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Effect Of Baffle Structure On Residence Time Of Large Particles In Horizontal Multi-chamber Fluidized Bed

Posted on:2020-04-27Degree:MasterType:Thesis
Country:ChinaCandidate:C C ChenFull Text:PDF
GTID:2381330599976205Subject:Chemical engineering
Abstract/Summary:PDF Full Text Request
The horizontal multi-chamber fluidized bed is a rectangular bed.To improve the residence time distribution of the material,the bed is divided into several chambers by some baffles.The horizontal multi-chamber fluidized bed is suitable for continuous drying of loose granular materials and has been widely used.Horizontal multi-chamber fluidized bed dryer adopts tongue-shaped punching distribution board.Usually a distance is left between the baffles and the distribution board to push a small amount of agglomerates in the fluidized bed to the outlet to discharge the fluidized bed.However,the fluidized bed of the distribution board-baffle's structure is used to dry materials with large difference in particle size.The material with larger particle size has large particle size,short residence time,high wet content,and uneven drying of the product,which often fails to meet the drying requirements.Therefore,this article keeps the original odd-numbered baffles unchanged,combines the even-numbered baffles with the distribution board and changes the height of even-numbered baffles.The colorless glass beads with the particle size range of 0.355 mm-0.6 mm is used as the material,and the colored glass beads with the particle size range of 0.85 mm-1.0 mm,1.4 mm-1.7 mm and 1.7 mm-2.36 mm are used as the tracer.In the 600 mm×100 mm horizontal six-chamber fluidized bed,the effect of baffle's structure on residence time distribution of large particulate materials is studied.The experiment uses air as the fluidization medium and uses pulse tracing method to obtain the relationship between the cumulative residence time distribution F?t?of large particulate materials and time.The effect of discharge mode,feed rate,the height of baffle 2 and 4,tracer particulate size on residence time distribution E?t?,average residence time???,dimensionless variance??2 and parameter N of multi-reactor series model are studied.And using the multi-tank series model to fit the experimental data.The results show that the height of overflow weir is 80 mm,and the average residence time of tracer increases from 5.08 min to 6.26 min when the height of baffle2 and 4 increase from 30 mm to 80 mm in the the condition of overflow.When the height of baffle 2 and 4 is 60 mm,the average residence time of tracer is longer than the material space time,and the average residence time of tracer with average particulate size of 2 mm is 0.18 min longer than the tracer with average particle size of 1 mm.Under the condition of direct discharge,the average residence time of tracer increases from 2.63 min to 5.06 min when the height of baffle 2 and 4 increases from30 mm to 80 mm.When the height of baffle 2 and 4 is 50 mm,the average residence time of tracer is longer than the material space time,and the average residence time of tracer with average particle size of 2 mm is 0.1 min longer than the tracer with average particle size of 1 mm.The baffles'structure can improve the average residence time of large particulate materials.Increasing the height of baffle 2 and baffle 4 can increase the average residence time of large particles.The larger the particle size,the longer the average residence time,and the longer the drying time of materials.On the basis of the multi-tank series model,the model is established for two experimental conditions of changing the height of baffle 2 and 4,changing the discharge method.The model formulas are as follows:E???=13.5??+a0?2e-3??+a0?The experimental data is used to verify the accuracy of the model.The peak width,peak height and tailing of the residence time density distribution function of the model formula and the experimental data is well matched..The result of this study can provide theoretical reference for the improvement of horizontal multi-chamber fluidized bed structure.
Keywords/Search Tags:fluidized bed, residence time distribution, multi-tank series model
PDF Full Text Request
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