Metal sorting and recycling is a heavy topic that is vast in scope. It is a mix of chemistry, engineering, physics and logistics. Most have seen a scrapyard where cluttered chunks of car bodies are stacked, bundled for their trip back to the metalworks, often being shipped in giant bales to foreign ports.
There is a difference in the processing of cars and motorcycles, because parts have value aside from scrappage. Aluminum cans are very close to their original form, so processing those is quick. Old buildings, rail tracks, fishing trawlers or construction materials can be hard to transport. Some steels require special facilities. Copper, silver and gold are highly valued for different reasons.
Old tractors, agricultural buildings, and farm machinery are typically collected through scrapyards, auctions, or specialized recyclers. Workers remove non-metallic parts like tires, hoses, wiring, and plastic. The goal is to reduce contamination in the recycling process. This work is labor-intensive.
Items are categorized by metal type (iron, steel, aluminum, etc.) and contaminants (rubber tires, plastic parts, etc.). Heavier metals like cast iron and steel from tractors are a priority since they are dense and valuable. The remaining metal is fed into industrial shredders. They break down large parts into smaller chunks, making them easier to process.
Separation of Metals
Modern recycling uses impressive technologies to sort and purify metals from mixed scrap:
- Magnetic Separation: Tractors and farm equipment often contain high-quality steel alloys that respond well to this. Magnets are used to pull out ferrous metals (iron, steel) from the shredded pile.
- Eddy Current Separation: Non-ferrous metals (like aluminum) are separated using eddy currents. This process uses an electromagnetic field to repel non-ferrous metals, making them jump off the conveyor belt.
- Density Separation: Heavy metals like cast iron sink in water-based or air-based systems, while lighter metals like aluminum float or are blown aside.
- Optical Sorting: Machines use cameras and sensors to identify and sort metals by color or material composition, especially when working with shredded fragments.
- X-Ray or Laser Spectroscopy: Advanced facilities use X-ray fluorescence (XRF) or laser-based tech to analyze the exact alloy composition of metals to sort them more precisely.
- Hand Picking for Legacy Metals: Workers may hand-pick valuable or niche alloys (like manganese steel) that older equipment contains, as these alloys can’t always be identified automatically.
Why Is Old Metal Better?
- Alloy Purity: Older metal often has fewer impurities since older manufacturing processes had more robust quality control for durability.
- Density and Grain Structure: Time and older techniques resulted in metals with denser structures, making them harder and longer-lasting.
- Unique Alloys: Many alloys used in old equipment are no longer produced due to cost or environmental concerns, like nickel-heavy or manganese-rich steels.