SCR系统尿素沉积物内相关组分动力学试验研究

Kinetic study on related components in urea deposits of SCR system

为完善尿素沉积物生成机理模型,对尿素沉积物进了热解特性试验研究。由TG-DSC曲线表明,尿素沉积物主要分3个阶段进行分解:第一阶段为尿素与缩二脲的分解,第二阶段为未知组分之间的形成与分解,第三阶段为三聚氰酸及其同系物的分解。采用Doyle积分法分析TG曲线可以得出6个温度区间的拟合曲线,拟合度接近直线,一级动力学反应机理假设合理,并计算出各个区间的活化能和指前因子。研究结果表明,采用Doyle积分法可获得各分解反应的指前因子与活化能近似值,试验与量子化学计算方法分解反应的化学反应速率参数对比,失重阶段中沉积物内部组分分解以及各组分比例表明沉积物的主要组分为三聚氰酸,此方法也可为今后SCR系统尿素沉积物内部组分动力学参数的获取提供试验可行方案。

The pyrolysis characteristics of urea deposits were tested to improve the model of urea deposits formation mechanism.The TG-DSC curves show that the urea deposits are mainly decomposed in three stages:the decomposition of urea and biuret,the formation and decomposition between unknown components,and the decomposition of cyanic acid and its homologues.By using the Doyle integral method to analyze the TG curve,the fitting curves of six temperature intervals can be obtained.The fitting degree is close to a straight line,then the first-order kinetic reaction mechanism is reasonable.The activation energy and the pre-exponential factor of each interval can be calculated.Results indicate that the Doyle integral method can obtain the pre-exponential factor and activation energy approximation of each decomposition reaction.Compared with quantum chemical calculation methods in chemical reaction rate parameters,the main component is cyanuric acid in the internal components of the deposit at the weight loss stage.This method can also provide a feasible solution for the acquisition of the internal component kinetic parameters of the urea deposit in the SCR system.