间歇式给料的生物质快速热解制油的实验研究

设计了间歇式给料的鼓泡流化床反应器,对生物质在不同的反应温度、不同的流化气速以及不同的床层高度等条件下的生物质热解进行了研究。结果表明热解温度是生物质产油率的主要影响因素,流化气流速和床层高度对产油率也有一定的影响。在最佳的反应条件下,生物质油的产率可达65%,其主要组分为有机酸和呋喃。     

湿污泥颗粒的流化床干燥实验及模型

在鼓泡流化床内以河砂为干燥介质,对单颗粒湿污泥的流态化干燥特性进行实验研究,得到了流化床温度、污泥初始水分、污泥粒径及流化速度对干燥速率的影响规律：流化床温度及污泥粒径对干燥速率的影响都呈指数规律;污泥的水分越大,干燥速率越大;在鼓泡流化床流化速度达到2倍临界流化速度以上时,充分流化,流化速度再增大(2~5倍临界流化速度)对干燥速率没有明显影响. 在基本的扩散传质理论的基础上,利用实验数据回归得到湿污泥在鼓泡流化床内干燥的半经验模型,为流化床污泥干燥器的设计提供了基础数据和依据.     

稻壳的流态化燃烧实验

在高为6m,内径为φ0.3 m的冷态流化床装置上,以0～0.6 mm的河砂为床料,进行了高速循环流化床(CFB)和低速鼓泡床流化床(BFB)不同工况的冷态流态化实验研究,当流化风速达到2.8m/s时,流化床就能实现循环;鼓泡流化床压力分布主要集中在底部的密相区,循环流化床压力分布更趋均匀。以稻壳为原料,在相同尺寸的流化床热态装置上进行了流态化燃烧实验,稳定燃烧阶段,循环流化床和鼓泡流化床沿炉膛的温度分布情况较为类似,循环流化床燃烧效率达到93.36%,鼓泡流化床达到93.01%,循环流化床和鼓泡床燃烧排放烟气中烟尘、SO2、NOx的含量都能满足国家排放标准。     

三维单旋导向挡板鼓泡流化床内气固流动的CPFD模拟

单旋导向挡板是一种广泛应用于流化床反应器中的横向内构件,研究其对鼓泡流化床内气固流动的影响具有重要意义。采用计算颗粒流体力学(CPFD)方法耦合Igci曳力模型研究带有两层单旋导向挡板的鼓泡流化床内的三维气固流动,并与空筒鼓泡流化床作对比。首先将轴向和径向时均固含率分布的模拟结果和实验数据进行对比,验证了该计算方法的可靠性;随后考察了单旋导向挡板对鼓泡流化床内气泡平均当量直径沿床高的分布以及气体停留时间分布的影响,计算结果表明,单旋导向挡板对大气泡具有一定的破碎作用,在挡板影响区域内气泡平均当量直径变小。同时,有、无挡板流化床内的气体停留时间分布曲线与其数学特征基本一致,表明单旋导向挡板的存在对鼓泡流化床内的气体返混没有明显影响。     

锥形鼓泡流化床的研究进展

气固两相系统被广泛应用于石油、化工、制药等行业中,为了满足工业应用和环境保护,反应器的形式逐渐呈现多样化。锥形反应器由于截面积随高度变化,其表观气速在轴向上存在速度梯度,使其具有不同于等径流化床的独特的流化特性。本文从实验研究和模拟研究两个方面概述了锥形鼓泡流化床的研究现状及最新研究进展,总结分析了影响锥形鼓泡床的关键参数,并对锥形鼓泡流化床的研究方向进行了展望。     

新型旋涡流化床热风炉的研究

本文分析了现■尼厂中流化床热风炉的优缺点,提出了在鼓泡流化床热风炉悬浮空间加入适量的二次风的新型(?)涡流化床热风炉,它具有颗粒停留时间长、气固相对滑移速度大等特点,因此它能获得比鼓泡流化床热风炉更高的燃烧效率和更低的污染排放。     

废塑料裂解制取液体燃料的研究

对近年来废塑料的几种典型再生处理方法做了概括性的介绍,重点讨论了目前由废塑料裂解制取液体燃料的几种流程、存在的问题、已采取的相关措施.文章对废塑料裂解制取液体燃料的主要影响因素,如温度、压力、催化剂及其用量进行了较详细分析与讨论,提出了今后废塑料再生利用中的建议.     

