Air is one of the most effective ways to isolate and transport materials. Air is an ideal separation and transportation medium for any number of materials due to fluid dynamics and gravity laws. Consider a dandelion's seed head: all it takes is a light breeze to disperse the seed and create the next generation, much to the chagrin of lawn lovers everywhere. Air has been used to isolate materials of various densities since ancient times. Winnowing is the age-old practice of throwing the grain into the air and letting the wind distinguish the lighter chaff from the heavier grain.
Air separation has been used in some way or another since prehistory and continues to be used today. Many companies use air separation and air conveyance systems equipment for sorting, separation, and processing because of their ability to distinguish materials based on their weight or density.
The basic concepts guiding this method are now being used to isolate and express materials in MRFs more frequently. Air separation and pneumatic conveyance can help to increase separation effectiveness, automate processes, improve material quality, and create a healthier, safer working environment. Air separation devices and systems from unrelated industries have been updated and optimized for use in the MRF set by equipment manufacturers.
As a result, equipment and systems for air separation and pneumatic conveying have been explicitly designed for use in MRFs to distinguish lighter from heavier materials. Reduced workforce for hand sorting, increased sorting system capability, reduced equipment wear and tore associated with conventional mechanical separating systems. Reduced staff exposure to airborne pollutants is just a few of the advantages of these systems.
Let's look at a few of these systems to see how they function and why they're becoming increasingly common in the recycling industry.
Air separation systems are used to distinguish between two types of materials based on their density and aerodynamic properties. They're often used to separate and catch material from the conveyance air stream, which is then processed or disposed of. In both cases, the target material is influenced to travel in the desired direction using the concept of terminal velocity.
In fluid mechanics, terminal velocity is defined as "the velocity with which a body moves relative to a fluid when the resultant force acting on it (due to friction, gravity, and other factors) is zero," according to the sixth edition of the McGraw-Hill Dictionary of Scientific & Technical Terms. The fluid in air separation systems with elutriation is air with a specific density, and the forces are gravity and the pressure exerted by a flowing air stream, which is measured in cubic feet per minute, or CFM. You can overcome gravity over a certain distance by varying the pressure of a focused stream of air and achieve the optimal separation of materials of various densities by varying the pressure of a focused stream of air.
This concept is used in optical sorting equipment to distinguish between different containers, such as metal cans and plastic bottles, using a burst of compressed air. A glass cleanup device is another popular application. This is a secondary method in which broken glass is dropped into a stream of upward-moving air at a high enough velocity to eliminate light fraction materials, including paper and plastic labels, resulting in less pollution and higher product value.
We are now seeing a more advanced airwash system that can automatically isolate materials of different densities in two, three, or four phases. Although the separation efficiency isn't quite 100% and usually necessitates some manual sorting of the products, the result is a more productive and effective way to distinguish large quantities of light fraction materials from waste. With China's Operation Green Fence program, which allows cleaner recyclable bales with fewer pollutants, this is even more essential today.