烟气脱硝用尿素水解制氨工艺试验研究

Experimental Investigation on the Ammonia Production Process with Urea Hydrolysis for Flue Gas Denitration

为了掌握烟气脱硝用尿素水解制氨工艺的放大规律,通过建立中试装置来模拟工业反应器的传递过程,对尿素水解工艺开展了中试及工业化放大试验研究。结果表明,尿素溶液在一定温度、压力下发生水解反应生成氨气、二氧化碳和水蒸气的混合气,气液相平衡可采用修正的LewisRandall方程和Herry方程分别描述。当操作温度为150℃时,反应-扩散准则数M为0.036,表明尿素水解制氨为液相慢反应,本征反应速率远小于氨气扩散速率,反应器的产氨速率由动力学控制,可简化为温度和反应平衡常数的函数;水解反应器内加热蒸汽发生冷凝换热,液相区则产生泡核沸腾;根据中试试验数据建立的表观动力学模型,可用于指导工业反应器的结构设计。该研究将为烟气脱硝用尿素水解制氨工艺开发及反应器放大设计提供重要参考。

In this research a pilot plant was established to simulate the transfer process in industrial reactor,and then preproduction and industrial tests were carried out.The results indicated that the urea solution was hydrolyzed to a mixture of ammonia,carbon dioxide and water vapor at certain temperature and pressure.The modified Lewis-Randall equation and Herry equation were adopted to describe the phase equilibrium between the vapor and liquid phases.When the operating temperature was 150 ℃,the reaction-diffusion criterion number M was0.036,which indicated that the urea hydrolysis in liquid was a slow reaction and the intrinsic reaction rate was much lower than the diffusion rate of ammonia.The ammonia production rate of the reactor was dominated by dynamics and could be simplified as a function of temperature and reaction equilibrium constant.In the tank reactor,the heating steam condensed in the pipe while the nucleate boiling occurred in the liquid region.The ammonia production rates of the industrial hydrolysis reactor agreed well with the theoretical values deduced from the apparent dynamic model,and satisfied the ammonia consumption requirement for flue gas denitration in the selective catalytic reduction.This study would provide a reference to the design and developmentof urea hydrolysis for flue gas denitration.