共查询到19条相似文献,搜索用时 46 毫秒
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采用欧拉-欧拉双流体模型,在Fluent数值模拟平台上对循环湍动流化床进行了研究。采用Gidaspow模型分段描述密相湍动和稀相循环输送区气固的相互作用,考察了反应器内压力、颗粒浓度等气固湍动特性参数的变化。计算流体力学(CFD)的模拟结果表明:反应器中压力分布较为均匀;固体颗粒相和气体相间隙成絮状分布,在轴向中心区域颗粒浓度分布较为均匀;边壁区域颗粒浓度变化较大,存在强烈的气固相互作用。 相似文献
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在较宽的操作条件范围内系统测试了下行床床层压力降,获得气固两相流与管内壁间的摩擦压降,提出了下行气固两相流与管壁间摩擦压降的计算模型。结果表明,在下行床的充分发展段,气固两相流与管壁间的摩擦导致表观颗粒浓度显著小于真实颗粒浓度;当表观气速大于8 m·s-1时,气固两相流与管壁间的摩擦压降接近甚至超过气固两相流重力产生的静压降。在采用压差法测试下行床中的平均颗粒浓度时,如忽略气固两相流与管壁间的摩擦,则可能导致显著的偏差。下行气固两相流与管内壁间的摩擦压降主要来自于颗粒与管壁间的摩擦。颗粒直径对气固两相流与管壁间摩擦压降的影响随着操作气速的提高逐渐减弱。采用提出的摩擦压降模型对表观颗粒浓度进行修正后,预测值与实验值吻合较好。 相似文献
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以甲烷化循环流化床反应器为研究对象,采用计算颗粒流体力学(CPFD)方法,耦合了甲烷化反应动力学模型,实现了甲烷化在循环流化床中的反应过程。将模拟结果同文献中的实验数据进行了对比验证,获得了反应器的内部流场、温度场以及组分浓度分布。数值模拟研究了不同操作条件对甲烷化特性的影响规律。结果表明:催化剂颗粒在反应器内的流化行为对反应影响显著,反应器提升管固体密相区是反应进行的主要区域;通过提高反应压力和H2/CO(物质的量之比),降低空速,可以提高CO转化率和CH4收率。 相似文献
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下行床气固两相流动计算流体力学模拟 总被引:5,自引:3,他引:5
基于颗粒相动力学理论 ,对层流机制表达的气固两相流体力学模型采用Reynolds平均的方法获得气固两相流的湍流模型描述 .其中 ,气相湍流行为以k -ε模型描述 ;颗粒相的碰撞行为以颗粒流的动力学模型表达 ;而湍流行为以kp 模型描述 .因此建立的k -ε -Θ -kp 模型综合考虑了气相和颗粒相的湍流运动以及颗粒的碰撞行为 .依据此模型建立了三维流体力学求解程序并对下行床气固两相流动行为进行了模型预测 .讨论了恢复系数的选取及壁效应假设 ,从机理上分析并考察了 3种模型的预测能力 .针对内径 1 40mm、高 7m的下行床冷态设备 ,在较宽的操作范围内 ,对比了详细的颗粒浓度和速度径向分布以及轴向参数分布 ,并对下行床的放大行为进行了预测 . 相似文献
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循环流化床燃烧数学模型及试验研究 总被引:5,自引:3,他引:2
利用循环流化床内气-固两相流动基础方面的研究成果, 提出床内气固浓-淡流动模型, 建立适用不同结构参数的循环流化床燃烧模型, 考虑了床内气体、固体颗粒的返混、循环过程以及煤燃烧、污染气体的生成和分解、颗粒磨损等过程. 在循环流化床燃烧试验台上进行实验研究, 模型仿真结果和实验数据吻合良好, 表明气固两相浓-淡流动模型所建立的循环流动床燃烧系统模型可以正确地模拟循环流化床的燃烧过程. 相似文献
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引 言流化床换热器具有防、除垢和强化传热等优点 ,在化工、食品、海水淡化、废水处理等领域具有广阔的应用前景[1].目前 ,流化床换热器历经散式流化床、内循环流化床 ,已发展到外循环流化床换热器[2 ],它要求在较稀的颗粒浓度 (颗粒浓度小于 5% )、较高的流速 ( 1~ 3m·s- 1)下操作 .流化床换热器中液体流动及颗粒运动状态的研究对流化床换热器的设计和操作具有重要意义 ,但人们对循环流化床换热器中颗粒运动情况的研究还很缺乏 .考虑到循环流化床换热器中的每根换热管都可作为一个独立的循环流化床对待[3].本文试图建立一滑移速度模型… 相似文献
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EFFECTS OF SECONDARY AIR INJECTION ON GAS-SOLID FLOW BEHAVIOR IN CIRCULATING FLUIDIZED BEDS 总被引:3,自引:0,他引:3
Yong Kang Pyung S. Song Jong S. Yun Yi Y. Jeong Sang D. Kim 《Chemical Engineering Communications》2000,177(1):31-47
Effects of secondary air injection on the hydrodynamics such as solid holdup and gas-solid flow behavior were investigated in a circulating fluidized bed. The gas velocity in the riser, the ratio of secondary air velocity to that of primary air, and the solid circulating rate were chosen as operating variables. Fluid cracking catalyst(FCC) with a density of 1840 kg/m3 and a mean diameter of 74 um was employed as the solid phase. The secondary air was fed to the riser radially or tangentially at the wall of the column. Pressure drop fluctuations in the riser were measured and analyzed by adopting the stochastic method to characterize the effects of secondary air injection on the gas-solid flow behavior in the bed.
