Material Recovery Facilities (MRF)

Our scope of work is so wide that not only we are able to provide the client with the best design for his facility taking into account the type of waste, its daily load, the space available, the maintenance and operation costs, but we can also supply the client with all the needed apparatus, provide him yearly maintenance contracts and even go for the full yearly operation and maintenance

• i. Solid Waste Sorting Line
• ii. Recycling sorting line
• iii. Trommel
• iv. Various processing equipments

A solid waste sorting line (SWSL), solid waste sorting line (SWSL), also known as a dirty material recovery facility (dirty MRF), processes recyclables from a stream of raw solid waste and is typically used in rural areas with no curbside programs and communities that are not actively promoting recycling. A properly designed SWSL will process and recover between five and 45 percent of the incoming material as recyclables. The remainder of the material is used in a waste-to-energy facility, landfilled or otherwise disposed. Materials processed as recyclables include newspaper; steel and aluminum cans; brown, green and clear glass; polyethylene terephthalate (PET) and high-density polyethylene (HDPE) plastic containers. A SWSL serving a small community is typically designed to process less than 200 tons per day of solid waste. A SWSL serving a municipality can process 700 tons per day of solid waste. In many cases, independent private contractors who haul commercial waste operate SWSLs. Rather than hauling the waste directly to the landfill, the trucks stop at an SWSL and recyclable material is extracted. Only the material for which there is no market goes to the landfill.

SWSL designs can vary significantly. SWSL sorting systems can be fully automated, partially automated or consist solely of manual sorting systems. A combined system of automated and manual sorting usually begins with automated sizing and sorting and ends with manual sorting. The type of recyclables processed, and anticipated current and future processing rates need to be considered when designing an SWSL. SWSLs typically include a customer vehicle weigh scale and areas for queuing and maneuvering; recyclable shipping areas; vehicle parking; and outdoor storage of recyclables. The main building housing the SWSL will typically include a tipping floor for dumping mixed solid waste, areas for sorting materials and processing recyclables, interim storage of recyclable materials, and warehouse storage for processed recyclables awaiting shipment.

At the tipping floor, a rubber-tired loader spreads the waste out for inspection. At this stage, hazardous items and appliances are recovered. The loader then transports the solid waste onto incline conveyors. These conveyors transport the solid waste to a sorting area, usually located 10 to 20 feet above the ground level. Sorting is conducted at the designated sorting area, and recovered recyclables are dropped into the appropriate segregated collection bins.

In an automated system, the initial sorting operation usually removes bulky or dangerous items followed by waste screening to remove both small grit and aluminum and tin cans. An air classifier, the most common density sorting system used at a SWSL, is used to split the solid waste stream into heavy and light fractions, which allows the other sorting operations to specialize in the most common materials found in the respective fraction. The light fraction includes paper, aluminum cans and plastic, while the heavy fraction includes glass and ferrous materials. Equipment that sorts by chemical composition such as magnets and eddy current separators are commonly used in automated SWSLs.

Manual sorting follows automated sorting. The waste travels down a flat conveyor belt and workers remove the recyclables as they pass by. The conveyor belt for sorting may be as long as 50 to 100 feet to accommodate between five and 20 sorters. The length of the belt depends on the number of types of recyclables and the total amount of each type of recyclable being sorted.

Once the recyclables are separated, they must be processed into materials for sale. Processing typically includes baling for paper, steel cans, and plastic bottles, flattening or densifying for aluminum cans; granulating or perforating for plastic bottles; and crushing for glass bottles. Once processed, the materials are sold directly to specialty recyclers for reuse.

If the residual solid waste can be used in a waste-to-energy facility, additional processing is required. In addition to balers, SWSLs employ other processing equipment including shredders, pelletizers and compactors. A shredder reduces the volume and increases the uniformity of the residual solid waste for use at a waste-to-energy facility. Pelletizers receive shredded waste and extrude it under high pressure to form small pellets. The pellets may then be used as fuel for a furnace or power plant.

Compactors are typically used to process residual solid waste bound for landfills. Compactors are large balers that compress either shredded or un-shredded waste into large bales weighing up to 29 tons. The compactor loads the bales into trailers for transport to a disposal site, which ensures the maximum legal load to reduce hauling costs.

Benefits:

• Saves landfill space by diverting recyclable materials.
• Allows municipalities to meet mandated goals for the reduction of landfilled waste.
• Income is generated from the sale of recyclables.
• Cost savings in landfill tipping fees.
• Conserves resources.

