Dry powder systems

FIra Supprassion Systams 4. 3.1 CO, Systems 4.2.3.2 Water Svstems 4.2.3.3 Dry Powder Systems 4.2.3.4 Halon Systems b. Faulty Indication... 

Using dry powders for the mitigation of airborne or liquid HF and other toxic materials is possible. The technique would work well where the maximum spill is known in advance so that stationary dry powder systems of finite, yet sufficient, capacity could be designed. 

Tornado dry powder system uses a hypersonic high shear system to ensure maximum dispersion without sample attrition. This system is stated... 

The use of aerosol delivery systems continues to be a desirable means of administering locally acting agents to the lungs. Since the early 1990s there has been a surge of interest in the pulmonary delivery of proteins and peptides for systemic activity but to date none of these products have made it to market [1], During this period the major commercial successes have been in the form of dry powder systems [2] and alternative propellant systems [1], as will be discussed later in the chapter. The incidence of asthma and chronic obstructive disease continues to rise and the need for improvement and diversity of therapies remains a priority in their treatment [3]. 

Dry Powder Systems Dry powder formulations are susceptible to a number of potential interactions. Since there is currently only one approved excipient, the drugs have to be compatible with lactose 4 In addition, dry powders are prone to moisture sorption, which can give rise to chemical degradation by hydrolysis or physical instability due to capillary forces.44 As other excipients, such as lecithin, are explored as excipients in dry powder products, a hydrophobic effect... 

A dry powder system comprises a container in which the powder is stored and which is connected to pipework leading to discharge nozzles in the protected area. On actuation of the system the powder is fluidised in the expellant gas (an inert gas such as nitrogen or carbon dioxide) and is conveyed to the nozzles. These systems are suitable for fires involving flammable liquids, electrical equipment or where water damage must kept to a minimum. They are not suitable in situations where Siere is likely to be a heat sink such that re-ignition could occur. Standards which cover dry powder systems are contained in BS EN 12416-2 2001. ... 

Latex Compounding. Latex compounding must take into account the stability of the latex both before and after compounding. Where consideration of soHds concentration permits, the additives are best predispersed in a compatible aqueous surfactant before addition to the latex. The volume of additives, especially if clay fillers are involved, may easily be enough to starve the system for soaps and flocculate the compound. On the other hand, dry powders or molten resins may often be added directly to the nonionic latex. 

The dry powder process has several additional advantages over the wet process. For example, much less waste of enamel occurs because the dry over-spray is airborne and recycled in a closed system. No-pidde ground coats have broadened the apphcation of both wet-process and dry-process systems. These enamels are appHed over cleaned-only metal. Thus the problems of disposing of pickling acid wastes containing iron sulfates and nickel wastes are eliminated (see Metal surface treatments) (7). 

The economics seem to be better for systems where dry powdered fresh hme plus ground recycled hme is injected along with a relatively coarse spray which impinges on and dries out from the reagent, as described by Stouffer et al. [Hs EC Res., 28(1) 20 (1989)]. Witnum et al. [9th Ann. Pitt. Coal Prep. Util. Euv. Control Contractors Conf. (1993)] describes an advanced version of that system that has been further optimized to the point that it is competitive with wet hme-stone scrubbing for >90 percent flue gas desirffurization. 

The most popiilar dry scrubbing systems for incinerators have involved the spray drying of hme slurries, followed by dry coUection in electrostatic precipitators or fabric filters. Moller and Christiansen [Air Poll. Cout. Assoc. 84-9.5 (1984)] published data on early European technology. Moller et al. [U.S. Patent no. 4,889,698 (1989)] describe the newer extension of that technology to include both spray-dryer absorption and dry scrubbing with powdered, activated carbon injection. They claim greatly improved removal of mercury, dioxins, and NOx. 

Using a closed charging system rather than pouring dry powders into flammable solvents directly via an open manhole... 

Figure A13.8 A dry painting system illustrating typical layout ol a medium-sized paint shop lor powder painting showing a seven-tank pre-treatment process...

Dry powders are effeetive on flammable liquid or eleetrieal fires. Speeial powders are available for use on metals. Dry powder extinguishers may be used on Class C fires, ineluding gases and liquefied gases in the form of a liquid spillage or a liquid or gas leak. This must be aeeompanied by other aetions, e.g. stopping the leak this is neeessary to avoid aeeumulation of an unburned flammable gas-air mixture whieh eould subsequently result in an explosion. Aetivation may be automatie by a deteetion system, or manual. 

Pressure 3.2.2.1 Piping Systems-Lined Pipe- Suppression Systems-Dry Powder... 

Taxonomy No. 4,2.3.3 Equipment Description PROTECTION SYSTEMS-FIRE- RRE SUPPRESSION -DRY POWDER ... 

Chiral salen chromium and cobalt complexes have been shown by Jacobsen et al. to catalyze an enantioselective cycloaddition reaction of carbonyl compounds with dienes [22]. The cycloaddition reaction of different aldehydes 1 containing aromatic, aliphatic, and conjugated substituents with Danishefsky s diene 2a catalyzed by the chiral salen-chromium(III) complexes 14a,b proceeds in up to 98% yield and with moderate to high ee (Scheme 4.14). It was found that the presence of oven-dried powdered 4 A molecular sieves led to increased yield and enantioselectivity. The lowest ee (62% ee, catalyst 14b) was obtained for hexanal and the highest (93% ee, catalyst 14a) was obtained for cyclohexyl aldehyde. The mechanism of the cycloaddition reaction was investigated in terms of a traditional cycloaddition, or formation of the cycloaddition product via a Mukaiyama aldol-reaction path. In the presence of the chiral salen-chromium(III) catalyst system NMR spectroscopy of the crude reaction mixture of the reaction of benzaldehyde with Danishefsky s diene revealed the exclusive presence of the cycloaddition-pathway product. The Mukaiyama aldol condensation product was prepared independently and subjected to the conditions of the chiral salen-chromium(III)-catalyzed reactions. No detectable cycloaddition product could be observed. These results point towards a [2-i-4]-cydoaddition mechanism. 

The use of a diesel-based concentrate with hydroxypropylguar gum has been evolved from the batch-mixed dry powder types [778], The application of such a concentrate reduces system requirements. Companies can benefit... 

Screening groups have experimented with several different solvent systems for manipulating and storing compounds. Solubilization of compounds in an organic solvent converts dry powders, oils and gums into liquids with more uniform properties that can be more readily and quantitatively transferred from container to container in massively parallel fashion with automated precision pipettors. Once... 

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