Hoechst Aktiengesellschaft

Wolfgang Becker

Thomas Staffel

Reinhard Gradl

Herbert Neumann

Gregor Fucker

To prepare essentially water-insoluble, long-chain ammonium polyphosphate, in a first stage, ammonium orthophosphate and phosphorus pentoxide are reacted in the presence of gaseous ammonia in a reactor equipped in its interior with mixing, kneading and comminution apparatus, until the drive motor of the reactor passes through the second current peak in its current consumption/time diagram. In a second stage, the material discharged from the reactor is then fed to a disk dryer, the heating disks of which are maintained at temperatures of 240.degree. to 300.degree. C., whereas its lower cooling disk has temperatures of 5.degree. to 45.degree. C. The material, which covers the disks of the disk dryer at a layer thickness of 5 to 20 mm, has a residence time of 35 to 70 minutes in the disk dryer, while ammonia-containing gas is continuously passed through the disk dryer. Finally, the ammonia-containing gas exiting the disk dryer is freed from water vapor contained therein by condensation and the ammonia-containing gas is reheated prior to its entry into the disk dryer.

Process for the preparation of ammonium polyphosphate

For producing substantially water-insoluble, chain-type ammonium polyphosphate, equimolar quantities of diammonium phosphate and phosphorus pentoxide are reacted at temperatures from 170.degree. to 350.degree. C. in a zone, which effects continuous mixing, kneading and comminution, in the presence of a stream of ammonia gas. In this process, the water is separated from the ammonia gas which leaves the zone and contains water vapor, and the dried ammonia gas is caused to flow again through the zone. A plant for producing substantially water-insoluble, chain-type ammonium polyphosphate can comprise a reactor (1) into which an ammonia feed pipe (8) and pipes for feeding phosphorus pentoxide (6) and diammonium phosphate (7) lead and from which an ammonium polyphosphate discharge pipe (9) and an exit gas pipe (10) start. The exit gas pipe (10) leads into a condenser (13) which is flow-connected via a pump (14) to a heat exchanger (15). An exit gas line (18) which leads into the ammonia feed pipe (8) starts from the heat exchanger (15).

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Erftstadt, Germany

Wolfgang Becker