油页岩循环流化床燃烧室密相区物料颗粒与燃烧特性

在 65t/h油页岩循环流化床锅炉上进行了燃烧室密相区物料特性与燃烧特性的工业试验。得到了极具片状结构特点的油页岩颗粒特性 ,经燃烧破碎磨损后的密相区床料和循环物料的颗粒特性与燃烧特性及相应的锅炉运行参数。试验结果对油页岩循环流化床锅炉的放大设计与运行调节具有一定的参考价值。同时为进一步建立油页岩循环流化床燃烧室密相区的流动、燃烧、传热、磨损、扬析与夹带模型奠定了基础。     

颗粒流化磨损研究进展

介绍了近年来流化磨损测试设备、流化磨损机理以及流化磨损动力学模型等3个方面的研究进展;通过比较单颗粒测试体系和多颗粒测试体系,阐明了多颗粒测试体系更接近工业流化磨损过程,并且介绍了实验室流化床测试设备的发展;概括了颗粒流化磨损的两种典型机理：表面磨损和体相断裂。综述了现有的流化磨损动力学模型,指出了流化磨损时变规律是研究颗粒流化磨损的基础,目前的时变规律模型是分段函数的形式,未能把流化磨损的起始阶段和平衡阶段统一起来;其他磨损模型致力于描述流化气速和流化床结构与磨损速率的关系。指出今后需在时变规律、颗粒性质和鼓泡特征等方面加强对流化磨损的研究,以满足完善流化磨损机理和开发高耐磨损性颗粒材料的需要。     

基于气固流态化原理的油页岩干燥动力学

为了考察气固流化床干燥器能否使油页岩含水质量分数达到要求,以柳树河油页岩颗粒为原料,研究进口气体温度和颗粒直径对油页岩干燥性能的影响,采用薄层干燥模型,对油页岩干燥实验数据进行模拟,确定油页岩干燥方程和干燥速率方程,建立油页岩干燥速率特征常数和有效扩散系数之间的关联式。研究结果表明:薄层干燥模型中修正Page模型Ⅰ适合描述油页岩的干燥过程;油页岩在流化床内干燥过程主要发生在降速干燥阶段,进口气体温度越高,油页岩颗粒直径越小,所需干燥时间越短,进口气体温度为350℃时,使2.4 mm油页岩含水质量分数低于5%,所需干燥时间为2.5 min。     

世界油页岩资源的开发利用现状

油页岩是一种非常规能源,世界储量巨大,作为石油的补充能源,开发前景广阔.油页岩在隔绝空气条件下加热至500℃左右,会热解生成页岩油,经加工处理后可以制得汽油、柴油等油品.油页岩也可直接燃烧,产生蒸气、发电,目前利用油页岩燃烧发电的国家有爱沙尼亚、中国、德国等.本文介绍了世界主要油页岩国家的油页岩储量和加工利用情况,目前世界上利用油页岩干馏制取页岩油的国家主要有3个,中国(产量80万吨)、爱沙尼亚(产量50万吨)和巴西(18万吨),其他国家略有生产.中国页岩油产量一直居世界首位,目前有将近10座油页岩干馏厂投入运行,其中抚顺矿业集团年产页岩油35万吨,全国居首,该公司引进的日处理颗粒油页岩量6000t的ATP干馏工艺,目前已经在调试中阶段性运转,并逐渐延长连续运转时间,山东龙口等其他地方的油页岩加工利用也取得很大进展.美国目前没有进行油页岩干馏炼制页岩油的工业化生产,但有多所大学、公司和研究所已经对油页岩进行了长期的地上和地下干馏工艺的研究和开发.文中还介绍了国内外油页岩干馏的3种主要炉型,分别为块状页岩气体热载体干馏炉、颗粒页岩固体热载体干馏炉和粉末页岩流化干馏炉,并对比了不同国家的干馏炉型的优缺点.     

