How does Butler-MacDonald perform the separations?
In plastics recycling, many types of plastic separation techniques and plastic separation equipment can be used. Which technology to use will depend greatly upon the outcome you want to achieve and the purity required. Knowing which to use and where to use it is often a greater value than owning the equipment. We view it as though you are not compensating us to own the equipment; you are engaging us to know how to use it and get the end result required. So we never get into specifics about the exact means and methods or chain of events we go through to get the desired end product.
We make it simple for our customers. Rather than our customers worrying about all the operational characteristics and expense of owning these technologies, we do that for you. As a result, Butler-MacDonald plant is flexible in how we link technology together which allows us to process a wide variety of polymers rather than be focused on just few. Though not exhaustive, the following is a list of technologies that can be used to recycle plastics:
- Granulator or Granulation - A process of reducing the size of parts or plastics to a size desired. Like these other technologies, Butler-MacDonald possesses many forms of granulation.
- Shredder or Shredding - The process of bulk size reduction to enable other systems to accept the material.
- Sink Float - A simple process of floating materials on water while other are allowed to sink.The density of an object determines whether it will float or sink in water.
- Density Separation - Multiple forms of density separation can be used to separate different plastics by their inherent weight. Sink Float – for example - is a form of density separation.
- Electrostatics - Electrostatic charges are imparted upon particles to attract or repel differently charged material thereby separating them from the particle mixture.
- Aspiration - Introduction of a counter air stream thereby causing finer and lighter density particles to be moved one direction over the heavier particles.
- Zig Zag Separator - A different means of achieving aspiration but material bounces from side to side in chute as it falls.
- Gravity Separator - A system that utilizes three essential elements of a separation system - air flow, speed of vibration, and the deck's differential action allowing heavy materials to be separated from light materials producing two or more fractions.
- Destoner - Similar function and outcome to that of the Gravity Separator but produces only two fractions, a light and heavy fraction.
- Cyclone Separator and Hydrocyclone Separator - Both of these cyclones are used to separate solids or size materials aided by the media used within each device. Each device must be carefully selected for the outcome desired.
- NIR Separator or Near Infrared Spectroscopy - By using near-infrared (NIR) sensors in compliance with extremely fast identification algorithms, these machines allows detection of differences in plastics based upon light transmission and reflectance. Typically pulsing air jets remove the fraction targeted from the mix. The failure of the technology can occur when the color of the plastic that is subjected to sensor identification is a dark color or of a small size. In these instances identification can fail. Pellet sized particles are almost impossible to identify.
- Laser Separator or Laser Spectroscopy - Based on high-speed laser spectroscopy: it identifies material by using the opto-electronic spectrum. It has the advantage over NIR in that it can see smaller particles (with claims down to 0.7mm) and also can identify dark materials with some level of precision. Laser based units suffer in different ways than do NIR machines. Laser has not demonstrated ability to ID differences in polyolefins very well and also in many cases is not currently fast enough for its sensors to identify pellet sized material.
- RGB Separator or Color Separation - There are multiple means if identifying contamination based upon differences in color, transparency, reflectance and light value. Some machines convert what you see in to gray scale values, others can see color differences by RGB values and color spectrum. With a properly setup machine and the right machine choice, defects can be removed from plastic waste streams by a blast of air. The level and type of contamination greatly affects the outcome.
- Melt Filtration - Where hot plastic is allowed to pass through a filter that can be made up of various sized screens, drums or discs that have pores or holes in the surface. Laser filters are used to remove non-abrasive contaminants that are present in higher amounts than can be handles with screen base filter systems. Laser based systems are not effective in removing any contaminant smaller than roughly 70 microns. Screen based systems can deal with contaminations smaller than 70 microns but cannot work well with high contamination levels that exceed 0.5%. Neither technology works very well with highly flexible materials such as silicones, gels or foams.
- Metal Removal and Metal Detection - These systems come in various capabilities, styles and the application of how they are used is the difference between success and failure. Metal removal is a key ability of Butler-MacDonald and one where many companies seek out our expertise in removing it from the plastic material.
- Plastic Blending and Plastic Compounding - A process whereby colorant and additives are added to one to many plastic materials to change the appearance or physical properties of the final product produced.
- Pelletizing or Pelletizer- Plastic is extruded through holes in a dye to form strands that are cut in to small pellets suitable for direct use into manufacturing.
- Extrusion - Single and twin screw extruders are used to perform different functions based upon the needs required.
- Screening and Fines Removal - Where sieves and or punch plates are used to allow material to pass through or stay on top of one to multiple layers to achieve a size desired.