旋风除尘器内部流场的数值研究

通过建立旋风除尘器模型,模拟了排气管插入深度对旋风除尘器的压降、气流的切向速度和轴向速度的影响。研究表明,增加排气管的插入深度会增大旋风除尘器的压力损失,但对其内部压力分布的影响却比较小;增加排气管的插入深度对气体切向速度和轴向速度的影响也比较小,在不同高度上,内外旋流交界处切向速度的最大值都有所增加,这会产生更大的离心力,除尘效率也会因此而提高。     

入口速度对静电monolith过滤器通道过滤性能的影响

采用单通道理论模型分析了表面带有静电的monolith过滤器通道的过滤性能。重点研究了气流入口速度大小和方向对通道捕获效率的影响,为设计和制造高效率低能耗的monolith过滤器提供理论指导。结果表明:对于直径1μm以下粒子气流入口速度大小u0的增加会降低通道的捕获效率,当u03 m/s时,通道的捕获效率接近于零,对于直径1μm以上粒子随着气流入口速度u0的增加,通道的捕获效率先减小后增大,出现一个极小值;在保证过滤器流量下,气流入口角度的增大会增加通道对直径1μm以上粒子的捕获效率,而对直径1μm以下粒子的捕获效率几乎没有影响。     

直筒式旋风脉冲静电除尘器性能研究

实验研究了电压、入口粉尘浓度和入口风速对直筒式旋风脉冲静电除尘器除尘效率的影响,测定了在不同入口风速下除尘器的分级效率.结果表明,脉冲供电能显著提高除尘器的除尘效率和分级效率,在脉冲电压为80 kV、入口粉尘质量浓度为5.0 g/m3N、入口风速为7～10 m/s时,除尘效率在99%以上,并在实验的基础上分析了脉冲供电下除尘器的除尘机理.     

旋流分离器油水分离效率的模拟研究

采用计算流体力学的方法,探讨了操作条件和物料特性对旋流分离器分离油水效率的影响。旋流器为单锥双入口,其主直径为50 mm,锥角为5.5°。模拟过程中,采用商业用软件‘Fluent 6.3’中的雷诺应力模型和欧拉多相流模型来模拟不同条件下油水旋流分离器的分离性能。模拟结果表明,对于本研究的油水旋流分离器,最佳的分流比是10%,最佳的油滴浓度是0.5%(V/V)。在最佳的分流比和油滴浓度下,当进口流速为10.46 m/s时,油水旋流分离器可将15μm的油滴去除80%以上,油滴的分离界限粒径d50(50%的分离效率)为9.2μm。在模拟的基础上,用统计软件STATISTICA6.0对分离效率与操作条件和物料特性之间的关系进行拟合。通过拟合式预测的分离效率与实测值相吻合,误差小于15%。     

柴油机Urea-SCR系统喷射雾化的数值模拟

为研究柴油机Urea-SCR系统喷射雾化规律,应用CFD软件建立喷射雾化模型,对喷嘴喷射距离、喷射位置与方向、喷孔数目与孔径对催化剂载体入口处的浓度分布情况的影响进行了数值模拟。结果表明,喷嘴距反应器距离为排气管直径5倍为宜;采用四喷孔、孔径为0.5 mm、喷嘴处于管道中心,喷射方向为径向时喷射雾化均匀性最好。通过台架实验,验证了采用喷距5D、径向、四孔、小孔径喷嘴方案可使NOx的转化率达到95%以上。     

下排气旋风分离器结构优化研究

下排气旋风分离器是一种新型的气固分离装置,但存在对细颗粒夹带严重,导致细颗粒分离效率稍低的现象.采用RNG k-ε湍流模型和拉格朗日坐标系下的离散相模型,对75 t/h循环流化床锅炉的下排气旋风分离器的气固两相流动进行数值研究并提出结构优化措施.结果表明,下排气旋风分离器进口改为减缩型、排气管位置下移并采用圆台入口,对...     

