Numerical simulation of flow hydrodynamics of struvite pellets in a liquid–solid fluidized bed

Phosphorus recovery in the form of struvite has been aroused in recent decades for its dual advantages in eutrophication control and resource protection.The usage of the struvite products is normally determined by the size which is largely depended on the hydrodynamics.In this study,flow behavior of struvite pellets was simulated by means of Eulerian–Eulerian two-fluid model combining with kinetic theory of granular flow in a liquid–solid fluidized bed reactor(FBR).A parametric study including the mesh size,time step,discretization strategy,turbulent model and drag model was first developed,followed by the evaluations of crucial operational conditions,particle characteristics and reactor shapes.The results showed that a cold model with the mesh resolution of 16 × 240,default time step of 0.001 sec and first order discretization scheme was accurate enough to describe the fluidization.The struvite holdup profile using Syamlal–O'Brien drag model was best fitted to the experimental data as compared with other drag models and the empirical Richardson–Zaki equation.Regarding the model evaluation,it showed that liquid velocity and particle size played important roles on both solid holdups and velocities.The reactor diameter only influenced the solid velocity while the static bed height almost took no effect.These results are direct and can be applied to guide the operation and process control of the struvite fluidization.Moreover,the model parameters can also be used as the basic settings in further crystallization simulations.     

盐度对EGSB反应器的运行及厌氧颗粒污泥的影响

高盐废水通常含有高COD浓度,难以处理,引用具有耐盐性能的生物反应器处理高盐废水成为必要.使用模拟高盐废水在3.267 kg·(m~3·d)~(-1)的COD容积负荷下,将Cl~-浓度逐步从0提升至10 000 mg·L~(-1),研究盐度对膨胀颗粒污泥床(expanded granular sludge bed,EGSB)反应器的影响.结果表明,Cl~-浓度小于7 500 mg·L~(-1)时,对微生物的抑制作用较低;Cl~-浓度为7 500 mg·L~(-1)时,反应器的COD去除率能保持在98.1%左右,容积产气率能够基本保持在1.3 m~3·(m~3·d)~(-1)以上,大粒径的厌氧颗粒污泥仍然占据体系的主体;当Cl~-浓度为10 000 mg·L~(-1)时,反应器中的厌氧颗粒污泥受到严重影响.采用高通量测序技术对0和5 000 mg·L~(-1)两个Cl~-浓度下的厌氧颗粒污泥的微生物菌群结构进行分析,结果表明,盐度影响了微生物的种群分布,在5 000 mg·L~(-1)的Cl~-浓度下,主要的优势菌属由Cl~-浓度为0时的Methanoregula与Longilinea变为Methanobacterium、Methanospirillum、Methanothrix和Paludibacter.     

A review on numerous modeling approaches for effective, economical and ecological treatment wetlands

Constructed wetlands (CWs) for wastewater treatment have evolved substantially over the last decades and have been recognized as an effective means of "green technology" for wastewater treatment. This paper reviews the numerous modeling approaches ranging from simple first-order models to more complex dynamic models of treatment behaviour in CWs. The main objective of the modeling work is to better understand the process in CWs and optimize design criteria. A brief study in this review discusses the efforts taken to describe the process-based model for the efficient removal of pollutants in CWs. Obtaining better insights is essential to understand the hydraulic and biochemical processes in CWs. Currently, employed modeling approaches can be seen in two categories, i.e. "black-box models" and "process-based models". It is evident that future development in wetland technology will depend on improved scientific knowledge of internal treatment mechanisms.     

影响循环流化床锅炉石灰石脱硫效率的因素分析

循环流化床锅炉不仅燃烧效率高、燃料适应性广、负荷调节性能好;而且脱硫效率高、运行成本低、设施简单可靠,近年来得到了快速发展.本文研究了循环流化床炉内脱硫机理,分析了影响脱硫效率的主要因素,对提高循环流化床脱硫效率和石灰石利用率,减少锅炉烟气二氧化硫排放浓度,降低脱硫剂的消耗量具有指导意义,在流化床脱硫系统设计、优化运行...     

