Simulation Research On Particle Heat Transfer Process In A Solid Heat Carrier Rotary Retorting For Oil Shale

The solid heat carrier rotary retorting technology is one of the main methods for refining granular oil shale.In this method,high-temperature shale ash particles are used as a heat carrier for mixing with oil shale particles in the horizontal rotary drum reactor and heating it,through which the pyrolysis process of oil shale particles is realized.The process of mixing and heat transfer between these two kinds of particles is very complicated during the pyrolysis.And the mixing effect has a direct influence on the effect of heat transfer,which will impact the oil yield of oil shale retorting finally.Therefore,it is of great significance to study the mixing and heat transfer process between oil shale particles and shale ash particles in the rotary retorting.In this paper,we choose the particle system which is formed by oil shale particles and hot shale ash particles in a non-reacting rotary retorting as the subject investigated,design the experimental condition through single factor experiment method and orthogonal experiment method respectively.And the process of mixing and heat transfer are investigated by applying discrete element method(DEM)combined with particle thermal conduction model.The mixing index,the average temperature of particles and the standard deviation of temperature are used as the quantitative indexes to evaluate the effect of fill ratio of particles,rotational speed of vessel,diameter of the oil shale particles and flights form on particles mixing and heat transfer characteristics.When rotary retorting without flights equipped,the segregation phenomenon between different kinds of particles is the main cause for the poor mixing and heat transfer effect.With the increasing of the fill ratio or the diameter of oil shale particles,the segregation phenomenon is difficult to eliminate,and the worse the mixing and heat transfer performance.But it goes up firstly then down with the increasing of rotational speed.When the flights installed in rotary retorting,the disturbance of flights can effectively improve the mixing speed of particle system and raise oil shale particles' average temperature.However,the effect of different forms of flights affecting on the mixing and heat transfer process is relatively small.Through the range analysis and variance analysis of the orthogonal test results,the influence of various factors on the mixing and heat transfer process was obtained.Under the experimental conditions designed in this paper,the factors having highly significant influence on the mixing are fill ratio and diameter of oil shale particles,and the oil shale particles' diameter also plays an obviously important role in the heat transfer.But the effect of rotational speed is minimal both on the mixing and heat transfer process.By using comprehensive balance method and experimentalverification,the optimal operating parameters combination was obtained: the particle filling ratio is 20%,the rotational speed is 0.2rad/s,the diameter of oil shale particles is 3mm,and right-angled flights installed in the drum,which lays a good foundation for further optimization and research.