Three-dimensional Numerical Simulation Of Gas-solid Flow Characteristics And Water Vaporization In A Powder-Particle Spouted Bed

With people’s increasingly yearning for a better life,and then the demand for energy is growing,the demand for the environment is higher and higher.Coal accounts for 60%of China’s energy consumption structure.A large amount of sulfur dioxide will inevitably be generated after coal combustion,which will cause environmental pollution.Under the current environmental protection demand,how to effectively deal with these pollutants has become particularly important.For the treatment of sulfur-containing coal-fired flue gas,powder spouted bed has been widely studied because of its unique advantages.Compared with experiments,numerical simulation can deeply explore and analyze the distribution of parameters such as volume fraction,velocity,temperature,mass transfer rate and reaction rate of each component in the bed,so as to provide data support for optimizing reactor design and amplification process.The three-dimensional numerical simulation of powder spray semi dry flue gas desulfurization consists of three parts: gas-solid two-phase flow,water vaporization,mass transfer and heat transfer,and desulfurization reaction.In this paper,the two-dimensional water vaporization model is modified to three-dimensional by reasonable assumption and optimization.The gas-solid two-phase flow and water vaporization mass transfer and heat transfer process in the three-dimensional powder spouted bed are mainly studied and compared with the two-dimensional model.It is found that the gas-solid two-phase flow process of three-dimensional powder particle spouted bed is different from that of two-dimensional spouted bed under the same conditions.The spouting process in the three-dimensional spouted bed presents a cycle state,and the cycle time is 0.18 s at different apparent gas velocities.In addition,the circulation of particles is mainly driven by the gas at the inlet to move upward from the downward flowing particles on the conical wall,and the upward moving particles pass through the jet area to the fountain area,and this process is intermittent.In the three-dimensional spouted bed,the heat transfer between gas-liquid solid three-phase is transferred to feed water and particles by high-temperature gas in the spout area.The temperature difference between the three-phase in the fountain area and the annulus area is not significant,and the heat transfer is less.The water vaporization rate of the three-dimensional spouted bed is higher at the junction of the jet zone and the annulus,lower at the center of the jet zone and lowest at the annulus.The water vaporization rate of the two-dimensional spouted bed is higher than that of the three-dimensional spouted bed.For the three-dimensional powder spouted bed,it is found that the higher the gas velocity,the higher the liquid temperature and the lower the gas humidity,the more obvious the effect on the water vaporization.