Material Sorting Systems
A myriad factors influence materials taken in by MSW operations at any given time—among them: the price of oil affecting plastics, changing packaging materials, and local regulations.
Municipal solid waste (MSW) operations face three primary goals in sorting material: the ability to do so in a manner that most efficiently saves time and money, the potential for generating the optimal post-sort revenue, and having a process that ensures safety.
Many operations are moving toward ballistic separators and systems that offer versatility against the backdrop of an ever-changing waste environment. Some manufacturers offer a chance to test the equipment before making an investment. Stadler America, a full systems design integrator, recently introduced to the North American market ballistic sorters for separating materials.
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There has been only one version of these types of machines available to the market over the last several years. MSW operations have requested the development of multiple versions that can handle various applications, notes Matt Everhart, CEO of Stadler America.
“The result is the ability to be able to have a system without rotational screens,” says Everhart. “That is the goal the industry is moving toward because as the amount of films and corrugated brown fiber grow in the waste stream and the amount of newspaper and other items that used to be problematic decrease, the rotational screen has become a real maintenance bottleneck within a typical American plant.”
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One version of the Stadler ballistic sorter is designed to screen cardboard away from other two-dimensional materials. “We have machines that are specifically designed to separate items strictly off of dimensionality—separating containers, bottles and cans away from two-dimensional fibers and films,” notes Everhart.
AMUT North America offers Ecotech, an elliptical ballistic separator that operates much like the exercise machine of the same name, notes Company President Anthony Georges.
The elliptical ballistic separator is designed for the need to separate two or more fractions having different physical characteristics and coming from a continuous stream of wastes from municipal single-stream or a dirty MRF. A series of parallel paddles applies a strong shaking to all of the waste to achieve separation before conveying the various material types to intended destinations.
The overlapped stages of AMUT’s SBC 202 are designed to enable the best operating conditions for the separation of the inlet flow composed of soft packages, mixed paper and film, and plastic containers into four different streams of outlet material:
- Two-dimensional (2D) large flat fraction composed of paper, cardboard, and film
- 2D small flat fraction mainly composed of small paper and plastics
- Small passing/undersize fraction that also can be used as fuel
- Three-dimensional (3D) heavy and rolling fraction composed of plastic, ferrous, and non-ferrous containers
Depending on material, the capacity ranges from 7 to 12 tons an hour.
The B Series elliptical ballistic separators are designed to enable optimal conditions for the separation of mixed waste into three groups:
- 3D rolling fraction mainly composed of hemisphere-shape containers for liquids and other packages
- Scrap (fines) composed of a mixed material having calibrated size as a result of the operation of the drilled paddles
- 2D flat fraction mainly composed of waste such as packaging, OCC, and flexible fibers
The elliptical ballistic separator model SB 202 can be supplied also in the QUAD version with parallel execution and fed by an alternative reversible belt. The QUAD version is designed to separate large quantities of material with alternate feeding helping the selection of mixed material with different shapes and specific weights by using the effect of load/unload volume change.
The MPC 206 paper and cardboard elliptical ballistic separator divides the inlet flow into two different material streams through the wave motion of paddles, as well as the holes with variable section placed on their surface. Fractions of output material are cardboard size A4 (8.3 x 11.7 inches) and mixed paper, the size of which depends on the screening holes dimension. Changing holes makes it possible to separate the mixed paper from the stream of newspapers and magazines.
AMUT offers a mobile single stage hook-lift ballistic separator designed to enable optimal operating conditions for the separation of packaging in three distinct streams: flat fraction, rolling fraction, and sieved fraction (nor valorizable) for rejection. It separates materials mainly composed by polyethylene film having the size of shop bag and domestic collecting bags, net food packaging, generally soft packages, and any paper and cardboard.
Rolling fraction is composed of containers for liquids and packages having hemispherical shapes, such as aluminum and tin can. Rejection consists of mixed materials of a size passing through the holes of the blades.