有复杂反应的鼓泡流化床的数学模拟

以晕相流动模型为基础,建立了复杂反应A■→B→C鼓泡流化床反应器的数学模型。从各组分物料衡算出发,通过理论解析,发展了浓度分布、转化率和选择性的计算方法。以顺酐合成反应为例,利用实验研究结果和文献数据验证了模型的适应性。本模型能更好地与实验和中试数据吻合,因此可为复杂反应的鼓泡流化床反应器的设计、开发提供依据。     

鼓泡流化床内高灰煤气化过程的颗粒尺度特性研究

基于多相流体质点网格方法(MP-PIC)对高灰煤在三维鼓泡流化床气化过程进行了数值模拟研究。在欧拉-拉格朗日框架下将气相和固相分别视作连续介质和离散相处理。首先,将模拟得到的出口处气体组分结果与实验数据进行对比,实验数据与模拟结果具有良好的一致性。其次,研究了煤颗粒在气化炉内的温度、传热系数、速度和停留时间,从颗粒尺度揭示了鼓泡流化床气化炉内的颗粒分布特性和气固流动特征。结果表明:在气化炉入口附近煤颗粒与床层温差最大,传热系数最大;由于流化床内强非线性的气固流动,床中煤温度和传热系数的空间分布不均匀;煤颗粒和床料的瞬时速度具有稳定的波动幅度,其中垂直方向速度波动最明显,且煤颗粒的瞬时速度比床料的瞬时速度略大;由于颗粒间的剧烈碰撞,延长了煤颗粒停留时间。此外,对鼓泡流化床中煤气化过程颗粒尺度的研究,有助于深入了解固体颗粒的流动行为以及气固相相互作用特性,对鼓泡流化床反应器的设计优化具有重要意义。     

流化床焚烧技术的设计及污染物排放与防治

围绕流化床废物焚烧处理技术,对鼓泡式流化床、内旋流式流化床和循环流化床3种主要流化床焚烧炉的特点进行了介绍,并对废物和填料颗粒的性质、载气的性质和气速、温度和热平衡等参数对流化床焚烧技术设计过程的影响进行了探讨。最后,对流化床焚烧过程中主要污染物CO、HCl、SO_x、NO_x及二噁英类物质的产生机理进行了分析,总结了这些污染物的防治方法。     

Reduction of Devolatilization Rate of Fuel During Bubbling Fluidized Bed Combustion Using Porous Bed Material

Plastic waste combustion in bubbling fluidized bed combustors (BFBC) is characterized by the rapid devolatilization of the fuel. Noncombusted hydrocarbons are often formed, which have been reported to promote the formation of dioxins. In this work, porous bed material was employed instead of commonly used non‐porous sand to reduce the devolatilization rate. We measured (1) the heat transfer coefficient between an immersed object (brass sphere) and the bed and (2) the time required for the devolatilization of a plastic pellet after dropping it into the bed at 943 K. For porous particles we found a 30 % lower heat transfer coefficient, delayed onset of devolatilization and prolonged devolatilization time, compared with quartz sand. Therefore, porous particles were found to be effective in suppressing the rapid devolatilization of plastic waste.     

The continuous flash pyrolysis of biomass

A continuous atmospheric pressure flash pyrolysis process for the production of organic liquids from cellulosic biomass has been demonstrated at a scale of 1–3 kg/hr of dry feed. Organic liquid yields as high as 65–70% of the dry feed can be obtained from hardwood waste material, and 45–50% from wheat straw. The fluidized sand bed pyrolysis reactor operates on a unique principle so that char does not accumulate in the bed and treatment of the sand is not necessary. The product gas, about 15% of the yield, has a medium heating value. The liquid product is an acidic fluid, which pours easily and appears to be stable. A preliminary economic analysis suggests that if the pyrolysis oil can be used directly as a fuel, its production cost from wood waste is probably competitive with conventional fuel oil at the present time.     

