声发射技术在气固两相流检测中的研究进展

阐述声发射技术的检测原理，回顾了近年来声发射技术在气固两相流检测中的研究成果，包括气固流化床、循环流化床、气力输送管道等，涉及到流化状态识别、流型转变、颗粒质量流量、颗粒粒径等方面的检测，研究表明：声发射信号对颗粒的运动非常敏感，能够实时准确检测气固两相流动特征。最后展望了基于声发射的气固两相流检测技术的发展方向。     

关于Unipol气相法聚乙烯工艺的几点思考

针对Unipol工艺而言,气相流化床反应技术与催化剂技术是其最核心的技术。在经过了长期的发展与创新之后,Unipol工艺通常都是将催化剂技术的发展与工艺的发展紧密联系,并以此来确保技术能够实现工业化应用。针对Unipol气相法聚乙烯工艺进行简单分析,以供参考。     

高流动抗冲聚丙烯的研究与开发

采用Unipol低压气相流化床工艺技术,新型催化剂结合氢调法开发生产了高流动抗冲聚丙烯LC7749-35N,分析了其结构、力学性能并与国内外同类产品进行了对比。结果表明,各项性能达到指标要求,满足客户使用要求。     

超高压反应器泄漏声发射检测技术的应用

采用声发射检测技术,对某塑料厂发生泄漏的超高压管式反应器进行检测。检测中利用伪Margenau-Hill分布时频分析方法,获取泄漏喷流噪声信号与流动噪声信号在时频分布上的区别,实现泄漏声信号的准确识别。结合声发射信号参量分析和连续型声信号区域定位方法,确定泄漏发生在1#管弯曲段。经拆下检查,证明了检测结果的准确性。     

Unipol气相流化床PP工艺的工业应用

阐述了Unipol气相流化床聚丙烯的工艺流程及技术特点,介绍了Unipol气相流化床工艺在国内同等规模的A公司和B公司聚丙烯装置上的工业标定情况,分析了装置的工业标定结果。结果表明:A公司和B公司装置运行平稳,各项操作均达到规定值,产品质量符合指标要求。针对聚丙烯生产过程中出现的催化剂活性降低、聚合物结块和氢气中CO含量高的问题,通过加强原料丙烯的精制、控制反应器内静电产生和流化状态、增设氢气脱CO系统等措施,促进了聚丙烯装置的长周期运行。     

低碳钢腐蚀声发射检测实验研究

应用声发射技术,对低碳钢均匀腐蚀过程进行了检测,获取了低碳钢均匀腐蚀过程中的腐蚀声发射信号,并应用特征参量和小波包变换相结合的方法,分析了低碳钢腐蚀过程的声发射信号特性,同时结合储罐现场检测数据进行分析,对比实验条件下低碳钢腐蚀声发射信号与实际条件下储罐罐底腐蚀声发射信号的参数特征,其结果为低碳钢均匀腐蚀过程的声发射特征研究和储罐在线声发射检测提供了参考。     

基于小波包分析和K-OPLS的集成方法在颗粒粒径分布检测中的应用

颗粒粒径分布的实时在线检测对于调控气固流化床中颗粒的流化特性具有重要意义。基于混料均匀设计法安排实验,以声发射(AE)技术为检测手段,结合小波包分析,提出采用K-OPLS方法构建颗粒粒径分布的声信号预测模型,定量描述小波包能量特征与颗粒粒径分布的非线性变化规律。实验结果显示,留一交叉验证法的均方根误差(RMSE)仅为0.063,表明基于K-OPLS的颗粒粒径分布声信号预测模型能准确测量气固流化床中颗粒的粒径分布,具有良好的工业应用前景。     

烯烃聚合流化床反应器内动结块的声发射检测

烯烃聚合流化床反应器近分布板区域的动结块是分布板堵塞的诱因,严重影响流化床的正常操作,甚至引发事故。本文在冷模实验装置中,使用声发射技术对近分布板区域的动结块进行检测,分别对比了正常流化、加入丝状结块和加入块状结块时近分布板区域声信号能量和频谱的差异。实验发现,与正常流化时相比,加入结块使得声信号能量下降,且加入块状结块时声信号能量下降更为显著;加入结块后声信号频谱的低频部分（0~20 kHz）和高频部分（70~150 kHz）均出现不同程度的降低,且高频部分下降比低频部分更为显著,块状结块导致的下降比丝状结块更为显著。实验结果表明,声发射技术可以用于流化床反应器内近分布板区域动结块的检测。     

