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Get Your Questions Answered

What is SAG^TM technology?
Where is SAG^TM Technology Applied?
How does SAG^TM technology compare to other types of gas purification technology?
What is required to determine the size and cost of a SAG^TM technology process?
What are Siloxanes?
What are some problems caused by Siloxanes?

Q: What is SAG^TM  technology?
A: SAG^TM technology refers to a patented proprietary adsorbent process that is custom-engineered for a specific application. SAG^TM was developed for fuel gases and mixtures of inert gases and fuel gases that contain more than one contaminant that must to be removed to critically Iow levels. In a typical vapor phase adsorption system, a single media, such as an activated carbon or resin, is employed to remove a mixture of VOC's (volatile organic compounds) from air or gas. These volatile organic compounds compete with each other for adsorption space in the activated carbon pores. The more strongly adsorbed species prevent adsorption or even displace the weakly adsorbed species. The result of this competition is reduced overall capacity and shortened bed life before breakthrough. Often, competitive adsorption renders the use of activated carbon or resins economically infeasible due to the cost of media replacement.

SAG^TM technology employs multiple proprietary media (over 150 types) that significantly reduce or eliminate the competition between compounds of different adsorption potential. This enables them to be picked up by the media at a higher capacity, with longer bed life and a longer time interval to breakthrough. In critical applications, SAG^TM technology not only performs better than standard activated carbons and resins, but also makes possible the removal of difficult mixtures of organics previously not able to be removed.

Q: Where is SAG^TM Technology Applied?A: SAG^TM technology was developed specifically to purify anaerobic digester and landfill methane gas. This gas is for use in low BTU gas-burning internal combustion engines that drive electricity generators. Digester and landfill gases contain approximately 50% methane and 50% carbon dioxide with some other gases such as nitrogen, argon, and oxygen. Nearly all digester and landfill gas contain one or more species of siloxanes, a chemical used extensively in industrial products such as lubricants and in personal care products like cosmetics, hair spray and deodorants. These siloxanes make their way into municipal wastewater and ultimately into the methane liberated in municipal digesters. Discarded cosmetics and cosmetic containers introduce siloxanes into the solid refuse that decomposes in landfills, producing methane that is contaminated.

The combustion of methane containing siloxanes causes damage that can be quite severe in generator engines (see below). Deposits of solid silica (silicon dioxide) on the engine internals increases maintenance requirements by a factor of 5 or 10 times. Normally designed to run 20,000 to 40,000 hours between teardowns, some engines are requiring re-builds in as short as 14,000 hours, and in severe cases, after only 2,000 to 4,000 hours.

While some engine manufacturers are specifying that the siloxane level in fuel gases fed to their engines should be below 200 ppb (parts per billion), moderate damage has also been experienced at concentrations as low as 50 ppb. SAG^TM technology reduces the siloxane level in fuels gases to below 20 ppb.

Q: How does SAG^TM technology compare to other types of gas purification technology?A: Compared to other adsorption-type technologies, SAG^TM technology is more than three times as effective in removing siloxanes as activated carbon and five times as effective as synthetic resins. The media used in the SAG^TM process is also regenerable, which means it can re re-used. This increases the economy of operating a SAG^TM system. Activated carbons are only partially regenerable and resins are not regenerable at all. This means higher costs. In the same equipment footprint, there is no more powerful or economical siloxane removal technology than the SAG^TM process.

Q: What is required to determine the size and cost of a SAG^TM technology process?
A: With a complete gas analysis, the scientists at Applied Filter Technology can size a SAG^TM system and estimate the operating life of the media. Since this is only a paper study, pilot testing is recommended to confirm treatment kinetics and other operating parameters. Analysis of dozens of gas sources already tested indicates that there is a finite range for the operating parameters. If the ultimate client is satisfied with the estimates, a system can be built and installed. If the gas will require a purity warranty, pilot testing is required.

Q: What are Siloxanes?
A: Siloxanes are encountered in Digester and Landfill gases:

• MM (Hexamethyl Disiloxane)
• D₃ (Hexamethylcyclotrisiloxane)
• D₄ (Octamethylcyclotetrasiloxane)
• D₅ (Decamethylcyclopentasiloxane)
• D₆ (Dodecamethylcyclohexasiloxane)
• Polydimethylsiloxanes - [Me₂SiO]_x - (MM, MDM, MD2M) are not usually volatile.
• Cyclomethicones - [Me₂SiO]_x - (D₃, D₄, D₅, D₆) are volatile, but not regulated as VOC or ODC.

Physical Properties

Q: What are some problems caused by Siloxanes?
A: Here are some pictures of the siloxanes clogging a boiler due to burning siloxane rich gas:

Below are damaged cylinder heads from a large generator.  This is significant damage that requires a complete overhaul and weeks of downtime.