Particle Model (particle + model)

Distribution by Scientific Domains


Selected Abstracts


Recycling of nickel,metal hydride batteries.

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 9 2004
I: Dissolution, solvent extraction of metals
Abstract Nickel,metal hydride batteries contain valuable metallic components and although they are not considered a hazardous waste, recovery of these materials is necessary from an economic point of view. In this work a hydrometallurgical method for the dissolution and separation of the metals from cylindrical nickel,metal hydride rechargeable batteries was investigated. Hydrochloric acid was employed as the leaching agent to dissolve the metals from the batteries. Dissolution of metals was investigated as a function of acid concentration, leaching time and temperature. Suitable conditions for maximum metal dissolution were 3 h leaching with 4.0 mol dm,3 hydrochloric acid solutions at 95 °C. Extraction of 98% of nickel, 100% of cobalt and 99% of rare earth elements was achieved under these conditions. Separation of the rare earths from nickel and cobalt was preliminarily investigated by single batch solvent extraction with 25% bis(2-ethylhexyl)phosphoric acid. Efficient separation via complete extraction of the rare earths was obtained at a pH of approximately 2.5 while leaving nickel and cobalt in the raffinate. A shrinking particle model which can enable, under certain conditions, evaluation of the extent of metal dissolution present in nickel,metal hydride batteries was developed. A proposed electrochemical recovery of nickel and cobalt is also briefly discussed. Copyright © 2004 Society of Chemical Industry [source]


Estimation of Morphology Characteristics of Porous Poly(propylene) Particles from Degassing Measurements

MACROMOLECULAR REACTION ENGINEERING, Issue 2 2008
Marek Bobak
Abstract The transport of reaction species in polyolefin particles affects both the polymerization and the degassing of the powder in the down-stream processing. The morphology of particles , that is, the distribution of polymer and pore phases , predetermines their degassing behavior. We utilize gravimetric measurements to obtain the dynamics of degassing and to determine morphology characteristics of porous poly(propylene) particles. We found that Fick's diffusion model is not generally capable of fitting the shape of degassing curves of porous particles. Therefore we propose a particle model including two sizes of compact polymer granules and demonstrate that the degassing can be described by this model and that the model is capable of estimating fractions of large and small compact zones and the size of large compact zones. [source]


Effect of Reaction Conditions and Catalyst Design on the Rheological Properties of Polyolefins Produced in Gas-Phase Olefin Polymerization Reactors

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 9 2008
P. Pladis
Abstract A model is developed to predict the viscoelastic behavior of polyolefins produced in catalytic polymerization reactors. The approach is based on the solution of different sub-models (e.g., a kinetic model, a single particle model, a macroscopic reactor model and a rheological model). From the calculated rheological curve, the polymer melt index is determined. The ability of the proposed model to predict the viscoelastic behavior of linear polymer melts quantitatively is examined for the operation of a catalytic olefin polymerization cascade-loop reactor process. In addition, the transient rheological properties of polyolefins produced in a Ziegler-Natta gas-phase olefin polymerization fluidized-bed reactor are calculated. [source]


Electric-oxidation kinetics of molybdenite concentrate in acidic NaCl solution

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2009
Cao Zhan-fang
Abstract The electric-oxidation kinetics of molybdenite concentrate in NaCl electrolyte was investigated in this study. The effects of liquid-to-solid ratio, stirring speed, and concentration of NaCl on the dissolution rate were determined. It was found that the dissolution rate increases with increase in liquid-to-solid ratio, stirring speed, and concentration of NaCl. A shrinking particle model is presented to describe the dissolution and to analyse the data. The apparent activation energy of this dissolution process was found to be 8.2,kJ/mol; it was established that the leaching process is mainly controlled by diffusion, and the kinetics formula of this research system can be expressed as: . Dans cette étude, on examine la cinétique de l'oxydation électrique d'un concentré de molybdénite dans un électrolyte de NaCl. Les effets du rapport liquide-solide, de la vitesse d'agitation et de la concentration de NaCl sur le taux de dissolution ont été déterminés. Il a été découvert que le taux de dissolution augmente avec le rapport liquide-solide, la vitesse d'agitation et la concentration de NaCl. Un modèle de contraction de particule est présenté pour décrire la dissolution et analyser les données. L'énergie d'activation apparente de ce processus de dissolution a été évaluée à 8,2KJ/mol. Il a été établi que le processus de lixiviation est principalement contrôlé par diffusion et la formule cinétique de ce système de recherche peut être exprimée sous la forme: k,=,0,0207C exp(,8200/RT). [source]