等离子体-喷动流化床性能研究

等离子体-喷动流化床结合了先进的等离子体技术与喷动流化床装置,由流过中心喷口的等离子射流(喷动床)以及通过分配器的辅助流化气流(流化床)组成,目前对等离子体-喷动流化床的操作特性及基本现象研究较少。本研究中,搭建了一套等离子体-喷动流化床装置并进行了性能测试,直流等离子体炬功率12 kW,流化物料采用石英砂颗粒。研究中使用上部内径为198 mm柱状、下部为60°锥体的锥柱形反应器,以等离子体射流作为喷动气流,氮气作为流化气流构成了等离子体-喷动流化床。对比研究了物料在常温下与等离子体条件下在装置内的流动情况;在等离子体状态下研究了喷动流化床内物料的磨损情况;测试了等离子状态下喷动流化床装置内的温度分布。研究结果表明:在等离子体条件下实现物料喷动流化所需的气体流量大大减少,高温区集中于物料喷动流化区,体系的能量利用效率高,该装置适宜进行生物质等离子体热解或气化。     

流化床式生物质快速热解设备监控系统的设计与开发

介绍了自主研发的喷动循环流化床式快速热解技术.通过对流化床式快速热解设备的温度、流量及压力监控方案的研究和设计,把计算机数据采集与控制技术应用于快速热解设备的工程实践中,实现了实时检测和半自动控制,使得热解反应效率提高,同时还增加了快速热解反应操作工艺的安全性.     

稻草快速热解产物气流床气化工艺流程模拟

以生物质能源高效利用为背景,通过自行设计的流化床快速热解装置,改变生物质的物理化学特性,对所获得的热解产物进行了分析,并应用过程模拟软件Aspen Plus对比了不同原料气化的结果。结果显示,利用快速热解可以提高生物质的能量密度,提高气化合成气热值。     

生物质的流化床转化

综述了生物质的流态化特性及生物质的流化床利用,内容包括：生物质在流化床中燃烧,气化以及在流经床中的热解,并介绍了煤与生物质共气化燃烧的最新进展。     

生物质快速热解装置研究进展

当今化石能源日渐枯竭和环境压力日益加重是亟待解决的问题,而生物质热解液化技术被认为是解决能源紧张的潜在方法,尤其是生物质快速热解技术。随着生物质快速热解技术与工艺不断成熟,需要快速热解装置不断放大以提高处理量,以实现生物质快速热解的工业化。生物质快速热解装置复杂且多样化,在装置的放大过程中,各系统的合理选择是难点。本文首先对生物质热解机理、快速热解过程的粒径选择和前处理进行了简述,并对快速热解流程中的进料系统、供能系统、热解反应器和快速冷凝系统4个关键系统进行了综述,着重介绍了快速热解反应器的类型及其特点,提供了该4个关键系统的选择及研究趋势。流化床反应器具有易放大、可以较好地实现自热式快速热解的优点,本文总结出流化床式反应器是目前研究的热点。在保证产品品质下,设备易放大、稳定实现自热式、流程能耗低、运行稳定安全等是快速热解装置未来的研究方向。     

生物质快速热解下行式流化床反应器研究进展

在碳中和目标下，未来发展之路是从化石能源的原料体系转变到可再生能源的原料体系。作为化石资源的重要替代品，生物质是唯一能够大规模取代化石资源的可再生碳资源。生物质快速热解技术是实现生物质资源转化为液体燃料的重要途经，其技术核心是反应器。下行式循环流化床反应器具有产物停留时间短、近平推流性能等优点，在生物质快速热解方面具有广阔的应用前景。本文介绍了流化床反应器的特点及其中试和示范/商业级装置的研究现状，详细总结了下行床反应器的特点、结构、分类及流体力学特性，并分析了目前下行床反应器放大过程中的瓶颈问题以及进一步研究的方向，为推动下行床反应器在生物质快速热解工业应用提供参考。     

流化床式生物质热解过程模拟研究进展

生物质能作为一种可再生的清洁能源,受到国内外研究者越来越多的关注。流化床式生物质热解转化技术是清洁高效转化利用生物质的新方法。本文在分析流化床式生物质热解过程的特征结构基础上,着重对各类热解流化床模拟进展进行了归纳总结。并提出了采用多尺度建模方法来提高生物质热解模拟的计算速度和精度,表明该类模型具有指导生物质热解过程优化与放大的应用潜力。     

