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。     

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。     

特定生产现场纳米粉体泄漏扩散的数值模拟

运用计算流体动力学软件FLUENT对某厂生产厂房内纳米粉体泄漏扩散进行模拟,分析大气风速、射流方向对粉体泄漏的扩散浓度和危险性区域的影响。结果表明:大气主导风速对气体扩散浓度和危险性区域影响较大,射流方向和风速一致时,vx=-3 m/s比在vx=-1 m/s条件下危险性区域扩大4 m,分析得出vx=-2 m/s时,扩散区域在x=28～35 m,y=25～28 m,z=1～4 m内。采用三维激光多普勒测速技术,对生产现场100∶1缩微模型进行速度场测量,并将测量结果与数值模拟结果进行对比。结果表明:两者颗粒速度基本吻合,说明采用计算流体动力学技术对生产现场纳米粉体泄漏扩散行为的模拟是可行的。     

防暴弹室内爆炸扩散试验及刺激剂浓度预测

为研究室内环境中不同初始风场条件对刺激剂防暴弹威力效能的影响,在尺寸为10.9 m×9.1 m×3.28 m的平房内开展了三种不同送风速度下(1.0 m/s、1.2 m/s和1.5 m/s)OC刺激剂防暴弹的爆炸扩散试验.首先在室内空间中布置36个采样点,采用智能多路气体采样器采集刺激剂并计算采样点浓度.接着对不同风速、不同时间、不同空间位置的试验浓度数据进行分析,从而得到爆炸后刺激剂浓度在时空中的分布规律及其在不同送风条件下的影响规律.可得到如下结论:刺激剂在爆炸作用下形成的气溶胶会受到室内风场的影响呈现浓度差,浓度由上风口至下风口逐渐升高;刺激剂气溶胶颗粒受重力影响向低处聚集,室内低处刺激剂浓度较高;初始流场的风速大小对刺激剂气溶胶颗粒扩散效果影响较大,一定范围内,风速越大刺激剂扩散速度越快.在此基础上,以试验数据作为训练样本,采用BP神经网络方法建立了1.0～1.5 m/s速度范围内的浓度预测模型.通过对比试验数据得到该模型预测误差为5％,并应用该模型开展了相关预测,结果表明:在送风速度为1.0～1.5 m/s的范围内,测点的浓度值随风速的增加而基本呈线性降低,且高度1.5 m的测点浓度值高于高度为0.5 m的测点,2.5 m高度处的测点浓度最低.     

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。     

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，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相同的３种不同粒径分布的玻璃珠颗粒在相同操作气上的颗粒时均速度、脉动速度与数量密度的截面分布特性；     

带有内置过滤元件的流化床浓相区颗粒浓度及其功率谱分析研究

:IGCC(整体煤气化联合循环 )、PFBC(增压流化床联合循环 )等新型、高效的能源清洁转换系统都需要一套运行可靠、高效、维护简单的高温或常温气体净化装置。本文利用光导纤维浓度测试仪对带有内置过滤元件的三维流化床实验台的流动进行了实验研究。运用FFT方法对颗粒浓度时间序列进行了大量的概率分析和统计。结果表明 ,局部颗粒浓度、L阀、卸料口的位置和气 -固混合特性对颗粒层的形成有重要影响 ,床内气固混合以低频为主 ,在距离布风板z =2 5 0mm附近颗粒浓度较高 ,混合较好 ;径向在壁面附近、边角处颗粒浓度较高 ,混合较好     

高炉渣余热裂解轮胎颗粒流化床的设计及实验研究

针对抗降解性很强的废旧轮胎与余热利用不充分的高炉渣,设计一种利用高炉渣余热裂解废旧轮胎颗粒的流化床;根据废旧轮胎颗粒与高炉渣颗粒的特性确定流化床的操作气速与尺寸大小;通过冷态实验确定流化床的操作气速为2 m/s。热态实验表明高炉渣余热裂解轮胎颗粒流化床的产油率可以达到42%。通过冷态与热态实验验证流化床设计参数的合理性。     

液-固流化床最小流态化速度的数值模拟与验证

为使用计算颗粒流体力学(CPFD)的数值模拟法代替实验法，建立单管的液-固两相流化床实验系统；实验测量5种颗粒的最小流化速度；应用CPFD方法对单管液-固流化床模型进行数值模拟，比较5种颗粒的最小流态化速度的实验值与模拟值，并进行误差分析，验证数值模拟方法的正确性。结果表明：5种实验颗粒的最小流态化速度实验值分别为0.021 6、 0.036 7、 0.029 3、 0.055 5、 0.084 5 m/s; 2种公式验算值与实验值的最大相对误差小于10%,平均相对误差小于5%,证明实验结果是可靠的；5种模拟颗粒的最小流态化速度模拟修正值分别为0.024、 0.044、 0.041、 0.069、 0.062 m/s;颗粒S₁、 S₂、 S₄、 S₅的模拟修正值与颗粒E₁、 E₂、 E₄、 E₅的实验值之间的最小流态化速度的误差分别为11.1%、 19.9%、 24.3%、 26.6%,均为正向偏差且在工程允许范...     

