Numerical Simulation And Experimental Study On Spray Drying Of Nitroguanidine

Nitroguanidine is a kind of flammable and explosive energetic material,and the traditional drying method is box drying.In this paper,the spray drying technique is used to dry nitroguanidine slurry to achieve highly efficiency,continuous and rapid drying.First of all,numerical simulation and experimental research were carried out on the spray drying process of nitroguanidine.Based on the known design parameters,material balance calculation and selection design calculation were carried out on the drying tower,and the geometric dimensions of the experimental grade centrifugal spray drying prototype were determined.A numerical model for spray drying of nitroguanidine slurry was established by using Fluent,a numerical simulation software,providing theoretical basis for subsequent engineering amplification experiments.Realizable k-?turbulence model was used to fit the air flow field in the tower,and particle trajectory model was used to describe the droplet motion.Considering the coupling effect between gas and liquid,the energy model was opened,and the component transport model was added on the basis of Navier-Stokes equation,and the boundary conditions were set according to the actual working conditions.Simulation results show that after the hot air into the drying tower at a certain tangential velocity,spiraling downward rapid erosion,material droplets after contact with the hot air moisture to evaporate quickly,droplet diameter by into tower 67.8?m reduced to 37.0?m,the water content at the outlet decreased from 75.000%to 0.027%,drying effect is obvious,in theory can meet the spray drying tower design index.Secondly,by amplifying the process of the experimental prototype,an industrial-scale continuous spray drying tower was constructed,and the atomization mode was changed to air flow type.Based on the above numerical model,the TAB crushing model was introduced.The gas flow rate and feed rate were amplified by 46 times,the boundary conditions were changed,and the air flow spray drying tower was simulated and calculated.Finally,through the experimental research of nitroguanidine gas-flow spray drying process,the best optimum process parameters are as follows:concentration 25%,inlet air temperature 180?,outlet air temperature 80?,feed rate 345 L/h.The experimental data of moisture content,particle size distribution and field temperature distribution of air-flow spray drying products were been compared with the simulation results.The results show that the average particle size d₅₀=12.6?m,and the water content is 0.030%.The temperature distribution in the tower is similar to the prediction results,which further verifies the correctness of the mathematical model.The morphology of nitroguanidine before and after drying is compared in the end,and the two are basically consistent,which can fully explain the reliability of spray drying.