Raw materials characterization for industrial lime manufacturing (original) (raw)
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Carbonate Rocks Characterization For The Industrial Lime Manufacturing: Worldwide Case-Studies
This paper reports an overview of representative and most significant case-studies analyzed by our lab in the last ten years. Customers from all over the world always send carbonate rocks samples to evaluate their suitability for the calcination process in Twin Shaft Regenerative (TSR) kilns, subsequently designed by CIMPROGETTI Spa. Internal procedure for the characterization of raw materials includes chemical, and physico-mechanical analyses, coupled to the burning attitude and technological tests. Recently, mineralogicalpetrographic examinations, deriving from a geological expertise, have been also performed, to evaluate the impact of compositional and microstructural fabric of carbonate rocks on the quality, and uses of the industrial quicklime. Especially, the digital microscopy image analysis, has been performed to determine the micrite to sparite (M/S) ratio, and the average crystal-size distribution. Compositional and microstructural parameters of carbonate raw materials can be successfully related to physico-mechanical properties, and the quicklime reactivity. As far as the last parameter is concerned, has been determined by means of the slaking test method on lime samples burnt in a muffle furnace at different temperatures, to predict the reactivity of an industrial lime produced in a TSR kiln using different fuels. As concerns technological tests, both the expansion of carbonate stones at 700°C, and the high temperature test at 1300°C, namely overburning test, have been performed. The former permits to predict the eventual clogging tendency of the kiln in the preheating zone, while the latter leads to predict the stickiness of the lime occurring during the maximum temperature in the kiln, as a consequence of the lime agglomeration.
It is well known that the most energy demanding stage in the cement industry, is the sintering process. The decrease of the energy consumption during the sintering can be brought about either by the improvement of the kiln design and performance or by the addition of mineralising or fluxing agents that accelerate the solid reactions and/or lower the melting point of the clinker liquid phase. It has been found that certain foreign elements, despite their low concentration in cement raw mix, may accelerate the sintering reactions and improve the reactivity of the cement raw mix. The subject of this paper is to investigate the possibility to introduce small amounts of minerals, containing these elements, in the cement raw mix. The minerals, iron rich wolframite, stibnite and a wolframite-stibnite assemblage, were selected in order to introduce W, Sb and S in the cement raw mix. One reference and twelve modified mixtures, prepared by mixing the reference sample with 0.5, 1.0, 1.5 and 2.0 % w/w of the above minerals, were studied. The effect on the reactivity of the raw mix is evaluated on the basis of the unreacted lime content in samples sintered at 1000, 1100, 1200, 1300, 1350, 1400 and 1450 o C. It is concluded that minerals containing Sb promote the consumption of the free lime, in the most effective way. In addition, the sintering reactions in all samples were recorded by means of differential thermal analysis (DTA). As it is shown, the added minerals affect mainly the final stages of the sintering and specifically the reactions that proceed in the presence of the liquid phase. This fact indicates that the constituents of the added minerals affect mainly the formation and the properties of the melt and therefore change the reactivity of the mixture at high temperatures.
In parallel with a wide scale program undertaken at University of Mons in collaboration with the Restoration Directorate of Public Service of Wallonia (SPW) concerning the suitability of mortars formulation for heritage conservation works in the Walloon Region, the authors set up a project to improve the understanding of contemporary and ancient lime as a material. This project involves, in a first step, the experimental on-site reconstruction of five lime kilns and, in a second step, series of lab replications based on data collected along the on-site process. Further than facing constraints encountered by ancient builders, the objective of the research concerns the possibility to outline specificities of ancient limes with regard to their mode of production (and eventual related limitations observed with industrial lime products). For their reconstructions, the authors focus their attention on a " short flame " kiln type used in the Walloon Region between roman and pre-industrial periods. They base their approach on results of archaeological excavations, ancient literature and archives, iconography, recent reconstitutions and experiments with craft kilns as well as ethnographic studies. Several limestones are considered as well as different fuels. Every test is recorded and instrumented (from local and manual temperature picking towards permanent survey in strategic parts of the kilns). The laboratory replication is carried out with computer-piloted electrical furnaces where evolutions of temperature collected on-site may be used as input data for imposing a given heating process to the limestone samples. Preliminary comparisons of products obtained with the on-site and in-lab processes allow outlining interesting results as physical and thermochemical outlooks are considered. Further investigations are in progress, namely considering mechanical aspects, mobilizing lime products that are industrially obtained with given limestones.
