Gypsum economic importance

Of the two naturally occurring strontium containing minerals, strontianite (SrGOj) and celestite (SrSO, the latter occurs much more frequently in sedimentary deposits of sufficient quantities to make its recovery practical. Strontianite would be the more useful of the two common minerals, because strontium is used most often in the carbonate form. Gelestite occurs principally as nodules, lenses, beds and materials filling crevices in sedimentary rocks such as carbonates, gypsums, days and evaporites. The economic importance of celestite is con-... 

Celestite occurs principally as nodules, lenses, beds, and materials filling crevices in sedimentary rocks such as carbonates, gypsums, clays, and evaporites. The economic importance of celestite is considerably greater than that of strontianite. 

Regeneration of S02 from gypsum has been done via the Krupp-OSW process, the most important facility formerly being the Fedmis plant in South Africa, which made about 300 tons per day H2S04 and a similar amount of cement. Apparently, because of the high cost of cement and sulfur in this remote location, the plant was not economically viable and shut... 

Calcium. sulfate occurs naturally as its dihydrate, (natural gypsum) as anhydrous anhydrite and rarely as its hemihydrate in the form of the mineral bassanite. Only the deposits of natural gypsum and anhydrite are of economic interest. For applications in the construction industry only the hardenable modifications, calcium sulfate hemihydrate (a- and P-form) and anhydrite, which are manufactured by dehydrating the dihydrate, are important. The properties and formation conditions of the different calcium sulfate modifications are given in Table 5.3-11. 

The critical evaluation of the results in Table 9 leads to the following conclusion it seems that the mechanical behaviour of the cements formed improves when more red gypsum is added to the cements, thereby approaching the resistance values of the commercial cement. In faet, in the YC sample (10 % red gypsum) the mechanical resistance values are similar to those for the commercial cement. This is important, as it supports the use of red gypsum as an additive in the formation of cements and because it is possible to reduce the amount of clinker used, with all the economic benefits that tliis entails (cost savings). In this sense, it is necessary to remember that the commercial cement taken as reference in our study is approximately 97% clinker and 3 % natural gypsum. 

Uitilization of FGD gypsum in cement-based material is feasible. It is not only for environmental uses, but also in construction and civil engineering. The results contribute to a greater understanding of how to sustainably and beneficially manage various industrial wastes and byproducts and suggest that there are also several important environmental and economic benefits that can be realized. 

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