Ideal trays

The feed tray lies between ideal trays 5 and 6, and in practice, the eighth actual tray from the top would be used. 

The model of a multicomponent batch distillation column was derived in Sec. 3.13. For a simulation example, let us consider a ternary mixture. Three products will be produced and two slop cuts may also be produced. Constant relative volatility, equimolal overflow, constant tray holdup, and ideal trays are assumed. 

AFTER TOTAL REFLUX STARTUP, DISTILLATE FLOW RATE IS FIXED ASSUMPTIONS CONSTANT RELATIVE VOLATILITIES (TERNARY) BQUIMOLAL OVERFLOW, IDEAL TRAYS... 

Finally, if the organic-solvent concentration in the recycled CO2 stream is too high for the particular system considered, a small distillation tower may be needed. Preliminary studies show that a tower with only six ideal trays, operating at 50 bars, can reduce the THF percentage in the CO2 recycled stream to 0.1 % [4]. This option should also be applied if CO2 is to be used to remove the residual THF content from the solid product. 

The units for pressure might not show up as atm. If not, you can change the units for entering any quantities hitting the function key F5. After setting the pressure, choose Return which moves the cursor to Heaters/cooiers. No heat is to be added or removed except for the condenser and reboiler, so we move the cursor on down to Efficiencies. Here we enter the Murphree tray efficiency. We enter 1 as the default to obtain ideal trays throughout the column. 

Use 8 trays, since it is not possible to specify a fractional number of trays. We can back-calculate the actual concentration of the gas leaving the tower when 8 trays are used. For an overall efficiency of 0.596 and an actual number of trays of 8, equation (5-5) yields N = 4.784 ideal trays. Solving equation (5-3), yt = 0.094%, which satisfies the requirement that the gas exit concentration should not exceed 0.1%. 

One kmol/s of a gas consisting of 75 mol% methane and 25% n-pentane at 300 K and 1 atm is to be scrubbed with 2 kmol/s of a nonvolatile paraffin oil entering the absorber free of pentane at 308 K. Estimate the number of ideal trays for adiabatic absorption of 98.6% of the pentane. Neglect the solubility of methane in the oil, and assume operation to be at constant pressure. The pentane forms ideal solutions with the paraffin oil. The average molecular weight of the oil is 200 and the heat capacity is 1.884 kJ/kg-K. The heat capacity of methane over the range of temperatures to be encountered is 35.6 kJ/kmol-K for liquid pentane, is 177.5 kJ/kmol-K for pentane vapor, is 119.8 kJ/kmol-K. The latent heat of vaporization of n-pentane at 273 K is 27.82 MJ/kmol (Treybal, 1980). 

The required yx = 0.0046 occurs at about 4 ideal trays, and the temperature on the top tray is esentially that assumed. Had this not been so, a new assumed value of Tx and a new stage-by-stage calculation would have been required. 

Table 10.2 Feed and product specifications for DE, DP, EF and PF columns number of ideal trays in each column is excluding condenser and reboiler stage numbers are counted from top with condenser as zeroth stage. 

EF 1693 kgmol/h (48 056 kg/h) at 2056 kfti and -24.4 °C Nf =86 Methane (0.003), Ethylene (0.8388), Ethane (0.1604), Propene (0.0005) Ethylene mole fraction in Overheads = 0.999 Ethane mole fraction in bottoms = 0.995 Column top pressure = 1997 kRa Pressure drop/tray= 0.7 kPla No. of ideal trays = 125 Total condenser Peng-Robinson model... 

Overall tray efficiency. The overall tray or plate efficiency Eq concerns the entire tower and is simple to use but is the least fundamental. It is defined as the ratio of the number of theoretical or ideal trays needed in an entire tower to the number of actual trays used. 

A 13 ideal tray column has its feed (100 kg mole/minute of saturated vapor) introduced on tray five. Relative volatility, Xd and Xg are 2, 0.94, and 0.06. Find the column s reflux ratio. What are the various tray... 

Carbon dioxide is separated from methyl alcohol in a stripping column. The saturated liquid feed enters the top tray at 100 kmole/min. Equilibrium is governed by T = 2X. If three ideal trays plus reboiler are used find the following items (assuming column liquid and vapor rates are constant). Feed and overhead vapor compositions when Xb =0.01 and... 

A stripping column used to separate ethanol and water has three ideal trays. The feed (13 mole percent ethanol) enters the top as a saturated liquid. In lieu of a reboiler live steam enters below tray 1 at 1000 kmole/hour. 

Stripper top product is 0.70 mole fraction THF. The bottom (liquid) product, which has a 0.01 mole fraction THF, is recycled back to the absorber to serve as the liquid feed (a 0.01 mole fraction THF liquid is added as makeup). Find the ideal trays for the absorber and stripper as well as all vapor and liquid flow rates. 

Where both operating line and equilibrium curve can be considered straight, the number of ideal trays can be determined without recourse to graphical methods. 

Equation (8.102) is an expression for the fractional absorption of any component, exact because it is based only upon material balances and the condition of equilibrium which defines an ideal tray. 

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