Gas Detection 23


Landfill Gas H2S Increase Measured with High-range Analysers


Hydrogen sulphide levels (H2S) in landfill gas have increased and Geotech (UK) has responded to changes reported by landfill site operators by now offering analysers measuring H2S up to 10,000 ppm. Rapidly rising H2S levels are thought to be caused by waste-to-landfill content changing largely as a result of success in recycling and other initiatives to avoid sending waste to landfill. Previously, H2S was measured at 0-500ppm – still typical for post-scrubber H2S measurement – but higher level monitoring is now essential on many UK landfill sites.


Currently the two main methods of landfill gas measurement are either with portable or fixed-position gas analysers. Geotech reports strong interest in high- range H2S analysis at 0-10,000 ppm which is an option on its newly launched portable landfill analyser, the GA5000 . This option is also available on the Geotech fixed-position, automated landfill and biogas gas analysers, the GA3000 and the Geotech AEMS system.


As well as presenting a significant health risk to operators, H2S can also ‘poison’ the electrochemical cells which provide the most cost-effective solution for H2S monitoring. Higher H2S levels present a greater challenge. The cells must be regularly purged with clean air. Geotech’s portable analysers are easily purged manually after taking each reading and Geotech fixed position gas analysers purge automatically. Without


purging, the life of the H2S cell is dramatically reduced and accuracy compromised. Some analyser systems dilute biogas with air in order to monitor H2S continuously but there is a significant danger of adding error with this approach and it may well not be enough to cope with new, high H2S levels.


For the many landfill operators using landfill gas to produce electricity from CHP engines, accurate H2S measurement is essential. To protect CHP engines, inbuilt gas content and quality sensors may cause auto-shut down to protect engines from corrosive H2S damage and CHP engine manufacturers usually specify an upper H2S limit above which warranties can be invalidated. Consequently, landfill operators often prefer to analyse the gas used in CHPs. If the gas is not suitable for CHP use and without an H2S scrubber, likely to cause damage with excessive H2S, they may divert it to flare or use it elsewhere.


High levels of H2S are often reduced with scrubbing systems and gas analysers can measure levels before and after scrubbing. This monitors scrubber performance as well as avoiding high levels of corrosive H2S reaching and damaging CHPs.


Geotech advises that all landfill gas analysers must be used and managed properly, including appropriate purging, to give operators the reliable gas readings essential for gas field management. As H2S levels rise, so does the need for accurate, dependable landfill gas analysis. Geotech works closely with landfill


operators and other stakeholders to ensure equipment is in-line with changing conditions as well as being reliable and well-supported.


Reader Reply Card No. 78


New Sampling Pump Module Simplifies Gas Monitoring in Remote Areas


The new SM100 Sampling Pump Module from General Monitors (USA) draws combustible or toxic gases at 0.05 to 1 LPM from monitored areas to a gas detector, making it easier and cost effective to measure potentially hazardous gases in areas that are too remote, inaccessible, or too cold, hot, or wet for direct sensor monitoring.


The user-friendly SM100 Sampling Pump Module supplies gas for up to three gas detectors, which is useful formonitoring multiple gases in a single line. The SM100 features a low flow indicator, which informs the end user if flow is insufficient for gas detection. It also includes a trouble relay that provides a local signal indication of the low flow condition.


The SM100 Sampling Pump Module reduces plant operating costs by simplifying operation and maintenance. Its rugged design and 316-stainless steel construction make it suitable for gas detection service in a variety of harsh industrial environments. Areas particularly suited for monitoring with the SM100 include ducts carrying combustible or toxic gas, wet wells, sewage dryers, printing drying ovens, and storage tanks.


The SM100 is available in two configurations, an aspirated model that is used with a compressed air source and a DC pump module. The aspirated model is designed for use with instrument grade aspirator air, up to a max aspirator pressure of 30 psig (206 kPa).


Reader Reply Card No. 80


Mass Flow Meters and Controllers


Designed for OEM


Axetris AG Switzerland Phone: +41 41 662 76 76 E-mail:


www.axetris.com Mass Flow Modules |


axetris@axetris.com


High turn-down ratio High repeatability Low flow ranges Platinum based MEMS


Laser Gas Detectors | IR Sources


Reader Reply Card No.


79


IT’S WHAT’S INSIDE THAT COUNTS


MSA’s ALTAIR 4X and ALTAIR 5X are equipped with XCell sensor technology to provide increased performance, fast response time & reduced cost of ownership.


PERFORMANCE BEYOND WHAT YOU SEE When contacting


companies directly from this issue of International


Environmental Technology


please tell them where you saw their product.


Thank you MSA EUROPE  Phone: +49 (0)30 6886-0 


MSA XCell Sensors have a typical life of more than double the industry average, and are engineered using MSA’s pro prietary application- specific integrated circuit (ASIC) design.


By miniaturizing the sensors’ controlling electronics and placing them inside the sensor itself, MSA XCell Sensors offer superior stability under extreme environmental conditions, accuracy and repeatability.


In addition to MSA XCell Sensors, the ALTAIR 5X Multigas Detector can also be equipped with our wide variety of IR sensors covering many gases and ranges including CO2.


+ DRIVEN BY


INNOVATIVE SAFETY FEATURES: MotionAlert, InstantAlert alarm & end-of-sensor life indicator


E-mail: contact@msa-europe.com www.MSAsafety.com 


Reader Reply Card No.


81 www.envirotech-online.com IET May / June 2012


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