高温环境下催化裂化催化剂磨损状况的研究

为研究流化催化裂化(FCC)催化剂在高温环境下的磨损行为,在一套固定流化床装置中考察了FCC平衡剂CGP-I在500℃和600℃高温环境下磨损率的时变关系和过孔气速对磨损率的影响,分别从颗粒形貌、磨损动力学等方面对催化剂的磨损机制进行了研究。结果表明:随着磨损时间的延长,磨损速率逐渐下降;随着磨损温度和孔气速的增加,磨损率增大。通过分析结果并与Gwyn磨损动力学方程比较建立了宏观磨损平衡方程,整个磨损过程可近似看作一级不可逆过程,该催化剂磨损率随磨损时间和孔气速的升高呈指数关系增加,高温环境下催化剂的磨损行为主要受表层磨损机制支配。     

煤沥青球气固流化磨损特性实验研究

固体颗粒的流化磨损是流态化技术重要的基础问题之一,气固流动过程中颗粒的磨损特性以及两种磨损机制的研究,对流态化技术的应用具有重要意义。针对煤沥青球设计可视化冷态流化实验系统,研究表观气速、初始粒径和高径比对颗粒流化磨损行为的影响,探讨颗粒流化磨损机理。结果表明：经过流化磨损后,仍在初始粒径范围内的煤沥青颗粒球形度增加,表面更光滑;流化磨损过程受到体相断裂和表面剥层两种磨损机制的共同作用：高速磨损阶段由表面剥层主导,低速磨损阶段表面剥层和体相断裂同时存在,稳态阶段再次由表面剥层主导;提高表观气速和高径比、降低初始粒径均会加剧流化磨损过程,流化数从2.7增加到3.9,体相断裂和表面剥层程度分别增加了3.6%和1.4%。     

声场流化床流动特性研究进展

声场流化床是将声场引入普通流化床,采用颗粒为床层介质的流固相处理系统。声波可以有效降低颗粒聚团尺寸,显著改善超细颗粒的流化质量。本文介绍了声场流化床的基本原理以及近年来在基础研究和应用方面取得的进展及成果,综述了声场流化床在流体力学特性、颗粒特性、声场参数、流态化模型、颗粒团聚以及流化质量机理等方面的研究,并对声场流化床目前存在的问题及发展趋势提出了一些建议。     

喷雾流化床颗粒包衣的研究进展

对近年来喷雾流化床颗粒包衣过程的主要试验研究成果以及颗粒包衣的成长动力学模型的研究进展进行了综述。对影响喷雾流化床颗粒包衣过程的主要因素：流化气速度、流化气温度与湿度以及喷雾速率和雾滴大小的作用机理进行了分析，并对今后的研究方向作了展望。     

石英砂流化床床料磨损的数学模型

针对石英砂流化床床料磨损问题,从磨损的机理出发,基于Fleischer关于摩擦磨损的系统能量平衡理论建立了一种磨损数学模型。磨损细颗粒脱离母体颗粒的磨损破坏条件是依据材料动力破坏的最小能量原理。该模型考虑了床料颗粒在流化床的运行特点和颗粒的物理性质,能够反映流化床床料磨损的一些物理意义,且模型计算结果与实验数据吻合较好。     

石英砂流化床床料的磨损实验与灰色关联分析

针对工业装置运行中的实际问题,在综合热态流化床实验台上研究了不同运行参数下石英砂的磨损规律.实验的设计采用正交实验方法,研究不同运行参数（初始颗粒平均直径、床温、流化数、床料高度）对石英砂床料磨损的影响并作灰色关联分析,得到各运行参数的影响程度排序为：初始颗粒平均直径>床温>流化数>床料高度.     

