Hong Liu, Chen De-zhen, Wang Du, Huang Su
Thermal & Environmental Engineering Institute, Tongji University, Shanghai 200092, China.
Huan Jing Ke Xue. 2012 Aug;33(8):2901-8.
The kinetic mechanism of NOx reduction with hydrazine hydrate in selective non-catalytic reduction (SNCR) process was studied and verified by the experimental results, the dominant radicals and reactions were confirmed through sensitivity analysis and key parameters in SNCR process have been obtained. The results of numerical simulation based on the proposed mechanism showed that the effective temperatures for SNCR de-NOx process were bimodal distribution with the optimum temperatures being 650 degrees C and 975 degrees C respectively and the lower temperature window fell in the range of 597-747 degrees C; while the experimental results proved the bimodal distribution of effective temperature with peak values being 653 degrees C and 968 degrees C respectively and the lower temperature window was within the range of 587-707 degrees C for hydrazine-based SNCR process, Simulation results and experimental results matched well with respect to reaction behaviors versus temperature. Through sensitivity analysis it had been found that the most effective reaction to reduce NO was the decomposition reaction of N2H4 to NH2 and the most helpful radical was NH2. Compared to ammonia the temperature window of hydrazine-based SNCR process on the lower temperature side is more flexible for application. Decreased O2 concentration would move the temperature window to the right side, which was contrary to that of ammonia; while increased n(N2H4)/n(NO) moved the temperature window to the left side and NO, reduction efficiency was also improved. All of these results showed that hydrazine has lower temperature window than those traditional de-NOx reagents and it will be widely used in application of SNCR as a potential reductant for NOx reduction.
研究了选择性非催化还原（SNCR）过程中水合肼还原氮氧化物的动力学机理，并通过实验结果进行了验证，通过敏感性分析确定了主要自由基和反应，得到了SNCR过程中的关键参数。基于所提出机理的数值模拟结果表明，SNCR脱硝过程的有效温度呈双峰分布，最佳温度分别为650℃和975℃，较低温度窗口在597 - 747℃范围内；而实验结果证明了基于水合肼的SNCR过程有效温度的双峰分布，峰值分别为653℃和968℃，较低温度窗口在587 - 707℃范围内，模拟结果与实验结果在反应行为与温度的关系方面匹配良好。通过敏感性分析发现，还原NO最有效的反应是N2H4分解为NH2的反应，最有帮助的自由基是NH2。与氨相比，基于水合肼的SNCR过程在较低温度侧的温度窗口在应用上更灵活。O2浓度降低会使温度窗口向右移动，这与氨的情况相反；而n(N2H4)/n(NO)增加会使温度窗口向左移动，且NO还原效率也提高。所有这些结果表明，水合肼的温度窗口比那些传统脱硝试剂更低，作为一种潜在的氮氧化物还原还原剂，它将在SNCR应用中得到广泛应用。
