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Flue Gas Desulfurization Process |
In flue gas desulfurization systems that use magnesium hydroxide (Mg(OH)2) slurry, the consumption of the desulfurization agent (Mg(OH)2) is controlled by using online pH analyzers. A great concern in the pH measurement is heavy staining of the pH electrodes by the Mg(OH)2 slurry. To ensure accurate measurement, frequent cleaning of the electrodes with an acid is required, adding to both maintenance workload and cost.
The FLXA AUTO CLEAN chemical cleaning system automates the acid cleaning process, which not only saves both time and expense but also ensures precise pH measurement over long periods.
Expected Benefits
In the flue gas desulfurization system, Mg(OH)2 is used as the absorbent to remove sulfur dioxide (SO2) from the flue gas.
Absorption reaction 1: Mg(OH)2 + SO2 ->MgSO3 + H2O
Absorption reaction 2: MgSO3 + SO2 + H2O -> Mg(HSO3)2
After absorbing SO2, the solution undergoes pH adjustment, oxidation, and filtration for detoxification before discharge.
pH adjustment: Mg(HSO3)2 + Mg(OH)2 -> 2MgSO3 + 2H2O
Oxidation: MgSO3 + 1/2O2 -> MgSO4
Measurement System & Operation Outline
Field Data
When performing pH measurement in a flue gas desulfurization system with Mg(OH)2 slurry, the electrodes tend to become heavily stained by the slurry. The cleaning of the electrodes and the reduction of maintenance time and cost are key points to consider when selecting a pH analyzer for the system.
pH System with Chemical Cleaning | General pH Analyzer | |
---|---|---|
Cleaning | "Automatic acid cleaning: 2 or 3 times/day, user programmable Manual acid cleaning: approx. monthly" | "Manual acid cleaning: once/day" |
Calibration | Manual calibration: weekly | "Manual 2-point calibration: weekly" |
Other maintenance | Replenishment of chemical tank: approx. every 2 months | - |
Acid cleaning is done with a 4% hydrochloric acid solution.
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The FLEXA™ series analyzers are used for continuous on-line measurements in industrial installations. With an option for single or dual sensor measurement, they are the most flexible two-wire analyzer available.
The FLEXA™ series analyzers are used for continuous on-line measurements in industrial installations. With an option for single or dual sensor measurement, they are the most flexible two-wire analyzer available.
The FLEXA™ series analyzers are modular-designed analyzers used for continuous online measurements in industrial installations. They offer single or multi-sensor measurement.
Yokogawa's pH and ORP analyzers are highly reliable. They feature advanced functions and are useful for a wide variety of applications including water quality management in a broad range of production processes and in medium-sized wastewater treatment plants, or as general pH and ORP control systems.
pH and ORP meters, analyzers and transmitters are used for continuous process monitoring of pH and ORP to ensure water/product quality, monitor effluent discharge, batch neutralization, pulp stock, scrubbers, cooling towers, chemical, water/wastewater treatment and many other applications.
pH electrodes and sensors are the sensing portions of a pH measurement. Various installation options including retractable, flow thru, immersion, and direct insertion. Proper pH electrode/sensor selection is critical for optimal measurement results.
Contact a Yokogawa Expert to learn how we can help you solve your challenges.