Metal Recovery from Smelting Slag via Volatile Chlorides
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Solution Overview
Problem
Existing methods for recovering metals from metallurgical slag wastes are inefficient due to the stability of these materials, which do not readily release metal constituents, and hydrometallurgical processes are non-selective, leading to complications such as excessive leaching of iron.
Innovation Solution
A process involving heating slag waste materials in a fluidised bed reactor with a gaseous chloride to form volatile metal chlorides, which can then be recovered and further treated to extract the metals, utilizing the lower vaporization temperatures of metal chlorides to reduce energy requirements and optimize recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If hydrometallurgical processes are used to extract metals from slag waste, then metal recovery is achieved, but the process is non-selective and causes excessive leaching of iron
Solution Approach 1:
The invention changes the chemical parameters of the extraction process by using gaseous chlorides instead of aqueous solutions. This parameter change transforms the extraction mechanism from non-selective leaching to selective chlorination, where only specific metals react with the gaseous chloride under controlled conditions, thereby achieving both high productivity and selectivity
Solution Approach 2:
The invention employs gaseous chlorides as strong chemical agents that selectively react with metal constituents in the slag. The gaseous state and high reactivity of chloride gases enable accelerated and selective conversion of target metals into volatile metal chlorides, which can then be separated from non-reactive components like iron, resolving the selectivity issue
2Productivity
If conventional heating methods are used to release metal constituents from slag, then metal recovery is attempted, but the stability of slag prevents effective release
Solution Approach 1:
The invention uses gaseous chlorides as aggressive chemical agents that can penetrate and react with the stable slag matrix. The chloride gases chemically attack the slag structure, converting stable metal compounds into volatile metal chlorides that can be released at lower temperatures, thereby overcoming the slag's stability without requiring excessive energy input
3Use of energy by moving object
If metal constituents are converted to metal chlorides to reduce vaporization temperature, then energy requirements are reduced, but additional processing steps are required
Solution Approach 1:
The invention merges the conversion and separation steps into a single integrated process. The gaseous chloride simultaneously converts metal constituents to volatile chlorides and enables their separation through volatility differences. This consolidation reduces the number of discrete processing steps while achieving both energy reduction and effective separation
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 process allows for the cost-effective recovery of valuable metals from slag wastes by converting them into volatile metal chlorides, enabling efficient extraction and reducing energy costs, with by-products like sulfuric acid and sodium hydroxide, and achieving high extraction rates for metals like zinc, copper, and lead.
Implementation Method 1
heating the solid waste material
Implementation Method 2
treating the heated material of step (i) with a gaseous chloride to form a gaseous metal chloride containing product
Implementation Method 3
as metal chlorides generally have lower vapourisation temperatures than other metal compounds such as oxides and the pure metals, less energy will be required to volatilise them
Data Source
AI summary
A process for recovering a metal chloride or mixed metal chloride from a solid waste material comprising recoverable metal containing constituents produced by lead, copper or zinc smelting and refining processes, said process comprising the steps of: (i) heating the solid waste material; (ii) treating the heated material of step (i) with a gaseous chloride to form a gaseous metal chloride containing product; and (iii) treating the gaseous metal chloride containing product of step (ii) to recover the metal chloride or mixed metal chloride. The metal chloride may be further treated to extract the metal itself.