油页岩循环床锅炉中温分离回输系统Loop Seal工作特性的研究

在目前世界上投入商业运行最大容量的 65t/h油页岩循环流化床锅炉上 ,进行了全尺寸的中温分离系统中LoopSeal型返料装置的工作特性热态试验 ,得到了油页岩循环流化床燃烧中温分离回输系统中LoopSeal型返料装置的运行参数、温度特性及其循环物料的颗粒特性和含碳量分布 ,试验结果对油页岩循环流化床锅炉的放大设计与运行调节具有一定的参考价值     

油页岩固体热载体流化干馏炼油工艺中试研究

介绍了以依兰粉末页岩作原料的页岩流化干流中试装置概况及试验流程,并对试验结果进行了分析。中试结果表明,中试装置页岩油产率为铝甑干馏法的90.15%,经冷凝回收系统及油泥处理后获得的页岩油收率为铝甑的82%;固体热载体流化干馏工艺所产页岩油较轻,337℃以前馏分大于80%。     

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%。     

Model selection for aqueous slurry coal desulphurization

Simple solid-fluid process models developed for uniform size solid bodies (screened or palletized materials), like the shrinking core model, have been applied to multifraction mixtures of solid bodies usually encountered in processing of ground coal or oil shale. The experimental conversion, measuring total effects on all of the size fractions was recalculated to the conversion of the longest surviving single fraction. The calculations used literature data on coal desulphurization by wet oxidation of pyretic sulphur and results are discussed in terms of rate limiting steps.     

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.     

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.     

油页岩循环流化床燃烧特性研究

摘要:在循环流化床燃烧试验台上对油页岩的着火、稳定燃烧、燃尽特性等燃烧特性进行详细地试验方案分析,同时提出了油页岩循环流化床锅炉的设计与运行的特点。根据拟做试验方案进行试验研究,可以测试出油页岩的燃烧特性,为油页岩CFB锅炉燃烧特性的试验研究,以及大型化油页岩循环流化床锅炉的设计提供了借鉴。     

Method for determining the kinetics of cracking and coking of shale oil vapours in fluidized beds

The secondary cracking and coking of oil vapours produced from oil shale retorting have been previously shown to depend upon the nature and temperature of the substrate over which these reactions occur. To realistically examine the kinetics of these reactions during fluidized bed retorting, an apparatus has been developed which permits shale oil vapours generated in one fluidized bed to pass over selected substrates in a second fluidized bed. Substrates can be fed as a batch or continuously. In the batch mode, the substrate is heated to reaction temperature and is then exposed to shale oil vapours for a chosen period of time. Carbon deposition onto the solid is monitored in real-time by combusting the pyrolysis products and measuring the oxides of combustion with an on-line mass spectrometer. The extent of carbon uptake is also determined by elemental analysis of the substrate following reaction. These two methods of analysis were shown to correspond well under all the conditions investigated. In the continuous mode, substantial amounts of product oil can be collected so the effects of cracking may be evaluated. The rates of carbon deposition onto processed shales and pure minerals have been measured.     

流化床用树脂基球形活性炭及其VOCs吸附性能

以聚苯乙烯树脂为原料,采用水蒸气活化、氯化锌活化及水蒸气?氯化锌协同活化方法制备了3种流化床用树脂基球形活性炭,采用固定床反应器考察了活性炭对乙酸乙酯的动态吸附行为,对比了其传质区长度,并利用Yoon?Nelson模型对实验数据进行了拟合. 结果表明,3种活性炭的摩擦磨损指数均小于0.1%,耐磨性能出色,物理、化学协同活化活性炭比表面积高达1702.49 m2/g,对二甲苯的静态吸附容量达0.86 g/g.     

Utilization of Estonian oil shale semicoke

In thermal processing of oil shale in vertical retorts huge quantities of a solid waste — semicoke are formed. It has been shown that circulating fluidized bed combustion of semicoke could be a promising technology allowing utilization of its high residual energy potential. The main parameters of combustion process and the additional heat produced were calculated and verified by combustion tests in a fluidized bed device with a thermal capacity of 50 kW_th. The experiments indicated that semicoke with low moisture content can be burnt directly in fluidized bed. For the combustion of semicoke with higher moisture content (over 10%) about 10% of oil shale must be added. In addition, possibilities for utilizing residual carbon present in semicoke by obtaining carbon-rich materials with further production, for example, activated carbon were discussed. A series of experiments accompanied by SEM and EDAX analysis was carried out in order to elucidate the distribution of carbon and mineral part in semicoke and to find possibilities for their separation and subsequent enrichment. Different separation methods — selective grinding and subsequent screening, pneumatic separation and triboelectroseparation method were analyzed. It was shown that due to close integration of mineral and organic part in semicoke, the separation of carbon-rich ingredients by these methods was not enough effective to obtain enriched products suitable for the production of activated carbon.     

