An extensive study has been executed to understand the mechanism of calcite scale deposition occurring in the main heat exchanger at the MPP (main production platform) facilities at SVSA. The deposit necessitated a change out of the internals of the heat exchanger, which caused production deferment and capital expenditures.

The conclusion of this investigation was that the mechanism for accelerated calcite scale build-up in the HX heat exchanger is driven by the considerably high skin temperature (above 120 °C at normal heating conditions) in a high pH environment. This latter is caused by the triazine, which is part of the H2S scavenger package (used to remove H2S from some of the sour gas production), and by-products originating from the reaction of triazine (an amine) with H2S. The CaCO3 scaling tendencies and indices as calculated by scaling software (ScaleChem, StreamAnalyzer) predict the adverse impact of the high temperature and alkalinity conditions encountered in the heat exchanger.

Several technical options to mitigate the effects of the scavenger were considered from an economic and operational perspective. The most effective of the options was the injection of an appropriate scale inhibitor at a suitable dosage upstream of the heat exchanger.

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