散装水泥运输罐车流化床改进方案的研究及仿真

以某型号散装水泥运输罐车为研究对象,提出几种改善流化质量的研究方案;在流体力学计算软件FLUENT中建立流化床流态化模型,对改进后的流化过程进行仿真,并且对流化质量进行评价分析。结果表明:采用40°侧导流板,用弧形布风板代替平面布风板的改进优化后,能够有效改善散装水泥运输车罐内水泥的流化质量,在原有的散装物料运输车的基础上对其结构进行改进,能够改善其工作性能,提高工作效率。     

Experimental Study in a Short Circulating Fluidized Bed Riser

Experiments were performed with gas and solids flow in a 2.42 m high circulating fluidized bed (CFB). This equipment has both solids and gas fed into the downer section. Local solids holdup was measured using an optical fiber probe. By the axial solids concentration distribution, it was verified that (1) the curve that precedes the entrance into the riser provides further acceleration to the flow and (2) the abrupt exit causes an increase in solids concentration in the top zone. Results of radial distributions in the bottom zone show that the flow is more concentrated near the wall. For the exit zone, the distributions show high values of solids holdup both near the wall and on the axis.     

空气重介质流化床的床层黏度研究

利用旋转法对空气重介质流化床的床层黏度进行研究,分析影响流化床床层黏度的因素,建立床层黏度与影响因素的数学模型。结果表明:流化床床层黏度随着加重质磁铁矿粉平均粒度的增大而增大,随着流化气速的增大而减小,随着床层高度及重介质水分含量的增大而增大;当煤粉质量分数大于12%时,床层黏度明显增大,煤粉质量分数为17%时,气-固两相流的流动性变差。     

循环流化床锅炉内颗粒速度分布的实验研究

为了研究操作参数对循环流化床锅炉内颗粒速度分布的影响,在冷态模型装置上使用PV6A型颗粒速度光纤测量仪、毕托管对循环流化床锅炉炉膛内的颗粒速度进行了测量与分析。结果表明:在流化风速为2.57 m/s、循环质量流率为0.58 kg/(m2.s)、一次风量为2 300 m3/h、二次风量为1 500 m3/h时,循环流化床锅炉炉膛内颗粒浓度分布、压降、流化状态、质量循环都达到一个较稳定的水平,呈现典型的环核分布特征。     

流化床气流磨粉碎制备超细SiC片晶的实验研究

超细SiC片晶由于其高强度、高弹性模量和导热系数已成为替代价值昂贵、制备技术复杂SiC晶须的理想的增韧材料。本文中通过对流化床气流磨粉碎机理,以及粉碎腔内工质压强与喷嘴个数对SiC颗粒形貌影响的研究,得出工质压强、喷嘴个数等参数对粉碎的颗粒形貌有很大的影响的结论,其中粉碎腔采用高的工质压强以增加粉碎强度。采用两喷嘴以增加颗粒互相撞击的几率是制备片状SiC粉的有效方法;采用流化床式气流磨加多级涡轮分级机的粉碎系统可以制备产品质量较好的多级别超细SiC片晶微粉。     

快速床提升管内颗粒的扩散行为研究

在直径１００ｍ ｍ ×３ｍ 的实验台上,利用热粒子为示踪剂,研究快速床提升管内的颗粒的扩散行为。在不同的径向位置测得反映扩散行为的温度响应曲线,提出二维扩散模型来描述颗粒的轴、径向扩散。通过最小二乘拟和估计轴向扩散系统Ｄａ 和径向扩散系数Ｄｒ。实验发现,Ｄａ 随气体表面风速的增加而增加,Ｄｒ 则基本保持不变。静止床高的增加使Ｄａ、Ｄｒ 略有增加。     

循环流化床锅炉二次送风结构影响的数值模拟

利用CFD软件Fluent,基于颗粒动力学理论的双流体模型对循环流化床锅炉的3种二次风送风结构对炉膛内气-固两相流宏观流动特性的影响进行数值模拟,将3种结构下的计算结果进行对比分析。结果表明:二次风通常采用90°垂直入射的情况下,炉膛内颗粒的环-核分布结构及上稀下浓的分布不均匀性达到最大;二次风进口入射角为与轴向方向成60°向上入射情况下,炉膛内颗粒主要分布在炉膛中上部区域,不均匀程度减小,最有利于炉膛内的燃烧和提高传热效率,同时得到二次风的射流深度最大;二次风送入结构为渐缩型入射口的情况时,二次风射流深度最小,炉膛内偏流现象明显,在本文的操作条件下,并没有达到喷射的设计效果,还有待于进一步的研究。     

