In the atmospheric and vacuum distillation units of the petrochemical industry, coking of crude oil occurs on the shell side of the heat exchanger tubes in the crude oil first-line system
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The image below shows the heat exchanger tube bank of the atmospheric and vacuum distillation unit in the petrochemical industry, for crude oil. Model: FB700-120-25-4, Material: 10#, Operating conditions: Shell side: crude oil, temperature 138°C, pressure 0.8 MPa. Tube side: Medium, usually two-phase, temperature 186°C, pressure 0.94 MPa. During maintenance, when the heat exchanger was opened, it was found that coking of crude oil in the shell side was quite severe. How can such phenomena be avoided?
Coking often occurs when crude oil is at high temperatures and under certain pressures. The following methods can be used to try to avoid or reduce coking: 1. Lower the temperature: Try to control the operating temperature of the oil in the heat exchanger, so as to prevent it from exceeding the thermal stability range of the crude oil. 2. Increase flow rate: Raising the flow rate of the oil through the heat exchanger can effectively reduce the residence time of the oil on the shell side, thereby decreasing the chances of thermal decomposition. 3. Regular cleaning: Clean the heat exchanger periodically to remove any coke that has formed, thereby preventing the gradual accumulation of coke from worsening the situation. 4. Use anti-coking additives: Additives that can improve the thermal stability of crude oil are used to help prevent or slow down the coking process. 5. Selection of equipment materials: Consider using materials that are more resistant to high temperatures and coking in the design of heat exchangers, such as nickel-based alloys. Through the above measures, crude oil coking in the shell side of the heat exchanger can be effectively controlled and reduced, thereby extending the equipment’s service life and improving operational efficiency. .