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South Korean Petrochemical CompanyExapilot Automates Naphtha Cracker Decoking and Dryer Regeneration Processes at Large Ethylene PlantExecutive SummarySouth Korea’s petrochemical company is located in the town of Yeosu. The plant started from 350,000 tons of ethylene per year production and expanded to 1,000,000 tons per year now. There are twelve naphtha cracking furnaces in this plant. The naphtha used as the feedstock for this plant is fed to a pyrol-ysis (steam cracking) furnace, where it is combined with steam and heated to 980 to 1,080 deg C. Within this temperature range, the feedstock molecules "crack" to produce ethylene as well as methane, hydrogen, ethylene, propylene, butadiene, benzene, toluene, xylene, and other co-products. After the pyrolysis reaction is quenched, the rest of the plant separates the desired products into streams that meet the various product specifications. The process steps include distillation, compression, process gas drying, hydrogenation (of acetylenes), and heat transfer.All of the processes at this ethylene plant are controlled by a Yokogawa CENTUM CS3000 pro-duction control system that was engineered, installed, and commissioned by Yokogawa Korea. To further enhance operations at this plant, Yokogawa Korea introduced the Exapilot operation efficiency improve-ment package in 2006.The Challenges and the SolutionsAutomation of naphtha cracker decokingThe pyrolysis reaction process in the ethylene plant employs naphtha cracking units (NCU), quench units, compressors, and dryer-equipped separators. The NCUs’ operating temperature is carefully controlled to ensure efficient production. During the pyrolysis reaction, coke forms inside the NCU coils, resulting in decreased heat transfer and a decline in reaction efficiency. In the worst case, the coils can crack or rupture. To prevent this from happening, the plant operators need to perform a decoking process. For each of the twelve NCUs in this ethylene plant, this must be done either every 60 days that the furnace is in operation or when the furnace temperature reaches 1,080 degC, whichever comes first. An important consideration in this is scheduling as the plant’s operators in the central control room have a very demanding workload.Plant InformationLocation: Yeosu, South KoreaOrder date: July 2003Completion: May 2004 (CS 3000) + 2006 (Exapilot)Pyrolysis reaction processChemical (Base Chemical, Fertilizer, Petrochemical)55Success Story Collection

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