Mass stream overview

Fig. 1 Mass stream overview of a pulp and paper mill. The presence of some substances depends on the raw material, paper-making process, additives used and type of energy supply...

The general mass stream overview for the foundry process is given in Figure 3.1. This scheme generally applies for ferrous and non-ferrous foundries. Specific aspects of the various process steps and types will be woiked out below. 

Figure 3.1 Mass stream overview for the foundry process...

The bed surface, in the context of this section, is considered to be nonmobile porous material made of various size solid particles. The particles typically range in diameter from a few millimeters to less than a micron. The various bed types generally reflect the fluid dynamic nature of the water column above the bed. Table 12.7 contains typical porosity values for sediment. Section 12.2.1 contains an overview description of the types of aquatic streams and currents above the beds. These aquatic systems include rivers, lakes, estuaries, shelf, and marine environments. Unlike the air-water interface, the sediment-water interface has a single fluid (i.e aqueous phase) on either side. Water, the continuous phase, exists from within the column above, through the imaginary interface plane and into the porous bed where it is termed porewater. The interface plane is not a sharp one. It can be considered a thin mixed layer of finite thickness in the context of mass-transfer modeling (DiToro, 2001). Visual and physical examination of thin-sliced (0.1mm) layers of a frozen core sample from a lake sediment bed microcosm showed the presence of a finite flocculent layer positioned between the water side and the particles on the bed surface (Formica et al 1988). Little is known about this layer from a mass-transfer perspective, it will not be considered further. Mass transport in those bed surface layers at and below the first layer of solid particles will be the subject of this section. 

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