钩板除雾器转折次数对除雾效率的影响

除雾器是用来除去烟气中细微液滴、降低污染物、保证系统正常运行的关键设备,故除雾器的研究具有重要意义。利用流体力学计算软件,分析无钩板与带钩板除雾器转折次数对除雾效率的影响。结果表明:除雾器增加转折次数和钩板都可以提高除雾效率,但同时会造成压降增大;增加钩板对除雾效率和压降的影响要高于增加转折次数的影响,带钩板的除雾器对2～10μm直径的液滴具有较理想的去除能力,对于粒径为8μm的液滴,当入口气体流速为3 m·s~(-1)、B=4时,带钩板除雾器除雾效率已达78.2%,并且增加带钩板除雾器的转折次数对除雾效率的提升要高于无钩板除雾器;液滴捕集模拟计算发现,当入口流速为3 m·s~(-1)、B=3时的除雾效率已达91.45%,比初始结构提升约20%。通过分析可知,除雾器可以通过增加钩板以及转折次数来提高对细微液滴的除去能力。     

沸石吸附及其固定化微生物间歇式活性污泥法同时硝化反硝化脱氮的研究

以2种粒径(＜0.25 mm和0.2～1.0 mm)的天然沸石为实验材料,进行沸石吸附NH4+实验以及吸附饱和后固定化微生物间歇式活性污泥法(SBR)同时硝化反硝化(SND)脱氮实验.结果表明,实验沸石对NH4+的吸附等温线符合Langmuir吸附模型,小粒径天然沸石吸附NH4+效率较高.将小粒径天然沸石投加到SBR反应器中,与平行实验的SBR反应器相比发现,天然沸石在再生的同时能够增强SBR反应器的脱氮效率.     

钢渣处理电厂循环冷却排污水中的有机膦

利用热泼渣和滚筒渣去除电厂循环冷却排污水中的有机膦,考察了粒径、搅拌速率及初始p H对两种钢渣除膦效果的影响,并对钢渣除膦动力学特性进行分析。结果表明,钢渣粒径会明显影响其除膦效率,钢渣粒径越小,其除膦速率越快,平衡吸附量越大。小粒径钢渣除膦更符合二级动力学,而一级动力学模型则适用于粒径大于1.25 mm的钢渣。搅拌有助于提高钢渣除膦效率,但增大到一定程度后,搅拌速率对除膦效率影响不大。酸性条件更有利于滚筒渣除膦,热泼渣的除膦速率随p H上升而升高,但其平衡吸附量则呈下降趋势。两种钢渣除膦的最佳p H均为5.0。     

荷电水雾除尘器捕尘效率的实验研究

实验分析了影响荷电水雾除尘器除尘效率的主要因素,在此基础上提出了一种新的除尘效率数学模型,该模型明确地表达了过滤风速、喷雾量以及雾滴荷质比对除尘效率的贡献情况。对实验结果及数学模型的分析表明,对于带有振弦栅的荷电水雾除尘系统,喷雾量对除尘效率的影响比过滤风速及荷质比更为显著,新除尘效率模型的提出对指导生产具有重要意义。实验中同时确定了荷电水雾除尘器最佳操作参数,在粉尘入口浓度为412 mg/m3的情况下,当过滤风速为16 m/s,喷雾量为12×10-3 m3/min,雾滴荷质为3.5×10-4 c/kg时,除尘效率可达99.5%。     

Changes in physical properties of a compost biofilter treating hydrogen sulfide

A technique is presented that can be used to estimate the changes in physical structure in a natural biofilter packing medium, such as compost, over time. The technique applies information from tracer studies, grain size distribution, and pressure drop analysis to a model that estimates the number of channels, average channel diameter, number of particles, and specific surface area of the medium. Important operational factors, such as moisture content, pressure drop, and sulfate accumulation also were evaluated both in a conventionally operated biofilter and in one operated with periodic compost mixing. In the conventionally operated laboratory-scale compost biofilter, hydrogen sulfide (H2S) removal efficiency decreased from 100% to approximately 90% over 206 days of operation. In a similar system, operated with compost mixing, the H2S removal efficiency was maintained near 100%. Variations in media moisture conditions and specific surface area can explain the results observed in this study. Under conventional operation, drying near the inlet disintegrated the compost particles, producing a large number of particles and flow channels and increasing the specific surface area. At the top of the column, where moisture was added, particle size increased and specific surface area decreased. In the column with media mixing, moisture content, particle size, and specific surface area remained homogeneous.     

