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50 APRIL 2017 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 56, NO. 4 CHEMICAL TREATMENT B Corrosion products such as iron sul- fides, iron oxides, and iron carbon- ates are the major constituents of black powder observed in the export gas handling facilities of Kuwait Oil Co. Acid gases, such as hydrogen sul- fide (H 2 S) and carbon dioxide (CO 2 ) together with oxygen (O 2 ), are benign in dry gas but highly corrosive when dissolved in water, either condensed or carryover water/glycol mixture. The resulting corrosion products, which consist of fine particles of several forms of iron oxides, sulfides, and car- bonates, form the basis for black powder. This article discusses black powder formation, mitigation, and prevention in export gas lines. Black powder deposits 1 are present in many locations, including the tank vapor compressor, low-pressure compressor (wet deposits), high-pressure compressor, heat exchanger, scrubbers, and glycol unit, as well as the export gas line. The deposits block control valves and drain lines from the scrubbers, filters, and driers. An effective gas filtration and separa- tion system for fine particles and droplets will not only mitigate equipment plugging and foaming in the absorption tower, it will also ensure high-quality gas transmission. The key to preventing black powder forma- tion is effective dehydration. Unfortunately, gas dehydration is not always successful because of design limitations and process upsets. Consequently, a judicious combina- tion of vapor phase corrosion inhibitors and periodic cleaning of pipelines normally supplement dehydration to reduce the black powder problem. Several removal and prevention methods are available to operators for managing the effects of black powder. West Kuwait Gas Lines The gas produced in the West Kuwait area is characterized by high levels of acid gases—hydrogen sulfide (H 2 S) (30,000 to 50,000 ppm) and carbon dioxide (CO 2 ) (30,000 to 40,000 ppm). In the export gas handling facilities of the Kuwait Oil Co. (KOC), sour gas with higher CO 2 content is compressed and dehydrated at local sta- tions. Two large crude gathering centers have the primary crude stabilization units, with gas compression/dehydration facili- ties located in the Minagish oil fields. The gas dehydration facilities use triethylene glycol (TEG) as a moisture absorbent and the TEG is continuously regenerated. The regeneration system is comprised of a gly- col regeneration column, glycol reboiler, and glycol surge drum. The regenerated TEG, after passing through a h eat ex- changer, is fed into the glycol contactor at 45 °C (113 °F). The dehydration plant is operated per the manufacturer's recommendations rela- tive to process indicator feedback. The key process control operating parameters in- clude inlet temperature, absorber temper- ature, pressure, and f low rate. The mini- m u m o p e r a t i n g t e m p e r a t u r e o f t h e dehydration plant is 45 °C and the TEG concentration is supposed to be main- Black Powder in Export Gas Lines o lago K e o labisi, DNV GL, Ahmadi, Kuwait s ale H a l- s ulai M an, a M e R j a RR ag H , y ouse F K H u R aibut, and a s H o K Mat H ew, Kuwait Oil Co., Ahmadi, Kuwait