Continuously operated fluidized beds

Table 1 Summary of Experimental Conditions and Results of Reported CLSR Reactor Studies. BFB, Batch Fluidized bed CFB, Continuously Operated Fluidized bed FBR, Fixed bed Reactor...

Ryden et al. also used a continuously operated fluidized bed to test a NiO/ MgAl204 carrier (60/40 wt%) at a reactor temperature of 830°C-930°C [117]. They report complete conversion of methane with a H2 CO product ratio of 2, suggesting that in their case partial oxidation was the dominant reaction. Tests were conducted both with and without steam co-feed. Even without steam, a sustained period of... 

The three-phase continuous countercurrent fluidized-bed reactor and the spouted-bed reactor have been used on the laboratory scale. Pruden and Weber88 have shown that the countercurrent mode of operation for hydrogenation of a-methyl styrene performs better than the cocurrent fixed-bed operation under similar reaction conditions. 

Operating Conditions for Drying Some Vegetables in Continuous Centrifugal Fluidized Bed Dryer... 

Hanni PF, Farkas DF, Brown GE. Design and operating parameters for a continuous centrifugal fluidized bed dryer (CFB). J Food Science 41 1172-1176, 1976. 

Sasol produces synthetic fuels and chemicals from coal-derived synthesis gas. Two significant variations of this technology have been commercialized, and new process variations are continually under development. Sasol One used both the fixed-bed (Arge) process, operated at about 240°C, as weU as a circulating fluidized-bed (Synthol) system operating at 340°C. Each ET reactor type has a characteristic product distribution that includes coproducts isolated for use in the chemical industry. Paraffin wax is one of the principal coproducts of the low temperature Arge process. Alcohols, ketones, and lower paraffins are among the valuable coproducts obtained from the Synthol process. 

Suspended Particle Techniques. In these methods of size enlargement, granular soHds are produced direcdy from a Hquid or semiliquid phase by dispersion in a gas to allow solidification through heat and/or mass transfer. The feed Hquid, which may be a solution, gel, paste, emulsion, slurry, or melt, must be pumpable and dispersible. Equipment used includes spray dryers, prilling towers, spouted and fluidized beds, and pneumatic conveying dryers, all of which are amenable to continuous, automated, large-scale operation. Because attrition and fines carryover are common problems with this technique, provision must be made for recovery and recycling. 

Reactors may be operated batchwise or continuously, e.g. in tubular, tubes in shell (with or without internal catalyst beds), continuous stirred tank or fluidized bed reactors. Continuous reactors generally offer the advantage of low materials inventory and reduced variation of operating parameters. Recycle of reactants, products or of diluent is often used with continuous reactors, possibly in conjunction with an external heat exchanger. 

In fluidized-bed adsorbers, the combination of high gas rate and small adsorbent particle size results in suspension of the adsorbent, giving it many of the characteristics of a fluid. Fluidized bed adsorbers, therefore, lend themselves to truly continuous, countercurrent, multistage operation. Adsorbent inventory is minimized. 

Fluidized bed dryers work best on particles of a few tenths of a mm dia, but up to 4 mm dia have been processed. Gas velocities of twice the minimum fluidization velocity are a safe prescription. In continuous operation, drying times of 1-2 min are enough, but batch drying of some pharmaceutical products employs drying times of 2-3 hr. 

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