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Prediction System of Denitrification

Prediction System of Denitrification

Overview

A proprietary denitrification device from Mitsubishi Power which uses ammonia as a reducing agent is used in thermal power plants. Nitric monoxide (NO) and NH₃ react and decompose to nontoxic nitrogen （N₂）and water（H₂O）.
This denitrification device requires highly efficient control over denitrification to eliminate unreacted NH3 in consideration of environment and costs.

A prediction system for denitrification from Mitsubishi Power combines a proprietary prediction/control method for denitrification and a quick-response zirconia-based NOx (nitrogen oxide) meter to offer optimal control over NH₃ supply when the load, NOx concentration, and other conditions fluctuate.

Features

Quick-response zirconia-based NOx meter
The 90 percent response time of the conventional CLD type NOx meter is about 60 seconds, In the case of the zirconia-based NOx meter, it is about 14 seconds.

Response Time between Zirconia type and CLD

Appearance of Prediction System of Denification

Appearance of Prediction
System of Denitrification

Model based predictive control
The system has a dynamic model for the denitrification reactor. It simulates the behavior of the denitrification reactor (controlled object), predicts the controlled variable (output of the controlled object), and determines the control input based on the predicted value.
- Improving the steady-state characteristics
  Even if the characteristics of the denitrification device change, the steady-state characteristics can be maintained.
- Improving the transient characteristics
  Predictive injection of NH3 improves the transient characteristics.

Nox-NH₃ Sensor of Zirconia type

Measurement example

Example of basic measurement using a NOx sensor

Operating principle

Theory of operation of a NOx sensor

NH3共存下のNOx及び、NH3の測定原理

Theory of measurement of NH₃, and that of NOx coexistent with NH₃

System Configuration

System structure of the denitrification prediction system

Characteristics

The result of the response comparison test between the zirconia-based NOx sensor and the CLD type NOx sensor is as follows. Compared to the CLD type, response time has been successfully improved by about one minute.

The result of the response comparison test between the zirconia-based NOx sensor and the CLD type NOx sensor