Column diameter absorber

The design studies are made for a packed column filled with 35-mm Pal rings. The height of the column is determined for 95 % removal of SO2 when 0.05 kmol m-3 bicarbonate solution is used as absorbent. The column diameter choice is based on 60 % of flooding condition. 

The apparatus essentially consists of a long narrow glass tube about 20-30 cm long and 2-3 cm in diameter. This can hold 60-70 g of absorbent. The absorbent column is supported on a plug of glass wool. If the tube is wider, a perforated disc covered by a pad of cotton is often used. The tube is provided with a tap at the bottom. The removal of the column from the tube is a simple process. 

To minimize channeling of liquid in packed absorbers and strippers require that the packing be sufficiently small when con5)ared to the column diameter. Small packing, however, will result in a high pressure drop.Treybal [29] specifies that the ratio of separator diameter to the packing diameter should be 15/1. 

Table 6.23 Summary of Equations for Sizing Absorbers, Strippers, or Fractionators - Column Diameter...

A packed column is designed to absorb ammonia from a gas stream. Given the operating conditions and type of packing below, calculate the height of packing and column diameter. The unit operates at 60% of the flooding gas mass velocity, the actual liquid flowrate is 25% more than the minimum, and 90% of the ammonia is to be collected. 

Determine the column diameter, tray efficiency, number of actual trays, and column height for the absorber of Example 12.8 or 15.4 if valve trays are used. 

The foregoing suggests that column diameters and packing selection can be sased on pressure drop and, indeed, this is commonly done. Figure 16.15 shows die computational steps. We start with the L/C obtained from the material iialance, choose a preliminary packing size, and obtain F from Table 16.6. Next we decide on the AP. A reasonable value for absorbers and strippers is 0.4 in./ft, which, as shown in Fig. 16.16, corresponds to about 60 to 70% of capacity [flooding). 

Example 13.1. Eletermine the column diameter for the reboiled absorber of Example 15.8 using a solution based on the Soave-Redlich-Kwong equation of state for thermo-d)mamic properties. Computed temperatures and molal flow rates, densities, and average molecular weights for vapor and liquid leaving each theoretical stage are as follows. 

You are to design a packed column to absorb CO2 from air in fresh dilute-caustic solution. The entering air contains 3 mole% CO2 and a 97% recovery of CO2 is desired. The gas flow rate is 5000 fF/min at 60°F, 1 atm. It may be assumed that at the range of operation Y = 1.75.Y where Y and X are mole ratios of CO2 to carrier. A column diameter of 30 in. with 2-in. Intalox packing can be assumed for the initial design estimates. Assume the caustic solution has the properties of water. Calculate ... 

In order to obtain a solution in 2M HPTS (p-toluenesulfonic acid), the [Mo303S(aq)] solution in IMHCl is diluted to five times its original volume with water, and was absorbed to Dowex 50W-X2 cation exchanger (column diameter 2 cm, length 10 cm). The column is then washed with O.IMHPTS to remove Cl" ion ( 200mL the column can be washed rapidly, and full removal of Cl ion is checked by AgN03 solution) and eluted slowly with 2M HPTS. Typically 120 mL of a 0.04M (per trimer) red solution is obtained. 

Internals, liquid, and gas distribution are practical aspects of column design discussed by Zenz [5]. Since in absorbers the liquid and the gas generally flow in countercurrent directions, there is a close interaction between the column diameter and the liquid and gas flow rates. If, for a given column diameter and liquid flow rate, the gas flow rate is too high, the liquid will be blown to the top of the column, which is said to be flooded. Zenz [5] derived the following relation for the maximum allowable gas and liquid flow rates above which flooding occurs ... 

CO2 is absorbed into propylene carbonate in a packed column. The inlet gas stream is 20 mol% CO2 and 80 mol% methane. The gas stream flows at a rate of 2 m /s and the column operates at 60°C and 60.1 atm. The inlet solvent flow is 2000 kmol/h. Use Aspen HYSYS to determine the eoncentration of CO2 (mole%) in the exit gas stream, the column height (m) and the column diameter (m). 

Optimal absorbent (stripping agent or extraction solvent) flow rate in an absorber (stripper or liquid-liquid extractor), for which the number of stages is balanced against the column diameter and absorbent (stripping agent or extraction solvent)... 

The packed hei t throng which a nonuniform profile persists is a function of column diameter (156). In pilot-scale columns, vapor maldistribution was found to posist for abed he t of the order of 1 ft (155,157). In large-diameter columns, this maldiattibution persists to a much greater hei t (15,152,154). In a number of 15-ft-diameter absorbers (154), vapor maldistribution persisted throu a 50-ft bed the efficiency was about balf that encountered during good vapor distribution. 

D20. Do after studying Chapter 12. If the column uses sieve plates, what column diameter is required for the absorber in Problem 12.D14 Operate at 75% of flood. Use a 0.6096 mtray spacing. Assume q = 0.85. The density of liquid ammonia is approximately 0.61 gm/ml. Assume that nitrogen is an ideal gas. Note that you will have to extrapolate the graph or the equation for 24-inch tray spacing to find Cgi,. Since surface tension data are not reported, assume that a = 20... 

Design the column diameter for an absorber or stripper for staged columns and packed columns... 

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