Novel Structured Packings

The novel structured packings that were used in the non-reactive sections of the column (i.e. the rolled mesh bales described in Chapter 11, Section 11.3.2) were tested prior to installation in the column in order to determine the pertinent packing characteristics: capacity, holdup, radial dispersion and pressure drop. The tests were performed in an apparatus used for undergraduate mass transfer laboratoiy experiments using air and water as the test fluids. The test rig diameter (140 mm) was similar to the pilot plant column (155 mm) and was constructed of perspex so that the fluid flow patterns could be observed.

A water flow rate of 3.5 L/min was used for all the tests while the air flow was varied from 150 L/min to 800 L/min. These rates compare with the pilot plant design conditions of 3.3 L/min of liquid and 60 L/min of vapour. The tests were repeated with 6 mm glass Raschig rings to provide a secondary assessment of the packing characteristics. These data were considered important since flooding predictions obtained with Pro/II indicated that 6 mm raschring rings would provide adequate hydraulic capacity for the required service. The pressure drop data from both sets of tests are shown in Table 12.1 and indicate that the novel packings have a higher capacity than the raschring rings, suggesting satisfactory hydraulic performance in the pilot plant.

Table 12.1 - A.ir-Water Pressure Drops for Novel Structured Packings and 6 mm Glass Raschring Rings in the 140 mm Diameter Test Apparatus

Novel Structured Packings 6 mm Raschring Rings

Novel Structured Packings 6 mm Raschring Rings

Table 12.1 - A.ir-Water Pressure Drops for Novel Structured Packings and 6 mm Glass Raschring Rings in the 140 mm Diameter Test Apparatus

Air Flow (L/min)

AP (mm H20)

AP/m

AP (mm H20)

AP/m

150

2.5

10

3

12

200

3

13

4.5

19

300

5

21

10

42

400

7

29

18

75

500

11

46

28

117

600

15

63

45

188

800

26

109

flooding

flooding

The higher density of the process vapour compared with the test fluid (air) will increase the pressure drop from the measured values but, at a vapour flow of 60 L/min, flooding is not expected in the pilot plant. The holdup and radial dispersion of the novel packings were recorded visually and were found to be similar to the raschring rings and, therefore, were considered to be acceptable.

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