The GlassPack® melter features a three-zone operation, comprised of separate but interconnected chambers that include a melting and combustion zone, a phase separation zone and a gas cooling zone.
Zone 1: Melting and Combustion
Feedstock that has been pre-dried to approximately 90% solids or more is injected along with air or synthetic air (see Closed-Loop Configuration for a more detailed description of synthetic air) into the Zone 1 chamber. In this zone, the organic component of the sludge is completely combusted, liberating a significant amount of heat energy. This heat, along with any heat from the co-fire fuel (typically natural gas), results in temperatures of approximately 2,400 to 2,700 degrees Fahrenheit. At these high temperatures, the mineral (ash) component of the feedstock melts to form a pool of molten glass at the bottom of the Zone 1 chamber. The high temperature environment provides very high destruction efficiencies of any organic compounds that may be contained in the feedstock.
Zone 2: Phase Separation
Phase separation of the molten glass and exhaust gas occurs by gravity draining the molten glass from Zone 1 through a drain port on the bottom of the Zone 2 chamber. The molten material drops into a quench tank and is cooled into the glass
aggregate product. The exhaust gas is directed out
of Zone 2 through a refractory lined duct into zone 3.
Zone 3: Gas Cooling
The exhaust gas from Zone 2 is 2,400 to 2,700 degrees Fahrenheit. This gas is cooled through dilution mixing with lower temperature gases obtained external to the melter. A typical source of lower temperature gas is the recirculation flow from a closed-loop melter installation.
Reducing the temperature offers two important cost-saving advantages. This system can eliminate refractory-lined ductwork exterior to the melter, and can cool and carry over particulate below the softening point, thus eliminating ductwork fouling. The temperature of the Zone 3 exit gas varies depending on the temperature and quantity of the dilution gas, but is typically in the range of 700 to 1,400 degrees Fahrenheit. Higher temperature exit gas can provide for higher efficiencies in heat recovery.