Fluidized-Bed Bioreactor Applications for Biological Wastewater Treatment： A Review of Research and Developments

Wastewater treatment is a process that is vital to protecting both the environment and human health. At present, the most cost-effective way of treating wastewater is with biological treatment processes such as the activated sludge process, despite their long operating times. However, population increases have created a demand for more efficient means of wastewater treatment, Fluidization has been demonstrated to in- crease the efficiency of many processes in chemical and biochemical engineering, but it has not been widely used in large-scale wastewater treatment. At the University of Western Ontario, the circulating fluidized-bed bioreactor （CFBBR） was developed for treating wastewater. In this process, carrier particles develop a biofilm composed of bacteria and other microbes. The excellent mixing and mass transfer characteristics inherent to fluidization make this process very effective at treating both municipal and industrial wastewater. Studies of lab- and pilot-scale systems showed that the CFBBR can remove over 90% of the influent organic matter and 80% of the nitrogen, and produces less than one-third as much biological sludge as the activated sludge process. Due to its high efficiency, the CFBBR can also be used to treat wastewaters with high organic solid concentrations, which are more difficult to treat with conventional methods because they require longer residence times; the CFBBR can also be used to reduce the system size and footprint. In addition, it is much better at handling and recovering from dynamic loadings （i.e., varying influent volume and concentrations） than current systems. Overall, the CFBBR has been shown to be a very effective means of treating wastewa- ter, and to be capable of treating larger volumes of wastewater using a smaller reactor volume and a shorter residence time. In addition, its compact design holds potential for more geographically localized and isolat- ed wastewater treatment systems.

Mathematical Model and Advanced Control for Gas-phase Olefin Polymerization in Fluidized-bed Catalytic Reactors

In this study, the developments in modeling gas-phase catalyzed olefin polymerization fluidized-bed reactors （FBR） using Ziegler-Natta catalyst is presented. The modified mathematical model to account for mass and heat transfer between the solid particles and the surrounding gas in the emulsion phase is developed in this work to include site activation reaction. This model developed in the present study is subsequently compared with well-known models, namely, the bubble-growth, well-mixed and the constant bubble size models for porous and non porous catalyst. The results we obtained from the model was very close to the constant bubble size model, well-mixed model and bubble growth model at the beginning of the reaction but its overall behavior changed and is closer to the well-mixed model compared with the bubble growth model and constant bubble size model after half an hour of operation. Neural-network based predictive controller are implemented to control the system and compared with the conventional PID controller, giving acceptable results.

Experimental investigation of fluidized-bed reactor performance for oxidative coupling of methane

Performance of the oxidative coupling of methane in fluidized-bed reactor was experimentally investigated using Mn-Na2WO4/SiO2,La2O3/CaO and La2O3-SrO/CaO catalysts.These catalysts were found to be stable,especially Mn-Na2WO4/SiO2 catalyst.The effect of sodium content of this catalyst was analyzed and the challenge of catalyst agglomeration was addressed using proper catalyst composition of 2%Mn2.2%Na2WO4/SiO2.For other two catalysts,the effect of Lanthanum-Strontium content was analyzed and 10%La2O 3-20%SrO/CaO catalyst was found to provide higher ethylene yield than La2O3/CaO catalyst.Furthermore,the effect of operating parameters such as temperature and methane to oxygen ratio were also reviewed.The highest ethylene and ethane （C2） yield was achieved with the lowest methane to oxygen ratio around 2.40.5% selectivity to ethylene and ethane and 41% methane conversion were achieved over La2O3-SrO/CaO catalyst while over Mn-Na2WO4 /SiO2 catalyst,40% and 48% were recorded,respectively.Moreover,the consecutive effects of nitrogen dilution,ethylene to ethane production ratio and other performance indicators on the down-stream process units were qualitatively discussed and Mn-Na2WO4/SiO2 catalyst showed a better performance in the reactor and process scale analysis.

