Measurement of the Hydrocarbon Dew Point of Real and Synthetic Natural Gas Mixtures by Direct and Indirect Methods

Abstract

A detailed comparison of the performance of direct and indirect methods for measuring the hydrocarbon dew point (i.e., the temperature at which the condensation of hydrocarbons in a gas mixture first occurs) of a range of real natural gases and synthetic natural gas mixtures is presented. Good agreement is found between the results of the different methods, although a difference is observed between those from the synthetic gas mixtures and the real natural gases, where the relative order of the dew points determined by direct and indirect instruments is reversed. The relationship between measured hydrocarbon dew point and the condensation rate of the gases is investigated. Using an automatic chilled mirror instrument to measure the dew point of gases with low condensation rates can result in a discrepancy of up to 2 K when compared to the measurement of fast-condensing gases. The limitations of the indirect gas chromatography methods, particularly the difficulties in measuring hydrocarbon species containing 10 or more carbon atoms, have been modeled and can also result in a discrepancy of up to 2 K when compared to the measurement of gases containing no such C10+ species. The magnitude of these discrepancies is close to the uncertainty of the method.

Multi-component adsorptive separation: use of lumping in PSA process simulation

“…Present work considers the NG treatment system which may have actually 30 components (Brown et al 2009). ≥7 ≥249 Not found, however patent example gives a process design considering 19 components (Holcombe et al 1990).…”

“…Lumping philosophy is also used successfully for capturing the essence of complicated mass transfer processes (Sircar and Hufton 2002). Experimental difficulties compel the analyst to report compositions of natural gas mixtures in terms of pseudo-components formed by lumping two or more number of components (Brown et al 2009). For adsorptive separation processes, both pure component and mixture adsorption data are very scarce.…”

Measurement and Prediction of Hydrocarbon Dew Points of Synthetic Natural Gas Mixtures

“…However, this situation would not occur when the operating temperature is higher than the HDP of rich gas for a given pressure condition. The HDP analysis and prediction of natural gas have been discussed in the literature for several decades, − and the common methods used to determine HDP are direct measurement using a chilled mirror procedure and indirect measurement using compositional analysis from a gas chromatograph (GC) combined with the equation of state (EOS). Avila et al and Jarne et al measured the dew point curves of synthetic natural gas and correlated the experimental data with model calculations.…”

“…In this work, by using a high-pressure sapphire cell apparatus which can provide low temperature and visualization conditions, we tested the HDP of eight synthetic natural gas samples with the pressure search method. It was reported that the influence of the hydrocarbon component on the HDP is more sensitive as the number of carbons increases. , However, there was few reports to quantify it in the literature; therefore, this study investigated the influence of a small trace change of n -C 5 or n -C 6 on the cricondentherm and cricondenbar. In addition, the adaptability of the PR and SRK EOSs in predicting dew points was examined.…”

Prediction of Dew Point Pressure in Gas Condensate Reservoirs Based On a Combination of Gene Expression Programming (GEP) and Multiple Regression Analysis

“…Typical phase diagram of gas condensate is shown in Figure 1. By reducing pressure isothermally starting from point "1", condensation begins at point "2" (dewpoint pressure) [4,10,11] and reach a maximum at point "3" then begins to decrease [12]. Point "G" represents separator condition that lies in the two-phase region, in which well stream separated into separator gas and separator oil [13].…”