声发射技术在多层包扎压力容器检测中的应用

简要阐述了声发射检测技术的内容,对声发射信号在多层包扎压力容器中的传播途径做出了分析,提出了利用声发射技术,进行多层包扎压力容器检测的重点要素,并对所涉及到的声发射信号处理方法做出了探讨,旨在为声发射检测技术的愈加完善,提供出可供参考和借鉴的内容。     

声发射信号分析与旋风分离器内颗粒粒径测量

采用声发射检测技术,在颗粒碰撞壁面产生声发射信号的机理上,结合小波算法,建立旋风分离器中固相颗粒粒径的声发射预测模型。在旋风分离器中,分别考察4种不同粒径的活性炭颗粒在0.137,0.214,0.296 m/s3个气相条件下的声发射信号,在流态稳定情况下,在0—500 k Hz采样频率范围内对声发射信号做二阶Daubechies9尺度小波分解,得到代表固体颗粒粒径的特征频段。实验发现特征频段下的声发射信号能量与气相速度的二次方、固相颗粒粒径存在线性关系。固相颗粒粒径的声发射模型的计算值与实际测量值之间的平均相对误差为14.3%,表明声发射技术能够实现固相颗粒粒径的准确、非侵入式的实时在线测量。     

基于声发射信号递归分析的气固流化床流型转变

利用声发射技术采集不同流化气速下流化床内颗粒与壁面碰撞的声信号,结合声能量及递归分析法研究不同流型下颗粒运动特征,得到鼓泡流态化到湍动流态化的临界转变速度及流型转变规律。特别是针对声能量分析无法准确区分不同床层高度处流型转变的不足,利用递归分析可有效预测系统周期性的特点,将声信号进行递归分析,研究了流化床不同位置的流型转变性质。结果表明,鼓泡流态化下颗粒运动的周期性较湍动流态化强,并能够清晰地检测到由鼓泡流态化向湍动流态化的流型转变速度,而且床层较低处的流型转变速度比床层较高处大。由此获得了一种便捷灵敏、安全环保的非侵入式流化床流型转变速度的测量技术,可用于对整个流化床内不同位置流型转变过程的实时在线监控。     

气固流化床中声发射和流动模式关系

颗粒在气固流化床壁面区域（或局部空间区域）碰撞产生的声波能量反映了颗粒的碰撞速度和频率（活跃程度）,从中可以揭示流化床内颗粒的流动混合模式。通过在φ150mm流化床冷模装置中,对聚乙烯颗粒－空气体系进行流态化实验,运用声发射技术测得声能量沿气固流化床的轴向分布,继而获得了颗粒的流动模式,并发现其与颗粒粒径、表观气速和分布板形式密切相关。对于颗粒粒径为460 μm的聚乙烯颗粒,当表观气速在0.3～0.7 m·s^-1内,其对应的流动模式为带有滞留区的双循环流动模式。如果气速增大到0.8 m·s^-1以上时,流动模式将转化为无滞留区的单循环流动模式。而当颗粒平均粒径降为365μm,对应的双循环流动模式蜕化为单循环模式,壁面不存在滞留区。进一步发现,滞留区位置与静床高无关。研究同时发现,颗粒的流动模式和分布板形式密切相关,对于在多孔平板分布板下为单循环流动模式的小粒径颗粒,在锥帽式分布板下,则在稍高气速时表现为双循环流动模式。     

流化床冷凝模式操作与乙烯聚合过程的研究Ⅱ露点提高组分对流化床反应器运行状态的影响

以Ｕｎｉｐｏｌ气相法乙烯聚合工艺作为流化床反应器冷凝模式操作的一个实例,通过模拟计算考察了在不同的操作负荷下,进反应器的循环物流的露点、组成和温度对反应器运行状态的影响,并对反应器运行的稳定性作了初步探讨。     

Characterization on hydrodynamic behavior in liquid‐containing gas‐solid fluidized bed reactor

In many industrial processes involving gas–solid fluidized bed rectors, the addition of a liquid phase significantly alters the hydrodynamics. To fully characterize the hydrodynamics in the fluidized bed, pressure and acoustic measuring techniques were applied to study the behavior of gas bubbles and particles. A camera was used to take pictures to verify the pressure and acoustic results. During the liquid‐addition process, the pressure technique captured the bubble size variation and bubble motion while the acoustic technique reflected particle motion and particle size growth. Hurst and V‐statistics analyses of acoustic emission were used for the first time to detect periodic behavior during the injection process. The new break formation and change trend of V_max were used as the criteria to judge occurrence of abnormal fluidization states, such as agglomeration and gas channeling formation. These measurement techniques are beneficial in the elimination of adverse effects caused by the addition of liquid. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1056–1065, 2013     

