Perfluoroelastomer stands up to gas sweetening processes

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  • Material features 10 to 15 times lower swell than FKM
  • Proven long-term seal life adds protection, reduces downtime

Today, oil refineries and gas plants around the world are processing crude oil and natural (sour) gas containing higher concentrations of hydrogen sulphide (H2S) than ever before. At the same time, global environmental standards demand progressive reduction of H2S content in gas and oil based end-products. As a result, the hot amine “sweetening” treatments used to remove H2S are becoming much more aggressive to the materials used to seal pumps, valves and other vital process equipment, to the extent that commonly used fluoroelastomer (FKM) and perfluoroelastomer (FFKM) seals are failing more frequently, risking toxic leakage and potentially costly downtime.

Material features 10 to 15 times lower swell than FKM

The company DuPont is addressing this issue with its new Kalrez Spectrum 6380 perfluoroelastomer. The material, used for sealing parts, provide very good resistance to amines and strong oxidizers at high temperatures in gas sweetening processes. 6380 parts exhibit 10 to 15 times lower swell than FKM, and four times lower swell than general purpose FFKM, in such environments. The DuPont FFKM has very good mechanical properties and can operate at a maximum application temperature of 225 °C, with short-term excursions to higher temperatures.

“Swelling caused by exposure to hot, toxic and aggressive chemicals is the biggest enemy of a sealing material. It can lead to extrusion and rupture of the seal, and eventual leakage of the process stream. The environment found in amine gas sweetening processes has become a particular challenge to sealing material suppliers and to valve, pump and mechanical seal manufacturers,” said Jean-Luc Matoux, global application engineer, Energy & Material Handling for DuPont Performance Polymers.

Case study: seven times longer seal lifetime

A major chemical company in France, processing a mix of amines, ethylene oxide and other chemicals at 150 °C, has reported seven times longer seal lifetime when switching to a Kalrez Spectrum 6380 O-ring from a competitive broad resistance FFKM grade O-ring. In this actual case history example, the conventional FFKM O-ring survived the hazardous and highly aggressive process conditions for only 15 days before requiring replacement, while the Kalrez Spectrum 6380 part survived for 3.5 months. Benefits of installing parts made from perfluoroelastomer are increased system efficiency, significantly extended Meantime Between Repairs (MTBR), greater reliability, and enhanced safety from reduced risk of potentially dangerous chemical leaks. Ultimately, this has led to valuable annual savings in reduced total system cost.

DuPont FFKM performance chart

Chart demonstrates the ability of DuPont Kalrez Spectrum and Kalrez 0090 perfluoroelastomer sealing parts to resist a highly aggressive mix of DiGlycolAmine/water at 140 °C, used typically in H2S removal/gas sweetening processes, by exhibiting 10 to 15 times lower swell than FKM and four times lower swell than general purpose FFKM after 336 hours exposure (source: DuPont)

Amine Gas Sweetening Processes

Most of the new sources of oil and gas discovered today contain high concentrations of H2S that demand more efficient removal technologies. However, the latest environmental standards require ever-decreasing H2S content in clean natural gas. Amine treatment units are used in oil refineries and gas plants around the world to remove H2S from natural gas (sour gas) in an operation commonly referred to as “gas sweetening.”

The challenge to sealing components

Amine treatment units can create harsh chemical environments. H2S, for example, is highly toxic, needs to be handled with care, and can cause embrittlement of metal equipment. In addition, these processes operate at high temperatures that require advanced elastomeric sealing components including FKM and FFKM. However, elastomers tend to swell to a high degree when in contact with amines, resulting in loss of mechanical properties and extrusion. This can lead to leakage, rupture of the fluid film in mechanical seals due to face seal deformation, and increase in the torque needed to operate a valve.

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