In petrochemical units, significant coking occurs on the outer wall of the tube bundles in the crude oil heat exchangers used in atmospheric and vacuum distillation processes
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The image below shows the tube bundle of the crude oil heat exchanger in the atmospheric and vacuum distillation unit of the petrochemical industry. The model is FB700－95－25－4, and the tube bundle material is 10# steel. The operating condition is that the tube side is constant temperature at 2°C, while the shell side contains crude oil ； The operating temperature is 246.1 degrees in the tube side and 118 degrees in the shell side ； The pressure in the tube side is 0.818 MPa, and that in the shell side is 2.316 MPa. This tube bundle has been in use for over a year; crude oil flows in the shell side, causing a significant amount of crude oil residue to accumulate on the outer wall of the tube bundle, which affects the efficiency of the heat exchanger.
Crude oil is prone to thermal cracking at high temperatures, resulting in the formation of heavier hydrocarbons, which deposit on the outer wall of the tube bundle and cause coking. It is recommended to clean and inspect the heat exchanger regularly to maintain its heat exchange efficiency. At the same time, optimizing the temperature and flow rate of the crude oil can be considered to reduce the likelihood of coking. .