Pipelines collect and transfer sales gas from upstream facilities to downstream customers (e.g., the LNG plants). Conventionally, pressurized gas is dehydrated with triethylene glycol (TEG) at upstream processing facilities. The sales gas pipelines are generally designed for dry gas operation. However, TEG losses in the form of vaporization and mechanical carryover lead to gradual liquid TEG accumulation within the pipeline. A small amount of water is also dropped out of the gas phase. TEG accumulation in the pipeline system has been demonstrated, and the quantities determined, to provide inputs for a pigging philosophy, liquid management and corrosion assessment. The key issues in the developed model and simulation are the overall operating condition and the thermodynamic package. Both the SRK and Glycol thermodynamic packages are validated equations of state for TEG-water-methane phase equilibrium. The liquid TEG profile within the pipeline system has been determined, and it shows that TEG accumulation rate and film thickness both decrease through the pipeline system, so that the majority of condensation occurs in the first quarter of the pipeline length. The simulation study shows that upsets in the TEG process lead to TEG film dilution due to water absorption from wet gas and off-spec gas. An excessive water fraction in the TEG film may cause a high rate of corrosion. However, on-spec gas strips the TEG film and removes water from the liquid phase as the TEG process is brought back to normal gas supply. A simulation was performed to examine the reversible cycle of upset and normal operation. It estimated the maximum encountered water fraction in the TEG film as well as the duration of TEG film dilution and stripping. The process simulation provided inputs for a corrosion management study. Corrosion rate calculations show that the upset in a TEG unit potentially brings about a considerable corrosion rate during the upset, but a negligible corrosion rate for lifetime service in the sales gas pipeline. However, adequate corrosion monitoring is recommended for any unknown corrosion issues. The study confirmed that the TEG film on the pipeline wall mitigates the impact of the short-time wet gas injection to the pipeline and its prominent role in corrosion rate determination.


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    Titel :

    Manage TEG liquid and corrosion in sales gas pipelines


    Beteiligte:
    Kordabadi, H. (Autor:in) / Dinon, M. (Autor:in)

    Erschienen in:

    Hydrocarbon Processing ; 92 , 10, Supplement Gas Processing ; 29-34


    Erscheinungsdatum :

    2013


    Format / Umfang :

    6 Seiten, 8 Bilder, 5 Tabellen, 7 Quellen



    Medientyp :

    Aufsatz (Zeitschrift)


    Format :

    Print


    Sprache :

    Englisch




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