Hoechst Aktiengesellschaft

Markus Erpenbach

Werner Kowalski

Hans Haas

Theo Dahmen

Gero Heymer

Alexander Maurer

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.

Spheroidal alkali metal polyphosphates of low apparent density, and

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.

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.

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 0.1 up to 10 cm high, without admission of gas; for hydrogen sulfide which remained unreacted in the individual liquid matter-receiving zones to be collected in the respective gas zone and for it to be finely redispersed in the liquid matter-receiving zone directly upstream of the respective gas zone by allowing the hydrogen sulfide to flow through a plurality of openings into the acid, the latter being delivered from the respective liquid-matter-receiving zone into the next downstream liquid-matter-receiving zone, and introduced thereinto directly below the liquid matter level therein; for precipitated arsenic sulfide to be separated from the acid coming from the lower end of the gas admission zone, and for the filtrate obtained to be freed from gaseous hydrogen sulfide in excess.

Growing community of inventors

Cologne, Germany

Markus Erpenbach