In petrochemical units, severe coking of crude oil occurs outside the tube bundles of high-efficiency heat exchangers used for constant pressure and reduced pressure operations, which greatly hinders the operation of these heat exchangers
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The image below shows the tube bundle of a high-efficiency heat exchanger used in petroleum chemical processes for constant pressure and vacuum distillation. In this setup, the tube side is used for constant pressure and vacuum distillation processes, while the shell side is used for crude oil； The operating temperature is 132 degrees in the tube side and 172 degrees in the shell side ； The pressure in the tube side is 0.71 MPa, and that in the shell side is 0.79 MPa. The tube bundle material is 10# steel. The outer surface of the tubes features pressed threads (to improve heat exchange efficiency); after being in use for over a year, severe coking occurred on the shell side, affecting normal operation. The high-efficiency heat exchanger becomes inefficient, reducing the heat exchange efficiency.
Due to the high content of heavy components in crude oil, it is prone to thermal cracking at high temperatures, resulting in the formation of coke and thus coking on the outside of the heat exchanger tubes. It is recommended to address this issue by regularly cleaning the tube bundles, reducing the operating temperature in the shell side, and using anti-coking materials or coatings. At the same time, optimizing the process design is considered to improve the efficiency of crude oil pretreatment and reduce the content of heavy components entering the heat exchanger, thereby minimizing coking. .
Indeed, how do I clean it?
This is caused by a low flow rate, as there are many mechanical impurities in the crude oil
Spiral plates can be considered, as they allow for a high flow rate