Corrosion has occurred on the tubes of the heat exchanger
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Process parameters:Tube side: Propylene gas; Feed temperature: 70°C; Temperature after condensation: 45–65°C.
Shell side: Circulating water; Inlet water temperature: 15–30°C; Outlet water temperature: 45–65°C.
The heat exchanger is a propylene condenser with a diameter of 1200 mm and a length of 8000 mm; it contains 981 heat exchange tubes. The specifications of these tubes are 25*2.5*8000, and they are made of 20# material. The shell side is made of 345R material.
Circulating water parameters: pH around 8.3; conductivity less than 2000; the concentration ratio is approximately 2. The turbidity varies but remains within 20 units; iron ion levels range from 1.5 to 4.
Problem: When the tubes of the heat exchanger were removed, it was found that they were severely corroded, with small holes formed in them; some of these holes were even through-the-wall, indicating pitting corrosion. However, the scaling in our circulating water is under good control. We outsource the management of our circulating water system; that is, we follow the instructions provided by the water treatment manufacturers, who usually conduct inspections at regular intervals. Dear sea friends, please analyze whether this is caused by the material or by poor water quality
There’s no problem with the material; many factories use it this way! There are issues with water quality control, but you’ve provided too few parameters! “ “Iron ions = around 1.5~4” indicates severe corrosion in the system; generally, it should be kept below 1.0. It should be considered from the perspective of water quality control! What should the total phosphorus level in the system be? Please provide detailed information on the system parameters!
If water quality control is fine, it can be seen that the circulation volume is a bit low. With an inlet water temperature of only 15–30°C and an outlet water temperature of 45–65°C, the heat exchange efficiency is not very good. The concentration ratio is quite low, and the amount of water added is also large; is the dosage of the chemical properly controlled? Whether the total phosphorus control is up to standard.