Columns with intermediate heat inputs/outputs

Figure 6.2. (a) A liquid profile for a column with direct split 1 2,3 with intermediate heat input and heat output (sohd fine), and for partially reversible column (dotted line), (b) Section trajectories for a column with intermediate heat input and heat output. 

Usage of nonadiabatic columns (i.e., column with intermediate at height inputs or outputs of heat), broadens conditions of separability of mixtures, having two reversible distillation traj ectory tear-off points. If, for example, heat is brought and drawn off in feed cross-section (Fig. 5.36), as it was offered in the work (Poellman Blass, 1994), then it is possible in one of the sections of the column, where there is limitation at the value of the parameter L/V or V/L, to keep the corresponding allowed value of this parameter, and joining of trajectories of the sections can be maintained at the expense of increase of vapor and liquid flows in the second section (Petlyuk Danilov, 1998). In a more general case, when there are limitations of the values of the parameters L/V and V/L in both sections, it is possible to use intermediate inputs and outputs of heat in the middle cross-sections of both sections. 

Columns with Intermediate Inputs and Outputs of Heat ... 

Therefore, the conceptual calculation of infinite column with intermediate input and/or output of heat consists in two stages (1) calculation of minimum reflux mode for adiabatic column, and (2) determination of opt 7, opt opt 7, and opt < 5, ( pinch method ). 

We examine the column with one intermediate input of heat in the bottom section and one intermediate output of heat in the top section. Figure 6.2a shows the change of internal liquid flows along the height of such a nonadiabatic column, depending on the value inverse to absolute temperature (7/T). Figure 6.2b shows the distillation trajectory of nonadiabatic column ... 

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