Powdered Lime Composition for Flue Gas Desulfurization
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Solution Overview
Problem
Current powdered hydrated lime compositions, even second generation ones, do not adequately enhance the capture of sulfur compounds like SO2 in flue gases, while requiring excessive reagents that generate by-products, posing challenges in emission standards compliance and treatment.
Innovation Solution
A powdered lime composition with calcium hydroxide particles having a BET specific surface area ≥25 m²/g and BJH pore volume ≥0.1 cm³/g, supplemented with an alkali metal content of 0.2-3.5% by weight, which improves SO2 capture performance without compromising HCl capture abilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional slaked lime is used for neutralizing acidic compounds in flue gases, then the process is simple and inexpensive, but a significant excess of calcium reagent is necessary which generates additional by-products and residues
Solution Approach 1:
The invention changes the physical parameters of the slaked lime by increasing its specific surface area (≥25 m²/g) and pore volume (≥0.1 cm³/g), which enhances its reactivity and neutralization efficiency, allowing for reduced excess reagent while maintaining effective acid gas capture
Solution Approach 2:
The invention creates a composite material by combining slaked lime with specific additives (such as magnesium hydroxide, aluminum hydroxide, or organic compounds) to produce a modified absorbent that achieves better neutralization performance with lower excess reagent requirements
2Reliability
If additives are added to quicklime slaking water to promote HCl capture, then gaseous HCl reduction performance improves at temperatures above 200°C, but no effect on SO2 reduction is mentioned
Solution Approach 1:
The invention develops a multi-functional absorbent that simultaneously effectively captures both HCl and SO2 gases, unlike conventional additives that only improve HCl capture. The modified slaked lime achieves dual functionality through physical modification and additive combination, making it adaptable to flue gases containing multiple acidic components
3Reliability
If additives such as NaOH or CaCl2 are added to quenching water to promote desulphurization at low temperature, then SO2 capture improves near dew point, but the absorbent becomes deliquescent which may cause operational issues
Solution Approach 1:
The invention carefully controls the type and quantity of additives used in the quenching water to achieve the desired pore volume and surface area while preventing excessive deliquescence. By optimizing these parameters, the absorbent maintains both low-temperature desulphurization performance and adequate stability for practical operation
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 composition achieves superior SO2 reduction rates while maintaining excellent HCl capture performance, reducing the need for excessive reagents and by-product treatment, and also effectively captures HBr and HF, broadening the application of the dry process in flue gas purification.
Implementation Method 1
the neutralization reaction between gas and solid matter is not easy and a significant excess of calcium reagent is often necessary in relation to the quantity of acid to be neutralized
Implementation Method 2
the additive results in making the absorbent deliquesce in the presence of humidity, which promotes the presence of a liquid film at the solid-gas interface and improves the capture of SO 2
Implementation Method 3
a powdered lime composition comprising calcium hydroxide particles, having a BET specific surface area equal to or greater than 25 m 2/g and a BJH pore volume equal to or greater than 0.1 cm 3/g
Data Source
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AI summary
The invention relates to a pulverulent lime composition comprising an alkali metal and having a specific surface BET which is equal to or larger than 25 m2/g and a total porous volume BJH of nitrogen desorption which is equal to or higher than 0,1 cm3/g. The invention also relates to a method for producing said composition, and to the use of the same for reducing the quantity of exhaust gas produced.