Page 124 - Wastewater Solids Incineration Systems

92 Wastewater Solids Incineration Systems

10.0 OTHER THERMAL PROCESSING
TECHNOLOGIES

Several emerging thermal processing technologies can be used for solids treatment.
Some of these technologies, such as vitrification, are commercially available for pro-
cessing WWTP solids. Some technologies, such as gasification and plasma arc, have
been used commercially for other feedstocks but not WWTP solids; others, such as
SlurryCarb™, have been developed but not applied commercially. The following
briefly describes these technologies.

10.1 Vitrification
Vitrification, defined as a thermal process for converting minerals into glass, is an
emerging technology in the area of treating WWTP solids. Vitrification has a well-
established track record in other industrial processes, especially in furnaces used in
the glass manufacturing industry and slagging furnaces used in coal-fired power
generation.
Wastewater treatment plant residuals possess characteristics common to both
glass manufacturing and power generation and, therefore, play two important roles
in the vitrification process. First, the organic fraction provides the thermal energy
required to complete vitrification. Second, the mineral fraction (ash, clays, and min-
eral fillers) melts into a glass aggregate product with multiple beneficial construction
and industrial applications.
Japan has practiced vitrification of WWTP solids for a couple of decades. Until
recently, however, commercial vitrification of waste materials in the United States has
been limited to hazardous waste applications. Commercial-scale vitrification of high-
volume industrial WWTP residuals emerged in 1998 with Minergy’s Fox Valley Glass
Aggregate Plant (FVGAP) located in Neenah, Wisconsin. The FVGAP vitrifies
approximately 270 000 metric tonne/a (350 000 ton/yr) of wastewater solids from
several local paper mills into approximately 45 000 metric tonne/a (50 000 ton/yr) of
glass aggregate that is sold and used locally. Minergy subsequently developed a
®
second generation vitrification technology, GLASSPACK , applicable for individual
on-site use.
®
The GLASSPACK system is a patented, modular, closed-loop oxygen-enhanced
combustion process. It uses enriched oxygen to achieve temperatures that promote vit-
rification, provide complete destruction of organic compounds, and reduce emissions.
The high process temperatures completely melt the inorganic fraction into an inert,