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CFD simulation of bubbling and collapsing characteristics in a gas-solid fluidized bed 总被引:4,自引:0,他引:4
Computational Fluid Dynamics (CFD) has become an alternative method to experiments for understanding the fluid dynamics of multiphase flow. A two-fluid model, which contains additional terms in both the gas- and solid-phase momentum equations, is used to investigate the fluidization quality in a fluidized bed. A case study for quartz sand with a density of 2,660 kg/m^3 and a diameter of 500 μm, whose physical property is similar to a new kind of catalyst for producing clean fuels through the residue fluid catalytic cracking process, is simulated in a two-dimensional fluidized bed with 0.57 m width and 1.00 m height. Transient bubbling and collapsing characteristics are numerically investigated in the platform of CFX 4.4 by integrating user-defined Fortran subroutines. The results show that the fluidization and collapse process is in fair agreement with the classical theory of Geldart B classification, but the collapse time is affected by bubbles at the interface between the dense phase and freeboard. 相似文献
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A simple hydrodynamic model based on two-fluid theory,taking into account the effect of discrete particles on both the gas-and solid-phase momentum equations,was used to numerically investigate the pressure fluctuation characteristics in a gas-solid fluidized bed with the aid of CFX 4.4,a commercial CFD software package,by adding user-defined Fortran subroutines.Numerical simulations together with typical experimental measurements show that pressure fluctuations originate above the distributor when a gas pulse is injected into the fluidized bed.The pressure above the bubble gradually increases due to the presence of a rising bubble.When the bubble passes through the bed surface,the pressure near the bed surface gradually decreases to a lower value.Moreover,the pressure signals in the bubbling fluidized beds show obviously periodic characteristics.The major frequency of pressure fluctuations at the same vertical position is affected slightly by the operating gas velocity,and the amplitude of pressure fluctuations is related to both the operating gas velocity and the vertical height.In this study,the influence of the operating gas velocity on the pressure wave propagation velocity can be ignored,and only two peak frequencies in the power spectrum of the pressure fluctuations are observed which are associated with the bubble formation above the distributor and its eruption at the bed surface. 相似文献
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流化床工艺冷凝操作热量计算的探讨 总被引:1,自引:0,他引:1
塑料厂LLDPE装置采用美国Univation公司20世纪80年代流化床工艺.该装置于2002年进行冷凝态操作模式改造,可以在不提高换热面积的情况下提高生产速率150%以上,文中针对非冷凝态与冷凝态操作热量平衡的原理以及特点进行了探讨. 相似文献
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流化床反应器的静电与结片的消除方法 总被引:1,自引:0,他引:1
文中论述了UNIPOL流化床反应器在生产过程中产生静电的机理及危害.分析了静电及结片产生的因素,并对此提出了行之有效的预防及消除方法. 相似文献
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甲醇制烯烃(MTO)项目普遍存在急冷水中含有有机物及催化剂粉末的情况,导致水洗塔操作不稳定,换热器换热效率下降,需经常离线清洗,运维劳动强度大、费用高,严重影响装置的长期、安全稳定运行.通过分析比较目前常用的几类分离方法,提出沸腾床过滤法在急冷水的深度净化上具有较大竞争优势,重点对沸腾床的分离过程进行了详细介绍.结合实... 相似文献
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半干法烟气脱硫工艺以其经济性好、能耗小、适应性强、产物易处理等优点而被广泛应用。针对某石油化工厂循环流化床锅炉烟气脱硫后的硫含量未达到GB 13223-2011《火电厂大气污染物排放标准》的问题,在侧线试验装置上进行了半干法烟气脱硫性能试验研究。选取3种不同硫含量的烟气,试验研究烟气入口温度、烟气入口流速、喷水量及脱硫剂浓度等运行参数对半干法烟气脱硫效率的影响。在经济许可的运行参数范围内,烟气脱硫效率高达91%,达到大气污染物排放标准中含硫量的要求。 相似文献
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在组合流化床燃烧器的冷态实验装置上,以空气一石英砂颗粒为流化介质体系,在烧焦管内表观气速(u。)为3.156~5.989m/s,颗粒循环强度(G8)为40.8~229.4kg/(m2·s)的条件下,采用光纤颗粒浓度测量仪对烧焦管内床层径向局部位置的固含率(ε8)进行了测定。结果表明,烧焦管内ε8沿床层径向呈中心稀边壁浓的环一核形分布形态,呈现出非均一的相结构;ε8随ug的升高而减小,且随Gs的升高而增大,这种影响规律在烧焦管的边壁区比中心区更为显著。根据实验数据关联出截面平均固含率不变条件下的径向局部ε8的计算式,所得计算值与实验值基本吻合。 相似文献
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XGL-2×3型三通道固定流化床催化裂化实验装置的构造与运行 总被引:2,自引:1,他引:1
介绍了XGL-2×3型三通道固定流化床催化裂化实验装置的组成、工艺流程及运行情况。在调试和试运行过程中曾出现裂化气产率的平行性较差、水泵出口压力偏高、再生烟气红外分析仪出现偏差等问题,采取适当措施后装置可稳定运行。催化剂评价及工艺条件考察效率比单套固定流化床装置高2倍。试用结果表明:干气、液化气、汽油、柴油、重油、焦炭收率最大相对误差分别为1.47%,0.78%,0.37%,0.25%,1.55%,1.25%;产物总收率最大相对误差为0.16%。 相似文献
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张光别 《中国炼油与石油化工》2020,22(2):102-110
In the present paper, the experimental method and computational fluid dynamics (CFD) method were used to investigate the effect of gas distributors with different orifice size and orifice pitch on fluidization characteristics in gas-solid fluidized bed.
The distributor pressure drop, bubble evolution, bed pressure drop and the distribution profile of solid volume fraction were investigated with using the four types of gas distributor plates.
Euler- Euler two fluid model(TFM) approach based on the kinetic theory of granular flow (KTGF) and Standard k-epsilon turbulence model were employed in the numerical simulation with using ANSYS Fluent 15.0.
The results showed that the orifice size and orifice pitch of gas distributor plate have the significant influence on the flow characteristics in gas-solid fluidized bed. With decreasing orifice size and orifice pitch of gas distributor plates under the same opening area, the distributor pressure drop, the initial bubble size and height of dead zone just above distributor was decreased, and the bed pressure drop was more increased than that of the larger orifice size and orifice pitch of distributors, the distribution of solid volume fraction was also more homogeneous for the small orifice size. 相似文献