循环流化床锅炉炉膛受热面的磨损分析

循环流化床锅炉以炉内、外循环相结合的方式燃烧,燃料处于流化状态。燃料适应范围广,多以低热值煤泥、煤矸石、混煤等作为燃料提供热量,燃料颗粒度大,通常d50约为8mm。炉膛受热面的磨损是影响循环流化床锅炉的寿命、长周期运行的重要因素之一。本文以某300MW/h循环流化床锅炉为例,从磨损机理出发,以炉膛内部燃料的运动形式分析各区域的磨损,同时对类似区域的磨损进行比较,得出最优的防磨方式。     

基于机器学习的气固流化床最小流化速度预测

气固流化床以其高效、可灵活操作等优点广泛应用于煤化工、煤燃烧和煤炭分选等领域。最小流化速度作为气固流化床最主要的操作参数之一,与流化床的操作设计紧密相关。现有的最小流化速度预测模型大多为经验或半经验公式,其准确性和便捷性还存在较大问题。为准确预测气固流化床最小流化速度,基于机器学习建立气固流化床最小流化速度预测模型,并探索模型的内部信息。从颗粒性质与设备条件等方面综合考虑,研究气固流化床的最小流化速度,以系统评估对最小流化速度的综合影响。采用随机森林模型验证了其预测最小流化速度的可行性,并考察了设备参数、颗粒密度和颗粒粒度3个影响因素在预测最小流化速度时的相对重要性。结果表明,最小流化速度与颗粒粒径、颗粒密度和床体直径均呈正相关,皮尔逊相关系数分别为0.79、0.31、0.14,颗粒粒径与最小流化速度相关性最强。随机森林能够根据颗粒性质(密度、粒度)与床体直径准确预测最小流化速度,模型的决定系数达到0.875。特征相关性分析揭示了各特征因素对目标变量的影响方式,颗粒粒度与最小流化速度相关性最强,为预测气固流化床最小流化速度提供借鉴。     

汽-液-固循环流化床蒸发器颗粒磨损特性

在不同循环流量和固含率条件下,通过1～2个月的操作运行实验,得到了汽-液-固三相循环流化床蒸发器内聚乙烯颗粒的磨损产物,分析了三相流化床的固含率和循环流量等条件对颗粒磨损速率、磨损粉体的直径和多分散度的影响,并探讨了颗粒磨损的机理。结果表明：磨损产物的粒径呈现三峰对数-正态分布,具有混合磨损机理特征;颗粒的磨损速率随固含率的减小和循环流量的增加而增大;较低固含率条件下,循环流量对颗粒的磨损速率影响较大;磨损速率随着运行时间的延长而减小;磨损粉体的粒径随固含率、循环流量、磨损时间的增加而减小;磨损颗粒的多分散度随固含率和循环流量的增加而减小。     

大颗粒流态化特性的实验研究

通过对大颗粒流化曲线及床层高度的测试对大颗粒流化床的流化过程进行了研究。结果显示,大颗粒的流态化过程是一个渐进的过程,整个流化过程可以分为:床层高度恒定、颗粒位置调整、表面颗粒运动、节涌波动和完全流化5个阶段。由于颗粒自身特性的影响,导致大颗粒流化过程中的各个特征速度(如起始鼓泡流化速度和完全流化速度)产生了有别于小颗粒流化床的特性。     

Particle attrition mechanism with a sonic gas jet injected into a fluidized bed

High velocity gas jets in fluidized beds provide substantial particle attrition: they are used industrially to control the particle size in fluid bed cokers and to grind products such as toner, pharmaceutical or pigment powders. One method to control the size of the particles in the bed is to use an attrition nozzle, which injects high velocity gas and grinds the particles together. An important aspect of particle attrition is the understanding and modeling of the particle breakage mechanisms. The objective of this study is to develop a model to describe particle attrition when a sonic velocity gas jet is injected into a fluidized bed, and to verify the results using experimental data. The model predicts the particle size distribution of ground particles, the particle breakage frequency, and the proportion of original particles in the bed which were not ground. It was found that the particle breakage frequency can be used to predict the attrition results in different bed sizes. A correlation was also developed, which uses the attrition nozzle operating conditions such as gas density and equivalent speed of sound to predict the mass of particles broken per unit time.     

