Calcination process

Ib/ft ). Again, dolomitic limes average about 4% denser than their high calcium counterparts. The severity of the calcination process largely determines the porosity of a quicklime the higher the temperature of calcination and the longer its duration, the more the porosity declines. 

Separation and Recovery of Rare-Earth Elements. Because rare-earth oxalates have low solubihty in acidic solutions, oxaUc acid is used for the separation and recovery of rare-earth elements (65). For the decomposition of rare-earth phosphate ores, such as mona ite and xenotime, a wet process using sulfuric acid has been widely employed. There is also a calcination process using alkaLine-earth compounds as a decomposition aid (66). In either process, rare-earth elements are recovered by the precipitation of oxalates, which are then converted to the corresponding oxides. 

Fig. 13. Combined dryer—calciner processes for sodium tripolyphosphate (a) cocurrent rotary dryer—calciner (b) countercurrent rotary dryer—calciner and...

Rdst-posten, m. roasting charge, -probe, /. calcination assay or test, -produkt, n. = Rosterzeugnis. -prozess, m. roasting process, calcination process, -reduktionsarbeit, /. (Metal.) roast reduction process, rostrein, a. rust-free. 

Engelhard s in-situ FCC catalyst technology is mainly based on growing zeolite within the kaolin-based particles as shown in Figure 3-9A. The aqueous solution of various kaolins is spray dried to form micR)spheres. The microspheres are hardened in a high-temperature l,3f)(TF/704°C) calcination process. The NaY zeolite is produced by digestion of the microspheres, which contain metakaolin, and mullite with caustic or sodium silicate. Simultaneously, an active matrix is formed with the microspheres. The crystallized microspheres are filtered and washed prior to ion exchange and any final treatment. 

Uchino and Azuma [504] developed and proposed a two-step calcination process of tantalum and niobium hydroxides to obtain oxides. The first treatment is recommended to be performed at 500-700°C, and the second- at 750-1000°C. It is reported that the above method ensures the production of oxides that contain only negligible concentrations of fluorine and silicon impurities. 

The first option is to improve the calcination process, usually by a two-step calcination. Other different mild template-destructive methods have been proposed. 

FIG. 10 SEM micrographs of (a) sUica nanoparticle/polymer [Si02/PDADMAC)3]-coated PS lat-ices and (b) hollow silica capsules. The hollow sUica capsules were obtained by calcining coated particles as shown in (a). The calcination process removes the PS core and the polymer bridging the silica nanoparticles, while at the same time fusing the silica nanoparticles together. Some of the silica capsules were deliberately broken to demonstrate that they were hollow (b). (From Ref. 106.)... 

In this work, effects of atmosphere during calcination process on photoactivities for decomposition of ethylene were investigated. TiOa were prepared by sol-gel and then calcined under Na plus increasing amounts of O2 at temperature 723 K. Conversion of ethylene increased with increasing sirface defect. Increasing this defect occurred when amount of O2 during calcination process increased. Surface defect of Ti02 samples was determined by CO2-TPD and ESR, while XRD, SEM, TEM and BET were used to characterize other physical properties of TiOa samples. 

In this work, effect of atmosphere during calcination process on surface defect was investigated using photocatalytic activity for oxidation of ethylene. CO2-TPD and ESR were used to determine this surface defect. 

The measured BET surface areas of titania samples were in the range of 99-116 m /g. It was found that surface area of titania decreased (as shown in Table 1) with increasing %02 during calcinations process whereas the crystallite size was apparently constant. 

Aurichalcite mineral calcined at 350°C was analyzed in greater detail because it contained both aurichalcite and ZnO phases, and thus represented an intermediate state in the calcination process. 

Calcining. In the calcining process, the lime mud removed from the white liquor is burned to regenerate lime for use in the lime mixing step. The vast majority of mills use lime kilns for this process, although a few mills now use newer fluidized bed systems in which the reactants are suspended by upward-blowing air. 

When gypsum, a sedimentary mineral (composed of hydrated calcium sulfate) is calcinated, most of its volatile constituent, water, evaporates and is therefore removed. The friable material remaining after the product of the calcination process cools down to ambient temperature is commonly known as plaster of Paris (composed of calcium sulfate hemihydrate) (see Textbox 33). 

Torma, V., Peterlik, H., Bauer, U., Rupp, W., Husing, N., Bernstorff, S., Steinhart, M., Goerigk, G. and Schubert, U. (2005) Mixed silica titania materials prepared from a singlesource sol-gel precursor A time-resolved SAXS study of the gelation, aging, supercritical drying, and calcination processes. Chemistry of Materials, 17, 3146-3153. 

FTIR spectroscopy of CO adsorbed at rt was used to monitor the state of platinum after the different calcination processes, i.e. at 500 and 300°C (Fig. 2A and B, respectively). Besides the broad band of the gaseous probe molecule, IR spectra of CO adsorbed on sample calcined at 500°C (Fig. 2A, a) showed the presence of a large band at ca. 2195 cm"1, accompanied by weak bands at ca. 2170 and 2100 cm 1, due to the presence of both platinum oxide species and Pt° clusters, whose formation is due to platinum autoreduction processes. The presence of large amounts of Pt° particles larger than 30 nm was observed by FIRTEM (data not shown). 

It is well know that the zeolite materials synthesized in alkaline systems usually have a high number of silanol groups (=SiOH) named defect groups [10] which possess a moderated Bronsted acidity [11]. Oppositely, Silicalite-1 synthesized in fluorine media are relatively defect-free [12] and the fluorine ions remain in the small cages of the MFI structure even after the calcination process [12]. The 29Si-NMR analyses carried out on samples Na-Silicalite-1 and F-Silicalite-1 confirm the presence of silanol groups only on the SI support surface (results not showed). Delaminated zeolites (ITQ-6) are obtained by exfoliation of as-synthesized lamellar precursor zeolites [13]. After this process, the final structure of the delaminated zeolite results in a completely hydroxylated and well-ordered external surface [13]. 

Coke which is low in sulfur and metal content is valued as a fuel, as a raw material for the manufacture of electrodes, and in graphite production. To produce high-purity coke, all traces of volatile matter must be removed from coke. A calcination process is utilized for this purpose. This process requires the coke to be heated to temperatures of 2,000°F (1,093.3°C) or higher. The pure coke is valued as raw material for the manufacture of electrolytic cell anodes and as a pure carbon source. 

Calx oxide of metal formed during calcination process... 

Aluminum nitride UFPs have been synthesized by thermal decomposition from many kinds of precursor such as polyminoalanef l/ ) AIH(NR)] (50), aluminum polynuclear complexes of basic aluminum chloride (BAC) or basic aluminum lactate (BAL) (51), and (hydroxo)(succinato) aluminum(lll) complex, A1(0H)(C4H404) jfLO (52). These precursors were calcined under N2 or NH, gas flow. The calcination temperatures, which depend on the individual precursor, can be lower by 600-200°C than the 1700°C in ihe conventional carbothermal reduction method. The XRD measurements at intermediate stages of the calcination process showed the phase change from an amorphous state to a trace of y-alumina with very fine grains and finally to wurtzite-type AIN (51,52). Lowering the calcination... 

Photocatalysis based on TiO has attracted much attention for enviromnental cleaning and antibacterial applications [1-3], In order to synthesize TiO nanoparticles, various modification of the sol-gel method have been widely used. However, sol-gel prepared TiO requires a post-calcination process for crystallization [4], which limits the applicability of TiO coatings to temperatnre resistant substrates. On the other hand, the solvothermal method, which does not need to be followed... 

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