Pumpable dispersions

Suspended Particle Techniques. In these methods of size enlargement, granular soHds are produced direcdy from a Hquid or semiliquid phase by dispersion in a gas to allow solidification through heat and/or mass transfer. The feed Hquid, which may be a solution, gel, paste, emulsion, slurry, or melt, must be pumpable and dispersible. Equipment used includes spray dryers, prilling towers, spouted and fluidized beds, and pneumatic conveying dryers, all of which are amenable to continuous, automated, large-scale operation. Because attrition and fines carryover are common problems with this technique, provision must be made for recovery and recycling. 

Product diameter is small and bulk density is low in most cases, except prilling. Feed hquids must be pumpable and capable of atomization or dispersion. Attrition is usually high, requiring fines recycle or recoveiy. Given the importance of the droplet-size distribution, nozzle design and an understanding of the fluid mechanics of drop formation are critical. In addition, heat and mass-transfer rates during... 

Thinners and dispersants are used to prevent excessive flocculation of clay particles and maintain pumpability of the fluid. Tannins, various lignosulfonate salts, sodium tetraphosphate and other phosphates, and synthetic polymers such as sodium poly(styrene sulfonate-co-maleic anhydride) have been used. 

Non-dispersible concrete can be poured into a water-filled form without a tremie pipe to produce dense structural repairs. This type of material has particular advantages over conventional concrete both in terms of the quality of the repair produced and the reduction in placement cost associated with plant and diver manpower requirements. Field tests carried out on a commercially available AWA[46] show that bonding capability, pumpability and flowability around reinforcement are improved over conventional tremie-placed concrete. The quality and strengths of cores show AWA concrete to be suitable material for in situ structural concrete construction at considerable water depths [46]. 

Stocks containing 20-40% of the product range from soft to stiff pastes. Stocks of 10-15% are pourable, pumpable fluids. They are all easily handled and are readily dispersible in warm water. 

Acetylated lecithins have improved fluid properties, improved water dispersibility, and are effective oil-in-water emulsifiers for a wide variety of food formulations (56, 58). Moderately and highly acetylated lecithins are resistant to heat and can be repeatedly heated and cooled without darkening. The intended uses for minimally acetylated products are in infant foods, coffee whiteners, meat sauces, and gravies, and for oil-in-water cosmetic emulsions. Moderately and maximally acetylated products are used in cheese sauces, release agents in pumpable and aerosol formulations, and shortenings. 

Spray Diyers Spray drying is a drying process for transformation of a pumpable liquid feed in the form of a solution, dispersion, slurry, or paste into a particulate dried product in one single operation. The process comprises atomization of the feed followed by intense contact with hot air. 

Low-temperature pumpability requirements may become more demanding, and evolution of all chemistries to improve this performance area should be expected. As the automotive and additive industries continue to become more aware of the low-temperature properties of used engine oils, dispersant VI improvers may be designed to prevent the thickening which now occurs at extended mileages. In summary, VI improver developments for the foreseeable future are likely to be evolutionary and market-driven. 

The feed must be pumpable and dispersible into droplets. 

Spray drying is one of the most important continuous drying methods for the conversion of solutions, emulsions, or slurries into powders. The pumpable feed is dispersed into droplets which are dried in a controlled flow of hot gas. Particles are formed as moisture evaporates from each droplet. Particularly in regard to agglomeration, there is a fundamental difference between producing dry particles from solutions or emulsions and from suspensions or slurries. 

Uses Wetting agent, dispersant for solv.-based varnishes, esp. highly pigmented pumpable formulations Properties Brn. vise, clear liq. anionic 50% cone. 

Of the above liquid crystalline stmctures, the lamellar phase is the most important for food apphcations. As we will see later, these lamellar stmctures are very good stabilizers for food emulsions. In addition, they can be diluted with water, forming liposome dispersions that are easy to handle (pumpable liquids) and they interact with water-soluble components such as amylose in starch particles. Hexagonal and cubic phases, in contrast, when formed give problems in food processing due to their highly viscous nature (viscous particles may block filters). 

Liquid injection incinerators (also about 40% of U.S. hazardous-waste incinerator capacity) that bum pumpable liquid wastes dispersed as small droplets... 

Uses Leveling agent, dispersant for dyeing polyester fibers with disperse dyestuffs, fluorescent whitening of polyester fibers with disperse FWAs and dyeing the polyester component of polyester/cellulosic blends by the HT process Features Prevents filtration of dyestuffs does not inc. the AOX content of waste-water pumpable resist, to acids, alkali, salts, hard water Properties YIsh.-brn. Iiq. readily sol. in water dens. 1.0 g/ml (20 C) pH 4,0 (10%)... 

Uses Pitch dispersant, pitch control agent for use in thick stock to limit pulp defects and stock system deposition, for kraft and newsprint furnish systems Properties Cl, pumpable liq, si, odor sol. in water sp.gr. 1.18 pH 7 (1%)... 

The shear-thinning rheological behavior obtained through this weak coagulation may also be very important for pumpable castables in order to provide a certain cohesiveness to the material and avoid the typical shear-thickening tendency of fully dispersed concentrated systems. 

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