Study On Particle Deposition Characteristics In Gasifier Based On Particle Comprehensive Adhesion Model

Particle deposition in gasifier is the premise of realizing slag layer accumulation and flow,wall reaction and other processes,Exploring slag deposition mechanism and perfecting the calculation model of deposition rate are of great significance to the safe and stable operation of gasifier.In this paper,the particle deposition process is divided into two processes:particle adhesion and near wall transport.For the adhesion process,a comprehensive adhesion model is established and verified;For the near wall transport process,the influence of particle force on deposition under different working conditions is analyzed.The main contents are as follows:1.Starting with the analysis of the morphological characteristics of particles under different temperatures and conversion degrees,taking the ash melting degree and carbon conversion as the two factors to describe the surface characteristics of particles,through the analysis of the particle char-slag interaction mode,the adhesion probability based on the surface characteristics is proposed,and the kinetic energy parameters are taken as the critical condition of particle adhesion to form the particle adhesion model.In addition,considering the influence of slag layer on adhesion,a comprehensive adhesion model is summarized.The model analysis shows that when the particle is higher than the critical velocity and lower than the critical kinetic energy required to overcome the effects of surface tension and viscosity,the particle adhesion ability is determined by the surface characteristics.The particle surface characteristics are determined by coal type,particle temperature and carbon conversion rate.The ash carbon ratio,particle temperature and carbon conversion rate are positively correlated with the adhesion ability,while higher than the ash flow temperature,the adhesion ability is affected by the change of surface structure.2.The effectiveness of the model is verified by two groups of experimental data under gasification and combustion conditions,and the relationship between temperature and deposition rate is further explored through the dropper furnace deposition experiment.It is found that the deposition rate increases with the increase of temperature.The variation trend of deposition rate predicted by the model at higher temperature is similar to the experimental results,and the particle deposition rate is underestimated at lower temperature because the predicted ash melting fraction does not consider the non-uniform distribution of elements.3.Through the two-dimensional channel particle deposition simulation,the effects of particle force and flow field velocity on the deposition velocity under the environmental conditions of gasifier are analyzed.It is found that except that Saffman lift and thermophoresis promote the deposition,Brownian force significantly improves the deposition velocity of small particle size particles(dp<5μm).With the increase of gas velocity,the deposition velocity increases first and then decreases.The limiting factor of large particles is the adhesion criterion,while small particles are affected by the deposition mechanism.In addition the analysis of the driving force induced by particle reaction shows that the force is closely related to the reaction rate,and the force has little effect on deposition under the reaction conditions of gasifier.