流化床外型对内部流场影响的模拟研究

以双流体模型为基础,采用CFD商业软件Fluent对7种不同外型鼓泡流化床内的流动特性进行了数值模拟.模拟结果表明,流化床外型对反应器内部流场的影响显著,流化床内部流场随外型的不同而存在差异,在流态化初期产生气泡的时间、位置、密相床层高度方面以及流场稳定性的差异尤为明显.一旦充分流态化后,流场的差异性减弱.根据模拟得到的结果给出了相关建议.     

多孔挡板导流筒型流化床内构件研究

筒型内件可以改善气固流化床中气体和固体颗粒的接触，本文对此系统的流体力学特性进行了研究，从而得出数学模型，用此模型模拟鼓泡流化床得到良好结果。     

气液两相鼓泡塔流区及其过渡的混沌分析

应用确定性混沌分析技术,以气液两民塔内的压力波动时间序列为分析对象,系统研究了鼓泡塔系统的混沌特性。结果表明,鼓泡内气液两相流动系数为混沌动力学系统,混沌特征参数最大Ｌｙａｐｕｎｏｖ指数,Ｋｏｌｍｏｇｏｒｏｖ熵和关联维数Ｄ２等可以有效地表征鼓泡塔的流区及其过渡,混沌分析为定量判别鼓泡塔的流区及其过渡提供了新途径。操作条件对鼓泡塔内气液两相流动的混沌特性影响显示,表现为混沌特征参数值随表观气速增加而     

喷动流化床的最小喷动流化速度和床层压降

在一喷动流化床（直径５０ｍｍ）实验台上采用０．６３￣１．６０ｍｍ的神府原煤颗粒，在连续进料的情况下进行了最小喷动流化速度以及固定流化气、改变喷动气和固定喷动气、改变流化气的床层压降变化的实验研究。结果表明，最小喷动流化速度可以参考鼓泡流化床的临界流化速度的计算方法；床层压降变化证实，喷动流化床具有良好的调节能力。     

新型鼓泡管通道换热性能的数值分析

针对热回收领域由于积灰、阻力损失大等造成换热器换热性能差的缺点,提出了新型鼓泡换热管结构。建立周期性单元流道数值计算模型,对其换热性能进行研究,结果表明:顺排分布鼓泡时,鼓泡间距为16mm的鼓泡管换热性能最好,换热通道的阻力损失随鼓泡间距的增大而减小;鼓泡间距为16mm的换热通道,鼓泡叉排分布时的换能因子j较顺排分布时的换能因子提高30.61%,阻力特性因子f较顺排时降低了32.46%。     

化学镀法制备超细Ag-SnO2粉末的烧结

采用在1μm粒径的超细SnO2粉末化学镀银的方法,制备了超细Ag-SnO2复合粉末.通过压制成形、烧结等粉末冶金工艺,对粉末进行烧结试验,结果发现试样表面存在鼓泡现象.文章分析了鼓泡的成因,并采用降低成形压力及粉末煅烧处理等手段消除鼓泡现象.热重分析结果及烧结后的金相组织分析结果表明较低的成形压力可以改善鼓泡现象,但要从根本上消除鼓泡现象则必须对粉末进行高于450℃的煅烧处理.所得Ag-SnO2材料中SnO2颗粒分布均匀,电阻率、密度、硬度分别为2.25μΩcm、9.85 gcm-3和98 HB.     

冷轧带钢表面鼓泡缺陷分析

采用扫描电镜对冷轧带钢表面鼓泡处的横、纵断面,鼓泡的破裂面以及鼓泡处拉断表面的形貌进行了观察,并对微区成分作了分析.鼓泡主要是在钢坯皮下由保护渣形成了层状夹杂,导致冷轧原料板出现分层,从而在轧制过程中心部、表面的塑性变形不一致而形成.     

