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首页> 外文学位 >ENGINEERING STUDY ON THE DRYING OF WOOD PARTICLES IN A FLUIDIZED BED (HEAT TRANSFER, MINIMUM FLUIDIZATION VELOCITY, EFFICIENCY).
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ENGINEERING STUDY ON THE DRYING OF WOOD PARTICLES IN A FLUIDIZED BED (HEAT TRANSFER, MINIMUM FLUIDIZATION VELOCITY, EFFICIENCY).

机译：流化床中木材颗粒干燥的工程研究（传热，最小流化速度，效率）。

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Fluidized bed dryers are commonly employed for the industrial drying of granular materials. In the forest products industry there exists a potential to dry particulate wood in fluidized beds. This study investigated the engineering parameters necessary to design an industrial fluidized bed dryer and compared various fluidized bed drying arrangements to commercial rotary dryers in terms of energy efficiency.; A 0.2 m square bed was constructed to fluidize processed wood particles and sawdust. The minimum fluidization velocities (u(,mf)), voidages, and elutriation constants were determined for a bed at room temperature. Emulsion-to-surface heat transfer coefficients were determined with a copper tube in both a cold and hot bed. Batch and batch simulated continuous (BSC) drying trials were done with inlet temperatures ranging from 127 to 290(DEGREES)C. BSC drying was done to collect data for designing a continuous dryer.; For the unscreened material (dust to 7 mm), u(,mf) was 0.66 m/s for the sawdust and 1.03 m/s for the processed particles. These values increased with increasing moisture content, decreasing sphericity, and increasing particle diameter. An operating range of 1.3 to 2.0 times u(,mf) was found to give acceptable fluidization without excessive entrainment. Some channeling and agglomeration occurred at average bed moisture contents greater than 80 percent (dry weight basis). Surface-to-emulsion heat transfer coefficients of 80 to 130 W/m('2)K were low for a fluidized system when compared to other materials.; Drying curves were presented for batch and BSC drying and a method was presented for adjusting these curves to account for the bed temperature, gas flow rate, and bed weight. Using this method, an isothermal inlet drying curve can be used to either obtain an isothermal bed drying curve or adjust drying curves to predict the performance of an industrial design.; Single and two stage fluidized bed drying arrangements were compared to two commercial rotary dryers. The fluidized bed designs are competitive in terms of energy efficiency. The information presented in this study indicates that wood particles can be fluidized to make this type of dryer practical.
机译：流化床干燥器通常用于颗粒材料的工业干燥。在林产品工业中，有可能在流化床中干燥颗粒木材。这项研究调查了设计工业流化床干燥机所需的工程参数，并就能源效率将各种流化床干燥装置与商用旋转干燥机进行了比较。构造了一个0.2 m的方形床，以流化处理过的木材颗粒和锯末。在室温下确定床的最小流化速度（u（，mf）），空隙率和淘析常数。在冷床和热床中均使用铜管测定了乳液至表面的传热系数。批次和批次模拟连续（BSC）干燥试验均在127至290（DEGREES）C的进口温度范围内进行。完成BSC干燥以收集用于设计连续干燥器的数据。对于未经筛选的材料（灰尘至7 mm），锯末的u（，mf）为0.66 m / s，加工后的颗粒的u（，mf）为1.03 m / s。这些值随水分含量增加，球形度降低和粒径增加而增加。发现在1.3到2.0倍u（，mf）的工作范围内可以得到可接受的流态化而没有过多的夹带。当床层平均含水量大于80％（以干重计）时，会发生一些窜流和结块。当与其他材料相比时，流化系统的表面-乳液传热系数为80至130 W / m（'2）K。给出了批次和BSC干燥的干燥曲线，并提出了一种调整这些曲线以说明床温，气体流速和床重的方法。使用这种方法，可以使用等温入口干燥曲线来获得等温床干燥曲线或调整干燥曲线以预测工业设计的性能。将单级和两级流化床干燥装置与两台商用旋转干燥机进行了比较。就节能而言，流化床设计具有竞争力。这项研究中提供的信息表明，木材颗粒可以流化以使这种类型的干燥机实用。

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