大型循环流化床底部区域颗粒浓度分布研究

为获得内径400mm、高9100mm的大型循环流化床底部区域颗粒浓度分布规律,利用光导纤维探头研究了该区域颗粒浓度的径向分布。实验结果表明,颗粒浓度径向分布不均匀,呈现出典型的环-核结构。r/R=0.8可以作为环-核分界点。增大颗粒循环速率,颗粒浓度增大,边壁区域增大幅度比中心区域大。增大表观气速,颗粒浓度减小,边壁区域减小幅度比中心区域大。径向不同位置颗粒浓度随轴向高度增加均减小,边壁区域减小幅度比中心区域大。     

Coating of Puffed Wheat by a Tumbling Method a Fluidized Bed Technique

Puffed wheat, traditionally consumed as a ready-to-eat breakfast cereal, is normally covered with sweet coatings. To make it more appealing to different tastes and consumers, the coating may also have colored ingredients added. Due to the rugged surface of puffed wheat, colored coats do not totally cover the particulate, causing problems of appearance that may affect overall quality. There is a need to develop uniform coats in order to improve physical properties, such as color and texture. Puffed wheat was coated with sweetened chocolate syrups by tumbling and a fluidized bed. Different proportions of sugar, cocoa, and starch were used to develop the cover and obtain an optimum formulation. The coated wheat was characterized by instrumental techniques. The developed product using the fluidized bed technique presented a firmer consistency and a more uniform color than the tumbling-coated and the commercial wheat.     

Coating of Puffed Wheat by a Tumbling Method a Fluidized Bed Technique

Puffed wheat, traditionally consumed as a ready-to-eat breakfast cereal, is normally covered with sweet coatings. To make it more appealing to different tastes and consumers, the coating may also have colored ingredients added. Due to the rugged surface of puffed wheat, colored coats do not totally cover the particulate, causing problems of appearance that may affect overall quality. There is a need to develop uniform coats in order to improve physical properties, such as color and texture. Puffed wheat was coated with sweetened chocolate syrups by tumbling and a fluidized bed. Different proportions of sugar, cocoa, and starch were used to develop the cover and obtain an optimum formulation. The coated wheat was characterized by instrumental techniques. The developed product using the fluidized bed technique presented a firmer consistency and a more uniform color than the tumbling-coated and the commercial wheat.     

稀相气-固流化床分选电厂磨机返料中黄铁矿的实验与模拟

为了降低燃煤电厂的磨机功耗,减少锅炉燃烧后的污染排放,通过分析磨煤机分离器返料的粒度和密度分布,对电厂采样物料进行稀相流化床分选去除黄铁矿等矿物质的实验研究,并对物料分选过程进行数值模拟。结果表明,粒径小于0.500 mm的分离器返料在流化床中具有较小的起始流化速度1.62 cm/s,流化床各层的密度和粒度具有很好的稳定性;物料中的黄铁矿等矿物质得到分离,上层和底层物料灰分质量分数分别为33.34%、73.42%,硫分质量分数分别为1.12%、8.96%,底层物中硫主要以黄铁矿的形式存在;气-固两相流稀相分选床的流场形态及颗粒运动数值模拟验证了实验结论。     

Time Domain Analysis of Optical Fiber Probe Signals Measured in a Short Circulating Fluidized Bed Riser

A time domain analysis of electrical signals provided by an optical fiber probe was conducted in order to characterize the local flow dynamics of a short circulating fluidized bed riser with a height of 2.42 m and ID of 82 mm. Experiments were carried out with air, and the bed materials were FCC particles (Geldart A). Probability and standard deviation distribution of signals measured locally at five radial positions and four axial positions are presented. The probability distribution can indicate the uniformity of the flow in terms of solids holdup distribution and can reveal the formation of clusters. Probability distributions indicate that the flux is more uniform in the core region of the reactor and that clusters appear near the wall. The highest value obtained in the standard deviation of the radial distribution suggests greater interaction between particles at that radial position. It was found that for the two lower axial positions, this phenomenon occurs near the wall, and for the two higher positions, the interactions between particles occur both near the wall and in the center due to the exit configuration of the reactor.     

液-固流化床回收废旧印刷电路板金属研究

采用液-固流化床对废旧印刷电路板资源化利用进行研究,通过分析颗粒在流化床中的运动机理,计算不同颗粒在流化床中的沉降末速度,并探讨影响颗粒沉降末速度的因素。结果表明,颗粒干扰沉降末速度随着颗粒密度和粒度的增大而增大,随着颗粒体积分数的增大而减小;对不同粒级不同给料量进行分选,随着上升水速的增大,金属回收率随之下降,品位随之提高;在实验范围内,给料量对液-固流化床中金属与非金属的分选效果基本无影响。     

循环流化床锅炉用旋风分离器性能的实验研究

结合水煤浆流化-悬浮燃烧的特点,通过全面测定循环流化床锅炉用旋风分离器在不同操作参数下的分离效率,研究了入口气速、入口颗粒浓度、入口颗粒物性等对旋风分离器的压降和分离性能的影响规律。实验结果表明,影响旋风分离器分离性能的主要物性参数是颗粒的中位粒径、密度,在入口颗粒的中位粒径相差较大时分离性能主要受粒径的影响,而当入口颗粒粒径相差较小时密度对分离器分离性能的影响则更为显著。     

