Supported cobalt is one of the common catalysts used in Fischer-Tropsch synthesis (FTS). Strong electrostatic adsorption (SEA) was employed to synthesize cobalt nano particles supported on silica. Cobalt nitrate was used as the catalyst precursor and non-porous silica spheres, which were synthesized using the modified Stöber method, were used as a catalyst support. Point of zero charge (PZC) for silica was determined using equilibrium pH at high oxide loading (EpHL) method. The optimum pH was determined by measuring cobalt uptake versus pH. High cobalt uptake at basic pH and low cobalt uptake at acidic pH indicates electrostatic interaction between the cobalt complexes in the precursor solution and the hydroxyl group on the support’s surface. Catalysts prepared at optimum pH were characterized using TPR, XPS and TEM. TPR shows reduction peak at high temperature (587°C) indicating strong interaction between cobalt and silica support. XPS shows presence of Co2+ species on the surface. TEM images of the Co/SiO2 at 5 wt% and 10 wt% cobalt loadings show fairly well-dispersed cobalt oxide nano particles on the spherical silica support with narrow particle size distribution. The findings suggest that SEA was deemed a suitable method to prepare supported cobalt catalysts.

Kinetic Theory of Granular Flow (KTGF) has been successfully incorporated and widely implemented in the Eulerian simulation models in many multiphase cases. The KTGF theory involves many parameters and is applied in the multiphase simulation for the purpose of hydrodynamic properties modeling of the granular phase. This paper is focused on granular viscosity which is a parameter in the KTGF that incorporates three different viscosities arising from the inter-phase and intra phases interaction in a bubbling fluidized bed (BFB). The 2D BFB model of 0.2 m width and 0.8 m length having a 13-hole orifice plate has been modeled for this purpose. The model was constructed using Gambit software version 2.4.6 and then simulated using ANSYS Fluent version 14. Two models of granular viscosity, namely Syamlal-Obrien model and Gidaspow model, were compared based on its effect to the pressure drop and bed expansion of the BFB. The results depicted that the simulation based on Syamlal-Obrien model tends to produce larger bubbles and contributing to a higher pressure drop across the distributor plate as compared to the Gidaspow model.

The production of refinery sludge has been increasing during tank cleaning, deslugging, and wastewater treatment process. Many efforts have been done to manage the large amount of generated sludge. The gasification of sludge is the most versatile alternative or /and is one potential treatment process for power generation and syngas production. The thermodynamic of gasifier is still not well understood for refinery sludge feedstock. As far as optimising the operational conditions of gasification process is concerned, a successful simulated work is introduced by making use of ASPEN PLUS software simulator. This software was tailored and developed to describe an equilibrium model in updraft gasifier of dry refinery sludge (DRS). The textural characteristic properties of refinery sludge are shown in this paper (ultimate and proximate analysis). In the present study four parameters ( i.e. oxidation zone temperature, operating pressure, air flow rate (l/min) and equivalent ratio) were analyzed. In the present work, details of the equilibrium model are presented. This model shows a better agreement with literature model for biomass gasification. From our model results, the mass fractions yield of the desired products (CO and H2) increases as the oxidation zone temperature increases while their yield decreases after 3 bar. The desired products are found to decrease as the air flow increases while CO2 mass fraction favors high air/fuel ratio. The model results are validated by comparison with experimental data issued from the literature.