细铁粉气液固三相磁场流化床的床层膨胀特性

研究了空气－－水＝细铁粉三相磁场流化床在两种气体分布器作用下的床层膨胀特性。结果表明，随着增强强度的增强，细铁粉流化床层表现为散流区、链流区和磁聚区、气体在液体中的分散形态与气体分布器、气体速度和液体速度有关，表现为鼓泡、鼓泡－节涌和节涌。实验得到了链流区内气体在上述分散形态下的床层膨胀比（ｈ／ｈｏ）与气速（Ｕｇ）、液速（Ｕ１）和磁场强度（Ｈ）的经验关系式。关联式如下：ｈ／ｈ０＝９．４６Ｕ１＾０．     

气固流化床系统非线性机理研究进展

从近年来气固流化床两相流动的研究成果出发,总结了流化床非线性机理研究的方向.混沌理论研究表明流化床系统是确定型的混沌系统,而耗散结构理论的结果认为流化床系统属于非平衡热力学系统.对流化床系统的随机力分析将随机理论的方法运用到流化床流动机理和气泡分布研究中,有助于揭示流化床内部非线性机理和特性.     

阿尔马累克矿冶公司的扩建和改造

国立有色金属设计院为使其研制的硫化铜精矿处理新工艺(喷射鼓泡氧化熔炼)投入运行做了大量工作。炉子的工作室分3个区，每个区由冷却隔墙分开并完成独立的工作任务熔炼-鼓泡；分层鼓泡和贫化鼓泡。     

循环流态化焙烧在金精矿两段焙烧中的设计与应用

难处理复杂金精矿采用两段焙烧提金工艺流程中,一段炉采用流化床沸腾焙烧脱砷,二段炉采用循环流态化焙烧脱硫。生产实践表明,该组合形式生产出的焙砂的质量明显优于常规的第二段氧化焙烧采用沸腾流化床焙烧炉,同时焙砂的金氰化浸出率提高了2~3个百分点。     

气固流化床内锂颗粒停留时间影响因素研究

为提高锂精渣颗粒在气固流化床中的燃烧效率及延长颗粒的停留时间,基于CPFD理论详细研究了气流速度、质量流和压力等对颗粒在流化床中停留时间的影响,并分析锂精渣颗粒在流化床提升管内轴向高度颗粒浓度的分布情况。结果表明,在质量流一定的情况下可以通过增加气流速度来提高颗粒的停留时间;在相同气流速度下可以通过降低质量流来提高颗粒停留时间;进气压力对颗粒的停留时间影响很小;通过提高气流速度可以显著提高颗粒在密相区的停留时间。     

喷动流化床内砂状氢氧化铝结晶实验研究

在直径为100 mm的喷动流化床中,苛性比小于1.9,流化速度分别为1.42×10-3m/s,1.98×10-3m/s,2.55×10-3m/s的条件下进行了砂状氢氧化铝结晶实验,考察了苛性比和流化速度对晶粒生长和次生晶核形成的影响,建立了适宜的喷动流化结晶条件。     

The reduction of hematite to wustite in a laboratory fluidized bed

Particles (approximately 180 to 250 Μm across) were reduced by CO-CO₂, by H₂-H₂O, and by CO-CO₂-H₂-H₂O in a small fluidized bed, with facilities for automatic sampling of off-gas. Structural changes in the preheating period and during reduction were followed by surface area measurements and by microscopy. During reduction, surface areas increased initially and then decreased, as porosity created by chemical reaction was reduced by sintering; ‘uniform internal reduction’ was observed from magnetite to wustite. Although the bed was operated under vigorously bubbling conditions, with flow rates 7 to 15 times the minimum fluidization velocity at temperature, gas utilization was high for abstraction of about two-thirds of the maximum amount of oxygen removable by the inlet gas. The utilization fell sufficiently in the remaining stages of the reaction for approximate rate constants to be estimated. The rate increased (a) with increasing temperature, (b) with increasing gas flow, (c) with increasing reducing potential of the inlet gas, and (d) with increasing hydrogen content of inlet gas. The off-gas analyses showed the importance of the water gas shift reaction within the pores of the fluidized particles.     

