选择性催化还原服役后催化剂活性及动力学实验研究

Experimental Study on Activity and Kinetics of Served SCR Catalysts

以NH3为还原剂,在选择性催化还原催化剂活性检测实验台上考察了典型催化剂服役前后在不同温度和氨氮比下的脱硝效率,分析了催化剂服役后的活性变化规律。采用E-R机制建立的速率方程对实验数据进行回归,得到了典型催化剂服役前后的表观动力学参数,并分析了催化剂失活的原因。研究结果表明:催化剂服役前后的脱硝效率和活性随温度的变化趋势一致,服役后催化剂的活性明显下降;催化剂服役前的脱硝表观活化能比服役后的小,催化剂服役前的表观指前因子比服役后的大,但催化剂服役前的NH3均衡速率常数的表观活化能和表观指前因子均比服役后的大。通过波纹板催化剂失活分析可以推断波纹板催化剂失活的主要原因是催化剂服役后活性成分的流失、灰分沉积造成堵塞以及灰分沉积后有毒元素对催化剂的毒害。

The DeNOx efficiencies of two typical SCR catalysts before and after service were examined with NH3 as a reducing agent under different temperatures and NH3/NO ratios on the experimental platform for SCR catalyst activity detection. The activity variation of catalysts after service was analyzed. The apparent kinetic parameters of the catalysts before and after service were calculated through the experimental data fitting with the reaction rate equation based on Eley-Rideal mechanism. The reason for catalyst deactivation was analyzed. The results show that the variation tendencies of DeNOx efficiency and activity with the change in temperature exhibit the same before and after service, with the activity of catalyst declining obviously. The DeNOx apparent activity energy of the catalysts before service is smaller than that of the catalysts after service; the pre-exponential factor of the catalysts before service is higher than that of the catalysts after service; but both apparent activity energy and pre-exponential factor of NH3 equilibrium rate constant of catalysts before service are higher than those of the catalysts after service. The reasons for catalyst deactivation mainly are the loss of active component of catalyst after service, the blocking of ash and the poison of toxic element in the ash.