Granules of aluminium

Table 5.2 Performance of Selected Dryers for Granules of Aluminium Alloy ...

Since wet purification methods are insufficiently effective, solid sorbents are used. The systems based on calcium and aluminium oxides and hydroxides are promising as such sorbents. A sorbent should provide a minimum gas dynamic resistance, therefore, it is produced as the granules of complicated shape. Sorbents based on lime and aluminium hydroxide are good fluorine absorbers. However, lime sorbents do not possess sufficient mechanical strength, while the use of aluminium hydroxide alone as a sorbent is limited by its high cost. 

The addition of aluminium powder in a form of foil, flakes oi granules can make slurry without nitro compounds. Tlte patent by I>avis, Fassnacht, Kirst and Noran [90] gives slurry explosives composed of ammonium and sodium nitrate, aluminium and water. An emulsifier is added to help the presence of air bubbles. Tlie fact that aluminium can react with the strongly oxidizing ingredients of the explo.sive mixture can be dangerous. 

Mkrolite (1) An expanded volcanic mineral, white spheroidal granules of a metastable amorphous aluminium silicate with a honeycomb, microcellular structure. 

However, the massive metal does not react with oxygen as long as it is covered by its natural oxide film, which forms spontaneously (see Section B.1.8). Only in the finely divided state, i.e. in the form of powder or granules, does aluminium burn spontaneously in contact with air or oxygen. The solid rocket boosters of certain rockets contain blocks of aluminium powder. 

The good resistance of aluminium to nitrate and ammonia environments makes it useful in production plants, namely for buildings, as internal cladding of granulation towers, etc. [2]. 

Aluminium is widely used in plastics and resin industries [22]. Since products of possible corrosion are white, aluminium neither stains nor modifies the surface appearance of plastics during their storage or transformation. Storage silos, tank trucks and tank wagons for polymer granules are made of aluminium alloys 5754, 5083, 5086, etc. 

The contact of aluminium with certain inorganic or organic products may lead to dangerous reactions, including explosion, splashes, etc. Several lists are available that include substances capable of producing such reactions with aluminium. In fact, a close analysis of such lists shows that there is very often a confusion between finely divided aluminium such as powder or granules and metal in the form of cast products or wrought semi-products sheet, plate, profiles, bars, tubes, etc. This distinction is very important. Here are a few well-known facts ... 

Certain products are excluded from the scope of the present book aluminium powders and granules, whose properties and uses have no relationship with the metallurgy and uses of aluminium in the form of castings or rolled, extruded or forged semi-products. Sintered aluminium powder (SAP) products, which have been studied since the 1970s, and aluminised steels are also excluded. 

An aluminium-mercury couple acts in the same way as zinc dust. This aluminium amalgam, prepared by the action of mercuric chloride on aluminium (preferably granulated), is also suitable for reducing substances dissolved in ether or alcohol the water which is required is slowly added drop by drop. (The method is that of H. Wislicenus.) The extent of the reduction varies according to the nitro-compound concerned, but corresponds approximately to the effect of zinc dust in a neutral medium. Consequently reduction usually does not proceed beyond the hydroxylamine stage. 

The suspension of crystals in sodium sulphite solution is pumped upwards by a rotary pump to a vacuum filter through a small tank in which the suspension is diluted with water. After the TNT has been separated from the liquor it is washed with cold water until its pink colour, produced during the sulphitation process, disappears. The aluminium filter plate in the filter bowl should be covered with linen cloth, which in turn is covered with a layer of pine, granulated TNT. 

After granulation has been completed, the nitrator contents are allowed to remain at rest for 12-15 hr, then without any dilution the spent acid are drawn off by means of an aluminium siphon. The spent acid is passed through an asbestos filter to retain any Cresilite granules carried away. 

X-ray microanalysis of thin cryosections of Anabaena cylindrica showed that aluminium was rapidly taken up and accumulated in PolyP granules (Pettersson et al., 1985). In addition, aluminium was found in the cell walls but could not be detected in the cytoplasm. The concentration of phosphorus in the medium affected the accumulation pattern. More aluminium was bound with PolyP granules and with the cell walls after growth in a Pj-rich medium. 

At present, the main industrial catalyst of ammonia oxidation is platinum and its alloys with aluminium and rhodium. Taking into account the deficit and high cost of platinum metals, the dcCTcasing of the consumption and losses of platinum metals is an urgent problem. Therefore, several compositions of complex oxide catalysts have been developed with iron (111), cobalt and chromium oxides as an active component. Complex oxides with perovskite structure are used as new catalysts they provide selective oxidation of ammonia with an yield not less than 90 %. The authors of [33] proposed to use perovskite powders LaMeOj, where Me=Fe, Co, Ni, Cr, Mn, and La,.,Sr,Me03, where Me=Co, Mn and x=0.25-0.75. To prepare these compounds, they used the precipitation by tetraethyl ammonia from diluted nitrate solutions taken at necessary ratios. The powders as prepared are poorly molded as in the form of honeycomb stractures as well as in the form of simple granules. 

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