Whitened Fly Ash Process via Exhaustive Magnetic Separation
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Solution Overview
Problem
Current processes are unable to effectively whiten coarse fly ash to a sufficient degree for use as a filler or extender in ceramic products, paints, rubber, and plastics, due to high iron oxide and unburnt carbon content, limiting its application in these industries.
Innovation Solution
A process involving size classification, optional slurry formation, exhaustive magnetic separation with increasing magnetic field strengths, and milling to produce whitened fly ash with reduced iron oxide content, achieving a particle size suitable for use in various applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional beneficiation processes are used to treat fly ash, then iron oxide content is reduced to some extent, but the fly ash is not white enough for demanding applications such as paint extender
Solution Approach 1:
The patent applies multiple magnetic separation steps with progressively increasing magnetic field strengths (first magnetic extraction step, second magnetic extraction step at higher field strength) to exhaustively remove iron oxide particles. This systematic parameter change in magnetic field intensity enables achieving whiteness levels suitable for paint extenders and other demanding applications, overcoming the limitation of conventional single-step beneficiation processes
Solution Approach 2:
The magnetic separation process is divided into multiple sequential steps with increasing field strengths. The first magnetic extraction step removes highly magnetic iron oxide particles, followed by a second magnetic extraction step at higher field strength to remove remaining magnetically susceptible material. This segmentation of the separation process enables exhaustive removal of iron oxides to achieve the required whiteness level
2Loss of substance
If coarse fly ash is used directly as filler, then waste disposal issues are addressed, but the colour is grey or off-white due to iron oxide and unburnt carbon, limiting its application
Solution Approach 1:
The patent converts the harmful effect of iron oxide (which causes grey/off-white colour) into a beneficial separation target. By applying magnetic separation, the iron oxide particles that cause colour problems are selectively removed, transforming the waste fly ash into a white filler suitable for high-value applications such as paint extenders, thereby converting a harmful property into a separable component
3Manufacturing precision
If magnetic separation is used to remove iron oxide, then whiteness is improved, but multiple extraction steps are required to achieve sufficient whiteness for paint extender applications
Solution Approach 1:
The patent employs a dynamic magnetic separation process where the magnetic field strength is progressively increased across multiple steps. The first magnetic extraction step uses a lower field strength to remove highly magnetic particles, while subsequent steps use progressively higher field strengths to remove remaining magnetically susceptible material. This dynamic approach optimizes the balance between achieving sufficient whiteness and managing process complexity
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 results in fly ash with a high whiteness value, suitable for use in ceramics, paints, rubber, and plastics, reducing waste disposal issues and providing an environmentally friendly, cost-effective solution for utilizing coarser fly ash.
Implementation Method 1
subjecting the size classified fly ash obtained in step (a) or the slurry obtained in step (b) to an exhaustive magnetic separation step to form magnetically treated fly ash
Data Source
AI summary
A process for preparing whitened fly ash includes the steps of: (a) subjecting fly ash to a size classification step to obtain size classified fly ash having a particle size such that at least 90 wt % has a particle size of from 44 μm to 250 μm; (b) optionally, contacting the size classified fly ash from step (a) with water to form a slurry, wherein the slurry has a solid content of less than 40 wt %; (c) subjecting the slurry obtained in step (b) to an exhaustive magnetic separation step to form magnetically treated fly ash, wherein the exhaustive magnetic separation step includes a first magnetic extraction step and a second magnetic extraction step, wherein the second magnetic extraction step is carried out at a higher magnetic field strength than the first magnetic extraction step; and (d) subjecting the magnetically treated fly ash obtained in step (c) to milling to form whitened fly ash.