Lightweight Aggregates From Waste-Coal Combustion Ash via Controlled Sintering
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Solution Overview
Problem
The current methods for producing lightweight aggregates (LWA) from waste-coal combustion ash (W-CCA) are inefficient and costly, leading to environmental pollution and limited accessibility due to high transportation costs and landfill disposal of untreated W-CCA, which also affects the price and availability of LWA.
Innovation Solution
A method involving the sintering process with a 40% molten liquid phase viscosity between 100 Pa·s and 107 Pa·s and emitting a minimum gas amount of 0.24% by weight to form pores in the liquid phase during sintering, using thermodynamic modeling and X-ray computed tomography to optimize the production process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional expanded shale, clay, and slate based LWA are used, then LWA is available at certain locations, but transportation cost increases and accessibility decreases
Solution Approach 1:
The patent changes the raw material parameter from traditional expanded shale, clay, and slate to waste-coal combustion ash (W-CCA). This parameter change enables LWA production in regions with W-CCA availability, thereby improving accessibility and reducing transportation costs while maintaining product quality through controlled sintering parameters
Solution Approach 2:
The patent utilizes waste-coal combustion ash as both the raw material and the source of gas for pore formation during sintering. The W-CCA serves multiple functions: as the aggregate material, as the gas source for creating pores, and as a waste product that needs disposal, thereby eliminating the need for separate gas generation systems and reducing overall production costs
2Productivity
If W-CCA is disposed to landfills, then recycling gap is reduced, but environmental pollution and health impacts increase
Solution Approach 1:
The patent converts the harmful waste product W-CCA that would otherwise pollute landfills into a beneficial LWA material. The sintering process transforms the ash into a functional aggregate with controlled porosity, thereby eliminating environmental pollution while creating a valuable construction material, achieving both recycling and environmental protection
3Ease of manufacture
If sintering is used to produce LWA from W-CCA, then LWA can be produced, but advanced understanding of sintering mechanisms is required
Solution Approach 1:
The patent simplifies the sintering process by establishing specific parameter ranges: liquid phase content between 30-70%, gas emission between 0.1-5%, and controlled heating rates. These parameter specifications transform the complex sintering mechanism into a manageable process with defined operational boundaries, reducing the barrier to entry while maintaining product quality
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 efficiently converts W-CCA into LWA, reducing landfill waste, increasing accessibility, and lowering production costs while maintaining the structural integrity and porosity necessary for applications like lightweight concrete and green roofs.
Implementation Method 1
converting the waste W-CCA available in the landfills to LWA is a viable solution that not only promotes landfill diversion, but also can increase the accessibility of LWA. Sintering is one of the techniques that can be employed in order to produce LWA from W-CCA.
Implementation Method 2
forming at least a 40% by mass molten liquid phase for the lightweight aggregate (LWA) using W-CCA
Implementation Method 3
emitting a minimum gas amount of 0.24% by weight of the LWA to form pores in the liquid phase during the sintering
Data Source
AI summary
Manufacturing lightweight aggregate (LWA) by a sintering technique requires a delicate balance among three conditions: forming sufficient amount of molten liquid phase during sintering; reaching an appropriate viscosity for solid-liquid suspension; and emitting sufficient amount of gas that can be entrapped by the liquid phase to form pores. LWAs were made from low-calcium and high-calcium Waste Coal Combustion Ash (W-CCA) including fly ash and bottom ash. A mass fraction of at least 40% liquid phase for fly ash and 50% for bottom ash is required for a successful entrapment of emitted gaseous phases during sintering. Larger pores were observed in the microstructure of LWA samples made using high-calcium W-CCA in comparison to low-calcium W-CCA. This result was mainly attributed to the high-calcium samples forming liquid phases with lower viscosity values and emitting higher amounts of gaseous phase during sintering than did the low-calcium samples. The gaseous phase was generated by hematite reduction and anhydrite decomposition.