Secondary Aggregate Production via Rotating Drum Carbonation
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Solution Overview
Problem
Existing methods for producing secondary aggregates from inert waste fines, such as those from quarrying and combustion processes, are inefficient in forming hard aggregates suitable for concrete production, as they require extensive mixing and longer hardening times compared to hydraulic cement systems.
Innovation Solution
A process combining accelerated carbonation and tumbling of CO2-reactive inert waste fines with a carbonatable binder in a controlled CO2-rich environment, forming successive layers of carbonate-based reaction products within minutes, using a rotating drum or tray to create a hard aggregate suitable for concrete applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional mixing equipment is used to mechanically activate reactive components through thorough mixing, then the reactive components are activated, but the process requires extensive mixing time and complex mixing equipment
Solution Approach 1:
The patent replaces complex mechanical mixing equipment with a simple rotating drum system. Instead of using planetary mixers or other sophisticated mixing devices, the invention uses a drum that rotates to tumble the material, allowing carbonation to occur naturally through exposure to CO2 atmosphere while the drum rotates. This substitution dramatically simplifies the mechanical system while maintaining effective carbonation activation.
Solution Approach 2:
The patent changes the operational parameters by controlling the rotation speed of the drum and the CO2 atmosphere conditions. By optimizing these parameters, the carbonation process achieves high reactivity without requiring complex mixing mechanisms. The rotation speed is controlled to provide adequate exposure to CO2 while preventing excessive material breakdown, achieving fast carbonation with simple equipment.
2Strength
If hydraulic cement systems are used for hardening, then strength is achieved, but the hardening time is extended compared to the desired rapid processing
Solution Approach 1:
The patent utilizes the phase transition of CO2 from gas to dissolved state in the moisture present on the waste fine surfaces. This phase change enables rapid carbonation reactions that form hard carbonate crusts on the particle surfaces within minutes, achieving hydraulic-like strength without the extended hardening times associated with traditional hydraulic cement systems.
Solution Approach 2:
The patent converts the typically harmful or wasted CO2 emissions into a beneficial hardening agent. By exposing the carbonatable waste fines to CO2 atmosphere in the rotating drum, the harmful gas is transformed into solid carbonate crusts that provide the desired hardness and strength to the aggregate particles, achieving rapid hardening while simultaneously addressing environmental concerns.
3Reliability
If accelerated carbonation is used to form hard granulates, then non-leaching granulates are produced, but the process requires complex mixing equipment and thorough mixing
Solution Approach 1:
The patent replaces complex mixing equipment with a simple rotating drum system. Instead of using planetary mixers or other sophisticated mixing devices, the invention uses a drum that rotates to tumble the material, allowing carbonation to occur naturally through exposure to CO2 atmosphere while the drum rotates. This substitution dramatically simplifies the mechanical system while maintaining effective carbonation activation.
4Ease of manufacture
If conventional aggregate production methods are used, then aggregates are produced, but the process is not cost-effective and environmentally friendly
Solution Approach 1:
The patent converts the typically harmful or wasted CO2 emissions into a beneficial hardening agent. By exposing the carbonatable waste fines to CO2 atmosphere in the rotating drum, the harmful gas is transformed into solid carbonate crusts that provide the desired hardness and strength to the aggregate particles, achieving rapid hardening while simultaneously addressing environmental concerns.
Solution Approach 2:
The patent recovers value from materials that would otherwise be discarded, such as 'out-of-date' Portland cement and other carbonatable waste fines. By applying the accelerated carbonation process in the rotating drum, these discarded materials are transformed into valuable secondary aggregates, reducing waste disposal costs and eliminating the need for energy-intensive primary aggregate extraction and 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 process efficiently produces aggregates with rapid strength development, achieving up to 97% of theoretical carbonation values in minutes, offering a cost-effective and environmentally friendly alternative to traditional aggregate production methods, with the ability to utilize 'out-of-date' materials like Portland cement.
Implementation Method 1
tumbling CO2-reactive i.e. carbonatable, fines, or inert fines and a CO2-reactive i.e. carbonatable, binder in the presence of moisture and carbon dioxide
Data Source
AI summary
Secondary aggregates are prepared from inert waste fines, from, for example, quarrying and combustion processes, using a combination of accelerated carbonation and tumbling, such that aggregate particles composed of successive layers of solid carbonate-based reaction products form a hard aggregate suitable for use in concrete. The process may carried out by loading the starting materials, and if necessary, water into a cylindrical drum that is rotatable about its horizontal axis, and the interior is charged with a carbon dioxide atmosphere, or mounted within a larger vessel that holds a carbon dioxide atmosphere. Aggregates are formed as coatings on core particles as tumbling proceeds, and the coatings are hardened by in situ formation of carbonates by reaction with the carbon dioxide.