Abstract

Abu Dhabi Gas Liquefaction Company Ltd (ADGAS) operates three sulphur recovery units (SRU). Units are aimed at reducing acid gas flaring. Sulfur is produced from these units. Units follow the Calus and Super Calus process. Each unit is composed of a main combustion chamber, waste heat boiler, series of condenser, reactors, line heaters and an incinerator. In one of the SRU units, one of the sulphur condensers had a tube failure. Failure investigation showed that one tube failed externally (water side). Tube internal surface revealed no tube degradation. Root Cause Analysis exercise revealed that failure was attributed to a corrosion assisted steam blanketing phenomenon. Damage was only confined to the first few centimetres away from the tube sheet hot side. Furthermore signs of Boiler Feed Water (BFW) corrosion was there. Corrosion control of the BFW quality was ensured through continuous intermittent blow down of the condensed BFW in addition to introducing an additional chemical injection skid to control the BFW quality in the SRU. These actions were able to control the quality of the BFW. Furthermore, ADGAS initiated a Computational Fluid Dynamics Exercise (CFD) through a specialised consultant to understand the possible scenario of the steam blanketing. CFD was done for normal operation ns cases in addition to transient conditions. CFD was able to prove that steam blanketing actually took place during one of the transient conditions. Actions were hence considered to prevent the recurrence of such transient condition.

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