Pneumatic transport tube

Figure 1. Recirculating fluidized bed concept—draft tube operated as a dilute phase pneumatic transport tube.

Draft Tube Operated As A Pneumatic Transport Tube... 

Most of the applications for the recirculating fluidized bed with a draft tube operate the draft tube as a dilute phase pneumatic transport tube. Hence we will discussed this system in more details. 

Figure 7 Nuclear reactor Thetis dedicated to neutron activation analysis. View in the swimming pool with nuclear fuel element, Cerenkov radiation, safety and control plates and pneumatic transport tubes. (Reproduced with permission from Institute of Nuclear Sciences, Gent, Belgium.)...

Figure 4 Recirculating fluidized bed with draft tube operated as a pneumatic transport tube.

The schematic for this system, where the draft tube is operated as a fluidized bed rather than a dilute phase pneumatic transport tube, is shown in Fig. 5. A mathematical model for the system was developed by LaNauze (1976). The driving force for solids circulation in this case was found to be the density difference between draft tube and downcomer. The solids circulation rate was also found to be affected only by the distance between the distributor and the draft tube and not by the draft tube length or height of bed above it. Because of the lower velocity in the draft tube, the... 

Most of the applications for the recirculating fluidized bed with a draft tube operate the draft tube as a dilute phase pneumatic transport tube. Typical experimental pressure drops across the downcomer, AP1.4, and the draft tube, AP2-3, show that they are essentially similar. Thus successful design of a recirculating fluidized bed with a draft tube requires development of mathematical models for both downcomer and draft tube. 

Other industrial applications of the concept include that for coating tablets in the pharmaceutical industry (Wurster et al., 1965), for drying of dilute solutions containing solids (Hadzismajlovic, 1989), and for mixing and blending (Decamps et al., 1971/1972 Matweecha, 1973 Solt, 1972 Krambrock, 1976). Both Conair Waeschle Systems and Fuller Company supply commercial blenders based on the concept. The concept was also proposed as a controllable solids feeder to a pneumatic transport tube (Decamps et al., 1971/1972 Silva et al., 1996). 

In the riser tube, the gas velocity of chlorine, is greater than both of the terminal velocities of the slag particle and the petrocoke particle, makes the particles to be at a pneumatic transport state. No agglomeration occurs in the riser tube. At the top of the riser tube, a... 

The basic character of non-fluidized gas-particle flow is the existence of contact pressure (or stress) among particles and between particles and the pipe wall. Both theoretical analyses and experimental results (Terzaghi, 1954 Johanson and Jenike, 1972 Li and Kwauk, 1989) showed that the pressure of the interstitial fluid in particulate material neither compresses nor increases the shear resistance of the particulate material. After Walker (1966) and Walters (1973), Li and Kwauk (1989) analyzed the stresses in a vertical pneumatic moving-bed transport tube by using the stress theory of particulate media mechanics and Mohr circles, shown in Figs. 19 and 20, and gave the following stress ratios at any point in the flow field ... 

Pneumatic metal tubes of varying diameters operated by positive or negative air pressure used for light particulates (unloading bins and hopper cars and intraplant transport). 

Cohen, R.A. The pneumatic mail tubes New York s hidden highway and its development. Proceedings of the 1st International Symposium on Underground Freight Transport, Columbia, MO, Sep 2-3, 1999 Henry, Liu, Ed. University of Missouri-Columbia Columbia, MO, 2000. 

The re-usable fuel elements and the new fuel elements fed in by the input station are pneumatically transported to the core via the charge tube. Primary coolant at cold-gas temperature acts as conveying gas. 

S. N. Syrkin, Conditions of Pneumatic Transport along Tubes, Tsent. Kotlotmb. Inst. (1935). 

Sampling from pneumatic conveyors parallels gas sampling. The exception is that soflds loadings can be as high as 50 kg of soHds per kg of gas. Commercially available samplers extract particles directly from a transport line. Fixed position samplers are mounted directly on the pneumatic conveyor pipe. Devices are available which extract samples from the product stream by the projection of a sample tube iato the flow. Particles impact on the tube and fill the open cavity. The tube is then withdrawn, and an internal screw discharges the collected material (20). In another model, the RX Sampler (manufactured by Gustafson) (29), samples are withdrawn usiag compressed air. 

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