Why Does a Sulfuric Acid Distributor Deliver Uneven Flow During Plant Operation?

A sulphuric acid distributor that delivered perfectly even flow at commissioning can slowly lose that evenness once the plant is running. The change is gradual, so it is often noticed only when tower efficiency has already slipped. Understanding why uneven acid flow develops during operation is the key to correcting it early.

Problem: Even Flow That Quietly Fades

At start-up, a well-made distributor spreads acid uniformly. Months or years later, the same unit may deliver noticeably different quantities from point to point. The tower then runs with dry and flooded zones, and operators compensate by raising the circulation rate or accepting lower efficiency. The underlying uneven acid flow is a symptom, not a cause, and it points to a change that has occurred inside the distributor or the circuit.

Cause: What Changes After Commissioning

Several mechanisms can disturb uneven acid flow during service:

• Loss of levelness — thermal cycling and vibration can move troughs or pipe runs out of level, favouring one side of the tower.
• Orifice change — partial blockage or corrosion-driven enlargement both alter the flow at individual points.
• Distortion under load — hot concentrated acid softens and slowly deforms thin sections, changing internal clearances.
• Circulation changes — if the acid rate drifts outside the distributor's design turndown, the distribution pattern itself shifts.

Engineering Solution: Restore and Hold Evenness

The fix depends on the cause, but it always starts with measuring the actual flow pattern across the cross-section. Where levelness has drifted, re-levelling restores the design pattern. Where corrosion is the driver, upgrading to an anodic protection acid distributor stops the dimensional change at its source, so the even flow the unit was built with is held year after year. Selecting geometry with adequate turndown within the Sulfuric Acid Distributor range keeps distribution even when plant rates vary.

Application

Operating drift affects drying towers that run at varying gas loads and absorption towers that follow plant throughput. Towers that experience frequent thermal cycling or shutdowns are the most likely to see levelness change, while towers on aggressive acid see orifice change first.

It is worth distinguishing between a change in the acid and a change in the distributor. If the circulation rate has drifted outside the design range, restoring the original flow may bring the pattern back on its own. If the rate is unchanged but the pattern is still uneven, the cause lies inside the unit — levelness, orifice condition or distortion. Recording the acid rate alongside the observed performance whenever efficiency is reviewed makes that distinction straightforward, and it turns a vague complaint about uneven flow into a specific, correctable fault.

Technical Checklist

• Current acid circulation rate versus the distributor's design range
• Levelness across troughs, weirs or pipe runs
• Individual orifice condition and evidence of corrosion
• Operating and upset temperature history
• Material grade and protection method
• Access for re-levelling and inspection

FAQ

Why was distribution even at start-up but not now?

Because the distributor itself has changed — through levelness drift, orifice change or corrosion-driven distortion. Commissioning results describe a new unit, not a used one.

Can uneven flow be corrected without replacing the distributor?

Sometimes. Re-levelling and cleaning can restore an otherwise sound unit; where corrosion has moved the geometry, replacement with a protected design is the durable answer.

Does flow rate affect distribution evenness?

Yes. Below the design turndown, the trough or pipe network cannot spread acid evenly. Keep operation inside the distributor's rated range.

Get a Selection Recommendation

Send us the tower diameter, acid concentration, operating temperature, design flow rate and the history of your existing equipment. We will help identify whether re-levelling, refurbishment or a protected replacement is the right answer for your uneven acid flow.