TN and NOx Measurement for a Denitration System

Importance of the Topic

Denitration systems in thermal power plants mitigate harmful NOx emissions to meet environmental regulations and improve air quality.
Monitoring the nitrogen content in urea solutions is essential to optimize reaction efficiency and prevent ammonia slip.

Objectives and Study Overview

This study demonstrates a rapid, reagent-free method for determining total nitrogen (TN) in urea solutions using Shimadzu TOC analyzers equipped with a TN measurement option.
Continuous monitoring of NOx concentrations at the denitration system outlet is also explored to ensure system performance.

Methodology and Instrumentation

Urea solutions at concentrations of 10%, 20%, 30%, 40%, and 50% were prepared by dissolving powdered urea in pure water. High-concentration samples were automatically diluted prior to analysis.
A two-point calibration curve was generated using potassium nitrate standards (0 and 30 mgN/L).

• TOC-LCPH with TNM-L total nitrogen unit
• TOC-4200 on-line TOC analyzer with TN option
• NOA-7100 transportable gas analyzer for NOx measurement (thermal decomposition–chemiluminescence)
• Catalyst for complete combustion in TN analysis

Main Results and Discussion

Measured TN values matched theoretical concentrations with recovery rates ranging from 99% to 105% and a correlation coefficient of 0.9997.
Continuous NOx monitoring at the denitration outlet confirmed system efficiency and supported real-time process adjustments.

Benefits and Practical Applications

The thermal decomposition–chemiluminescence TN method eliminates the need for acids and alkalis, reducing analysis time to about 5 minutes.
Integration of TOC-based TN measurement with NOx analysis allows comprehensive quality control of urea reagents and optimization of denitration system operation.

Future Trends and Opportunities

Advancements in online sensor integration, wireless data transmission, and predictive analytics will further enhance process control and preventive maintenance.
Linking analytical data to digital plant management platforms can improve environmental compliance and operational efficiency.

Conclusion

Shimadzu’s TOC-based TN measurement provides accurate, rapid, and reagent-free analysis of urea solutions, enabling efficient denitration and continuous NOx emission monitoring.

References

Ikezawa Y. TN and NOx Measurement for a Denitration System. Shimadzu Corporation; Application No. O68; First Edition: May 2018.