Shell and tube heat exchanger progression fouling and its mitigation using chemical cleaning process

The heat exchanger calcium sulphate fouling in tube side is the deposition on the tube surfaces which affect the heat transfer. It’s found that the oil refinery process plant having an issue of calcium sulphate fouling in heat exchangers due to the crude product which form by hydrous calcium with Sulphur trioxide developed calcium sulphate deposit. The crystalline form of aqueous solution in three forms: gypsum (CaSO4⋅2H2O), hemihydrate (CaSO4⋅½H2O), and anhydrate (CaSO4), which is created by reacting Sulphur trioxide with calcium oxide in the presence of moisture in hydrous form (i.e. CaO+SO3 +2H2O=CaSO4·2H2O and CaO+SO3→CaSO4) form. Calcium sulfate deposits as a crystalline mass which adheres tenaciously to the metal surface, builds up and tends to undesirably reduce the heat transfer characteristics as well as causes plugging. The heat exchanger fouling removal are difficult which is not remove by any normal online cleaning and flushing. The objective of this work is to provide essential understanding of calcium base fouling removal techniques by EDTA chemical cleaning methodology. The mechanical cleaning, needs major shutdown, bundle pulling and retro-jetting which associated with huge cost and additional integrity test. The results of an experimental study on fouling phenomena, environment of fouling, and mitigation of fouling in shell and tube heat exchanger have been clearly explained.