Pressure drop irrigated packing

A new generalised correlation for pressure drop in packed columns, similar to Figure 11.44, has been published by Leva (1992), (1995). The new correlations gives a better prediction for systems where the density of the irrigating fluid is appreciably greater than that of water. It can also be used to predict the pressure drop over dry packing. 

Piche, S.R., Larachi, F, and Grandjean, B.P.A. (2001c), Improving the prediction of irrigated pressure drop in packed absorption towers, The Canadian Journal of Chemical Engineering, 79(4) 584-594. 

Venturi scmbbers can be operated at 2.5 kPa (19 mm Hg) to coUect many particles coarser than 1 p.m efficiently. Smaller particles often require a pressure drop of 7.5—10 kPa (56—75 mm Hg). When most of the particulates are smaller than 0.5 p.m and are hydrophobic, venturis have been operated at pressure drops from 25 to 32.5 kPa (187—244 mm Hg). Water injection rate is typicaUy 0.67—1.4 m of Hquid per 1000 m of gas, although rates as high as 2.7 are used. Increasing water rates improves coUection efficiency. Many venturis contain louvers to vary throat cross section and pressure drop with changes in system gas flow. Venturi scmbbers can be made in various shapes with reasonably similar characteristics. Any device that causes contact of Hquid and gas at high velocity and pressure drop across an accelerating orifice wiU act much like a venturi scmbber. A flooded-disk scmbber in which the annular orifice created by the disc is equivalent to a venturi throat has been described (296). An irrigated packed fiber bed with performance similar to a... 

Leva, M. Chem. Eng. Prog. Symp. Ser. No. 10, 50 (1954) 51-59. Flow through irrigated dumped packing Pressure drop, loading, flooding. 

For gas flow through dry packings, pressure drop may be estimated by use of an orifice equation. For irrigated packings, pressure drop... 

I. Iliuta, F. Larachi, Mechanistic model for structured-packing containing columns Irrigated pressure drop, liquid holdup and packing fractional wetted area, Ind. Eng. Chem. Res. 40 (2000) 5140-5146. 

M. Leva Flow through Irrigated Dumped Packings, Pressure Drop, Loading Flooding, Chem. Eng. Prog. Symp. Sen, 50(10) 51 (1954). 

When the packed bed is irrigated, the liquid holdup causes the pressure drop to increase. The experimental data are reasonably well correlated by (Billet and Schultes, 1991a)... 

A packed tower is to be designed for the countercurrent contact of a benzene-nitrogen gas mixture with kerosene to wash out the benzene from the gas. The gas enters the tower at the rate of 1.5 m3/s, measured at 110 kPa and 298 K, containing 5 mol% benzene. Essentially, all the benzene is absorbed by the kerosene. The liquid enters the tower at the rate of 4.0 kg/s the liquid density is 800 kg/m3 and the viscosity is 2.3 cP. The packing will be 50-mm metal Pall rings, and the tower diameter will be chosen to produce a gas-pressure drop of 400 Pa/m of irrigated packing. 

A more rigorous approach to flooding is based on pressure drop models of irrigated packed beds, see Sect. 5.4.2.3. 

For packed beds used in gas and liquid contacting, the liquid can flow in the opposite direction to the gas (countercurrent operation), or it can flow in the same direction as the gas (concurrent operation), or the gas flow can be transverse to the liquid flow (crossflow operation). The theory of pressure drop in irrigated packed beds is not as well developed as that for single-phase flow. 

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