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CR3 Communication: Red Mud – a Resource Or a Waste? Partners in Progress K

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CR3 Communication: Red Mud – a Resource Or a Waste? Partners in Progress K JOM, Vol. 65, No. 3, 2013 DOI: 10.1007/s11837-013-0560-0 Ó 2013 TMS CR3 Communication: Red Mud – A Resource or a Waste? Partners in Progress K. Hammond, B. Mishra, D. Apelian and B. Blanpain 706KDVIRUJHGFRRSHUDWLYHDJUHHPHQWVZLWKVHYHUDOFDUHIXOO\VHOHFWHGRUJDQL]DWLRQVWKDWDFWLYHO\ZRUNWREHQH¿WWKHPDWHULDOV science community. In this occasional series, -20 will provide an update on the activities of these organizations. This installment, by the Center for Resource Recovery & Recycling (CR3), focuses on Bayer process residue. The CR3 is a research center established by Worcester Polytechnic Institute, Colorado School of Mines, and K.U. Leuven. Twenty-eight corporations and national laboratories along with support from the U.S. National Science Foundation’s I/UCRC program are sponsors of the center. “Waste is wasted if you waste it, other- the focus of several previous research behind material eligible for ironmak- wise it is a resource. Resource is wasted if efforts. One investigator suggests sepa- ing. Simultaneous recovery of Al and you ignore it and do not conserve it with rating the red mud (in slurry form) using Na is performed by mixing the red mud holistic best practices and reduce societal high intensity magnetic separation. The with a solution of caustic soda and lime costs. Resource is for the transformation resulting magnetic product can be used DW&DWSUHVVXUHVRI±03D7KLV of people and society.”1 as an ingredient for ironmaking or as a solution is supplemented into the Bayer Red mud, a byproduct of the Bayer pigment for pottery making. The non- process for increased alumina recovery. Process, is a mixture of metallic oxides magnetic portion can be applied in build- One approach utilizes the amphoteric that has proven to be a major disposal ing materials or supplemented back into characteristics of Al by extracting it problem due to its mass and toxicity. the Bayer process. Recovery of the Fe is via treatment with sulfuric acid. It also This disposal problem is compounded low.5 Another investigator reduces the attempts to extract the Al through bio- by the fact that for every kg of primary Fe with chlorocarbons before magnetic logical leaching using sewage sludge Al produced, 2.5 to 3.0 kg of red mud separation and uses the resulting magnetic bacteria.10 is generated. The global primary Al portion as feed for ironmaking.6Another Another process that emphasizes production is approximately 44 million research suggests drying the red mud, Ti recovery converts the red mud into tons.2,3 There are two current methods of blending with lime and ground coal and VRGLXPDOXPLQXPÀXRULGHFRPSRXQGV VWRUDJH7KH¿UVWLVWRVLPSO\SXPSWKH feeding the mixture into a machine that The red mud is mixed with hydrochloric red mud into holding ponds and the other agglomerates it into ½-in. diameter balls. DQG K\GURÀXRULF DFLG WR REWDLQ VLOLFLF is to store the mud after drying upon a Subsequently, the balls are pre-reduced acid, which is then separated out. Evapo- special liner. In the latter case, once there at high temperatures in a circular grate. ration leaves behind a material close LVVXI¿FLHQWUHGPXGWKHGU\VWDFNLVWKHQ The balls are then fed into a submerged- to cryolite. The remaining material is covered with topsoil. Both methods create arc electric furnace for smelting and mixed with the residual liquor, which the issue of land use. Table I shows a transported to a basic oxygen furnace, dissolves the Fe and Al. The Ti-rich solid typical compound analysis for red mud where high-quality steel is produced. remaining can be further processed via generated from Jamaican bauxite. As is 7KH¿QDOSURGXFW\LHOGVDERXW± chlorination.11 Synchronous recovery of evident, the presence of heavy metals Fe.7 Another process entails mixing the Al, Fe and Ti is investigated by a number such as lead, cadmium, and mercury, as red mud with Fe2(SO4)3. This solution of researchers. One method utilizes well as the presence of soda, is a serious removes the Na from the mud, leaving chlorination combined with fractional problem for groundwater.4 distillation to extract Fe and Ti from red Limited application of red mud has Table I. Composition of Dried North mud. The red mud can be leached prior to been tried as a constituent in industrial Coast Jamaican Bauxite and the this to retrieve Al.12 A novel technique is construction aggregates, such as bricks, Generated Red Mud being investigated where the red mud is road surface material, and cement, in carbothermically reduced in an electric- Bauxite Red combination with other waste products Compound (%) Mud arc furnace to produce pig iron and a VXFKDVÀ\DVKDQGLWKDVDOVREHHQWULHG (%) ¿EHUL]HGZRROPDWHULDOIURPVODJ13 DVDVRLOPRGL¿HU7KHVHDSSOLFDWLRQVGR A review of all these past and current Al2O3 56.4 14.7 not add value but can serve as a valid SiO2 0.7 2.6 efforts highlight certain limitations that route for waste utilization after metal(s) CaO 1.2 8.8 must be overcome before red mud can be extraction. Careful consideration is TiO2 4.3 7.2 converted into useful metals. These are: Fe2O3 35.1 60.7 required for addressing the vastness of Na2O0.01.61. Red mud is generated and cur- the problem via construction material Others (P, S, Cr, Mn, 2.3 4.4 rently stored where processing for applications. The extraction of Fe, the Hg, Pb, Zn, Cd, RE, alumina recovery from bauxite Mg) main constituent in red mud, has been ore (Bayer’s process) is done. Any 340 CR3 Communication: Red Mud – A Resource or a Waste? 