It has been found that the injection of secondary air into the riser can increase the solid holdup in the riser considerably, and that the tangential injection of secondary air is more effective for the increasing the solid holdup than the radial injection. However, the gas-solid flow behavior has been found to become less persistent with the injection of secondary air; the resultant flow behavior is more complex when the air is injected tangentially than radially. The solid holdups in the primary as well as secondary zones of the riser have been well correlated in terms of not only operating variables but also fractal dimension of the pressure fluctuations. 相似文献
It has been found that the injection of secondary air into the riser can increase the solid holdup in the riser considerably, and that the tangential injection of secondary air is more effective for the increasing the solid holdup than the radial injection. However, the gas-solid flow behavior has been found to become less persistent with the injection of secondary air; the resultant flow behavior is more complex when the air is injected tangentially than radially. The solid holdups in the primary as well as secondary zones of the riser have been well correlated in terms of not only operating variables but also fractal dimension of the pressure fluctuations. 相似文献
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YONG KANG PYUNG S. SONG JONG S. YUN YI Y. JEONG SANG D. KIM 《Chemical Engineering Communications》2013,200(1):31-47
Effects of secondary air injection on the hydrodynamics such as solid holdup and gas-solid flow behavior were investigated in a circulating fluidized bed. The gas velocity in the riser, the ratio of secondary air velocity to that of primary air, and the solid circulating rate were chosen as operating variables. Fluid cracking catalyst(FCC) with a density of 1840 kg/m3 and a mean diameter of 74 um was employed as the solid phase. The secondary air was fed to the riser radially or tangentially at the wall of the column. Pressure drop fluctuations in the riser were measured and analyzed by adopting the stochastic method to characterize the effects of secondary air injection on the gas-solid flow behavior in the bed. It has been found that the injection of secondary air into the riser can increase the solid holdup in the riser considerably, and that the tangential injection of secondary air is more effective for the increasing the solid holdup than the radial injection. However, the gas-solid flow behavior has been found to become less persistent with the injection of secondary air; the resultant flow behavior is more complex when the air is injected tangentially than radially. The solid holdups in the primary as well as secondary zones of the riser have been well correlated in terms of not only operating variables but also fractal dimension of the pressure fluctuations. 相似文献