Process Area Event – [So That’s How It Is-038]: The Pipeline Is Finally Unblocked

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This post was last edited by *lihuagong on 10-28-2016 at 13:09. The continuous reforming unit utilizes IFP technology; the production process for high-octane gasoline involves separating the distillate from the depentanizer tower, after which it enters a pentane tower where it is further separated into liquefied gas and pentane oil. The reflux tank at the top of the pentane tower is equipped with a water removal device that detects the level of water. During normal operation, there is almost no water in this device, so the water removal valve remains closed most of the time, with dehydration being carried out only on a regular basis. One year after the unit started operating, problems were encountered during regular dehydration attempts – the pipes were blocked. After various attempts failed, the tower was shut down and the drain valve was opened; it was found that the pipeline from the flange of the water removal device to the drain valve was completely filled with salt crystal particles. A temporary water supply line was connected at the water cooling outlet, and water was poured into the reflux tank to soak the area. After one day and night, the pipes were cleared and made functional again. Sampling analysis showed that the main component of the crystalline salt is ammonium chloride. Cause analysis: To adjust the water-chlorine balance in the reforming catalyst, chlorine was added to the reforming feed based on the water content in the recycled hydrogen. Most of the chlorine entered the gas phase and was removed in the hydrogen dechlorination tank; however, the oil produced by reforming still contained a small amount of chlorine. Although the reforming feed underwent hydroprocessing, it still contained a small amount of nitrogen, and over time this led to the formation of ammonium chloride crystals that blocked the pipelines. Experience: A water washing pipeline was installed before air cooling, and water is used for washing every six months; production has proceeded smoothly to date.