Untersuchungen an einer zirkulierenden Wirbelschicht mit Zentralrohr

Control mechanisms of fluidized solids circulation between adjacent vessels

“…In order to explain that shift, the data of Figure 5 have been replotted using a different abscis- hand side of the curves in Figure 5, as W, increases, is due to the increase in the rate of bypassed gas, passing from compartment 1 to compartment 2. The definition of the new abscissa shows that the bypass rate is about proportional to the circulation rate of solids, as obtained by Yang and Keairns (1978), and by Hofbauer (1983). From the analysis of the data presented in Figure 5, it is possible to explain in detail the mechanism which is responsible for the variation of the vertical resisting force in compartment 1.…”

“…These compact systems have the following advantages: Easy to obtain circulation Stable circulation rate of solids Real operating flexibility A great deal of experimental results have been published so far (Yang and Keairns, 1975,1978, 1983LaNauze and Davidson, 1975;LaNauze, 1976;Hofbauer, 1983; authors found that the circulation rate of solids could be controlled by the aeration rate in the upflowing compartment and by the area of the communication orifice. They developed an equation, based on the analogy of the flow of a liquid through an orifice, which could explain the results obtained with the fourcompartment cold model and predict the value of the circulation rate of particles within 40%.…”

“…What are the laws of variation of the resisting forces with 1983Escudero et al, 1985;Botton and Delcoigne, 1985;Ndenge, 1985, and Kuramoto et al, 1981. From the point of view of the hydrodynamic behavior, essential results have been obtained.…”

“…ing of the phenomena, the geometry of the circulating system The problem is even more complicated, since the existence of can be greatly simplified to its essential principle, as shown in a gas bypass, in the same direction as the circulation, has been Figure 1. The two compartments communicate at the bottom of found by almost all the authors (Yang andKeairns, 1978, 1983; the system through a rectangular orifice of height, f f f , and LaNauze and Davidson, 1975;LaNauze, 1976;Hofbauer, width, L. The particles flow over a partition plate at the top of 1983, and Kuramoto et al, 1981Kuramoto et al, , 1985. This bypass concerns the system.…”

“…They are used mainly for the gasification of coal and biomass, and they are generally made of several fluidized compartments. Examples of such concepts are the draft-tube (Yang and Keairns, 1975, 1978, 1983LaNauze and Davidson, 1975;LaNauze, 1976;Hofbauer, 1983;Judd et al, 1983Judd et al, , 1986Escudero et al, 1985, andButton andDelcoigne, 1985), the two-compartment auto-circulating fluidized boiler (Ndenge, 1985) and the fourcompartment reactor invented by Kunii (Kuramoto et al, 1981. These authors showed the existence of a driving force, of two kinds of resisting mechanisms, and of a gas bypass phenomenon.…”