Column diameter stripping operations

There are five stripping trays, five rectifying trays, and nine reactive trays. The column operating pressure is 8 bar, and the holdup on the reactive trays is 1000 mol. The vapor boilup is 28.91 mol/s, and the column diameter is 0.805 m. Figures 4.2 and 4.3 give composition and temperature profiles in the column, respectively. 

Column Operation To assure intimate contact between the counterflowing interstitial streams, the volume fraction of liquid in the foam should be kept below about 10 percent—and the lower the better. Also, rather uniform bubble sizes are desirable. The foam bubbles will thus pack together as blunted polyhedra rather than as spheres, and the suction in the capillaries (Plateau borders) so formed vidll promote good liqiiid distribution and contact. To allow for this desirable deviation from sphericity, S = 6.3/d in the equations for enriching, stripping, and combined column operation [Lemhch, Chem. E/ig., 75(27), 95 (1968) 76(6), 5 (1969)]. Diameter d still refers to the sphere. 

The component with the lowest equilibrium constant is called the key component in the stripping process, because it yields the largest value of Vnjm- This largest value is the true minimum air flowrate, whereas the actual air flowrate should be selected at 1.20 to 2.0 times the minimum. This becomes a balance between fewer theoretical stages at actual air flowrate, yet requires a larger diameter column to carry out the operation. 

The air compressor purchase cost was estimated on the basis of power consumption. The oxidation vessel and reactor costs were estimated using correlations appropriate for pressure vessels. Capacity formed the basis of the storage tank purchasing cost. The absorption and stripping column were costed according to diameter, operating pressure and number of trays. 

A vessel 1.0 m in diameter is to be used for stripping chloroform from water by sparging with air at 298 K. The water will flow continuously downward at the rate of 10.0 kg/s at 298 K. The water contains 240 pg/L of chloroform. It is desired to remove 90% of the chloroform in the water using an airflow that is 50% higher than the minimum required. At these low concentrations, chloroform-water solutions follow Henry s law (yj = mx) with m = 220. The sparger is in the form of a ring located at the bottom of the vessel, 50 cm in diameter, containing 90 orifices, each 3 mm in diameter. Estimate the depth of the water column required to achieve the specified 90% removal efficiency. Estimate the power required to operate the air compressor, if the mechanical efficiency of the system is 60%. 

A wastewater stream of 0.038 m3/s, containing 10 ppm (by weight) of benzene, is to be stripped with air in a packed column operating at 298 K and 2 atm to reduce the benzene concentration to 0.005 ppm. The packing specified is 50-mm plastic Pall rings. The airflow rate to be used is five times the minimum. Henry s law constant for benzene in water at this temperature is 0.6 kPa-m3/mol (Davis and Cornwell, 1998). Calculate the tower diameter if the gas-pressure drop is not to exceed 500 Pa/m of packed height. Estimate the corresponding mass-transfer coefficients. The diffusivity of benzene vapor in air at 298 K and 1 atm is 0.096 cm2/s the diffusivity of liquid benzene in water at infinite dilution at 298 K is 1.02 x 10 5 cm2/s (Cussler, 1997). 

D5. A packed column 0.0762 m in diameter with 3.048 m of Intalox saddle packing is being run in the laboratory. P is being stripped fromnCg using methane gas. The methane can be assumed to be insoluble and the nCg is nonvolatile. Operation is isothermal. The laboratory test results are ... 

A modification of this technology has been used to treat solutions of ammonium salts and free ammonia. The stripped ammonia in the exit air stream subsequently is absorbed into a dilute sulfuric acid solution in a packed column. The air leaving this absorber is ammonia-free, thus it is recycled back through the stripping column in a closed cycle. Such a system is described in U.S. patent 3,920,419 [10]. This process is operated at a temperature range of 140 to 180°F in order to raise the vapor pressure of the dissolved ammonia. At such temperatures only 50 to 100 CFM of air per gpm is needed to remove 99% of the ammonia from the feed. By minimizing the recycled air flow, the diameters of the stripper and absorber are reduced. 

The present simulated object is an industrial-scale sieve tray column of FRl, which is 4 ft in diameter with six sieve trays for (1) separation of n-heptane and meth-ylcyclohexane [2] and (2) stripping of toluene from dilute water solution [3]. They reported the outlet composition and the tray efficiency of each tray under different operating conditions. The details of this column are given in Fig. 4.1 and Table 4.1 [2]. The operating pressure is 165 kPa. 

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