生物质快速热解流化床反应器气力进料特性

为探究不同工况下热解流化床反应器的气力进料特性,设计并搭建了流化床反应器气力进料冷态试验装置。生物质原料和床料分别采用落叶松颗粒和石英砂颗粒,通过试验测得了本装置的最小流化速度,研究了流化气速、喷动气速、流量比、初始静床高、石英砂粒径、落叶松粒径对流化床反应器气力进料特性的影响。试验结果表明：流化气速和喷动气速的增加均会提高进料率;流化气使床料流化并为落叶松颗粒提供进料空间,喷动气为落叶松颗粒提供动能,并平衡一部分床层压力;落叶松与石英砂粒径的增加对进料效果不利;流量比在1.9~2.7范围内进料率高且稳定性好。本文构建了生物质、床料与气体的三相流物理及数学模型,开展试验对模型进行验证,结果表明其预测误差为±13%。     

稻壳快速热解制取生物质油的试验研究

目前生物质快速热解高温热解气主要利用间壁式冷却器进行冷凝,容易造成冷却管道的结焦堵塞问题,本试验根据流化床稀相输送特点、生物质的热解特性以及生物质油的冷凝收集特点,设计了生物质快速热解反应装置,改进生物质物快速冷凝系统,以稻壳为原料进行快速热解制取生物质油的试验研究,分别考察单因素反应温度、流化气量以及进料速度对生物质油产率的影响。试验表明:稻壳热解气能够快速顺利地得到冷凝,反应系统能够连续顺利运行,随着反应温度、流化气量、进料速度的增大,生物质油的产率都呈现先增大后减小的趋势。另外对产出的生物质油用气质联用设备进行了成分分析,得出了生物质油的主要成分,其中酸类、酮类、脂类以及酚类的含量相对较高。     

导向喷动流化床颗粒物料抛高的估算

本文以气固两相流运动理论为基础，进行导向喷动流化床颗粒物料抛高估算，从而确定导向喷动流化床床高。计算结果与实验测定值吻合颇好。     

Numerical investigation of the reactive gas–solid characteristics in biomass fast pyrolysis of conical spouted reactor equipped with draft tube

Biomass fast pyrolysis is a promising technology to produce available char and high-value gas due to its green and sustainable ability. In the current work, the biomass fast pyrolysis in draft tube spouted bed has been numerically investigated via the multiphase particle-in-cell model. In this model, gas turbulence is calculated via large eddy simulation and particles are individually tracked in the Lagrangian manner. This model is successfully validated against experimental data. The particle-scale information of sand and biomass feedstock has been discussed, and the influence of draft tube configuration on the pyrolysis performance has been studied. The results show that the equipment of draft tube prevents gas leakage from spout to annulus, leading to large axial gas flux in the spout. Biomass particles in the spout and freeboard have high temperature and heat-transfer coefficient. Some biomass particles move along the outer wall of draft tube, indicating that the equipment of draft tube can avoid back-mixing by preventing direct contact of particles in the spout and annulus. Increasing the height of draft tube results in larger axial gas flux and higher sand heat-transfer coefficient, while decreases biomass temperature in the spout. The simulation results can offer valuable insights into comprehending intricate reactive gas–solid characteristics and conducting operation and design optimization of spouting apparatus.     

Fast Pyrolysis of Biomass in a Spout-fluidized Bed Reactor--Analysis of Composition and Combustion Characteristics of Liquid Product from Biomass

In order to gain insight into the fast pyrolysis mechanism of biomass and the relationship between bio-oil composition and pyrolysis reaction conditions, to assess the possibility for the raw bio-oil to be used as fuel, and to evaluate the concept of spout-fluidized bed reactor as the reactor for fast pyrolysis of biomass to prepare fuel oil, the composition and combustion characteristics of bio-oil prepared in a spout-fluidized bed reactor with a designed maximum capacity 5 kg/h of sawdust as feeding material, were investigated by GC-MS and thermogravimetry. 14 aromatic series chemicals were identified. The thermogravimetric analysis indicated that the bio-oil was liable to combustion, the combustion temperature increased with the heating rate, and only minute ash was generated when it burned. The kinetics of the combustion reaction was studied and the kinetic parameters were calculated by both Ozawa-Flynn-Wall and Popsecu methods. The results agree well with each other. The most probable combustion mechanism functions determined by Popescu method are f(a)=k(1-a)2 (400~406℃), f(a)=1/2k(1-a)3 (406~416℃) and f(a)=2k(1-a)3/2 (416~430℃) respectively.     

