Sludge disposal problem converted into energy conservation advantage
At the Abitibi-Price hardboard plant in Alpena, Michigan, sludge collected by dissolved air flotation (DAF) is dried and pelletized. The pellets are burned as supplemental fuel in combination with coal. This is expected to reduce the amount of coal used by about 15%. The system is not self-sustaining. The cost of equipment, labor, and chemicals for treatment balances off against the coal savings to make the new system break even. Elimination of a disposal problem and improvement of environmental conditions make the added investment worthwhile. The Btu content of the pelletized sludge is about 2/3 that of coal. The DAF equipment serves to remove biological solids from the water and prevent them from settling. In the DAF process, air is dissolved under pressure in the mixture of water and solids (the dead microbes). When this is released into a long trough, the air is expelled as tiny bubbles, which rise to the surface, carrying the suspended solids with them in a foamy mass. When the foam is skimmed, about 95% of the carcasses are captured. The collected solids go to a sludge dewatering machine, which squeezes off the water to create a relatively high (15-25%) solids content. The dewatered sludge is delivered to the dryer, where moisture content is reduced to about 7-8%, and the sludge is automatically pelletized (1/16 to 3/16 in diameter pellets). The pellets are delivered to a screw conveyor which transports them to the power house.
- OSTI ID:
- 6935093
- Journal Information:
- Am. Logger. Lbrman; (United States), Vol. 6:4
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
REFUSE DERIVED FUELS
FUEL SUBSTITUTION
PRODUCTION
SLUDGES
PELLETIZING
CALORIFIC VALUE
COAL
COCOMBUSTION
DRYING
ECONOMICS
ENERGY CONSERVATION
ENERGY SOURCES
MICHIGAN
WASTE DISPOSAL
WATER REMOVAL
CARBONACEOUS MATERIALS
CHEMICAL REACTIONS
COMBUSTION
COMBUSTION PROPERTIES
FABRICATION
FEDERAL REGION V
FOSSIL FUELS
FUELS
MANAGEMENT
MATERIALS
MOLDING
NORTH AMERICA
OXIDATION
REMOVAL
THERMOCHEMICAL PROCESSES
USA
WASTE MANAGEMENT
090400* - Solid Waste & Wood Fuels- (-1989)
320305 - Energy Conservation
Consumption
& Utilization- Industrial & Agricultural Processes- Industrial Waste Management
140504 - Solar Energy Conversion- Biomass Production & Conversion- (-1989)