Numerical Simulation of Dust Removal in the Cyclone Collector of a Straw Crusher Based on a Discrete Phase Model

The cyclone dust collector is an important subsystem of straw crushers used in agriculture.In the present study,a new type of dust collector with involute morphology is proposed to obtain better dust removal efficiency with respect to that of classical tangential and spiral dust collectors.A discrete phase model(DPM)method is used in synergy with a turbulence model,and the SIMPLE algorithm to simulate the flow field inside the dust collector and the related particle dynamics.It is shown that the internal flow field features a primary swirl,a secondary swirl and blockage effects.Moreover,for the involute dust collector,the tangential velocity in the initial stage and the pressure in the high-pressure area are larger than those obtained for the classical types.The dust removal efficiency is 37.11%,25.3%,and 16.37%for the involute type dust collector,the tangential type and the spiral type,respectively.

Improving the Energy Efficiency of Cyclone Dust Collectors for Wood Product Factories

Dust collection systems represent a significant portion of a wood product manufacturer’s total electricity use. The system fan works against the static pressure of the entire system—the blast gates, the ductwork, and the upstream or downstream cyclone and/or baghouse. A poor system design (e.g., sharp elbows or undersized ductwork) increases the total amount of static pressure in the system, the fan’s performance curve shifts, increasing the total brake horsepower required by the fan (up to the maximum point on the curve). Additionally, system designers may oversize a dust collection system to ensure adequate dust capture and transport, either to accommodate system expansion or simply to be conservative. Since theoretical fan energy use increases with its velocity cubed, this can be an expensive safety net. This paper presents a comprehensive literature review about industrial cyclone dust collectors energy saving in relation to management, technologies, and policies. Energy-saving technologies like high-efficiency motors (HEMs), variable-speed drives (VSDs), leak detection, and pressure drop reduction have all been examined. Based on energy saving technologies results, it has been found that in the industrial sectors, a sizeable amount of electric energy, and utility bill can be saved using these technologies. Finally, various energy-saving policies were reviewed.

旋风滤布除尘器的除尘性能研究

为了解决传统旋风除尘器对颗粒捕集效率差、袋式除尘器使用寿命短等问题,将传统旋风除尘与滤布除尘有效结合,形成一种优势互补的一体式旋风滤布除尘装置。采用数值模拟和试验相结合的方法,探究在不同出口压力的条件下,旋风滤布除尘器的除尘效率及压力损失情况。利用Fluent软件对旋风滤布除尘器的除尘性能进行模拟,模拟采用雷诺应力模型(Reynolds Stress Model, RSM)和多相流模型(Discrete Phase Model, DPM)。通过搭建试验平台,测试除尘装置的除尘性能,验证数值模拟的可靠性与正确性。结果表明:旋风滤布除尘器的除尘效率相对于旋风除尘有明显的提高,旋风滤布除尘器的除尘效率与出口负压呈正相关,旋风滤布除尘总效率随出口负压的增加而逐渐增加,且旋风滤布除尘器除尘效率的最小值都高于旋风除尘部分除尘效率的最大值;旋风滤布除尘器的压力损失随出口负压的增加而线性增大,压力损失增大使得除尘器损耗的功率也增多,且压力损失的上升速度快于除尘效率的提升速度;在旋风滤布除尘器中,负压增大后,旋风除尘捕获大粒径颗粒,逃逸到滤布部分的颗粒粒径都较小,降低了滤布被大颗粒划破的风险,提高了滤袋的使用寿命。

Estimation of Collection Efficiency Depended on FeedParticle Concentration for Axial Flow Cyclone DustCollector

A cyclone dust collector is applied in many industries. Especially the axial flow cyclone is the mostsimple construction and it keeps high reliability for maintenance. On the other hand, the collectionefficiency of the cyclone depends not only on the inlet gas velocity but also on the feed particle concentration. The collection efficiency increases with increasing feed particle concentration. However untilnow the problem of how to estimate the collection efficiency depended on the feed particle concentrationis remained except the investigation by Muschelknautz & Brunner~[6]. Therefore in this paper one ofthe estimate method for the collection efficiency of the axial flow cyclones is proposed. The applicationto the geometrically similar type of cyclone of the body diameters D_1=30, 50, 69 and 99 mm showedin good agreement with the experimental results of the collection efficiencies which were described indetail in the paper by Ogawa & Sugiyama~[8].