Characterization of flow regime transition and particle motion using acoustic emission measurement in a gas‐solid fluidized bed

Particle motion is a major determinant of the dynamical performance of a fluidized bed. It plays an important role in determining and optimizing the complex correlation of fluidization condition between particle‐particle and particle‐environment in a system. A passive acoustic emission (AE) technique is applied to monitor, characterize, and control the fluidization condition of polyethylene particles in a gas‐solid fluidized bed. Experimental results show that AE signals are very sensitive to the particle movements by analyzing energy distribution, which can help to understand the status of the system. The AE energy temporal analysis is further used to identify the transition of flow regimes. Moreover, the activity of particle motion can be quantitatively determined by using a combination of granular temperature and AE spatial energy analysis. This work provides valuable insights into the dynamic behavior of particles in a gas‐solid fluidized bed based on AE technique. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

声波的多尺度分解与气固流化床故障检测

引言 在流化床乙烯气相聚合过程中,由于传热速率较低(与淤浆工艺相比),聚合物小颗粒容易聚集在一起形成结块,若不及时采取措施,将影响流化状态.而不良的流化状况经常导致装置不能满负荷、长周期地运转,严重时会"熔床",继而停产.为了保证流化床长期稳定的运行,聚合物颗粒结块的监测就变得十分重要.目前工业生产中主要根据流化松密度、反应温度、床高等参数的突变和γ射线法来检测结块.前者多依赖人为经验的判断,漏报、误报的情况时有发生.而γ射线法则对人体存在致命的伤害.因此,发展一种简单快捷、灵敏准确、安全环保的结块测量技术成为当务之急.     

Unipol气相法聚烯烃液体催化剂技术进展

介绍了Unipol气相法聚烯烃工艺液体催化剂的成分、加入反应器的方式和喷嘴结构及控制催化剂液滴尺寸方法等方面的最新进展情况。     

A Novel Model for Predicting the Dense Phase Behavior of 3D Gas‐Solid Fluidized Beds

A novel phenomenological discrete bubble model was developed and tested for prediction of the hydrodynamic behavior of the dense phase of a 3D gas‐solid cylindrical fluidized bed. The mirror image technique was applied to take into account the effects of the bed wall. The simulation results were validated against experimental data reported in the literature that were obtained by positron emission particle tracking. The time‐averaged velocity profiles of particles predicted by the developed model were found to agree well with experimental data. The initial bubble diameter had no significant influence on the time‐averaged circulating pattern of solids in the bed. The model predictions clearly indicate that the developed model can fairly predict the hydrodynamic behavior of the dense phase of 3D gas‐solid cylindrical fluidized beds.     

CFD simulation study of the effect of baffles on the fluidized bed for hydrogenation of silicon tetrachloride

In this study, the effect of channel baffles and louver baffles on the flow pattern in the large-scale industrial fluidized beds was studied by computational fluid dynamics (CFD) methods. Then, the effect of flow pattern on the chemical reaction performance was studied for the first time. Simulation results showed that the gas velocity distributed more uniformly, solid particles dispersed more homogeneously and aggregation scarcely occurred in the fluidized bed with louver baffles than that with channel baffles. The residence time distribution indicated that louver baffles remarkably suppressed gas back-mixing in comparison with channel baffles. The reasonable agreements of pressure distribution and reaction results between the simulation in the bed with channel baffles and the data on a large-scale industrial apparatus demonstrated the accuracy of the CFD model. The predicted conversion of SiCl₄ in the bed with louver baffles (27.44%) was higher than that with channel baffles (22.69%), indicating that louver baffles markedly improved the performance of the fluidized bed. This study could provide useful information for future structural improvements of baffles in large-scale fluidized beds.     

循环流化床气体返混及停留时间的分布

本文采用脉冲示踪技术,研究了直径140 mm循环流化床内气体的返混特性及其停留时间分布规律,并通过一维轴向扩散模型,得到了气体轴向扩散系数。实验结果表明,在循环流态化条件下,气体轴向流动明显偏离于平推流,并且随操作气速增大或颗粒循环速率的减小,气体轴向返混程度减小。