Every other screening machine separates by size. An air separator does something different, and that is exactly why it is indispensable: it separates by density. Two objects of the same size, a plastic bag and a piece of brick, leave on different streams, which no screen in the world can achieve.
The principle is the law of settling in air. A controlled air stream passes through the falling material. Anything light with a large surface, paper, bags, film, textiles, is carried upward or thrown far horizontally. Anything heavy and compact, glass, metal, wood, stone, cannot be supported by the stream and drops immediately. See the full range of waste sorting equipment and where each machine sits in the flow.
Key Advantages of an Air Separator
• It separates what no screen can, an air separator splits two objects of the same size but different weight, which is impossible on a size criterion.
• It produces the combustible fraction, the light fraction it yields is exactly the high calorific material from which RDF alternative fuel is made, so the separator creates a sellable product.
• It protects the heavy equipment, by pulling stone, glass and metal out of the light flow, the shredders and presses downstream no longer receive the objects that destroy their knives.
• Adjustable airflow, the air volume is tuned to the material composition, so the cut point between light and heavy sits exactly where you need it.
• Three system variants, positive pressure, negative pressure or combined, chosen from dust requirements, site conditions and material.
• No parts that dull, separation is done with air rather than mechanically, so there are no knives or screens in contact with abrasive material.
Technical Specifications, Air Separator
| Parameter | 0.8 m drum | 1.2 m drum | 1.6 m drum |
|---|---|---|---|
| Drum width (mm) | 800 | 1200 | 1600 |
| Input conveyor width (mm) | 1000 | 1200 | 1400 |
| Airflow | Adjustable | Adjustable | Adjustable |
| System type | Positive / negative / combined | Positive / negative / combined | Positive / negative / combined |
| Air circuit | Closed, with recirculation | Closed, with recirculation | Closed, with recirculation |
| Output fractions | Light and heavy | Light and heavy | Light and heavy |
The drum widths correspond to published manufacturer configurations, and the input conveyor widths to standard market ranges. Real throughput depends heavily on material density and moisture, so it is set at configuration.
Applications for Air Separation
• Municipal waste sorting plants, separating the light recyclable fraction from the heavy inert one, as the central stage of the line.
• Alternative fuel production, concentrating the high calorific fraction for RDF and SRF.
• Construction and demolition waste, pulling insulation, plastic and paper out of heavy rubble.
• Plastic recycling, removing labels, dust and light particles from washed flakes.
• Composting, eliminating light contaminants, especially plastic film, from organic waste.
• Wood recycling, separating light chip from stone, soil and metal parts.
How It Works
Material is delivered by a feed conveyor and released into a zone where a fan creates a controlled air stream. Here the settling law takes over: every object has its own falling speed, determined by the ratio between its weight and the surface it presents to the air. Objects with a large surface and low weight, paper, film, textiles, have a low falling speed, so the stream supports them and carries them upward or far horizontally, into the expansion chamber. There the air slows, the material drops out of the stream onto the light fraction conveyor, and the air returns through the recirculation duct to the fan. Heavy, compact objects, glass, metal, stone, have a high falling speed, the stream cannot support them, so they drop immediately behind the discharge point onto the heavy fraction conveyor. An internal drum helps guide the light material. By adjusting the air volume, you move the threshold between the two fractions exactly where you want it.
Selection Guide
Drum width is chosen from line throughput, and the system type from site conditions. Negative pressure, that is suction, keeps dust under control and is preferred in enclosed halls or where environmental requirements are strict. Positive pressure, that is blowing, is simpler and cheaper. The combined system offers the best separation accuracy but is also the most complex. One thing is essential: an air separator gives good results only on already screened material with relatively uniform particle size. Put straight onto mixed, unscreened waste, its performance drops dramatically, because a large light object and a small heavy one can behave identically in the air stream.
Frequently Asked Questions
What is the difference between an air separator and a ballistic separator?
Both separate on something other than size, but on different criteria. An air separator separates strictly by density, using air. A ballistic separator separates by shape, flat versus rolling, using the mechanical motion of paddles. Many plants use both, one after the other, because they make complementary cuts in the flow.
Positive or negative pressure, which should I choose?
Negative pressure, that is suction, controls dust far better and is recommended in enclosed halls or where you have strict environmental requirements. Positive pressure is simpler, cheaper and suitable where ventilation is good. The combined system gives the best separation accuracy, at higher cost and complexity.
Does the material have to be screened first?
Yes, it is effectively mandatory. An air separator works well on material with uniform particle size. On mixed waste, a large light object and a small heavy one can have the same falling speed, so they end up together and the separation becomes meaningless. That is why the air separator is placed after the screen, not before it.
Is material lost into the air?
No, the air circuit is closed. The air that carried the light fraction passes through the expansion chamber, where the material drops out, then returns through the recirculation duct to the fan. A filtration system is also fitted for the fine dust that does not settle in the expansion chamber.
Is the equipment supplied new?
Yes. We supply new units only, made to order for your application, with complete technical documentation.
What maintenance does it need?
Checking and cleaning the fan and the air ducts, where dust builds up, inspecting the guide drum, checking the air circuit seals and periodically replacing the filters. With no parts that cut or grind, mechanical wear is minimal.
Why URSTAG?
URSTAG is a premium brand of recycling equipment, with over 15 years of experience. You don't just get a machine, you get a solution engineered by specialists, built from top-tier components and backed by a team that supports you from design through commissioning.
• European engineering, every machine and every complete line is designed by our engineering teams in Europe, with a focus on reliability, safety and energy efficiency.
• Premium components, we build on motors and automation from industry leaders: Siemens, Schneider Electric, ABB, WEG, SEW-Eurodrive, NORD Drivesystems and Bonfiglioli.
• Over 15 years of experience, we know how materials and machines behave in real-world operation, and we configure each solution for your flow and volume.
• New equipment, configured for you, we supply new units, made to order for your application, with complete technical documentation.
• Delivery, installation and training included, we handle transport, commissioning and operator training, with support throughout the equipment's life.
As a premium brand, URSTAG relies on European engineering, top-tier components and experience. You choose a partner that supports your production long term, with equipment built to run reliably in demanding industrial environments.
