Determination of major hydrocarbons in natural gas using near infrared spectroscopy and chemometrics

Author(s)

Camila Manara Franco

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2008-03-10

Examining board members

Jarbas José Rodrigues Rohwedder; Roberto Kawakami Harrop Galvão; Edvaldo Sabadini

• Advisor: Jarbas José Rodrigues Rohwedder

Abstract

Near Infrared (NIR) Spectroscopy and Chemometrics were used to construct calibration models to determine the concentration of major hydrocarbons in gas mixtures in concentrations similar to those observed in natural gas. The spectra were obtained by two different NIR spectrophotometers made in the laboratory, one employing a cell of fixed and other with variable optical path. Different sample sets were prepared in order to mimic the variability of methane, ethane, propane and butane concentration found in natural gas obtained from various sources. The analysis of certified samples made by using the calibration models showed Root-Mean-Square Errors of Prediction (RMSEP) equal to 1.07, 0.21, 0.22 and 0.14% (v/v) for methane, ethane, propane and butane determination, respectively. The prediction of methane gas content showed better repeatability compared to the standard technique based on gas chromatography. To investigate the possibility of constructing an NIR spectrometer dedicated to the analysis of natural gas, the selection of variables was evaluated. The results indicated that, by using up to 13% of the initial variables, the prediction of hydrocarbon gases is achieved with the same quality when compared to the results obtained using the full spectral range. Employing the selected wavelengths, it is possible to predict the concentration of methane, ethane, propane and butane with values of RMSEP equal to 1.32, 0.41, 0.22 and 0.14% (v / v), respectively. (AU)

• FAPESP's process: 05/03150-7 - Study of spectroscopic parameters for construction of a NIR photometer dedicated to determining major hydrocarbons in natural gas
• Grantee: Camila Manara Franco
• Support Opportunities: Scholarships in Brazil - Master