Key Engineering Materials, 2002
The use of selected secondary materials for improving the reactivity of cement raw mix, is a challenging subject. It is known that certain foreign elements exert a considerable effect on the cement raw mix burnability and clinker structure, even at low concentration. This work is part of a project on the use of selected minerals as a source of elements having a positive effect on the burnability of cement raw mix. The minerals, iron rich wolframite, stibnite and a wolframitestibnite assemblage, were selected in order to introduce W, Sb and S in the cement raw mix. One reference and twelve modified mixtures, prepared by mixing the reference sample with 0.5, 1.0, 1.5 and 2.0 % w/w of the above minerals, were studied. Their effect on the burnability is discussed in Part I. The subject of this paper is their effect on the structure of the produced clinker. The XRD studies, performed in samples that were burned at 1450 o C, showed that the diffraction patterns correspond to a structure of a typical clinker, obtained at the above temperatures. In addition, samples sintered at lower temperature (1200-1400 o C) were examined in order to investigate the effect of the additives on the intermediate products. It is concluded that the added compounds affect mainly the structure of calcium aluminate and calcium aluminoferrite phases, due to their dissolution in the melt formed during the sintering. Scanning Electron Microscopy was used in order to examine the structure of the clinker and the distribution of the foreign elements in its main phases. It is shown that W and Sb are mainly concentrated in the solidified melt. In addition, bigger and more roundish alite crystals are found in these samples. These modifications are attributed to the effect of the added elements on the properties of the melt.
Resumo In this work, comments are made about indirect methods and direct Chapelle's method applied to the determination of the reactivity of pozzo-lanic materials. The Chapelle's method is based on the lime-pozzolan reaction and quantifies the pozzolanic reactivity of any material intended to be applied by the cement industry. This lime consumption determination by the pozzolan through this reaction can be made with mass proportions – lime:pozzolan 1:1, as originally proposed by Chapelle or 2:1, as specified in Brazilian and French Standards. Comparative results with both proportions are presented for sugar cane bagasse ash, rice rusk ash, silica fume, fly ash, and metakaolin, commonly studied in our country. Statistical calculations showed that for some materials of similar characteristics to the researched RHA, FA e MK at issue, essays carried out with only 1g of CaO may be underestimating the amounts of CaO consumed per gram of pozzolanic material that can be obtained. Comments were made about the Brazilian and French Standards based on this method and emphasized the expression of lime consumption per mass of the amorphous phase of these materials, as determined by X ray diffraction analysis with the Rietveld refinement method. Keywords: pozzolanic reactivity, Chapelle's method, sugar cane bagasse ash, rice rusk ash, silica fume, fly ash, metakaolin Neste trabalho, são discutidos os métodos indiretos e método de Chapelle direto aplicados para a determinação da reatividade de materiais pozolânicos. O método Chapelle baseia-se na reação química cal-pozolana e quantifica a reatividade pozolânica de materiais destinados à aplicação pela indústria de cimento. A determinação do consumo de cal pela pozolana que ocorre por meio desta reação química pode ser feita empregando-se as proporções em massa cal: pozolana 1:1, como proposto originalmente por Chapelle, ou 2:1, conforme especificado nas nor-mas técnicas brasileira e francesa. São apresentados os resultados comparativos com as duas proporções cal-pozolana para cinza de bagaço de cana-de-açúcar, cinza de casca de arroz, sílica ativa, cinza volante e metacaulim, comumente estudados em nosso país. Os cálculos estatísticos indicaram para alguns materiais com características semelhantes aos da cinza de casca de arroz (CCA), cinza volante (CV) e metacaulim (MC), pesquisados em questão, que os ensaios realizados com apenas 1 g de CaO podem estar subestimando os valores obtidos de CaO consumidos por grama de material pozolânico. As normas brasileira e francesa foram discutidas com base nos resultados de ensaios Chapelle e enfatizou-se a quantificação do consumo de cal, em massa, pela fase amorfa destes materiais, que pode ser determinada pela análise de difração de raios-X por meio do método de refinamento de Rietveld.
