Severe coking occurs outside the tube bundle of the heat exchanger for crude oil and residue in petrochemical light and heavy vacuum distillation processes
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The image below shows the tube bundle of the heater for crude oil and residue oil in petrochemical vacuum distillation units. Model is FB800-170-40-2, with the tube bundle made of 10# steel. The operating condition is that the tube side contains crude bottom oil, while the shell side contains residue oil ； The operating temperature is 270 degrees in the tube side and 305 degrees in the shell side ； The pressure in the tube side is 2.12 MPa, and that in the shell side is 1.70 MPa. This tube bundle has been in use for over a year, and the outer wall of the tubes has suffered severe coking, which has affected the heat exchange efficiency of the heat exchanger. It can be seen from the exposed metal surface that there are many pitting defects. Atmospheric residue contains elements such as sulfur, nitrogen, and oxygen, as well as metal compounds. The presence of these elements and compounds affects the quality of residue oil and the difficulty of its processing, while also causing significant corrosion to metals. The corrosion of residue is much more severe than that of crude oil.
The corrosion of the tube bundle and coking caused by residue at high temperatures can lead to a decrease in heat exchange efficiency. It is recommended to clean the tube bundles regularly and consider using materials that are more resistant to high temperatures and corrosion, such as stainless steel, in order to improve the stability and service life of the equipment. At the same time, optimizing process parameters and controlling the flow rate and temperature of residue and vacuum residue within the tube bundle can also effectively reduce coking and corrosion. .