Separation and Sorting Technology

Separation and sorting technology innovations in waste handling and recycling operations

If there is one part of the recycling process that is complicated and hard, it is the part of separating and sorting the recyclables. Effective recycling relies on effective and efficient sorting. Separating the different elements found in waste streams is crucial for recovering valuable materials, minimizing the amount of material sent to landfills, and allowing recyclable materials to find a new purpose. There is a wide range of sorting and separating technologies on the market today. This Technology Zone offers an insight into the latest innovations in separation and sorting technology.

Waste separation is the process of separating waste into different elements. Waste sorting can be done manually at the household and collected or automatically separated in materials recovery facilities. Hand sorting was the first method used in the history of waste sorting.

Separating waste is the innovation of traditional waste collection and disposal. With the growing waste production and deterioration of the environment, it becomes the typical focus on achieving garbage utilization and improving the quality of the living environment.

Waste separation is an essential step before the disposal of waste. The valuable waste can be sorted for recycling and reusing through separation, such as plastics, paper, rubber, bottles, glass, etc. Separation of waste for recycling improves the level of resources utilization and reduces the amount of garbage.

Magnetic separation is separating components of mixtures by using different types of magnets to attract magnetic materials. The process that is used for magnetic separation detaches non-magnetic material from those that are magnetic.

Magnetic separation can be used in different environments and markets, so are magnetic separators used primarily for recovering metal from waste or purifying secondary materials by removing metals. But magnetic separators are also used in electromagnetic cranes that separate magnetic material from scraps and unwanted substances. Magnetic separation is also used in the mining and mineral industry and plays a small role in the food and pharmaceutical industry. For example, to remove metal contaminants from product streams.

How is a magnetic separator used in recycling applications?

A magnetic separator consists of a powerful electromagnet placed or suspended from a ceiling or device. Materials can be passed over a tabletop magnetic separator, while suspended magnetic separators often hover over material to remove imperfections. Magnetic separators can also be cylinders that objects pass through.

In the recycling industry, magnets are commonly used to attract ferrous materials, such as tin, iron, steel, and many more. Magnets are found along assembly lines where they will be placed either above or below the conveyor belts to attract said materials or minerals.

Screening is the most standard form of separating solid waste, depending on its size, by using one or more screening surfaces. Screening has several applications in solid waste resources. Screens can be used before or after shredding and after air separation of waste in various applications. Rotary drum screens and various vibrating screens are the most commonly used screens nowadays.

Selection of screening systems

Screening systems come in many shapes and sizes and provide various sorting solutions. Popular screening systems include the screen drum, trommel screens, mobile screens, vibrating screens, and many more.

The following variables affect the decision of selecting the most appropriate screen:

Separation efficiency.
Material specification for screened components.
Location where screening is to be applied.
Characteristics of waste material to be screened and the screen design
Operational characteristics (energy and maintenance requirements, simplicity of operation, reliability, and more.
Site considerations include space and height access, noise, and environmental limitations.

Sensor-based sorting has become more established in recent years, and it’s commonly used in the mining industry. The benefits of automatic sorting using color, x-ray, or near-infrared sensors are increasingly common in the industry and therefore accepted as the standard process. Mining technologies, like sensor-based sorting, can address the problems the industry now faces, such as water shortages, declining ore grades, and increasing environmental regulations.

Usage of sensor-based sorting technology

Sensor-based sorting has been used in the food processing and waste/recycling industries. In recent years, the mining industry has become more common for sensor-based sorting.

Sensor-based sorting is used for particle sizes ranging between 0.5 to 300 mm and is completed before applying fine comminution and chemical processing techniques. The goals are to remove waste before production and recover the usable ore.

Robotic recycling sorting uses artificial intelligence (AI) and robotics to sort plastics, so humans don’t have to. With advanced cameras and technology, these companies count on robots to sort recycling.

How does robotic sorting work?

