Melting state unsteady

About 40 - 60 minutes delay in the appearance of the maximum emission during the "cold" start-up of an SO2 oxidation reactor cannot be plausibly explained if only the absorption in the liquid melt phase is taken into account. This would require the "molar capacity" of the bed, C, of about 10 kmol / m. At such an assumption, the amount of SOg retained in the bed during the first 40 minutes of the start-up would correspond to the change in mass of the catalyst of 8 - 10%. Therefore, it seems little probable that it is solely the absorption of SOg in the bed which is responsible for such a considerable shift in the maximum emission in the unsteady state. 

If the melt is treated as a case of unsteady-state cooling directly (Fig. 4-7), the calculated cooling time is 13.86 s. This, of course, neglects the thermal effects of the heat of solidification. 

For unsteady-state processes, and in particular in injection molding, initial conditions are also needed, while the boundary conditions applied inside the mold must invariably take into account the interaction between the mold and the flowing and solidifying polymer melt. The variety of such conditions makes a full description beyond the scope of this chapter. The interested reader can find useful information in the manuals of custom-made commercial computer software, such as MOLD-FLOW [44], and in a recent thesis [20]. 

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