Jet cup attrition testing

Jet cup attrition testing is a common method for evaluating particle attrition in fixed fluidized beds and circulating fluidized beds. An attrition index, calculated from jet cup data, is used to compare with one or more reference materials. However, this method is far from perfect despite its popularity. Results obtained at Particulate Solid Research, Inc. (PSRI) in different-sized jet cups and a 29-cm (11.5-in.) diameter fluidized bed test unit did not provide the same ranking of catalyst with respect to particle attrition. To obtain a better understanding of attrition in a jet cup, both computational fluid dynamics (CFD) and cold flow studies were performed with a 2.5-cm (1-in.) diameter Davison-type jet cup and PSRI's cylindrical 7.6-cm (3-in.) diameter jet cup. Results showed that a significant amount of material in the Davison and PSRI jet cup remained stagnant. Based on these results and additional CFD modeling, PSRI designed a new jet cup, where most of the material was hydrodynamically active. The new jet cup showed a 25% increase in attrition compared to PSRI's cylindrical jet cup under similar conditions and run times. Results were also compared to cyclone attrition data for several materials at PSRI. The new jet cup provided data that correlated with attrition results from the 29-cm (11.5-in.) diameter fluidized bed unit.     

流化床与固定床耦合反应器中的颗粒磨损

在直径50mm的冷模流化床与固定床耦合反应器中,考察了活性炭颗粒在130～150℃及不同气速下的磨损情况,得到了不同气速下固定床中圆柱状颗粒的磨损率随时间的变化关系,同时分析了滞留在流化床、固定床及袋滤器中的细颗粒在不同气速下的粒径分布与质量分布.结果表明,颗粒在该耦合反应器中磨损严重,在0.212～0.424m/s气速下,固定床中颗粒质量损失可达3%～4%,流化床中颗粒平均粒径由200μm降至100μm以下.     

Effect of the grid-velocity on attrition in gas fluidized beds

Changes in particle size distribution play an important role in fluidized bed processes, and these changes are dominated by elutriation and carryover of fines and by attrition or agglomeration. In this study on attrition in gas-fluidized beds, we found that the attrition is a function of the particle size distribution, the jet velocities and the overall superficial gas velocity. Empirical equations have been developed to predict the attrition rate.     

Attrition of char agglomerates

A 15.2 cm diameter fluidized bed system with single- and multiple-jet distributors was designed and constructed to study the attrition behavior and mechanism of Kentucky No. 9 char from IGT's U-GAS fluidized bed gasifier. The effects of the jet and auxiliary gas velocities, the number of jets, the bed height, and the roughness of the fluidized bed wall on the attrition of char particles were studied. Particle shape variation during attrition was calculated by comparing our experimental data on pressure drop for a packed bed with the Ergun equation prediction. A mathematical procedure was developed to translate the size distribution variation of particles in the fluidized bed to the attrition rate expression.     

Influence of hydrodynamic parameters on particle attrition during fluidization at high temperature

In a fluidized bed, attrition both increases the number of particles and reduces particle size, which may affect reactor performance, fluidizing properties, operating stability and operating costs. Most fluidized applications are conducted at high temperature, but in the past most attrition correlations were performed at room temperature, so the attrition rate at high temperature could not be predicted. In contrast, this study investigates the attrition rate of fluidized materials at high temperature. Silica sand was used as the bed material; the operating parameters included temperature, particle size, static bed height and gas velocity to assess the attrition rate. Then an appropriate correlation was developed by regression analysis to predict attrition rate at high temperature. Experimental results indicated that the attrition rate increases with increasing temperature. In addition, the particle attrition increased as average particle size decreased because the probability of collision increases with surface area. The attrition rate increased with increasing gas velocity because of increased kinetic stress of particle movement. The actual density and viscosity of air at specific fluidization temperature were modified and an Ar number was introduced to fit our experimental data. The experimental correction agrees with the experimental results, which can predict particle attrition rate at high temperatures.