Mineralogy and Petrology, 2017
This study evaluates the influence of chemical, mineralogical and petrographic features of the Neoarchean limestone from the Ouplaas Mine (Griqualand West, South Africa) on its burnability and quicklime reactivity, considering the main use as raw material for high-grade lime production in twin shaft regenerative (TSR) kilns. This limestone consists of laminated clotted peloidal micrite and fenestrate microbial boundstone with herringbone calcite and organic carbon (kerogen) within stylolites. Diagenetic modifications include hypidiotopic dolomite, micrite to microsparite recrystallization, stylolites, poikilotopic calcite, chert and saddle dolomite replacements. Burning and technical tests widely attest that the Neoarchean limestone is sensitive to high temperature, showing an unusual and drastically pronounced sintering or overburning tendency. The slaking reactivity, according to EN 459-2 is high for lime burnt at 1050 °C, but rapidly decreases for lime burnt at 1150 °C. The predominant micritic microbial textures, coupled with the organic carbon, are key-factors influencing the low burnability and the high sintering tendency. The presence of burial cementation, especially poikilotopic calcite, seems to promote higher burnability, either in terms of starting calcination temperature, or in terms of higher carbonate dissociation rate. In fact, the highest calcination velocity determined by thermal analysis is consistent with the highest slaking reactivity of the lower stratum of the quarry, enriched in poikilotopic calcite. Secondly, locally concentered dolomitic marly limestones, and sporadic back shales negatively affects the quicklime reactivity, as well. This study confirms that a multidisciplinary analytical approach is essential for selecting the best raw mix for achieving the highest lime reactivity in TSR kilns.
2019
Se presentan los resultados de pruebas analiticas realizadas en ladrillos fabricados a partir de diferentes mezclas de arcilla y ceniza. Las cenizas fueron obtenidas de un horno ladrillero tipo Hoffman equipado para coincinerar carbon y residuos solidos municipales. Las muestras fueron caracterizadas fisica y quimicamente y su calidad se determino a traves de pruebas de porosimetria, absorcion y esfuerzo de tension y de ruptura. La capacidad portante de los ladrillos aumenta con contenidos de ceniza hasta del 10% y decrece en proporciones mayores. La absorcion de agua es superior para todas las combinaciones de mezcla. Este estudio reporta que ladrillos elaborados utilizando mezclas arcilla/ceniza cumplen con todos los requisitos de calidad exigidos en Colombia.
Carbide lime and industrial hydrated lime characterization
Powder Technology, 2009
This paper focuses on the characterization of carbide lime (CL)a by-product of acetylene production, composed mainly of calcium hydroxide with minor parts of carbonateand compares its features to those of "dry" hydrated lime (HL) commonly used as a building material. Chemical, thermogravimetric and X-ray diffraction analyses indicated that the limes are similar in chemical and mineralogical compositions, except for the presence of carbon in the waste. Morphological and elemental chemical analyses by SEM and EDS revealed that CL particles differ from HL ones in their morphology and by the presence of carbon formations. Physical characterization included density and BET surface area of the materials, as well as, their particle size distributions in deionized water at diverse time periods. CL underwent agglomeration after approximately 60 min in water, whereas HL progressively became finer with time as determined by laser diffraction. In addition, water retention and squeeze flow tests were used to assess the pastes' fresh properties.
Process simulation of lime calcination in mixed feed shaft kilns
2018
Ich erkläre hiermit, dass ich die vorliegende Arbeit ohne unzulässige Hilfe Dritter und ohne Benutzung anderer als der angegebenen Hilfsmittel angefertigt habe. Die aus fremden Quellen direkt oder indirektübernommenen Gedanken sind als solche kenntlich gemacht. Insbesondere habe ich nicht die Hilfe einer kommerziellen Promotionsberatung in Anspruch genommen. Dritte haben von mir weder unmittelbar noch mittelbar geldwerte Leistungen für Arbeiten erhalten, die im Zusammenhang mit dem Inhalt der vorgelegten Dissertation stehen. Die Arbeit wurde bisher weder im Inland noch im Ausland in gleicher oderähnlicher Form als Dissertation eingereicht und ist als Ganzes auch noch nicht veröffentlicht. Magdeburg, den 09.01.2012