Solar Reflective Granules via Sintering and Cooling Control
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Solution Overview
Problem
The existing methods for producing solar reflective roofing granules are costly and inefficient, with a significant amount of waste material generated during the crushing process, and there is a need for granules with high solar reflectance and low lightness L* values.
Innovation Solution
The method involves forming green body granules from aluminosilicate granule fines, sintering them at high temperatures, and controlling the cooling regime to achieve a temperature hold between 700° C. and 900° C. or a slow cooling rate, while adding aluminum trihydrate (ATH) as a dopant to enhance solar reflectance without significantly affecting the lightness L* value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If standard base rock is crushed to produce solar reflective granules, then solar reflective granules can be produced, but about 40 wt % to 50 wt % of the crushed stone becomes waste material (granule fines)
Solution Approach 1:
The patent converts the previously wasted granule fines (40-50 wt% of crushed stone) into a valuable resource by using them as the primary raw material for producing solar reflective granules through sintering. This transforms the harmful waste disposal problem into a beneficial recycling process that reduces overall material waste and production costs
2Ease of manufacture
If granule fines are used as waste material, then production costs increase, but if they are utilized in the sintering process, then production costs are reduced
Solution Approach 1:
The patent implements a recovery process where granule fines that were previously discarded as waste are collected and reused as the main feed material for sintering to produce solar reflective granules. This recovery approach eliminates the need to purchase and process fresh raw materials, significantly reducing production costs
3Manufacturing precision
If aluminum trihydrate (ATH) is added as a dopant to enhance solar reflectance, then solar reflectance increases to at least 30%, but the process complexity increases
Solution Approach 1:
The patent combines the ATH doping step with the existing sintering process by adding ATH to the granule fines before sintering. This merging of operations allows the dopant to be incorporated during the high-temperature treatment, achieving enhanced solar reflectance (at least 30%) without requiring separate doping equipment or complex multi-step processes
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 results in roofing granules with high solar reflectance, low lightness, good strength, and weather resistance, reducing waste and production costs while maintaining desired optical properties.
Implementation Method 1
heating the green body granules to form sintered granules
Implementation Method 2
cooling the sintered granules according to a cooling regime, wherein the cooling regime comprises a temperature hold between 700° C. and 900° C. for at least one hour
Data Source
AI summary
A method of making a plurality of composite granules can include: forming green body granules comprising an aluminosilicate; heating the green body granules to form sintered granules; cooling the sintered granules according to a cooling regime, wherein the cooling regime comprises a temperature hold between 700° C. and 900° C. for at least one hour. In a particular embodiment, the aluminosilicate for making the composite granules can have a particle size less than 150 μm. The composite granules are particularly suitable as roofing granules and can have a desired combination of high solar reflectance SR and low lightness L*, a low bulk density, good weather resistance and strength.