循环流化床底部区域流动特性的数值模拟

基于欧拉两相流模型计算循环流化床底部区域的流动特性。在低气速(1.0～2.5m/s)、低循环量下(5.2～34.5kg/(m2·s)),模拟时黏性采用层流模型取得了较好的效果。实验采用光导纤维探头测量仪测量流化床底部区域3个截面的局部颗粒浓度,模拟计算了循环流化床底部3个截面的颗粒浓度的径向分布,并同循环流化床装置的实验数据进行了对比。结果表明,数值模拟计算与实验结果相吻合。     

The Unique Phase Doppler Particle Analyzer Application and Analysis of Solid Particle Flow in the Fluidized Bed Combustor (FBC) Cold Model

The hydrodynamic effects of varying operating parameters in the fluidized bed combustor (FBC) have been of great interest to the FBC design and manufacturing process. Some experiments to investigate the gas/particle flows in the gaseous fluidized bed were performed with the laser-based phase Doppler particle analyzer (PDPA). In the experiments, the PDPA was used to measure the vertical component of fluidizing particle velocity at one specific position point. The robust experimental design method was used to evaluate the experimental conditions and to analyze the experimental results. An empirical model for the particle velocity vertical component V_y with particle size (S) and fluidizing airflow rate (R) as variables was developed for the FBC cold model. From the model, it was found that vertical component V_y has a strong linear relationship with the fluidizing airflow rate (R), while particle size (S) has less linear relationship to V_y. It can also be seen that V_y increased when fluidizing airflow rate increased and V_y decreased when particle size increased.     

The Unique Phase Doppler Particle Analyzer Application and Analysis of Solid Particle Flow in the Fluidized Bed Combustor (FBC) Cold Model

The hydrodynamic effects of varying operating parameters in the fluidized bed combustor (FBC) have been of great interest to the FBC design and manufacturing process. Some experiments to investigate the gas/particle flows in the gaseous fluidized bed were performed with the laser-based phase Doppler particle analyzer (PDPA). In the experiments, the PDPA was used to measure the vertical component of fluidizing particle velocity at one specific position point. The robust experimental design method was used to evaluate the experimental conditions and to analyze the experimental results. An empirical model for the particle velocity vertical component V_y with particle size (S) and fluidizing airflow rate (R) as variables was developed for the FBC cold model. From the model, it was found that vertical component V_y has a strong linear relationship with the fluidizing airflow rate (R), while particle size (S) has less linear relationship to V_y. It can also be seen that V_y increased when fluidizing airflow rate increased and V_y decreased when particle size increased.     

粒径分布对循环床内颗粒速度分布的影响

利用激光相位多普勒粒子分析仪（PDPA），在截面尺寸为100mm×15mm的二维循环流化床实验装置上测量比较了平均粒径基本相同的3种不同粒径分布的玻璃珠颗粒在相同操作气速下的颗粒时均速度、脉动速度与数量密度的截面分布特性；初步考察了粒径分布对气固并流上行两相湍流流动行为的影响问题。     

超临界循环流化床机组全负荷段深度调峰方法研究

随着新能源发电装机容量不断扩大,火力发电市场受到严重挤压,为了满足电网深度调峰的需求,火电厂需要承担起深度调峰的重任,循环流化床机组可以采用停炉不停机的方式参与深度调峰。以山西某电厂超临界350 MW循环流化床机组为研究对象,分析了超临界循环流化床机组2种典型汽水系统全负荷段深度调峰方法,对其中的操作要点进行了详细的阐述,并就操作过程中需要特别关注的问题进行了分析,也提出了相应的防控措施。分析表明:超临界循环流化床机组可以采用2种典型汽水系统实现全负荷段深度调峰;加装炉水循环泵系统投资大、操作复杂,增设贮水箱到除氧器管路投资小、操作简单,但是加装炉水循环泵系统参与全负荷段调峰时,各系统稳定性较好。     

鼓泡床内双组分颗粒流动行为的数值模拟

为了模拟预测粒径和密度同时存在差异的双组分颗粒体系的分级混合行为,基于欧拉-欧拉方法建立多流体模型,采用颗粒动力学理论描述颗粒相性质,分别通过Gidaspow和Syamlal曳力模型描述气-固相曳力和固-固相作用力。结果表明,模拟得到的轴向和径向颗粒浓度分布与实验数据吻合较好;当在较小气流速度下出现分级行为时,床层底部富沉积组分层中沉积组分的运动十分有限,而在较大气流速度下处于完全混合状态时,床层内部颗粒运动较为剧烈。