Integrated FGD System with Sodium Packed Bed for Deep SOx Capture
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Solution Overview
Problem
Current calcium-based flue gas desulfurization (FGD) technologies face challenges in achieving high enough sulfur oxide (SOx) removal efficiency to meet stringent emission standards, particularly in coal-fired power plants, with limitations in cost-effectiveness and operational efficiency, especially when dealing with low sulfur coal and varying environmental conditions.
Innovation Solution
An integrated FGD system combining traditional wet calcium FGD with a sodium-based packed bed absorber, utilizing a caustic solution with soluble calcium compounds and alkali reagents to enhance SOx capture efficiency and prevent fouling, scaling, or plugging in the packed bed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional wet calcium FGD is used for SOx removal, then the system is cost-effective and easy to operate, but the SOx removal efficiency is limited to around 97% and cannot meet stringent emission standards of 17.5 ppm
Solution Approach 1:
The FGD system is segmented into two distinct functional sections: a lower wet calcium FGD section for coarse SOx removal, and an upper sodium-based packed bed absorber section for deep SOx capture. This segmentation allows each section to be optimized for its specific function, achieving over 99.6% overall removal efficiency while maintaining operational simplicity through modular design
Solution Approach 2:
The patent merges two different FGD technologies (wet calcium FGD and sodium-based packed bed absorber) into a single integrated system. The lower section uses traditional wet calcium FGD for bulk removal, while the upper section employs sodium-based absorption for deep capture, combining the advantages of both methods to achieve stringent emission standards
2Manufacturing precision
If a packed bed absorber is added above traditional Ca-WFGD to achieve deep SOx capture, then SOx removal efficiency exceeds 99.6%, but fouling, scaling, or plugging of the packed bed may occur
Solution Approach 1:
Different solution compositions are used in different sections: the lower wet FGD section uses traditional calcium-based slurry, while the upper packed bed section uses a caustic solution with soluble calcium compounds and alkali reagents. This local quality differentiation prevents fouling and scaling in the packed bed by maintaining optimal pH and chemical composition specific to that section
Solution Approach 2:
The liquid collection tray acts as an intermediary between the lower wet FGD section and the upper packed bed section. It collects the caustic solution, allows sulfur removal through reaction with calcium compounds, and prevents solids from entering the packed bed, thereby preventing plugging while maintaining deep SOx capture efficiency
3Manufacturing precision
If new concepts in FGD are implemented to achieve 99.6% removal efficiency, then emission standards are met, but capital and operating costs may increase
Solution Approach 1:
The system uses partial action by having the lower wet FGD section handle the bulk of SOx removal (coarse removal), and the upper packed bed section handle only the remaining trace amounts (deep capture). This avoids the excessive cost of using a single high-performance system for the entire removal task, achieving cost-effective compliance with stringent standards
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 integrated system achieves deep SOx capture efficiency exceeding 99.6% while maintaining cost-effectiveness, effectively meeting stringent emission standards and reducing operational costs, as demonstrated by pilot-scale experiments.
Implementation Method 1
a second circuit for circulating a second, caustic solution through the upper section and the packed bed unit
Implementation Method 2
the acid gas is absorbed into the liquid and reacts with the base to form a neutral insoluble calcium salt
Implementation Method 3
utilizing a caustic solution with soluble calcium compounds and alkali reagents to enhance SOx capture efficiency and prevent fouling, scaling, or plugging in the packed bed
Implementation Method 4
A liquid collection tray divides that reaction chamber into an upper section and a lower section
Data Source
AI summary
An apparatus is provided for removing sulfur oxides from a flue gas stream. That apparatus includes an absorber tower having an upper section and a lower section. A packed bed unit is provided in the upper section of the absorber tower. A first recycling circuit is provided for recycling lime water to the lower section of the absorber. Further the apparatus includes a second recycling circuit for recycling caustic solution to the packed bed unit.