Simulation and Off-line Optimization of an Acrylonitrile Fluidized-bed Reactor Based on Artificial Neural Network

A mathematical model is developed for an industrial acrylonitrile fluidized-bed reactor based on arti-ficial neural networks. A new algorithm, which combines the characteristics of both genetic algorithm (GA) andgeneralized delta-rule (GDR) is used to train artificial neural network (ANN) in order to avoid search terminatedat a local optimal solution. For searching the global optimum, a new algorithm called SM-GA, incorporating ad-vantages of both simplex method (SM)and GA, is proposed and applied to optimize the operating conditions of anacrylonitrile fluidized-bed reactor in industry.

Reduction of Precursors of Chlorination By-products in Drinking Water Using Fluidized-bed Biofilm Reactor at Low Temperature

Objective To investigate the reduction of chlorination by-products （CBPs） precursors using the fluidized-bed biofdm reactor （FBBR）. Methods Reduction of total organic carbon （TOC）, ultraviolet absorbance （UV254）, tfihalomethane （THM） formation potential （THMFP）, haloacetic acid （HAA） formation potential （HAAFP）, and ammonia in FBBR were evaluated in detail. Results The reduction of TOC or UV254 was low, on average 12.6% and 4.7%, respectively, while the reduction of THMFP and HAAFP was significant. The reduction of ammonia was 30%-40% even below 3℃, however, it could quickly rise to over 50% above 3℃. Conclusions The FBBR effectively reduces CBPs and ammonia in drinking water even at low temperature and seems to be a very promising and competitive drinking water reactor for polluted surface source waters, especially in China.

Production of hydrogen and syngas via pyrolysis of bagasse in a dual bed reactor

Pyrolysis of bagasse followed by thermal cracking of tar was carded out at atmospheric pressure using a dual bed reactor. The first bed was used for the pyrolysis and the second bed was used for thermal cracking of tar. Iron fillings were used as the packed bed material in the second bed. The effects of reaction time （20 to 40 rain）, reactor temperature （600 to 900 ℃） and packed bed height （40-100 mm） on the product （char, tar and gas） yield and gas （H2, CO, CO2, CH4, CnHm） composition were studied. Over the ranges of the experimental conditions used, the operating conditions were optimized for pyrolysis temperature around 850 ℃, a reaction time of 30 min and packed bed height of 100 mm, thus we could obtain a gas richer in hydrogen and carbon monoxide and poorer in carbon dioxide and hydrocarbons. It was observed that compared with single bed process, dual bed process increased the gas yield from 0.397 to 0.750 m3/kg and decreased the tar yield from 0.445 to 0.268 g/g while the heating value of the product gas remained almost constant （10-11 M J/m3）.

Particle/metal-based monolithic catalysts dual-bed reactor with beds-interspace supplementary oxygen:Construction and performance for oxidative coupling of methane

A novel particle/metal-based monolithic catalysts dual-bed reactor with beds-interspace supplementary oxygen is constructed comprising of the upper-layer 5 wt%Na2WO4-2 wt%Mn/SiO2 particle catalyst and the under-layer 3 wt%Ce-5 wt%Na2WO4-2 wt%Mn/SBA-15/Al2O3/FeCrA1 metal-based monolithic catalyst as well as a side tube in the interspaces of two layers for supplementing 02. The reaction performance of oxidative coupling of methane （OCM） in the dual-bed reactor system is evaluated. The effects of the reaction parameters such as feed CH4/O2 ratio, reaction temperature and side tube feed 02 flowrate on the catalytic performance are investigated. The results indicate that the suggested mode of dual-bed reactor exhibits an excellent performance for OCM. CH4 conversion of 33.2%, C2H4 selectivity of 46.5% and C2 yield of 22.5% could be obtained, which have been increased by 6.4%, 4.1% and 5.5%, respectively, as compared with 5 wt%Na2WO4-2 wt%Mn/SiO2 particle catalyst in a single-bed reactor and increased by 10.7%, 31.9% and 17.7%, respectively, as compared with 3 wt%Ce-5 wt%Na2WO4-2 wt%Mn/SBA-15/Al2O3/FeCrA1 metal-based monolithic catalyst in a single-bed reactor. The effective promotion of OCM performance in the reactor would supply a valuable reference for the industrialization of OCM process.

