Agglomeration and defluidization

Compo, P., Tardos, G., and Pfeffer, R., Thermally Induced Agglomeration and Defluidization Characteristics of Fluidizable Particles, Proceedings of the Second World Congress in Particle Technology, Kyoto, Japan (1990)... 

M. L. Mastellone and U. Arena, Agglomeration and defluidization phenomena in a gas-solids fluidized bed operated with different liquid feedings. In Fluidization XI, U. Arena et al. (eds). Engineering Conferences International, New York, ISBN 0-918902-52-5, pp. 219-226 (2004). 

Agglomeration and Defluidization. Two possible problems arise (1) ground shale containing a sizeable fraction of 1/16-inch-or-less (1.6 mm) particles will segregate into coarse and fine layers, even under moderate fluidization conditions, and (2) the ground shale might become tacky, due to the presence of liquids on the shale surface under retort conditions, and defluidize by agglomeration. 

Tardos, G. and Pfeffer, R. (1995) Chemical reaction induced agglomeration and defluidization of fluidized beds. Powder Technology, 85, 29-35. 

Manzoori AR, Agarwal PK. Agglomeration and defluidization under simulated circulating fluidized-bed combustion conditions. Fuel 73(4) 563-568, 1994. 

As long as product is deposited within the micropores of the catalyst by capillary condensation only, there should be no problem, as the particle will behave as a dry one. Incipient wetness corresponds to a situation where hydrocarbon product starts to condense on the outer surface of the porous catalyst particle. This situation, which is characterized by the hydrocarbon dew point, marks the onset of particle agglomeration and defluidization. 

Compo, P., Pfeffer, R., and Tardos, G. I., Minimum Sintering Temperatures and Defluidization Characteristics of Agglomerating Particles, Powder Technology, 51(1) 87-103 (1987)... 

In a fluid bed petroleum coking unit, pitch is injected through nozzles submerged in the bed unless the mixing is good both locally near the nozzles, and in the bed as a whole, the coke already in the bed is agglomerated by the pitch and defluidization occurs. 

Compo (1987) also investigated the effect of temperature on the velocity required to prevent defluidization for (i) materials which agglomerated rapidly after their sintering temperature (Ts) was reached (coal, plastics, etc.), and (ii) materials which agglomerated slowly after reaching Ts (calcium chloride, etc.) For the rapidly agglomerating materials, the gas velocity had to be increased rapidly to prevent defluidization after Ts was reached. For the weakly agglomerating materials, a much smaller increase in gas velocity was required to prevent defluidization after Ts was reached. 

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