Inhalable particle is a harmful air pollutant that causes a significant threat to people's health and ecological environments,which should be removed to purify air,but there exists limited removal efficiency due t...Inhalable particle is a harmful air pollutant that causes a significant threat to people's health and ecological environments,which should be removed to purify air,but there exists limited removal efficiency due to particle re-entrainment.Here,Operando observation system based on microscopic visualization method is developed to make in situ test of particle migration,deposition and re-entrainment characteristics on a lab-on-a-chip to achieve the investigation in micro-level scale.The deposition evolution of charged particles is recorded in electric field region intuitively,which confirms the fracture of particle chain occurs during the growth process of deposited particles.It captures the instantaneous process that a larger particle with micron size due to the coagulation of submicron particles fractures from main body of the particle chain for the first time.The analysis of migration behavior of a single submicron particle near electrode surface demonstrates the direct influence of drag force on the fracture of particle chain.This work is the first-time visualization of dynamic process and mechanism elucidation of particle re-entrainment at the micron level,and the findings will provide the theory support for the particle re-entrainment mechanism and bring inspires of enhancing capture efficiency of inhalable particle.展开更多
Electrostatic precipitators clean away the particulate matter of exhaust gases in manifold industrial processes.Parameter studies of particle separation in the size range of several 100 nm to 25μm is of particular in...Electrostatic precipitators clean away the particulate matter of exhaust gases in manifold industrial processes.Parameter studies of particle separation in the size range of several 100 nm to 25μm is of particular interest for the prediction of precipitation efficiencies and emissions.Models typically cover the transport of particles towards walls of the precipitator.However,no model yet covers the possible re-entrainment of particles from layers formed at the walls back into the gas flow.This study presents the implementation of a new time-resolving model for electrostatic precipitation utilizing a re-entrainment model.Experimental data support the results of modelling.The model uses a statistical approach based on properties of the particulate layer forming at the precipitator walls.The model is used for the analysis of the redispersion of particles in a laboratory-scale electrostatic precipitator(Sander,Gawor,&Fritsching,2018).Results show reduced precipitation efficiencies for particles larger than 5μm as particles have higher kinetic impact energies and lower bounding energy at the layer surface.Time dynamics reveal a steady-state behavior of the separation for CaCO3(limestone,trademark"Ulmer WeissR")while Al2O3(trademark"Pural NFR")precipitation is affected by layer buildup at the walls increasing over several minutes.展开更多
Wall deposition occurs in spray dryers when dried or partially dried particles contact and adhere to the walls during operation, thus reducing the yield of product collected. Wall deposits also present a product conta...Wall deposition occurs in spray dryers when dried or partially dried particles contact and adhere to the walls during operation, thus reducing the yield of product collected. Wall deposits also present a product contamination risk and a fire or explosion risk when spray drying products that oxidize exothermically, such as milk powder. Re-entrainment is the resuspension of spray dryer wall deposits into the main gas stream for collection as product. Literature suggests that the process for re-entrainment of particles from spray dryer wall deposits is strongly dependent on particle size and gas velocity.展开更多
基金supported by the National Natural Science Foundation of China (Nos.52200130 and 22176123)Postdoctoral Science Foundation of China (No.2022M722082)the National Key Research&Development Plan (No.2017YFC0211804)。
文摘Inhalable particle is a harmful air pollutant that causes a significant threat to people's health and ecological environments,which should be removed to purify air,but there exists limited removal efficiency due to particle re-entrainment.Here,Operando observation system based on microscopic visualization method is developed to make in situ test of particle migration,deposition and re-entrainment characteristics on a lab-on-a-chip to achieve the investigation in micro-level scale.The deposition evolution of charged particles is recorded in electric field region intuitively,which confirms the fracture of particle chain occurs during the growth process of deposited particles.It captures the instantaneous process that a larger particle with micron size due to the coagulation of submicron particles fractures from main body of the particle chain for the first time.The analysis of migration behavior of a single submicron particle near electrode surface demonstrates the direct influence of drag force on the fracture of particle chain.This work is the first-time visualization of dynamic process and mechanism elucidation of particle re-entrainment at the micron level,and the findings will provide the theory support for the particle re-entrainment mechanism and bring inspires of enhancing capture efficiency of inhalable particle.
文摘Electrostatic precipitators clean away the particulate matter of exhaust gases in manifold industrial processes.Parameter studies of particle separation in the size range of several 100 nm to 25μm is of particular interest for the prediction of precipitation efficiencies and emissions.Models typically cover the transport of particles towards walls of the precipitator.However,no model yet covers the possible re-entrainment of particles from layers formed at the walls back into the gas flow.This study presents the implementation of a new time-resolving model for electrostatic precipitation utilizing a re-entrainment model.Experimental data support the results of modelling.The model uses a statistical approach based on properties of the particulate layer forming at the precipitator walls.The model is used for the analysis of the redispersion of particles in a laboratory-scale electrostatic precipitator(Sander,Gawor,&Fritsching,2018).Results show reduced precipitation efficiencies for particles larger than 5μm as particles have higher kinetic impact energies and lower bounding energy at the layer surface.Time dynamics reveal a steady-state behavior of the separation for CaCO3(limestone,trademark"Ulmer WeissR")while Al2O3(trademark"Pural NFR")precipitation is affected by layer buildup at the walls increasing over several minutes.
文摘Wall deposition occurs in spray dryers when dried or partially dried particles contact and adhere to the walls during operation, thus reducing the yield of product collected. Wall deposits also present a product contamination risk and a fire or explosion risk when spray drying products that oxidize exothermically, such as milk powder. Re-entrainment is the resuspension of spray dryer wall deposits into the main gas stream for collection as product. Literature suggests that the process for re-entrainment of particles from spray dryer wall deposits is strongly dependent on particle size and gas velocity.
