共查询到19条相似文献,搜索用时 250 毫秒
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循环流化床燃烧条件下煤的成灰磨耗特性是影响床内的流化特性和锅炉整体性能的重要因素之一 .利用静态燃烧然后冷态流化实验方法 ,可以得到给煤的成灰及磨耗参数并提出煤种的本征成灰概念 .在此基础上建立稳态的 CFBC冷态灰平衡模型来研究流化床内物料的粒径分布规律 .分析了流化风速、分离器效率和煤灰的磨耗系数对飞灰、排渣和床料的粒径分布的影响 . 相似文献
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0 前 言循环流化床锅炉 (后称 CFB锅炉 )与常规煤粉炉相比 ,汽水一侧的控制基本相同 ,但床温及床压的控制不同。CFB锅炉的炉膛类似于一个低温的化学反应器 ,一般将密相区物料温度控制在 850~ 90 0℃ ,这是最佳脱硫、脱硝温度 ,床温过低使锅炉燃烧效率下降 ,床温过高则会造成 NOx 及 SOx 排放增多 ,污染环境 ,甚至造成床料结焦 ,影响设备安全运行。1 床温影响因素1 .1 设计因素炉膛传热计算方法不准确 ,没有考虑宽筛分床料的特性 ,导致计算偏差大 ,炉内受热面配置不合理。1 .2 运行因素锅炉的实际运行条件往往同设计不一致 ,尤其是… 相似文献
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连续进出料鼓泡流化床颗粒停留时间分布 总被引:2,自引:0,他引:2
针对双流化床气化或双床热解气化工艺中鼓泡床反应器的设计,采用脉冲法研究了Geldart B类固体颗粒在连续颗粒进料和出料的矩形流化床内的停留时间分布(RTD),考察了气速、床料高度、粒径、物料流率等操作参数对RTD的影响. 结果表明,物料流率、床料高度、粒径是影响颗粒RTD的主要因素,而气速则是次要因素. 随物料流率和粒径增加,鼓泡床内颗粒流动向平推流靠近;随床料高度增加,物料在床内的混合更加充分,颗粒流动向全混流靠近. 根据实验结果,推荐采用比理想平推流时间低9%~18%计算平均颗粒停留时间. 相似文献
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降低循环流化床锅炉飞灰可燃物的探讨与实践 总被引:2,自引:0,他引:2
针对2台燃用福建无烟煤的DG75/3.82-11型CFB锅炉所存在的飞灰可燃物含量较高的问题,通过分析福建无烟煤特有煤质特性、燃料颗粒特性、锅炉总体设计和运行调整工况是影响福建无烟煤在CFB锅炉中燃尽的主要因素。针对性采取优化筛分破碎系统、增强二次风的扰动穿透能力、提高旋风分离器的分离效率、改造回料风系统以减少返料偏流等措施;同时不断摸索CFB锅炉运行规律,完善和优化运行方式,应用锅炉燃烧优化控制系统实现CFB锅炉的自动优化控制运行。2台锅炉平均飞灰可燃物含量从2003年的22.17%降低到2009年第1季度的15.03%。 相似文献
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Hairui Yang Guangxi Yue Xianbin Xiao Junfu Lu Qing Liu 《Chemical engineering science》2005,60(20):5603-5611
An 1D model of the circulating fluidized bed (CFB) boiler is developed specifically to predict the material balance in CFB boiler. This model emphasizes on the important factors that influence the ash balance in CFB boilers, such as ash formation, attrition and size reduction, residence time and segregation in dense bed. The corresponding sub-models are discussed in detail. In the simulation of a 135MWe CFB boiler in Zibo power plant, China, the parameters in mass balance model under full load operation, such as segregation parameters and axial decay constant, are optimized. The model can predict the mass balances at different operating loads in the same boiler. 相似文献
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Fluidized bed combustion of high ash anthracite (HAA) was experimentally studied. The combustor consists of 0.25 m ID bed,
and auxiliary equipments for coal feeding, ash removal, lemperature control, etc. Experimental results elucidate main cause
of fuel loss to be elutriation of fines (i.e., flyash) containing unburned carbon. However, detailed balances of particle
size distribution show majority of carbon in flyash comes from fines contained in the feed instead of attrition of coarse
particles. The latter is the main source of flyash for conventional coal. The difference is due to much smaller attrition
rate of HAA; feed HAA particles do not shrink much in size by combustion and attrition. 相似文献
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An experimental study was performed on the attrition of the bed materials in a recirculating fluidized bed (RCFB) using Indian standard (IS) grade I sand (size between 2.0 and 1.0?mm) at ambient conditions. Experiments were performed with superficial air velocity ranging from 7.13 to 9.16?m/s, bed inventory of 7–10?kg, and a spacing of 0.085?m between the jet top and draft tube bottom. The main objective of the study was to investigate the effects of operation time on the attrition and size distribution of sand particles in a RCFB. It was noticed that the prime mode of attrition of bed materials was abrasion, not fragmentation. Reduction in the downcomer bed height was observed with increasing operation time. It indicates that attrition was significant and fines were elutriated out with the fluidizing air. Furthermore, variations in the shape, size, and harmonic diameter of particles were studied with increasing operation time. It has been observed that the coefficient of uniformity and coefficient of curvature showed increasing patterns. It specifies that particles of different size ranges and fines were formed due to attrition of particles. At the end of the operation, it was found that a significant amount of fines was elutriated with fluidizing air from the reactor. 相似文献
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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. 相似文献
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采用静态燃烧加冷态振筛磨耗方法对4种煤灰的磨耗速率常数进行了测量,发现同类煤灰的磨耗速率常数随其粒径的增加呈指数衰减的规律, 而相同粒径的不同煤灰的磨耗速率常数不同。通过分析煤灰组分,认为煤灰成分差异是造成这一现象的主要原因。基于煤灰成分主要由偏高岭土、石英、氧化铁和氧化钙组成的假设,采用灰色关联和神经网络分析了煤灰主要成分对磨耗速率常数的影响以及趋势,认为氧化钙、氧化铁以及偏高岭土含量的增加能够增大煤灰的磨耗速率常数,而煤灰的磨耗速率常数随氧化硅含量的增加而降低。 相似文献
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In both pressurized and oxygen-enriched fluidized bed combustion the partial pressure of CO2 in the reactor becomes high, which affects SO2 capture by limestone. Both of these technologies are also applicable to decreasing greenhouse gas emissions; the first one by increasing the efficiency of electric energy production and the latter by enabling capture of carbon dioxide for storage.Attrition increases the reaction rate by removing the sulphated layer on the particle, thus reducing the diffusion resistance. In the well-known solution for the shrinking core model the reaction time can be presented as the sum of the contributions of the kinetics and diffusion. It is shown that the effect of attrition can be expressed as an auxiliary term in this expression. A method to extract the diffusivity of the product layer from the SO2 response in a bench-scale fluidized bed test using a limestone sample with a wide particle size distribution is presented. Based on a population balance model, a method to estimate the particle-size-dependent attrition rate from measured particle size distributions of the feed and bed material is illustrated for a 71-MWe pressurized power plant. In addition attrition and its effect on the optimization of the limestone particle size for sulphur capture in oxygen-enriched combustion are discussed. 相似文献
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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。 相似文献