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《动力工程》2012,32(1)
为准确预测双循环流化床生物质气化的颗粒循环流率Gs,设计并搭建了双循环流化床冷态试验台,研究了提升管流化风速、二次风量、二次风送风方式、二次风口高度及二次风口数量对颗粒循环流率的影响,并建立了基于Levenberg-Marquardt优化算法的BP神经网络预测模型,通过对比找出了最优模型,对颗粒循环流率进行了预测.结果表明:Gs随着提升管流化风速和二次风量的增大而增加,二次风量超过一定值后,增加的趋势变缓;二次风径向引入比切向引入时的Gs大;Gs对二次风口高度的变化十分敏感;应用该BP神经网络模型得出的Gs预测值与试验值的平均偏差为0.07 kg/(m2.s),平均相对误差仅为0.49%,模型准确地预测了提升管送风特性对颗粒循环流率的影响. 相似文献
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采用计算颗粒流体力学(CPFD)方法在直径0.5 m、高8.5 m的高通量循环流化床物理模型上,对分别采用U型和N型返料阀的全回路进行气固流动特性数值模拟研究。对比分析了不同工况下提升管颗粒浓度、物料循环流率和压差梯度分布等,并以此评价返料器的工作性能。循环物料为B类颗粒,初始床料量M_p为380~665 kg。在提升管底部以均匀进气的方式通入流速为1.5~5.5 m/s的空气。结果表明:在采用相同流通面积的U型和N型返料阀的全回路流动中,后者的提升管颗粒浓度更高;在M_p为600 kg时,N型阀最大返料流率为1 220.85 kg/(m~2·s),而U型阀仅能达到904.37 kg/(m~2·s);N型阀设计更满足高通量循环要求,操作弹性大且物料循环稳定。 相似文献
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在一冷态循环流化床实验装置上,考察了一定颗粒原始存料量下,流化风速和回料风量对物料在循环系统中的分布和循环流率的影响.实验结果表明,当固定回料风量时,系统颗粒循环量随着流化风速的增加先增加后有所减少.流化风速较高时,系统将离开了传统的快速床操浊?为在高风速下保持和提高颗粒循环流率,需要进一步提高回料阀的输送能力.当固定流化风速时,回料阀松动风的增加将提高系统颗粒循环流率;但随着料封高度的降低,回料阀向提升管输送的颗粒量趋于稳定.过高的松动风量将破坏正常的料封,这对实际操作是不利的. 相似文献
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为了研究卧式循环床回料器立管高度偏低导致其工作特性可能改变的问题,以12,t/h蒸汽炉的返料器为原型,按照1∶1的比例搭建了冷态回料器实验台.研究了松动风流量、回料风流量、物料性质等对回料器工作性能的影响.实验研究表明,回料量随输送风流量和松动风流量的增加而增加.对于河沙,当输送风流化数接近1.0时,回料质量流率达到饱和,而对稻壳灰只有当输送风流化数接近1.5才达到饱和值.松动风流量越大则饱和值越大,可调节输送风量使其处于饱和区,然后利用松动风控制回料量,该现象可与三极管的工作原理比拟.实验台回料器尺寸、立管高度设计上与实际的工业装置类似,本文成果可供设计工业装置回料系统时参考. 相似文献
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在生物质化学链气化反应基础上设计并搭建了一套串行流化床冷态模型。以石英砂为床料、空气为流化介质,在该冷态装置上开展了压力分布及控制规律试验研究。采用PY500型智能压力检测系统及PV-6型激光颗粒速度测量仪着重研究了循环流化床冷态装置的料层阻力特性及固体循环量,考察了空气反应器、燃料反应器、返料管部件的流化风量对循环状态和流化床内压力分布的影响,获得了串行流化床稳定运行的操作条件和控制规律。试验结果表明,最佳操作状态:燃料反应器流化气速为0.23~0.32 m/s,空气反应器气速为0.42~0.47 m/s,返料管气速为0.07~0.1 m/s,两反应器存料量为2.5~4.5 kg,为热态试验装置的设计、运行提供了参考依据。 相似文献
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The solids acceleration length was investigated in a cold dense transport bed(0.10m-ID×17m-height)with three kinds of silica sand.The solids circulation rate(Gs)was up to 954 kg/(m2s).The effects of operating conditions,particle properties,and riser structures on the solids acceleration length were investigated under high Gs conditions,with the effect of riser height non-negligible.The solids acceleration length increased with the increase of the riser height.Based on the experimental data,an empirical correlation was proposed to predict the solids acceleration length.Predictions of the correlation were in good agreement with the experimental data in this work and those from the literature over a wide range of Gs(18~954kg/(m2s)). 相似文献
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Internal gas-lift loop reactor (IGLR) was used as an anaerobic digester and its hydrodynamics were studied using Computer Automated Radioactive Particle Tracking (CARPT) Technique. This paper deals with the experimental study on a laboratory-scale digester. An anaerobic digester is a three-phase system consisting of gas, liquid, and solids; however solid–liquid slurry was treated as a single phase due to smaller size and lower density of solids. The effect of various geometric and operating variables on the hydrodynamics was studied. The superficial gas velocity was maintained at very low values and IGLR was operated in bubbly flow regime, which is suitable for operation of anaerobic digesters. The flow pattern and liquid velocity profile was obtained and effect of gas superficial velocity, draft tube diameter, type of sparger on liquid velocity and dead volume was studied in detail. Mean circulation times were calculated and compared for different digester configurations. Results showed that the increasing gas velocity increases the liquid velocity, decreases circulation time but does not offer any significant advantages in reducing the dead volumes. The configuration with draft tube diameter to tank diameter ratio of 0.5 showed good liquid circulation throughout the digester volume and low mean circulation time implying better mixing. 相似文献
