Regenerators circulating fluidized

The fluidized bed reactor has been used for phenol removal instead of fixed bed as most of the products formed are insoluble. The operation in packed bed reactors would lead to clogging phenomena and undesirable pressure drop [47, 88]. When deactivation of biocatalysts occurs and regeneration is needed, the liquid-solid circulating fluidized bed is a worthy alternative, as demonstrated for phenol polymerization [89]. The continuous enzymatic polymerization was carried out in a riser section and a downcomer was used for the regeneration of the coated immobilized particles. 

Gamblin, B., Newton, D., and Grant, C. X-Ray Characterization of the Gas Flow Patterns from FCC Regenerator Air Rising Nozzles, in Circulating Fluidized Bed Technology IV (Amos A. Avidan, ed.), pp. 595-600. Somerset, Pennsylvania (1993). 

Most fluidized bed partial oxidation processes are operated in the turbulent flow regime of fluidization. However, DuPont operated a circulating fluidized bed catalytic reactor process for maleic anhydride production in Spain, featuring regeneration of the catalyst (by oxidation) on the downcomer side of the circulating system. 

Calcium oxide can act as a CO2 acceptor at higher temperatures than hydrotalcites. It reacts with methane and steam to form hydrogen and calcium carbonate (Reaction 11). Between 600 and 650°C, the CaO-CaCOa equilibrium lies at the carbonate side, which means that high methane conversions can be reached. To regenerate CaCOs, temperatures of900°C (at atmospheric pressure) to 1100°C (at 15 bar) are necessary (44). The process is carried out in circulating fluidized bed reactors. 

Chen, Z, Elnashaie, SSEH. Steady-state modelling and bifurcation behavior of circulating fluidized bed membrane reformer-regenerator for the production of hydrogen for fuel cells from heptane. Chem. Eng. Sci. 2004 59 3965-3979. 

In pilot-scale DMTO fluidized bed reactor, due to circulation of catalyst between reactor and regenerator, there exists a certain distribution of residence time of catalyst. Thus, the coke content on catalyst also shows a certain distribution, as shown in Fig. 7. But from Fig. 18, it is participated that, for a given temperature, an optimal value of coke content can be identified by which the selectivity to light olefins is maximized. Therefore, catalyst particles with coke content either higher or lower than the optimal value might lead to a lower selectivity to light olefins the overall selectivity is then affected by the coke distribution in DMTO circulating fluidized bed reactor. 

Golbig KC, Werther J. Selective synthesis of maleic anhydride in a riser-regenerator system. In Kwauk M, Li J, eds. Circulating Fluidized Bed Technology V. Beijing Science Press, 1996, pp 394-399. 

Many chemical processes recirculate solids. Catalytic systems recirculate catalyst in a reaction/regeneration cycle. First the catalyst is used to supply heat or a reactant to the process it is then transferred to a separate vessel to regenerate the catalyst, and then it is returned to the reactor. Circulating fluidized bed combustors recirculate fuel and ash around a loop to burn the fuel completely. A system with a cyclone collecting entrained solids above a fluidized bed and returning the solids to the bed via the cyclone dipleg is also a recirculating solid system. All of these recirculation systems employ standpipes. 

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