We have LPG caustic wash and water wash systems.Similarly,we have Naptha caustic wash and water wash systems.Frequent caustic carry over in product LPG and Failures in copper corrossion due to exhausted caustic solutions is a operational problem.Is there any continuous monitoring instrumentation available to check circulating caustic strength in caustic wash system? Similarly any instrumentation exists for monitoring recirculating wash water for caustic carry over symptom needing wash water replacement?
If so advise/share
Answers
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08/02/2016
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Lindsay McRae, Pall Corporation, Lindsay_McRae@pall.com
Measuring caustic carryover on-line is difficult. There is certainly a test for measuring it in the laboratory. One proven way to remove carried over caustic causing Cu strip test failures is to use a High Efficiency PALL PhaseSep Liquid Liquid coalescer. Less than 0.5ppmw Na+ can be obtained downsteam of PALL PHASESEP Liquid Liquid coalescer technology. This technology is much more efficient than mesh pad, sand coalescer or other devices sometimes used. This can be a very stable emulsion so the separation is often a difficult one. PhasesSep coalescer can separate even very stable emulsions with an Interfacial Tension as low as 0.5 dynes/cm
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07/02/2016
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Egbert van Hoorn, Hocon B V, Egbertvh@hotmail.com
Caustic carry over from LPG treaters and copper strip failures needs to be handled at the root cause:
Is the equipment adequate?
More importantly, what are the reasons for the entertainment?
Is the upstream amine unit working correctly?
The upstream amine unit can cause entertainment in the downstream caustic units. This is a problem which is poorly understood in the industry.
Please let me know if I can help you further.
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04/02/2016
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Stefan van der Wal, Mettler-Toledo Process Analytics, stefan.vanderwal@mt.com
The concentration of the caustic in the caustic wash circulation can be monitored easily through conductivity measurement. Sensors of the inductive type are needed here as they are insensitive to (hydrocarbon) fouling.
Caustic carry-over in the water wash is detected fastest with an inline pH measurement.
Both conductivity and pH measurements are very common in these operations (also sulfuric acid type alky units, ethylene quench sections etc.)
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04/02/2016
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Vijay Beleri, Rateau energy systems, v_beleri@hotmail.com
Are you using a electrostatic coalescer in the stream? We have seen caustic addition, mixing followed by electrostatic coalescence that takes the water and salts away.
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