Condenser appraisal

Condensation produces strong sulfuric acid from H20(g)-laden, weak [SO3 + H2S04(g)] (2-3 volume%) gas. This makes it indispensable as the last step in treating S-bearing hydrocarbon wastes and moist S02-bearing sulfide concentrate hearth roaster exit gases. 

It is also used to treat gases containing 6.5 volume% [S03(g) + H2S04(g)]. However, these gases can also be treated by conventional acidmaking so that condensation is not indispensible. 

Gases containing much more than 6.5 volume% [S03 + H2S04(g)] cannot be treated by condensation because the acid dewpoint temperature of these gases is quite high, e.g., 270-300 °C. The materials utilized in the WSA condenser are less suitable at these high temperatures. 

The proposed WSA-DC process overcomes these limitations by using two acid condensation steps (Rosenberg, 2009). The first WSA-DC plant is expected to start-up in China in early 2014. 

The first major step in wet sulfuric acidmaking is 802 + 0.502 SO3 oxidation. It is similar to dry gas SO2 oxidation, but with physically stronger catalyst. 

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Interaction of the noble gas atom with condensed matter is considerably more complicated and is usually approximate simply by summing or integrating potentials pairwise. Such treatments are necessarily crude nevertheless, they allow an appraisal of the general features of an interaction and often provide realistic numerical values as well. Young and Crowell (1962), for example, review theoretical treatments of noble gas adsorption along these lines predicted potentials for adsorption on various forms of carbon, to consider one example, range from a few hundred calories per mole for He to a few kilocalories per mole for Xe, in reasonable agreement with observed heats of adsorption. 

In a critical appraisal of the different methods for determining surface fractal dimensions, Neimark (1990) has stressed the importance of taking account of the different mechanisms of physisorption (e.g. at high p/p° the combination of multilayer adsorption and capillary condensation). Conner and Bennett (1993) have also warned of the risk of an oversimplistic interpretation of a linear log-log fractal plot. 

Vaporization in Vacnnm In 1882, Heinrich Hertz, at the age of 25, published a paper [19] dealing with a study of the vaporization rate of mercury in vacuum and a comparison of the experimental data obtained with theory. Hertz apparently recognized the difficulties encountered in a direct theoretical calculation of the vaporization rate (the experience accumulated over more than a century of research in this area is in agreement with this appraisal). Therefore he decided, instead, to calculate the maximum rate of the reverse process, i.e., the condensation of vapour. A theoretical analysis and comparison with the experiments conducted by Hertz led to two fundamental conclusions. First, every substance has a maximum rate of evaporation which is dependent only upon the surface temperature and the properties of the substance and, second, the maximum rate of evaporation cannot exceed the number of molecules from the vapour phase that are incident upon the surface of the condensate when equilibrium conditions are established. 

In early studies, it was natural to seek explanations of the processes in terms of the already well-confirmed mechanisms of gas breakdown such as collision ionization and streamer propagation. Since that time, the very considerable advance in understanding the electronic properties of the amorphous solid state offers opportunity for a much wider appraisal of the breakdown mechanisms of liquids. They are, as condensed phases, in many ways closer to the solid than to the gaseous state, at least through the initiatory stages of breakdown if not at the onset of final dielectric collapse. An important feature of the improved understanding is the possibility to consider in detail the electronic processes of an electro-chemical nature which are likely to occur at metal electrode-dielectric liquid interfaces. As will be discussed below, the processes at these interfaces play a vital role in breakdown initiation ... 

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