A recycling sorting line (RSL), also known as a clean material recovery facility (clean MRF),

processes commingled recyclables from curbside collection programs, drop-off sites, and satellite recycling centers. A properly designed RSL will process and recover up to 90 percent of the collected material. Recovered material is ultimately resold to specialty recyclers. Materials processed include newspaper; steel and aluminum cans; brown, green, and clear glass; polyethylene terephthalate (PET) and high-density polyethylene (HDPE) plastic containers. An RSL serving a small community is typically designed to process less than 50 tons per day of recyclables. An RSL serving a municipality can process 200 to 300 tons per day of recyclables.

RSL designs can vary significantly. RSL sorting systems can be fully automated, partially automated, or consist solely of manual sorting systems. A combined system of automated and manual sorting usually begins with automated sizing and sorting, and ends with manual sorting. The type of recyclables processed, and anticipated current and future processing rates need to be considered when designing an RSL. However, the basic features of the RSL site are similar for all types of RSLs. Each RSL includes customer vehicle weigh scales; areas for queuing and maneuvering; recyclable shipping areas; vehicle parking; and outdoor storage of recyclables. The main building housing the RSL will typically include a tipping floor for dumping recyclables, areas for sorting materials and processing recyclables, interim storage of recyclable materials, and warehouse storage for processed recyclables awaiting shipment.

The RSL tipping floor is divided into separate areas for source-separated recyclables and commingled paper and recyclables. At the tipping floor, a rubber-tired loader transports the recyclables onto incline conveyors. These conveyors transport the recyclables to a sorting area, usually located 10 to 20 feet above the ground level. Sorting is conducting at the designated sorting area, and recovered recyclables are dropped into appropriate segregated collection bins.

Automated sorting systems distribute recyclables into containers based on size, density, and/or chemical composition. These automated sorting systems may consist of trommels, disk and vibrating screens, density sorters, and magnetic separators. A trommel, or rotating drum screen, sorts material by size. The outside of the trommel consists of a screen with small holes that grow larger along the length of the screen. Small containers, like aluminum and tin cans fall through the smaller screen holes. Plastic soda bottles and milk jugs pass through the larger holes.

Disk and vibrating screens also sort by size. The disk screen employs a series of parallel rotating shafts affixed with discs that are staggered from one shaft to the next. Between the shafts and the discs are openings where small materials fall as they pass over the surface of the rotating discs. Larger materials ride along the discs onto a conveyor.

Density sorting subjects the materials to an air stream, also known as an air knife or air classifier. The air stream velocity is pre-set so that lighter materials such as plastic or aluminum cans are blown away from heavier materials such as glass containers.

Magnetic equipment sorts materials by removing ferrous metals. Eddy current separators create an electric current in aluminum materials that propels the aluminum away from other materials.

Manual sorting systems generally consist of flat conveyor belts where workers remove recyclables by hand from the belt as they pass by. The conveyor belt for sorting may be 50 to 100 feet long to accommodate between five and 20 sorters. The length of the belt depends on the number of types of recyclables and the total amount of each type of recyclable being sorted. Glass is usually separated by hand, in order to ensure the separation of clear, brown, and green glass.

Once the recyclables are separated, they must be processed into materials for sale. Processing typically includes baling for paper, steel cans, and plastic bottles; flattening or densifying for aluminum cans; granulating or perforating for plastic bottles; and crushing for glass bottles. Once processed, the materials are sold directly to specialty recyclers for reuse.

RSLs operated by municipalities have had a dramatic effect on reducing the reliance on landfills. The use of RSLs has, in many states, been mandated by legislation requiring a significant reduction in landfill disposal. California Assembly Bill 939 requires every city and county in California to reduce its landfill waste stream 25% by 1995 and 50% by the year 2000. Similar mandates are now law in many other states. The employment of RSLs in conjunction with commingled recycling programs have greatly assisted municipalities in achieving these goals.

Benefits:

• Saves landfill space by diverting recyclable materials.
• Allows municipalities to meet mandated landfill reduction goals.
• Income is generated from the sale of recyclables.
• Cost savings in landfill tipping fees.
• Conserves resources.
• Generates community interest in recycling.

A trommel is a rotary cylindrical screen that is typically inclined at a downward angle that, combined with the tumbling action of the trommel, separates materials of different density. Trommel screens are used to separate commingled recyclables, municipal solid waste components, or to screen finished compost from windrow and aerated static pile systems.

Trommel screens are used by material recovery facilities to separate compostable paper from glass and other contaminants in previously shredded municipal solid waste. Smaller trommels have been used to separate labels and caps from crushed glass. Some trommels are designed to let paper pass through the screen while diverting heavier materials to re-crushing or a landfill. Other applications require multi-stage trommel screens which have meshes or plates of different aperture sizes. These screens may be used for the separation of commingled wastes with components of various sizes.

