4 February / March 2016
The Benefits of Thermal Desorption Coupled with Gas Chromatography for the Analysis of Hydrocarbon Residues in Liquefied Petroleum Gas
by Lee Marotta, PerkinElmer, Inc, Shelton, CT, email:
Lee.Marotta@
perkinelmer.com Dan Wispinski, Dave Murray, Tom Kosik, Chris Goss and Jodi Johnston, Alberta Innovates Technology Futures, Edmonton, Alberta, Canada.
Liquefied Petroleum Gas (LPG) is a hydrocarbon fuel produced from the refining of natural gas or the fractional distillation of crude oil. It is primarily a mixture of propane and butane that is used for a wide variety of field and industrial applications, including a fuel for motorised transport systems, a propellant for aerosols and as a gas for refrigeration purposes. Once produced, LPG is transferred to pipelines, ocean tankers or terminal delivery systems for long-distance distribution. Once at a distribution centre, LPG is typically transferred to a bulk truck or rail car for short-haul transport to a retail plant. From there, it is distributed in cylinders or bulk trucks for delivery to the retail customer. Figure 1 represents a simplified schematic of the LPG distribution Chain [1].
The transportation and delivery of LPG can lead to potential sources of contamination, which can be harmful to engines, motorised systems or industrial processes. For example, if gasoline or diesel fuel has been used in the transportation tankers, it can result in contamination of those components in the LPG. When compressors are used to pump the LPG into pressurised tanks, the oil can contaminate the LPG. And finally, phthalates
and similar plasticisers can end up in the LPG from the delivery hoses used to fill pressurised cylinders.
ASTM International (ASTM) D1835 ‘Standard Specification for Liquefied Petroleum (LP) Gases’ [2] designates ASTM Method D2158 ‘Standard Test Method for Residues in Liquefied Petroleum (LP) Gases’ [3], as the referee method for residue measurement. However, residue contaminants in LPG using
this evaporation/gravimetric procedure does not achieve the detection limits required by industry. Besides being time consuming and labour intensive, the sensitivity of the method is not sufficient for many of the more challenging applications of LPG including fuel cells and micro turbines, which require keeping the contaminants below 20 ppm (µg/g) for the process to work efficiently. In addition, Method D2158 can
Figure 1: Simplified schematic of the LPG distribution Chain [1]
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