Study On The Agglomeration And Removal Of Fine Particles In Multiple Fields

Since the 21st century,with the rapid economic development,the energy consumption is increasing day by day.Moreover,China is a big consumer of coal,and the particulate matter emitted by coal-fired power plants is one of the main sources of air pollution,which increases the frequency of haze,and the heavy metal and other harmful substances it carries will seriously endanger human health.The removal efficiency of fine particulate matter(PM_2.5)by traditional precipitators is low.With the continuous improvement of China's emission standards,traditional precipitators can no longer meet the standard requirements.The method of particle pretreatment is considered to aggregate fine particles into large ones for further removal.The research on the methods of acoustic agglomeration,chemical agglomeration and electrical agglomeration has become a hot spot.In this paper,the agglomeration characterization and removal efficiency of particulate matter with the traditional electrostatic precipitator in the single field and multi-field are studied.At present,the research on multi-field synergy is not complete and the theoretical model is seldom studied.Firstly,particle removal experiments in positive and negative DC field,agglomeration experiments and combined removal experiments in pulsed corona discharge field and acoustic field have been carried on,it is found that the negative DC high voltage discharge effect is higher than that of positive DC,the input voltage and pulse frequency in pulsed electric field,the sound pressure level?SPL?and acoustic wave frequency in acoustic field will affect the number concentration distribution of the particles.The particle agglomeration characterization experiment is carried out with DP-02 laser particle size analyzer,and the on-line agglomeration detection of particles is realized.The concept of agglomeration rate is put forward,and the agglomeration rate is analyzed to characterize the agglomeration effect under different experimental conditions.It is found that the median size of fine particles in the external field is significantly improved,and there is an optimal sound frequency of 1600 Hz in the acoustic field to maximize the particle agglomeration efficiency.At the same time,the effect of the combined action of acoustic wave and pulsed corona discharge on the agglomeration rate of fine particles is compared,which is better than single field.Secondly,three different size of monodisperse particles are used for particle agglomeration experimental research.It is found that the particle number concentration of monodisperse particles matters more than the particle size.the influence of monodisperse particles in the acoustic field is mainly due to the acoutic wake effect rather than the synthetic agglomeration,with the increase of SPL,agglomeration efficiency of particles will increase,and the optimal acoustic frequency for each particle exists.With the increase of particle size of monodisperse particles,the agglomeration efficiency of under the same conditions will be improved,but the advantage of combined field over single field is decreasing.Then a platform for the removal of fine particles under synergistic action of several fields is designed,and the effects of humidity and oxygen content on discharge characteristics and particle charge are studied.and the optimal conditions of multi-field synergistic action are analyzed by studying the operating parameters of different fields.With the increase of SPL,the introduction of acoustic field has a buff effect on particle charge.The combination of three kinds of joint field and DC can greatly promote the removal efficiency,the effect is more than that of two kinds of combination applied field and DC.when the acoustic wave frequency is 1400 Hz,SPL is 143 dB,pulse input voltage is 55 kV,pulse frequency is 100 Hz,and the addition of 0.1%XTG,the value of removal efficiency reaches the maximum,its value is 94.0%.Multi-field synergy removal can be used as an effective means to improve the dust collection effect of particles which are difficult to be removed from traditional precipitators.Finally,The forces on fine particles in multi-field effect are studied from the aspects of mechanism theory,including acoustic driving force,acoustic wake effect,coulomb force and the electric field force,through the analysis of agglomeration of monodisperse particles and polydisperse particles in different coupling field,different agglomeration kernal models are established.Three kinds of agglomeration kernal in different coupling fields are calculated respectively,the influences of SPL,acoustic wave frequency,electric field intensity and particle size on agglomeration kernel are discussed,and the results of the kernel function are compared and analyzed.The influences of various operating conditions on the number concentration of particles under the combined action of acoustic wave and pulsed electric field are calculated by the grouping method,which is consistent with the experimental results.