AMUT also makes a De-Labeller, which is designed to separate labels from plastic bottles to enable a higher-quality product for market.
AMUT’s ballistic separators have entered the North American market in the last two years with the technology having been used in Europe for more than a decade.
In the elliptical technology, objects such as rope will bounce off or down depending on heavy they are and how it’s set up, says Georges. “Floatables move up and three-dimensional objects and heavy objects will move down,” he says. “Small fines will slip through the grid, which can be adjusted for different things as well. It can be adjusted down to five-eighths for a fine cut such as getting the organics out or the grid can be changed for a two-inch, which is pretty much the standard in MSW at this time.”
An 8 x 11 grid can be used to separate OCC from newsprint. The newsprint will fall through while the OCC will float over top.
AMUT has made available a mobile unit to North American operations for evaluation and a better understanding of how it works. MSW operations are given a three- to four-week trial period to test the equipment at no cost.
“They can get a good understanding of it and use it for different processes,” says Georges. “If they want to separate the organics stream, single stream, or mixed wastestream, they can use it for a few days in each of those operations. Some operations have two or three MRFs in the city, and they’ll want to take it to those different MRFs.”
One operation using the AMUT technology is Casella Recycling’s Lewiston, ME, plant. Casella is a northeast regional public company with a half-billion in revenues, which provides integrated services such as hauling, landfill, and recycling.
Two of the four systems in the operation include a unit with a double stage on the three-dimensional objects to separate paper or plastics from the 3D containers and an OCC unit with an 8- x 11-inch opening. The other two serve as polishing units.
Bob Cappadona, the company’s vice president of recycling, notes the company’s recycling efforts include the processing and marketing of 700,000 tons of traditional recyclables in single-stream MRFs, several commercial operations, and a brokerage division serving seven states. One of the single-stream sites is in Lewiston.
“It’s a great piece of equipment,” notes Cappadona of the AMUT elliptical ballistic separator. “A significant piece from an operation standpoint in single-stream equipment is the maintenance and operating costs. A big piece within the system is the separation mechanisms. The ballistic separation technology that AMUT supplied us with is typically used as a polishing mechanism, but they designed it as a major separation mechanism in the systems.”
Cappadona notes the technology provides the same quality his operation looks for in traditional recycling equipment or disk screens. “It replaces the disk screens and the maintenance associated with disk screens since it doesn’t have any disk screens,” he points out. “All the maintenance is a replacement of bearings, so there is very much less maintenance and operating costs.”
The operation had previously used disk screens. “It serves just as well as any type of disk screens,” notes Cappadona. “It’s a little bit restricted with regards to throughput; if you want it to increase throughput, you would need additional separation unit.”
The elliptical ballistic separators are offering comparable bales to that of the disk screens. “It produces a high quality,” says Cappadona, adding that his operation is able to sell newsprint domestically.
“If you can put out better quality bales, you’re going to get a better quality price,” notes Georges.
Green Machine systems are designed to process both dry and wet MSW waste and can accommodate removal of most commodities. “We find the systems which concentrate on the sorting of large OCC, mixed paper, mixed plastics, ferrous and non-ferrous recyclable materials with a fines removal capability are the most profitable,” says Marc Lindemann, sales director/operations–waste processing and energy conversion.
Green Machine is designed to place profitability ahead of recovery rates, notes Lindemann. “Most large-scale MSW processing plants fail primarily because they are too costly to deploy, too costly to operate, and produce a contaminated recyclable material product,” he contends. “It is our philosophy to process large tonnages at the lowest processing cost per ton while capturing the high value recycling commodities at recovery rates that don’t adversely affect throughput.”
That in turn mitigates cost situations on shipping material to landfills, says Lindemann, adding the company is focusing its efforts on transfer stations as an optimal business model.
