Temperature Effect on Separation

As pointed out in the introduction to this chapter, it is helpful in understanding multistage separations to distinguish between two effects temperature and composition. (The other factors, such as pressure, number of stages, column configuration, etc., are assumed fixed in this context.) Of the two effects, the more predominant in distillation is temperature. In the case of binary distillation where the composition effect on the distribution coefficients may be neglected, the temperature is essentially the only factor. Under these conditions, the equations derived in Section 3.1.2 are applicable. 

If more stages are added, the temperature spread becomes wider and therefore separation becomes sharper. Also, as discussed further along, increased vapor rate from stage 2 to 1 and liquid rate from stage 1 to 2 results in a larger temperature difference between the stages and, hence, better separation. 

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