Today, oil refineries and gas plants around the world are processing crude oil and natural (sour) gas containing higher concentrations of hydrogen sulfide (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.
An exception is provided by DuPont™ Kalrez® Spectrum™ 6380 perfluoroelastomer sealing parts that have proven to offer outstanding resistance to amines and strong oxidisers 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.
“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 – Kalrez® & Vespel®, for DuPont Performance Polymers.
“Kalrez® perfluoroelastomer parts formulations have evolved over many years to the point where, today, Kalrez® Spectrum™ 6380 can be considered a new benchmark in swell resistant elastomeric sealing materials,” Matoux said. “By exhibiting as little as 5% swell after long-term exposure to highly toxic hydrogen sulfide and water/amine mixture, it represents the optimum in FFKM sealing performance.”
Performance in use
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.
According to the company, the benefits of installing Kalrez® Spectrum™ 6380 parts have been seen in 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.
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.
Solving the sealing challenge
DuPont™ Kalrez® Spectrum™ 6380 perfluoroelastomer parts have been specifically developed for static and dynamic sealing applications in chemical processes involving hot, aggressive amines and strong oxidizers, exhibiting 10 to 15 times lower swell than FKM and four times lower swell than general purpose FFKM. The DuPont FFKM has excellent mechanical properties and can operate at a maximum application temperature of 225°C, with short term excursions to higher temperatures.
The use of DuPont™ Kalrez® Spectrum™ 6380 parts in amine gas sweetening applications can extend the MTBR of valves and mechanical pump seals, reduce leakage and help contribute to reduced maintenance costs and lower emissions. The latest Kalrez® 0090 parts represent another option for this application when high pressure resistance is needed. In rigorous third party laboratory testing for rapid gas decompression (RGD) resistance, Kalrez® AS568-312 O-rings received the best possible rating of 0000 per the NORSOK M-710 Rev 2 standard.
DuPont Performance Polymers is committed to working with customers throughout the world to develop new products, components and systems that help reduce dependence on fossil fuels and protect people and the environment. With more than 40 manufacturing, development and research centres throughout the world, DuPont Performance Polymers uses the industry’s broadest portfolio of plastics, elastomers, renewably sourced polymers, filaments and high performance parts and shapes to deliver cost effective solutions to customers in aerospace, automotive, consumer, electrical, electronic, industrial, sporting goods and other diversified industries.
Adapted from press release by Rosalie Starling
Read the article online at: https://www.hydrocarbonengineering.com/product-news/15122015/new-dupont-technology-stands-up-to-gas-sweetening-processes-1981/