CP Group designs and manufacture screens, optical sorters, trommels, and other sorting equipment to separate MSW material by size, pulling out the largest items first, and refining the screening process more, diverting various materials into the desired areas.
The CPScreen uses cam-discs to agitate material and carries fiber over while allowing containers and 3D material to fall back. Optical sorters separate plastics, glass, metals, and fiber and are designed to identify challenging materials such as black plastics, short fill containers, labels, and PET-G.
CP Group has engineered and installed several mixed waste processing plants in recent years that have yielded profitable results, points out Terry Schneider, President and CEO of CP Group.
Case in point is the Sunnyvale Material Recovery and Transfer (SMaRT) Station in Sunnyvale, CA, operated by Bay Counties Waste Services (BCWS). The operation collects and processes residential and commercial garbage, recyclables, green waste, and organics.
At one time, the operation’s old screens were missing approximately 90 PET bottles and 60 aluminum cans per minute with 30 more PET bottles and 30 aluminum cans per minute buried under materials.
That was lost revenue, points out Jeff Nabhan, BCWS SMaRT Station Facilities Manager. CP Group was chosen to retrofit the MRF in early 2015, using the existing footprint as the small SMaRT Station offered no room for expansion. The system retrofit consists of the installation of two new CPScreens on the MSW line for the separation of 2D paper, films, and residue from 3D containers and bulky waste.
A new MSS CIRRUS optical sorter was installed on the container line for the identification and recovery of PET, HDPE, and other #3–7 material. One of the two eddy current separators was moved from the MSW line to the residential container line. An additional five conveyors were removed.
On the MSW line, the new CPScreens have increased the separation of the 2D material (paper and plastic) from the 3D material (aluminum cans, PET, HDPE), making it significantly easier for sorters to recover material, says Nabhan.
Nabhan notes the retrofitted system dramatically increased recovery rates while maintaining material quality.
After the retrofit, while doing belt checks, BCWS found an average of only 2.5 PET bottles and 1 aluminum can per minute being missed, in contrast to the 120 PET bottles and 90 aluminum cans being missed per minute prior to the retrofit, with those numbers expected to improve.
With the custom-designed solution, new equipment, and new controls, BCWS achieved its retrofit objectives, including:
- 98.8% recovery of previously missed aluminum cans
- 97.9% recovery of previously missed PET
- 65% increase in organics recovery
- reduction in landfill and shipping costs
- increase in total value of recyclables and improvement in system control
Schneider says the CP Group designs systems for MSW operations that are based on their materials stream, diversion goals, space availability, and budget. How a system is designed figures into its overall operation efficiency.
Green Machine system efficiencies depend on proprietary screening technologies, automatic optical sorters, and typical magnetics producing a 60 TPH throughput with as few as 11 total force with 30% + recyclable material diversion rates, says Lindemann. “We find that to be a sweet spot where clean recyclables are collected and solid waste operations’ overall investment and operating costs reach maximum profitability,” he adds.
Machine size is a driving factor for efficient design, Everhart points out, adding there is now available a wider variety of sizes that meet MSW operational needs. “We now make units in five different sizes and a couple of different lengths as well to be able to accommodate whatever the system needs in that particular place,” he says. “The major change layout-wise is where in the past, an MSW operation may have had one or two of a particular unit, but it was very oversized for that particular area. Now we can apply the right-sized machine for the right area because we’ve got the flexibility to do that.”
Addressing how a system design figures into overall operational efficiency, Schneider points out that technology for processing mixed waste has “greatly improved in recent years, and will continue to do so with research and development.” He adds, “With modern MSW waste processing technology, there are limited marketability issues with plastics and metals.”
Thus, the primary focus and concern of MSW processing is fiber quality, he continues. “Clean fiber recovery can be challenging, yet it is feasible to achieve end-market specifications. Profitable fiber recovery requires additional equipment and additional sorting. While some yield loss is inevitable, it is offset by the additional volume. Organics solutions are ongoing and continue to develop.”