Wetting columns

Ceramic and metal packings are normally dumped into the column wet , to ensure a truly random distribution and prevent damage to the packing. The column is partially filled with water and the packing dumped into the water. A height of water must be kept above the packing at all times. 

Figure 61 Expenditure of substances on total metabolism during a year by anchovy. Whole column wet matter light stipple lipids heavy stipple proteins. The small numbers represent age groups.

Figure 67 Efficiency of the utilization of assimilated food for production (K2) in anchovy, age groups 1-5. White columns, wet matter black columns, calories.

In addition to the stirred cell, other laboratory reactors commonly used include rotating drum contactor, wetted wall column, wetted sphere column, laminar jet, and stirred contactor. These equipments are shown schematically in Figures 11.14b-f. AU have several common features, the principal one being a weU defined gas-liquid interfacial area and the ability to vary the area per unit reactor volume a). In the stirred cell, it is achieved by varying the liquid height. As an alternative way, a solid circular baffle is placed at the gas-liquid interface. Holes are drilled on the baffle plate so that the hole opening area becomes the interfacial area. For varying a, baffle plates are made with different free (hole) areas. 

Multiple reactor constructions for gas-liquid reactors are available, because of the large number of different application areas. Spray columns, wetted wall columns, packed columns and plate columns are mainly used for absorption processes. The gas concentrations are low in the case of absorption processes, hence a large interfacial contact area between the gas and the liquid is important to enhance the absorption process. These column reactors usually operate in counter-current mode. Counter-current operation is the optimal operating mode, because at the gas outlet where the gaseous component concentration is lowest, the gas is in contact with a fresh absorption solution. The low concentration of the gaseous component can then partly be compensated by the high concentration of the liquid component. 

Plate column with shallow liquid layers on plates Spray column Wetted wall column... 

Fiorenza and co-workers [50] have described a technique based on column chromatography on neutral alumina for the separation of antioxidants, plasticisers, and so on, in rubber extracts (Figure 3.8). They detected the separated compounds by monitoring the effluent with a LKB 254 nm UV detector (Figure 3.9). In this procedure a carbon tetrachloride solution of the sample is applied to an alumina column wetted with the same solvent and the column is successively eluted with carbon tetrachloride, mixtures of carbon tetrachloride and benzene, benzene, mixtures of benzene and absolute ethanol, and finally, ethanol. Separations were carried out on a scale to provide enough of each separated compound for the preparation of IR and UV spectra. 

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