Agglomerates spherical

Subsequently, we will discuss effective rates of current conversion at the agglomerate level. Most commonly it is assumed that agglomerates in CCLs either comprise a homogeneous mixture of carbon/catalyst particles and perfluorosulfonated ionomer (PFSI) or that they consist of aggregated carbon/catalyst particles and water-filled pores which are coated on the external surface by a fihn of ionomer. These types of agglomerates represent the two limiting structures in terms of ionomer distribution at the mesoscopic scale, and both of them may exist simultaneously. 

Equation 8.2 can be used to determine the exchange current density (per unit 

The steady-state flux of hydrated protons in the agglomerate is due to diffusion and migration in the internal electric field. It is dictated by the Nemst-Planck 

We use the Bruggemann formula to relate the effective diffusion coefficient of protons in micropores, to the relative volume portion of micropores in 

The variation in local electrostatic potential is obtained from the Poisson equation. 

---

For approximately spherical agglomerates, compression strength is calculated as follows ... 

A process called spherical agglomeration closely resembles the sand-reduction process. Water is added to tar sands and the mixture is ball-milled. 

With the development of new instrumental techniques, much new information on the size and shape of aqueous micelles has become available. The inceptive description of the micelle as a spherical agglomerate of 20-100 monomers, 12-30 in radius (JJ, with a liquid hydrocarbon interior, has been considerably refined in recent years by spectroscopic (e.g. nmr, fluorescence decay, quasielastic light-scattering), hydrodynamic (e.g. viscometry, centrifugation) and classical light-scattering and osmometry studies. From these investigations have developed plausible descriptions of the thermodynamic and kinetic states of micellar micro-environments, as well as an appreciation of the plurality of micelle size and shape. 

Fig. 3 Intrinsic compressibility of nonagglomerated naproxen (control) and of naproxen that has been spherically agglomerated with different solvents. (From Ref. 21.)...

In this section three miscellaneous topics in the area of agglomeration shall be discussed, namely, dry pelletization, spherical agglomeration in liquid suspension, and spontaneous or inadvertent agglomeration of fine particles. 

Kawashima, Y., and Capes, C. E., Further studies of the kinetics of spherical agglomeration in a stirred vessel. Powder Technol. 13, 279 (1976). 

Since the ORR is a first-order reaction following Tafel kinetics, the solution of the mass conservation equation (eq 23) in a spherical agglomerate yields an analytic expression for the effectiveness factor... 

Examples of the kinds of fine solids that have been separated from suspension in the form of floes or spherical agglomerates include phosphate ore particles from water, calcium phosphate from phosphoric acid, soot from various aqueous process streams, coal particles from coal-washing slurry, and iron ore from aqueous tailings [324-326],... 

In Section 7.1 we show that the criterion for a spherical agglomerate breakup in viscous flow depends on parameter Z defined as ... 

In polymers crystallized from the melt, in most cases spherulitic structures are observed spherical agglomerates of crystals and amorphous regions, grown from a primary nucleus via successive secondary nucleation (Figure 4.18). The dimensions of the spherulites are commonly between 5 pm and 1 mm. When spherulites grow during the crystallization process, they touch each other and are separated by planes. In a microtome slice they show a very attractive coloured appearance in polarized light. 

Laboratory scale up to tons/hr, depending on application. Recovers particles directly from liquids. Can be selective in removing one or more particle types. Highly spherical agglomerates are possible. 

Fig. 2.9. Typical compressive strengths of various spherical agglomerates formed by tumbling.

Common practice to normalize the compressive strengths of spherical agglomerates of different sizes is to divide individual loads at failure by (pellet diameter)2 (cf. Section 4.1). This treatment of pellet strength data, however, assumes a uniform radial distribution of bonds within the agglomerates. That is, in the generalized relationship between load at failure and agglomerate diameter,... 

A simple example of immiscible liquid wetting is the addition of oil to a fine coal suspension to agglomerate and remove the carbon constituents while the inorganic impurities (ash constituents) remain in suspension and are rejected. A number of such coal cleaning processes, such as the Trent Process [3], the Convertol Process [4] and the Spherical Agglomeration Process [5], have been developed and used in this century. As discussed below, developments of the latter process have shown that many other applications are possible for immiscible liquid wetting. 

C.E. Capes, A.E. Mcllhinney, R.E. McKeever and L. Messer, Application of spherical agglomeration to coal preparation, Int. Coal Prep. Conf., Proc., 7th, Sydney, Aus., 1976. 

---