Selective flotation separation of andalusite and quartz and its mechanism

The separation of andalusite and quartz was investigated in the sodium oleate flotation system, and its mechanism was studied by solution chemical calculation, zeta-potential tests, Fourier transform infrared spectroscopic(FTIR), and X-ray photoelectron spectroscopic(XPS). The flotation tests results show that FeCl3·6H2O has a strong activation effect on andalusite and quartz and citric acid has a strong inhibitory effect on activated quartz, thus increasing the floatability difference between quartz and andalusite when the pulp p H is approximately 8. The FTIR, Zeta potential, and XPS analyses combined with the chemical calculation of flotation reagent solutions demonstrate that Fe forms hydroxide precipitates on the surface of andalusite and quartz and that oleate anions and metal ions adsorb onto the surface of the minerals. The elements Al and Fe can be chemically reacted. The anions in citric acid have different degrees of dissolution of Fe on the andalusite and quartz surfaces, thereby selectively eliminating the activation of the elemental Fe on andalusite and quartz and increasing the floatability of andalusite, leading to a better separation effect between andalusite and quartz.

Sillimanite,Kyanite and Andalusite in China and Their Applications Part Ⅰ:Their Reserve,Distribution and Characteristics

Sillimanite, kyanite and andalusite are advantageous natural refractory raw materials for aluminosilicate refractories to attain improved key properties. This paper are divided into two parts to introduce their resource and technical characteristic in the first part, and their applications in refractories in the second part to be succeeded . In this part, based on authors ' knowledge and sources , information on their reserve, distribution, composition and characteristic is provided , to bring it to light that China is rich in the reserve of them , in particular andalusite. The sillimanite group minerals are characterized by their phase transformation to form primary mullite and secondary mullite when added in high alumina system , accompanied by volume expansion , which can be taken use to improve creep resistances and thermal shock resistance of the related refractories.

Mullite Refractory Made from Andalusite and α-Al_2O_3

Mullite refractory was made from micropowder of andalusite and α-M2O3 by an ' one-step sintering process' . This refractory has a lower linear expansion coefficient, more simple process and the sintering tem-parature can be decreased 200 - 25017 . But the cool strength of the material is near to that of fused casting mullite brick. For this material, the test sum of α-Al2 O3 added is 20% , the favorable sintering temperature is 1400℃.

Effect of Andalusite Aggregate Pre-fired at Different Temperatures on Properties of Al2O3-SiC-C Castables

This work investigates the effect of the pre-firing temperature of andalusite aggregate(5-3 mm)on the conversion of andalusite,the volume stability,the thermal shock resistance and the slag resistance of Al2O3-SiC-C castables.The results show that the volume stability and the thermal shock resistance of the castables could be adjusted at different pre-firing temperatures of andalusite aggregates.There was no noticeable difference in the slag resistance between the specimens without andalusite and those with andalusite aggregate pre-fired at different temperatures.

Effect of Carbon Graphite on the Crystallization of Andalusite: Application to the Synthesis of Mullite and the Improvement of Refractory Quality

Different mixtures of Moroccan silica-alumina geomaterials were used for the preparation of refractory ceramics. A formula of composition (M2) has allowed obtaining a good quality of refractory. Addition of a small quantity of carbon (1%) to the M2 formula has substantially improved the quality of the refractory. The morphological, textural and mineralogical evolution, through SEM and XRD shows that the addition of carbon, which plays a catalytic role, favors the crystallization of andalusite. Then, from 1200°C, the andalusite starts to transform to primary mullite needles. At 1400°C, the mullite becomes the major mineral phase beside cristobalite and vitreous phase.

