Fast Refinery Gas Analysis Using the Agilent 490 Micro GC QUAD

Transcription

1 Fast Refinery Gas Analysis Using the Agilent 0 Micro GC QUAD Application Note Energy & Fuels Authors Coen Duvekot Agilent Technologies, Inc. Introduction There is a large variation in the composition and source of refinery gases. Therefore, the precise and accurate analysis of these gases is a significant challenge in today s refineries. Typical sources include fluid coking overheads, ethylene, propylene, fuel gas, stack gas, off gas, etc. The physical stream ranges from gas to highly pressurized gas or liquid. Very fast refinery gas analysis (RGA) is possible with the portable Agilent 0 Micro GC QUAD. This note describes the use of the 0 Micro GC for RGA, with results obtained in about two minutes.

2 Instrumentation 0 Micro GC QUAD Channel : Agilent J&W CP- Molsieve with back flush Channel : Agilent J&W PoraPLOT U with back flush Channel : Aluminum oxide with back flush Channel : Agilent J&W CP-Sil CB The CP-Molsieve channel and the aluminum oxide channel are equipped with extra in line filters between the manifold and the column module to ensure moisture- and carbon-dioxidefree carrier gas. This enhances column lifetime and, most importantly, leads to stable retention times. GC control and data handling software: Agilent chromatography software. Materials and Reagents Channel, equipped with a CP-Molsieve column, separates and analyzes the permanent gases except for carbon dioxide. Channel, with a PoraPLOT U column, separates and analyzes the C gases and hydrogen sulfide. The C and C hydrocarbons are analyzed on the third channel with an Al O column. Finally, the higher hydrocarbons are analyzed on the fourth channel, with a CP-Sil CB column. Table. Peak identification and composition of gas standards Gas Standard Peak # Component Amt (%) Hydrogen Oxygen Nitrogen Methane Carbon monoxide Bal Refinery Gas standard Peak # Component Amt (%) Peak # Component Amt (%) 7 Conditions Results and Discussion Figures and show chromatograms of the CP-Molsieve channel. Helium Nitrogen Methane Carbon monoxide Carbon dioxide Ethylene Ethane Acetylene Hydrogen sulfide Propane Propylene iso-butane Table. Chromatographic conditions Bal Propadiene n-butane tr--butylene cis--butylene n-pentane, -Butadiene n-hexane 0 s s Figure. Refinery gas on the CP-Molsieve column, channel Channel Channel Channel Channel m CP-Molsieve m PoraPLOT U m AlO/KCL m CP-Sil CB Injector Temp ( C) Column Temp ( C) Carrier Gas Argon Helium Helium Helium Column Head Pressure (kpa) Injection Time (ms) 0 0 Back Flush Time (s) 7. N/A s Figure. Standard gas on the CP-Molsieve column, channel Hydrogen or helium, oxygen, nitrogen methane and carbon monoxide were separated and analyzed. Later eluting components were back flushed to vent.

3 7 Figure. Refinery gas on the Agilent PoraPLOT U column, channel On the PoraPLOT U channel (channel ), the C hydrocarbons, hydrogen sulfide and carbon dioxide were separated and analyzed. The channel was equipped with a back flush, later eluting components to vent. 0 s 0 0 On channel the C and C saturated and unsaturated hydrocarbons were separated and analyzed. This channel was also equipped with back flush in order to prevent the later eluting hydrocarbons from entering the analytical column. This prevented the later eluting components from interfering with the next analysis causing ghost peaks and/or baseline drift and higher noise. Furthermore, this channel was equipped with extra filters in the carrier gas lines, effectively protecting the analytical column from traces of moisture and carbon dioxide that could influence the chromatographic properties of the stationary phase in the long term. Stable retention times are key factors for good chromatographic results. Repeatability results derived from Table and Figure for retention times are superb with RSDs around 0.% and no drift s Figure. Refinery gas on the aluminum oxide column, channel 0

4 . tr--butylene cis--butylene,-butadiene Run # Figure. Repeatability figures for the aluminum oxide channel, channel Table. Repeatability figures for the aluminum oxide channel Run # tr--butylene cis--butylene, -Butadiene Average Std Dev Rsd % % %

5 Table. Reproducibility figures Day tr--butylene cis--butylene, -Butadiene Average St. dev. RSD % % % % % % Table and Figure show the effects over several days. RSDs are only slightly higher when compared to the resultsper-day, which is to be expected. However, the results are very good, demonstrating the suitability of the Al O channel for this type of analysis. RSDs below 0.% are shown in Table. During the ten day laboratory experiments no drift in retention times were observed, as can be seen in Figure. Figure shows no drift in retention time of components analyzed on the Al O channel over ten days. Figure 7 shows a chromatogram of refinery gas on the CP-Sil CB channel. In this case the higher hydrocarbons C+ were analyzed..0. tr--butylene cis--butylene,-butadiene 0 Analysis Day Figure. Reproducibility of the aluminum oxide channel, channel

6 s Figure 7. Refinery gas on the Agilent CP-Sil CB column, channel Conclusion The Agilent 0 Micro GC QUAD was successfully used for the analysis of refinery gas. The permanent gases helium, hydrogen, oxygen, nitrogen, methane and carbon monoxide were analyzed on the CP-Molsieve channel. The C hydrocarbons, carbon dioxide and hydrogen sulfide were analyzed on the second channel equipped with a PoraPLOT U column. On the third channel, with an aluminum oxide column, the C and C hydrocarbons were analyzed. This channel was equipped with extra in line filters to ensure moisture and carbon-dioxidefree carrier gas. This significantly enhanced column lifetime and ensured long-term stable retention times. Finally, the fourth channel, equipped with a CP-Sil CB column, analyzed the C+ hydrocarbons. This information is subject to change without notice. Agilent Technologies, Inc. 0 Published in USA, September, 0 SI-0