Reboiled stripping

Reboiled stripping is efficient for mixtures containing a significant amount of light and intermediate components. An example is the separation of C2 and C3 fractions from a hydrocarbon mixture issued from fluid catalytic cracking. The initial precooled mixture is sent to the top of a distillation column provided only with reboiler. The top product contains gases and light components stripped out... 

The first step is the split of the initial mixture in essentially monophase submixtures, as gas, liquid and solid. This operation, called the first separation step, can employ simple flash or a sequence of flashes, adsorption/desorption and reboiled stripping, or the combination of the above techniques. Next, the process synthesis activity can be further handled by specialized managers, namely gas split manager (GSM), liquid split manager (LSM) and solid split manager (SSM). 

Reboiled stripping. In this case, the vapor needed for stripping is produced internally. This method may replace conveniently steam distillation. Note that the initial mixture should be fed at sufficiently low temperature on the top stage. 

The next column C-2 handles the separation of acrylonitrile/ace to nitrile binary by extractive distillation. A large amount of water is necessary to modify the volatility of components. The simulation indicates a ratio solvent/mixture of 10 1, which corresponds roughly to the complete dissolution of acrylonitrile in water. The column has 40 theoretical stages, being simulated as reboiled stripping. Water is introduced on the top stage, the organic feed in the middle. Purified acrylonitrile leaves in top, while acetonitrile is drawn off as a liquid side stream. 

The above development raises conceptually the problem of steam distillation versus reboiled stripping. The first has the advantage of simpler equipment, but the disadvantage of contamination. With the second the situation is reversed. The choice depends largely on local conditions. 

FIG, 13-2 Separation operations related to distillation, [a) Flash vaporization or partial condensation, h) Absorption, (c) Rectifier, d) Stripping, (e) Reboiled stripping, fj Reboiled absorption, (g) Refluxed stripping, (h) Extractive distillation. (1) Azeotropic distillation. 

The column has two feeds, as in Example 9.1, but in this application the feeds are of very different average boiling points, and they enter the column at about the same temperature. The oil feed has the higher boiling point and is fed at the top of the column as external reflux, while the gas mixture is fed at an intermediate tray. The top section of the column between the two feeds is the absorption section where most of the propane recovery takes place. The lower section, between the gas feed and the reboiler, is the reboiled stripping section where ethane and lighter components are stripped off as in conventional columns. 

Recovery of absorbents Reboiled stripping Stripping Flashing, reboiled, or steam stripping... 

Decomposition in elementary simulation blocks. Example an azeotropic distillation column may be decomposed in reboiled stripping column, heat exchanger, three-phase flash separator and reflux splitter. 

The application of the heuristics indicates that the gaseous components should be removed in the first split, This separation can be done by a simple flash, which will be the first step in the sequence. The second split should take as lights the four next components, up to water. This split corresponds also to the heuristics three and four. A suitable separation technique could be the reboiled stripping. 

The production of steam is very important to the operation of an industrial facility. Steam is used in a variety of operations, including heating and temperature control, steam turbines, steam tracing, heat exchangers, reboilers, stripping, and distillation. The energy in steam can easily be... 

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