Use of a tapered fluidized bed as a continuous bioreactor

Reactor systems based on tapered fluidized beds are being developed for aqueous bioprocesses in which adhering microorganisms or immobilized active biological fractions are used. The use of a fluidized bed prevents biomass buildup, accommodates particulates in the feed stream, is compatible with gas sparging, and allows easy removal or addition of the active materials. The tapered reactor tends to stabilize the fluidized bed, thus allowing a much wider range of operating conditions. Preliminary experimental results and an empirical mathematical model of the tapered bed indicate that bed stability is associated with a decreasing velocity and void-fraction profile up the bed and the pressure drop across the bed decreases with increasing flow rates. The tapered fluidized bed bioreactor is being evaluated for use in the enzymatic production of hydrogen, microbiological denitrification, and microbiological degradation of coal conversion aqueous waste streams. The enzyme catalyzed conversion of lactose to glucose and galactose was used in the evaluation of the reactor concept.     

The kinetics of nickel oxide reduction by hydrogen; Measurements in a fluidized bed and in a gravimetric apparatus

The suitability of a batch fluidized bed laboratory reactor for measuring the rates of gas-solid reactions was investigated. Experiments were carried out on the reduction of Falconbridge nickel oxide by hydrogen in a batch fluidized bed reactor within the tem-perature range 550 K to 650 K using particles in the range of 60 to 100 mesh. The reactor was operated at approximately atmospheric pressure and gas flow rates were in the range of two to four times the minimum fluidization velocity at temperature. The results showed internal consistency and rough agreement with the results of previous workers. The re-sults were interpreted and correlated by means of a structural model for gas-solid reac-tions. As a check on the fluidized bed measurements, experiments were also carried out using the conventional gravimetric technique to measure the rate of reduction of compac-ted pellets of nickel oxide by hydrogen. When due allowance was made for the change of surface area of the oxide during compaction, the results were in close agreement with the fluidized bed results. Rate measurements using hydrogen-nitrogen mixtures revealed that the reaction is not first order with respect to hydrogen, as usually assumed, but is ap-proximately of order two-thirds at one atmosphere hydrogen partial pressure. Formerly Graduate Student at Berkeley     

细粒级人造金红石流态化特性的CFD模拟

采用欧拉-欧拉模型,在20 mm宽和80 mm高的二维流化床中,模拟了直径为46μm和密度为4 000 kg/m3的细粒级人造金红石在不同操作气流速度下的流体动力学特性。在操作气流速度u=0.004 m/s时,呈现均匀的散式膨胀;当u=0.005 m/s时,出现鼓泡现象,为聚式流态化,但气泡内固体含量较高;提高气流速度至0.02 m/s,床层内出现固体含量几乎为零的气泡。     

Thermal decomposition of limestone in a fluidized bed

Particles of limestone of 16 to 28 and 60 to 100 mesh sizes were decomposed in a fluidized bed. A mathematical model for the thermal decomposition was proposed comprising the thermal decomposition at the interface within particles and the related heat and mass transfer steps. It was assumed in this model that the particles are completely mixed within the fluidized bed and that gas is in upward plug flow. Fractional decomposition of limestone particles and the bed temperature during thermal decomposition calculated from this model coincide very well with the experimental results. It was further revealed that the overall reaction rate of 60 to 100 mesh size particles is virtually determined by the rate of heat transfer from the reactor wall to the fluidized bed, and that both rates of interfacial reaction and heat transfer from the wall to the bed contribute to the overall decomposition rate of 16 to 28 mesh size particles. Former Graduate Student at Kyoto University, is now with the Railway Technical Research Center, JNR, Tokyo, Japan.     

高、低混合流速循环流化床锅炉的应用

介绍了一种高效高、低混合流速循环流化床锅炉的原理,技术特点及其工程应用.新型高效循环流化床锅炉吨汽有效容积随挥化份而变化,选取了合理的有效容积,且设计分离器阻力小于800 Pa.实践表明：新型锅炉热效率88％～91％,飞灰含碳量低至3％ ～5％,飞灰200目过筛率达88％.