Pyrometallurgical PGM Recovery Using Silicon-Free Slag
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Solution Overview
Problem
Current methods for recovering platinum group metals from spent alumina-based catalysts face challenges such as high wet reagent consumption, large wastewater discharge, heavy metal pollution from pyrometallurgical processes, and low leaching rates due to ferrosilicon alloy formation in high-temperature smelting, leading to environmental concerns and increased costs.
Innovation Solution
A pyrometallurgical method using a silicon-free slag system of CaO-Al2O3-Fe2O3-B2O3, where iron traps platinum group metals, avoiding heavy metal contamination and ferrosilicon alloy formation, and achieving a lower melting point slag phase to enhance recovery efficiency and reduce slag quantity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional CaO-MgO-Al2O3-SiO2 slag type is used for pyrometallurgical smelting, then platinum group metals can be collected through iron collection, but ferrosilicon alloys are produced resulting in low recovery rates
Solution Approach 1:
The invention removes silicon from the slag system composition, using a silicon-free slag system of CaO-Al2O3-Fe2O3-B2O3 instead of conventional CaO-MgO-Al2O3-SiO2 slag. This extraction of silicon prevents ferrosilicon alloy formation and enables high recovery rates of platinum group metals through iron collection
Solution Approach 2:
The invention changes the chemical composition parameters of the slag system by eliminating SiO2 and using B2O3 as a substitute flux. This parameter change transforms the slag properties to prevent ferrosilicon alloy formation while maintaining effective platinum group metals collection
2Reliability
If hydrometallurgical process is used to dissolve PGMs in acidic environment, then separation of PGMs from support is achieved, but large amounts of sulfuric acid are consumed and waste water is large
Solution Approach 1:
The invention replaces the hydrometallurgical chemical dissolution process with a pyrometallurgical process. Instead of using acidic environments and chemical reagents to dissolve and separate PGMs, the invention uses high-temperature smelting with iron collection in a silicon-free slag system, eliminating the need for large amounts of acid and producing minimal waste water
Solution Approach 2:
The invention changes the fundamental process parameters from low-temperature chemical dissolution to high-temperature thermal processing. This parameter change transforms the separation mechanism from chemical dissolution to thermal smelting and metal collection, fundamentally reducing chemical reagent consumption and waste water generation
3Reliability
If oxidative leaching is used to dissolve platinum group metals, then PGMs can be recovered, but toxic gases such as Cl2 and NOx are produced causing environmental pollution
Solution Approach 1:
The invention replaces oxidative leaching with a pyrometallurgical smelting process. Instead of using oxidizing agents in acidic environments that produce toxic gases, the invention uses controlled oxygen partial pressure during high-temperature smelting to collect PGMs through iron, eliminating the production of Cl2 and NOx gases
Solution Approach 2:
The invention creates a controlled atmosphere during smelting by maintaining oxygen partial pressure below 10^-3 atm. This controlled low-oxygen environment prevents the formation of toxic gases while still allowing effective PGM collection through iron, providing a cleaner alternative to oxidative leaching
4Productivity
If high-temperature smelting is used to collect PGMs with iron, then collection efficiency is improved, but ferrosilicon alloy formation reduces subsequent separation efficiency
Solution Approach 1:
The invention extracts silicon from the slag system to prevent ferrosilicon alloy formation. By using a silicon-free CaO-Al2O3-Fe2O3-B2O3 slag system, the invention ensures that iron collects PGMs without forming difficult-to-separate ferrosilicon alloys, maintaining high collection efficiency while enabling easy separation
Solution Approach 2:
The invention creates local chemical environment control by using a silicon-free slag composition. This local quality change in the slag system ensures that iron interacts with PGMs without simultaneous silicon presence, preventing ferrosilicon alloy formation and maintaining easy separability while preserving collection efficiency
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
This method achieves high platinum group metal recovery rates (up to 99.7%) with reduced environmental impact and lower costs, utilizing the CaO-Al2O3-Fe2O3-B2O3 slag system to facilitate efficient separation and resource utilization of waste slag for producing high-strength cement.
Implementation Method 1
The CaO-Al2O3 phase diagram undergoes a eutectic reaction around 1370℃
Implementation Method 2
the collecting process produces SO2 and nickel is a toxic heavy metal with potential environmental risk
Data Source
Figure 1
AI summary
The present application relates to the technical field of platinum group metals (PGMs) recovery, providing a method for pyrometallurgicalconcentration of platinum group metalsfrom spent alumina-based catalysts. For an Al2O3 supported spent catalyst, a method for pyrogenic iron collection of platinum group metals is disclosed, using a CaO-Al2O3-Fe2O3-B2O3 slag system to achieve highly efficient concentration of platinum group metals via slag iron separation, avoiding CaO-MgO-Al2O3-SiO2slag systemfrom producing poorly soluble platinum group metals-ferrosilicon alloys, increasing recovery of platinum group metals. The present application is characterized by low slag content, silicon-free Fe-PGMs alloy, high recovery efficiency and low cost, and is suitable for industrial production.