Two-stage dual fluidized bed gasification: Its conception and application to biomass

The quoted two-stage dual fluidized bed gasification (T-DFBG) devises the use of a two-stage fluidized bed (TFB) to replace the single-stage bubbling fluidized bed gasifier involved in the normally encountered dual fluidized bed gasification (N-DFBG) systems. By feeding fuel into the lower stage of the TFB, this lower stage functions as a fuel gasifier similar to that in the N-DFBG so that the upper stage of the TFB works to upgrade the produced gas in the lower stage and meanwhile to suppress the possible elutriation of fuel particles fed into the freeboard of the lower-stage bed. The heat carrier particles (HCPs) circulated from the char combustor enter first the upper stage of the TFB to facilitate the gas upgrading reactions occurring therein, and the particles are in turn forwarded into the lower stage to provide endothermic heat for fuel pyrolysis and gasification reactions. Consequently, with T-DFBG it is hopeful to increase gasification efficiency and decrease tar content in the produced gas. This anticipation was corroborated through gasifying dry coffee grounds in two 5.0kg/h experimental setups configured according to the principles of T-DFBG and N-DFBG, respectively. In comparison with the N-DFBG case, the test according to T-DFBG increased, the fuel C conversion and cold gas efficiency by about 7% and decreased tar content in the produced gas by up to 25% under similar reaction conditions. Test results demonstrated also that all these upgrading effects via adopting T-DFBG were more pronounced when a Ca-based additive was blended into the fuel.     

Pyrolysis of scrap printed circuit board plastic particles in a fluidized bed

Pyrolysis behavior and corresponding pyrolysis products of printed circuit board plastic particles (PCBP particles) were investigated in a fluidized bed using TG-FTIR analysis system. PCBP particles were separated from crashed printed circuit boards using fluidized beds, 354 μm crashed plastic particles were pyrolyzed at the temperature ranging from 20 to 900 °C by a thermogravimetric analyzer. Two stages of decomposition were identified for PCBP particles under nitrogen conditions. The activation energy was 90.49 kJ/mol for the first-stage reaction and 137.80 kJ/mol for the second-stage reaction. Further, gas products, liquid products, and solid residues yielded in the fluidized bed were analyzed using an elemental analyzer and FTIR. It has been found that the liquid yields increased with an increase in pyrolysis temperature, and with an increase in superficial gas velocity. The main compositions of liquid products were aromatic compounds including substituted benzenes. Whereas, the solid products mainly contained char and fiberglass.     

Potential approaches to improve gasification of high water content biomass rich in cellulose in dual fluidized bed

Biomass containing water of 30-65 wt.% and rich in cellulose, such as various grounds of drinking materials and the lees of spirit and vinegar, is not suitable for biological digestion, and the thermal conversion approach has to be applied to its conversion into bioenergy. The authors have recently worked on converting such biomass into middle heating-value gas via dual fluidized bed gasification (DFBG) integrated with various process intensification technologies. This article is devoted to highlighting those technical ways, including the choice of the superior technical deployment for a DFBG system, the impregnation of Ca onto fuel in fuel drying, the integration of gas cleaning with fuel gasification via two-stage DFBG (T-DFBG), and the decoupling of fuel drying/pyrolysis and char gasification via the decoupled DFBG (D-DFBG). The attained results demonstrated that the superior deployment of bed combination for the DFBG should be a bubbling/turbulent fluidized bed gasifier integrated with a pneumatic riser combustor. In terms of improving efficiency of fuel conversion into combustible gas and suppressing tar generation during gasification, the impregnation of Ca onto fuel exhibited distinctively high upgrading effect, while both the T-DFBG and D-DFBG were also demonstrated to be effective to a certain degree.     

Modeling of fuel mixing in fluidized bed combustors

This paper presents a three-dimensional model for fuel mixing in fluidized bed combustors. The model accounts for mixing patterns which were experimentally shown to govern mixing in risers with geometry and operational conditions representative for furnaces in fluidized bed combustors. The mixing process is modeled for three different solid phases in the furnace and the model, which includes the return leg, can be applied both under bubbling and circulating regimes. The semi-empirical basis of the model was previously validated in different large-scale fluidized bed combustors and is combined with a model for fuel particle conversion to obtain the fuel concentration field. Model results are compared with experimental data from the Chalmers 12 MW_th CFB combustor, yielding a reasonable agreement.     

