Waste Tire-Derived Asphalt Modifier via PAH Removal
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Solution Overview
Problem
Existing asphalt binder modification processes often require extended processing times, extensive heating, and produce side products with high polycyclic aromatic hydrocarbon (PAH) compounds, which are harmful and difficult to manage, and they may add substantial amounts of carbon black or rubber, increasing costs and environmental concerns.
Innovation Solution
The method involves pyrolyzing waste tires to produce a fractional oil product, removing PAH compounds through distillation, solvent extraction, centrifugation, or wiped film evaporation, and combining the resulting reduced-PAH oil fraction with an asphalt binder to create a modified asphalt composition that is safer, more stable, and less flammable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional asphalt binder modification processes are used to incorporate tire rubber, then rubber modification is achieved, but processing time is extended and extensive heating is required
Solution Approach 1:
The patent applies preliminary action by pre-processing the tire rubber through pyrolysis to create pyrolyzed rubber particles before incorporating them into the asphalt binder. This pre-treatment breaks down the rubber structure in advance, eliminating the need for extended processing times and extensive heating during the asphalt modification process itself. The pyrolyzed rubber is then readily incorporable into the binder without requiring prolonged mixing or high-temperature treatment.
2Object-affected harmful factors
If conventional tire rubber modification processes are used, then rubber is incorporated into asphalt, but harmful PAH compounds are produced that are difficult to manage
Solution Approach 1:
The patent applies the extraction principle by removing harmful PAH compounds from the pyrolysis oil through distillation or other separation techniques. The process extracts and separates the PAH fraction from the beneficial pyrolysis products, allowing the cleaner oil to be used for asphalt modification. This targeted removal of harmful components simplifies the overall process by focusing on extracting only the problematic substances while retaining the useful modifiers.
Solution Approach 2:
The patent applies parameter changes by controlling the pyrolysis conditions (temperature, atmosphere, residence time) to minimize PAH formation in the first place. By optimizing these parameters during the pyrolysis process, the resulting oil has reduced PAH content compared to conventional methods. Additionally, subsequent refining parameters are adjusted to further reduce PAH levels to acceptable ranges.
3Reliability
If substantial amounts of carbon black or rubber are added to modify asphalt, then modification effectiveness is improved, but costs increase and environmental concerns are amplified
Solution Approach 1:
The patent applies parameter changes by transforming the chemical structure of the rubber through pyrolysis, converting it from a macromolecular polymer into smaller molecular weight compounds. This fundamental parameter change in the rubber's molecular state allows for more efficient incorporation into the asphalt binder at lower quantities. The pyrolyzed rubber products interact more effectively with the asphalt molecules, achieving the desired modification effects with reduced material input compared to using virgin rubber.
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 approach reduces processing time, minimizes fire risks, improves control over ingredients, enhances product stability and safety by removing low flash point components and PAHs, and produces modified asphalt with improved properties such as increased flexibility and reduced flammability.
Implementation Method 1
at least partially pyrolyzing, separately from such asphaltic binder, whole rubber articles or size-reduced rubber particles to provide one or more pyrolyzed rubber fractions
Implementation Method 2
fractionally distilling the pyrolyzed oil fraction over a temperature range that removes a desired initial boiling point or desired minimum flash point pyrolyzed oil fraction
Implementation Method 3
centrifuging the pyrolyzed oil fraction to separate a desired initial boiling point or desired minimum flash point pyrolyzed oil fraction from a fraction containing concentrated PAH compounds
Data Source
AI summary
Products from waste tire pyrolysis are prepared using an initial step of i) at least partially pyrolyzing, separately from such asphaltic binder, whole rubber articles or size-reduced rubber particles to provide one or more pyrolyzed rubber fractions including a pyrolyzed oil fraction having a selected minimum initial boiling point or flash point, and ii) removing some or all polycyclic aromatic hydrocarbon (PAH) compounds from such pyrolyzed oil fraction to provide a reduced-PAH and preferably translucent pyrolyzed oil fraction that may be combined with an asphaltic binder to provide a modified asphalt composition.