How Engineers Benchmark Packed Tower Performance Against Expected Performance

A packed tower can continue operating while gradually losing performance.

For example:

• pressure drop slowly increases;
• energy consumption rises;
• separation efficiency decreases.

However, without a reference point, engineers may not recognize the degradation.

The engineering question is:

How do engineers determine whether a packed tower is performing as expected, below expectation, or better than expected?

The key principle is:

Performance benchmarking compares actual tower behavior against a defined reference condition to identify improvement opportunities and hidden degradation.

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Why Performance Benchmarking Matters

A tower that is still producing product may not be operating optimally.

Benchmarking helps identify:

• performance loss;
• unnecessary energy consumption;
• remaining improvement potential.

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1. Define the Performance Reference

Possible benchmarks include:

Design Basis

Original engineering design.

Historical Best Operation

Best proven plant performance.

Similar Equipment

Comparable operating systems.

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2. Benchmark Hydraulic Performance

Engineers compare:

• pressure drop;
• flooding margin;
• operating load.

Questions:

• Is ΔP higher than expected?
• Is capacity lower than design?

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3. Benchmark Mass-Transfer Performance

Compare:

• outlet concentration;
• removal efficiency;
• product quality.

A tower may have acceptable hydraulics but poor separation.

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4. Benchmark Energy Performance

Review:

• fan power;
• pump energy;
• steam consumption.

Two towers may produce the same result but consume different energy.

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5. Consider Operating Conditions During Comparison

Performance comparison must consider:

• gas flow;
• liquid flow;
• temperature;
• pressure;
• composition.

A direct comparison without conditions can be misleading.

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6. Identify Performance Gap

Example:

Expected:

ΔP = 250 Pa/m

Actual:

ΔP = 400 Pa/m

Gap:

investigate possible causes.

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7. Separate Equipment Limits From Operation Issues

Poor performance may result from:

Equipment:

• packing condition;
• distributor.

Operation:

• excessive load;
• changed process conditions.

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8. Use Benchmarking Before Revamp Decisions

Before replacing equipment, engineers ask:

• Is the tower truly underperforming?
• Where is the gap?
• Can operation improvement solve it?

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9. Use Benchmarking for Continuous Improvement

Repeated benchmarking can track:

• improvement after modification;
• degradation over time.

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10. Benchmarking Requires Reliable Data

Good benchmarking needs:

• accurate measurements;
• consistent operating conditions;
• correct design information.

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Example 1 — Pressure Drop Benchmark

Design:

200 Pa/m

Current:

350 Pa/m

Flow unchanged.

Conclusion:

possible fouling or hydraulic degradation.

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Example 2 — Absorber Efficiency Benchmark

Historical best:

98% removal.

Current:

94%.

Investigation:

operating condition or distribution change.

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Example 3 — Energy Benchmark

Two operating modes:

Same removal efficiency.

Mode A:

higher pump power.

Optimization opportunity identified.

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Packed Tower Performance Benchmarking Workflow

Define Reference Condition

↓

Collect Actual Performance Data

↓

Normalize Operating Conditions

↓

Compare Performance

↓

Identify Gap

↓

Investigate Cause

↓

Improve Operation or Equipment

↓

Maintain High Performance

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Performance Benchmarking Checklist

Reference

✓ Design data✓ Historical data✓ Comparable equipment

Hydraulic

✓ Pressure drop✓ Capacity✓ Flooding margin

Process

✓ Efficiency✓ Outlet quality✓ Separation target

Energy

✓ Power consumption✓ Operating cost

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Common Benchmarking Mistakes

Mistake 1 — Comparing Without Matching Conditions

Why it fails:

Different loads create different performance.

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Mistake 2 — Using Only Design Data

Why it fails:

Actual operating history may provide better reference.

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Mistake 3 — Ignoring Energy Performance

Why it fails:

A tower can meet specification inefficiently.

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Mistake 4 — Treating Any Difference as Failure

Why it fails:

Some differences are caused by normal variation.

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Mistake 5 — Benchmarking Without Action

Why it fails:

Comparison alone does not improve performance.

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Performance Benchmarking vs Related Nodes