Air Quality

Below: National Park Vista on a Good AQ Day

 

EPR air fed gasification systems are the cleanest and most efficient means available for converting solid waste to energy. Because of their design and operational features, they also and have the lowest lifecycle impact on air quality of any waste disposal process, including landfill.

 

 

 
Above: Same Vista on a Poor AQ Day

EnviroPower Renewable works with equipment manufacturers and operators to design the cleanest air fed gasification systems available. Designing for clean operation starts with the procedures used to collect and separate the refuse derived fuel that will be used in the gasification systems, and continues through the thermodynamic design of the facility and selection of stack gas cleaning equipment.

 

 

Air quality impact of EPR gasification systems is lower than for any alternative means of solid waste disposal, including landfill. EPR waste to energy gasification systems are designed and operated as a component of a comprehensive waste management solution. Our total waste management solutions typically include the following: 

 

 

 Recycling: Any materials that can be sent to economically viable recycling market will be removed from the waste stream and recycled.  In fact, the waste materials are first sorted and recycled at an offsite Material Recovery Facility (MRF), and then are again sorted, and recyclables and unacceptable waste are removed at the EPR Sorting Facility. The only materials that will be gasified are combustible residues from the sorting lines that have no value as recyclable materials, or for which no viable market exists.

Fuel Selection: Refuse derived fuel (RDF) is generated by sorting the incoming waste streams and removing recyclable materials, non-combustible materials (also known as inerts), and any hazardous materials.

Characteristics of the RDF that is used in the facility are highly dependent on the incoming waste stream. The fuel selection, fuel feed rate and under fire air feed rate are computer controlled to maintain optimal temperature and oxygen partial pressure inside the gasification reactor. 

 

Odor and Fugitive Dust: EPR facilities only accept dry combustible materials, as contained in construction as demolition waste, source separated commercial waste, and residential municial solid waste. These materials are comprised mainly of wood, plastics, cardboard and paper, carpeting, roofing material, with minor amount of leather, textiles, and other fiber materials.  Because all tipping and sorting operations are conducted inside a building at negative pressure, the EPR facilities are not sources of odor or fugitive dust emission.

Flue Gas Clean-up Process Units: Flu gas from the boiler is then routed through a series of process units to neutralize or remove remaining particulates or criteria pollutants. These units include a dry scrubber to remove any acid gas residues including SOx and traces of HCl. The dry scrubber is followed by an selective catalytic reduction (SRC) unit that provides a reagent and catalyst that promotes a reaction with any remaining NOx to convert it to molecular nitrogen (N2) and water.

 

Any remaining particulate in the flue gas at this point is removed by a high efficiency electrostatic precipitator (ESP). The ESP unit is followed by a fabric filter baghouse, into which activated carbon is injected to absorb any traces of organic molecules remaining in the gas stream. The baghouse also serves as a final filter for any particulate that has not already been removed by the ESP.

Image above shows the initial placement of bulk bags of inert ash in a temporary lined landfill. (Inert waste need not be bagged for permanent placement.)

Inert Landfills: Gasification of solid waste results in an inert, non-leachable frit or slag material that can be landfilled without the subsequent generation of gas phase products of anaerobic digestion. This is because inert landfills contain no organic materials that support the metabolism of anaerobic bacteria.  In contrast to conventional practice of sending organic materials to landfill, inert waste landfills produce no carbon dioxide, methane or odor causing gasses such as hydrogen sulfide.

 

Thus, gasification of municipal solid waste, with inert landfilling of the resulting frit or slag, results in far less green house gas emissions than conventional landfill practice.

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A paper describing an air quality impact study for an EPR gasification system in the Las Vegas Valley, please click here.