Elaboration and Characterization of Mullite Refractory Products from Moroccan Andalusite

Enrichment of schist mined in Morocco resulted in an extract essentially made of andalusite, quartz and muscovite, which was investigated with the aim to synthesize mullite refractory materials. X-ray diffraction analysis was used to assess phase transformations upon heating at different temperatures. Mullite formation starts as early as 1200℃ and seems almost total at 1450℃. This process correlates with a weak shrinkage (3.5% at 1450℃) and the formation of an important glass phase. Green compacts obtained by unidirectional pressing the extract powder were heated under air in the temperature range 1200℃ - 1600℃. Chemical and mechanical properties of these materials were investigated and correlated with their microstructure.

Effect of Andalusite on Properties of Homogenized Bauxite Based Al2O3-SiC-C Castables

In this study,in order to evaluate the performance of homogenized bauxite,two Al_2O_3-SiC-C castables were prepared using homogenized bauxite and brown fused corundum as aggregates,respectively. 5 mass%andalusite was introduced into the two castables so as to research the effect and mechanism of andalusite in Al_2O_3-SiC-C castables. The results showed that：（1） compared with the brown fused corundum based castables,the homogenized bauxite based castables had higher cold strength after heat treatment,but lower hot modulus of rupture;（2） addition of 5 mass% andalusite could enhance the cold and hot modulus of rupture,improve the thermal shock resistance,and optimize the microstructure of specimens;（ 3） the mullitization of andalusite was not obvious in the castables fired at 1100-1400℃.

Development of Andalusite Bricks for Hot Blast Stove

Low-creep andalusite bricks are characterized by high refractoriness under load, good anti-creep property, high mechanical strength, low porosity, good thermal shock resistance, etc. In this study, low-creep andalusite brick specimens were investigated in the lab using mullite, bauxite and andalusite. Andalusite with the different particle sizes were used in the experiment and the specimen with the best property was selected us the production standard. In addition, the industrial produced low-creep andalusite bricks were compared with other low-creep bricks. The results show that the developed low-creep andalusite bricks is an excellent material for hot blast stove.

Kyanite Sillimanite and Andalusite

1 Scope This standard specifies classification, symbol, brand,technical requirements, test methods, inspection rules,packing, marking and quality certificate of concentratedkyanite, sillimanite and andalusite. This standard is applied to the beneficiated kyanite,sillimanite and andalusite used for high quality refracto-ries, technical ceramics and Si-Al alloy.

Effect of Andalusite Addition on Properties of Chrome-corundum Bricks

In order to improve the thermal shock resistance of chrome-corundum bricks,different amounts of andalusite were added to the formulation of chrome-corundum bricks to replace the equivalent white fused corundum with the same particle size.After mixing,shaping,drying and firing,the density,the cold strength,the cold wear resistance,the hot modulus of rupture and the thermal shock resistance were tested.XRD,SEM and elemental surface scanning were used to characterize the specimens.The results show that:(1)the volume expansion of andalusite mullitization reduces the apparent porosity of chrome-corundum bricks;(2)the density and the hardness of mullite are lower than those of corundum so the decrease of the corundum content in brick leads to the decrease of the bulk density,the strength and the cold wear resistance;(3)the cross-distributed columnar mullite in the matrix can effectively improve the hot modulus of rupture and the thermal shock resistance of the specimens;(4)considering comprehensively,the andalusite addition shall not exceed 18%.

QUANTUM CHEMISTRY ON FLOTATION BEHAVIOR OF KYANITE－GROUP POLYMERPHOUS MINERALS

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Influencing Factors of Properties of Castables for Hot Blast Stove Pipes

In order to prolong the service life of castables for hot blast stove pipes,effects of SiO2 micropowder addition and aggregate kind on properties of castables for hot blast stove pipes,and properties of silica sol bonded castables were researched using homogenized bauxite,andalusite particles,andalusite fines,white fused corundum fines,α-Al2O3 micropowder,pure calcium aluminate cement,SiO2 micropowder,and silica sol as starting materials. The results show that：（1） as SiO2 micropowder addition increases,the shrinkage rate of fired specimens increases; BD increases firstly,reaches the highest at 4 mass%,and then decreases; CMOR and CCS of all specimens increase gradually; so the appropriate SiO2 micropowder addition is 4 mass%;（2） the specimens with bauxite aggregate have better CCS and volume stability,but specimens with andalusite aggregate have better thermal shock resistance;（ 3） for castables for hot blast stoves using silica sol as binder,the addition of pure calcium aluminate cement can decrease the linear change rate after treatment at 1 400℃ and can slightly enhance CCS and CMOR,but has very little influence on AP and BD; and the introduction of citric acid worsens the thermal shock resistance of specimens.

