Sulfite Control System for Flue Gas Desulfurization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wet flue gas desulfurization (WFGD) systems, controlling sulfite oxidation is difficult due to challenges in measuring sulfite concentration, leading to excessive oxygen supply, which reduces efficiency and oxidizes all sulfites to sulfates, thereby missing the benefits of maintaining sulfites in the slurry.
Innovation Solution
A WFGD system with a sulfite control system that includes a tank for receiving partially reacted slurry, an oxygen-containing gas inlet for controlled dispersion, a sensor to measure sulfite concentration, and a controller to adjust oxygen flow based on measurements to maintain a low sulfite concentration, thereby reducing nitrate and nitrite levels in the purge stream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If forced oxidation is used to ensure complete sulfite conversion to sulfate, then gypsum production is maximized, but energy consumption increases due to excessive oxygen supply
Solution Approach 1:
The patent employs a feedback control system using sulfite sensors to monitor sulfite concentration in the slurry and automatically adjusts oxygen supply accordingly. This closed-loop control ensures sufficient sulfite oxidation for gypsum production while preventing excessive oxygen consumption, directly resolving the contradiction between productivity and energy use.
Solution Approach 2:
Instead of applying full oxidation continuously, the system applies partial oxidation only when sulfite concentration exceeds predetermined thresholds. This selective application of oxidation eliminates unnecessary energy consumption while maintaining adequate sulfite conversion for gypsum production.
2Quantity of substance
If forced oxidation is used to convert all sulfites to sulfates, then sulfite concentration is reduced to zero, but the benefits of maintaining sulfites in the slurry are lost
Solution Approach 1:
The system intentionally maintains partial sulfite concentration rather than achieving complete oxidation. By controlling oxygen supply to keep sulfite levels within a target range (5-80 ppm), the system preserves the beneficial effects of sulfites while preventing their excessive accumulation, thus maintaining system efficiency.
Solution Approach 2:
The patent changes the oxidation parameter from complete conversion (100% sulfite to sulfate) to partial conversion (maintaining 5-80 ppm sulfite). This parameter adjustment optimizes the balance between sulfite removal and system efficiency, allowing the slurry to retain beneficial sulfite concentrations.
3Ease of operation
If sulfite concentration is not monitored and controlled, then oxygen supply cannot be optimized, but implementing monitoring increases system complexity
Solution Approach 1:
The system integrates sulfite sensors and automated control to provide real-time feedback on sulfite concentration. This enables automatic optimization of oxygen supply without requiring manual intervention, simplifying operation despite the added sensing and control infrastructure.
Solution Approach 2:
The control system automatically adjusts oxygen supply based on sulfite sensor readings without requiring continuous operator attention. The system serves itself by autonomously optimizing oxidation based on measured sulfite levels, reducing operational complexity.
4Quantity of substance
If excessive oxygen is supplied to ensure complete sulfite oxidation, then nitrate and nitrite levels remain high, but reducing oxygen supply improves nitrate and nitrite removal
Solution Approach 1:
The feedback control system monitors sulfite concentration and adjusts oxygen supply to maintain it within the optimal range (5-80 ppm). This precise control ensures sufficient sulfite oxidation for reliability while limiting excess oxygen that would otherwise promote nitrate and nitrite formation, thus achieving both goals simultaneously.
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 reduces total nitrates and nitrites by more than 50% while maintaining a low sulfite concentration, improving system efficiency and compliance with regulatory standards, and reduces the need for costly biological treatment steps.
Implementation Method 1
a sensor operable to measure a sulfite concentration of the at least partially reacted slurry in the tank to obtain a sulfite concentration measurement
Implementation Method 2
The inlet for receiving the oxygen-containing gas is operable for dispersing at least a portion of the oxygen-containing gas supplied to the tank through at least a portion of the at least partially reacted slurry contained within the tank
Implementation Method 3
adjusting a flow rate of the oxygen-containing gas into the tank based at least in part on the sulfite concentration measurement to adjust oxidation of the one or more sulfites contained within the reacted slurry
Implementation Method 4
effective reacted slurry nitrates and nitrites reduction
Data Source
AI summary
A system and method of using the system for controlling oxidation of sulfites to reduce total nitrite and nitrate levels in a slurry is disclosed. The system includes a tank having an inlet for receiving a slurry produced in a wet flue gas desulfurization process. The tank also includes an inlet for receiving a gas. The inlet for receiving the gas is operable to disperse at least a portion of the gas received in the tank through at least a portion of the slurry received in the tank. A sensor is configured to measure a sulfite concentration of the slurry received in the tank to obtain a sulfite concentration measurement. In some embodiments, the sensor is a sulfite analyzer. In other embodiments, the sensor is a virtual analyzer. The system also includes a controller. Software executing on the controller generates an electronic signal affecting an adjustment of a flow rate of gas into the slurry in the tank based at least in part on the sulfite concentration/sulfite concentration measurement.