Fluid bed conditions

As noted already, the bed particle size changes inversely with the intensity of fluidization. Hence reduced gas velocity increases granule size and coalesced structures are favoured, while layer growth and smaller particles result at high velocities. A lower limit exists for the gas velocity below which particle movement is inadequate and defluidization occurs. 

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TCS synthesis laboratory scale experiments generally yield higher TCS selectivities than do industrial reactors, because of the more defined conditions over the whole of the reacting silicon bed in the laboratory scale reactor. The TCS selectivity losses in the industrial reactor result from regions of imperfect fluid-bed conditions, with significantly increased temperature and significantly lower HCl flow rate than desired. 

Fluidized catalytic reactions have been industrially operated in the fluid bed conditions, but most of the research has been carried out for the teeter bed. Several studies of fluidized catalytic reaction are listed in Table VI, which are of interest in considering transport phenomena in fluidized catalyst beds. 

After drying in the spray tower, the detergent granules are conveyed to storage silos prior to carton packaging. In some processes, product storage is preceded by fluid-bed conditioning. 

Cyanopyridines are usually manufactured from the corresponding picoline by catalytic, vapor-phase ammoxidation (eq. 7) in a fixed- or fluid-bed reactor (28). 3-Cyanopyridine (25) is the most important nitrile, as it undergoes partial or complete hydrolysis under basic conditions to give niacinamide... 

Minimum Fluidizing Velocity U,nj, the minimum fluidizing velocity, is frequently used in fluid-bed calculations and in quantifying one of the particle properties. This parameter is best measured in small-scale equipment at ambient conditions. The correlation by Wen audYu [A.l.Ch.E.j., 610-612 (1966)] given below can then be used to back calculate d. This gives a particle size that takes into account effects of size distribution and sphericity. The correlation can then be used to estimate U, at process conditions, if U,nj cannot be determined experimentally, use the expression below directly. 

As mentioned in Section 2.2 (Fixed-Bed Reactors) and in the Micro activity test example, even fluid-bed catalysts are tested in fixed-bed reactors when working on a small scale. The reason is that the experimental conditions in laboratory fluidized-bed reactors can not even approach that in production units. Even catalyst particle size must be much smaller to get proper fluidization. The reactors of ARCO (Wachtel, et al, 1972) and that of Kraemer and deLasa (1988) are such attempts. 

If the new catalyst requires drastically different conditions, e.g. fluid bed operation instead of fixed bed operation, or if it needs substantial additions to the purification train, it is again possible to calculate the benefit in terms of the return (in reduced operating cost) on the new capital, but it is probably more informative to draw up a cumulative cash flow diagram. This is illustrated in Fig. 3. 

Minimum Fluidizing Velocity LO, the minimum fluidizing velocity, is frequently used in fluid-bed calculations and in quantifying one ol the particle properties. This parameter is best measured in small-scale equipment at ambient conditions. The correlation by Wen... 

In the butane route, a chemically complicated three-step process is needed to get from the feed to EDO. The two feeds, oxygen (air is used) and butane, are fed to a fluid bed reactor admixed with a catalyst. In a fluid bed reactor, the feeds and catalyst move continuously and, in this case, at a uniform temperature that allows optimum conditions for the catalyst to do its work. Butane and oxygen react to form maleic anhydride (MA), a cyclic compound. The fixed bed reactor effluent gases are taken off overhead, cooled, and filtered to remove entrained catalyst particles. The gases are then... 

Several laboratory studies have contributed to our understanding of turbulent chemical plumes and the effects of various flow configurations. Fackrell and Robins [25] released an isokinetic neutrally buoyant plume in a wind tunnel at elevated and bed-level locations. Bara et al. [26], Yee et al. [27], Crimaldi and Koseff [28], and Crimaldi et al. [29] studied plumes released in water channels from bed-level and elevated positions. Airborne plumes in atmospheric boundary layers also have been studied in the field by Murlis and Jones [30], Jones [31], Murlis [32], Hanna and Insley [33], Mylne [34, 35], and Yee et al. [36, 37], In addition, aqueous plumes in coastal environments have been studied by Stacey et al. [38] and Fong and Stacey [39], The combined information of these and other studies reveals that the plume structure is influenced by several factors including the bulk velocity, fluid environment, release conditions, bed conditions, flow meander, and surface waves. 

Experimental work to date confirms that the MTO process, which is an extension of fluid-bed MTG technology, has been scaled up successfully in a 4 BPD fluid-bed pilot plant at Mobil s Paulsboro Laboratory. Product yields and catalyst performance were nearly identical to those of bench top microunits. The process is currently being demonstrated in the 100 BPD fluid-bed semi-works plant in Germany. The plant was started up February, 1985 after completing modifications required to enable extended operation at MTO conditions. 

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