Troubleshooting and Solving a Sour Water Stripper Problem

摘要

A Sour Water Stripper in a gas processing plant was designed to strip 35 m3/h (154 gpm) ofsour water containing approximately 650 ppmw H2S to a bottoms purity of less than 5 ppmw.Upon start-up, the column could only achieve a feed flow rate of 20 m3/h (88 gpm). Anyincrease beyond this would initiate flooding. Several theories were proposed to explain thepremature flood.A systematic investigation combining field testing and hydraulic analysis eliminated abouthalf the theories, leaving foaming and damage as the frontrunners. A plant test wasperformed in which the liquid loads were raised at a constant vapor load. The test showed theflood to be vapor-sensitive and liquid-insensitive. When combined with the hydraulicanalysis, the test provided strong evidence that supported the column internals damagetheory.The tower was shut down and inspected, and one of the upper trays was found to bedamaged. The damage unsealed one of the upper downcomers. Interference of rising vaporwith the descending liquid in the unsealed downcomer was proposed as the explanation to theflood. This explanation is consistent with a vapor-sensitive flood. The damage was repairedand the tower achieved design performance. The most likely cause of the damage wasthought to be entry of cold water during start-up.One lesson learned is the importance of using hot feed during start-up of steam-watersystems. If cold feed is used, any sudden feed surges or feed temperature drop may causerapid condensation near the column inlet and consequent column internals damage. Anotherlesson learned is that contrary to some literature references, Sour Water Strippers are notalways foaming. The column investigated was not adequately designed to handle foaming,yet achieved the design capacity after the damage was repaired.