Surveillance of De-NOx

For control and surveillance of the De-NO_x plant, it is usually recommended to measure NO (possibly NO_x), NH₃ and H₂O before and after the De-NO_x reactor.

The purpose of these measurements is to reduce the consumption of raw materials, reduce NO_x emission and to minimise and monitor the emission rate of NH₃. The reason for measurement of H₂O is to convert the results to dry condition (reference state).

The measurement of NH₃ is either made from the emission measurement system or from a stand-alone analyser placed just after the reactor (where NH₃ is added to the process). If measurement of NH₃ is part of the control of the De-NO_x process, it is not always recommended to place it with the equipment for emission measurement due to the rather long response time.

In waste incineration plants with a multi component emission measurement system such as ABB ACF-NT FTIR analysis system, it is obvious to implement the NH₃ measurement into the analysis system unless there are legal demands for short response times. This is a cheap solution and all measurements have been gathered into one system.

For measurements with short response times, an in-situ NH₃ monitor based on the laser light principle (single line spectroscopy) is often used. The laser gas monitors are noted for very short response times and can be used with high dust loads and high temperatures.

• Measurement of NO with an extractive analysis system such as GASloq 600 with an ABB NO analyzer named Uras 14; or with the existing emission measurement system
• Measurement of NH₃ with an in-situ measurement system such as NEO Monitors LaserGas Monitor; or with an existing emission monitoring system.
• Measurement of H₂O integrated into the NH₃-monitor; either by a laser gas monitor or by an emission measurement system
• Demands for a reliable measurement in high temperatures and high dust loads
• Demands for short response times for operation purposes