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  See discussions, stats, and author profiles for this publication at: Iron Ore Sintering: Process  Article   in  Mineral Processing and Extractive Metallurgy Review · February 2017 DOI: 10.1080/08827508.2017.1288115 CITATIONS 9 READS 5,326 5 authors , including: Some of the authors of this publication are also working on these related projects: Investigation and evaluation of solar energy as energy source in the treatment of metallurgical by-products (P1701250238).   View projectproyecto privado con Orovalle (Belmonte de Miranda, Asturias)   View projectDaniel Fernández GonzálezUniversity of Oviedo 34   PUBLICATIONS   111   CITATIONS   SEE PROFILE I. Ruiz-BustinzaSpanish National Research Council 53   PUBLICATIONS   228   CITATIONS   SEE PROFILE Carmen González-GascaEuropean University of Madrid 15   PUBLICATIONS   82   CITATIONS   SEE PROFILE Luis Felipe VerdejaUniversity of Oviedo 257   PUBLICATIONS   457   CITATIONS   SEE PROFILE All content following this page was uploaded by Daniel Fernández González on 20 October 2017. The user has requested enhancement of the downloaded file.  Full Terms & Conditions of access and use can be found at Download by:  [UOV University of Oviedo] Date:  20 June 2017, At: 08:08 Mineral Processing and Extractive Metallurgy Review An International Journal ISSN: 0882-7508 (Print) 1547-7401 (Online) Journal homepage: Iron Ore Sintering: Process D. Fernández-González, I. Ruiz-Bustinza, J. Mochón, C. González-Gasca & L. F.Verdeja To cite this article:  D. Fernández-González, I. Ruiz-Bustinza, J. Mochón, C. González-Gasca &L. F. Verdeja (2017) Iron Ore Sintering: Process, Mineral Processing and Extractive MetallurgyReview, 38:4, 215-227, DOI: 10.1080/08827508.2017.1288115 To link to this article: Accepted author version posted online: 16Feb 2017.Published online: 16 Feb 2017.Submit your article to this journal Article views: 149View related articles View Crossmark dataCiting articles: 1 View citing articles  Iron Ore Sintering: Process D. Fernández-González a , I. Ruiz-Bustinza b , J. Mochón b , C. González-Gasca c , and L. F. Verdeja a a Department of Materials Science and Metallurgical Engineering, School of Mines, Energy and Materials, University of Oviedo, Oviedo, Asturias,Spain;  b Department of Primary Metallurgy and Recycling, National Centre for Metallurgical Research (CENIM-CSIC), Madrid, Spain;  c EuropeanUniversity of Madrid  –  Laureate International Universities, Villaviciosa de Odón, Madrid, Spain ABSTRACT Sintering is a thermal agglomeration process that is applied to a mixture of iron ore fines, recycledironmaking products, fluxes, slag-forming agents, and solid fuel (coke). The purpose of the sinteringprocess is manufacturing a product with the suitable characteristics (thermal, mechanical, physical andchemical) to be fed to the blast furnace. The process has been widely studied and researched in the ironand steelmaking industry to know the best parameters that allow one to obtain the best sinter quality.The present article reviews the sintering process that the mixture follows, once granulated, when it isloaded onto the sinter strand. There, the sinter mixture is partially melted at a temperature between1300-1480°C and undergoes a series of reactions that forms the sinter cake to be loaded into the blastfurnace to produce pig iron. KEYWORDS Agglomeration; CAP process;flame front; HPS process;iron ore; MEBIOS process;sintering; softening andmelting 1. Introduction Oxidized iron ores with a granulometry within 10 and120 mm were loaded into the blast furnace until the fiftiesof the last century (Peacey and Davenport 1986). The devel-opment of agglomeration processes appeared with the pur-pose of using iron ores (and concentrates) with a size lowerthan 10 mm (Sancho et al. 2000). Agglomeration processesinclude  briquetting   (used in ferroalloys industry, Ordialeset al. 2016),  nodulizing, sintering  , and  pelletizing  .Sintering is a thermal agglomeration process (1300-1480°C,Eisele and Kawatra, 2003) of a mixture of iron ore mineral fines(0.5-8 mm), by-products of the iron and steelmaking industry,fluxes, slag-forming elements and fossil fuel (coke). The objec-tive of the process, whereby the mixture of materials charged ispartially fused at a high temperature to produce clusteredlumps, is obtaining a load (12-35 mm) for the blast furnacewith the suitable physical-chemical and mechanical propertieswith the lowest price (Fernández-González et al., 2016).The origin of the sintering process was in 1887 whenF. Haberlein and T. Huntington (Patent no. US786814)invented a sintering process for copper sulphide ores. Theprocess was based on a sintering bed being blown with airfrom bottom upwards. This process was also known as up-draft sintering process (Patent no. US786814). In 1902, asintering method for pyrite cinder and dusty iron ores withaddition of coal and air blowing through the bed from bottomupwards was patented (Patent no. DE137438). In 1905, E. J.Savelsberg applied the Huntington-Heberlein equipment tothe sintering of iron, and by 1912 there were fifteen iron oreplants using that technique (Koerner and MacDougall 1983)(Patent no. DE210742). In 1906, A. S. Dwight and R. L. Lloydinvented a machine for vacuum sintering (Patent no. US882518 A). In 1909, A. S. Dwight and R. L. Lloyd invented amoving-bed of fine ore particles and additives supported on ametallic chain type strand with exposure to high tempera-tures, (Patent no. US916393). In 1909, a rotatory type of sintering machine was patented (Patent no. DE226033). In1913, W. K. Bartsch described a sintering method (belt type)for operation with air blowing from bottom upwards (Patentno. DE276424). Since then, Dwight-Lloyd technology hasbeen the main technology for iron ore sintering (Ghosh andChatterjee 2008). 