Hoechst Aktiengesellschaft

Johannes Krause

Hans Haas

Hermann Niermann

Gunter Reichert

Franz Mainzer

Werner Kowalski

Herbert Ressel

Herbert Diskowski

Hans Scheffer

Ben Damman

Paul De Witte

Dietrich Mandelkow

Iron and vanadium is phosphoric acid solution are reduced. To this end, the phosphoric acid solution is contacted with ferrophosphorus which is used as the reductant.

Process for reducing iron and vanadium in phosphoric acid solution

The disclosure relates to a process for making alkali metal polyphosphates, especially alkali metal triphosphates. To this end, the disclosure provides for an alkali metal phosphate solution or suspension to be forced through at least one nozzle and for them to be sprayed inside a spray tower through a flame zone produced by a one or more burners arranged in annular fashion. More particularly, the disclosure provides for fine particulate alkali metal polyphosphates, especially alkali metal triphosphates, to be additionally introduced into the spray tower from above and for them to be regularly distributed across the spray region(s) of the nozzle(s) with formation of agglomerated products. The disclosure also relates to an apparatus for carrying out the process. The apparatus is comprised of a cylindrical spray tower (1) having a tapered lower end (3) and being closed by means of a cover (2); a spray means (6) being passed centrally through the cover (2); a plurality of burners (11) and a solid matter feed means being passed through the cover concentrically with respect to the spray means (6) and so as to be spaced therefrom; and a bevelled issuing gas outlet (4) opening upwardly from the tapered end of the spray tower (1).

Process for making alkali metal polyphosphates

The invention provides a process and an apparatus for removing molten phosphorus pentasulfide, via an overflow, from a reactor, wherein phosphorus is reacted with sulfur at temperatures higher than 300.degree. C. To this end, the reactor is supplied with phosphorus and sulfur from dosing vessels which are given the dimensions necessary (a) to receive the quantity of phosphorus and sulfur, respectively, which are required to produce phosphorus pentasulfide with a preselected quantitative ratio of P:S, (b) to provide a total filling volume corresponding to that of a P.sub.2 S.sub.5 -receiving tank. The quantity of the phosphorus and sulfur feed materials in the respective dosing vessels is in each case fully emptied into the reactor and a corresponding quantity of molten P.sub.2 S.sub.5 is simultaneously discharged directly from the reactor, via the overflow, into the respective P.sub.2 S.sub.5 -receiving tank, whose filling volume exactly corresponds, to that of the dosing vessels.

Process for removing molten phosphorus pentsulfide from a reactor

The invention relates to a process for working up phosphorus-containing waste water by subjecting it to filtration with the use of a filter aid in a centrifugal filter. To this end, waste water with a temperature of at least 46.degree. C. and a pH-value within the range 0.5 to 4.0 is introduced into the centrifugal filter and fitrate coming from the centrifugal filter is introduced into a calming zone and separated therein within an average period of 10 to 60 minutes into yellow phosphorus and water containing 1 to 30 ppm of phosphorus. Water overflowing from the calming zone is treated with an oxidant and the waste water so freed from phosphorus is reacted with a neutralizing agent.

Process for working up waste water containing phosphorus

The reactivity of phosphorus pentasulfide produced by reacting phosphorus and sulfur at a temperature higher than the melting point of phosphorus pentasulfide and allowing the resulting melt to cool and solidify on a cooling device is improved. To this end, liquid phosphorus pentasulfide is placed on, or introduced into, a cooling device; an upper liquid P.sub.2 S.sub.5 -layer portion A is separated immediately from a solidified lower P.sub.2 S.sub.5 -layer portion B which is in direct contact with the cooling surface area of the cooling device; the upper P.sub.2 S.sub.5 -layer portion A is recycled to a P.sub.2 S.sub.5 melt; the lower P.sub.2 S.sub.5 -layer portion B is removed from the cooling device and collected as final product; the reactivity of the collected P.sub.2 S.sub.5 -layer portion B is increased to the same extent as the quantitative ratio of the P.sub.2 S.sub.5 -layer portion A to the P.sub.2 S.sub.5 -layer portion B is increased.

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Hurth, Germany

Johannes Krause