How does the MCC (metal-catalysed coking) phenomenon happen in a high temperature fired heater in CCR unit, and how to protect?
Answers
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17/04/2012
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A:
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Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
From my course manual:
"Coke formed in the furnace tubes can migrate to the reactors and lodge behind the scallops or
baskets. The coke deposits can grow until the scallops or baskets are deformed, affecting catalyst circulation. Carburization of the furnace tubes can result as well, a mechanism by which carbon atoms diffuse through the matrix of a metal and crystalizes. This phenomenon results in loss of malleability during thermal stress, leading to tube failure. A solution to both the coke formation and the carburization phenomena is to maintain a trace of sulfur in the feed by injecting dimethyldisulfide (DMDS). A target of 0.3-0.5 wppm in the feed is often used."
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