08 ENGINE ROOM WINTER EDITION These non-toxic silicon-bearing organic compounds are added to many domestic products like deodorants to improve their texture and feel; and as we use more of them they add to the chemical mix being added to our waste and drainage systems, and consequently our landfills. The problem for landfill gas-to-energy operators is when contaminants like siloxanes react with the engine lube oil causing varied combustion deposits. The main issue with siloxanes and other silicon-bearing compounds is that they are volatile and evaporate and migrate out with landfill and digester gases – either harmlessly in a flare, or harmfully inside internal combustion equipment. If untreated, biogas prior to induction, can contain varying levels of siloxanes which, during the combustion process, convert to silicates. These form part of the combustion deposits and are highly abrasive substances affecting the combustion chamber, cylinder head valve gear, exhaust systems and turbochargers. These deposits also contain strong acids that have a detrimental effect on the service life of the lubricating oil. Evidence of siloxanes in biogas is found in the form of a white powder in gas turbine hot section components, as a DECADESOF RELIABILITY light coating on various types of heat exchangers, in deposits on combustion surfaces in reciprocating engines, and as a light coating on post-combustion catalysts. The white powder is primarily silicon dioxide (SiO2), a product of siloxane combustion. Manufacturers of combustion turbines and reciprocating engines are expressing an increasing desire for siloxane control - despite almost two decades of successful experience without such controls. There is no doubt that some maintenance cost benefit can be realised by siloxane removal (and through the incidental removal of other biogas contaminants that will occur during siloxane removal); however, it does not currently appear that siloxane removal is cost effective in most cases. Supplying the best gensets to stand up to siloxanes Modern landfills are required to install gas collection systems to capture and destroy the methane gasses that are naturally produced within a landfill. These gases are burned in a flare. Rather than eliminating landfill gas by simply burning it off, Cat® is committed to the future of turning it into a renewable fuel by providing gas-fuelled engine-generators that can produce electric power from landfill gas. Two decades powering landfill gas-to-energy solutions The best of these landfill gas-to-energy gensets include the Cat® G3516LE and the state-of-the art CG132 and CG170 biogas gensets. In fact, the predecessor of the CG170 gas genset, the TBG 620 16-cylinder V-engine has proven its l eadership in the sector, continuously powering the Eastern Creek landfill site in Sydney’s west for almost 20 years. The range of Cat® CG biogas gensets include: 500kW – 1200kW, CG132 V12 600kW, CG132 V16 800kW and CG170 V12 1200kW. MWM TBG620 V16 engines rated at 1260kW operated by EDL at Eastern Creek landfill site in NSW also have a long history of reliability on untreated gas and have in excess of 50,000 hrs without major component change. The site was originally commissioned with four MWM TBG 620 16V units (with a fifth genset installed on a nearby site). EPSA assumed distribution of all the Cat® Mannheim-sourced gas products in Australia in September 2013. As part of this agreement, EPSA took on the parts and service support role for existing MWM product, including this site with full in-field support. World’s best research and design in action The research and development invested in by Cat® and Mannheim affords EPSA access to the world’s best practice in responding to any potential siloxane threats that can damage equipment. The TBG 620V16, now replaced with the Cat® CG170-12, boasts low operating costs; and is energy efficient due to its maximum primary energy utilisation. The long service intervals and outstanding energy conversion efficiencies ensure additional cost savings. Their intercooling feature permits New contaminants like siloxanes and other man-made compounds are an increasing problem in landfill sites but there is a smart solution writes Noel Rosario, EPSA Segment Manager - Diesel and Gas Investor Products. POWERING LANDFILL GAS-TO-ENERGY AND STANDING UP TO SILOXANE