C&D Processing 101 : The Eco-Star Screen
The screen is considered the heart of every recycling system, as screen performance determines the recovery rate of materials. In addition to improved separation and reduced power consumption, the Eco-Star anti-wrapping feature has proven to reduce scheduled and unplanned maintenance requirements. Several recycling facilities in Europe that process Food Waste, Biomass, Commercial and Industrial Waste, along with Construction and Demolition material, have improved the recovery rate of materials and lowered operating costs with the Eco-Star dynamic disc screen. They consider Eco-Star to be the preferred screening method for difficult materials that contain stretch wrap film, plastics, wire, metals, and wet, stringy waste.
In the USA, a considerable amount of the waste that is generated on every renovation and construction project can be recycled. The C&D waste is loaded into a roll-off container or trailer and transported to a recycling facility. In order to reduce transportation costs the C&D waste may be crushed or combined with soils and other contaminants from the construction site. At the recycling facility, the recycling process begins as the C&D waste is presented to a screen. Some recycling facilities deposit the material directly onto the screen with an excavator while others use a conveyor to discharge the material onto the screen. The primary objective for the screen is to separate the C&D waste into manageable fractions, commonly referred to as Fines, Middles and Overs.
The Fines (nominally 2” and smaller ) may contain soils, asphalt, brick, concrete block, metals and other items. Magnets will capture the ferrous metals, but recovering of aggregates from Fines will require the removal of the soils with a density separator or Destoner. The Middles fraction (nominally 2” – 10” fraction) is processed with magnets and density separators to capture ferrous metals and aggregates. It can be very difficult to capture items manually on a sort belt from the Middles fraction. Optical sorters and near-infrared detectors can be utilized to identify and separate wood, metals and plastics from this fraction. The Overs material (nominally +10” fraction) discharges onto a sort belt and laborers remove items such as aggregates, steel, plastics, clean wood and old cardboard containers (OCC). Even though OCC is a valuable commodity, when it comes in contact with waste the value is negatively affected as OCC tends to absorb any liquids.
After the manual separation, items discharged from the sort belt are commonly referred to as Residuals. In most cases, the Residuals are transported and disposed of at a landfill. In certain cases, the Residuals may be acceptable as an Alternate Fuel or processed waste. New construction waste consisting of packaging materials and cut offs from new material such as plywood, dimensional lumber and drywall are easier to recover and more valuable than items from demolition waste. New markets for select items recovered from demolition waste need to be created in order to justify the expense of recycling demolition waste. Some materials are easier and more profitable to process. Choosing the correct screen will enhance the operation and improve your bottom line.