TL;DR
Declining heat transfer in a jacketed reactor means fouling on the jacket side. Track the overall heat transfer coefficient trend and plan a jacket clean at the next opportunity.
What you might see
- heat transfer rate declining over time
- longer batch heat-up or cool-down time
- jacket supply and return temperature differential increasing
- jacket vent port showing scale deposits
Likely causes
Hard water scale (calcium carbonate) depositing on jacket inner surface
Corrosion products from jacket material accumulating at low flow areas
Heat transfer fluid degradation products depositing on the jacket wall
Air pocket trapped in the jacket reducing effective heat transfer area
Required tools
- Thermometer or thermocouple recorder for jacket temperatures
- Jacket fluid water quality test kit
- Circulation pump flow meter
Safety first
- Acid cleaning of the jacket circuit requires compatibility verification with the glass lining, nozzles, and gaskets. Always obtain engineering approval before introducing acid to the jacket.
- Jacket circuits on glass-lined reactors may be at elevated pressure during operation. Isolate the jacket steam or cooling supply before opening any jacket connection.
Procedure
- 1
Calculate the overall heat transfer coefficient (U) from the current batch temperature profiles. Compare to the value at commissioning.[1]
- 2
Review the jacket heat transfer fluid quality. Check calcium hardness and corrosion inhibitor concentration.[1]
- 3
Inspect the jacket vent point and drain for scale or particulate deposits.
- 4
Verify the jacket circulation pump flow rate is at the design value. Low flow worsens fouling and temperature uniformity.
- 5
If air pockets are suspected, vent the jacket at the highest point while the pump is running.
- 6
If scale fouling is confirmed, plan a jacket acid clean (dilute citric acid or similar) during the next product campaign break. Follow the vessel material compatibility requirements for the glass-lined vessel.
- 7
Implement a water treatment program for the jacket circuit to prevent recurrence.
Sources
Pfaudler Pfaudler RA / RT glass-lined Reactor / Pressure Vessel general technical documentation, Pfaudler
Pfaudler RA / RT glass-lined reactor general jacket maintenance and heat transfer procedures (general)
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Iron contamination in the product or a failed spark test confirms glass lining damage. Schedule a spark test inspection during the next cleaning cycle and assess for repair or re-lining.
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