Precious Metal Enrichment from PCB Ash via Chlorination
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Solution Overview
Problem
Current methods for recovering copper and other valuable metals from printed circuit board incineration ash are inefficient, leading to low recovery rates and environmental pollution, with existing processes failing to comprehensively recover precious metals and causing secondary pollution due to tail liquid discharge.
Innovation Solution
A method involving slurry aging with concentrated sulfuric acid, followed by primary and secondary roasting, water leaching, and chlorination enrichment using calcium chloride, sodium chloride, and hydrochloric acid to separate and recover copper, zinc, lead, and bromine, with lead displacement and precipitation processes to achieve high recovery rates and eliminate secondary wastewater.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If traditional pyrogenic treatment is used for copper recovery from ash, then copper can be recovered, but the comprehensive recovery rate of valuable metals is low and impurities accumulate
Solution Approach 1:
The patent divides the recovery process into distinct segments: pyrogenic treatment for copper recovery, followed by wet treatment for comprehensive valuable metal recovery. This segmentation allows each process to target specific metals optimally, preventing impurity accumulation while maximizing overall recovery rates of copper, zinc, lead, and precious metals.
Solution Approach 2:
The patent introduces an intermediary wet treatment process between pyrogenic treatment and final metal recovery. This intermediary step uses leaching and precipitation to remove impurities and recover additional valuable metals, acting as a bridge that enhances overall recovery efficiency without compromising copper recovery.
2Quantity of substance
If pyrogenic treatment is used for ash processing, then copper can be recovered, but working conditions are poor and environmental pressure increases
Solution Approach 1:
The patent converts the harmful brominated flame retardant residues and impurities generated during pyrogenic treatment into beneficial recovery targets. The wet treatment process specifically targets these impurities for recovery as zinc, lead, and precious metals, transforming environmental hazards into valuable products and eliminating tail liquid discharge.
Solution Approach 2:
The patent changes the treatment parameters from purely high-temperature pyrogenic conditions to a combined approach including wet chemical treatment at lower temperatures. This parameter change reduces environmental pressure and improves working conditions while maintaining copper recovery efficiency and adding valuable metal recovery capabilities.
3Quantity of substance
If existing recovery processes are used, then some metals can be recovered, but tail liquid discharge causes secondary pollution
Solution Approach 1:
The patent implements comprehensive recovery of all valuable metals including copper, zinc, lead, and precious metals through the combined pyrogenic and wet treatment processes. By recovering these metals from what would otherwise be tail liquid, the process eliminates secondary pollution while maximizing metal recovery rates.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method achieves high recovery rates of 98.7% for bromine, 99.2% for copper, 99.1% for lead, and 99.2% for precious metals, while recycling tail liquids and reducing environmental impact by avoiding secondary pollution.
Implementation Method 1
slurry aging with concentrated sulfuric acid
Implementation Method 2
decomposition using self-heating smelting
Implementation Method 3
volatile lead and zinc are volatilized and enriched under a reducing atmosphere
Implementation Method 4
pyrolysis in molten pool under the high temperature
Implementation Method 5
water leaching and enrichment to generate a water leaching slag rich in precious metals, and a water leaching solution
Implementation Method 6
chlorination enrichment using calcium chloride, sodium chloride, and hydrochloric acid to separate and recover copper, zinc, lead, and bromine
Implementation Method 7
lead displacement and precipitation processes
Implementation Method 8
precipitation of zinc, and comprehensive treatment of primary and secondary flue gas
Data Source
AI summary
The invention relates to the field of comprehensive recovery of valuable elements such as bromine, base metal and precious metal from incineration ash, especially relates to a method for enriching precious metals from printed circuit board incineration ash by bath smelting-chlorination circulation process. The process mainly comprises pretreatment of the printed circuit board Incineration ash and circulation-chlorination enrichment process for precious metals. The crude copper, crude zinc sulfate, bromine, lead chloride and precious metal enriched slag are obtained. Compared with the traditional process, it realizes the cycle enrichment of precious metals as well as avoids the loss of valuable metals and secondary pollution caused by tail liquid discharge.