A comparison of Berl saddles and Nor-Pac rings for absorption in the air-ammonia-water system



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Texas Tech University


This research has two objectives. The first objective is to determine three conventional packed tower performance characteristics for each of two packings: 1/2-in. (nominal) ceramic Berl saddles and 5/8-in. (nominal) polypropylene Nor-Pac® rings. The characteristics are the gas-handling capacity; the height of a transfer unit; and the overall, gas-associated with each packing. The second objective is to compare these performance characteristics in order to determine which packing has the higher gas-handling capacity, the lower height of a transfer unit, and the higher overall, gas-side, mass-transfer coefficient.

The first objective was met by obtaining experimental data from a single laboratory-scale gas absorber packed first with the Berl saddles, then with the Nor-Pac® rings when they became available. The data includes the pressure drop at various air and water flowrates, which was used to determine a set of flooding and loading points. The operating range and the gas-handling capacity associated with each packing were based on the flooding- and loading-point data. The packed tower was then used as an absorber to remove ammonia from air using water as the liquid solvent. The steady-state inlet and outlet compositions were used to calculate the number of transfer units (NTU), which represent the amount of contacting required to accomplish a phase enrichment, divided by the driving force in phatphase.^ The HTU values were obtained from the NTU and the height of the packed section. Subsequently, the HTU and other proces parameters were used to calculate KoG.

The second objective was met by comparing the flooding points and operating ranges of each packing, as well as the HTUs and KQGS. These last two parameters were reported as functions of both the gas and the liquid flowrates.