循环流化床锅炉在森工林区供热行业的应用前景

针对目前森工林区供热行业使用传统燃煤锅炉现状,分析对比层燃锅炉与循环流化床锅炉的优缺点,分析森工林区供热行业应用循环流化床锅炉的前景。     

Cd~(2+) removal from wastewater by sulfate reducing bacteria with an anaerobic fluidized bed reactor

Ｃｄ２＋ｒｅｍｏｖａｌｆｒｏｍｗａｓｔｅｗａｔｅｒｂｙｓｕｌｆａｔｅｒｅｄｕｃｉｎｇｂａｃｔｅｒｉａｗｉｔｈａｎａｎａｅｒｏｂｉｃｆｌｕｉｄｉｚｅｄｂｅｄｒｅａｃｔｏｒＭａＸｉａｏｈａｎｇ，ＨｕａＹａｏｘｉ，ＪｉａｎｇＦｅｎｇＩｎｓｔｉｔｕｔｅｏｆＭ...     

有机废水处理中复极固定床电解槽的研究进展

在分析中 ,结合了近年来关于三维电极等应用技术以及复极固定床电解槽 (BPBC)水处理技术的研究文献 ,概括了BPBC的特点、基本原理以及有机废水处理的应用现状 ,并提出了目前复极固定床电解槽的研究中存在的问题及今后的研究发展方向     

发酵床垫料中微生物16S rDNA PCR反应条件的建立与优化

为探讨发酵床垫料中微生物16S rDNA基因扩增实验中诸多因素对实验结果的影响,采用单因素法对16S rDNA基因扩增时PCR反应体系中的5个潜在因素（Mg^2＋、dNTP、引物、Taq酶、模板DNA）5水平上进行优化实验,并进一步优化了反应程序中的退火温度、循环次数。结果表明：25μL的最佳反应体系为：10×PCR buffer 2.5μL、MgCl22.0 mmol·L^-1、dNTP 0.2 mmol·L^-1、引物0.2μmol·L^-1、Taq DNA聚合酶0.5 U、模板DNA 50 ng;最佳反应程序为：在94℃下进行4 min预变性;随后循环扩增25个循环（包括94℃变性45 s,53.7℃退火30 s,72℃延伸90 s）;最后在72℃下延伸10 min。     

新排放标准下烧结烟气脱硫工艺的选择

结合国内钢铁行业烟气脱硫治理的现状,针对《钢铁烧结、球团工业大气污染物排放标准》(GB28662-2012)的实施,论述了LJS烟气循环流化床多组分污染物协同净化工艺是一种适合新排放标准的可靠工艺。     

MBBR工艺中SNEDPR的启动及性能研究

为探究同步硝化内源反硝化除磷(SNEDPR)强化移动床生物膜反应器(MBBR)工艺脱氮除磷的可行性,采用连续曝气和搅拌/曝气交替运行的MBBR反应器,以磁性填料作为载体处理模拟生活污水,考察了SNEDPR启动过程中的脱氮除磷性能,并结合荧光显微镜和高通量测序技术对各个功能菌群结构变化情况进行了分析.结果表明,经两阶段运行后,氨氮和磷去除率分别达到97.6%和85.37%,出水NO₂^-—N、NO₃^-—N和COD浓度分别为1.3949,3.88和20.4mg/L,同步硝化内源反硝化率(SNEDR)由0.07%逐渐升高至86.35%.好氧阶段同步硝化内源反硝化率的提高,使出水NO_x^-—N浓度下降,提高了系统的脱氮性能和厌氧阶段内碳源的储存量.荧光显微镜和高通量测序结果表明,经过53d的运行,微生物群落多样性呈显著提高,系统内GAOs、AOB、NOB丰度的提高(分别由接种污泥中的3.3%、0.84%和0.66%提高至系统内的27.08%/20.48%、1.45%/1.76%和1.05%/0.85%)和PAOs、DPAOs的存在,保证了系统的脱氮除磷性能,在MBBR工艺中实现了EBPR与SNED的耦合.