Research On Fluidizing And Separating Characteristics Of Gas-solids Agitatated Fluidized Bed With Binary Medium Solids

Water resources and coal resources of China are in reverse regularities of distribution as a whole show,water scarcity is the biggest problem restricting the implementation of traditional coal separating technology in water shortage areas.Dry coal separating is a new and highly efficient separation technology in the field of coal separating.The main characteristic of dry coal separating is that the gas-solids suspension are used as separation medium.Stable airflow is accessed into fluidized bed with fine medium particles,and the medium solids,which formate fluidizing gas-solid suspension with a certain density and fluid properties,get fluidized.Selected materials in the fluidized bed are separating according to the density stratification,the light floating,and the heavy sinking,separation of different particles is achieved because of different density.Agitated system were successfully applicated into gas-solids agitated fluidized bed with binary medium solids to prevent the local instability of the bed caused by the merger of bubbles.The agitated system can effectively improve the fluidization effect of fluidized bed to form a stable and uniform fluidized station.Quartz sands and magnetite powders are mixed to form binary medium solids,quartz sands are used to improve the performance of dense medium and broaden the fluidized bed separation density.In the experiment agitated fluidized bed was used as operating system,airflow and quartz sand-magnetite powder forming binary dense medium was used as separating medium with fluid properties.The characteristics of fluidization and separation of gas-solids agitated fluidized bed with binary medium solids are studied.Through the study on the fluidization of binary medium solids formed by several different grading sizes quartz sand and magnetite powder.When the operating factors are H=160 mm,U=1.1Umf and V=75 r/min,optimal quartz sand sizes are 0.45-0.3mm and 0.3-0.15 mm.When the weight ratio of magnetite powder are 10% and 12%,fluidized bed exhibits optimal density stability,the standard deviation of density are 0.0425 and 0.0454.Density contours,graphic model of pressure drop distribution and fluidized curves are drawed by Matlab and Origin,they can objective show the fluidization characteristics of fluidized bed,which provides theoretical basis for separating operation.The single factor exploration was carried out on the fluidizing gas velocity,bed height and agitated speed of gas-solids agitated fluidized bed with binary medium solids.The results show that when fluidized bed is in stable statin,the operating factors are H=160 mm,U=1.1Umf and V=75 r/min.The ox-Behnken response surface method is used by Design-Expert software,it is based on the evaluation index ash degree of segregation and standard deviation of density.When the bed height was fixed in 160 mm,gas veolicity is 9.89cm/s,agitatating speed is 75r/min,the bed is near to optimal fluidization,when standard deviation of density is 0.0362.The 13-6 mm coal and 6-5mm fine coal are separated in the bed under this experimental condition,the ash content of clean coal are 6.94% and 9.50%,ash degree of segregation can reach 1.25 and 1.19 respectively,obviously are superior to the fine coal below 4mm.The value of probable error E show 0.121 g/cm3 and 0.135 g/cm3,which indicates successful spearating.Fine coal below 4 mm can not be effectively separated under this experimental condition.