| Fine particulate matter is easy to cause haze weather,and seriously harm human health.Under the environmental protection constraints such as"carbon peak,carbon neutral"and other goals,particulate matter emission standards are becoming more and more stringent,and traditional dust removal technology is difficult to meet the emission requirements of fine particles.Agglomerating technique is an effective means to strengthen the interphase interaction of particles and to remove the particles after they grow together.In this paper,a coupling method of turbulence agglomeration and humidification agglomeration is proposed to promote the efficient removal of fine particles in the swirl field,and the removal effect is verified.The removal mechanism is revealed through theoretical analysis,numerical simulation and experimental study.The main research work and innovation points are as follows:A strong cyclone spray dust removal experimental system was designed and built.The effects of cyclone separation and spray humidification on the removal of fine particles in cyclone field were investigated,and the influence rules of inlet air velocity,spray flow rate,initial particle concentration and other conditions on the removal efficiency of fine particles were experimentally studied.The results show that when without spraying the removal efficiency of large particle size increases with the increase of cyclone velocity,but the removal efficiency of small particle size decreases with the increase of cyclone velocity,and the total removal efficiency of particles is low.Spray humidification in swirling flow field improves the removal efficiency of fine particles,and the removal efficiency of fine particles of different particle sizes is significantly improved.Under typical working conditions,spray humidification can increase the removal efficiency of fine particles in the swirl field by more than 40%.At the same flow rate,the larger the spray volume,the better the spray humidification removal effect.Under the same condition,the removal efficiency increases first and then decreases with the increase of particle concentration.The Reynolds stress model suitable for anisotropy was used to simulate the flow field in the swirl precipitator.The tangential,axial,radial velocity and turbulent structure characteristics and pressure distribution of the gas phase swirl flow field were analyzed.The results show that the inner flow of the swirling flow field is a complex turbulent flow,and the velocity is basically axisymmetric along the radial direction.The outer region of tangential velocity is a quasi-free vortex,while the inner region is a quasi-forced vortex.The maximum tangential velocity is located near the device wall and the central velocity is small.There is a significant pressure gradient in the radial direction of the static pressure,and it increases from the center to the side wall,showing an obvious rotation characteristic.Near the wall,there is a large velocity gradient,the fluctuation of Reynolds stress is large,and the turbulent kinetic energy of the fluid is relatively large.The Reynolds stress distribution in the central region is flat and the turbulent kinetic energy of the fluid is weak.The large difference of Reynolds stress distribution reflects the anisotropy characteristics of strong swirling flow.The Euler two-fluid model based on the population balance model was used to study the velocity and concentration distribution of fine particles in the strong swirl field,and the interaction mechanism between the swirl flow characteristics and particle agglomeration removal under different flue gas parameters was investigated.The results show that the fine particles in the strong swirling flow field are easy to follow the airflow,and their velocities are characterized by rotating flow.In central region,particle volume fraction and turbulent kinetic energy is small,reunite particle collision probability is small,granular component source term almost to zero,the smaller particle size.In the area near the wall,due to the high particle concentration,the number of particles per unit volume increases,which increases the collision probability and makes it easier to adhere and obvious particle agglomeration occurs,the particle size is larger.With the increase of inlet velocity,particle collision is promoted,and the particle size of fine particles increases slightly along the axial direction.However,particles with smaller particle size are easily discharged by airflow entrain due to the influence of turbulence pulsation and radial mixing,and the separation efficiency decreases gradually.Under the condition that the turbulence characteristics remain unchanged,with the increase of the particle concentration,the particle concentration in the near wall and the central area increases,and the distance between particles decreases.The removal efficiency is improved due to the turbulent agglomeration.The gas-liquid two-phase flow characteristics under different gas flow rates and spray flow rates were studied by using the Euler two-fluid model and the population balance model.The droplet movement and separation characteristics during spray process were obtained.The results show that the rotating water mist increases the coverage area of the water mist,and the interaction with the gas phase swirl makes the velocity of the flue gas under the nozzle decrease sharply,which enhances the enrolling ability of the surrounding medium,and improves the mass transfer effect compared with that without spray.The droplet volume concentration was hollow cone,low in the center region and high in the side wall region.In the swirl field,the particle size of the droplet near the wall increases continuously,and the fraction of the large droplet group increases,while the fraction of the small droplet group is smaller.In the spray center area,the group fraction of both the large droplet and the small droplet decreases,resulting in a distribution pattern that the average particle size of the droplet in the center area is smaller than that near the wall area.With the increase of air velocity,the droplet convergence and growth phenomenon are very significant,droplet breakage is not obvious and the centrifugal separation efficiency is improved.The droplet concentration at the outlet decreases and the pressure drop gradually increases.With the increase of spray volume,the pressure drop showed an increasing trend,but the amplitude was not large,and the concentration of fog drops at the outlet increased.Taking the strong cyclone spray dust collector as the research object,the Euler multiphase flow model was established,which regarded the gas phase,solid phase and liquid phase as the continuous phase.On this basis,the population balance model of the collision and coalescence of droplets and dust particles was loaded.The multiphase flow characteristics of the strong cyclone spray dust removal and the agglomeration removal effect of the spray in the strong cyclone field under different influence parameters were numerically calculated.The results show that with the introduction of spray solution,the liquid bridging force and viscous force promoting agglomeration increase the turbulent kinetic energy of gas phase in the spray area,and the reflux area around the nozzle enrolls particles and droplets,extending the acting time of droplets and particles,and promoting the agglomeration and growth of particles.With the increase of flue gas velocity,the turbulent kinetic energy in the near wall area increases,and the increase of swirling centrifugal force improves the relative velocity of dust particles and fog droplets,which promotes the enhancement of gas-liquid turbulence,accelerates the increase of fine particle size,and improves the agglomeration and removal efficiency of particulate matter.With the increase of spray flow,the number of droplets increases,which increases the collision efficiency between particles and droplets,and the increase of turbulent kinetic energy in the spray area is conducive to the turbulent mixing between particles and between particles and droplets,which significantly improves the agglomeration removal efficiency of particles.As the concentration of particulate matter increases,due to the limited adsorption efficiency of spray droplets,the number of outlet particles decreases first and then increases,and the removal efficiency of particulate matter increases first and then decreases,reaching the maximum value at 2g/m~3. |
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