Separation Characteristics Of Feedstock At Different Regions In The Gas-Solid Dense-Phase Separating Fluidized Bed

Gas-solid dense phase separation fluidized bed can achieve effective separation of 6-50 mm coal.However,the difference between the physical properties of the fluidizing medium and the medium solids determines the fluidization state of the medium solids and its heterogeneous flow pattern in the fluidized bed,thus affecting the density and stability of the bed layer.Steady flow state and bed density are the necessary conditions for materials separated accurately by density in a fluidized bed.Under the conditions of actual operation,it is difficult to achieve uniformity of medium solids flow state and bed density at different areas of the bed.The force acted on the selected materials and settlement motions of the particles in different areas of the bed are different.There are significant differences in the effect of separation at different regions.Thus it is very important to study the separation rule of feedstock at different regions in the separation fluidized bed.In this paper,compressed air is used as fluidizing medium,and magnetite powder mainly based on 0.074-0.3 mm is used as the medium solids.The physical property of the heavy medium is known by measuring of the characteristics of the bulk density,wall characteristics and mobility.The theoretical hypothesis and conjecture are regarded as breakthrough point.The relationship between the static bed height and the bed layer density stability is explored by carrying out single factor experiment.Under the condition of different fluidization number,the density data are collected and the density contours is drawn by using MATLAB software.Effect of the fluidization is evaluated by measuring the bed pressure gradient and calculating the standard deviation of bed density and observing the growth of bubbles.Forces acted on the different size and density tracer sphere particles in the fluidized bed are measured with the SF-3 dynamometer.The settling process of high density material is simulated by using large density steel balls.The process of the balls settlement are measured and recorded with the J0207 Electromagnetic Pointing Timer.Under the condition of different fluidization number,when the material is feed the different region,the rules of the force and settlment of the different size and density tracer particles are revealed.Under the condition of static feeding the material,the mechanical model of material particles in fluidized bed is improved.???The separating experiment is carried out at different region in the gas-solid dense phase separation fluidized bed.The bed layer is divided into nine regions?longitudinal A1,A2,A3 and horizontal B1,B2,B3?.The effects of the different paramters on separating result are explored by single factor experiment of static bed height H₀,sorting time T,fluidization number N.The effect of separation is explored by the experiment of feedstock at different regions.The results are as follows:under the condition that the static bed height H₀ is 140 mm,when the separation times T are2,min 3,min 4 min,the value of probable error E are 0.105 g/cm³,0.105 g/cm³,0.104g/cm³ respectively.When the fluidization numbers N are 1.35,1.5,1.65,the value of probable error E are 0.135 g/cm³,0.110 g/cm³,0.112 g/cm³ respectively.From the effect of different regions on the separation characteristics,the effects of separation between the A area above the bed and the A₁B₁ area are approximate consistent.When the regions of feeding material are A₁,A₂B₁,A₂B₃,the value of probable error E are0.090 g/cm³,0.135 g/cm³,0.130 g/cm³ respectively.Tow optimal programmes?T=3min,N=1.5,A₂B₁ and T=3 min,N=1.65,A₁B₁?are obtained by intuitively analysising the three-factor three-level orthogonal experimental results.Under the condition of tow optimal conditons,the experimental results are showed that the ash of clean coal are 10.66%and 11.02%respectively;the recovery of the combustible body of clean coal are 81.08%and 82.54%respectively;the value of probable error E is 0.095g/cm³ and 0.097 g/cm³ respectively.