MSWI Ash Metal Recovery via Froth Flotation and Acid Leaching
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Solution Overview
Problem
Current methods for recovering valuable metals from municipal solid waste incineration (MSWI) ash are inefficient due to high alkalinity, complex composition, and environmental concerns, leading to significant losses and environmental pollution.
Innovation Solution
An integrated process combining size classification, froth flotation, magnetic separation, gravity separation, acid leaching, and chemical separation to recover valuable metals, including the use of a novel reagent scheme for froth flotation and lime removal technology to reduce acid consumption and enhance metal recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If acid leaching is used to recover valuable metals from MSWI ash, then metal recovery efficiency is improved, but acid consumption increases exceptionally and heavy metals are mobilized causing environmental pollution
Solution Approach 1:
The patent applies preliminary action by using size classification and froth flotation to pre-concentrate valuable metals from MSWI ash before acid leaching. This pre-concentration step reduces the amount of material requiring acid treatment, thereby decreasing acid consumption and limiting heavy metal mobilization to a smaller, controlled portion of the waste stream.
Solution Approach 2:
The patent introduces an intermediary substance (collectors and modifiers in flotation) that mediates between the MSWI ash and the subsequent acid leaching process. These chemicals selectively bind to valuable metal particles, enabling their separation from the bulk ash matrix, which then reduces the burden on the acid leaching step and minimizes environmental pollution.
2Productivity
If direct acid leaching is applied to MSWI ash, then valuable metal extraction is enhanced, but the complex composition including Al, Si, Ca, and Na requires significant water treatment
Solution Approach 1:
The patent segments the MSWI ash processing into distinct stages: size classification, froth flotation for valuable metal concentration, and then acid leaching. This segmentation allows the complex composition (Al, Si, Ca, Na) to be partially separated in earlier stages, reducing the burden on water treatment systems in later stages.
Solution Approach 2:
The patent extracts and removes problematic components (Al, Si, Ca, Na) through size classification and froth flotation before acid leaching. By taking out these contaminant elements in preliminary steps, the patent reduces the complexity of water treatment required for the subsequent metal extraction process.
3Reliability
If high alkalinity conditions are maintained in MSWI ash processing, then heavy metal stabilization is achieved, but valuable metal recovery becomes difficult due to acid consumption
Solution Approach 1:
The patent applies preliminary action by performing size classification and froth flotation before acid leaching to pre-concentrate valuable metals. This reduces the total amount of material that requires acid treatment, thereby lowering acid consumption while still maintaining heavy metal stabilization in the treated portion.
Solution Approach 2:
The patent changes the parameters of the processing system by introducing flotation chemistry (collectors, modifiers, pH control) that operates under high alkalinity conditions to concentrate valuable metals. This allows the system to maintain high alkalinity for heavy metal stabilization while using a smaller volume of acid in the subsequent leaching step.
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 process effectively concentrates and purifies valuable metals like Ti, Fe, Cu, Zn, and Ni, increasing their economic value and reducing environmental impact by improving recovery efficiency and reducing chemical consumption.
Implementation Method 1
adding the MSWI ash in a froth floatation solution to separate the MSWI ash in a froth floating fraction and a tailings fraction
Implementation Method 2
contact of the MSWI ash with a magnetic field to provide a magnetic fraction of the ash and a non-magnetic fraction of the ash
Implementation Method 3
adding the MSWI ash to a float/sink solution with a specific gravity of 2.4-3.0 to provide a float fraction and a sink fraction
Implementation Method 4
treating the ash with a leaching solution to provide a leachate
Data Source
AI summary
The present disclosure concerns processes and the combinations thereof for the enrichment and/or isolation of valuable metals from municipal solid waste incineration (MSWI) ash. Included are processes of size separation, froth floatation, magnetic separation, specific gravity separation, chemical separation, as well as the removal of lime. BY utilizing two or more, circuits of treatment are also provided that allow for fractionation of enriched valuable metals(s) from which purification thereof can be readily achieved.