Introduction
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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
- Improves the efficiency of a flue gas desulfurization system with Mg(OH)2 slurry
- Ensures stable, continuous pH measurement
- Reduces operating costs
- Eliminates manual cleaning
Process Overview
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
Solution Details
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.
Industries
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Chemical
Chemical plants rely on continuous and batch production processes, each posing different requirements for a control system. A continuous process calls for a robust and stable control system that will not fail and cause the shutdown of a production line, whereas the emphasis with a batch process is on having a control system that allows great flexibility in making adjustments to formulas, procedures, and the like. Both kinds of systems need to be managed in available quality history of product, and to be able to execute non-routine operations. With its extensive product portfolio, experienced systems engineers, and global sales and service network, Yokogawa has a solution for every plant process.
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Power
In the mid 1970s, Yokogawa entered the power business with the release of the EBS Electric Control System. Since then, Yokogawa has steadfastly continued with the development of our technologies and capabilities for providing the best services and solutions to our customers worldwide.
Yokogawa has operated the global power solutions network to play a more active role in the dynamic global power market. This has allowed closer teamwork within Yokogawa, bringing together our global resources and industry know-how. Yokogawa's power industry experts work together to bring each customer the solution that best suits their sophisticated requirements.
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Specialty & Fine Chemical
Yokogawa has long served customers in the specialty and fine chemicals market. With a market leading batch solution that offers the best in class reliability and flexibility as well as industry experts who understand the complex requirements in designing a batch solution, you can be assured that in your partnership with Yokogawa you will have a system that will enable you to produce products that meet your customers’ needs in the future while maintaining safety and regulatory compliance.
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Thermal
Thermal power using coal, oil or gas as fuel accounts for the majority of electric generation throughout the world.
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