Oxidative coupling of methane in a dual-bed reactor comprising of particle/cordierite monolithic catalysts

A dual-bed reactor was constructed comprising of a 5%Na2WO4-2%Mn/SiO2 particle catalyst and a 4%Ce-5%Na2WO4-2%Mn/SiO2 /cordierite monolithic catalyst.The reaction performance of the oxidative coupling of methane （OCM） over the dual-bed reactor system was evaluated.The effects of the bed height and operation mode,as well as the reaction parameters such as reaction temperature,CH4/O2 ratio and flowrate of feed gas,on the catalytic performance were investigated.The results indicated that the suggested dual-bed reactor exhibited a good performance for the OCM reaction when the feed gases firstly passed through the particle catalyst bed and then to the monolithic catalyst bed.A CH4 conversion of 38.2% and a C2H4 selectivity of 43.3% could be obtained using the dual-bed reactor with a particle catalyst bed height of 10 mm and a monolithic catalyst bed height of 50 mm.Both the CH4 conversion and C2H4 selectivity have increased by 2.5% and 12.8%,respectively,as compared with the 5%Na2WO4-2%Mn/SiO2 particle catalyst in a conventional single-bed reactor and by 12.9% and 23.0%,respectively,as compared with the 4%Ce-5%Na2WO4-2%Mn/SiO2 /cordierite monolithic catalyst in a single-bed reactor.The catalytic performance of the OCM in the dual-bed reactor system has been improved remarkably.

双面冷却熔盐堆组件热工分析程序开发与验证

新型液态燃料熔盐堆双面冷却组件相比传统熔盐堆组件具有更大的换热面积和更短的石墨导热距离,因而具有更低的石墨温度热点,然而由于其不同的几何结构特征和熔盐自发热特性,组件内存在独特的热量分配和冷却剂流量分配的问题。为准确高效评估新型组件的热安全边界,有必要开发新的计算分析工具。本研究基于MATLAB开发了适用于熔盐堆双面冷却组件的一维稳态热工分析程序THDA-MSR(Thermal-Hydraulic Analysis Code for Dual Cooled Assembly-Molten Salt Reactor),考虑熔盐自发热的特点,建立了组件内外流道内熔盐的一维温度分布模型和熔盐石墨对流换热模型以及石墨导热模型,根据并联通道压损相等原则建立流量分配模型,通过CFD(Computational Fluid Dynamics)数值模拟对程序计算结果进行了验证,并初步分析了各结构参数对组件最大熔盐出口温度和石墨温度热点的影响。THDA-MSR的计算结果与CFD结果吻合较好,压损偏差小于4.84%,石墨温度热点偏差小于0.15%,分析结果发现:外通道截面积占总流道截面积比是影响最大熔盐出口温度和石墨温度热点的关键参数。以上研究结果表明,自编程序能很好地预测组件流量分布、组件压损、熔盐温度分布和石墨温度热点。THDA-MSR能够应用于熔盐堆双面冷却组件热工水力性能分析评估,对于组件选型设计有较大工程参考价值。

小型反应堆与煤电机组融合发展面临的问题研究

为应对日益严重的气候变化问题,低碳化、清洁化已成为全球能源发展的主基调,其中电力系统的脱碳是全社会实现零碳发展的重要一环。核能是安全、低碳、清洁、高能量密度的战略能源,对优化能源结构、减少温室气体排放发挥着重要作用。小型反应堆作为核能利用的前沿领域,在提升安全性的同时,也具有较高的经济性。根据煤电机组现状和未来小堆发展特点,本研究提出四种不同类型的融合发展模式。结果表明,小型堆与煤电机组的融合发展,不仅可以提高社会用能效率、降低碳排放强度,而且能提升新型电力系统下用能的安全性和可靠性。提高小型堆技术本质安全性、解决公众心理安全问题、降低小型堆单位造价、拓宽小型堆与煤电机组应用范围,有利于解决小型堆发展难题,推动小型堆与煤电机组融合发展。

