Introduction to crude oil coking in petrochemical heat exchangers, specifically those used for heat exchange with residue oil
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The image below shows the tube bundle of the heat exchanger used for exchanging heat between crude oil and residue in the petrochemical industry. The tubes inside this bundle developed coking after less than 2 years of use. The operating conditions for this tube bundle are as follows: the fluid flowing through the inner tubes is crude oil, while the fluid flowing through the outer tubes is residue； Temperature: 120°C in the tube side, 160°C in the shell side ； Pressure: 1.88 MPa on the tube side, 1.37 MPa on the shell side. Material: tube bundle made of 10# steel.
In the petrochemical industry, crude oil and residue heat exchangers often face coking problems, especially under high temperature and certain pressure conditions. Under the operating conditions you provided, the temperature of the crude oil in the tube side is 120°C, while the temperature of the residue oil in the shell side is 160°C. This temperature difference can lead to the gradual accumulation of heavier components in the crude oil on the tube walls, where they carbonize to form coke. Crude oil contains various light and heavy hydrocarbons, with the heavier hydrocarbons tending to aggregate and decompose under high temperatures to form solid coke. These coals adhere to the inner walls of the heat exchanger, not only reducing the heat exchange efficiency but also potentially causing pipe blockages, which increases the difficulty and cost of maintaining the equipment. To reduce coking, optimizing operating conditions such as appropriately reducing the temperature difference, increasing the flow rate of crude oil, or using coking-resistant pipe materials and coatings can be considered. Regular cleaning and maintenance are also necessary to maintain the proper operation of the heat exchanger. .