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Glass Furnace
Technology
Feasibility Study
Vitrification vs.
Incineration
Technologies > Glass Furnace Technology > Vitrification vs. Incineration
The Differences Between Vitrification and Incineration
Unlike incineration, vitrification melts the sediment instead of burning it. Vitrification, also known as Glass Furnace Technology (GFT), requires less energy, uses oxygen rather than atmospheric air, produces an inert and usable end product, produces less air emissions and represents a more complete treatment for PCB-contaminated sediment.
GFT is different from incineration in the following ways:
Burning vs. Melting
Incineration is defined as the burning of waste to reduce the volume of material that needs disposal. River sediment is made up mainly of minerals and, as a result, does not burn. Therefore, river sediment is not suitable for incineration or other combustion-based processing. In contrast, the glass furnace used in GFT vitrification uses heat to melt minerals into glass. This is important in processing river sediment, because its mineral component is an ideal feedstock for glassmaking in the GFT.
Requires Less Energy
Historically, industry has made attempts at incinerating contaminated sediments. Incinerators require feedstocks that burn; however, sediment is mainly made up of minerals and does not burn. Therefore these incineration systems have required very high use of auxiliary fuels such as natural gas. The thick refractory used in GFT provides very high insulating value and keeps the process heat inside the melting chamber. This allows the GFT to conserve considerable energy compared to incinerators, which must use significantly thinner refractory due to restrictions that are inherent to their design (e.g., rotary kilns or boilers).
Use of Oxygen
The state-of-the-art in glassmaking furnaces, such as the GFT, utilizes pure oxygen in the melting chamber. Incinerators, in comparison, use atmospheric air, which only contains 21% oxygen. The remainder of air is nitrogen (78%) and argon (1%), which are gasses that significantly penalize the efficiency of any thermal process. The use of oxygen allows the GFT to raise the sediment to temperatures well above the levels required for complete destruction of any organic contaminants such as PCBs.
More Complete Treatment
The GFT has undergone an extensive review by the U.S. Environmental Protection Agency (EPA), which monitored a demonstration project operated round-the-clock for a one-week period, using PCB-contaminated sediment from the Fox River. The EPA's report showed that more than 99.999% of the PCBs were destroyed, in compliance with the EPA's "six nines destruction" rule. The analysis also showed that no dioxins or other pollutants were created in the process.
Creates Inert and Usable Product
Incineration results in large amounts of ash, a byproduct of the process. In comparison, GFT does not. Instead, the minerals that would otherwise create ash in an incinerator are melted into inert and usable glass in the GFT. The glass is used in construction applications as glass aggregate, for such items as asphalt paving, concrete and building foundations.
Less Air Emissions
Burning processes like incineration create a variety of pollutants that are significantly reduced in the use of GFT vitrification. The factors listed above all combine to allow the GFT to generate significantly less exhaust gas. A further benefit is that any pollution control equipment that might be included in a GFT facility is much smaller and less complex than the equipment necessary for incineration.
Minergy Corp., located in Neenah, Wis., specializes in the vitrification, or melting, of waste materials into glass aggregate, an inert glass product used by the construction industry. Waste materials processed by the company include sludges, sediments and soils. Minergy has owned and operated one of the largest vitrification facilities since 1998. Established in 1993, Minergy is a wholly owned subsidiary of Wisconsin Energy Corporation.
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