution is forced under a pressure of 6-40 bars into a fluidization zone; the orthophosphate solution is fluidized in the fluidization zone by injecting a finely dispersed permanent gas maintained under a pressure higher than the orthophosphate solution; and the fluidized orthophosphate solution is sprayed with the aid of a plurality of single medium nozzles arranged downstream of the fluidization zone through a flame zone produced inside the spray tower. Apparatus for carrying out the process.

Abstract: Alkali metal polyphosphates consisting substantially of hollow spheroidal particles with an apparent density of less than 350 g/l are made. To this end, an alkali metal orthophosphate solution is forced under a pressure of 6-40 bars into a fluidization zone; the orthophosphate solution is fluidized in the fluidization zone by injecting a finely dispersed permanent gas maintained under a pressure higher than the orthophosphate solution; and the fluidized orthophosphate solution is sprayed with the aid of a plurality of single medium nozzles arranged downstream of the fluidization zone through a flame zone peoduced inside the spray tower. Apparatus for carrying out the process.

Abstract: Alkali metal polyphosphates consisting substantially of hollow spheroidal particles with an apparent density of less than 320 g/l are made. To this end, an aqueous alkali metal orthophosphate solution and an aqueous solution of an inflating agent are simultaneously forced under a pressure of 6-40 bars into a fluidization zone; the two solutions are fluidized in the fluidization zone by injecting a finely dispersed permanent gas maintained under a pressure higher than the two solutions and the fluidized solutions are sprayed with the aid of a plurality of single medium nozzles arranged downstream of the fluidization zone through a flame zone produced inside the spray tower. Apparatus for carrying out the process.

Abstract: The disclosure relates to a process for the continuous dearsenification of polyphosphoric acid with the aid of hydrogen sulfide in a gas admission zone. To this end, the disclosure provides for the acid to be dearsenified in a gas admission zone subdivided so as to comprise at least two separate liquid matter-receiving zones, each zone being separated from the other by means of a separate gas zone; for the liquid in each of the liquid matter-receiving zones to be maintained at a level 0.