Poor distribution can lead to dry zones or localised flooding, severely affecting performance. ○ Fouling susceptibility : Packed beds are more prone to plugging from solids or degradation products. Cleaning often requires the complete removal and replacement of packing, which is time-consuming and costly. ○ Vendor-specific design : Performance predictions rely on proprietary correlations and vendor data, needing close collaboration during design and implementation. In summary, trays offer reliability and ease of maintenance, while packing provides efficiency and compactness. The best choice depends on factors such as process conditions, fouling potential, maintenance practices, and overall economics. Case study: Retrofitting a refinery amine regenerator To assess the practical implications of converting trays to packing, a simulation-based study was conducted on an existing amine regenerator in a mid-sized refinery. System overview ○ Column dimensions: 3.0m diameter, 32m height. ○ Amine solution: 40 wt% MDEA. ○ Current throughput: 330 m³/h rich amine feed. ○ Internals: 23 trays (20 two-pass in stripping section, three single-pass in wash section). ○ Operating conditions: Reboiler pressure at 1.31 barg, bottom temperature at 128.2°C, condenser temperature at 45°C. ○ Guaranteed lean amine loading: 0.01 mol of H 2S/mol of amine. The column runs at 79% of its jet flood capacity, with a pressure drop of 180 mbar. Figure 2 shows a simplified sketch of the existing column. Packing retrofit : Replace the 20 stripping section trays with IMTP #50 random packing, keeping the top three wash trays. Figure 3 shows the existing column with its stripping trays replaced with packing. Pushed trays : Increase circulation rate to assess the maximum capacity of existing trays without changing internals. Both scenarios were modelled using mass Revamp scenario Two options were evaluated:
Re ux
Re ux
23#
23#
22#
22#
21#
21#
Feed
Feed
20#
19#
Bed 1
10#
9#
2# 1#
Bed 2
transfer rate-based distillation simulations, with key parameters constant for fair comparison. Design constraints ○ Maximum flood limits : 90% for trays, 85% for packing (revamp scenario). ○ Foaming factor : 0.85 applied to both cases. ○ Lean amine H₂S target : ~0.006-0.007 mol/mol (margin to satisfy guaranteed loading). ○ Steam-to-amine ratio : 1 lb/gal (industry standard). Result summary Table 1 shows the result of the study. The packing retrofit resulted in a substantial increase of approximately 30% in throughput, with the rich amine flow rising from 330 m3/h to 425 m³/h. More importantly, it led to a significant reduction in column pressure drop by approximately 140 mbar, decreasing from 180 Figure 2 (left) Existing column. Figure 3 (right) Existing column; stripping trays replaced with packing
Refining India
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