Theoretical stages atmospheric distillation

Heat Sensitivity. The heat sensitivity or polymerization tendencies of the materials being distilled influence the economics of distillation. Many materials caimot be distilled at their atmospheric boiling points because of high thermal degradation, polymerization, or other unfavorable reaction effects that are functions of temperature. These systems are distilled under vacuum in order to lower operating temperatures. For such systems, the pressure drop per theoretical stage is frequently the controlling factor in contactor selection. An exceUent discussion of equipment requirements and characteristics of vacuum distillation may be found in Reference 90. 

A water-isopropanol mixture at its bubble point containing 10 mol% isopropanol is to be continuously rectified at atmospheric pressure to produce a distillate containing 65 mol% isopropanol. Eighty-five percent of the isopropanol in the feed must be recovered. VLE data are given in Problem 6.13. If a reflux ratio of 1.5 times the minimum is used, how many theoretical stages will be required ... 

A batch distillation column with four theoretical stages (first stage is the still pot) is charged with 100 kmol of a 50 mol% benzene in toluene mixture at atmospheric pressure. At a constant reflux ratio R = 1.5, how many moles of the charge must be distilled if an average product composition of 84 mol% benzene is required If the boil-up ratio is 15 kmol/h, calculate the distillation time. The equilibrium distribution curve at column pressure is given in Example 6.4. 

A batch distillation column with eight theoretical stages (the first stage is the still pot) is charged with 500 kmol of a 48.8 mol% A in B mixture at atmospheric pressure (relative volatility aA B = 2.0). The boil-up ratio is constant at 213.5 kmol/h. If the distillate composition is to be maintained con-... 

The results of a steady-state simulation for a distillation column to separate a mixture of 50 wt% cyclohexane/w-heptane (Cg/Cy) into 99.93% Cg in the distillate and 0.07% Cg in the bottoms are shown in a McCabe-Thiele diagram (Figure 3.1). The simulation used 50 theoretical stages with a reflux ratio of 3.41 at atmospheric pressure with a feed temperature of 15 C. 

Initially, structured packings were applied in vacuum distillation services because their very low pressure drop characteristics and low HETP values provided reduced pressure gradients per theoretical stage. Later, these packings were used to increase capacity in atmospheric distillations, since replacement... 

---