Numerical Simulation Of The Physical Field Of SCR System In 30 Million Square Meters Gypsum Board Production Line

Selective Catalytic Reduction（SCR）technology has been proved to be an effective denitrification technology at present.However,in the process of application,it is necessary to determine the structure parameters of SCR process and its reactor according to the specific characteristics of flue gas temperature and composition in order to ensure denitrification efficiency.The hot flue gas produced by calcining raw gypsum in fluidized bed furnace in gypsum board production process needs denitrification treatment.Because the flue gas temperature is higher than the working temperature of catalyst,cold air is mixed into the actual project to reduce the temperature of catalyst.How to design the mixing mode of cold air to ensure the uniformity of the physical field in the reactor is the key to the application of tail gas denitrification technology in gypsum board plant.In order to solve this problem,the enterprise entrusted the evaluation of the SCR denitrification system design scheme of the gypsum board production line with an annual output of 30 million m².And optimized the physical field of the system by adjusting the process parameters,so as to guide the SCR process design and operation of the gypsum board production line.It has important practical value for guiding the SCR process design and operation optimization of the gypsum board production line.Using computational fluid dynamics software such as ANSYS Fluent,based on engineering drawings and calibration data provided by the factory,the SCR denitrification system was modeled and simulated numerically.The uniformity of the physical field was characterized by relative standard deviation of velocity,relative standard deviation of NH₃ concentration and upper and lower deviation of temperature,respectively,and the distribution law of the parameters in the system was explored.In view of the shortcomings of the initial scheme,three optimization schemes are proposed to improve the flow field uniformity from the aspects of pipe shape,ammonia injection mode and diversion equipment.By optimizing the position and angle of the cold air inflow,the shape or quantity of the guide plate and the treatment of the bend,an ideal SCR system scheme is obtained.The results show that the three optimization schemes can improve the uniformity of the physical field in varying degrees,and the flue gas temperature satisfying the working temperature of the catalyst can be controlled.The mixing of flue gas is aggravated by helical cold air injection.The efficiency of fluid heat transfer is improved by inserting nozzle air injection.Rational addition of diversion plate is a simpler and more effective optimization method.The non-uniformity of velocity field is effectively improved by adding rectifier grid.When the distance between the cold air inlet and the ammonia injection system is 2 m,the angle of cold air inflow is 55degrees,four fan-shaped guide plates are arranged,the turning radius of the round pipe is 1.0 m,and six guide plates are arranged above the reaction tower,the uniformity of the flow field is the best.