Fly Ash Agglomerates Stabilizing Hazardous Contaminants
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Solution Overview
Problem
New air pollution control regulations at coal-fired power plants alter fly ash properties, making it unsuitable for concrete admixtures and creating challenges for disposal, as they introduce hazardous substances like arsenic, selenium, and chlorides, requiring alternative uses and stabilization methods for fly ash and dry alkaline sorbent byproducts.
Innovation Solution
The development of aluminosilicate compositions formed into agglomerates using fly ash as a base material with a polysulfide binding agent and leach reduction additives, which can be formed into pellets without requiring heating or pressure, providing rapid strength development and reduced leachability of hazardous contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If new air pollution control technologies are implemented to control acid gas discharge and vapor-phase mercury, then harmful emissions are reduced, but fly ash properties are altered making it unsuitable for concrete admixtures
Solution Approach 1:
The patent converts the harmful altered fly ash properties into a beneficial product by using the same fly ash containing hazardous substances (arsenic, selenium, chlorides) as the base material for agglomerates. The harmful contaminants are immobilized within the agglomerate structure, transforming the waste stream into a useful construction material that provides both acid gas control benefits and maintains concrete applicability.
Solution Approach 2:
The patent creates composite agglomerates by combining altered fly ash with binding agents and leach reduction additives. This composite structure allows the material to simultaneously achieve contaminant immobilization, structural integrity for concrete use, and reduced leachability, resolving the contradiction between emission control benefits and concrete suitability.
2Object-affected harmful factors
If alkaline sorbents are injected into the duct for acid gas control, then HCl removal efficiency increases to as high as 97%, but the resulting fly ash contains high concentrations of arsenic, selenium, and chlorides creating leachability concerns
Solution Approach 1:
The patent transforms the leachable hazardous contaminants (arsenic, selenium, chlorides) resulting from alkaline sorbent injection into immobilized components within the agglomerate structure. The binding agents and leach reduction additives convert the harmful leachable substances into a stable, non-leachable form, maintaining the beneficial HCl removal while eliminating the leachability problem.
Solution Approach 2:
The patent changes the chemical and physical parameters of the fly ash by incorporating binding agents and leach reduction additives. These parameter changes reduce the solubility and mobility of arsenic, selenium, and chlorides, transforming them from leachable hazardous substances into stable, immobilized components within the agglomerate matrix.
3Quantity of substance
If traditional chemical or physical water treatment is used for FGD scrubber wastewater, then treatment cost is reduced, but the treatment is ineffective for soluble selenates and cannot meet new discharge limits
Solution Approach 1:
The patent extracts soluble selenates and other contaminants from FGD scrubber wastewater by incorporating them into the agglomerate formation process. The binding agents and leach reduction additives remove these dissolved substances from the liquid phase and immobilize them within the solid agglomerate structure, achieving effective separation and treatment.
Solution Approach 2:
The patent uses composite agglomerates containing binding agents and leach reduction additives to treat FGD scrubber wastewater. This composite approach creates a material that can simultaneously bind and immobilize soluble selenates, providing effective treatment for contaminants that traditional methods cannot address.
4Object-affected harmful factors
If Zero Liquid Discharge processes are used to eliminate water discharge from FGD scrubbers, then wastewater discharge is eliminated, but an entirely new hazardous residual sludge is produced requiring disposal
Solution Approach 1:
The patent recovers the hazardous residual sludge from ZLD processes by incorporating it into the agglomerate formation process. Instead of discarding the sludge as hazardous waste, the binding agents and leach reduction additives transform it into a stable, immobilized component of the agglomerate, converting waste disposal into a beneficial use.
Solution Approach 2:
The patent creates composite agglomerates that incorporate ZLD residual sludge along with binding agents and leach reduction additives. This composite structure immobilizes the hazardous substances in the sludge, transforming the disposal problem into a useful material that can be utilized in construction applications.
5Object-generated harmful factors
If fly ash is stabilized and solidified into agglomerates with binding agents, then leachability and permeability are reduced, but the process complexity increases
Solution Approach 1:
The patent enables the altered fly ash to self-stabilize by using its own characteristics as the base material for agglomerate formation. The fly ash itself provides the matrix structure, while binding agents and leach reduction additives work within this matrix to achieve contaminant immobilization, allowing the material to self-organize into a stable form without complex external processing.
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 effectively stabilizes and solidifies fly ash wastes, reducing leachability and permeability, allowing for the safe incorporation of high chloride solids and enabling the use of fly ash in concrete applications, while avoiding wastewater discharge and landfilled hazards.
Implementation Method 1
aluminosilicate compositions formed into agglomerates using fly ash as a base material with a polysulfide binding agent
Implementation Method 2
leach reduction additives, which can be formed into pellets without requiring heating or pressure, providing rapid strength development and reduced leachability of hazardous contaminants
Data Source
AI summary
An agglomerate is provided that can include an aluminosilicate (ash) base material and one or more of a binding agent or leach reduction agent. Each of the agglomerate and binding agent can include no more than about 25 wt. % cement.