生物质双流化床气固流动特性研究与数值模拟

依靠双流化床冷态装置考察流化风和松动风的流量对流化床流化形式、返料器料封高度以及固体循环量的影响。当流化风流量为5 m3/h时,流化床气化器内颗粒呈鼓泡流化。返料器料位与返料器两侧压差有关,压差越大,返料器内料封高度越低。气体反窜时返料器两侧压差变小,料位逐渐升高。不改变其他条件,在下松动风流量为3 m^(3)/h及以下时,增大松动风流量,颗粒循环量逐渐增加,一定条件下固体颗粒循环量达到最大为6.72 kg/h。对装置进行数值模拟,结果显示颗粒的流化形式与实验一致。

Temperature fault-tolerant control system of CSTR with coil and jacket heat exchanger based on dual control and fault diagnosis

For the characteristics of the continuous stirred-tank reactor(CSTR) with coil and jacket cooling system,a CSTR temperature dual control solution based on the analysis of the CSTR exothermic reaction control characteristic was proposed for an organic material polymerization production.The control solution has passive fault-tolerant ability for the jacket cooling water cutting off fault and active fault-tolerant potential for the coil cooling water cutting off fault,and it has good control ability,high saving energy and reducing consumption performance.Fault detection and diagnosis and fault-tolerant control strategy are designed for the coil cooling fault to achieve the active fault-tolerant control function.The CSTR temperature dual control,process fault detection and diagnosis and active fault-tolerant control were full integrated into the CSTR temperature fault-tolerant control system,which achieve fault tolerance control of CSTR temperature for any severe malfunction of jacket cooling or coil cooling cutting off,and the security for CSTR exothermic reaction is improved.Finally,the effectiveness of this system was validated by semi-physical simulation experiment.

双模式热管堆电热原理样机设计及验证实验研究

固态热管反应堆是未来新型装备最佳能源动力解决方案之一,然而其关键技术尚未成熟,可行性及可靠性有待近一步研究。本文提出了动静结合双模式热管堆概念设计,搭建了“模拟堆芯-高温热管-斯特林-温差发电”一体化集成实验装置,利用紫铜基体及加热棒模拟反应堆堆芯,利用弯折高温钾热管实现堆芯冷却及能量传输过程,利用斯特林热电转换装置及碲化铋温差发电元件实现动态/静态热电转换过程,验证了双模式热管堆技术的可行性。实验结果表明,所研制的弯折高温钾热管符合设计需求,输入功率为878 W时,热管轴向壁面温差低于60 K,不凝气体段长度小于5 cm。对于碲化铋温差发电器件,输入功率为4.2 kW、热端温度为310℃、冷端温度为20℃时,30片热电器件共发电102.6 W,热电转换效率为2.44%。对于斯特林发电机,输入功率为3.3 kW时,发电功率为429 W,热电转换效率为13.1%。本文结果可为双模式热管堆概念设计及研制提供实验数据支撑。

双模式热管堆非核原理样机热力特性数值分析

小型热管反应堆电源技术具有续航久、结构紧凑、环境适应性强、固有安全性高等优势,可以适配于多种领域。本文以双模式热管堆非核原理样机NUSTER2.0为对象,在COMSOL中建立高温热管、温差发电装置及斯特林装置理论模型并耦合形成系统模型,对样机运行特性及力学特性进行数值仿真研究。15 kW加热功率稳态工况下,仿真结果与实验结果的热管温度分布及动、静态模块主要运行参数均吻合良好,最大相对误差为6.73%,初步验证了模型可靠性。变功率仿真结果确定了斯特林撞杆阈值为16.5 kW,并预估静态模块在25 kW附近达到效率峰值。系统启动瞬态仿真得到了“3-5-10-15 kW”阶梯式功率平台下的样机启动特性,并提出了样机启动策略。系统热力耦合稳态工况确定了样机应力危险区,并求得15 kW工况中堆芯热膨胀率为1.21%,热管-堆芯基体和热管-集热基体耦合处的最大应力分别为160 MPa和97 MPa。本文为NUSTER2.0样机的特性研究和实验设计提供了数值分析基础。

