FENTON流体化床与曝气生物滤池联合在造纸废水提标改造中的应用研究

本文对四川德阳某造纸厂造纸废水深度处理扩容及提标改造项目工程案例进行了论述,选用FENTON流体化床与曝气生物滤池联合的主体处理工艺对造纸废水进行深度处理提标改造,废水从《制浆造纸工业水污染物排放标准》GB3544-2008表2造纸企业排放标准提升至《四川省岷江、沱江流域水污染物排放标准》DB51/2311-2016表1“工业园区集中式污水处理厂”排放限值。本工艺具有较高的难降解污染物去除效率,较强的抗冲击负荷能力,以及相对稳定的出水水质,具备良好的应用价值,同时具有较低的运行费用。

流体化床Fenton深度处理合成制药废水研究

采用流体化床Fenton装置深度处理合成制药废水,通过正交试验确定了处理合成制药废水的最佳条件是HRT为20min,初始pH值为4.0,H2O2/CODcr(质量比)为4.0,H2O2/Fe2+(摩尔比)为15,且在最佳条件下出水CODcr稳定在80mg/L以下,可以达到《污水综合排放标准》(GB8979-1996)一级标准。同时将其与标准Fenton氧化法进行对比试验,结果显示流体化床FentonCODcr去除率可提高13%以上,污泥产生量可降低70%,运行成本可减低28%,稳定运行成本可以控制在3.0元/吨废水以内。

Fenton流体化床工艺处理腈纶污水的研究

采用流体化床Fenton法与生物接触氧化法相结合的工艺处理腈纶污水。根据水质特点,制定加药量、回流比及水力停留时间,运行效果明显。在保证供水COD稳定在300mg/L左右,适当增加污水处理成本的情况下,出水COD全部控制在100mg/L之内。

厌氧脱硝流体化床技术处理硝态氮废水研究

开发研制了ADFB厌氧脱硝流体化床,分别研究了用甲醇及高浓度有机废水作为碳源的情况下该流体化床对废水中的硝态氮及COD去除效果。结果表明,ADFB厌氧脱硝流体化床在运行稳定的情况下,对废水中的硝态氮及COD去除率分别可达到95%和85%以上。

电解还原Fenton法及流体化床Fenton法介绍及应用

目前有很多产业的废水处理须增设高级废水处理单元才能达到排放标准,至今已发展的高级废水处理技术包括臭氧氧化法、活性碳吸附法、薄膜分离法、湿式氧化法及Fenton氧化法等,其中以Fenton氧化法(H2O2/Fe2+)被认为是一种最有效、简单且经济的方法,其他方法则因初设成本或操作成本太高而较难被业者接受。Fenton家族高级处理技术的演进,由传统Fenton法、电解氧化-Fenton法(简称FentonⅡ)、电解还原-Fenton法(简称FentonⅢ)、至流体化床-Fenton法(简称FentonⅣ)。本文重点介绍了FentonⅢ及FentonⅣ这两类目前高浓度与低浓度废水的重点低污泥处理技术。

以制糖滤泥吸收二氧化硫之流体化床数学模拟

以修正二相数学模式来描述以制糖滤泥及添加剂吸收二氧化硫之流体化床。我们对床中之气体及固体进行质量均衡，结果设立了联立的常微分方程式并以数值方法解之。如此可解得不同时间时气体和固体的浓度分布和气泡相及乳化相中的转化率。最后可算出床的脱硫效率。计算结果显示当反应温度、床直径或床高增加时，脱硫效率增加。当气体流速或进口二氧化硫浓度降低时，脱硫效率亦会增加。粒子大小对脱硫效率的影响很小。

陶瓷装置可增加流体化床从铝熔炼炉中回收废热

根据美国能源部工业计划局的统计,安装在纽约马塞纳阿尔考公司铝熔炼炉上的第一个美国工业流体化床废热回收装置,从被冷却到593℃的废烟气中产生了将近11793.4吨可用作能源的蒸汽。该装置的关键部件是一个浅的流体化床,在流体化床里细小的氧化铝颗粒提高了炉子烟道排气对翅片管蒸汽发生器的热传递效率。经过完整的试验周期和一年的测定,现在已确认另外的使用性能得到了提高,即,

COD深度处理——Fenton流体化床高级氧化处理技术

Fenton以其独特的优越性在COD废水,尤其是高浓度有机废水上达到新的处理效果,具有广阔前景,本文介绍了Fenton流体化床高级氧化处理技术的原理、技术特点以及应用流程。

