Spray apparatus design

An apparatus for reducing and controlling the temperature of superheated steam. Typically, a spray attemperator design is employed. 

The design of central as well as peripheral elements of spray fluidized bed equipment has been discussed in considerable detail by Jacob (2007), so that it is sufficient to give here a brief summary before focusing on some special aspects of apparatus design with high relevance for product quality. 

American physicist Robert A. Millikan and his student Harvey Fletcher designed an experiment to determine the charge on the electron. As shown in Figure 2-14. the apparatus was a chamber containing two electrical plates. An atomizer sprayed a mist of oil droplets into the chamber, where the droplets drifted through a hole in the top plate. A telescope allowed the experimenters to measure how fast the droplets moved downward under the force of gravity. The mass of each droplet could then be calculated from its rate of downward motion. 

In most types of separation equipment such as packed or spray towers, the interfacial area that is effective for mass transfer cannot be accurately determined. For this reason it is customary to report experimentally observed rates of transfer in terms of transfer coefficients based on a unit volume of the apparatus rather than on a unit of interfacial area. Such volumetric coefficients are designated as Kca, kLa, etc., where a represents the interfacial area per unit volume of the apparatus. Experimentally observed variations in the values of these volumetric coefficients with variations in flow rates, type of packing, etc., may be due as much to changes in the effective value of a as to changes in k. Calculation of the overall coefficients from the individual volumetric coefficients is made by means of the equations... 

Figure 156 shows three compartments of a multicompartmental design. Powder is metered into the first chamber and the same amount of liquid binder is sprayed into each chamber. Drying and dust collection take place in each compartment. Dust from the cyclone is recirculated to the last chamber. In equipment of this kind, narrow product size distributions can be obtained without the need for screening. For example, in a nine-compartment apparatus crystallized urea (0.2-0.5 mm) has been converted into a product featuring 92% between 1 and 3 mm. 

AATCC Test Method 35 -2000 " is designed to simulate a rain event. A special apparatus is used to hold the 20 x 20 cm fabric sample in a vertical position backed by a weighed piece of blotter paper. The fabric face is sprayed with water under constant hydrostatic pressure for 5 min and the blotter paper reweighed. The increase in weight of the backing paper is a measure of the resistance of the fabric to penetration by the simulated rain. 

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