Milling
In the early years of mining, sorting of ore started in the vein style deposits directly on the stopes. High grade ore containing more than 1% uranium was handpicked and later automatically separated and shipped to the Soviet Union without further processing until 1980. Ore containing less than 1% ("Fabrikerz" - factory ore) was sent to mills. In the early years of the SAG Wismut, it simply took over existing plants for processing its uranium ores. These were the mill of a tungsten mine in Lengefeld (Vogtland), the mill of the tin mine Tannenbergsthal (Vogtland), a plant processing cobalt ore to produce colours at Oberschlema, a nickel processing plant at Aue and some industrial areas at Freital. Further, a new mill was erected at Johanngeorgenstadt. These small mills produced different concentrates: mechanical concentrates, wet-mechanical concentrates and chemical concentrates ("Yellow Cake"). A total of 18 million tonnes of ore was processed in these smaller mill and the last was shut down in 1962. Milling was concentrated at two central milling sites situated between Zwickau and Ronneburg.
The mill at Crossen (a northern suburb of Zwickau) was already erected in 1950 using the site of a former paper mill. It was called Object 101 / Factory 38 (later renamed in Aufbereitungsbetrieb 101 - milling division 101) and processed ore from all major deposits of the Wismut. It produced mechanical as well as chemical concentrates and used for the latter one an alcalic-based technology resulting in Yellow Cake containing more than 70% uranium. The mill processed a total of 74.7 million tonnes of ore producing 77,000 tonnes of uranium before it was shut down in 1989. Experimental milling was also carried out processing silver and tin ore from the deposit Niederschlema-Alberoda and Pöhla.
In 1961 the most modern milling plant got into production at Seelingstädt called Aufbereitungsbetrieb 102 (milling division 102). It was built near the open pits of the Culmitzsch deposit which it used as tailings management facilities. It processed the majority of ore from Ronneburg, ore and solutions from Königstein but also ore from the Erzgebirge Mts. It used both acid and soda-alcalic processes depending on the chemistry of the ore to produce Yellow Cake. It processed in total 108.8 million tonnes of ore producing concentrate containing 86,273 tonnes of uranium.
About 216,000 tonnes of uranium were delivered in chemical and mechanical concentrates from the mills to the Soviet Union and about 15,000 tonnes were shipped in unprocessed high-grade ore directly from the mines.
The rehabilitation of the tailings storage facilities at the milling sites is a major issue for the Wismut GmbH. The tailings at both sites have a total volume of 152 million m3 and contain between 50 and 300 g/t uranium and between 50 and 600 g/t arsenic. The activity of radium in the tailings has a total value of 1.5*1015 Bq.
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Famous quotes containing the word milling:
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—Mary Barnett Gilson (1877–?)