Coal Ash Refining via Flotation Separation
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Solution Overview
Problem
Existing methods fail to efficiently separate and process coal ash and carbonaceous ashes from combustion processes, particularly due to variations in composition and high coal content in ashes from recycled fuel combustion, leading to unstable product quality and handling challenges, with harmful compounds complicating their use in construction and energy applications.
Innovation Solution
A flotation process is developed to treat a carefully proportioned mixture of coal ash and fly ash from recycled fuel combustion, using efficient dispersion and specific chemicals to separate a carbonaceous fraction for energy use and a pozzolanic silicate fraction, while removing harmful compounds from process waters, utilizing a collector oil and depressant to enhance selectivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If flotation process is used to separate coal ash and carbonaceous ashes, then separation efficiency is improved, but product quality stability deteriorates due to variations in ash composition
Solution Approach 1:
The patent adjusts the ratio of coal ash to carbonaceous ash in the feed mixture, optimizing the proportion of each component to ensure stable flotation results despite variations in individual ash compositions. This parameter change allows the process to handle variable input while maintaining consistent product quality.
Solution Approach 2:
The patent creates a composite feed material by mixing coal ash and carbonaceous ash in specific proportions. This composite approach allows the beneficial properties of each ash type to complement each other, stabilizing the overall flotation process and product quality despite variations in individual component compositions.
2Loss of energy
If ashes from recycled fuel combustion are processed, then energy utilization is improved, but handling complexity increases due to varied composition and high coal content
Solution Approach 1:
The patent combines the processing of coal ash and carbonaceous ash from recycled fuel combustion into a single integrated flotation process. This merging eliminates the need for separate handling systems for different ash types, reducing overall handling complexity while maintaining energy utilization benefits.
Solution Approach 2:
The flotation process is designed to handle multiple types of ash materials (coal ash and various carbonaceous ashes from different recycled fuel sources) using the same equipment and chemical regime. This universal approach simplifies handling by making the system adaptable to varied compositions without requiring specialized equipment for each ash type.
3Loss of energy
If high coal content ash is processed, then energy recovery is improved, but product purity deteriorates
Solution Approach 1:
The patent optimizes flotation parameters including reagent dosages, pH levels, and air flow rates to achieve effective separation even when processing high coal content materials. These parameter adjustments ensure that coal particles are efficiently recovered while maintaining the purity of the ash products, resolving the contradiction between energy recovery and product purity.
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 achieves stable and constant-quality products, enabling the effective utilization of coal ash as a binder and recycled fuel ash in construction, while efficiently removing harmful substances, thus overcoming the limitations of existing technologies in handling and processing these ashes.
Implementation Method 1
by treating a carefully proportioned mixture of these ashes in a common flotation process, by separating, after an efficient dispersion step, a carbonaceous fraction from said coal ash and from ash produced in the other combustion processes employing recycled fuels by utilizing a flotation technique
Implementation Method 2
after an efficient dispersion step, a carbonaceous fraction from said coal ash and from ash produced in the other combustion processes
Implementation Method 3
enables harmful compounds, such as different chlorine compounds contained in gasification ash in particular and dissolving in the process waters
Implementation Method 4
These compounds that become concentrated in the process waters may be removed from the process water circulation mechanically or chemically by precipitation
Data Source
AI summary
A method for industrial refining of coal ash created in power plants and carbonaceous ashes produced in other combustion processes by separating coal from said ashes and returning it to use and by recovering a substantially coal-free ash fraction obtained in the refining. In the method, coal ash and at least one ash fraction created by gasification technique in combustion plants are carefully proportioned in relation to one another and formed into a slurry mixture by means of an efficient dispersion technique, the slurry being then led to a flotation step, where a fraction rich in coal and a siliceous fraction poor in coal and a fraction dissolving in the process water are separated by flotation. The coal ash is arranged to have the highest proportion in the mixture to be taken to flotation, the ashes from combustion plants being dosed into said mixture in an amount that does not cause the maximum amounts of harmful substances to be exceeded in the qualities of the carbonaceous product and the silicate product poor in coal to be obtained.