Moistened Fly Ash Injection for WFGD Purge Liquid Recovery
Solution Overview
Problem
Wet flue gas desulfurization systems generate significant purge liquid that requires costly wastewater treatment, leading to increased operational and capital expenses due to corrosion issues from chloride and fluoride ions, and necessitates large facilities.
Innovation Solution
A method where fly ash is removed from the flue gas stream, combined with purge liquid to form moistened fly ash, and injected back into the flue gas stream upstream of the particle collector, reducing the need for wastewater treatment by utilizing the alkaline particles to remove contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If purge liquid is used to maintain desired chloride concentration and protect equipment from corrosion, then equipment reliability is improved, but the amount of liquid requiring expensive wastewater treatment increases
Solution Approach 1:
The patent recovers purge liquid that would otherwise be discarded to wastewater treatment facilities. The liquid is sprayed onto fly ash in a silo, allowing reuse of the liquid's alkaline properties for neutralizing acidic gases while the fly ash absorbs the liquid. This eliminates the need to discharge the liquid to wastewater facilities while maintaining corrosion protection.
Solution Approach 2:
Fly ash serves as an intermediary medium between the purge liquid and the flue gas stream. The liquid is applied to the fly ash, which then becomes a carrier that can be injected into the flue gas. This intermediary approach allows the purge liquid to continue functioning for corrosion protection while eliminating the need for wastewater treatment discharge.
2Object-affected harmful factors
If wastewater treatment facilities are implemented to treat purge liquid, then environmental compliance is improved, but capital and operating costs increase dramatically
Solution Approach 1:
The patent converts the harmful purge liquid that requires expensive treatment into a beneficial reagent. By spraying the liquid onto fly ash, the alkaline components neutralize acidic gases (SOx, HCl, HF) in the flue gas stream. The harmful waste liquid becomes a useful contaminant removal agent, eliminating the need for wastewater treatment facilities.
Solution Approach 2:
The system uses its own purge liquid to treat the flue gas stream, making the system self-sufficient. The liquid that would normally require external wastewater treatment facilities is instead reused within the desulfurization system itself to remove contaminants, eliminating dependency on external treatment infrastructure.
3Reliability
If more purge liquid is discharged to maintain low chloride concentration, then corrosion protection is improved, but the cost and land requirement for wastewater treatment facilities increase
Solution Approach 1:
Instead of discarding purge liquid to wastewater facilities requiring large land areas, the system recovers and reuses the liquid by spraying it onto fly ash. This eliminates the need for land-intensive wastewater treatment facilities while maintaining corrosion protection through continued chloride concentration control.
4Productivity
If organic acids are used in the WFGD system to enhance SOx removal, then desulfurization efficiency is improved, but the cost and complexity of wastewater treatment facilities increase dramatically
Solution Approach 1:
Organic acids that would normally require expensive biological treatment are converted into a beneficial reagent. When sprayed onto fly ash, these organic acids enhance the neutralization of acidic gases in the flue gas stream. The harmful organic contaminants become useful additives that improve desulfurization and盐酸 removal efficiency.
Solution Approach 2:
The system uses organic acids internally to treat the flue gas stream, making the system self-sufficient. The organic acids that would normally require external biological reactors are instead used within the desulfurization process itself to enhance contaminant removal, eliminating the need for separate biological treatment facilities.
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 decreases the amount of purge liquid sent to wastewater treatment plants, reduces the need for fresh alkaline reagents, and enhances contaminant removal efficiency while minimizing corrosion and equipment damage.
Implementation Method 1
the moistened fly ash removes at least a portion of contaminants present in the flue gas stream
Implementation Method 2
utilizing the alkaline particles to remove contaminants
Implementation Method 3
the slurry reacts with sulfur oxides (SOx) present in the flue gas and removes them from the flue gas stream as precipitated compounds
Implementation Method 4
removing fly ash from a flue gas stream utilizing a particle collector
Data Source
AI summary
One aspect of the invention relates to a method for removing contaminants from a flue gas stream (22). The method includes: removing fly ash from a flue gas stream (22) utilizing a particle collector (24); contacting the flue gas stream with an alkaline reagent in a wet scrubber (26); discharging a purge liquid (30) from the wet scrubber (26); combining at least a portion of the purge liquid (30) with at least a portion of the fly ash (48) to form moistened fly ash (60); and injecting at least a portion of the moistened fly ash (60) into the flue gas stream (22) upstream of the particle collector (24), whereby the moistened fly ash (60) removes at least a portion of contaminants present in the flue gas stream (22).