Cameras and high-tech computer systems trained to recognize specific objects will include the robotic components over conveyor belts to reach their target. Sensors attached to the arms can detect and interact with cans, glass, plastic containers, and any other recyclable items out of the otherwise garbage and place them in their respective bins.

Advantages of robotic recycling include:

Reduced reliance on manual sorters, therefore, more reliable
Increased agility and accuracy
Improved knowledge
Advantages of AI
Quality control

The application of X-rays has also changed every aspect of life, most notably in the mining industry. The application of X-ray separation technology has overturned the traditional methods. X-ray sorting technology enables materials to be separated based on their specific atomic density by recognizing the material beforehand.

The signal recorded by the X-ray sorting method is the content of the selected material, so the sorting process is not affected by other material properties.

X-ray methods can be divided into three categories:

The X-ray radiation sorting method sorts materials by using characteristic spectral lines generated by excitation after receiving X-ray irradiation.
The X-ray-fluorescence sorting method is based on the characteristics of materials that emit photons when they are excited by X-rays to achieve mineral separation.
The X-ray absorption separation method separates different materials by different X-ray absorption coefficients of a specific wavelength and energy.

An induction sorting system (ISS for short) is the perfect addition to magnetic sorting and eddy-current separation for recovering residual metals from a mix of materials and minerals. These systems are especially suitable for stainless steel and composite materials such as cables or circuit boards.

How does an induction sorting system work?

Pre-sorted bulk material is fed on a conveyor belt. Below the conveyor, metal detectors are arranged over the whole width of the belt. The metal detectors are coils with a defined inductance. This inductance is changed if a metal passes by. If metal is recognized, it will be blown out with compressed air. The purity of the sorted materials is up to 90%.

Color sorters (often called optical sorters, digital sorters, or electronic color sorters) are sorting machines used on the production lines in bulk food processing and many other industries. They separate items by their colors, detecting the colors of things that pass before them.

Color sorters are primarily used in sorting grain (agricultural products), and the rice sorting industry is the first big market. Color sorters are also used for the food processing industry, such as coffee, nuts, and oil crops. Colour sorters are also found in the mining industry, more specifically, the diamond industry.

Color sorting in the recycling industry

In the recycling industry, the color sorter can distinguish between colored and colorless PET and HDPE flakes and separate flakes by color. Plastic color separators are used to separate mixed-color plastic flakes or particles, and Plastic-type separators separate plastics of the same color but different materials.

NIR sorting is the industry’s preferred plastics sorting technology because it can accurately identify the many different polymers already in use today. NIR technology is also widely used to recover valuable materials from streams in the waste industry.

The minerals industry offers various fields of application for NIR spectroscopy, and NIR spectroscopy can be implemented as offline laboratory analysis and online process control. In both cases, the well-known characteristics, namely: short analysis time, non-destructive, easy sample preparation, relatively low cost) are the best reasons for using NIR spectroscopy in the minerals industry.

Benefits of NIR

NIR sensors have already been proved to be efficient in the mechanical sorting of plastics in sorting facilities and the mineral industry. They are also an affordable option, as the development of MEMS technology has resulted in very cost-effective NIR solutions.

Laser-Induced Breakdown Spectroscopy (LIBS) is a laser-based analytical, identification, and detection technique that has been proposed for numerous applications, for instance, for the detection of metals (i.e., minerals, metallurgical, environmental, etc.).

LIBS uses a high-focus laser that erodes the surface of the metal. When this happens, the atoms decay and emit light wavelengths. These wavelengths are specific for each element; thus, the type of metal can be determined. LIBS is a minimally destructive method since it does melt a portion of the surface to obtain a result.

Some advantages of the LIBS technology

LIBS can identify types of metal rapidly as well as perform simultaneous multi-element analyses.
There is no need for extra equipment or licensing
LIBS scanners are used to be much more effective at analyzing light metals
Aluminum is also considered to be easier to sort with LIBS technology.