External corrosion and scaling of the heat exchanger tube bundles in the constant pressure and reduced pressure units of petrochemical plants, Line 1 and Line 3
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The images below show the heat exchanger tube banks of the Constant Pressure/Reduced Pressure Line 1 and Line 3 in the petrochemical industry. Model is FLB500-55-25-2, with the tube bundle made of 10# steel. The usage condition is that the tube side has a constant three-wire configuration, while the shell side has a constant one-wire configuration ； The operating temperature is 330 degrees in the tube side and 180 degrees in the shell side ； The pressure in the tube side is 1.1 MPa, and that in the shell side is 0.8 MPa. This tube bundle has been in use for over 2 years, and the anti-erosion plates on its outer wall are severely corroded; some of them have completely corroded away, rendering the tube bundle completely ineffective. Common first-line oils have relatively low boiling points and lighter compositions; they mainly include jet fuel (aviation kerosene), lamp kerosene, solvent oils, raw materials for fertilizers, feedstocks for ethylene cracking, or special diesel fuels. Often, surface corrosion is influenced by H2S-HCl-H2O, leading to corrosion of the metal surface.
Due to the different operating conditions of the primary and tertiary lines, the outer wall of the heat exchanger tube bundle is prone to corrosion and scaling under the influence of high temperatures and chemical components. In particular, the oils and fuels in the main pipelines often contain corrosive gases such as H2S and HCl; when combined with water vapor, these gases cause more severe erosion of metals, leading to serious corrosion of the anti-erosion plates on the outer walls of the pipe bundles, and even their failure. Furthermore, high temperatures can also accelerate the formation of scale, further affecting heat transfer efficiency and equipment lifespan. The tube bundles need to be regularly inspected and cleaned, and considering the use of more corrosion-resistant materials or coatings can improve the durability of the equipment. .