Development of Thermal Shock Resistant and Low Creep Bricks for Hot Blast Stove

The paper describes the ries with high thermal shock development of brick seresistance and low creep rate for hot blast stove, including research target and research plan on the basis of analysis on how to enhance the thermal shock resistance and to lower creep rate of the bricks. Efforts have been made on the selection of starting materials such as corundum, mullite, andalusite and sillimanite etc., together with some measures taken on multi-grade formulation, homogenizing of the matrix of bricks and addition of some special additives. The results indicated that the bricks were with characteristics such as higher thermal shock resistance of 〉 30 cycles under quenching in water from 1000℃, and creep rate of 0. 2 under 1400℃ for 20 -50hrs with load of 0.2 MPa. Now a series of products of this kind have been developed and produced. The application of the products in Wuhan Iron and Steel Co. showed very prospective results. Now most of domestic large sized blast furnaces say ≥- 1000m^3, including those of Baoshan Iron and Steel Co. , have selected the series products made by Gongyi No. 5 Refractories Head Factory（GYWN） for their hot blast stoves.

Characteristic mineralogy of the Zhutishi granite:Implication for petrogenesis of the late intrusive granite

Many late intrusive granites with strongly peraluminous composition and fine-grained tex-ture occur as stocks or apophysis in the Dadongshan main intrusive granite located in NW Guang-dong Province. This paper reports the results of a petrogenetic study of some characteristic minerals (zircon, muscovite and andalusite) from the Zhutishi granite, one of the late intrusive granites in the Dadongshan granite. It is observed that the typological pattern of zircon population in the Zhutishi granite differs significantly from that in the Dadongshan granite, and that muscovite and andalusite, only found in the Zhutishi granite, are of magmatic origin. Therefore, this paper considers that the Zhutishi granite was unlike to be produced through crystal fractionation from the Dadongshan granitic magma as reported by previous authors, but is related closely to the formation of the Dadongshan granite. The hydrothermal fluid, produced by differentiation of the Dadongshan granitic magma at deep magmatic chamber, would penetrate into the source rock of the Zhutishi granite, and make it enriched in H2O and Al2O3; and the decompression after the ascent of the Dadongshan granitic magma in extension regime promotes partial melting of the source rock of the Zhutishi granite, and produces the strongly peraluminous granitic magma. The model proposed in this paper seems to be more reasonable to explain the spacio-temporal relationship between the late intrusive granites with strongly peraluminous feature and the main intrusive granite with metaluminous feature.

Sintering Densification Mechanism of Talc on Promoting Thermal Storage Andalusite Ceramics in Solar Thermal Power Generation

Mullite ceramic,as one of high-performance thermal storage ceramics for solar thermal power generation systems,was in-situ fabricated with talc as a sintering aid via semi-dry pressing and pressureless sintering in air.The mullitization influence of talc as a sintering aid on the formation of andalusite was investigated,and its mechanism to promote the sintering densification of samples was analyzed.The results show that talc reacts with corundum at a low temperature to in-situ produce cordierite.Cordierite reacts in-situ to produce mullite and glass phase,which reduces the sintering temperature sharply when corundum reacts with rich silicon fluid directly and generates secondary mullite.Cordierite resolves and produces magnesium oxide liquid phase,which contains active aluminium oxide lattice capable of reducing reaction activation energy and promoting remaining corundum to react with rich silicon fluid and produces secondary mullite.