循环喷动二维流化床流动的特性研究

分析了循环喷动流化床中固体的循环机理 ,考察了固体循环速率随操作参数和物性参数的变化规律 ,给出可用于设计和操作的综合考虑几何参数、操作参数及物性参数对固体循环流动影响的固体循环速率的关联式及计算颗粒喷射高度的关联式     

Hydrodynamics of a Novel Biomass Autothermal Fast Pyrolysis Reactor: Flow Pattern and Pressure Drop

A novel biomass, autothermal, fast pyrolysis reactor with a draft tube and an internal dipleg dividing the reactor into two interconnected beds is proposed. This internally interconnected fluidized beds (IIFB) reactor is designed to produce high‐quality bio‐oil using catalysts. Meanwhile, the pyrolysis by‐products, i.e., char, coke and non‐condensable gases, are expected to burn in the combustion bed to provide the heat for the pyrolysis. On the other hand, the catalysts can be regenerated simultaneously. In this study, experiments on the hydrodynamics of a cold model IIFB reactor are reported. Geldart group B and D sand particles were used as the bed materials. The effects of spouting and fluidizing gas velocities, particle size, static bed height and the total pressure loss coefficient of the pyrolysis bed exit, on the flow patterns and pressure drops of the two interconnected beds are studied. Six distinct flow patterns, i.e., fixed bed (F), periodic spouted/bubbling bed (PS/B), spouted bed with aeration (SA), spout‐fluidized bed (SF), spout‐fluidized bed with slugging (SFS) and spouted bed with backward jet (SBJ) are identified. The investigations on the pressure drops of the two beds show that both of them are seen to increase at first (mainly in the F flow pattern), then to decrease (mainly in the PS/B and SA flow patterns) and finally to increase again (mainly in the SA and SF flow patterns), with the increase of the spouting gas velocity. It is observed that a larger particle size and lower static bed height lead to lower pressure drops of the two beds.     

农林废弃物的能源转化技术及研究进展

农林废弃物是放错地方的可再生清洁生物质资源;回收综合再利用是恢复资源的法宝;能源新技术是资源回收再利用的途径。以生物质中的农林废弃物为主,描述了农林废弃物转化生物质能的可行性和机理,分析、比较、总结了生物质能转化技术及其应用,特别是快速热解技术,并提出了生物质自混合下行循环流化床快速热解技术。     

Experiment and computational fluid dynamics investigation of biochar elutriation in fluidized bed

In fluidized bed biomass fast pyrolysis, the biomass is converted to biochar and elutriated. The elutriation rate is a key parameter in reactor designs and operations. This research presents a video-based continuous measurement of biochar elutriation rate in a fluidized bed with sands and biomass as bed materials. The fluidized bed is simulated with the computational fluid dynamics—coarse-grained discrete element method (CFD-CGDEM) in MFiX. The fluidization behavior of nonspherical sands can be more accurately captured when a rolling friction model is used. The predicted elutriation rate is close to the experimental measurement when the particle size distributions are considered and the filtered drag with a shape correction is used. These results validated the accuracy of the MFiX-based CFD framework for the prediction of biochar elutriations in the fluidized bed biomass fast pyrolysis reactor.     

Simulations of flow behavior of gas and particles in spouted bed with a porous draft tube

Flow behaviors of particles in a two-dimensional spouted bed with a porous draft plates are studied using a fluid dynamic computation with kinetic-frictional stresses models. Gas flow through the porous draft tube is simulated by Brinkman-Darcy-Forchheimer formulation. The distributions of concentration and velocities of particles are predicted. Simulated results predict the solid circulation rate and gas flux rate measured in the spouted bed with a porous draft tube (Ishikura et al., 2003). The solid circulation rate in the spouted bed with a porous draft tube is larger than that with a non-porous draft tube. The predicted bed pressure drop with the porous draft tube is high in comparison to the spouted bed with non-porous draft tube. The effect of the porosity of the porous draft tube on distributions of gas flux rate through the annulus and solid circulation rate are discussed.     

喷动流化床及其在煤加工方面的应用

论述了喷动流化床的主要技术进展,讨论了其主要流体动力学特性如喷动气流动形式、床层压降、固体循环速率、最小喷动气速和颗粒停留时间等以及喷动流化床在煤加工方面的应用如裂解、气化和燃烧等．指出了喷动流化床发展前景．     

Detailed CFD modelling of fast pyrolysis of different biomass types in fluidized bed reactors

In the present study, an Eulerian‐Eulerian computational fluid dynamics (CFD) model, combined with a comprehensive biomass reaction scheme, was used to simulate fast pyrolysis of four different biomass types in the fluidized bed reactors. The study focuses on the influence of biomass components of different biomass types on the yields, formations, and contents of compositions of pyrolysis products. The result showed that the bio‐oil yield of cellulose‐rich biomass was higher than other biomass types, and char was mainly produced by the fast pyrolysis of LIG‐C of biomass. Moreover, the contents of bio‐oil components were affected by the fast pyrolysis of biomass components. Further, the energy recovery coefficient (ERC) of bio‐oil obtained from pyrolysis of different biomass types was also calculated and analyzed in this paper.