Atomizing nozzle performance

The Bechtel confined zone dispersion (BCZ) process involves the injection of a fine slurry mist of pressure hydrated dolomitic lime or calcitic lime, using two-fluid atomizing nozzles. A demonstration at the 70 MWe Seward Station of the Pennsylvania Electric Co., performed in 15.2 m of ductwork with a 2.4-m by 3.4-m cross section, achieved a 50% removal of SO2 at a Ca S ratio around 1.1. 

In the second configuration (moderate swirl) tested (see Fig. 20.2a), only the air stream was forced and no liquid-fuel pulsations were imposed. The experiments were performed with a Parker-Hannifan Research Simplex Atomizer. The atomizing nozzle consisted of a primary liquid ethanol feed with a coaxial primary air stream. The air stream passed through a set honeycomb, flow-straightener, and swirl vanes to provide the necessary level of swirl. Three loudspeakers were used to excite the primary air. 

Giffen (6C) and Mock and Ganger (ISC) present the effect of various operating parameters on fuel atomization in sprays. Applications of dimensional analysis to spray-nozzle performance data are discussed by Shafer and Bovey (23C). 

Viscosity affects nozzle performance, with higher viscosity fluids inhibiting atomization. Generally, fluids with viscosities greater than 100 cps are difficult to atomize unless another fluid like air or steam is provided. 

The physics governing the heat removal process by droplet sprays is very complex and still is not completely understood, and few theoretical models are available in the literature. Hence, it has turned out to be easier to investigate the various aspects of the problem by performing experimental work. Several studies have been conducted in the past on sprays, but most of them deal with the boiling regime, which was not considered in the present work. Air driven sprays obtained using atomizer nozzles are not considered in this study either because they would be impractical to use in a closed system for electronic cooling. 

For all atomizer designs the feedstock rheological properties will impact nozzle performance with the twin-fluid designs generally being less susceptible to a droplet size... 

Gas antisolvent processes can be performed in a semicontinuous mode. In this case the solution and the antisolvent are continuously introduced in the system until the desired amount of the product is formed. The introduction of the solution is then stopped and the DG flux extracts the residual solvent from the system. The system is then depressurized to enable collection of the product. The solution is generally introduced through an atomization nozzle that favors the prompt expansion of the solution and the formation of small particles. Different process configurations have been utilized, i.e., co- and countercurrent introduction of the solution and antisolvent fluxes and various nozzles have been designed. The process is referred to by different acronyms such as ASES (aerosol solvent extraction system), SAS (supercritical antisolvent), SEDS (solution enhanced dispersion by supercritical fluids), PCA (precipitation with a compressed fluid antisolvent), GASR (gas antisolvent recrystallization), GASP (gas antisolvent precipitation). 

Apparatus. The experiments were performed in a pilot plant consisting of a 1-ft. diameter, 15-ft. high AST reactor and its accessories. A schematic flow sheet of the pilot plant is shown in Figure 1. Details of the reactor and the auxiliary equipment were described earlier (1,9). Flashing atomization at 160°-220°C. and 400-1000 p.s.i.g., through small-orifice stainless steel atomizing nozzles was used in all tests described. 

Very similar to (24.94) and (24.95) suggests a similarity in rotary nozzle performance regardless of the mechanism Neglects liquid flow rate and liquid viscosity Atomization must occur by sheet formation Viscosity is considered conditions same as those of (24.94)... 

A cabinet performing such tests should be equipped with a solid-state humidity sensor reading the current humidity condition and a feedback controller. The mechanism that controls the humidity t5q3ically moves chamber air via a blower motor and passes it with an atomizer nozzle over a heater coil at the bottom of the chamber (Fig. 11.32). 

The transmitter and the receiver housing are mounted on a sensor carrier, which mechanically rigidly connects them to each other. Due to the U-shaped configuration of the sensor carrier, an influence of the sensor carrier on the sprays in the measurement volume is prevented. The sensor carrier is mounted on a linear axis system that provides an exact positioning of the measurement volume of the sensor in the sprays in two axes. The transmitter and the receiver module are sealed by mounted covers. Hence, the purging gas flows exclusively in the direction of the measurement volume out of the sensor modules. A relative shifting of the atomization nozzle, and the sensor carrier, is performed via a displacement of the nozzle. 

Advanced ceramics have a wide range of application (Figure 5.3). In many cases, they do not constitute a final product in themselves, but are assembled into components critical to the successful performance of some other complex system. Commercial applications of advanced ceramics can be seen in cutting tools, engine nozzles, components of turbines and turbochargers, tiles for space vehicles, cylinders to store atomic and chemical waste, gas and oil drilling valves, motor plates and shields, and electrodes for corrosive hquids. 

Machinery is a heterogeneous sector that puts all the properties of all thermoplastics to good use. Applications are very diverse, covering all types of functionalities and a broad diversity of shapes and forms, from miniaturized (nozzle of atomizer) to giant parts (combine harvester). Requirements can be severe needing high-performance mechanical, thermal, optical, physical or chemical properties obtainable with certain thermoplastics and thermoplastic composites. 

The spray nozzle (or nozzles) in the production machine would need to be of a size such that this increased spray rate is within its performance envelope (similar droplet size, uniform in distribution), or equivalence in granule size would be impossible. Figure 17 illustrates the concept that atomizing air pressure must be adjusted to attain similar average droplet sizes in all three scales of process equipment at the desired spray rate (data from... 

The main variables in the operation of atomizers are feed pressure, orifice diameter, flow rate and motive pressure for nozzles and geometry and rotation speed of wheels. Enough is known about these factors to enable prediction of size distribution and throw of droplets in specific equipment. Effects of some atomizer characteristics and other operating variables on spray dryer performance are summarized in Table 9.18. A detailed survey of theory, design and performance of atomizers is made by Masters (1976), but the conclusion is that experience and pilot plant work still are essential guides to selection of atomizers. A clear choice between nozzles and spray wheels is rarely possible and may be arbitrary. Milk dryers in the United States, for example, are equipped with nozzles, but those in Europe usually with spray wheels. Pneumatic nozzles may be favored for polymeric solutions, although data for PVC emulsions in Table 9.16(a) show that spray wheels and pressure nozzles also are used. Both pressure nozzles and spray wheels are shown to be in use for several of the applications of Table 9.16(a). 

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