Fast and Reliable TS Determination in Liquefied Pressurized Gases (LPG) according to ASTM D6667, ASTM D7551, and DIN EN 17178 Application Note · compEAct

Introduction

Gaseous compounds in the liquefied pressurized state are valuable source materials for chemical synthesis or polymerization, but are also increasingly utilized as energy carrier for heating, power generation and transportation purposes. The concentration of sulfur compounds is a key parameter for their quality and usability, for example as propellant gas or as starting material in polymer production (e.g., polyethylene). Because sulfur compounds may cause catalyst poisoning and undesirable byproducts, their content should be <100 ppb, to avoid increased production costs. For the use as combustible or fuel (LPG, CNG), different requirements and standards apply. Here emission limits for sulfur must not be exceeded and the odorants (e.g., mercaptan) added for safety reasons must be at the appropriate level. To guarantee optimum product quality and instant process optimization, the rapid detection of ultra-low and high sulfur contents is required in LPG analysis.

Analysis of an LPG is more challenging than any other sample matrix due to two big challenges. The first is the sample metering and dosing into the analyzer, the second the safe and complete combustion of this vigorously reacting matrix.

Due to widely varying pressures, safe and controlled handling and quantitative dosing of LPG into the combustion zone is challenging. Samples tend to evaporate too early, affecting analysis quality and operating safety due to deflagration, explosion, soot formation or incomplete combustion. When expanding the LPG to allow a more controlled handling, the samples undergo changes due to adsorption loss, condensation, etc., which clearly influences the analysis quality. Direct LPG analysis out of the liquefied phase followed by stepwise evaporation in controllable safe small volumes is one approach to overcome these challenges. Sulfinert™ coating of relevant system parts and the PermaPurge function help to avoid adsorption losses of reactive TS compounds.