PRODUKTUTVIKLING

Målet med prosjektet har vært å beskrive egenskaper og vurdere bruksområder for restprodukter (her kalt Sican) fra A/S Polymers prosess for å fremstille aluminiumskjemikalier fra anortositt. Spesielt er det lagt vekt på å vurdere det som råstoff for pozzolan tilslag i betong og som filler. Aluminium og kalsium i anortositt mineralet går i løsning etter syrebehandling. Residuumet består av restene fra lakeprosessen av bergarten anortositt, der mesteparten av aluminium, kalsium og natrium ionene i mineralstrukturen fjernes Bergarten består i utgangspunktet av mineralene anortitt (90-95%) og mindre mengder andre silikatmineraler. Materialet får etter utluting en store spesifikke overflate og porøsitet. Spesifikk overflate er målt til 57 m²/g, noe som skyldes indre porerom i de utlutede mineralpartikler. Porestørrelsesfordel- ingsdiagrammer viser at 2/3 av porene er mindre enn 40 Ångstrøm. Ved magnet- separasjon av materialet enten før eller etter utlutingsprosessen kan hvitheten på materialet forbedres fra 81% til 93%. Et relativt omfattende testprogram for bruk av Sican i betong er utført av FBC/SINTEF og Institutt for betongkonstruksjoner på NTH. Resultatet er blant annet at Sican gir tilsvarende økning i fasthet som eksisterende silikatstøv, i tillegg reduserer den varmeutviklingen i betong de første døgnene.

XRF-analyses of products from beneficiation tests of Nakkan talc, made by OMYA GMBH, is described. The results are compared with earlier test-results from Nakkan and from the mine. The mineralogical compositions have been estimated from the chemical data. The purest talc products contain around 96-97% talc and, in addition, minor amounts of chlorite and carbonate. The carbonate-product "Mag 2" contains around 80% carbonate, 15% talc and 5% chlorite. Based on XRF analyses, the Ni content in the talc products is around 0,16%, which is comparable to earlier studies of Nakkan products, but lower than in products from the mine which contain around 0,24%. If similar procedures have been followed in the benefication process, a general lower content of Ni in the talc lattice from the Nakkan deposit compared to the mine is indicated. Instead, more Ni is bound in sulphides and spinels. Although not encountered earlier in the Altermark talc by the present author, possible trace amounts of As are weakly indicated. Since important trace elements occur in very small amounts or below the detection level by XRF, it is recommended to apply other analytical methods (ICP-AES, AAS, LECO) with lower detections levels to achieve more correct numbers.

The chemistry of products from benefication tests of Altermark talc made by Pluss-Staufer AG is described. The earlier conclusions that the ore is very pure when it comes to elements with potential risks to health have been confirmed, although minor amounts of Cr and Ni are present. Of major importance is the composition of talc-products from the Nakkan deposits, which is currently being investigated, and the current mine as well as their relationship to chemical composition of the crude ore. Pluss Stauffer has succeeded in making pure talc-products of high quality of the Altermark talc. Some slightly different results were obtained from the Nakkan ore, with respect to recovery and whiteness, which were also element characteristics of products, but with some small variations in the content of Ni and Cr. The content of Ni and Cr are lowest in the Nakkan product. Estimation of mineralogy from the chemical data, indicate that the amount of talc in the best products reaches around 95%, the remainder being carbonates and chlorite. In the present report a model is presented which explains the variations in the Ni and Cr contents in relation to the grade of talc-carbonate alteration. With progressive alteration of serpentinite to talc-carbonate the magnetite and Ni-bearing sulphides disappear. The Fe from magnetite moves into carbonate, talc and chlorite, while Ni from the sulphides moves into talc, and to a limited extent, into carbonate. Chromium, which is abundant in magnetite, moves primarily into chlorite, but to a much more limited extent also into talc.