A cyclohexanone vacuum column can suffer bottom or reboiler fouling partly because pressure drop in the upper tray section raises the pressure and boiling temperature of the lower column. In a documented industrial retrofit, only the 15 trays above the feed were replaced with 350Y structured packing. At an 80 mbar top pressure, the reported bottom pressure fell from about 205 to 135 mbar while the required upper-column separation was maintained, helping reduce bottom temperature and fouling. The key retrofit question is therefore not whether structured packing is generally better than trays, but which column section is consuming the vacuum pressure budget and whether replacing that section can reduce bottom thermal stress without sacrificing separation.

Furfural purification must remove light impurities such as water, methanol, acetone and acetic acid while also separating heavier compounds such as 2-acetylfuran and 5-methylfurfural. Furfural and water form a heterogeneous azeotrope, allowing condensed overhead to split into organic and aqueous phases, while vacuum operation reduces the high temperatures that can promote furfural resinization. A recent industry-oriented pilot process used BX500 wire-mesh structured packing in the upper sections and 252Y corrugated-sheet packing below, achieving furfural purity above 99.5% at about 5 kPa condenser pressure. Packing selection should therefore balance high-stage efficiency, low pressure drop and section-specific resistance to heavy/resin-forming material.

Hydrogen cyanide purification can use structured packing to provide efficient HCN-water separation with relatively low pressure drop. The application is unusual because conventional reflux can concentrate higher nitriles such as acetonitrile, acrylonitrile and propionitrile inside the tower. At sufficiently high concentration, two liquid phases may form, creating polymerization and foaming risks that can disturb structured-packing hydraulics. Packing selection should therefore balance theoretical-stage efficiency with channel openness, liquid distribution, reflux strategy, pressure-drop stability and the plant's actual higher-nitrile impurity profile.

DMF recovery from synthetic leather wastewater is complicated because water-containing DMF can hydrolyze during heating to form formic acid and dimethylamine. Vacuum distillation reduces the required temperature and helps suppress this decomposition, while low-pressure-drop structured packing helps preserve the vacuum through the rectification section. Industrial DMF recovery and retrofit projects have directly used structured packing to improve separation and capacity. Packing selection should nevertheless consider high-boiling residues, solids, deacidification requirements, feed variability and the complete heat-integrated recovery system rather than treating the service as a clean DMF-water binary distillation.

N-methyl-2-pyrrolidone recovered from lithium-ion battery electrode manufacturing contains water together with low- and high-boiling impurities, so industrial NMP recycling requires more than simple solvent dehydration. Published battery-recovery systems use packed or tray columns to first remove water and light components and then reject high-boiling contaminants, producing NMP of 99.9 wt% or higher. Single-column side-cut designs can place high-purity NMP between the light-impurity zone above and heavy-impurity zone below. Structured packing is attractive because its high stage density and low pressure drop support reduced-pressure operation, but packing grade, liquid distribution, side-draw position and turndown must be evaluated against the actual battery recovery duty.