Steve Blankinship, Associate Editor
You probably never knew it, but shaving your face, shampooing your hair or using deodorant is undermining the growing trend toward converting municipally generated biogas into electricity.
That’s because many consumer and industrial products including deodorants, shampoos, shaving creams and sealants use silicon as dispersion agents. By way of industrial and residential discharges, silicones are introduced into sewage and landfills. When the methane produced from sewage sludge and landfills is recovered from wastewater and landfills, siloxanes are present. As the gas is used, Siloxanes break down into a white abrasive powder that damages equipment installed downstream, including boilers, combustion engines, turbines, and catalysts used to produce electricity from the municipally produced methane.
Wartburg, Tenn.-based Pioneer Air Systems, Inc. has a solution that not only removes siloxanes, but also eliminates moisture and reduces hydrogen sulfide (H2S), sulfur dioxide (SO2), halogens and other contaminants contained in biogases.
“Our concept utilizes what we term alternating evaporator technology for chilling compressed air and gases to temperatures below freezing,” says Sam Basseen, Pioneer’s president & CEO. “The first evaporator chills the gas while the second evaporator is de-frosted, and vice-versa, to provide continuous and uninterrupted air and gas flow.”
Although specialty carbons are effective in separating most contaminants, carbon, regeneration and disposal costs are high. Pioneer’s approach involves chilling gas to approximately
-20 F and using carbon adsorption to remove the remaining traces of contaminants. Chilling gas condenses moisture and most other contaminants. In addition, most of the remaining contaminants dissolve in the condensed moisture, which is separated and drained at various chilling and separation points. The specialty carbon adsorbs the remaining traces of contaminants to provide a virtually contaminant-free, energy-rich gas.
The standard total contaminant removal system includes a gas-to-gas heat exchanger that cools gas to approximately 40 F with the chilled gas at -20 F; cold coalescer; reheater; carbon absorber; control panels; fan motors; and hermetic compressor. Options include after-cooling, a duplex coalescer, and an after-filter with block and bypass valves.
Pioneer’s total containment removal system for landfill gas (LFG), digester and biogases removes 99 percent of siloxanes, H2S, SO2, moisture, halogens and other contaminants. Photo courtesy of Pioneer Air Systems, Inc.