循环流化床锅炉自控技术的应用

介绍了国内循环流化床锅炉的应用现状,总结了影响锅炉自动控制的相关问题,在进一步分析循环流化床锅炉燃烧原理和存在问题的基础上,对如何实现锅炉自动控制以获得更好的燃烧效果提出了建议。

Heat Transfer Between Immersed Horizontal Tubes and Aerated Vibrated Fluidized Beds

Heat transfer coefficients between an immersed horizontal tube and an aerated vibrated fluidized bed are measured. There is a maximum value in the h-P experimental curve. The heat transfer coefficient increases with decreases in particle diameter in the fully fluidized region. The particle density has less effect on the heat transfer coefficients. High amplitude and low frequency, or low amplitude and high frequency are favorable to heat transfer. Exceedingly high gas velocity is unfavorable to the surface-bed heat transfer. A model based on the 'pocket' theory was proposed for predicting the surface-to-bed heat transfer coefficients in fully fluidized region. The predictions from the model were compared with observed data. The reasonable fit suggests the adequacy of the model.

Simulation of the Clustering Phenomenon in a Fast Fluidized Bed: The Importance of Drag Correlation

Drag force is a key parameter in the numerical modeling of gas-particle flow in circulating fluidized beds. The reliability of current drag force correlations over the regime of fast fluidization has, however, not been thoroughly investigated. In this article, a drag force correlation accounting for the clustering effects for Geldart A particles is used to simulate the behaviors typical of fast fluidization, including dynamic evolution of clusters as well as time- averaged axial and lateral voidage profiles. Diverse images of clusters are captured and the time-averaged profiles of voidage are shown to be in quantitative agreement with the present empirical correlation. The results based on different constitutive correlations of drag force show the importance of the choice of drag force in modeling fast-fluidized beds. This drag force correlation, based on a simple averaging assumption, could give some basic insights about the magnitude of the drag reduction.

Horizontal gas mixing in rectangular fluidized bed:A novel method for gas dispersion coefficients in various conditions and distributor designs

In a rectangular fluidized bed combustor, the tracer gas is injected continuously into the bed from a point source at the center of the distributor plate. In this study, a general governing equation is formulated for tracer gas dispersion in the bed. An analytical solution is derived to estimate the dispersion coefficients, Dxand Dy, in a horizontal plane. The concentration profiles at different sampling heights with various gas velocities are plotted.Subsequently, to estimate the dispersion coefficients, surface fitting of the obtained analytical solution to the experimental data is performed. The dispersion coefficients obtained from this model are compared with those of a conventional model. Additionally, the effect of walls, bed height and gas injection rate on the dispersion coefficients in a horizontal plane is investigated, and the effect of distributor design on the dispersion coefficients in a horizontal plane is investigated with different tracer positions. It is found that Dxand Dyare nearly equivalent at a lower tracer gas ratio of the injected gas to the total gas flow rate. It is also demonstrated that the effect of bed height on Dxis minor. This model is also able to estimate the dispersion coefficients in the case of a multihorizontal nozzle distributor.

Preparation of solid medium for use in separation with gas-solid fluidized beds

The highly-efficient dry separation technique using a gas-solid fluidized bed is very beneficial for increasing coal grade and optimizing the utilization of coal resources.The size distribution of the solid medium(e.g.,magnetite powder) used in this technique is one of key factors that influences fluidization and separation performance.It is,therefore,urgent to prepare medium in a way that operates at low cost and high efficiency.Grinding experiments were performed using a planetary ball mill equipped with a frequency converter.The effect of fed mass,rotation frequency of the mill,grinding time and the ball-size ratio on grinding performance was investigated.The grinding parameters were optimized by numerical calculations using Artificial Neural Network(ANN) in Matlab.A regression equation for predicting the yield of the desired product(i.e.,0.3～0.15 mm magnetite powder) is proposed.The maximum yield of 0.3～0.15 mm particles was 47.24%.This lays a foundation for the industrial-scale production of the solid medium required for separation with a magnetite-powder fluidized bed.

Pseudo-Fluid Simulation of Transient Behaviors in a CFB Riser

The kinetic theory of granular flow (KTGF) is modified to fit the Einstein′s equation for effective viscosity of dilute flow. A pseudo-fluid approach based on this modified KTGF is used to simulate the dynamic formation and dissipation of clusters in a circulating fluidized bed riser. The agglomeration of particles reduces slip velocity within particle clusters, and hence results in two reverse trends: discrete particles are lifted by air while particle clusters fall down along the wall. The dynamic equilibrium of these two types of motion leads to the characteristic sigmoid profile of solid concentration along the longitudinal direction. The predicted solid velocity, lateral and longitudinal profiles of solid volume fraction and annulus thickness are in reasonable agreement with experimental results.