旋风除尘器流场及浓度场实验与模拟

在研究旋风除尘器内气固两相的运动状况及分离机理方面,计算机模拟替代部分实验的方法能够优化设计旋风除尘器结构参数,提高其对微细颗粒的捕集效率,减少运行压力损失。本研究采用RSM模型和随机轨道模型对旋风除尘器内流场及浓度场进行模拟及实验。研究表明,旋风除尘器压力损失模拟结果与实验结果吻合较好,对于大于5μm的颗粒其捕集效率模拟结果与实验结果基本吻合;旋风除尘器外壁的颗粒浓度呈螺旋带状分布;如将排气管管径减少至原直径0.8倍,可使其对2μm颗粒捕集效率提高6.6%,但压力损失提高36.5%;颗粒的凝并作用有利于提高旋风除尘器微细颗粒的捕集效率。     

An Inertial-Type Particle Separator for Collecting Large Samples

A two-stage inertial-type particle separator has been developed for collecting large size-selective samples of particulates on filters. The sampler operates at a flow rate of 1.4 cubic feet per minute and may be run for extended periods without change in collecting efficiency. The particle size cut of the sampler is at a diameter of 1.4 microns; separation of greater than 90 percent is obtained for particles below 0.80 micron and above 2.0 microns. The sampler was calibrated with monodisperse polystyrene latexes. Data are presented to relate the separating efficiency of the sampler to its separation parameters.     

非均质多孔介质对水平潜流人工湿地水力效率的影响

对比以不同粒径(4～9、8～12、11～17mm)非均质多孔介质(玻璃珠)作为基质的水平潜流人工湿地(以有机玻璃板材模拟)的水力效率、水力停留时间等参数,并参照其流态变化进行分析。结果表明:(1)均以上端为进水口、下端为出水口,水流流经不同粒径玻璃珠的水平潜流人工湿地会产生不同的流态。(2)玻璃珠粒径小(4～9mm)的水平潜流人工湿地中,染料在其中运动并最终能够迁移到出水口的有效空间最大,空间利用率最大,则有效体积比最大,染料流经区域面积最大;转角处染料呈圆角流过,死区范围小。(3)当玻璃珠粒径为4～9mm时,水平潜流人工湿地具有最长的平均水力停留时间(0.437 8h)和最小的水流散度(标准方差为0.052 5),使得水平潜流人工湿地的有效体积比最高(0.495 7),水力效率也最高(0.469 6)。随着粒径的增大,平均水力停留时间缩短,水流散度增大,而有效体积比和水力效率均呈减小趋势。(4)合理的水力停留时间分布能够提高有效体积比,而有效体积比越高,即污水在水平潜流人工湿地中运动并最终能够迁移到出水口的有效空间越大,污染物与基质以及附着在基质上的微生物的接触越充分,从而提高污染物的去除率。     

Evaluation of cyclone performance in different gases

A new set of the cyclone efficiency data is reported. The particle collection efficiency data have been obtained as a function of particle size, flow rate, cyclone size, and gas properties. Cyclones of four different dimensions were used covering a flow rate range of 9.1–19.5 l min ⁻¹ and a particle size range of 0.5–25 μm. Both liquid and solid particles were used. For varying the gas properties, air and argon were used.The experimental results suggest that in addition to the gas viscosity, the gas density plays an equally important role in cyclone performance. It was found that increasing the gas density enhances particle collection characteristics. Among the several parameters tested, the Reynolds number using the inlet gas velocity and the exit tube diameter was found to show the strongest correlation on the cut size.     

石膏浆液旋流器的分离性能实验研究

通过理论分析及工程经验对石灰石/石膏法烟气脱硫工艺中石膏浆液脱水系统的旋流器进行优化设计,在与工业实际相近的操作条件下,优选出了一根综合性能较好的旋流器。考察了该旋流器的压力、流量与分离效率之间相互关系,与常规石膏浆液旋流器的分级效率进行了比较,确定了最佳操作条件。结果表明,旋流器的进口流量随着进出口压力差的增大而增大,分离效率随着流量增加先上升后下降。在进口硫石膏颗粒平均粒径为24μm,流量为11.8~14.8 m3/h时,分离效率在85%以上,底流出口10μm、15μm以下的颗粒分别占底流出口颗粒总体积的1%、10%左右,起到了很明显的分级浓缩作用,分离性能也优于常规使用的石膏浆液旋流器。     

