Abstract: The problem of rapid efficiency decrease of the high pressure heat exchanger for product and raw material in the coking gasoline/diesel hydrotreating unit in CNOOC Huizhou Petrochemical Co. Ltd. was analyzed based on the operation parameters and heat exchanger fouling mechanism. It is thought that the problem is caused by fouling in shell-side of the heat exchanger B and can be solved by adding scaling inhibitor into raw materials, which effectively delays the scaling and slows down further the decline of the heat transfer efficiency. Long-term operation shows that the inhibitor has no obvious effect on the pressure drop of the catalyst bed and does not affect the quality of the diesel product.

Key words: high pressure heat exchanger, shell-side, scaling, scale inhibitor