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Spray dryer dispersion

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. [Pg.120]

Spray Dryers A spray diyer consists of a large cyhndrical and usu ly vertical chamber into which material to be dried is sprayed in the form of small droplets and into which is fed a large volume of hot gas sufficient to supply the heat necessary to complete evaporation of the liquid. Heat transfer and mass transfer are accomphshed by direct contact of the hot gas with the dispersed droplets. After completion of diying, the cooled gas and solids are separated. This may be accomplished partially at the bottom of the diying chamber by classification and separation of the coarse dried particles. Fine particles are separated from the gas in external cyclones or bag collectors. When only the coarse-particle fraction is desired for fini ed product, fines may be recovered in wet scrubbers the scrubber liquid is concentrated and returned as feed to the diyer. Horizontal spray chambers are manufactured with a longitudinal screw conveyor in the bottom of the diying chamber for continuous removal of settled coarse particles. [Pg.1229]

Pneumatic dryers, also called flash dryers, are similar in their operating principle to spray dryers. The product to be dried is dispersed into an upward-flowing stream of hot gas by a suitable feeder. The equipment acts as a pneumatic conveyor and dryer. Contact times are short, and this limits the size of particle that can be dried. Pneumatic dryers are suitable for materials that are too fine to be dried in a fluidised bed dryer but which are heat sensitive and must be dried rapidly. The thermal efficiency of this type is generally low. [Pg.432]

It was apparent from the very earliest tests that control of thin moisture films on the surface of reactive particles was the key to success. The main three competing arrangements, as compared by Statnick et al. [4th Annual Pitt. Coal Conf. 1987)] involved slurry spray dryers, where lime and water were injected together, versus systems where the gas was humidified by water injection before or after injection of limey dry powder reagents. It turns out that there are tradeoffs among the costs of hardware, reagent, and water dispersion and reagent purchase and disposal. Systems where water evaporates in the presence of active particles are usually less expensive overall. [Pg.44]

Microspheres by solvent extraction method were obtained with rate of mixing equal 300 rev/s. Particles by spray drying were produced with spray dryer operated with an inlet temperature of 50°C and outlet temperature of 45°C. The air flow indicator was set at 700 and the aspirator at 5. The polymer solution (concentration 0.5% wt/v) was supplied at 10 mL/min. The concentrations of monomer, initiator, and surfactant in ring-opening dispersion polymerization leading to microspheres were as follows [Lc]o = 2.77 10 mol/L, [tin(II) 2-ethyUiexanoate]o = 4.9 10 mol/L, [poly(DA-CL)] = 1.6 g/L. [Pg.272]

Figure 14-9 shows the spray dryer. This is a large cylindrical vessel with a conical bottom. Hot air enters at the top via a distributor. A concentrated solution of inulin in water is dispersed as small droplets. These are flung outwards by a spinning wheel, and dry rapidly in the hot air. The dry powder falls down and is collected at the bottom of the machine. The air flow leaves the dryer via a tube in the conical section powder carried by this flow is separated by a cyclone. [Pg.154]

Spray drying, one of these methods, is very suitable for the production of microc sules. In a spray dryer, an atomizer is used to form a spray of small droplets, which then mix with hot gases to evaporate the liquid from the droplets to form a dispersed, dry product. This dry product must then be separated from the exhaust gases. Figure I shows a schematic diagram of a spray dryer. [Pg.165]

Dilute This is a fully expanded condition in which the solids particles are so widely separated that they exert essentially no influence upon each other. Specifically, the solids phase is so fully dispersed in the gas that the density of the suspension is essentially that of the gas phase alone (Fig. 12-29). Commonly, this situation exists when the gas velocity at all points in the system exceeds the terminal settling velocity of the solids and the particles can be lifted and continuously conveyed by the gas however, this is not always true. Gravity settling chambers such as prilling towers and countercurrent-flow spray dryers are two exceptions in which gas velocity is insufficient to entrain the solids completely. [Pg.996]

Two-fluid nozzles do not operate efficiently at high capacities and consequently are not used widely on plant-size spray dryers. Their chief advantage is that they operate at relatively low pressure, the liquid being 0 to 400 kPa/m pressure, while the atomizing fluid is usually no more than 700 kPa/m pressure. The atomizing fluid may be steam or air. Two-fluid nozzles have been employed for the dispersion of thick pastes and filter cakes not previously capable of being handled in ordinary atomizers [Baran, Ind. Eng. Chem., 56(10), 34-36 (1964) and Turba, Brit. Chem. Eng., 9(7), 457-460 (1964)]. [Pg.1056]

Airborne mixing, e.g., fluidized beds and flash and spray dryers. Generally there is excellent mixing and mass transfer, but feed must be dispersible and entrainment and gas cleaning are higher. Mechanical vibration may also be used to assist solids movement in some dryers. [Pg.1367]

Figure 12-97 shows a traditional spray dryer layout with a cone-based chamber and roof gas disperser. The chamber has two-point discharge and rotary atomization. The powder leaving the chamber bottom as well as the fines collected by the cyclone is conveyed pneumatically to a conveying cyclone from where the product discharges. A bag filter serves as the common air pollution control system. [Pg.1417]

Gas flow and solids flow are usually cocurrent, one exception being a countercurrent flow spray dryer. The method of gas-solids contacting is best described as through-circulation however, in the dilute condition, solids particles are so widely dispersed in the gas that they exhibit apparently no effect upon one another, and they offer essentially no resistance to the passage of gas among them. [Pg.1419]

Spray Dryers 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. [Pg.90]


See other pages where Spray dryer dispersion is mentioned: [Pg.141]    [Pg.141]    [Pg.247]    [Pg.299]    [Pg.1229]    [Pg.1599]    [Pg.1898]    [Pg.211]    [Pg.278]    [Pg.761]    [Pg.8]    [Pg.139]    [Pg.150]    [Pg.417]    [Pg.1052]    [Pg.1052]    [Pg.1421]    [Pg.1657]    [Pg.761]    [Pg.2394]    [Pg.238]    [Pg.247]    [Pg.252]    [Pg.261]    [Pg.1417]    [Pg.1912]    [Pg.2377]    [Pg.96]    [Pg.29]   
See also in sourсe #XX -- [ Pg.2 ]




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