Powder cake, wetted

Individual chemicals may be so prepared or mixed to be suitable for use as either deflagrating or detonating explosives. Explosives find wide use as mining and constmction to blast ore, coal, and rock in petroleum prospecting and oil well production in manufacturing to bond metals and manufacture diamonds as pyrotechnics and in the aerospace Industry. Military explosives are used in demolition, ammunition, pyrotechnics, signals, and the like. 

In transportation terms, explosives are divided into six divisions (1.1 to 1.6) based on the (1) speed with which they react (2) sensitivity and modes of initiation (3) explosive power and (4) effects of the packaging or article to contain the explosive. 

Explosives are further assigned to one of thirteen compatibility groups (A through H, J, K, L, N, S) which identify the explosive article or substance and allow identification of other compatible explosives. 

A large number of chemicals, usually organic compounds of carbon, hydrogen, nitrogen, and oxygen, exhibit explosive properties  

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Powder cake, wetted or Powder paste, wetted with not less than 17 per cent alcohol by mass 0433... 

Powder Cake (Powder Paste), Wetted Substance consisting of nitrocellulose impregnated with not more than 60% of nitroglycerin or other liquid organic nitrates or a mixture of these. UN App. B, ICAO A2... 

A typical plot of torque versus amount of liquid (di-butyl-phthalate, DBT) added is given in Fig. 15 for a very porous sodium carbonate powder mixture. The increase in measured torque at around 25% by volume DBT and again at around 65 %, can easily be seen (the final decrease in torque upon the formation of the wet cake is not shown). These two points correspond to the condition under which the continuous network of bridges forms, at about 25% liquid present, and the formation of the dry paste, at around 65%, where enough binder is available to fill most internal voids. The amount of liquid in Fig. 15 is given as a fraction of the total volume of powder, instead... 

Further, the use of aqueous additive systems eliminates dust and compaction problems associated with the handling of powder form additives. Finally, the use of aqueous additive systems provides flexibility for mixing the additive with the resin. The additive can be mixed and dried with the resin still in moist, wet-cake form. It can be blended with other formulation ingredients, or pumped into an extruder or kneader during the compounding step. This flexibility can, in turn, provide still lower-cost processes and improved uniformity of mixing. 

Disposal of old or waste Zr powder which is packed either wet or dry in closed containers presents some additional hazards when attempts are made to open the containers. Particularly risky is the digging out of the Zr which may have settled. Whereas it is considered safe practice to douse or flood Zr fines with at least five parts of water, once the Zr has settled and caked, one cannot really assume that the metal is in contact... 

The starting material is a state-of-the-art flat y-alumina membrane prepared by dipcoating of a boehmite solution on a macroporous a-alumina support and subsequent firing at 600°C as described in [4], The a-alumina support is prepared from AKP-30 powder by making a colloidal suspension of this powder in diluted nitric acid and subsequent filtration. After filtration the wet cake is dried overnight and sintered for 1 hour at 1100°C. The resulting flat a-alumina supports have a mean pore diameter of 80 nm. A detailed description of the support synthesis is provided in chapter 4. 

In the last process step, the wet filter cake containing about 70% water was flash dried to a final water content of 2-5%. The powdered active carbon was collected in polyethylene bags which were sealed and stored in fibre drums. 

For foods and pharmaceutical products, the handling of slurries and solids at industrial scale presents problems where the product is exposed on filters and in dryers, rather than being enclosed within a pipe or vessel as a liquid. Contamination of the crystalline material can occur, and the product itself or the solvent phase it must be removed from might be toxic. Various types of equipment have therefore been developed to enable wet crystalline cakes and dry powders to be handled in a contained manner, using specially designed booths, isolators, and pack off systems to protect the product from its environment (and vice versa for highly potent materials). 

Lessons learned from paints and inks in achieving complete wetting of powders and separation of particles to micron levels with dispersion stability to forestall settling and caking are quite applicable to aqueous and nonaque-ous flowables. 

Drying. Hot air is blown over wet solids—for example, over a wet cake deposited in a filter or centrifuge. The water evaporates, leaving a dry solid product. Drying is the last step in the production of most crystalline products and powders, including many pharmaceuticals and food products. 

Instant foods. Lecithin has been used as a wetting agent and emulsifier in instant foods. Foods including cocoa powder, instant drinks, instant cocoa and flavored coffee, powdered protein drinks, coffee whiteners, instant puddings, cake mixes, and instant toppings are widely employed applications for specific lecithins. The most common method to incorporate lecithin is as an external coating on the powder particles. The particular lecithin to be employed largely depends on the hydrophilicity or lipophilicity of the powder system (7). 

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