Modeling And Pilot Test Of The Urea Hydrolysis To Ammonia For Gas Denitration

Thermal power plant flue gas denitration SCR system commonly used method of liquid ammonia or urea reductant prepared, in recent years, domestic power generation companies for the use of ammonia in the process of increasing emphasis on the potential dangers to replace ammonia urea ammonia preparation process began to receive widespread attention. Urealysis prepared denitration reducing agent is divided into pyrolysis and hydrolysis, which hydrolysis to ammonia process equipment is 11% lower than the pyrolysis in the pre-investment, and is lower than annual operating costs. Hydrolysis to ammonia will have a stronger market competitiveness.Urea hydrolysis technology comes from waste recycling process of urea production in the chemical industry. When applied to the thermal power plant flue gas denitration SCR reductant preparation process, the reaction mechanism and process design have a significant difference. Nowadays, the theory study of urea hydrolysis to ammonia is based on the batch reactor, however, urea hydrolysis to ammonia of continuous reactor used in industry is a chemical reaction process with heat and mass transfer, its theoretical model needs to be further improved. For the research and development of urea hydrolysis technology applied to thermal power plant flue gas denitration. In this paper, theoretical model and experimental research were carried out for the industry continuous reactor.First of all, the nonlinear equations of mass balance, thermal equilibrium, chemical equilibrium and phase equilibrium were applied to establish thermal model and kinetic model for urea hydrolysis in an open system. On the equilibrium of gas-liquid two-phase, the modified Lewis-Randall equation and modified Herry equation were adopted, and the non-ideal behavior of ACWU gas-liquid two-phase system was modified by using PR equation of state and Extended-UNIQUAC model. The heat transfer of urea hydrolysis reaction system is consisted of heating by steam, heat conduction of coil and heat absorption of urea solution. The model of condensation heat transfer was used, and endothermic process of urea solution fitted the characteristics of boiling heat transfer.For simulation of industrial conditions, urea hydrolysis pilot plant was set up in TPRI, and experimental research was carried out.The impact of operating pressure and concentration of feeding solution on hydrolysis reaction system was analysed, and then the mode of the flow and heat transfer in urea hydrolysis reactor were discussed. According to two aspects of the reactor structure design and corrosion protection, the optimal urea hydrolysis process operating parameters were determined, which perating pressure is 0.6MPa, the operation temperature of 140～160℃, the feeding urea solution concentration is 40wt%-60wt%Finally, the impact the internal and external diffusion and mass transfer on the reaction kinetics was discussed, kinetic parameters of the urea hydrolysis reaction under the condition of thermal power plant denitration were fitted., the activation energy and frequency factor of urea hydrolysis reaction was found to be 86.575 kJ/mol and 2979461.82 s-1,respectively.