温度场对供料器管道内颗粒分布影响的CFD模拟

建立供料器管道内气固两相流的物理和数学模型,采用Fluent 2020 R2软件中的离散相模型(DPM)模拟供料器管道中温度场、压力流场和颗粒分布情况,搭建气力式混合机实验平台进行压力测试验证,并将考虑温度场和不考虑温度场影响时的仿真结果进行对比,研究温度场对供料器内颗粒分布的影响规律。结果表明:在供料器管道中,气相与颗粒相初始温度不同,气固两相流进行热量交换后温度逐渐趋向一致;考虑温度场影响时管道内的绝对压降大于不考虑温度场影响时,而且与实验测量值的误差仅为16%左右;在两侧管道出口段,随着Z轴向距离的增加,颗粒质量浓度分布从管道圆截面中心处低、壁周面高逐渐变为整个管道圆截面上近似均匀分布;相较于不考虑温度影响时的情况,考虑温度场影响时管道圆截面中心处的颗粒质量浓度降低了3.0%～8.7%,在管道圆截面上形成稳定均匀的颗粒质量浓度分布所需要的Z轴向距离要长。     

基于GSA-SVM的循环流化床锅炉NOx排放特性模型

为了准确地预测循环流化床锅炉NOx排放量,以某热电厂循环流化床锅炉燃烧数据为样本,提出了基于支持向量机（SVM）的循环流化床锅炉NOx排放特性GSA-SVM模型。由于SVM精度及泛化能力依赖于参数选择,故将万有引力搜索算法（GSA）运用到模型参数寻优过程中,利用不同工况下的样本数据检验了模型的预测性能,并将该模型分别与BP神经网络、粒子群(PSO)和遗传算法(GA)优化的SVM模型进行比较,仿真实验证明GSA-SVM模型具有很好的辨识能力及良好的泛化能力。     

On the Cluster Structure of a Circulating Fluidized Bed

A model of a bottom fluidized bed has been developed, in which the latter is represented as an ensemble of uniformly distributed spherical clusters. Using Ergun’s formula, we obtained the dependence for calculating the diameter of a cluster. The results were compared with experimental data on the sizes of clusters in the transport zone of a circulating fluidized bed. In the framework of this model, a correlation to calculate the rate of filtration at which the bottom layer disappears has been obtained.__________Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 2, pp. 104–110, March–April, 2005.     

Mixing of Particles in a Circulating Fluidized Bed

A phenomenological model of longitudinal mixing of particles in a circulating fluidized bed is formulated. The model allows for the main features of the process: ascending motion of particles in the core of the bed and their descending motion in the annular zone (internal circulation of the solid phase); considerable changes in the concentration of particles and in the values of the ascending and descending zones over the bed height; external circulation of the solid phase and the effect of the nearbottom fluidized bed on the process as a whole. The validity of the initial proposition is confirmed by comparison of calculated and experimental curves of mixing.     

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。     

3D simulation on pressurized oxy-fuel combustion of coal in fluidized bed

Pressurized oxy-fuel combustion technology is considered as a perspective carbon capture technology in industrial process. A computational fluid dynamics (CFD) model based on Multi-Phase Particle-In-Cell (MP–PIC) method was developed to predict pressurized oxy-coal combustion process in fluidized bed. The heterogeneous and homogeneous combustion reactions of coal were considered in this model. The predicted results were validated the accuracy of this model with experimental data from a 15 kW_th pressurized fluidized bed combustor in terms of the gas component and temperature characteristics. The characteristics of gas–solid flow and combustion under different pressure (0.1–2 MPa) and oxygen atmosphere were studied in this work. The predicted results show that the intensity of particle motion and the expansion degree in the fluidized bed was gradually decreased with an increase in pressure. A correlation was proposed based on the simulation results to maintain suitable fluidization conditions in pressurized circulating fluidized bed at different pressures. The temperature of particle phase region gradually increased with combustion pressure and inlet O₂ concentration increased. In addition, the CO₂ concentration in outlet increased while the emission of CO and NO_x decreased as the combustion pressure increased.     

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.     

Fluidization of molten salt fluid-particles using low density ratio kinetic theory of granular flow

To deduce and analyze the hydrodynamics of molten salt fluid and particles, computational simulations were performed using a low density ratio kinetic theory of granular flow with two-fluid model in a fluidized bed. Two types of transition fluidization of molten salt fluid-particle mixtures were found in the fluidized bed. One represented the coexistence of wave-like flow at the bottom regime and large scale turbulent regime with chunk-like flow at the bed upper. The other characterized the coexistence of particulate fluidization near the bottom regime and particle aggregations at the upper part along bed height. The molten salt fluid-particle mixtures transited from particulate fluidization to transition state with increasing molten salt fluid temperatures, inlet fluid velocities and particle diameters and densities. The computed expansion heights and fluid volume fractions agreed with measured data in a water-particles fluidized bed.     

多流程循环流化床技术在综合能源服务中的应用

园区级的清洁供热是目前综合能源服务中需要迫切解决的问题。多流程循环流化床技术采用"三床两返多流程"的结构设计,解决了传统的循环流化床锅炉小型化的问题。工业实践证明,多流程循环流化床锅炉可以选用生物质、工业固体废弃物、煤炭等作为燃料,针对多种燃料的热效率达到88%~92%,且污染物排放均达到了国家和地方标准中对排放浓度限值的要求。多流程循环流化床技术具有分散能源分散利用、多种燃料同时适用的优势,可以有效地为园区级的综合能源服务提供帮助。