Sorting by Category
Complete galvanized elbows are sent directly into the crushing line. Elbows with flange assemblies are separated by hydraulic shears, and elbows with threaded interfaces are processed by flame cutting to remove the threaded section. Sorting at the start ensures each material stream is processed efficiently.
Surface Cleaning
Physical cleaning uses dry ice blasting with carbon dioxide particles at about minus 78 degrees C to remove oil and coatings. Chemical cleaning uses a neutral cleaning agent at pH 6.5 to 7.5 with cyclic spraying. The target is residual pollutants below 50 mg per kilogram, meeting environmental compliance requirements for recycled materials.
Zinc Coating Recovery
Mechanical stripping uses a high-pressure water jet at about 250 MPa to strip the zinc layer, which is then crushed into zinc slag suitable as welding wire raw material with zinc content of 98 percent or more. Cold spray regeneration applies recycled zinc powder with high-pressure gas to directly spray-repair old elbows, achieving bonding strength above 30 MPa.
Development Trends
Short-process regeneration develops in-situ repair technology for zinc layers to reduce remelting energy consumption. Digital traceability records the elbow lifecycle data to optimize recycling solutions. Urban mining establishes regional recycling centers with a radiation radius of about 50 km to concentrate material flows.
Conversion of Waste Residue into Resources
Acid-leached iron slag undergoes magnetic separation to recover iron for steelmaking, used as converter coolant. Zinc distillation residue is processed to extract indium and cadmium above 99 percent purity as scattered metal raw materials. Neutralized sludge is sintered to make ceramsite used as building material.
Frequently Asked Questions
Q: How are galvanized elbows sorted for recycling?
Complete elbows go directly to crushing, flanged elbows are separated by hydraulic shears, and threaded elbows by flame cutting.
Q: How is the surface cleaned?
By dry ice blasting or neutral chemical cleaning to below 50 mg/kg residual pollutants.
Q: How is zinc recovered from the coating?
High-pressure water jet stripping at about 250 MPa crushes the zinc into slag with 98 percent or more zinc content.
Q: What is cold spray regeneration?
Recycled zinc powder is sprayed with high-pressure gas onto old elbows, achieving bonding strength above 30 MPa.
Q: What resources come from the residue?
Iron from acid-leached slag, indium and cadmium from distillation residue, and ceramsite from neutralized sludge.
Q: Why establish regional recycling centers?
Concentrating material within about 50 km improves logistics efficiency and recycling economics.