LPG is an alternative fuel, which is still fossil fuel-derived. It offers several benefits over traditional fuels as LPG is a clean-burning transport fuel with a high energy content and the infrastructure is well developed. The legislative rules and automotive industry promote the use of LPG.
Control over the residue content is essential in end-use applications of automotive LPG. These residues can lead to troublesome deposits that will accumulate and corrode or plug the LPG fuel filter, the low pressure regulators, the fuel mixer or the control solenoids. Commercial LPG, especially LPG destined for automotive applications, must meet certain fuel specifications. Test methods used to provide these assessments are described in ASTM Method D2158, ISO 13757, EN 15470, or EN 15471. These test methods require the evaporation of large amounts of LPG and therefore present a high safety risk.
New Method to Determine Residues in LPG
The industry now has an alternative for the determination of dissolved residues in LPG. This new technique is a fast, safe and accurate method based on Gas Chromatography combined with the Da Vinci Europe Liquefied Gas Injector (LGI). ASTM has approved the method:
ASTM D7756-12 ” Standard Test Method for Residues in Liquefied Petroleum (LP) Gases by Gas Chromatography with Liquid, On-Column injection”
The Method Appendices also provides guidance on the following analyses:
- Analysis of Benzene, Toluene, and Hydrocarbons C7 through C10
- Analysis of Diisopropanolamine (DIPA; CAS No. 110-97-4)*
*Application note available upon request
At the time of this writing it is also a CEN work item (PrEN 16423). The ASTM D2158 and ISO 13757 methods can be supplemented and eventually replaced by this GC method, which will provide the industry with a safer, more reliable and robust standard to determine LPG residue in less than half an hour.
The Da Vinci LGI injects LPG under pressure and at room temperature direct on column. With this injector no vaporizer, transfer line or valve is needed and therefore there is no adsorption, discrimination and fractionation. The unique capabilities of the LGI make it possible to analyze and quantify a complex matrix of heavy boiling components in low boiling matrices.
After injection, the GC analysis technique uses a vapor exit to flush the LPG light end fraction. The oily residue remains on the column and is separated by boiling point order. The result is reported as concentration in mg/kg (mass ppm). The analysis range starts from 10 up to 600 mg/kg having a repeatability of 5%. The required analysis time is less than 30 minutes.
After the product introduction in 2010 the LGI was awarded “Best New Technology” at the 2010 Gulf Coast Conference. The current installed base includes LPG customers located in Africa, Australia, Asia, Europe and U.S.A. Their experiences with the LGI have proven that the new technology is safe, fast and accurate. Additional benefits are: the results are not only reported as a value in mg/kg, the chromatogram also indicates the composition of the contamination and helps tracing the source of contamination.
Features of the Liquefied Gas Injector:
- Meets the specifications for ASTM D7756-11
- Alternative for ASTM D2158, EN 15470, EN 15471 & ISO 13757
- No open air evaporation of LPG
- High pressure injection directly onto GC column up to 30 bar
- Prevents discrimination and fractionation
- Unique and user friendly design
- Accurate quantification of heavy residues
- Fast analysis time of 24 minutes
- Lowest detection limit of 1 mg/kg (mass ppm)
- Repeatability of 5%
- Sample size from 30 – 500 µL
- Analysis range from 10 – 600 mg/kg (mass ppm)
- Fingerprint of contamination
Envantage, Inc. is the Exclusive North American Distributor of the Da Vinci Europe Liquefied Gas Injector (LGI) on the Agilent Platform
The Da Vinci LGI injector was featured in the Petro Industry News article “A Safe and Fast Solution for Accurate Quantification of Heavy Residues in LPG by Gas Chromatography: Representative Liquefied Gas Sample Introduction via High Pressure On-Column Injection into a Gas Chromatographic System”
Click here to download the PIN article
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