Separation and Sorting Technology

Magnetic separation

Magnetic separation is the process of 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 mainly used 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 that is 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 its 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.

Waste screening systems

Screening is the most standard form of separating solid waste, depending on their size by the use of one or more screening surfaces. Screening has a number of 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 forms of vibrating screens are the most commonly used screens nowadays.

Selection of screening systems

Screening systems come in many shapes and sizes and provide a variety of sorting solutions. Some of the 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 component.
  • 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 such as space and height access, noise and environmental limitations.

Sensor-based sorting technology

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 colour, x-ray or near-infrared sensors are increasingly more common in the industry and therefore accepted as the standard process. Mining technologies, like sensor-based sorting, have the potential to 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 prior to the application of fine comminution and chemical processing techniques. The goals are to remove waste before it enters production and recover the usable ore.

Robotic sorting technology

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 are counting on robots to sort recycling.

How does robotic sorting work?

Cameras and high-tech computer systems that are trained to recognize specific objects will the robotic components over conveyor belts to reach their target. Sensors that are attached to the arms are able to detect and interact with objects such as 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 dexterity and accuracy
• Improved knowledge
• Advantages of AI
• Quality control

X-Ray sorting technology

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 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 properties of the material.

X-ray methods can be divided into three categories:

1. The X-ray radiation sorting method is a method of sorting materials by using characteristic spectral lines generated by excitation after receiving X-ray irradiation.
2. 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.
3. The X-ray absorption separation method is to separate different materials by different X-ray absorption coefficients of a certain wavelength and energy.

Induction sorting technology

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%.

Colour sorting technology

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

Colour sorters are mostly used in sorting grain (agricultural products). The rice sorting industry is the first big market. Colour 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.

Colour sorting in the recycling industry

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

Near infra-red (NIR) sorting technology

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 in the waste industry to recover materials of value from streams.

The minerals industry offers various fields of application for NIR spectroscopy. NIR spectroscopy can be implemented as an offline laboratory analysis as well as for 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, but also in 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) sorting technology

Laser-Induced Breakdown Spectroscopy (LIBS), is a laser-based analytical, identification and detection technique that has been proposed for numerous applications, as 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 in order 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 analysing light metals
• Aluminium is also considered to be easier to sort with LIBS technology.