Wet Flue Gas Desulfurization ORP Control
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Solution Overview
Problem
The wet type flue gas desulfurization apparatus faces challenges in controlling the oxidation-reduction potential (ORP) when the amount of oxidation air supplied is reduced to zero, leading to peroxidized states, which can result in gypsum quality deterioration, heavy metal ion oxidation, and increased mercury re-scattering, requiring effective ORP management to maintain desulfurization performance and prevent metal mercury generation.
Innovation Solution
The apparatus includes an ORP meter, a reducing additive supplying unit for sodium thiosulfate, sodium metabisulfite, or sodium dithionite, and an oxidizing additive unit, which adjust the ORP by supplying reducing or oxidizing additives based on measured values to maintain an appropriate range of 50 mV to 200 mV, preventing peroxidation and mercury re-scattering, and ensuring stable desulfurization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the amount of oxygen-containing gas introduced into the absorbent storing unit is increased to maintain high conversion rate from calcium sulfite to gypsum, then the desulfurization performance is improved, but the running cost increases and peroxides are generated causing wastewater quality deterioration
Solution Approach 1:
The patent employs ORP (oxidation-reduction potential) measurement as a feedback mechanism to monitor the oxidation state of the absorbent in real-time. Based on the measured ORP value, the control system automatically adjusts the amount of oxygen-containing gas supplied to the absorbent storing unit, thereby maintaining optimal oxidation conditions while preventing peroxide generation. This closed-loop control ensures high conversion rate of calcium sulfite to gypsum without excessive oxygen introduction.
2Object-generated harmful factors
If the amount of oxygen-containing gas is reduced to adjust peroxide generation, then wastewater quality is improved, but the conversion rate from calcium sulfite to gypsum decreases and desulfurization performance deteriorates
Solution Approach 1:
The ORP meter continuously monitors the oxidation-reduction potential of the absorbent, providing real-time feedback on the oxidation state. When the ORP value indicates insufficient oxidation (low conversion rate), the control system increases oxygen supply. When the ORP value indicates excessive oxidation (peroxide generation risk), the system reduces oxygen supply. This dynamic feedback control resolves the contradiction by maintaining the optimal balance between conversion rate and peroxide prevention.
3Object-generated harmful factors
If oxidation air supply is reduced to zero to control ORP, then peroxide generation is prevented, but sulfurous acid cannot be sufficiently oxidized and ORP control becomes difficult
Solution Approach 1:
The patent utilizes natural oxidation that occurs through contact between the flue gas and the absorbent in the absorber as a self-service oxidation mechanism. This natural oxidation process continues to convert sulfurous acid to gypsum even when external oxygen supply is reduced to zero, preventing peroxide generation while maintaining ORP control stability. The system leverages the inherent oxidation capacity of the flue gas-oxygen to maintain reliable 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
This solution effectively controls the ORP within a stable range, preventing excessive oxidation, maintaining gypsum quality, and reducing mercury re-scattering, thereby ensuring stable and efficient desulfurization operations while preventing metal mercury formation and corrosion.
Implementation Method 1
an oxidizing agent is supplied into the absorbent storing unit to oxidize sulfurous acid
Implementation Method 2
a reducing additive supplying unit for supplying at least one of sodium thiosulfate, sodium metabisulfite, and sodium dithionite as a reducing additive
Implementation Method 3
an oxidation-reduction potential meter that measures an oxidation-reduction potential of the absorbent
Implementation Method 4
an absorber that removes sulfur oxide in a flue gas with an absorbent
Data Source
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AI summary
Provided is an absorber 11 that removes sulfur oxide in a flue gas with an absorbent 14, an absorbent storing unit 11b that stores the absorbent that has absorbed the sulfur oxide, an oxidation-reduction potential meter 18 that measures an oxidation-reduction potential of the absorbent 14, a reducing additive supplying unit 20 that supplies a sulfur oxoacid reducing additive 19 into the absorbent 14 or the absorbent storing unit 11b, and a control device 50 that controls the reducing additive supplying unit 20 based on a measured value of the oxidation-reduction potential of the absorbent 14 measured with the oxidation-reduction potential meter 18, wherein the control device 50 controls the reducing additive supplying unit 20 to supply the sulfur oxoacid reducing additive 19 when the measured value of the oxidation-reduction potential has exceeded an upper limit of an appropriate range of the oxidation-reduction potential.