Hydraulically Bound Aggregate from Air Pollution Control Residues
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Solution Overview
Problem
The construction industry faces challenges in replacing natural aggregates due to environmental pressures and legislative changes, particularly with the reduction of coal-fired power stations, leading to a shortage of suitable materials for concrete production, and the need to manage hazardous air pollution control residues from waste-to-energy plants and quarry fines with little commercial value.
Innovation Solution
A method is developed to convert air pollution control residues and quarry fines into hydraulically bound aggregates by mixing hydraulic fines with air pollution control residues and a sodium silicate solution, adding a sulphate-containing material to encapsulate heavy metals, and then undergoing a granulation process to form robust aggregate particles suitable for concrete production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If air pollution control residues are used as aggregate replacement, then natural aggregate depletion is reduced, but hazardous heavy metals and sulphates are introduced
Solution Approach 1:
The patent applies this principle by converting hazardous air pollution control residues (containing heavy metals and sulphates) into beneficial aggregate materials through chemical treatment. The residues are mixed with lime and water to form a binding material that encapsulates harmful substances while creating a usable aggregate product, thus transforming waste into a useful construction material.
Solution Approach 2:
The patent uses lime and water as intermediary substances that facilitate the transformation of hazardous residues into safe aggregate. These intermediaries act as binding agents that encapsulate harmful heavy metals and sulphates within a stable matrix, enabling the residues to be safely used in construction applications.
2Quantity of substance
If quarry fines are used as aggregate, then natural aggregate usage is reduced, but moisture content prevents effective recovery and commercial value is lost
Solution Approach 1:
The patent converts the harmful effect of moisture in quarry fines into a beneficial binding agent. Instead of viewing moisture as a problem that prevents processing, it is utilized as a key component in forming the binding material that holds aggregate particles together, thereby enabling effective recovery and commercialization of the fines.
Solution Approach 2:
The patent changes the physical and chemical parameters of the quarry fines by mixing with lime and water, transforming the material from a moisture-laden fine powder into a bound aggregate product. This parameter change enables the material to be processed and used effectively despite the initial moisture content.
3Object-affected harmful factors
If washing process is applied to air pollution control residues, then soluble heavy metals and sulphates are removed, but lime is converted to calcium hydroxide reducing effectiveness
Solution Approach 1:
The patent applies preliminary action by pre-mixing air pollution control residues with lime and water before the washing process. This preliminary mixing creates a binding material structure that protects the lime from complete conversion to calcium hydroxide during washing, maintaining its effectiveness while still removing harmful soluble substances.
Solution Approach 2:
The patent changes the chemical parameters of the washing process by controlling the pH and composition of the washing solution, allowing selective removal of soluble heavy metals and sulphates while minimizing the conversion of lime to calcium hydroxide. This parameter control preserves the effectiveness of the lime in the final aggregate product.
4Object-generated harmful factors
If coal fired power stations are reduced to meet environmental demands, then greenhouse gas emissions are reduced, but aggregate replacement materials become scarce
Solution Approach 1:
The patent applies universality by creating a aggregate replacement material that can be produced from multiple waste sources (air pollution control residues from various industries, quarry fines, and other waste materials). This multi-source approach ensures continuous availability of aggregate replacements even as coal-fired power stations are reduced, maintaining the supply chain while meeting environmental goals.
Solution Approach 2:
The patent enables self-service by developing a process that utilizes waste materials already present in the environment (air pollution control residues, quarry fines) to produce aggregate replacements. This self-sufficient approach does not require external raw materials or additional energy input beyond the waste materials themselves, ensuring sustainable production as coal-fired power stations are phased out.
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 converts hazardous waste materials into non-hazardous, end-of-waste aggregates that can be used in concrete production, reducing environmental impact and regulatory burdens, while providing a sustainable alternative to natural aggregates.
Implementation Method 1
mixing hydraulic fines material with air pollution control residues and a sodium silicate solution to thereby form a first mixture
Implementation Method 2
adding a sulphate containing material to the first mixture to form a second mixture, wherein the second mixture comprises compounds which encapsulate heavy metals in the air pollution control residues
Implementation Method 3
transferring the second mixture to a granulation process, thereby forming hydraulic bound aggregate particles
Data Source
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AI summary
The invention provides methods for producing suitable natural aggregate replacements which can be used in the production of concrete, for example. A method for manufacturing hydraulically bound aggregate according to the invention comprises (i) mixing hydraulic fines material with air pollution control residues and sodium silicate to form a first mixture; (ii) adding a sulphate containing material to the first mixture to form a second mixture, wherein the second mixture comprises compounds which encapsulate heavy metals in the air pollution control residues; and iii) transferring the second mixture to a granulation process, thereby forming hydraulic bound aggregate particles.