Rotating Packed Beds HIGEE

However, the gas undergoes a solid-body-like rotation and the slip velocity between liquid and gas is in the same range as in a conventional packed bed. Hence, for the cases in which the controlling resistance is on the gas side, the expected size reduction is only about 5-8 times, which is due to the high specific area of the packing. In most distillation columns, the dominant resistance is on the vapor side. To enhance the slip velocity and hence the gas-side mass-transfer coefficient, a rotor with split packing was proposed by Chandra et al. [5]. Its brief description is given below. 

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Three-phase rotating packed bed (HIGEE) reactor Three-phase circulating fluidized bed reactor... 

Figure 13.6 HiGee technology for hypochlorous acid manufacturing at Dow Chemical. Three rotating packed beds shown in front offer the same production capacity as the conventional plant behind them. (Courtesy Dow Chemical.)...

One particular embodiment of this approach is the rotating packed bed, which was originally conceived as the Higee equivalent of a packed column (1),... 

In its present configuration the HiGee rotating packed-bed concept only applies the elevated acceleration to the mass transfer elanent of a distillation operation. However, it is worth noting that the associated reboiler and condenser functions both involve multiple phases. They could therefore benefit from inclusion within the rotor, leading to a peripheral reboiler and a central condenser. This would lead to a further development of the PI strategy by the provision of multi-functional units, see Figure 6.8. 

As shown in the examples below, rotating packed-bed machines (e.g. HiGee), are used in bulk chemicals plant. The benefits are substantial, as illustrated in Table 8.1. 

Three HiGee units were installed by Dow Chemicals in the US for stripping hypochlorous acid, used as the reactive chemical in a process. The rotating packed-bed used for stripping was selected after other alternatives such as a spray distillation tower were rejected for capital cost reasons. The packing selected was a woven wire screen, with the gas flowing counter-current to the liquid. Various packing surface areas were tested, with 2000-3000 m /m area densities, but these exhibited no performance differences so the lower value was used. 

Much has been reported about the HiGee concept in the chemicals and offshore processing sectors, but its use in the food and drink industries has been less evident. Already referred to in Chapters 8 and 9 in the context of oil and gas processing and the chemicals sector, the use of rotating packed beds of the type described in Chapter 6 has been extended to other application areas by GasTran Systems (see Appendix 4) including deaeration of beverages. 

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