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• Lean Amine (MDEA) from Amine Regenerator bottom pre-heats the feed to regenerator and then is pumped to users while passing through Air Fin cooler (AFC). A slip stream is sent to pre-coat filter and filtered MDEA joins the rundown. We are facing high MDEA rundown temp (>75 degC) due to internal fouling of the rundown Air fin cooler (AFC) which is designed to reduce MDEA temp from 104 degC to 60 degC. MDEA rundown results is as follows: Fe (5-6 ppmw), HSS (1.5-2.0), Na (400-500 ppmw), TSS (200-400 ppmw). There is no trim cooler at downstream of AFC. There is a HSS removal  from MDEA skid which was recently commissioned in Mar'23. What could be the reason for fouing of AFCs? Is there any reference of online cleaning of Lean Amine AFC without impacting the quality?

  Mar-2024

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Answers

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

  Considering the analysis results for lean amine presented in the question it seems that your processing unit is suffering corrosion and fouling process due to high concentration of Heat Stable Salts (HSS).

  It's possible to see a high iron concentration (5 to 6ppmw) in the lean amine which evidentiate concentration of HSS is around 3 to 4 times of the recommended by the literature (0,5 wt % maximum). The heat stable salts (HSS) tends to hold the iron in solution avoiding the creation of passivating film which exposes the metal to corrosion process, the sodium concentration indicates that is not occurring caustic over injection to neutralize the heat stable salts, a suggestion is analyse if the current dosage is sufficient.

  Another suggestion, is to analyze the efficiency of the lean amine filter and, according to the result, change the filter element mesh to stricter values (a typical case is to reduce the filter mesh from 10 to 5 micron). Regarding the online cleaning process of AFC, I don't have knowledge about these technologies.

   

  Apr-2024