Trays vs. Packing
December 12, 2006
Kohl (1997) contains excellent information concerning trayed vs. packed columns for gas treating applications. Some information you will find in this text includes the following:
- Bubble-cap trays and raschig ring packings were once commonly used in amine plant absorbers and strippers, however, modern plants are generally designed to use more effective trays (e.g., sieve or valve types) and improved packing shapes (e.g. Pall rings or high-performance proprietary designs).
- The choice between trays and packing is somewhat arbitrary because either can usually be designed to do an adequate job, and the overall economics are seldom decisively in favor of one or the other.
- At this time, sieve tray columns are probably the most popular for both absorbers and strippers in conventional, large commercial amine plants; while packed columns are often used for revamps to increase capacity or efficiency and for special applications.
- Very high-performance structured packing is seldom used for large commercial gas treating plants because of its high cost and sensitivity to plugging by small particles suspended in the solution.
- Tray columns are particularly applicable for high pressure columns, where pressure drop is not an important consideration and gas purity specifications can readily be attained with about 20 trays.
- Packing is often specified for CO2 removal columns, where a high degree of CO2 removal is desired and the low efficiency of trays may result in objectionably tall columns.
- Packing is also preferred for columns where pressure drop and possible foam formation are important considerations.
- Packing should not be used in absorbers treating unsaturated gases that can readily polymerize (propadiene, butadiene, butylene, etc.) as gum formation can lead to plugging of the packing.
- Also, packing should not be used in treating gases containing H2S which are contaminated with oxygen because of the potential for plugging with elemental sulfur.
Authored by Lili Lyddon - BR&E Technical Support / Help Author