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• There is any safe limit for chlorine for DCU feed?

  Jul-2024

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Answers

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• Marcio Wagner da Silva, Petrobras, marciows@petrobras.com.br

  According to my experience, some refiners are considering a chloride content below than 5 ppm (in mass) in the delayed coking feed as a safe limit to avoid corrosion issues, especially in the cold areas of the processing unit like the main fractionator top section.

  The corrosion control is more effective considering the chloride content in the sour water accumulated in the vessel in the top of  the main fractionator once this is the main area which suffers with  chloride salt deposition, mainly the NH4Cl. The chloride content is related with the salt deposition temperature which needs to be controlled above the operating temperature of the top section of the main fractionator, the chloride content in the top vessel of the main fractionator should be controlled below than 4,0 ppm.

  A good way to ensure these chloride limits in the delayed coking units is to control the performance of the desalting section of the crude oil distillation unit defining adequate chloride levels in the desalted crude and monitoring this parameter frequently as a critical parameter.

  Special attention should be done to refiners processing high nitrogen content crude oils once the high nitrogen concentration will lead to higher concentrations of NH4Cl.

   

  Jul-2024