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Posted by Bob D. on February 25, 2006 at 11:15:12:
In Reply to: Firing methane (landfill) gas in firetube boiler problems posted by KLK on February 24, 2006 at 15:07:34:
What pre-processing of the landfill gas is the User doing? Included in the "stew" described below, there is no small amount of hydrogen sulfide in raw LF gas.
From EPA (and the "Environmental Justice" website, hey the lunatic fringe isn't always completely wrong) - Landfill gas is roughly 50% methane. The remainder of landfill gas is mostly carbon dioxide with varying amounts of nitrogen, oxygen and assorted contaminants known as "non-methane organic compounds" or NMOCs. NMOCs usually make up less than 1% of landfill gas. EPA identifies 94 NMOCs in their 1991 report, "Air Emissions from Municipal Solid Waste Landfills - Background Information for Proposed Standards and Guidelines." Many of these are toxic chemicals like benzene, toluene, chloroform, vinyl chloride, carbon tetrachloride, and 1,1,1 trichloroethane. At least 41 of these are halogenated compounds. Many others are non-halogenated toxic chemicals.
Even though it's a relatively small amount, with larger burners over the course of a year you could end up with a lot of weird stuff deposited on the fire-sides. There's probably all kinds of "side" reactions going on, some of which are bound to be aggressive towards refractory and ferrous tubes and sheets. Without a pretty top-notch scrubbing and processing protocol, I'd figure on an accellerated rotating schedule of inspections, cleaning, and repairs for the fire-sides. I would think that the cost-benefit analysis for justifying advanced gas pre-processing would be pretty complicated. There's a lot of people way smarter than me on this site, so I'm curious to see if there is a majic bullet.