Hydrolysis Of Urea To Produce Ammonia Dircio Francisco Xavier Fatima Ximenes

Nitrogen oxides(NOx)has caused huge environmental problems,it is one of the biggest environmental pollutants and as regulations on nitrogen oxides(NOx)are gradually tightened,many researches have been actively conducted worldwide to reduce NOx-causing pollution.A number of techniques have been developed and utilized up to now and the selective catalytic reduction(SCR)and the selective non catalytic reduction(SNCR)have been proved to have high denitration efficiency.In SCR and SNCR processes,reducing agents are injected into the flue gas to reduce NOx into harmless nitrogen(N2).At present,the most popular reducing agent is ammonia(NH3).Ammonia produced from the catalytic urea hydrolysis plays an important role in ammonia-based NOx removal process.The aim of this thesis is threefold.First of all is the selection of homogenous and heterogeneous catalyst was done and prepared to catalyze the hydrolysis of urea under different reaction conditions and the qualitative analysis of urea hydrolysis especially titration of urea hydrolysis by HCl and NaOH was adopted to determine the conversion of the urea hydrolysis.Second is that Box-Behnken center composite experiments were carried out with four factors;reaction temperature,reaction time,reaction pressure,and the dosage of sodium acetate catalyst.The response surface methodology(RSM)was adopted to determine the prime factors and interaction on the conversion rate of urea hydrolysis.And third is to construct the thermodynamic model and kinetic model of urea hydrolysis in an open system by using or applying the non-linear equations of mass balance,thermal balance,chemical balance,and phase balance.On the equilibrium of vapor-liquid two phases,the Lewis Randall equation and the modified Herry equation were adopted,the non-ideal linear behavior of the ACWU system(NH3-CO2-H2O-(NH2)2CO)vapor-liquid two-phase system was modified by using PR equation of state and extended-UNIQUAC model.The result showed that the optimized process conditions were that the reaction temperature was 160?,the reaction time was 4h,the reaction pressure was 4MPa and the dosage of sodium acetate was 0.034wt%.Under the optimized reaction conditions,the conversion rate of urea hydrolysis was 98.620%.The fitting quadratic regression model based on the BBD experiment was valid and the model predicted the experiment ran well.