Kinetics Determination Of Noncatalytic Liquid-Solid Reaction System In Stirred Tank And CFD Simulation Of Particle Suspension

As a common reaction device,the stirred tank reactor has the characteristics of strong adaptability,flexible operation and large controllable range of reaction conditions.Since the reaction kinetics and the homogeneity of the reaction system in the stirred tank will both affect the chemical reaction rate,this paper conducts the reaction kinetics and particle suspension in the stirred tank from the experimental and numerical simulation aspects.The experimental results show that the reaction rate is positively correlated with the reaction temperature,gas phase reactant pressure and solid particle surface area under the condition of eliminating mass transfer resistance.After determining the reaction rate control step as the surface reaction control,the reaction rate constants at 60?,70?,80?,and 90?were obtained through the assumed kinetic equations,and the experimental data were brought into the kinetics equation for testing,and it was found that the experimental value and the calculated value have a high consistency,which shows the rationality of the kinetic equation,and the activation energy of the reaction is 22.325 kJ·mol-1.The gas-liquid mass transfer resistance is expressed by the relationship between the stirring speed and the Sherwood number,and a differential equation system about the concentration of the gas-phase reactants and the particle size is established.Thus,the changes of the pressure of the gas-phase reactants and the particle size with time under the condition of mass transfer resistance are obtained.The numerical simulation results show that the k-? turbulence model can form a larger axial circulation in the stirred tank with baffles and pitched blade impeller,thus improving the suspension effect of particles.The rotation speed has no obvious effect on the flow pattern in the stirred tank,but within a certain range,the uniformity of the mixing of solid particles is positively related to the stirring speed.The small clearance of the stirring tank may cause the flow pattern to be difficult to expand,thus resulting in poor suspension of the particles,and the power consumption of the stirred tank will increase sharply.The critical suspension speed of the stirred tank is positively related to the diameter of the solid particles and the initial volume fraction of the particles.The mixing efficiency in the stirred tank is proportional to the flow rate,and the transfer rate of particles at the tip of the blade is faster,and the transfer rate at the center of the blade is the slowest.