A one-dimensional adiabatic mathematical model was developed for the riser reactor of an industrial residue fluid catalytic cracking unit (RFCCU). A seven-lump kinetic model was presented for the catalytic cracking of vacuum residue, taking cognisance of diffusion resistance, which is a departure from the general norm in the literature. Also, heat transfer resistance between the fluid and solid phases was incorporated into the energy balances for instantaneous and one-dimensional vaporization of feedstock. The developed model was a set of twelve coupled, highly non-linear and stiff ordinary differential equations, ODEs, which was numerically solved with an implicit MATLAB built-in solver, ode23t, designed deliberately for handling stiff differential equations to circumvent the problem of instability associated with explicit methods. An excellent agreement was achieved between the industrial RFCCU plant data and the simulated results of this study, with average absolute deviation being < ± 5% for instantaneous vaporization of feedstock in all cases investigated. Moreover, the simulated results revealed that half of the reactor was relatively redundant as this accounted for only 3% of the conversion. Hence, the findings of this study could be useful to the production practice for the Khartoum Refinery Company.

The optimal process conditions for the preparation of activated carbon from bean husk were investigated in this study. Four chemical activating agents; potassium hydroxide (KOH), sulphuric acid (H2SO4), zinc chloride (ZnCl2), and ortho-phosphoric acid (H3PO4) were used to activate the carbon. The influence of these agents on the surface area and porosity of activated carbon was determined. The Iodine numbers of 894.65, 1027.69, 1218.24 and 1256.31mg/g were found for the KOH, H2SO4,ZnCl2 and H3PO4activated carbons respectively. This indicates that the one prepared using ortho-phosphoric acid (H3PO4) produced the best activated carbon. The influence of activation temperature was studied between 500 o C and 900 o C. The effect of activation temperature shows an optimum temperature of 700 o C at the time of 30mins. Further studies revealed that the best impregnation ratio of carbon to ortho-phosphoric acid was 10:5as it gave a maximum iodine number of 1288.926.The results of the characterization show that the values of apparent density, ash content, moisture content and pH of the activated carbon fall within the range recommended by ASTM. This activated carbon is suitable for the treatment of effluent water and gases.

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The kinetics of the reforming of n-heptane on a platinum/alumina catalyst has been studied in a pulse microcatalytic reactor at a total pressure of 391.8 kPa over a relatively wide temperature range of 420 ı C-500 ı C. The differential and integral methods were used for the kinetic analyses of the reforming reaction. Twenty-nine reaction rate equations of the Langmuir-Hinselwood-Hougen-Watson type, based on molecular and atomic adsorption of hydrogen, were developed. Parameter estimates for the n-heptane reforming reactions were obtained by application of the Nelder-Mead simplex optimization technique to the predicted and observed conversion/production rates of the reaction components. Discrimination among rival kinetic models was based upon physicochemical criteria, analysis of the residuals, and statistical and thermodynamic tests. The rate-determining step was found to be the surface reaction of adsorbed iso-heptane to adsorbed methylcyclohexane with dissociative adsorption of hydrogen on the catalyst surface during dehydrocyclization of iso-heptane to methylcyclohexane. Hence, the surface reaction on the metallic function is ratedetermining for the n-heptane reforming on the Pt/Al 2 O 3 catalyst.