ASTM to Develop Standards for Tunable Diode Laser Spectroscopy, Determination of Siloxanes in Methane, Natural Gas
November 3, 2009 // Published as a news service by IHS
ASTM International Committee D03 on Gaseous Fuels is developing ASTM WK24874 and ASTM WK24875 to address moisture vapor concentration and siloxanes in biogas.
Tunable Diode Laser Spectroscopy
ASTM WK24874 - Test Method for the Determination of Moisture Vapor Concentration in Natural Gas and by Tunable Diode Laser Spectroscopy (TDLAS) is being developed at the request of several gas companies that use TDLAS analyzers for the measurement of moisture in natural gas.
While TDLAS has become a popular type of gas analysis, no specific standard exists for its use, experts said.
The new standard is under the jurisdiction of Subcommittee D03.12 on On-Line/At-Line Analysis of Gaseous Fuels.
According to D03 member Samuel Miller, the proposed standard will primarily be used for measuring moisture in methane or natural gas, with consideration for the following specific applications:
- Raw natural gas found in production and gathering sites.
- Dehydration plant inlet and outlet.
- Transportation pipelines.
- Underground gas storage facilities.
- Natural gas distribution (utilities).
- Natural gas power plant inlets.
- Natural gas processing, such as natural gas liquids (NGLs) separation, sweetening and gas liquification plants.
Siloxanes
ASTM WK24875 - Practice for On-Line Determination of Siloxanes in Biogas and Other Gaseous Fuels by FTIR (Fourier Transform Infrared) is being developed by Subcommittee D03.05 on Determination of Special Constituents of Gaseous Fuels.
The standard fills a need for a way to measure siloxanes in biofuel mixtures.
While biofuel from landfills and sewage digestion has been used as fuel for local gas turbine engines, it is necessary to hold the content of siloxanes within the fuel down to 50 parts per billion (ppb).
Siloxanes that can coat the turbine under working conditions are converted to an abrasive silicone dioxide coating that greatly reduces the lifetime of the engine, according to ASTM.
Barbara Marshik, D03 member, said ASTM WK24875 will allow for the field analysis of siloxanes in real time at the ppb level required for the purified process gas stream.
"This technique does not require daily calibrations in order to obtain the correct concentration values found within the gas stream," Marshik said. "Once the initial calibrations are created, only verification testing is required after that point and those are not done on a daily basis, all of which greatly reduces the analysis time."
Marshik said once it has been approved, ASTM WK24875 will be used by landfill gas and sewage digester personnel responsible for measuring biogas composition in its crude form, as well as by those responsible for analyzing the composition both during and after the purification/removal of siloxanes to form the final biofuel product.
Source: ASTM International.