Packed-column gas absorbers

Edwin Lightfoot I ve been impressed by the talks this morning. I urge fluid mechanicists to study separation processes because they are dominated by fluid mechanics. What you want is to maximize mass transfer and minimize momentum transfer. The sensitivity of momentum transfer to geometry is so much greater than the sensitivity of mass transfer that the fluid mechanics problems tend to dominate. If you look at the asymptotic results that Gary talked about, you can get useful insights into practical problems that don t require much time to develop. For example, if you examine the old problem of packed-column gas absorbers, you can show with relatively simple... 

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 ... 

Nonisothermal Gas Absorption. The computation of nonisothermal gas absorption processes is difficult because of all the interactions involved as described for packed columns. A computer is normally required for the enormous number of plate calculations necessary to estabUsh the correct concentration and temperature profiles through the tower. Suitable algorithms have been developed (46,105) and nonisothermal gas absorption in plate columns has been studied experimentally and the measured profiles compared to the calculated results (47,106). Figure 27 shows a typical Hquid temperature profile observed in an adiabatic bubble plate absorber (107). The close agreement between the calculated and observed profiles was obtained without adjusting parameters. The plate efficiencies required for the calculations were measured independendy on a single exact copy of the bubble cap plates installed in the five-tray absorber. 

NGc, Nitrosamines, Nitramines, etc. In this technique, microgram quantities of a sample are added to a column packed with an absorbing medium or phase. Over this is maintained a flow of mobile phase (gas or liq). The sample components separate because of their relative mobility in the absorbing phase, and thus leave the column at different times (See Vol 1,... 

Experiments were performed in a packed column with 1000 mm in length and 18 mm in diameter. The absorber was operated with a continuous influent gas feed rate of 0.2L/min from fhe bottom and a continuous scrubbing solution fed at a superficial flow rate of 13 m /m. hr at the top, as described in [8]... 

A packed column is used to absorb S02 from flue gas using an ethanolamine solution. The column is 4 ft in diameter, has a packed height of 20 ft, and is... 

Nonisothermal gas absorption in bubble tray absorbers, 1 86-87 in packed column absorbers,... 

Nuclides, reaction with monomers, 14 248 NuDat database, 21 314 Nukiyama-Tanasawa function, 23 185 Null-background techniques, in infrared spectroscopy, 23 139-140 Number-average molecular weight, 20 101 of polymers, 11 195, 196 Number density, of droplets, 23 187 Number of gas-phase transfer units (Nq), packed column absorbers, 1 51 Number of overall gas-phase transfer units (Nog), packed column absorbers, 1 52 Number of transfer units (Nt, NTU), 10 761... 

Outside vapor deposition (OVD), in fiber optic fabrication, 11 140, 141 Outsourcing, of maintenance, 15 478 Ovalbumin, properties of standard, 3 836t Overaged precipitation, 13 502 Overall gas-phase height of a transfer unit (Hog), packed column absorbers, 1 52... 

Liquid absorbents. If the partial pressure of the water in the gas is greater than the equilibrium partial pressure at the surface of a liquid, condensation will take place as a result of contact between the gas and liquid. Thus, water vapour is frequently removed from a gas by bringing it into contact with concentrated sulphuric acid, phosphoric acid, or glycerol. Concentrated solutions of salts, such as calcium chloride, are also effective. The process may be carried out either in a packed column or in a spray chamber. Regeneration of the liquid is an essential part of the process, and this is usually effected by evaporation. 

In 1981 the Los Alamos National Laboratory investigated for EPA the thermal destruction of wooden boxes treated with penta-chlorophenol (PCP). The incineration system consisted of a dual-chamber, controlled-air incinerator, a spray quench column, a venturi scrubber, and a packed-column acid gas absorber (11). Destruction efficiencies for PCP exceeded 99.99% for combustion chamber temperatures above 980°C, 20% excess air, and a retention time greater than 2.5 s. For these conditions, TCDD and... 

It should be appreciated that this example is one of the few very simple practical cases of a packed column reactor. The removal of carbon dioxide by reaction is a step in many important industrial processes, e.g. the nitrification of natural gas and of hydrogen in the manufacture of ammonia. Most of these processes0 " use as the liquid absorbent a solution which can be regenerated, for example solutions of amines or potassium carbonate0", and the design of these columns is distinctly more complicated. 

A schematic process flow sheet is shown in Figure 2. Inlet gas, a mixture of methane, hydrogen and carbon monoxide at 100°F and 500 psia (stream 1) is successively cooled to -140°C by the outlet gas stream from the absorber and some recycle gas. The absorber is a packed column of 1-in. berl saddles with 50% void fraction. The rich liquid from the bottom of the absorber is heat exchanged with the bottom liquid from the stripper. The stripper is also a packed column with 1-in. berl saddles. The dissolved methane, hydrogen, and carbon monoxide is stripped out by heating at the bottom of the stripper. The outlet gas stream from the stripper is heated in a heat exchanger by a recycle gas stream and is further compressed to produce the final methane product at 100°F and 1000 psia. 

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