Impingement chambers

Note that the term geometry of the impingement zone refers only to the active fraction of the impingement chamber volume that contributes to the transfer processes. On the basis of numerous experiments, the limiting value of H/D below which the impingement zone can be considered to be active is 1.2 to 1.5. 

Interestingly, better drying performance (lower final moisture contents and higher volumetric evaporation rates) was found for ISD with a rectangular impingement chamber than for the cylindrical one that is commonly used in laboratory studies and industrial units (Cao and Liu, 2000). This effect can be attributed to a different flow pattern that results in improved heat and mass transfer. 

X-ray spectrometer An apparatus used in the X-ray study of crystals in which a fine beam of monochromatic X-rays impinges at a measured angle on the face of a crystal mounted in its path, and in which the intensity of the X-rays diffracted in various directions by the crystal is measured with an ionization chamber mounted on an arm of the spectrometer table, or is recorded photographically. 

Direct water spray cooling must be carried out with care. The spray chamber must be designed to ensure complete evaporation of all Hquid droplets before the gas enters the baghouse. Spray impinging on the chamber walls can result ia a dust mud iaside the chamber and any increase ia gas dewpoint may result in baghouse problems or atmospheric plume condensation. Spray nozzle wear can result in coarse or distorted spray and wetted bags, and water pressure failure can cause high temperature bag deterioration. 

Following each use the impingement mixing chamber is cleared by advancing a piston that eliminates the need for solvent flushing as is required for low pressure machines. 

Because the highest possible interfacial area is desired for the heterogeneous reaction mixture, advances have also been made in the techniques used for mixing the two reaction phases. Several jet impingement reactors have been developed that are especially suited for nitration reactions (14). The process boosts reaction rates and yields. It also reduces the formation of by-products such as mono-, di-, and trinitrophenol by 50%. First Chemical (Pascagoula, Mississippi) uses this process at its plant. Another technique is to atomize the reactant layers by pressure injection through an orifice nozzle into a reaction chamber (15). The technique uses pressures of typically 0.21—0.93 MPa (30—135 psi) and consistendy produces droplets less than 1 p.m in size. The process is economical to build and operate, is safe, and leads to a substantially pure product. 

Fig. 6. Approaches to minimising entrapment and impingement of fish and large aquatic invertebrates, eg, blue crabs, on trash screens at intakes, (a) An inlet pump house with vertical traveling screens mounted flush with a river shoreline to minimise obstmctions to animal movements (b) parallel flow to direct fish to a recovery chamber that returns to the water body (c) a velocity cap atop a vertical, offshore inlet induces a horizontal flow which fish avoid...

In the atomizing process, a stream of molten zinc is broken into tiny droplets by the force of a pressurized fluid impinging on the stream. The fluid can be any convenient material, although air is normally used. The atomized drops cool and soHdify rapidly in a coUection chamber. The powder is screened to specified sizes. Particulate zinc is also produced by other methods such as electrolytic deposition and spinning-cup techniques, but these are not of commercial importance. 

For proper use of the equations, the chamber shape must conform to the spray pattern. With cocurrent gas-spray flow, the angle of spread of single-fluid pressure nozzles and two-fluid pneumatic nozzles is such that wall impingement wiU occur at a distance approximately four chamber diameters below the nozzle therefore, chambers employing these atomizers should have vertical height-to-diameter ratios of at least 4 and, more usually, 5. The discharge cone below the vertical portion should have a slope of at least 60°, to minimize settling accumulations, and is used entirely to accelerate gas and solids for entty into the exit duct. 

FIG. 14-87 Charactersitic spray nozzles, a) Whirl-chamber hollow cone, (h ) Solid cone, (c) Oval-orifice fan. (d) Deflector jet. (e) Impinging jet. (/) Bypass, (g) Poppet, (h) Two-flnid. ( ) Vaned rotating wheel. 

Fluidized-bed opposed-jet mills Hosokawa Micron Powder Systems Div.) differ from the Majac mill in that powder is not fed into the jets, but the jets impinge into a chamber mich contains suspended powder. The powder is entrained into the jets. This ehminates wear on the nozzles, and reduces contamination. Otherwise, construction and appheations are similar to the Majac mill. The fluidized-bed level is maintained a few inches above the jets. The Fluidized-bed mill is available in 13 sizes with air volumes ranging from. 50 to 11,000 mVh. One application is for toner grinding. 

The part that marries the plasma to the mass spectrometer in ICPMS is the interfacial region. This is where the 6000° C argon plasma couples to the mass spectrometer. The interface must transport ions from the atmospheric pressure of the plasma to the 10 bar pressures within the mass spectrometer. This is accomplished using an expansion chamber with an intermediate pressure. The expansion chamber consists of two cones, a sample cone upon which the plasma flame impinges and a skimmer cone. The region between these is continuously pumped. 

PM Control - An impingement-plate scrubber is a vertical chamber with plates mounted horizontally inside a hollow shell. Impingement-plate scrubbers operate as eountercurrent PM collection devices. The scrubbing liquid flows down the tower while the gas stream flows upward. Contact between the liquid and the particle-laden gas occurs on the plates. The plates are equipped with openings that allow the gas to pass through. Some plates are perforated or slotted, while more complex plates have valve-like openings. 

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