双提升管催化裂解技术研究进展

综述了国内外双提升管催化裂解工艺技术进展,包括国内灵活多效催化裂解(FDFCC)系列技术、增强型催化裂解技术(DCC-plus)、两段提升管催化裂解多产丙烯技术(TMP)及国外Maxofin-FCC工艺、PetroRiser工艺及PetroFCC工艺。重点介绍了旨在解决催化剂与原料油精确匹配问题的双催化剂分区再生工艺技术,并指出今后的研发应注重:优化双提升管催化裂解分区再生装置的工艺参数,以降低操作难度;根据市场需求,实现不同技术方案在同一装置上的灵活切换,以加快工业化进程。

浆态床合成气制二甲醚双功能催化剂的性能

在浆态床合成气制二甲醚过程中，在２８０℃、４ＭＰａ、尾气流量４５００ｍＬ／ｇｃａｔ·ｈ条件下，考察了甲醇合成和甲醇脱水催化剂组成的双功能催化剂对合成的影响。随二者质量比的增加，合成气的转化率、二甲醚生成速率逐渐增加，在催化剂比例４～７时达最高值后降低。随催化剂比例的增加，二甲醚、烷烃的选择性逐渐降低，甲醇选择性逐渐升高。当催化剂比例为４～５时二甲醚生成速率最高达１５～１６ｍｍｏｌ／ｇｃａｔ·ｈ，甲醇当量生成速率接近最高值≈３９ｍｍｏｌ／ｇｃａｔ·ｈ，二甲醚选择性≈７５％，烃类选择性５％以下，为合成气制二甲醚最适宜催化剂比例。

用于研究大气氧化过程和机制的双反应器烟雾箱的评估和应用（英文）

设计并搭建了一个新的双反应器烟雾箱,用于研究可生成臭氧或二次有机气溶胶(SOAs)的大气氧化过程.该烟雾箱包括一个绝热的箱体及其内部两个体积为5 m3的氟化乙丙烯(FEP)薄膜反应器,箱内的温度可以精确控制在-10到40°C之间.利用该烟雾箱研究了光源对丙烯气相氧化机理的影响,发现相对于传统的黑光灯光源,采用的多重光源所得到的结果可以与模型更好地匹配.进行了丙烯和间二甲苯的光氧化的初步实验,发现该烟雾箱可用于模拟可产生臭氧或SOAs的气相氧化过程,并可以通过不同初始浓度的对比实验找寻不同物种对反应过程的影响.间二甲苯在不同NOx条件下光氧化得到的SOA产率与之前的研究比较符合,这表明该烟雾箱可以实现气-粒转化过程的模拟.双反应器可以实现在一个关键条件的存在区别,而其他条件完全一致的情况下的对比实验,从而帮助我们进一步理解在大气复合污染过程中起关键作用的因素.

降低催化裂化汽油烯烃技术——FDFCC工艺

根据催化裂化过程中烯烃转化机理,提出了一种并联双提升管催化裂化反应体系--FDFCC工艺,其中一根提升管用于重油裂化,另一根用于汽油改质.工业实施结果表明,该工艺可以显著降低催化裂化汽油的烯烃含量,烯烃体积分数降低20～30个百分点,硫含量下降15%～20%,改质汽油诱导期增加,MON和RON略有增加,芳烃中苯含量基本维持不变,芳烃含量虽有所提高,但远远小于规定指标.与常规FCC工艺相比,FDFCC工艺的汽油产率下降4～5个百分点,液化气和柴油产率均增加2个百分点左右,(焦炭+干气)产率增加小于1个百分点.

聚变驱动次临界堆双冷嬗变包层热工水力学参数设计与分析

聚变驱动次临界堆双冷嬗变包层是一个以氦气和液态金属LiPb为冷却剂,以嬗变核废料为主要目的的多功能包层。依据功率平衡模型对不同工况优化的基础上,对该包层热工系统参数进行了设计分析。采用三维商用计算流体力学程序对第一壁和高功率密度区中液态LiPb的流场进行数值模拟计算,给出了优化的典型热工水力参数。