ESP粉尘收集性能的影响因素

为了进一步提高电除尘器的收尘效率,尤其是对高比电阻粉尘的收尘效率,依据非稳态静电收集理论,对影响电除尘器粉尘收集性能各项因素的作用程度及机理进行了进一步研究。实验研究了粉尘收尘效率与不同比电阻粉尘的最优极间距、最优工作电压、粉尘层厚度和比电阻之间的相互关系。研究结果表明,随着极间距的增加,对应比收尘极面积,对于不同比电阻粉尘的收尘效率的增加幅度是不同的,其中高比电阻粉尘的收尘效率增加的趋势更加显著;粉尘比电阻越高,所对应的最优极间距越大,宽间距电除尘器对捕集高比电阻粉尘具有一定优越性;在最优极间距条件下,粉尘比电阻越高,其所对应的最优工作电压越小;相对于正常比电阻粉尘,随极板沉积粉尘层厚度的增加,高比电阻粉尘的最佳收尘效率所对应的最优工作电压升高幅度较大,而且最优工作电压所对应的收尘效率下降显著。随粉尘比电阻的增大,电除尘器收尘效率逐渐降低,特别是当粉尘比电阻大于1011Ω.cm后,粉尘收尘效率显著下降。研究结果与非稳态静电收尘理论提出的观点相吻合,有助于透彻理解电场结构和运行参数与粉尘收集性能的关系,特别是对于今后研发提高高比电阻粉尘收集性能的针对性技术措施具有指导作用。     

水力旋流器速度场的PDPA测试研究

应用相位多普勒粒子分析仪(PDPA)对液液水力旋流器模型的内部流场进行了测试,分析了旋流器内部速度场的特点。通过进口流量的变化,测试了该模型的不同截面上的速度场分布情况。测试结果表明:随着流量的增大,旋流器轴截面上的速度都增大,旋流变大,有利于连续相和分散相的分离;旋流器中连续相和分散相速度分布趋势相同,但在管芯处,两者速度滑移明显。     

The Prediction of Overall Collection Efficiency of Air Pollution Control Devices from Fractional Efficiency Curves

The application of air pollution control devices requires the prediction of overall collection efficiency from the particle size distribution of the dust and the fractional efficiency of the air pollution control device. The cumulative particle size distribution of dust resulting from industrial processes can usually be represented by a straight line on logarithmic probability paper or a log normal function. The fractional efficiency curves of many air pollution control devices such as cyclones or wet scrubbers can also be adequately represented by a log normal function. Only two parameters are required to define a log normal function, a median diameter and a geometric standard deviation. Both of these can easily be obtained from a plot on logarithmic probability paper. The overall collection efficiency has been found to be Very simply related to the four parameters required to define the log normal functions representing the particle size distribution and the collector fractional efficiency. These four parameters are: the mass median diameter and the geometric standard deviation of the dust size distribution, the cut diameter (50% efficiency diameter), and geometric standard deviation of collector fractional efficiency curve. Using this relationship the prediction of overall collection efficiency is greatly simplified with no loss of accuracy.     

Effect of the location of the inlet and outlet structures on short-circuiting: experimental investigation.

The location of the inlet and outlet structures in a treatment plant (e.g., waste stabilization pond) may affect its hydraulic efficiency by increasing short-circuiting. Therefore, in this paper, the effect of the location of inlet and outlet structures was investigated in three laboratory channels of different lengths. Nine different combinations of inlet and outlet locations were considered for each channel under varying rates of flow. Results showed that the placement of the inlet and outlet structures close to the surface and the bottom of the pond, respectively, gave the minimum value of short-circuiting. This location was, therefore, judged to be the optimum among the nine combinations considered. The short-circuiting index was found to increase both with the dispersion number and the actual flow velocity, giving correlation coefficients of 0.3186 to 0.9258 and 0.8057 to 0.9972, respectively. Although minimization of short-circuiting will result in higher hydraulic efficiency, it may not necessarily result in higher effluent quality unless the temporal and vertical fluctuations of the water column are also considered.