Reboilers selection

Figure 7 provides an overview of reboiler selection choices. The accompanying notes provide information for a quick or first cut estimate of the appropriate type for a given application. Tables 2 - and 3 provide additional, more detailed, selection data. Table 2 gives advantages and disadvantages for all the major reboiler types. Table 3 is limited to thermosyphon types. 

Love, D. L., No Hassle Reboiler Selection, Hydrocarbon Processing, October 1992. 

To illustrate the effect of the pressure drop on the reboiler selection. Table 10-34 compares several designs for the same heat load and quantity of reboiled vapor. 

This table and the following discussion are intended to serve as a general guide. In a specific application, reboiler selection may also be influenced by other factors. The application of the common reboiler t5rpes is described below. 

The use of high or low limits for process variables is another type of selective control, called an override. The feature of anti-reset windup in feedback controllers is a type of override. Another example is a distillation column with lower and upper limits on the heat input to the column reboiler. The minimum level ensures that liquid will remain... 

This applies to any pair of components. My experience suggests adding +1 theoretical tray for the reboiler, thus making the total theoretical trays perhaps a bit conservative. But, they must be included when converting to actual trays using the selected or calculated tray efficiency ... 

As an example, if this were the final column selection, then the column trays = 8-condenser-reboiler = 6 theoret-... 

Figure 10-96C. Shell types selected for horizontal and thermosiphon reboilers, boiling in shell. (Used by permission Yilmaz, S. B. Chemical Engineering Progress, V. 83, No. 11, 1987. American Institute of Chemical Engineers. All rights reserved.)...

The mechanism of boiling is essentially nucleate pool hoiling. In hoth styles of rehoiler the liquid velocity is relatively low compared to thermosiphon units. Jacobs provides an extensive comparison of advantages and disadvantages of essentially all the reboiler types used in industrial plants. Palen and Taborek conducted extensive studies of available data and proposed nucleate boiling equations to correlate various data from the available 14 equations down to a selected 6 for detailed study. The study was limited to various hydrocarbons and hydrocarbon mixtures. Their conclusions after computer correlations of the results from several equations were as follows. 

Select flow loop geometry, i.e., type reboiler arrangement. 

Design Select a thermosiphon reboiler as the preferred operation, if design is acceptable. 

Vertical Thermosiphon Reboiler Comparison Effect of Pressure Drop and Pipe Size on Selection... 

Reboiler control systems are selected as part of the general control system for the column and are discussed in Section 5.8.7. 

S Entropy (kJ-K-1, kJkg-1-K-1, kJkmol-1-K-1), or number of streams in a heat exchanger network (-), or reactor selectivity (-), or reboil ratio for distillation (-), or selectivity of a reaction (-), or slack variable in optimization (units depend on application), or solvent flowrate (kg s-1, kmol-s-1), or stripping factor in absorption (-)... 

A reboiler at the bottom of a distillation column contains an organic liquid at 1 atm and 320°F, at which its density is 0.7 g/cm3, its viscosity is 0.5cP, and its vapor pressure is 800 mmHg. The liquid must be pumped to another column at a rate of 200 gpm and discharges at 1 atm at a point 30 ft higher than the reboiler. You must select the best pump from those represented by the curves in Appendix H and determine where the pump is to be installed. The suction line of the pump will include 20 ft of 2 in. sch 40 pipe, eight elbows, four gate... 

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