Electrostatic charge effects

Consider a dilute gas-solid flow in a pipe in which the solid particles carry significant electrostatic charges. It is assumed that (a) the flow is fully developed (b) the gravitational effect is negligible and (c) the flow and the electrostatic field are axisymmetric. Derive an expression to describe the radial volume fraction distribution of the particles and identify the radial locations where the particle volume fractions are maximum and minimum in the distribution. Also, if the electrostatic charge effects are negligible, derive an expression to describe the radial volume fraction distribution of the particles. 

It has been confirmed by flood gun experiments, that the signal positions and peak shapes measured were not influenced by electrostatic charging effects. 

The effect of sedimentation was illustrated in an in vitro study in which a budesonide pMDI was delivered through two different spacers, Nebuhaler (Astra Zeneca, Sweden) and Babyhaler (GlaxoWellcome, UK) (Fig. 5). Both spacers are of similar length (200 mm) but have different diameters (80 versus 50 mm) both were primed before use to prevent electrostatic charge effects (see below). The total dose was increased in the wider spacer, mainly due to an increased coarse particle dose, and the half-fife of the fine particle fraction was longer (33 versus 23 s). 

For aromatic molecules of intermediate size these hydrophobic interactions seem to be more important than electrostatic charge effects, as has been concluded from work on soluble polymers [33]. However, it is also possible for hydrophobic interactions to become so strong that substrate and product molecules block the polymeric catalyst, and some observations of decreasing activity of catalyst with progressing reaction have been ascribed to this cause [1]. It has been noted that a similar effect may be caused by degradation (desulphonation) of the polysulphonic acid [1] or, as in Noller and Gruber s study of the decomposition of ethyl diazoacetate [19], by the accumulation of bubbles of a gaseous reaction product in the pores of the resin. 

Particularly in polar solvents, electrostatic charges usually have an important contribution to tire particle interactions. We will first discuss tire ion distribution near a single surface, and tlien tire effect on interactions between two colloidal particles. 

Antistatic agents require ambient moisture to function. Consequently their effectiveness is dependent on the relative humidity. They provide a broad range of protection at 50% relative humidity. Much below 20% relative humidity, only materials which provide a conductive path through the bulk of the plastic to ground (such as carbon black) will reduce electrostatic charging. 

As the filter accumulates dust, the pressure loss increases, and the dust removed improves the normal separation. Another effect can be seen with electrostatically charged filter material. During operation, the impurities neutralize the material, and the filter s capacity to separate is reduced. Figure 9.3" shows exam-... 

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