A supercritical unit of a power plant adopts the selective catalytic reduction flue gas denitrification technology, that is, in the temperature range of 305 to 420 °C, an appropriate amount of ammonia gas is injected into the high temperature flue gas. The NOx in the original flue gas is fully reacted to eventually generate harmless nitrogen and water. In order to improve the efficiency, the denitration system should inject enough ammonia gas, so there is a possibility that the ammonia gas reaction is not completely then escaped. Ammonia escape will lead to problems such as blockage and corrosion of air preheater, increase of flue gas resistance loss, and loss of reducing agent, which affects enterprise benefits.

In order to ensure the full reaction of nitrogen oxides and avoid the waste of ammonia gas and damage to equipment caused by excessive ammonia injection, it is necessary to conduct real-time monitoring and analysis of ammonia escape to optimize the injection amount of ammonia gas.

Our laser analyzer adopts high-temperature heat tracing extraction technology to continuously monitor the gas to be measured in the flue gas. The system consists of three parts: sampling and transmission unit, preprocessing and control unit, and analysis unit, which are mainly used in many industrial fields for example: coal-fired power plants, aluminum plants, steel plants, smelters, waste-to-energy plants, cement and chemical plants, glass plants, etc. The analyzer adopts TDLAS technology (Tunable Diode Laser Absorption Spectroscopy), which is one of the most advanced gas measurement methods in the world. The instrument has the advantages such as high sensitivity, fast response speed, no background gas interference and non-contact. It provides a reliable reflecting the changes of the gas to be measured in real time.

At present, the on-line ammonia escape monitoring system for flue gas of power plant units is running stably, which greatly improve our efficiency.