Thickeners high-rate

High-Rate Thickeners Flocculants are commonly used in thickeners, and this practice has resulted in thickener classification as either conventional or high-rate. These designations can be confusing in that they imply that there is a sharp distinction between the two. 

FIG. 18-87 Unit area vs. flocciilant dose, illiistrating the relationship between conventional and high-rate thickeners. 

The uniformity of film thickness is dependent upon temperature and pressure. The nucleation rate rises with pressure, such that at pressures above atmospheric the high rate of nucleation can lead to comparatively uniform oxide films, while increase in temperature reduces the density of oxide nuclei, and results in non-uniformity. Subsequently, lateral growth of nuclei over the surface is faster than the rate of thickening until uniform coverage is attained, when the consolidated film grows as a continuous layer ... 

Nitrome thane-Nitropropane-Thickener expl compositions having high rates of deton, but being non-cap-sensitive, are described. They were useful in marine seismic exploration work. For their prepn 800 lbs fertilizer-grade AN prills (previously ground to pass 10-mesh screen of which 22% passed 200-mesh) were intimately mixed with 104 lb MeNC>27 86 lb PrN02 ... 

However, the thermal decohesion time predicted for a craze layer which thickens at constant high rate still depends strongly on the cohesive stress. We now describe a method by which this parameter can be measured directly, and by which the impact lifetime of the craze can be measured and compared to the predictions of the model. 

Although the rate of corrosion may be regarded as high at the initiation of the process, for instance Mott and Bott [1993] noticed that corrosion sites on mild steel in contact with a simulated cooling water appeared within 3-4 hours exposure, it is likely that as the corrosion layer thickens the rate of reaction will decrease due to the barrier imposed by the deposit. Much will depend on the structure of the corrosion products, i.e. whether they are porous or compact. 

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