Hydrated Lime Manufacturing via Segmented Grinding and Classification
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Solution Overview
Problem
Conventional processes for producing hydrated lime fail to achieve high reactivity and purity necessary for effective capture of HCl and SO2 in air pollution control applications, leading to suboptimal performance in flue gas treatment.
Innovation Solution
A method involving grinding calcium oxide to a coarse particle size, air classification to remove smaller particles, hydration, flash-drying, and further milling to achieve a high BET surface area and small particle size, resulting in a hydrated lime with enhanced reactivity and purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hydration process is used, then production efficiency is maintained, but reactivity and purity of hydrated lime are insufficient
Solution Approach 1:
The patent applies preliminary action by pre-grinding calcium oxide to a coarse particle size (4-8 mesh) before hydration, and pre-classifying to remove fine particles. This preliminary preparation ensures that only coarse particles with proper morphology undergo hydration, which inherently produces more reactive hydrated lime without requiring complex post-processing
Solution Approach 2:
The patent segments the hydration process into distinct stages: pre-grinding to coarse size, classification to remove fines, hydration of selected coarse particles, and post-grinding to final size. This segmentation allows each stage to be optimized independently, achieving high reactivity through controlled coarse particle hydration while maintaining manufacturing efficiency
2Manufacturing precision
If fine particles are removed by air classification, then purity and reactivity improve, but particle size distribution becomes more restricted
Solution Approach 1:
The patent performs preliminary classification before hydration to remove fine particles from the calcium oxide feed. This preliminary action ensures that only coarse particles (4-8 mesh) enter the hydration stage, improving the quality of the final product by ensuring uniform particle size and high reactivity, while the classification process is designed to maintain production throughput
3Reliability
If multiple grinding and classification stages are implemented, then BET surface area and reactivity increase, but process complexity increases
Solution Approach 1:
The patent segments the process into two distinct grinding stages: pre-grinding to coarse size (4-8 mesh) before hydration, and post-grinding to final size after hydration. This segmentation is necessary because hydrating coarse particles produces the desired high reactivity and BET surface area (25-40 m²/g) that cannot be achieved by grinding fine particles before hydration. The classification stages are integrated to remove fines at each point, maintaining productivity while achieving the required product quality for effective acid gas removal
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
The resulting hydrated lime exhibits superior performance in capturing HCl and SO2, with significantly reduced reaction time and improved acid gas removal efficiency compared to conventional methods.
Implementation Method 1
feeding the ground lime into an air classification system; removing a refined fine lime from the air classification system wherein the refined fine lime has a particle size distribution of greater than 70% minus 200 mesh
Implementation Method 2
adding water to the refined fine lime to form damp hydrated lime
Implementation Method 3
flash-drying the damp hydrated lime to form dried hydrated lime
Data Source
AI summary
A hydrated lime product exhibiting superior reactivity towards HCl and SO2 in air pollution control applications. Also disclosed is a method of providing highly reactive hydrated lime and the resultant lime hydrate where an initial lime feed comprising calcium and impurities is first ground to a particle-size distribution with relatively course particles. Smaller particles are then removed from this ground lime and the smaller particles are hydrated and flash dried to form a hydrated lime, which is then milled to a significantly smaller particle size than that of the relatively course particles. The resultant lime hydrate product has available CaOH of greater than 92%, a citric acid reactivity of less than 20 seconds, a BET surface area greater than 18, a D90 less than 10 μm, a D50 less than 4 μm, a D90/D50 less than 3, and a large pore volume of greater than 0.2 BJH.