PROCEDURE FOR IMPROVING THE CHARACTERISTICS OF A BY DEHYDROGENATION OF A PHOSPHOGIPSES RECEIVED GYPSUM

The invention concerns a procedure for improving the characteristics of a gypsum received by dehydrogenation of a Phosphogipses, which contains metal salts of phosphoric acid as impurities in particular synkristallisiert in the Phosphogips. With the procedures for the production of Phosphersäuren by effect of sulfuric acid 5auf natürIich occurring phosphates are called, formed substantial quantities of gypsum mud, in the following Phosphogips. It was tried to make this Phosphogipsschlamm usable by transformation in gypsum in economic way u.zw by controlled heating up and/or baking. In order to receive a gypsum in the neutral pH range by controlled heating up and baking of an also very carefully cleaned Phosphoglpses, it is inevitably necessary to admit 10entweder before or after baking a basic substance (for example lime) in order those drinks salts to neutralize, which are enclosed in the crystalline net of the Phosphogipses, but will collect themselves by the putting on water for the gypsum freely and therein. Even if this procedure gives interesting results with some Phosphogipsarten, it does not permit to obtain acceptable results if the Phosphogipssehlamm comes from certain very useful phosphates, so for example the phosphates KIIOURTBGA (Marecco). Without it admits the reasons for the fact is why from certain phosphates of due Phosphogipsschlamm an unsatisfactory and appropriate behavior shows, if it is converted into gypsum, is from the simple addition of a basic material to judge that this phenomenon is to due to the presence of unfavorable phosphate ores of Fluer, silicon and aluminum. The invention is not limited to the processing of kinds of gypsum from Phosphogäps, which are won by effect of sulfuric acid on phosphates originating from Marocco, but them completely generally cover kinds of gypsum, which are due to phosphates, which contain these impurities due to the sulfuric acid treatment, with production of relatively small quantities of aluminum fluorine compounds (AIFs--), which are synkristallisiert with the Phosphogips. It was received found that it möglieh is, from such phosphates a Phosphogips and then a gypsum to, which exhibits interesting manufacturing properties. The procedure according to invention is characterized by it that one in presence of 30Wasser an additive on basis of a fluorine compound, like a Fluorsi] ikat, preferably ammonium fluorine silicate or potassium fluorine silicate, admits, that in the aqueous environment under setting free fluorine ions gradually hydrolyzed, whereby the fluorine compound in such a quantity sets zugeF becomes that the VerhäItnis P2 0 lies between 0,2 and 1, whereby F mean the weight of the fluorine ions freed by the Einwirknng of the Pluorverbindung during tying the gypsum and P zO the weight of the synkristallisierten phosphates expressed in phosphoric acid anhydride, furthermore that one adds a neutralization means, preferably to lime, in a quantity, which is sufficient for the neutralization of the tied gypsum. Without committing itself to an exact explanation of the different phenomena, it is accepted that the used additives cause the AusfaIlen of the sour phosphate ions become free in the putting on water during tying the gypsum, u.zw. in the form of fluorine apatites crystallized well, which are very insoluble, whereby the education is avoided by hydroxyl apatite gels, which the Waehstum of Gipskristal] EN would disturb. Everything runs off in such a way, as if this hypothesis applies, dh. that on the one hand the invention is applicable to kinds of gypsum (those of Phosphogips are due), the synkristallisierte phosphates however no sufficient quantity of fluorine aluminum connections (A1Fs-- ), those contain at this moment tying the gypsum, which supply necessary fluorine ions for the education of the very soluble fluorine apatites; on the other hand than additives the used fluorine compounds to be gradually hydrolyzed must, i.e. with such a speed that the fluorine ions in the measure, formed by this hydrolysis, arise like it, with which phosphate ions freed during the treatment of the gypsum with putting on water it reacts. To the useful fluorine compounds belong in particular the fluorine silicates, whose metallic Katiofien with the fluorine forms wasserlSsliahe fluorides. For example Natriumfluorosilikat, Kaliumfluerosilikat, Ammoniumfluorcsilikat or Zinkfluorosilikat are used. Kalium-und ammonium compounds is preferential. The used quantities of Fluorosilikaten are variable according to the different kinds of gypsum (or Phosphogipsarten). It is indeed appropriate to proceed with a given gypsum (to a Phosphegips is due) as follows: A certain quantity gypsum is diluted in water and the pH value of the solution is measured. Then to this solution a neutralization means (lime) in different quantities is admitted, in such a manner that after the complete Hydratisierung of the gypsum a neutral suspension will receive (pH value between 6 and 8). ton then a dose by P2 05 determined, which is present which quantity of fluorine silicate, approximate in form of a synkristallisierten metal salt in the gypsum, in order to determine, to the gypsum will be