Benzene scrubbing liquid

For economic reasons, the use of RME as scrubbing liquid requires initial tar concentrations in the product gas to be relatively low. At the Giissing plant, tar concentrations downstream the fabric filter are reduced to approximately 2.5 g/Nm by the preliminary dry de-tarring treatment referred to earlier injection of fine limestone particles into the gasifier freeboard. Benzene and remaining tar compounds are then almost completely removed in the RME scrubber, operating at 5 C [33]. 

A vapor stream containing 3,0 mole percent benzene is scrubbed with wash oil in a packed absorber to reduce the benzene concentration in the gas to 0.02 percent. The oil has an average molecular weight of about 250 and a density of 54,6 Ib/ft and contains 0.015 percent benzene. The gas flow is 1500 ft /min at 25°C and 1 atm. (fl) If the scrubber operates isothermally at 25°C with a liquid rate of 14,000 Ib/h, how many transfer units are required (b) If the scrubber operates adiabatically, how many transfer units are needed (c) What would be the major effect of operating with an oil of lower molecular weight, say, M = 200 ... 

A gas stream (mole fraction of 0.03 benzene) is scrubbed with an oil (molecular weight 250, specific gravity of 0.875, 0.015 mole fraction benzene) in a packed column. The gas flow rate is 0.614 m /sec at 25°C. If the equilibrium relation is T = 0.125X and the liquid rate is 6.19 x 10 kmole/sec (on a benzene-free basis), find the number of transfer units needed. Also what effect would a molecular weight of 200 for the oil have ... 

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