The influence of fast pyrolysis condition on biocrude-oil yield and homogeneity

The characteristics of biocrude-oil yield and quality have been investigated by changing fast pyrolysis condition for woody biomass. For the fast pyrolysis of woody biomass, a bubbling fluidized bed reactor having cylindrical shape was devised and a commonly used spiral quenching system was applied to the condensation of volatile gases from the reactor. Biomass feeding rate, nitrogen flow rate, pyrolysis temperature and particle size of woody biomass were changed to study the characteristics of volatile generation, its condensation and the homogeneity of the condensed biocrude-oil. In particular, the microscopic visualization of the collected biocrude-oil and its evaluation method by image processing technique were made for quantifying the homogeneity of the oil. From the results, the effects of heating and fluidization condition on the biocrude-oil yield and the homogeneity were fully scrutinized in a bubbling fluidized bed reactor. Also, the physical and chemical characteristics of the collected biocrude-oil were determined through various analysis techniques.     

串行流化床内气固流动控制

针对化学链燃烧分离CO₂技术特点,在一串行流化床（循环床+喷动床）冷态实验装置上,以CaSO₄载氧体为实验原料（d_p= 0.6 mm）,研究串行流化床气固流动特性。基于床内压力分布特征,提出将循环床（空气反应器）沿床高方向划分为鼓泡段和快速流化段2个流型区域,将喷动床（燃料反应器）沿床高方向划分为喷动段、鼓泡段和悬浮段3个流型区域,得出串行流化床内气固流动控制机理。研究并考察了循环床流化风速度、喷动床喷动风速度对串行流化床内反应器间（空气反应器和燃料反应器）气体串混、颗粒循环速率以及床层压降的影响。研究结果表明,流化风是床内颗粒循环的驱动力,流化风速度应控制在 3.77～4.05 m·s^-1;喷动风速度对床内颗粒循环以及系统稳定运行起着关键作用,建议将喷动风速度控制在0.42～0.56 m·s^-1。     

Upgrading of derived pyrolysis vapors for the production of biofuels from corncobs

A bubbling fluidized bed pyrolyzer was integrated with an in-situ honeycomb as a catalytic upgrading zone for the conversion of biomass to liquid fuels. In the upgrading zone, zeolite coated ceramic honeycomb (ZCCH) catalysts consisting of ZSM-5 (Si/Al=25) were stacked and N₂ or recycled non-condensable gas was used as a carrier gas. Ground corncob particles were fast pyrolyzed in the bubbling bed using fine sand particles as a heat carrier and the resulting pyrolysis vapors were passed on-line over the catalytic upgrading zone. The influence of carrier gas, temperature, and weight hourly space velocity (WHSV) of catalyst on the oil product properties, distribution and mass balance were studied. Using ZCCH effectively increased the hydrocarbon yield and the heating value of the dry oil, especially in the presence of the recycled noncondensable gas. Even a low usage of zeolite catalyst at WSHV of 180 h⁻¹ was effective in upgrading the pyrolysis oil and other light olefins. The highest hydrocarbon (≥C2) and liquid aromatics yields reached to 14.23 and 4.17 wt-%, respectively. The undesirable products including light oxygenates, furans dramatically decreased in the presence of the ZCCH catalyst.     

化工流化床技术在铀燃料循环工业中的应用

阐述了化工流化床技术在铀燃料循环工业各个过程中的具体应用,包括铀矿石浸析、铀化学转化、铀同位素富集、水堆燃料元件制备、高温气冷堆燃料元件制造、乏燃料后处理、铀燃料工业三废处理以及新型流化床核反应堆概念设计等过程。概述了各种应用流化床的类型和构造,结合具体应用过程评价了各种流化床的设计特性和优缺点,展望了流化床技术在铀燃料循环工业中的未来发展方向和广阔应用前景。指出必须结合我国核电快速发展的新趋势和新要求,加大针对铀燃料工业中的流化床应用技术研究,特别是气固流化床的基础研究工作。