admitted must. Afterwards gypsum, Fluorosilikat and neutralization means are mixed with one another (whereby it is considered that the neutralization means must neutralize also the acidity which is due to the hydrolysis of the admitted Fluoro15silikats), in such a manner that pieces of gypsum sample will receive firm, their characteristics is measured. The mixture, which shows the best characteristics, is kept as basis. It is actually possible, the sample attempts only once for all further linear paths durehznführen, if in a given industrial plant the same output phosphate ore and 20die same treatment procedures for this Phopshat, as well as the recovery and washing of the Phosphogipses are used. Preferably one adds the fluorine compound to the gypsum or the gypsum powder. The invention is more near described on the basis some remark examples. Comparison example: Phosphogips was manufactured as by-product with the treatment of a phosphate 25aus KHOURIBGA (Marocco) by sulfuric acid. This Phesphogips was baked under controlled conditions, in order to receive a gypsum, which essentially consisted of hemihydrate. To this gypsum in actually well-known way was admitted lime in rising quantities and with tying the different mixtures for each particular the pH value, the time up to complete tying (measured with the Vicat needle) as well as the values of the breaking strength under Biegeund compression stress (determines according to tying the dry samples 4×4×16 cm) measured. The results received thereby are shown in Fig.1. Show: the abscissa the approx. (OH) 2 - content in Gew. - % in the gypsum; the left ordinate the pH value of the gypsum after tying, based on a dispersion of 50% of the mixture in water u.zw a sample, which became to receive by scraping a thickness off from 1 mm from a hard and dry piece of gypsum. The curve of the pH values is broken drawn; the right ordinate the values: the Ahbindezeit (in min) - pulled through line, which ultimate strength under compression stress (in bar) - strong pulled through line, which bending ultimate tensile strength (in bar) - dots. This Fig. it shows in descriptive way that on production of a neutral gypsum. (PH value between 6 and 8) by addition of lime serious disadvantages arise, u.zw. both regarding the setting time, which is substantially extended (whereby certain samples 45nicht could be measured more), and the mechanical characteristics of the received pieces of sample. Example 1: A gypsum of the same Phosphogipsschlamm 0.3 Gew became made. - % Kaliumfluorosilikat and rising quantities lime admitted. The pH value of °einer 50%igen Suspensien of the different mixtures in water was measured and accomplished then the 50Abbindevorgang. Subsequently, like the setting time and the mechanical characteristics (Druck-und bending load) of the pieces of sample (4×4x16 cm) were measured above. r Nr.360414 the results are represented in Fig.2. Show: the abscissa the Gew. - % of the lime in the mixture, the left ordinate the measured pH value, broken drawn, the right ordinate the values of the setting time (in min) - pulled through line, the ultimate strength during compression stress (in bar) - strong continuous line, the ultimate strength during bending load (in bar) - line dotted. The results show clearly that by addition by Kaliumfluorosilikat the characteristics of the gypsum won from Phosphogips can be stabilized and improved, in particular 10im neutral pH range. Example 2: Similar attempts became on the basis of the same gypsum under addition of 0,15 Gew. - % fluorine, related to the gypsum, in form of different Fluorosilikate and 0.6 Gew. - Approx. (OH) = accomplished. The products received with identical kinds of gypsum were compared, as different 15Mengen was admitted approx. (OH) 2 however no Fluorosilikat. With these attempts the following measurements were accomplished: Setting time (in min) with the Vivat needle for a relationship water/gypsum of 0,8. Ultimate strength with Biegeund compression stresses (in bar) on dry and put on pieces of sample of 4x4x16 cm with a relationship water/gypsum of 0,8. PH value of the gypsum after tying, based on 50 a igen dispersion of a sample, which became to receive by scraping a layer off from 1 mm of a hard dry piece of sample. The received results are summarized in the following table: Gew. - Approx. (OH) 2 kind of the Fluorosilikates table I pH value of the gypsum setting time {in bar) ultimate strength when demand by bending pressure 0,0.3,0.6,0.6,0.6 o, 6,0.6 K SI F “well ZSI F6 (NHù) ZSI F6 Zn SI F6 3.6,7.3 10.2 6.9,7.0,7.0,7.3 8 min > 14 43 41 27 98 46 92 76 96 77 it is evident to 100 min min min 24 min 23 min min that the additives (neutralization means and Flnorderivate) at this moment the use (ties the gypsum reacts. These additives must be present from there in this stage. From it results that the additives are added during different stages of the gypsum production from Phosphogips kSnnen (if these additives are stable). In addition, they can be given during putting on the gypsum, u.zw either directly to the gypsum or to the putting on water. It is preferred adding the neutralization means to the Phosphogips to its cheeks to gypsum and adding the Fluorosilikat either the finished gypsum during its storage or for the moment its use.