341 recovery process from red mud that would require the transport RI UHG PXG ¿QH PDWHULDO ZLWK ± ZDWHU WR IDU GLVWDQFHV e.g. ironmaking operations, will likely be cost prohibitive. Thus, any conversion scheme that is adopted needs to be located near the bauxite processing facility. Whether an electric arc furnace or a rotary hearth type of process is used, it must be collocated. 2. Solid-state carbothermic reduction of red mud to recover Fe and its sep- aration from the remaining oxides YLDDQ\SK\VLFDOPHDQVLVGLI¿FXOW due to the mineralogy of red mud ZKHUH¿QHLURQR[LGHLVLQWLPDWHO\ associated with other oxides and does not allow the separation of reduced Fe in a concentrated form. This is a major limitation which Figure 1. A potential flow sheet for full red mud utilization under investigation in CR3. forces the carbothermic smelt- ing of red mud. A solid Fe-rich product, such as direct reduced resulting material may be smelted 2012), minerals.usgs.gov/minerals/pubs/commodity Fe, is unlikely. However, a solid to produce pig-iron and a slag now /aluminum/mcs-2012-alumi.pdf. 3. A.K. Staley, “An Investigation into the Pyrometallurgical product with reduced metallic Fe rich in calcium titanate. Titanium and Electrometallurgical Extraction of Iron from Red amenable to steelmaking remains could be considered a product Mud Generated in the Processing of Bauxite Ores,” a possibility. from this slag stream. However, Thesis No. T 5668 (Golden, CO: Colorado School of Mines, 2002). 3. Injection of red mud, with or the process suitable for Ti recovery 4. D. Gura, “Toxic Red Sludge Spill from Hungarian without pre-reduction, into a blast LVWKH6XOIDWLRQ0HWKRGGHYHORSHG Aluminum Plant —An Ecological Disaster” furnace through the tuyeres, is an E\WKH86%XUHDXRI0LQHV14 The (October 5, 2010), www.npr.org/blogs/thetwo-way /2010/10/05/130351938/red-sludge-from-hungarian interesting concept. However, the Kroll process is unsuitable due to -aluminum-plant-spill-an-ecological-disaster. high alumina content is a problem the high lime content of the slag. 5. J. Fursman, J.E. Mauser, M.O. Butler, and W.A. IRUWKHVODJÀXLGLW\DQGYROXPHLQ Based on these considerations, Stickney, ‘Utilization of Red Mud Residues From Alumina Production’, U.S. Bureau of Mines Report of the blast furnace and the high alkali )LJXUH VKRZV WKH ÀRZ VKHHW WKDW Investigations 7454 (1970). content is not compatible with the CR3 is attempting to improve upon. 6. R. Piga, F. Pochetti, and L. Stoppa, JOM, 45 (11) refractory and alkali accumulation. There appear to be more valuable (1993), pp. 55–59. 7. W. Braithwait, GB patent 2078211-A (January 1982). While lime, silica and titania addi- materials in red mud than the Fe and 8. Agency of Ind. Sci. Tech., J. patent 52152896-A tions from red mud are acceptable to Al, such as Ti and rare earth elements. (December 1977). the blast furnace, alumina and alkali Preliminary analyses indicate the levels 9. S. Guccione, Eng. Min. J., 172 (9) (1971), pp. 136–138. 10. N. Dakatos, M. Miskei, and J. Szolnoki, DE patent oxides must be removed before are relatively high. Further investigation 2,747,436 (May 1978). any injection. This concept will is needed on four main parts of the 11. M. Cresswell, and D.J. Milne, AU patent 88102 also require transportation adding previous research: a complete elemental, (September 1981). 12. R. Vachon, R. Tyagi; J-C. Auclair, and K.J. Wilkinson, to commercialization challenges. mineralogical and particle size analysis; Environ. Sci. Technol., 28 (1) (1994), pp. 26–30. 4. Removal of alumina via soda-ash solid state reductions for magnetic 13. E. Balomenos, I Gianopoulou, D. Panias, and I. roast and water leaching can pro- separation feasibility tests; smelting Paspaliaris, “A Novel Red Mud Treatment Process” (Paper presented at the 3rd Intl. Conf. on Industrial & duce a liquor that can be reverted reduction feasibility work for metal slag Hazardous Waste Management, Crete, Greece, 2012). back to the Bayer process, thus separation; and slag analysis for further 14. B. Mishra, A. Staley, and D. Kirkpatrick, Recycling generating a residue that will be recovery of metals. and Waste Treatment in Mineral and Metal Processing: Technical & Economic Aspects: Vol.2, ed. B. Björkman, very low in alumina and alkali References C.
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