GPSA · Plant Processing of Natural Gas Ch. 9 · Packed Towers
Learn packing types, HETP calculations, and pressure drop design
It designs packed columns by calculating HETP, flooding velocity, pressure drop, and packing selection for absorption and stripping applications.
HETP (Height Equivalent to a Theoretical Plate) is a measure of packing efficiency that relates the physical height of packing to the number of theoretical separation stages.
It supports packed column sizing and pressure drop calculations for gas processing applications including absorption and stripping operations.
Packed columns are preferred for vacuum service (low pressure drop), corrosive systems, foaming applications, low liquid rates below 5 gpm/ft², and large columns over 10 ft diameter. Trayed columns are better for fouling service, wide turndown, and very low surface tension liquids.
HETP (Height Equivalent to a Theoretical Plate) converts theoretical stages to actual packing height. Metal Pall rings have moderate HETP of 2-4 ft and are the most common random packing for amine treating and general absorption applications.
Design velocity is typically 70-80% of the flooding velocity calculated from the Generalized Pressure Drop Correlation. Operating too close to flood causes excessive liquid entrainment and poor separation performance.
Common applications include amine contactors (2-inch Pall rings, 15-25 ft packing height), glycol dehydration (1-2 inch random packing, 10-20 ft height), NGL fractionation (structured packing for low pressure drop), and acid gas removal with MDEA systems.