Airless drying

Air heating losses (to heat air through-flow from 20°C to 700 20 

Evaporation energy (from assumed 20°C ambient tempera- 2594 74 

In batch mode of operation, airless drying has three distinct stages. These 

Cool-down phase. When all liquid in the wet solid has been evaporated, a cool-down phase is initiated in which air is readmitted to the drying chamber to drive out the superheated vapor. 

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Stubbing [107] describes the use of drying at atmospheric pressure in a steamy environment, which he terms airless drying, with the tower density of the steam relative to the air being used to seal the chamber, so that the air is progressively displaced. A possible application in the drying of cloth is suggested. 

Stubbing, T.J. 1994. Airless drying. Proceedings of the Ninth International Drying Symposium. IDS 94, Gold Coast, Southeastern Queensland, Australia, Vol. A, pp. 550-566. 

Because of space limitations, this chapter discusses steam dryers only for a selected range of products. However, the references cited provide detailed information. Also, other chapters in this book include discussion of some steam-based drying technologies such as airless drying or solvent drying. 

Table 8.1 Energy Audit for Conventional and Airless Drying of Ceramic Materials in a Tray Dryer...

Stubbing TJ. Airless drying process saves energy and reduces emissions. Paper Technology June 36-39, 1990. 

Stubbing TJ. Airless drying Its invention, method and application. Trans. IChemE. Part A 71 (A5) 488-495, 1993. 

Stubbing TJ. Airless drying. In Drying 94. Proc. 9 Inti. Drying Symposium (IDS 94), Gold Coast, Australia, 1994b, pp 559-566. 

Stubbing TJ. Airless drying-development since IDS 94. Drying Technology 17(7 8) 1639-1651, 1999. 

Acrylated rubber These are based on styrene butadiene and have become commercially available only relatively recently. They are manufactured in several grades but most have the advantage over other materials in this class of being based on white spirit solvent rather than the stronger and more obnoxious xylol. In other respects, they are similar to chlorinated rubber and cost approximately the same, although they are easier to airless spray and the dried film contains less pores. They are considered to have superior weather resistance to chlorinated rubber and vinyl. 

In conventional spraying paint is forced under pressure to the spray gun, where it mixes with air and, forced through a small orifice, atomises. Airless spray is created by forcing paint at extremely high pressures through an accurately designed small hole. Rapid expansion as it leaves the gun produces an extremely fine and very even spray pattern. No air is mixed with the paint before it leaves the gun, so avoiding dry spray . A wetter, heavier... 

Neither roller nor brush is capable of attaining the same film thickness as airless spray. A paint which consistently gives 100/im dry-film thickness when applied by the latter means is unlikely to produce more than 75 m d.f.t. comfortably by roller or brush the more complex the geometry of a structure the more unlikely it is that consistent results will be obtained. 

Red lead primer in quick-drying Airless spray. 2 100-125... 

Note 5 In calculating paint requirements up to 50% more than the theoretical dry film weight requirement should be allowed to cover thick coatings, wastage, repairs, losses (typically 30% for air spray 15% airless spray 10% electrostatic spray 5% roller or brush) etc. Manufacturers should be asked to quote percentage volume solids in their paint to facilitate calculations. 

The finely divided cadmium may be stored for several months either as a slurry or in a dry state. (A dry 7 month-old sample was just as reactive as a fresh sample.) Strict anhydrous, airless conditions must be maintained, however. The cadmium crystallite sizes are variable but are generally in the 100-1000 A range. Particle sizes range up to several microns, with some particles even much larger. (Nontransition metals yield more nonuniform particle distributions than transition metals, which form stronger complexes with the solvent). 

The most widely used method of application in heavy industrial projects is airless spraying. This utilises high pressure, the liquid paint being ejected through a fine specially designed nozzle which causes the paint stream to break up into fine droplets in the form of a fan. This rapid method of paint deposition also allows application of high dry-film thickness with each coat, 150 /an being not unusual in this respect. A coat of "decorative paint applied by brush would probably yield a thickness of 30-40 fim. 

Heptathiazocine (1.4 g, 5.85 mmole) is dissolved in anhydrous diethyl ether (150 mL) in a 250-mL, three-necked flask. The solution is cooled to -78° (acetone-Dry Ice) under nitrogen and tetrabutylammonium hydroxide 7.5 mL of 25% solution in methanol, Eastman, 7.25 mmoles) in diethyl ether (12.5 mL) is added slowly. A yellow precipitate (sometimes with a greenish tinge) is formed immediately. The solution is kept at -78° and filtered through a coarse glass frit in a low-temperature filter funnel (Kontes, airless-ware). The greenish-yellow solid on the frit is transferred quickly to a dry box, and in the course of about 1 day it becomes a deep-purple solid. This solid contains elemental sulfur (x-ray... 

Fig. 34 Spray-dried plant extract solutions used to prepare readily soluble tea preparations. Spray-dried product from an airless high-pressure system leading to a coarse particle size distribution (A) and a magnification thereof (B), detailed view of one particle showing fragments inside (C), and the product from above after a wrong sample preparation (D).

To the polymer [NPCl2]2—[NP(CH3)(CH2SiMe3)] and the residual cyclic trimer, ge/n-N3P3Cl4(CH3)(CH2SiMe3), in an airless flask is added 300 mL of dry toluene (distilled over sodium benzophenone). This mixture is stirred under an atmosphere of dry nitrogen until the contents of the broken tube dissolve (3-4 hr). The toluene solution is then transferred to a 500-mL addition funnel under a nitrogen atmosphere via a double-tipped syringe needle. 

Caution. Benzene, hexamethylphosphorous triamide, and dichloro-phosphoranetriyltris[dimethylamine] are suspected carcinogens. The reaction should be conducted in a well-ventilated hood, and gloves should be worn at all times. The synthesis must be carried out in the absence of any moisture. Airless Schlenk ware and two-ended filters with side-arm gas inlets for filtration are recommended. Solvents should be dried rigorously. 

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