Q:How to deal with galvanized coil waste?
A:The recycled galvanized coil waste mainly comes from automobile manufacturing waste, scrapped vehicle dismantling parts, industrial scraps, etc., and must be classified according to material (such as hot-dip galvanizing, electrogalvanizing), coating thickness, impurity content, etc. to avoid mixing of different types of waste and affecting recycling efficiency.
Remove mixed non-metallic impurities (such as plastic, rubber, paint, oil, etc.), common methods include magnetic separation, screening, manual sorting or laser sorting.
Q:How to treat the surface of galvanized coil?
A:Alkaline, solvent or ultrasonic cleaning is used to remove surface oil, lubricants and other organic contaminants to prevent the generation of harmful gases (such as hydrogen chloride) or the impact on metal purity during subsequent processing. ◦ For painted or coated galvanized coils, it may be necessary to remove the coating through heat treatment (low temperature baking) or chemical stripping.
Q:How many methods are there to recycle galvanized coils?
A:Electrolysis method
Immerse the galvanized waste in an electrolyte (such as zinc sulfate solution), dissolve the zinc layer into zinc ions through electrolysis, and reduce it to metallic zinc (purity can reach 99.9%) at the cathode. The iron matrix is used as the anode for further recovery of iron elements after dissolution.
Thermal reduction method (high temperature melting)
Heat the waste to above the boiling point of zinc (907℃), evaporate the zinc coating to form zinc vapor, then condense and collect metallic zinc, and the iron matrix forms molten iron liquid that can be cast into steel ingots.
Mechanical stripping method
The zinc layer is physically stripped by grinding, sandblasting or high-pressure water jet, and the separated zinc powder and iron filings are collected separately.
Q:What are the advantages and disadvantages of the above three methods?
A:Electrolysis method: high zinc recovery rate, simultaneous iron recovery, low environmental pollution; Disadvantages: high energy consumption, need to treat electrolyte wastewater.
Thermal reduction method: Advantages: high processing efficiency, suitable for large-scale recycling; Disadvantages: high temperature and high energy consumption, and the need for supporting waste gas treatment equipment (to prevent zinc vapor and smoke pollution).
Mechanical stripping method: Advantages: simple process, no chemical pollution; Disadvantages: incomplete stripping of the zinc layer, low metal recovery rate, suitable for waste with thicker coatings.
Q:How to deal with waste during the recycling of galvanized coils?
A:Non-recyclable residues (such as ceramic and glass fragments) or purified sludge need to be classified and disposed of as hazardous waste (such as zinc-containing sludge) or general industrial waste. Some of them can be used in the production of building materials (such as bricks and paving materials).