Multi-scale Analysis of Chaotic Characteristics in a Gas-Solid Fluidized Bed

Deterministic chaos theory offers useful quantitative tools tocharacterize the non-linear dynamic be- havior of a fluidized bed andthe developed complexity theory presents a new approach to evaluatefinite sequences. In this paper, the non-linear, hydrodynamicbehavior of the pressure fluctuation signals in a reactor wasdiscussed By chaos parameters and complexity measures. Coherentresults were achieved by our multi-scale analysis, which Furtherexposed the behavior in a gas-solid two-phase system.

Hydrodynamics and Lateral Gas Dispersion in a High-Density Circulating Fluidized Bed Reactor with Bluff Internals

Effect of bluff internals on the hydrodynamics and lateral gas mixing was studied in a 0.186m ID high-density riser. With the bluff internals, the extremely non-uniform radial profiles of solid fraction and particle velocity become flat and the dense downflow layer near the wall disappears, indicating the significant enhancement of solid turbulence introduced by the internals. The fluctuation velocity and solid fraction transient signal analysis indicates a significant increase in fluctuation intensity near the wall region. The length influenced by the internals on the flow structure is about 1 meter. The lateral gas dispersion coefficient increases significantly as the bluff internals exist in the riser.

The Ejffect of Vertical Internal Baffles on Fluidization Hydrodynamics and Grain Drying Characteristics

The effect of vertical internal baffles on the particle mixing and graindrying characteristics in a batch fluidized bed column is investigated. Experimental work wascarried out in a 3m high rectangular fluidized bed dryer of cross sectional area of 0.15 m x 0.61 mat different operating conditions using paddy, a group D particle, as the fluidizing material. Theresults of the study showed that the fluidized bed dryer system with vertical internal baffles gavebetter particle mixing effect in the bed of particles than that without vertical internal baffles.This is due to the fact that the vertical internal baffle act as gas bubble breakers by breaking upthe large gas bubbles into smaller ones. The smaller bubbles cause a more vigorous mixing in the bedof particles before finally erupting at the bed surface. This improves the contacting efficiencyand enhanced the heat and mass transfer of the fluidized bed system. Thus a higher drying rate wasobtained in the falling rate period because the higher contacting efficiency increases theevaporation rate at the particle surface. However, the drying rate in the diffusion region showslittle improvement because the moisture diffusivity does not depend on the contacting efficiency.The fluidized bed dryer with vertical internal baffles could therefore be used in the initial rapiddrying stage in a two stage drying strategy for paddy. The insertion of vertical internal bafflesinto a fluidized bed system improves the processing of Group D particles in a fluidized bed systemespecially if the system is large in scale.

Number Concentration of Cylindrical Particles in a Fluidized Bed

In this study, a three-dimensional model based on RANS, slender-body theory and Newton-Euler dynamics is established to study the number concentration, one of the most important fluidization characteristics of cylindrical particles. Also, the effects of interaction between cylindrical particles are taken into account by introducing the rigid collision dynamics. To validate the model, the fluidization experiments of cylindrical particles in a cold-state fluidized bed are carried out. The number concentration characteristics of cylindrical particles are obtained from computational fluid dynamics (CFD) simulation. It is found that cylindrical particles arriving at the exit of the riser the earliest come from the near-wall regions, the horizontal transfer of so many cylindrical particles from the radial centre regions to the near-wall regions is evident. Meanwhile, there is no distinct relationship between the number concentration and inlet wind velocity.

The Axial and Radial Solid Loadings up the CFB-Riser

1 INTRODUCTIONThe determination of the solids hold-up and local solidfluxes is of paramount importance in the study ofthe hydrodynamics of a two-phase flow.Several tech-niques have been used during the past decades(Table1).These methods can be classified in two groups,depending on their possible disturbance of the two-

Study on Liquid-Phase Axial Dispersion in Converging Taper Liquid-Solid Fluidized Beds

It is found analytically that the parabolic radial profile of liquid velocity in cylindrical liquid-solid fluidized bed (LSFB) causes particles to circulate around some radial position. This is the main reason for liquid-phase axial dispersions. The liquid-phase axial dispersion is depressed as the liquid velocity presents a flatter Bessel radial profile in a converging taper LSFB. The void fraction increases with axial distance in converging taper LSFB. The behavior produces less liquid-phase axial dispersion. Experimental results show good coincidence.