Cracking catalysts expansion

Cracking catalysts are members of a broad class characterized by diameters of 30-150 im, density of 1.5 g/mL or so, appreciable expansion of the bed before fluidization sets In, minimum bubbling velocity greater than minimum fluidizing velocity, and rapid disengagement of bubbles. 

Cracking catalysts are included in a class of particles characterized by diameters of 30-150 pm and densities of about 1.5 g/mL. In these, there is appreciable bed expansion before fluidization sets in, minimum bubbling velocity is greater than minimum fluidizing velocity, and disengagement of bubbles is rapid. 

Over the years, the savings in petroleum resources have been enormous. In the U.S. alone, the zeolite cracking catalyst has saved the U.S. petroleum industry the equivalent of some 3.5 billion barrels (500 million tonnes) of crude oil since 1962. It lowered crude imports even more and enabled industry to produce higher gasoline volumes without additional investments in refinery expansion. 

Expansion of fluidized beds of sand and cracking catalyst. 

Expanders have not been the essence of reliability. It is not that the expander design in itself has any significant problems. The problems for the most part seem to be related to the application. Most of the failures have been the result of the expander ingesting foreign substances, such as the catalyst in a catalytic cracking unit heat recovery application. Unlike the expansion section of the gas turbine, the inlet temperature is not as high, therefore, temperature is not a significant factor in reliability reduction. 

Estimates of Model Parameters. The reactor models for FFB, MAT and riser include important features for translating the MAT and FFB data to steady state riser performance. A series of key parameters specific to a given zeolite and matrix component are needed for a given catalyst. Such key parameters are intrinsic cracking anc( coking activities (kj, A ), activation energies and heats of reaction (Ej, AHj), coke deactivation rate (exponents nj), and axial dispersion in the FFB unit (DA). Other feedstock dependent parameters include the inhibition constants (kHAj), the coking constants (XAj), and the axial molar expansion factor (a). 

The effectiveness factor is related to the Thiele modulus for different molar expansion modulus 0 [12]. The molar expansion modulus 0 expresses the intensity of the molar expansion, 0=(m-l),X R. Two simple cases may be considered, whether the cracking reaction is initially controlled by diffusion of reactants in the uncoked catalyst, or not. 

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