Experimental investigation on the ammonia production process with urea hydrolysis for flue gas denitration

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 was 0.036, 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 development of urea hydrolysis for flue gas denitration. © 2016, Editorial Office of Journal of Xi'an Jiaotong University. All right reserved.