Simulation And Analysis Of Urea To Ammonia In Thermal Power Plant

The reducing agent NH3 of SCR commonly used method of liquid ammonia to prepare.However,due to the safety of liquid ammonia,urea ammonia has been widely used in recent years.Urealysis prepared denitration reducing agent include urea pyrolysis and hydrolysis.Based on the existing technology and parameters of system,this simulation conducted for the two processes using Aspen Plus to compare the ammonia production and energy consumption under different operating conditions.On these basis,this study analyzed the optimal ammonia production scheme and operating conditions.Moreover,the urea hydrolysis system of the 300MW unit was designed.Using RCSTR module in Aspen Plus to simulate the urea pyrolysis and hydrolysis systems of a 300MW unit of a coal-fired power plant.Compared with pyrolysis,the hydrolysis scheme has a lower reaction temperature,and the energy consumption is only about 20-30%of that of pyrolysis.What's more,low temperature steam can be used as the heat source of the hydrolysis scheme.From the point of energy saving,hydrolysis to ammonia is the best method.This study analysed the influence of urea feed mass fraction,reaction temperature and pressure on the product gas of urea hydrolysis method.The result showed a same tendency with the experimental data,verifying the reliability of the hydrolysis model.When the urea feed mass fraction was increased,the ammonia concentration in the product gas increased,while the heat consumption decreased.However,with the increase of feed concentration,the urea in the liquid also increased,thus the risk of corrosion rising.With the temperature increasing,the urea hydrolysis rate increased,but also accelerated the ionization reactions,and the economy was poor.As the pressure rose,the risk of corrosion decreased.However,excessive operating pressure will inhibit the release of product gas.Considering comprehensively,the operating temperature and pressure of the hydrolyzer can opt to 150-160? and 0.6-0.8 MPa,respectively.Finally,the urea hydrolysis system of the 300MW unit was designed under the condition of urea solution at 50%wt,160? and 0.6MPa.The results showed that the hydrolyzer needs to take saturated steam(180?,1 MPa)417.72 kg/h,and the reactor volume should be 14.52m3.