Use online analyzers for successful monitoring
01.01.2011
| Benton, A. , Michell Instruments Ltd., Ely, Cambridgeshire, United Kingdom; Valiz, C. , PDVSA, Jose Complex, Venezuela
Improved analytics measure moisture and dew points for natural gas components
Keywords:
[natural gas]
[analyzers]
[dew point]
[turboexpander]
Using advanced online water and hydrocarbon dew-point analysis techniques is critical to the efficient and reliable operation of natural gas liquid-extraction processes, producing valuable light alkane liquids while the remaining gas is suitable for sales distribution. At its San Joaquin facility, Petróleos de Venezuela, S.A. (PDVSA) initially processed raw wellhead natural gas by separating residual hydrocarbon (HC) condensates, followed by glycol dehydration to reduce the water dew point. Reduced temperature separation was used to decrease the HC dew point prior to molecular sieve dehydration. This provided feed gas with moisture controlled to trace levels into the primary liquid-extraction process. Maintaining moisture concentrations to less than 0.1 parts per million (ppm) by volume is essential for reliably operating turbo expanders. The turboexpanders function is to use the depressurization of natural gas to achieve deep cooling of the process flow to 80°C. Avoiding ice formation within the separation processparticularly the turboexpanderis critically important for continuous plant operations and to prevent astronomical maintenance costs. Online measurement of dew point temperature within the feed gas, containing water precipitate and hydrocarbon condensate, enabled PDVSA process operators to extend the lifetime of the desiccant beds while protecting the turboexpanders from risk of damage.
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