Can Structured Packing Be Replaced with Random Packing in an Existing Tower?

Most retrofit discussions focus on upgrading random packing to structured packing.

But the opposite conversion also occurs.

A tower using structured packing may be converted to random packing when operating conditions have changed or when fouling, maintenance, or cost has become more important than maximum efficiency.

The conversion can be practical, but it requires careful evaluation.

Why Replace Structured Packing with Random Packing?

Possible reasons include:

• severe fouling;
• solids in the process;
• frequent plugging;
• difficult cleaning;
• damaged structured packing;
• lower replacement cost;
• easier maintenance;
• changed separation requirements.

In dirty service, an open random packing may sometimes provide more reliable long-term operation.

Understand What Performance May Be Lost

Structured packing often provides high mass-transfer efficiency at relatively low pressure drop.

Random packing may behave differently.

The retrofit can affect:

• separation efficiency;
• pressure drop;
• capacity;
• liquid holdup.

The existing packed height may not provide the same process performance after conversion.

Therefore, the process duty must be recalculated.

Check Available Bed Height

If random packing requires more height to deliver equivalent separation, the existing shell may not have enough available space.

This can become the main limitation.

The designer should determine whether:

• existing bed height is sufficient;
• additional height is available;
• reduced performance is acceptable;
• another packing size or design is preferable.

Review the Support Plate

A support suitable for structured packing may have different geometry from one required for random packing.

Random packing needs openings small enough to retain individual pieces while maintaining high free area.

The old support should be checked for:

• opening size;
• open area;
• load capacity;
• mechanical condition.

An additional screen should not be added without considering hydraulic resistance.

Re-evaluate the Distributor

Random packing may tolerate distribution imperfections differently, but this does not mean distributor quality is unimportant.

The existing distributor should still be checked for:

• flow range;
• outlet spacing;
• levelness;
• blockage.

If the retrofit is being performed because of fouling, distributor design may also need modification to reduce plugging.

Consider Bed Depth and Mechanical Load

Random packing creates a deep loose bed.

This can generate different loading patterns from structured packing blocks.

The support system should be reviewed for total bed weight.

This is especially important if ceramic random packing is being considered.

Fouling Improvement Must Be Realistic

Switching to random packing can improve tolerance to certain fouling mechanisms, particularly when larger open passages are used.

But it does not remove the root cause of fouling.

The project should still examine:

• solids loading;
• precipitation;
• polymer formation;
• poor liquid distribution;
• insufficient washing.

Otherwise, the new packing may eventually foul as well.

Installation Becomes Simpler—but Not Uncontrolled

Random packing can often be loaded more easily than structured packing.

However, proper loading remains essential.

The bed should be uniform and free of large voids or excessive compaction.

Ceramic packing must be loaded carefully to minimize breakage.

Pressure-Drop Expectations Should Be Verified

It should not be assumed that random packing automatically creates higher pressure drop.

Performance depends on the selected geometry and size.

Modern high-capacity random packing can offer excellent hydraulic performance.

Actual operating conditions must be evaluated.

Maintenance May Become Easier

One advantage of random packing is often simpler replacement.

Individual pieces can be removed and replaced without reconstructing organized packing layers.

For plants with frequent shutdowns caused by contamination, this can reduce maintenance complexity.

Conversion Should Follow the New Operating Priority

A plant that originally prioritized maximum separation efficiency may later prioritize:

• fouling resistance;
• simple maintenance;
• lower replacement cost;
• operational robustness.

If the process requirement has changed, random packing may become a rational retrofit choice.