During the production of ethylene many contaminants are formed and distributedthroughout the system. These contaminants are usually classified into organic and inorganiccompounds. Organic foulants are the result of complex chemical reactions and may containsulfur, nitrogen and oxygen. Oxygen-containing materials are often further oxidized to organicacids.The cracked gas stream going overhead in the Primary fractionator will contain both organicand inorganic acids that will condense in the overhead exchangers. The aqueous pH of thecondensed water will be low, resulting in corrosion in the overhead condensing system.Corrosion is generally most severe at the dew point. The acidic species found in the overheadvapor are present in the water as it condenses, thus lowering the pH. This will result ingeneral corrosion attack, possibly with some localized pitting of the exchanger tubes and pipewalls.Preventing corrosion in the overhead system will be based on controlling the aqueous pHabove 5 at dew point conditions. An organic neutralizing amine is water-soluble and willtherefore be present in the water droplets at the initial dew point. The reaction will form saltsthat will be washed through the system in the condensed water. Improper neutralizer choiceand/or application can result in serious corrosion problems. An example showing the use of asimulation method using Ionic Equilibrium Modeling is discussed in this paper. The IonicEquilibrium Model is used to carry out a rigorous electrolyte simulation resulting in neutralizingamine selection and application guidelines.
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