In a lithium battery recycling line, the plastic fraction — separator film, casing flakes and insulation — is one of the lightest but most awkward materials to handle. After the batteries are crushed and separated, this material has to travel from the breaking and separation section to a briquetting station or storage silo. Moving it by hand is slow and labor-intensive; belt or screw conveyors struggle with film that tangles and dust that escapes. A plastic pneumatic conveying system moves the material through enclosed pipelines using air, keeping the line clean, the material intact and the process continuous. The catch is that a system designed without care will block, wear out or waste energy. Here is how to design one properly for a battery recycling line.
Step 1: Understand the material you are moving
Design starts with the material, not the pipe. The plastic coming out of lithium battery crushing and separation is rarely uniform. You will typically be handling:
- Separator film — thin, light and prone to tangling or floating in the airstream
- Casing and shell flakes — irregularly shaped, from a few millimeters to a few centimeters across
- Insulation and label fragments — mixed sizes, sometimes carrying traces of metal or dust
Before any calculation, collect samples and measure four properties:
- Particle size and shape — jagged flakes catch on bends far more easily than round pellets, so the system must be designed for the worst case, not the average
- Bulk density — lightweight plastic needs enough air velocity to stay suspended, but not so much that it degrades
- Moisture content — damp film clumps and sticks to pipe walls, so a dry process environment is important
- Abrasiveness — plastic itself is gentle on pipes, but any metal contamination from the shredding step accelerates wear at bends
Step 2: Choose the conveying mode
Pneumatic conveying comes in two main forms, and the choice shapes everything downstream:
- Dilute phase — material is suspended in a fast airstream of roughly 15–30 m/s at low pressure. It is simple, low-cost and ideal for lightweight, non-abrasive materials such as battery plastic film and flakes. This is the standard choice for plastic conveying in battery recycling.
- Dense phase — material moves in slow slugs at roughly 2–8 m/s under higher pressure. It is gentler and uses less energy per tonne, but it suits heavy, abrasive or fragile materials rather than light plastic film.
For plastic from a battery recycling line, dilute phase is almost always the right starting point. It keeps the film suspended, handles short-to-medium distances well and is easy to integrate with the rest of the line.
Step 3: Size the system
Once the material and conveying mode are fixed, three numbers matter most:
- Air velocity — for plastic flakes, around 20 m/s is a safe starting point: fast enough to keep the material suspended, slow enough to avoid excessive pipe wear and material degradation.
- Pipe diameter — the diameter must match the throughput you need to move. A common approach is to size the pipe so that the air volume at the chosen velocity comfortably carries the required kilograms per hour, then confirm the figure with a supplier who can run a simulation. Undersized pipes create bottlenecks; oversized pipes waste energy.
- Blower power — the blower must overcome the pressure ｄｒｏｐ created by pipe length, bends and vertical lift. A variable frequency drive (VFD) lets you adjust speed to demand, which cuts energy use during low-production periods.
Step 4: Lay out the pipeline
The layout decides whether the system runs for years or jams every week. Follow these rules:
- Keep it simple — every bend is a potential blockage point and a wear point. Use long-radius elbows rather than sharp 90-degree turns wherever possible.
- Avoid long vertical rises — vertical sections are magnets for blockages with light film. If a lift is unavoidable, keep it short and support it properly.
- Plan for expansion — if the line will grow from 500 kg/h to 2,000 kg/h, size the pipe and blower for the future capacity now. Oversizing a blower by a small margin today is far cheaper than replacing it later.
- Leave access for maintenance — install access hatches near common trouble spots so blockages can be cleared quickly.
Step 5: Integrate dust collection and air pollution control
A pneumatic system is enclosed, but the air that carries the plastic still has to go somewhere. At the discharge end, a cyclone separator drops the material out of the airstream, and a bag filter captures fine dust before the air is released. In a battery recycling plant, this discharge air should be tied into the plant’s air pollution control system so that dust and any volatile compounds stay well within emission limits. Getting this integration right protects operators and keeps the plant compliant.
Step 6: Plan for safety
Plastic dust is combustible, and a pneumatic system can build up static charge as material rubs against the pipe. Three measures are non-negotiable:
- Ground all conductive components to prevent static buildup that could ignite dust
- Install pressure relief valves on lines and silos so a blockage cannot cause a dangerous pressure spike
- Choose pipe materials that are compatible with the process — avoid reactive metals where lithium dust may be present
Common design mistakes to avoid
- Designing for the average material instead of the worst case — one day the line processes clean casing flakes, the next it handles film with metal fragments. Size for the toughest condition.
- Underestimating bends — each sharp 90-degree bend adds resistance equivalent to several meters of straight pipe and slows the airstream, encouraging settlement.
- Skipping the filter — a cyclone alone will not catch fine dust. Without a bag filter, dust damages the blower and escapes into the working environment.
- Ignoring moisture — damp plastic clumps and blocks the line. Keep the conveying air dry and the process environment stable.
Designing with a partner who knows battery recycling
A plastic pneumatic conveying system is not an off-the-shelf product; it is a designed subsystem that must match the rest of the battery recycling line. That is why working with a supplier who understands the whole process matters. San Lan Technologies, a manufacturer of e-waste recycling machinery, supplies plastic pneumatic conveying system equipment designed to collect plastic film from lithium battery crushing and separation and feed it directly into a plastic hydraulic briquetter, where the film is pressed into dense blocks with a volume compression ratio of 10:1. The conveying system, the briquetter and the li battery recycling equipment are engineered as one integrated line, so the plastic fraction flows continuously from the separator to a compact, stackable product.
When you design your system, start with the material, choose the right conveying mode, size it for growth, and integrate it with the plant’s dust control and safety systems. Do that, and the plastic fraction stops being a handling headache and becomes a clean, saleable output of your battery recycling line.
