Abstract: A process may involve digesting raw phosphate with concentrated sulfuric acid and converting the raw phosphate to calcium sulfate in the form of dihydrate and/or hemihydrate, and phosphoric acid, separating off calcium sulfate as solid from a liquid phase of a suspension that is obtained, treating the calcium sulfate that is separated off or from a stockpile with an acid to give a suspension with purified calcium sulfate and P2O5-containing acid solution, separating off the purified calcium sulfate as solid from a liquid phase of a suspension obtained, using the P2O5-containing liquid phase as a portion of the sulfuric acid required for digesting the raw phosphate or as feedstock for treating phosphogypsum from the stockpile to give a suspension of purified calcium sulfate and P2O5-containing acid solution, which is thereafter processed.

Abstract: A process may involve treating calcium sulfate separated from phosphoric acid with acid to obtain a suspension comprising purified calcium sulfate, separating the purified calcium sulfate in solid form from a liquid phase of the suspension, treating the purified calcium sulfate with water or with a salt- and/or chelate ligand-containing aqueous solution to leach rare earths out of the calcium sulfate, separating the further-purified calcium sulfate in solid form from the liquid phase of the suspension, mixing the purified calcium sulfate that is separated off with admixtures and reducing agents to obtain a raw meal mixture for cement clinker production, burning the raw meal mixture to obtain the cement clinker and thereby forming sulfur dioxide as offgas, and feeding the sulfur dioxide as raw material to sulfuric acid production to produce the sulfuric acid.

Abstract: A method may be employed to produce a fertilizer granulate comprising an ammonium salt and, as a filler material, limestone, dolomite, and/or magnesite. At least a proportion of the limestone or dolomite or magnesite is at least partially calcinated prior to use in the fertilizer granulate. A targeted adjustment of the reactivity of the filler material may occur by its degree of calcination and/or its calcite proportion. If, for example, dolomite is used as a filler material, the calcination results in separation of carbon dioxide from the mineral. This calcination is a two-stage process in which the dolomite is first converted to periclase (MgO) and calcite (CaCO3), and the calcite is also converted by decomposition and release of carbon dioxide only at a higher temperature.

Abstract: A method for determining a charge state of a vanadium redox flow cell may comprise indirectly determining concentrations of V4+ and V5+ in a positive electrolyte by mixing positive and negative electrolytes with one another in particular proportions to reduce V5+ present in the positive electrolyte. In this way, CT complexes of V4+/V5+ may be avoided, the concentration of which is not determinable directly owing to the strong UV/vis absorption. Furthermore, the method enables determination of the concentrations of the negative electrolyte and positive electrolyte via UV/vis absorptions, which enables simple monitoring of the charge state of a vanadium redox flow battery.