In composting applications, trommel screens are used to enhance the market value of finished compost by separating large particles and non-degraded bulking agents such as wood chips from the organic fines. The fines are used or sold as a soil amendment and the bulking agent can be re-used. Trommel screens are used when a high quality end product is desired.

The factors that influence the separation efficiency of trommel screens are:

• Characteristics and quantity of the incoming materials
• Size, proportions, and inclination of the cylinder screen
• Rotational speed
• Clogging of screen openings
• Size and number of screen openings

The types of trommel screens available range from electrically or hydraulically stationary units with or without conveyors and hoppers to electrically or hydraulically self-contained, portable or mobile units with conveyors, cleaning brushes, and variable speed trommel drums.

Benefits:

• Allows recovery of recyclable and compostable wastes from mixed waste stream.
• Produces a high quality compost product for use in landscaping.
• Produces a more marketable compost product that has higher value.
• Allows reuse of compost bulking material.
• Compost reduces the amount of waste to be disposed. Complete recovery of yard waste will reduce the amount of waste disposed in landfills by an average of 12% (U.S. EPA, 2000).

Magnetic-based separators - Magnetic separators create magnetic fields that attract ferrous metals and remove them from the rest of the feedstock stream as it travels along conveyors. Magnetic separators are among the most effective and inexpensive unit processes available for sorting and removing contaminants from the feedstock. The economic benefits of these devices are enhanced by selling the scrap metals these units separate from the compostable materials. The efficiency of magnetic separators depends primarily on the quantity of materials processed and the speed at which they pass through d-se magnetic field. The size and shape of the ferrous objects, as well as the distance between the magnet and the objects, also are important variables. To increase the efficiency of the separation process, more than one magnetic separation technology can be used in series with another. Applying air classification (described below) prior to magnetic separation minimizes the contaminants in the scrap ferrous even further.

Eddy-current machines - Eddy-current machines separate aluminum and other nonferrous metals from MSW. These machines generate a high-energy electromagnetic field that induces an electrical charge in nonferrous metals (and other materials that conduct electricity). The electrical charge forces these materials to be repelled from noncharged fractions of the feedstock material. The feedstock should be conveyed to eddy-current machines after magnetic separation to minimize contamination by ferrous metals. Recovery rates for eddy-current separators vary with the depth of the material on the conveyor belt, belt speed, the degree of preprocessing and the strength of the magnetic field. Full-wale trials and manufacturer estimates of separation efficiency in MSW applications range from 50 to 90 percent.

Air classifiers - Air classifiers separate feedstock materials based on weight differences; for example, the heavier fractoions (metals, glass, ceramics, and rocks) are removed from the lighter materials. The heart of an air classification system is an air column or throat into which the materials stream is fed at a metered rate. A large blower sucks air up through the throat, carrying light materials such as paper and plastic. These then enter a cyclone separator where they lose velocity and drop out of the air stream. Heavy materials fall directly out of the throat. An important consideration when using air classifiers is that although most of the heavier materials separated out are noncompostable, some materials that fall out (e.g., certain food materials and wet paper) can be composted.

Air classifiers typically are used after the feedstock has been size-reduced. Separation efficiency in experimental application of air classification systems has reached 90 percent for plastics and 100 percent for paper materials. In combination with screening and size reduction, air classification can be used to significantly reduce metal contaminant levels.

Wet separation technologies - Wet separation technologies are similar to air classification systems in that they separate materials based upon density, but water replaces air as the floating medium in these technologies. After entrainment in a circulating water stream, the heavy fraction drops into a sloped tank where it moves to a removal zone. The lighter organic matter floats and is removed from the recirculating water using stationary or rotating screening systems similar to those employed by wastewater treatment facilities. This technology is particularly effective for removing glass fragments and other sharp objects.

Ballistic or inertial separation - This technology separates inert and organic constituents based upon density and elasticity differences. Compost feedstock is dropped on a rotating drum or spinning cone and the resulting trajectories of glass, metal, and stones, which depend on density and elasticity, bounce the materials away from the compost feedstock at different lengths.

Shredder/ Hammermill.-. These units are used to reduce the size of the incoming waste to homogeneous dimensions to ease the composting process. These units can also be used to reduce almost every type of waste to small pieces (tire shredder, green wastes, plastics...)

Bag opener.-.These units are usually installed at the front end of a sorting system to open and empty plastic bags/ sacks containing household recyclable, municipal solid waste (black bag waste) or biodegradable waste.

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