Date of Award


Degree Type


Degree Name

Doctor of Philosophy


A pilot plant unit, namely Multicrackex, for the catalytic cracking of hydrocarbons with the riser and regenerator units under direct heat exchange conditions was designed, built and operated. The heat transfer process, between regenerator and reactor, was achieved by placing the riser reactor inside the regenerator, with an arrangement similar to the one of a bundle of tubes in a heat exchanger.;The regenerator of the Multicrackex unit had an outside diameter of 0.2667 m and a height of 3.25 m. The riser had an outside diameter of 0.0334 m and a total height of 3.460 m.;A two levels pseudo-factorial design was selected for the experimental program. Targeted factor levels were: (i) 580-730{dollar}\sp\circ{dollar}C temperature range in the regenerator, (ii) 1.5-4.0 s contact times, defined at riser entry conditions and (iii) 1.0-12.0 catalyst-to-oil ratios. A synthetic gas oil SF-135 (CANMET) and a commercial equilibrium catalyst, Octaboost 6XX Series (Akzo) were used during the operation of the unit.;Superimposing the experimental temperature profile inside the riser, reaction rate constants and activations energies, associated with three and four lumps models, were simultaneously evaluated with a high degree of precision ({dollar}\pm{dollar}7% average) and relatively low correlation.;It was successfully demonstrated that given heat transfer conditions, both endothermic effects of the cracking reactions and gas oil vaporization were substantially neutralized by the heat fluxes from the regenerator. Thus, the significant heat exchange was represented with a film coefficient assigned to the gas-solid suspension (riser side) of the riser-regenerator system. A heat transfer correlation was proposed to model this coefficient. Simulation results obtained from the simultaneous application of kinetic and heat transfer parameters were inside the {dollar}\pm{dollar}15 to 20% relative errors range.;Results obtained demonstrate that heat transfer conditions in the Multicrackex unit provide a unit of extreme flexibility. High temperature conditions can be selected to produce a high fraction of light gases with significant amounts of C{dollar}\sb3{dollar}-C{dollar}\sb4{dollar} olefin and a controlled coke yield. On the other hand, model predictions indicated that operating conditions can be adjusted to maximize gasoline yields at high temperatures and short contact times (about 150 milliseconds).;Consequently, heat transfer conditions between riser and regenerator made it possible to control selectivity to gasoline or light gases formation. Moreover, light gases fractions with high content of butenes were also obtained in encouraging amounts. These fractions are excellent feedstock for alkylation units and consequently for the production of reformulated gasolines.



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