SOUTHEAST VIRGINIA RDF PLANT
IS AMONG FIRST IN NATION

  • An aluminum picking station to collect all beverage cans and two magnetic separators to remove all ferrous material; these items are recovered for sale.
  • Two dust collection systems on each line--a 50,000-cfm system to control dust from the trommels, magnets and conveyors; and a 15,000-cfm system on the shredder discharge.
  • Eleven Heil belt conveyors on each line, ranging from 24- to 60-inch widths, to inter-connect all systems.
  • Ten additional Heil belt conveyors, common to all processing lines and used to transport ferrous materials, rejects and RDF.
  • A complete Heil control system, including console, programmable controller, motor control centers, medium voltage starters and local control panels on each processing line.

Fine Tuning the System
Hadfield said that due to the design of the Navy's boiler fuel feed equipment, oversized pieces of RDF would cause intermittent jams in the system.  The original disc screens that Heil supplied to insure final sizing of the RDF did not totally eliminate the fuel feed problems.  In addition, they required frequent cleaning, which reduced system throughput.
SPSA, Heil, and project engineer HDR Engineering resolved the situation by:
  • Reconfiguring the shredder's hammers, producing a more uniformly sized RDF.
  • Reducing oversized pieces by conveying the secondary trommel "overs" material--after aluminum recovery--back through the shredder.
  • Making several changes to the boiler fuel feed system.
These modifications allowed the disc screens to be bypassed, resulting in greater system throughput and lower operating expenses, according to Hadfield.  He said:  "The most improvement in system throughput occurred in 1990, when SPSA contracted with the Navy to operate and maintain its power plant.
"The operation of both facilities produced better communication, less 'finger pointing' and allowed SPSA more freedom to revise and maintain troublesome areas in the power plant," Hadfield added.
The SPSA plant's ambitious goals in the areas of overall tonnage throughput in the system, processing 1,500-2,000 tons per day of municipal solid waste, are now being met, according to the deputy executive director.
"Based on the sustained performance of the RDF Plant, we feel Heil's package met our needs very well," Hadfield said.

A portion of the processing operation for SPSA's refuse derived fuel plant, designed and installed by Heil Engineered Systems. At right foreground is a secondary trommel screen, with a primary trommel just behind it. Also pictured are portions of the belt conveyor system that connects the entire operation, while the duct work above contains the 50,000 cfm dust collection system.

The $50 million RDF plant, the third largest RDF/materials recovery facility in the country, sits on a 21-acre site just outside the Navy's shipyard facility.  The plant is equipped with four truck scales, two scale houses, four fixed cranes and an intricate network of conveyors which transport refuse derived fuel to the power plant.
Three Processing Lines
Waste is handled in three identical process lines, each of which can process 80 tons of raw waste per hour, according to Hadfield.  Two of the lines run two eight-hour shifts a day, with the third kept in reserve.
"The entire processing system was designed, supplied, installed and tested by Heil Engineered Systems," Hadfield said.  "The specifications for the system we wanted were quite exact; Heil provided the overall design package and the proper equipment to meet those specifications."
According to Heil's design of the processing operation, each line contains the following equipment:

  • Horizontal and inclined apron infeed conveyors, each 7 feet wide, to handle the raw refuse.
  • A Heil primary trommel, 12.5 feet in diameter and 60 feet long, with spikes in the forward section to rip open plastic bags and 6-inch holes to separate smaller sized waste for further screening separation.
  • A 1,000 horsepower Heil Model 92B vertical shaft shredder, equipped with explosion vents and a Fenwal explosion detection and suppression system.  The shredder reduces incoming waste to less than 4-inch size particles for fuel.
  • A two-stage secondary trommel, also from Heil, which picks up the waste sifted through the primary trommel for further screening.  Fifty feet long and 10.5 feet in diameter, the trommel separates all waste larger than 1.25 inches, which continues through the trommel to the power plant.  Anything smaller, essentially glass and grit, is transported to the landfill.
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