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BROOKFIELD, WI (JUNE, 1998)…
HEIL ENGINEERED SYTEMS recently completed startup and testing of new processing equipment to handle approximately 270,000 tons per year of municipal trash from the Dade County, Florida (Miami area). Dade County is a rapidly growing area with garbage (MSW) and trash (primarily yard waste containing additional bulky waste and construction/demolition material) tonnage growing beyond the capacity of the existing 3,000 tpd Miami Dade County Resources Recovery Facility (The Plant). Additional landfilling of trash in the existing landfill was also considered undesirable.
A private, local Independent Power Producer (IPP) had constructed a solid fuel power plant and needed additional biomass-type fuel to supplement their seasonal consumption of sugar cane bagasse.
The Miami-Dade County Dept. of Solid Waste Management, Montenay International Corp. (operator of The Plant) and the IPP structured a contract to modify the plant to produce high quality fuel and soil products from the trash. The fuel size requirements were: 13% maximum by weight passing a ¼" x ¼" screen and 95% minimum by weight passing a 4" x 4" screen. The fuel quality requirements were: 3% maximum by weight plastic and rubber content; 2% maximum by weight painted and treated wood; and 5% maximum by weight non-combustible (inert) material.
The IPP also agreed to accept a soil product with similar sizing and quality requirements. The separation of Dade Co. municipal trash into rejects, ferrous fuel, primary soil and secondary soil had never been attempted with the quality and throughput requirements of the project participants.
Prior to detailed process design, numerous samples of municipal trash were hand sorted, shredded, screened through various trommel screen openings, destoned and analyzed to determine whether fuel and soil requirements could be achieved in a full scale system at 110 tons per hour. Several months of testing by Montenay Power and Heil produced the confidence necessary to modify the plant.
The major components of the 26 million-dollar project were as follows:
Construct a new truck scale facility to weigh incoming trash and outgoing product [rejects, fuel, primary soil and secondary soil (broken concrete, rocks, etc.)].
Construct a new tipping building for trash storage to allow the existing tipping floor to be used for the initial separation of large reject items via large front-end loader and small skid/steer loaders. Modify and add new infeed conveyor systems to each of the three existing trash shredding lines to allow easier removal of rejects by hydraulic grapple crane and sorting personnel.
Construct air-conditioned enclosures for the sorting personnel located along each side of the new sorting conveyors.
Modify the three existing shredders by eliminating their compression feeders, adding explosion detection/suppression equipment and explosion vent stacks through the roof.
Construct a common conveyor system to handle the rejects removed from each of the three lines.
Construct a common system of trommels, destoners, conveyors, and dust collection equipment to separate the output of all lines (110 tph) into fuel, primary soil, secondary soil and oversize rejects.
Construct a building to enclose the separation system and another adjacent building with large concrete bunkers to store fuel, primary soil and secondary soil.
Construct a new electrical control system containing motor starters, programmable logic controllers, I/O racks, IBM compatible computers (redundant) and touch screens (redundant).
Except for the truck scale and buildings, Heil Engineered Systems designed, provided, installed and tested the processing systems as described above. The project was developed over three years, was built in 1996 and successfully commissioned in 1997. The existing shredding lines were modified in sequence to allow continued operation of the plant.
Several unique features were required due to the constraints of the existing facility:
A section of the shredder explosion vent stack had to be hydraulically raised and lowered to allow passage of an overhead bridge crane used for shredder maintenance.
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