What Can Be Decided When a Packed-Tower RFQ Does Not Include the Required Bed Height?

Industrial packed-tower inquiries are often incomplete.

A buyer may provide the column diameter, gas flow, operating temperature, gas composition, circulating-liquid rate, and even a target outlet concentration, but leave out one critical parameter:

the required packed-bed height.

At this point, suppliers face an important engineering boundary.

Should they recommend a packing immediately? Should they calculate a bed height? Or should they refuse to proceed until the missing information is available?

The correct answer depends on what the available process data can genuinely support.

Packing Type and Bed Height Are Different Decisions

Selecting a suitable packing family is not the same as determining how much packing is required.

From the operating conditions, an engineer may often make a preliminary judgment about:

• suitable packing material;
• probable packing geometry;
• corrosion requirements;
• hydraulic suitability;
• fouling risk;
• approximate packing size.

But these decisions do not automatically establish the required bed height.

Bed height is closely connected to the required mass-transfer duty.

That duty depends on factors such as:

• inlet concentration;
• outlet target;
• gas flow;
• liquid composition;
• equilibrium behavior;
• reaction chemistry;
• effective mass-transfer performance.

A supplier should therefore separate material and hydraulic screening from final process sizing.

What Can Be Evaluated Without Bed Height?

Even when bed height is missing, useful engineering work can still be performed.

Material compatibility

If the process gas contains HCl, SO₂, alkaline vapor, solvents, or other corrosive components, candidate materials can be screened.

Possible materials may include:

• PP;
• PVDF;
• ceramic;
• stainless steel;
• corrosion-resistant alloys.

Temperature and chemical compatibility can be reviewed before bed height is known.

Hydraulic suitability

If gas flow, tower diameter, and liquid circulation rate are available, the supplier can evaluate whether a proposed packing geometry is likely to provide an appropriate hydraulic window.

This can help identify whether the application favors:

• more open packing;
• higher-capacity geometry;
• smaller high-area packing;
• larger fouling-resistant packing.

Mechanical feasibility

Column diameter can be used to review:

• practical packing size;
• support requirements;
• wall-effect concerns;
• loading method.

These are useful decisions even before process sizing is completed.

What Cannot Be Confirmed Reliably?

Several conclusions should normally remain provisional.

Final packing quantity

Without the required bed height, the total packing volume cannot be finalized.

Packing volume is approximately linked to:

column cross-sectional area × packed height

If the packed height changes from 2 meters to 4 meters, the material quantity changes dramatically.

Guaranteed outlet performance

A supplier should not claim that a proposed packing will achieve a specific removal efficiency unless the mass-transfer design supports that statement.

The packing material may be suitable, but insufficient bed height can still cause the tower to miss the outlet target.

Final pressure drop

Pressure drop per meter may be estimated from hydraulic data, but the total packed-bed pressure drop also depends on bed depth.

Without bed height, only a unit-height estimate may be possible.

Why Guessing the Bed Height Is Dangerous

Some quotations attempt to solve missing information by assuming a “typical” packed height.

This may make the quotation look complete, but it introduces hidden risk.

A typical height from another scrubber may not apply because:

• inlet concentration is different;
• absorption chemistry is different;
• gas flow is different;
• removal target is different;
• liquid chemistry is different;
• packing efficiency is different.

A three-meter bed that works in one system may be completely inadequate in another.

A Better Preliminary Engineering Response

Instead of pretending that all design parameters are known, the supplier can divide the recommendation into two levels.

Level 1 — preliminary product recommendation

This may include:

• proposed packing family;
• material;
• nominal size;
• expected advantages;
• hydraulic considerations;
• support and distributor concept.

This recommendation should clearly state that it is based on currently available conditions.

Level 2 — final process design

This requires the remaining process information needed to determine:

• packed height;
• number of beds;
• total packing volume;
• final pressure drop;
• expected process performance.

This separation allows the project to continue without creating false precision.

What Information Should Be Requested Next?

If bed height has not already been determined by the process designer, the supplier should request sufficient data to understand the mass-transfer requirement.

Typical information includes:

• inlet component concentration;
• required outlet concentration;
• gas flow at operating conditions;
• pressure;
• temperature;
• liquid flow;
• liquid composition;
• absorbent type;
• relevant physical properties;
• existing process calculation if available.

For reactive absorption, reagent concentration and reaction chemistry may also be important.

What if the Client Is an EPC or Equipment Manufacturer?

In many projects, the packing supplier is not responsible for complete process design.

The EPC or scrubber manufacturer may already have calculated the required packed height.

In that case, the most efficient question is simply:

“Please confirm the required packed height or packing volume from your process design.”

This prevents the packing supplier from unintentionally taking responsibility for a process calculation outside the agreed scope.

What if the Client Wants the Supplier to Calculate It?

Then the design scope must be expanded.

A real process calculation may require:

• mass-transfer model;
• equilibrium data;
• reaction assumptions;
• packing performance correlations;
• hydraulic verification.

This is different from simply quoting packing.

The commercial and technical scope should reflect that difference.

Avoid Turning a Product Quotation into an Uncontrolled Process Guarantee

This is one of the most important lessons in industrial RFQ handling.

A supplier can often provide useful engineering guidance from incomplete data.

But guidance should not become an unsupported guarantee.

The correct approach is to identify which parameters are:

• confirmed;
• assumed;
• provisional;
• still required.

This makes the quotation technically stronger, not weaker.

Final Engineering Principle

Missing bed height does not mean that the entire project must stop.

Material selection, hydraulic screening, packing geometry, and mechanical feasibility can often be evaluated first.

However, final packing quantity and guaranteed mass-transfer performance should remain open until the required bed depth has been established.