Dispersions sedimentation

Peptization is less important in the formation of natural colloidal solutions, inasmuch as conversion of the coagulant into sol again is characteristic of fresh highly dispersed sediments under the influence of special substances — peptizers. Peptization usually is observed when substances capable of forming sols act on sediments formed by coagulation of colloidal particles. 

Metal deactivator. Metal deactivator prevents precipitation of metal ion oxidation reactions and precipitation of insoluble metal compounds. Metal deactivator in combination with other antioxidants, shows strong synergistic effects. Oxygen and moisture present, diffuse through oil film and cause corrosion. Amine derivative, used in the additive has good water-displacing properties. They impede sludge formulation, disperse sediments and reduce corrosion in various fuel systems. 

In solid-liquid mixing design problems, the main features to be determined are the flow patterns in the vessel, the impeller power draw, and the solid concentration profile versus the solid concentration. In principle, they could be readily obtained by resorting to the CFD (computational fluid dynamics) resolution of the appropriate multiphase fluid mechanics equations. Historically, simplified methods have first been proposed in the literature, which do not use numerical intensive computation. The most common approach is the dispersion-sedimentation phenomenological model. It postulates equilibrium between the particle flux due to sedimentation and the particle flux resuspended by the turbulent diffusion created by the rotating impeller. 

Rutile from Tiwest The original powder contained sand and alumina. Sand was removed by a few dispersion-sedimentation cycles. Alumina was removed with hot 1.5 M HCL... 

The analysis of many technological processes involving dissolution, extraction, vaporization, combustion, chemical transformations in dispersions, sedimentation of colloids, etc. are based on the solution of the problem of mass exchange between particles, drops, or bubbles and the ambient medium. For example, in industry one often deals with processes of extraction from drops or bubbles or with heterogeneous transformations on the surface of catalyst particles suspended in a fluid. The rate of extraction and the intensity of a catalytic process to a large extent are determined by the value of the total diffusion flux of a reactant to the surface of particles of the disperse phase, which, in turn, depends on the character of flow and the particle shape, the influence of neighboring particles, the kinetics of the surface chemical reaction, and some other factors. 

The sediment samples used in the present study were obtained from Narragansett Bay. The sediment sample used for the PAH extraction study and in Experiments 1 and 4 was obtained adjacent to a pier in Narragansett, Rhode Island. The intercalibration sediment (ICS) was obtained near the north end of Jamestown Island (14). Recently contaminated sediments were produced by dispersing sediment obtained near the south end of Jamestown Island in seawater, dosing it with No. 2 fuel oil in a continuous flow oil-dosing system (15), and collecting it after it had settled to the bottom of the tanks. 

With regard to an effective use of catalyst it is necessary to realize a uniform distribution over the entire reactor. There are a number of experimental studies reported in the literature (1-5) which show that even for small particles well pronounced solid concentration profiles can be observed in the gas agitated bubble column slurry reactors (BCSR). A dispersion-sedimentation model has been proposed, which successfully describes measured data (2-4). 

The nonuniform catalyst distribution will be described by the dispersion-sedimentation model. 

The nonuniform catalyst distribution due to the settling of the particles is characterized in the balance equations by the variable ( ), which represents the ratio of the local solid concentration to the reactor mean value Ccat The catalyst concentration profile follows from the dispersion-sedimentation model (2-4). 

Dispersion/sedimentation model used for solid concentration profile others assume slurry as homogeneous phase. 

Colony forms an easily dispersible sediment in an exudate. 

Sediment difficult to disperse Sediment easy to disperse... 

---