SCR脱硝系统性能及空气预热器阻力上升分析

NO_x排放浓度、氨逃逸浓度难以控制及空气预热器阻力上升，是SCR脱硝系统超低排放改造中遇到的主要问题。以某SCR脱硝系统超低排放改造后的300 MW 机组为研究对象，通过测试得知：（1）SCR反应器出口NO_x分布不均，氨逃逸浓度超标严重，氨逃逸监测表计示值不具代表性，造成NO_x排放浓度控制困难和空气预热器阻力上升；（2）过度追求NO_x超低排放浓度，造成催化剂活性、主要化学成分明显衰减，硫酸氢铵在其表面沉积严重。对此提出的改进措施为：进行NO_x浓度烟气在线监测系统（CEMS）多点取样改造，定期进行喷氨优化和催化剂性能检测，以改善SCR系统运行效果和提高运行的经济性。

Analysis and Research on SCR System Performance and Resistance Increase of Air Preheater in Ultra-Low Emission Unit

Some major problems were encountered such as the difficulties to control NO_x emission concentration and ammonia escape concentration as well as the resistance increase of air preheater during the transformation of SCR denitrification system for ultra-low emission. In this paper, an SCR System of 300 MW unit after the ultra-low retrofit was selected for study purpose. The testing results are summarized as follows: (1) The NO_x at the outlet of unit denitrification was unevenly distributed. However, since the ammonia escape concentration limit was severely exceeded and the on-line ammonia escape monitoring meter readings were no longer eligible to represent the right values, NO_x concentration control would become more difficult and the increase of the resistance of the air preheater had been observed. (2) Excessively pursuing the ultra-low NO_x emission concentration may result in the drastic attenuation of the catalyst activities and some main chemical components. Then eventually severe deposition of ammonium bisulfate comes up on its surface. Therefore corresponding improvement plans are proposed. CEMS multi-point sampling transformation at denitrification outlet should be carried out to monitor NO_x concentration after ultra-low emission transformation. Both the ammonia injection optimization adjustment and the catalyst performance testing should be done on a regular basis to improve the effect of SCR denitrification device and the economy of denitrification operation.