Distillation material balance

FIGURE 5.3-13 Tridiagonal matrix foratulation or multistage distillation material balances. A similar matrix is required for each component. 

Figure 12.110 Effect of feed rate feedforward on distillate (material balance scheme)...

Fig. 18. Separation of ethanol from an ethanol—water—benzene mixture using benzene as the entrainer. (a) Schematic representation of the azeo-column (b) material balance lines where I denotes the homogeneous and the heterogeneous azeotropes D, the end points of the Hquid tie-line and A, the overhead vapor leaving the top of the column. The distillate regions, I, II, and III, and the boundaries are marked. Other terms are defined in text.

Fig. 19. Separation of ethanol and water from an ethanol—water—benzene mixture. Bottoms and are water, B is ethanol, (a) Kubierschky three-column sequence where columns 1, 2, and 3 represent the preconcentration, azeotropic, and entrainer recovery columns, respectively, (b) Material balance lines from the azeotropic and the entrainer recovery columns, A and E, respectively, where represents the overall vapor composition from the azeo-column, 2 1SP Hquid in equiUbrium with overhead vapor composition from the azeo-column, Xj, distillate composition from entrainer...

The entrainer recovery column takes the distillate stream, from the azeo-column and separates it into a bottoms stream of pure water, and a ternary distillate stream for recycle to column 2. The overall material balance line for column 3 is shown in Figure 19b. This sequence was one of two original continuous processes disclosed in 1915 (106). More recendy, it has been appHed to other azeotropic separations (38,107,108). 

Fig. 20. Three sets of material balance lines for the Kubierschky three-column sequence where design 1 corresponds to the upper tie-line having Tmin = 8.78 design 2, to the subcooled upper tie-line having = 12.23 and design 3, to the lower tie-line having = 17.31 represents overall decanter composition , the overall feed composition to the azeo-column , the distillate composition from the entrainer recovery column and O, the...

Example This equation is obtained in distillation problems, among others, in which the number of theoretical plates is required. If the relative volatility is assumed to be constant, the plates are theoretically perfect, and the molal liquid and vapor rates are constant, then a material balance around the nth plate of the enriching section yields a Riccati difference equation. 

The most impoi tant factor affecting product quahty is the material balance. In separating a feed stream F into distillate D and bottom B products, an overall mole-flow balance must be maintained ... 

FIG. 13-28 Two material-balance envelopes in the top section of a distillation column,... 

Exploitation of Boundary Curvature A second approach to boundaiy crossing exploits boundaiy curvature in order to produce compositions in different distillation regions. When distillation boundaries exhibit extreme curvature, it may be possible to design a column such that the distillate and bottoms are on the same residue curve in one distillation region, while the feed (which is not required to lie on the column-composition profile) is in another distillation region. In order for such a column to meet material-balance constraints (i.e., bottom, distillate, feed on a straight hne), the feed must be located in a region where the boundary is concave. 

Parameter Estimation Relational and physical models require adjustable parameters to match the predicted output (e.g., distillate composition, tower profiles, and reactor conversions) to the operating specifications (e.g., distillation material and energy balance) and the unit input, feed compositions, conditions, and flows. The physical-model adjustable parameters bear a loose tie to theory with the limitations discussed in previous sections. The relational models have no tie to theory or the internal equipment processes. The purpose of this interpretation procedure is to develop estimates for these parameters. It is these parameters hnked with the model that provide a mathematical representation of the unit that can be used in fault detection, control, and design. 

The total number of moles n, and composition x, in the distillate receiver can now be obtained from the material and component material balances ... 

The system material balance from Treybal [129] using a heated kettle and distillation column following a McCabe-Thiele diagram, using reflux, but having only a batch (kettle) charge ... 

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