Analysis of technologies and practice of limonite ore processing

The article analyzes technologies and practice of limonite ore processing in Russia and abroad. Results obtained at the Russian and foreign processing plants are reported with the description of the applied concentration circuits and concentrates. The authors give characteristics of limonite ore from Mokroolkhovskoe deposit and discuss the ore concentration tests. Features of texture and structure, mineralogy and chemistry of the ore are described. The article presents the results of gravity, flotation and roasting–magnetic concentration of limonite ore from the specified deposit. Conclusions are drawn based on the analysis of the obtained results. Reserves of limonite ore are the third largest in the world and occur in the CIS countries, Germany, France, Great Britain, Australia, Canada, former Yugoslavia, Bulgaria and some other countries. Limonite ore was one of the key types of iron ore in the former Soviet Union. The issue of beneficiation and processing of limonite ore is very topical worldwide but no economic methods are yet developed. Limonite enjoyed the highest concern in the 1960–70ies featuring mature research in the related area of science. In the 1980ies limonite production suddenly dropped and was almost terminated later on. Foreign countries dressed limonite ore using gravity and magnetic concentration. Gravity concentration involved washing and heavy-medium separation. Currently, nearly world’s single plant engaged in limonite ore processing is Lisakovsk Mining and Processing Integrated Works, Orken LTD. The plant uses gravity–magnetic concentration circuit yielding the concentrate with the iron content of 49–49.5% at the recovery of 65–66%. One of the promising mineable deposits is Mokroolkhovskoe iron ore occurrence. Analysis of processing properties of ores from Kamyshin basin and their test concentration using gravity, flotation and roasting–magnetic methods was implemented by the Mekhanobr Institute, laboratory of Kamysh-Burun Plant and Bardin Central Research Institute for Ferrous Metallurgy. Based on the tests, it has been concluded that:– gravity concentration with washing, jigging and heavy-medium separation is inefficient, nothing but jigging has yielded the concentrate with the iron content from 36–44.5% at the recovery from 47 to 94%;– flotation concentrates have the iron content of 39–45% at the recovery of 65–75%, with high content of phosphoric anhydride, silica and alumina;– roasting–magnetic concentration of Mokroolkhovskoe limonite ore has exhibited sufficiently high efficiency and yielded the concentrate with the iron content of 51% for sample I (hydrogoethite) and about 48% for samples II and III (ferro-chlorite) at the recovery of 91–93%. The content of phosphoric anhydride is 0.82–0.91%.It is infeasible to develop Mokroolkhovskoe deposit at the present time in view of low technology parameters and the recent conditions on the market of iron-bearing raw materials. A way out seems to be continuing treatment of limonite ore using Romelt process. The application of roasting–magnetic concentration, as the highest effective method, in combination with the Romelt process will allow a competitive product at lower capital costs of mining Mokroolkhovskoe and other analogous deposits. The study was supported by the RF Ministry of Education and Science in the framework of the federal targeted program “R&D in the Priority Areas of Science and Technology Complex of Russia in 2014–2020”, Unique Agreement Identifier RFMEFI57814X0049.