2. Sintering process The sintering process is based on treating a mix (mineralfines, return fines, fluxes, etc.) layer in presence of coke dustto the action of a burner placed in the surface of the layer. Inthis way, heating takes place from the upper to the lowersections. The mix layer rests over a strand system and anexhausting system allows to the whole thickness to reach thesuitable temperature for the partial melting of the mix, andthe subsequent agglomeration. In the Dwight-Lloyd system,the sintering grate is a continuous chain of large length andwidth, formed by the union of a series of pallet cars that makethe sintering strand (Figure 1).Each pallet car passes below a charging hopper where ischarged firstly by material of coarse granulometry (10-20 mm)in a layer of 3-6 cm that forms the hearth layer composedmainly by sinter (Umadevi et al., 2011; Gupta 2010). The hearth layer protects steel grates from over-heating during the CONTACT  D. Fernández-González Department of Materials Science and Metallurgical Engineering, School of Mines, Energy andMaterials, University of Oviedo, Oviedo, Asturias 33004, Spain. MINERAL PROCESSING AND EXTRACTIVE METALLURGY REVIEW2017, VOL. 38, NO. 4, 215 – 227 © 2017 Taylor & Francis Group, LLC  sintering process. Secondly, and over the first layer, a secondlayer of fine material (0-8 mm) is charged. This second layer isformed by fine mineral, return fines, fluxes and coke.Then, the pallet car passes bellow an initializing furnace,where the combustible ignition takes place in the surface of the mix. At the same time, the mix is subjected to down-draught suction through the load.The pallet car continues the process and the combustionprogresses in the direction of the gas flow. In this way, thesintering process takes place. The combustion process doesnot happen simultaneously in the whole thickness of the bed.On the contrary, combustion happens as a horizontal layerthat moves vertically through the bed. The thickness of thislayer is a small fraction of the bed. Permeability is a quality requirement for the load, and for that reason the granulationprocess is previously used (permeability is improved duringgranulation) (Fernandez-González et al., 2017). In the regionabove the combustion zone, very hot sintered product heatsthe air that passes through this layer. In this way, pre-heatedair arrives to the combustion area. The heat of the air/gasespreviously heated is absorbed in these cold sections, causingpreheating of the load and evaporation of the water. In thiscontext, high temperatures that cause partial melting arereached, and the sintering process takes place.This high thermal efficiency is caused by heat accumula-tion in a partial layer of the load called sintering zone orflame front. The flame front progresses at 10-30 mm/min(23.9-27.7 mm/min, Zhou et al., 2015; 12-28 mm/min,Loo and Dukino 2014) towards the sintering grate. In abed height of 500-600 mm the process would take 25 min-utes (Gosh and Chaterjee, 2008).Once the end of the strand is reached, the sintered materialis discharged and subjected to cooling, crushing, and screen-ing. Obtained product can be divided into three granulo-metric fractions: ●  Between 0 and 5 mm (0 and 10 mm, according to Gupta2010), called return fines, which are sent to the feedinghoppers (Williams 1983; Lu and Ishiyama 2015; Loo and Dukino 2014; Mochón 2014a). ●  Sinter with a granulometry within 5 and 20 mm is usedas hearth layer in the sinter strand. Other authors con-sidered other granulometric fractions: 10 and 20 mm(Umadevi et al., 2011; Ying et al. 2011) or 10 and 15 mm (Gupta 2010). ●  More than 20 mm (Umadevi et al., 2011) o more than15 mm (Gupta 2010) are directly sent to the blast fur-nace. Maximum grain sizes <50 mm according to Luand Ishiyama 2015.Return fines are unavoidably formed during the sinteringprocess, and are recycled back into the sintering process, mak-ing up 30 to 40% of the iron bearing materials. Wu et al. 2013,studied the proper ratio of using return fines in the sinteringprocess. They observed that return fines from sintering sievingwere a little easily assimilated than that from the blast furnacesieving due to the lower high-Ca calcium ferrite content (Wuet al. 2013). Wu et al. 2013 suggested an optimal ratio of 30 mass % (max.) return fines from blast furnace sieving and 20 mass %return fines from sintering sieving.Four zones can be identified in the bed height: ●  Cold and wet zone : Includes the zone of the sinter bedwith a temperature lower than 100°C. This area isformed by the mix to be sintered, with upper limitsaturated in water/water vapor. ●  Drying zone : Sinter area with temperatures between100°C and 500°C. The vaporization of the mix moistureand subsequent dehydration of hydroxides take place. ●  Reaction zone  (maximum temperatures: 1300-1480°C,according to Eisele and Kawatra, 2003): Includes thezone of the sinter bed with a temperature between500°C (coke ignition beginning) and 900°C (coolingperiod beginning). The main processes that happen inthis zone are: coke combustion (exothermal), carbonatesdecomposition (endothermal), solid phase reactions,reduction and re-oxidation of iron oxides and reactionsof formation of the sintered mass. ●  Cooling zone : This zone is found immediately after thereaction zone. Cooling and re-crystallization of the sin-tered product take place. There is a superficial zonewhere the sinter layer is brittle than in the rest of thesinter bed. Figure 1.  Sintering plant scheme. 216 D. FERNÁNDEZ-GONZÁLEZ ET AL.

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