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双循环流化床提升管二次风特性是影响颗粒循环流率的重要因素。设计并搭建了双循环流化床冷态实验台,通过实验分析了二次风风速、送风方式、风口高度及风口数目对颗粒循环流率的影响。实验表明:对于物料固定粒径、固定静床高时,颗粒循环流率随着二次风速的增加而增加,风速达到一定值后,颗粒循环流率的增加趋势趋于平缓;风速一定时,径向送风比切向给风时颗粒循环流率大,4个二次送风口比2个送风口时颗粒循环流率稍大;二次风口在距布风板15cm时比20cm时颗粒循环流率明显增加,且风口高度对颗粒循环流率的影响随着风速的增加逐渐明显。 相似文献
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隔板式内循环流化床的流动特性研究 总被引:5,自引:1,他引:4
以石英砂和稻壳为实验床料,在隔板式内循环流化床气化炉冷态实验装置上对颗粒的内循环流动特性进行了研究,考察了高速区和低速区的流化速度、结构尺寸和侧风量等对颗粒内循环流动的影响.结果表明:在保持低速区流化速度一定的条件下,随着高速区风速增大,颗粒循环量先增大后减小;流化速度不变的条件下,颗粒循环量随孔口和侧风量的增大而增加,但增加趋势逐渐变缓.实验给出了合理的运行设计参数.通过实验数据回归,得到了石英砂和稻壳通过隔板式内循环流化床孔口的颗粒循环量关联式,计算结果与实验值误差分别小于6%和14%,能较好地预测孔口颗粒流动. 相似文献
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在锥形布风板双循环流化床冷态装置上,研究了提升管风速、气化室风速、物料质量和颗粒粒径对提升管颗粒循环流率的影响,并与水平布风板的结果进行了对比.利用3种改进的BP神经网络算法建立模型来预测循环流率.结果表明:提升管颗粒循环流率随着提升管风速和气化室风速的增大而增大,当风速达到一定值后,增大趋势逐渐平缓;循环流率随着物料质量的增大基本呈线性增大,随着颗粒粒径的增大而明显减小;锥形布风板比水平布风板更具优势,同样条件下可以增大循环流率;BFGS拟牛顿算法的预测效果最佳,其颗粒循环流率预测值与实验值的最大相对误差为7.7035%,平均相对误差为3.5943%. 相似文献
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The coal gasification behaviors in the pressurized high-density circulating fluidized bed under various solids circulation fluxes were studied with the CFD method, which combines the two-fluid model and coal gasification reactions represented by the chemical percolation devolatilization and the MGAS models. The numerical method was validated with two experimental cases, and detailed distributions of gas species and temperature in the riser were illustrated to understand the gasification process. To fully understand the influence of solids circulation flux on the gasification behavior, a series of cases were simulated with the solids flux varying gradually from 260 to 1010 kg/m~2 s, and the composition and quality of syngas were compared between various cases. The higher heating value of syngas firstly increased and then decreased with the increase of solids flux, and it reached the highest value around 480 kg/m~2 s. The influence of solids flux on gasification process was further analyzed through the contours of temperature, solids concentration, and gas composition in the riser. 相似文献
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Wei Dai Haijiang Wang Xiao-Zi Yuan Jonathan Martin Jun Shen Mu Pan Zhiping Luo 《Journal of power sources》2009
Water management in a proton exchange membrane (PEM) fuel cell is one of the critical issues for improving fuel cell performance and durability, and water transport across the gas diffusion layer plays a key role in PEM fuel cell water management. In this work, we investigated the effects of polytetrafluoroethylene (PTFE) content and the application of a micro-porous layer (MPL) in the gas diffusion layer (GDL) on the water transport rate across the GDL. The results show that both PTFE and the MPL play a similar role of restraining water transport. The effects of different carbon loadings in the MPL on water transport were also investigated. The results demonstrate that the higher the carbon loading in the MPL, the more it reduces the water transport rate. Using the given cell hardware and components, the optimized operation conditions can be obtained based on a water balance analysis. 相似文献
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采用“湍动床+快速床”作为煤基化学链燃烧(CLC)系统的空气反应器(AR),鼓泡床作为燃料反应器(FR),设计了流动密封阀和旋风分离器,分别用于隔绝2个反应器之间的气氛和进行气固分离,在冷态试验装置上分析研究了CLC系统的压力分布、固体循环流量、气体泄漏率及煤灰与循环载体的分离效果.结果表明:该串行流化床反应器之间气氛隔绝性良好,气体泄漏率较低,固体循环流量达到甚至超过设计标准,FR二级旋风分离器的分离效率接近100%,FR中煤灰进入AR的质量分数小于1.55%,煤灰分离效果良好;装置可以长时间连续稳定运行,且操作气速范围较广,自行设计建造的循环流化床作为煤基化学链燃烧试验装置是可行的. 相似文献