Experimental study on the attrition and size distribution of bed material in a recirculating fluidized bed

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.     

Attrition of spherical electrode carbon particles during batch fluidized combustion

Spherical electrode carbon particles prepared from carbon rods of dry cell batteries have been used to study the attrition behaviour in a bubbling fluidized bed combustor. Experiments have been conducted in a 40 mm I.D. and 1 m high fluidized bed combustor operated at 1 m/s superficial velocity. The bed was operated with nitrogen and with two different oxygen concentrations at 850°C to study the effect of combustion on attrition of these particles. The experimental technique used allowed the time resolution of attrited fines generation, providing detailed curves of attrition rates as a function of time. Attrition rate constants have been evaluated. Results show an enhancement of attrition due to combustion even for spherical, homogeneous and smooth particles.     

An experimental study on the primary fragmentation and attrition of limestones in a fluidized bed

In this paper, an experimental study on the primary fragmentation and attrition of 5 limestones in a fluidized bed was conducted. The intensity of fragmentation and attrition were measured in the same apparatus but at different fluidizing velocities. It was found that the averaged size of the particles decreased by about 10-20% during the fragmentation process. The important factors for particle comminution include limestone types, heating rate, calcination condition and ambient CO₂ concentration. Fragmentation mainly occurred in the first a few minutes in the fluidized bed and it was more intense than that in the muffle furnace at the same temperature. The original size effect was ambiguous, depending on the limestone type. The comminution caused by attrition mainly occurred during calcination process rather than sulphation process. The sulphation process was fragmentation and attrition resisted. The attrition rate of sulphate was similar to that of lime in trend, decaying exponentially with time, but was one-magnitude-order smaller than that of lime. Present experimental results indicate that fragmentation mechanism of the limestone is dominated by CO₂ release instead of thermal stress.     

Particle population model for a fluidized bed with attrition

For a steady-state fluidized process, a population model for particle mixtures undergoing both attrition and reaction is developed. Populations of different materials affect each other through ways such as attrition. The evolution of the attrited fines is more realistically assessed so that the differential solid balance is consistent with the overall mass balance. The possible effects of fines on the attrition and reaction are considered too. Effects of several input and operational conditions on the process performance are discussed and demonstrated by a simulating program. Many particle population models in the literature can be seen as special cases of the present model. The model represents a more realistic approach to the simulation of the fluidized-bed process.     

Experimental and numerical analysis of oil shale drying in fluidized bed

The main objective of this work was to experimentally and numerically investigate the Liu Shu River oil shale drying by the means of flue gas in a fluidized bed dryer. Several experiments were performed under different temperatures conditions. The moisture content of oil shale was measured during the experiments. The two-stage drying model was incorporated in computational fluid dynamics (CFD) package FLUENT via user-defined functions (UDF) and utilized for simulation of heat and mass transfer of oil shale drying in the fluidized bed dryer. The simulation results for solid moisture content agreed well with experimental data. The effects of the temperature and velocity of flue gas, initial bed height, and the particle size on the drying characteristics were predicted and analyzed. It is shown that the gas temperature and velocity are the important parameters in the whole drying process. The particle size has more obvious influence in the falling drying period than the constant drying period. The temperatures of gas and solid phases were monitored. It is shown that the so-called “near gas distributor zone” is the most effective heat transfer zone, which agrees well with the calculated value. The system quickly reached thermal equilibrium, characterizing a nearly isothermal bed. The developed model provides a very good demonstration to describe the oil shale drying in the fluidized bed dryer, and may provide important information for design, optimization of operation conditions.