The reduction of FCCU afterburning through process optimization and regenerator revamping

Operating the fluid catalytic cracking unit (FCCU) in afterburning conditions can increase the regenerator temperatures above the metallurgical design leading to mechanical failures of the cyclones and plenum chamber. This paper presents the methodology applied in a commercial FCCU to investigate the afterburning causes and the technical solutions that can be implemented to reduce the afterburning. Thus, by evaluating the regenerator temperature profile, regenerator as-build design and the internals mechanical status, it was concluded that the main cause of afterburning was the non-uniform distribution and mixing of air and catalyst. The industrial results showed that optimizing the catalyst bed level, stripping steam, reaction temperature and equilibrium catalyst (e-cat) activity reduced the afterburning by 39%. Other process parameters such as feed preheat temperature, slurry recycling and excess oxygen did not have a significant influence on afterburning because of air and catalyst maldistribution. Revamping the regenerator to assure a symmetrical layout of cyclones reduced the afterburning by 86%, increased the fines retention in FCCU inventory and provided a better regeneration of the spent e-cat. The reduction of operating temperatures at around 701?C removed the risk of catalyst thermal deactivation and therefore the e-cat activity was increased by 10.2 wt.%.

Thermodynamics and kinetics of thermal deactivation of catalase Aspergillus niger

The thermal stability of enzyme-based biosensors is crucial in economic feasibility. In this study, thermal deactivation profiles of catalase Aspergillus niger were obtained at different temperatures in the range of 35°C to 70°C. It has been shown that the thermal deactivation of catalase Aspergillus niger follows the first-order model. The half-life time t1/2 of catalase Aspergillus niger at pH 7.0 and the temperature of 35°C and 70°C were 197 h and 1.3 h respectively. Additionally, t1/2 of catalase Aspergillus niger at the temperature of 5°C was calculated 58 months. Thermodynamic parameters the change in enthalpy ΔH*, the change in entropy ΔS* and the change Gibbs free energy ΔG* for the deactivation of catalase at different temperatures in the range of 35°C to 70°C were estimated. Catalase Aspergillus niger is predisposed to be used in biosensors by thermodynamics parameters obtained.

CFD model-supported design of monodisperse co-current spray dryers

In this study the operation of spray drying chambers fitted by the multi-stream monodisperse atomizer was simulated by the previously developed CFD model of skim milk spray drying. A series of CFD simulations of skim milk monodisperse spray drying were performed. The influence of different nozzle positions, initial droplet diameters (180 μm and 167 μm) and the way of air introduction (vertical or swirling with 30° or 60° angle) on the drying process were checked. Parameters like drying air and particle residence time, wall deposition, inter-particle collisions, protein thermal deactivation, air velocity and temperature profiles were compared for each case. Keywords: CFD, spray drying, skim milk, monodisperse atomizers, optimization.