Nitrogen oxides (NOx) are one of the main components of air pollution. 70% of the emissions of nitrogen oxides in China come from the direct combustion of coal, while the power industry, iron making industry, sintering industry, cement industry are also Large coal producers are one of the main sources of NOx emissions. In recent years, China's nitrogen oxide emissions have risen rapidly with the rapid growth of energy consumption. Statistics show that the total amount of nitrogen oxides emitted by thermal power plants in China has increased to 8.4 million tons in 2007. According to expert predictions, if not controlled, the total emissions of nitrogen oxides in China will reach 14.52 million tons in 2020.
Flue gas denitrification technology is one of the main methods for controlling nitrogen oxide emissions in China. At present, the selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) flue gas denitrification, which are widely used at home and abroad and have a mature process, require the injection of reducing agent ammonia into the flue gas to make the flue gas Nitrogen oxides are reduced to nitrogen. In order to ensure the full reaction of nitrogen oxides and avoid new pollution caused by excessive ammonia, real-time monitoring and analysis of NH3 escape is needed to achieve the optimization of the ammonia injection of the reducing agent and improve the denitration efficiency. Installing an online laser ammonia escape gas analysis system to monitor the ammonia content before and after denitrification is an effective basis for implementing the control of NH3 escape, thereby avoiding corrosion and damage to downstream equipment.
Significance of ammonia slip detection
• The escaped ammonia causes waste of funds and environmental pollution;
• Ammonia escape will corrode the catalyst module, causing catalyst deactivation (ie failure) and blockage, greatly shortening the catalyst life;
• The escaped ammonia gas will generate ammonium sulfate (corrosive and sticky) with the SO3 in the flue gas, which will block and corrode the heat storage element of the air preheater located downstream of the denitrification;• Excessive escape ammonia will be absorbed by fly ash, making fine ash (grey brick) unsaleable;