Application of Mechanical Similarity Laws to the Collection Efficiencies of Geometrically Types of Uni-Flow Cyclone Dust Collectors

From the mechanical similarity point of view, the centrifugal effect, Ar, and the Stokes number, St, as well as the Reynolds number, Re_c for the motion of solid particles in the cyclone are the relevant parameters. In order to apply these similarity laws for the prediction of the characteristics of the collection efficiency, ηc, geometrically similar types of uni-flow cyclones were used. The body diameters of the cyclones were D_1=30, 50, 69 and 99 mm, respectively. The feed particle concentration of the fly-ash particles was up to C_o = 60g/m^3. From the experimental results: (1) the pressure drop, △pc, in the cyclones was a function of not only the Reynods number, Re_c, but also the body diameter, D_1; (2) the collection efficiency, η_c, did not always increase with decreasing body diameter but there existed an optimal body size; (3) application of the mechanical similarity laws to the collection efficiency was not always sufficient for estimating the collection efficiency, since the feed particle concentration was an additional important factor; (4) a new parameter which was the ratio, E_(pf), of the apparent separation energy, W_p, of the solid particles to the energy loss, E_c, of the gas flow in the cyclone was introduced for discussing the collection efficiency; (5) Fuchs theory, used to estimate the collection efficiency, was examined. Fuchs theory may be applied for high feed particle concentration.

Contributions of the Secondary Jet to the Tangential Velocity Distribution and to the Collection Efficiency of the Fixed Guide Vane Type Axial Flow Cyclone Dust Collector

In order to control the maximum tangential velocity V?m(m/s)of the turbulent rotational air flow and the collection efficiencyηc(%)using the fly ash of the mean diameter X R50=5.57?m,two secondary jet nozzles were installed to the body of the axial flow cyclone dust collector with the body diameter D1=99mm.Then in order to estimate V?m(m/s),the conservation theory of the angular momentum flux with Ogawa combined vortex model was applied.The comparisons of the estimated results of V?m(m/s)with the measured results by the cylindrical Pitot-tube were shown in good agreement.And also the estimated collection efficienciesηcth(%)basing upon the cut-size Xc(?m)which was calculated by using the estimated V?m(m/s)and also the particle size distribution R(Xp)were shown a little higher values than the experimental results due to the re-entrainment of the collected dust.The best method for adjustment ofηc(%)related to the contribution of the secondary jet flow is principally to apply the centrifugal effect?c(1).Above stated results are described in detail.

Estimations of the Maximum Tangential Velocity V_(θm) in the Vortex Core Region and also the Mean Rotational Velocity V_(oi) near the Concave Wall Surface in the Returned Flow Type Cyclone Dust Collector

There are many types of cyclone dust collectors for separating the fine solid and dust particles from gases in the various industries and also in the home used purposes. For estimating the power loss and the collection efficiency, one of the most important factors is the maximum tangential velocity V0m in the vortex core region in the cyclone body. In order to determine V0~ by the simple method, it is useful to apply the mechanical balance of the angular momentum fluxes under the assumption of Ogawa combined vortex model which is composed of the quasi-forced vortex in the vortex core region and also the quasi-free vortex surrounded the vortex core region and also under the assumption of the introduction of equivalent length Heq corresponding to the cone spaces of the cyclone body and the dust bunker. On the other hand, the mean rotational velocity Voi near the concave wall surface is also estimated by the mechanical balance of angular momentum fluxes with the moment of viscous friction force. For confirming the general applications of the obtained equations, the returned flow types cyclones changed the throat diameter D3 are designed. The material of the cyclone is the transparent acrylic resin. Therefore the inner surface of the cyclone body can be regarded as smooth surface. The comparisons of the measured velocities V~ and Voi by a cylindrical Pitot tube are shown in good agreement with those of the proposed equations. The above stated results are described in detail.

干式钻孔除尘旋风分离技术数值模拟研究

以旋风除尘器为研究对象,建立几何模型,通过FLUENT数值模拟软件对旋风除尘器粉尘收集率进行分析,得到旋风除尘器的筒体高度、阻力、入口风速与粉尘收集率的关系。以数值模拟的结果为依据,设计旋风除尘器样机,并对其各个参数与过滤效率之间的关系进行验证,最终得到旋风除尘器工艺参数。结果表明:最佳筒体高度为1.5倍的筒体直径,入口风速为15 m/s,此时模拟的粉尘收集率为82.47%,阻力为500.76 Pa。实验旋风除尘器过滤效率为80.22%,阻力为494.6 Pa,与数值模拟的结果相近。

发尘角度对旋风除尘效率影响的实验研究

本研究运用旋风除尘实验装置测试旋风除尘器的主要性能,通过改变风机频率和发尘角度,研究了不同风量和发尘角度对除尘效率的影响。随着风机频率的增大,当发尘角度为60°时,除尘效率呈先减小后增大;当发尘角度为为90°、120°时,除尘效率呈先增大后减小在增大。为旋风除尘器如何提高除尘效率提供了理论依据和设计参考。

多类型旋风除尘器壁面磨损对比研究

壁面磨损是制约旋风除尘器发展的突出问题。基于计算流体力学方法,研究了三种常见除尘器(扩散式旋风除尘器、标准比例式旋风除尘器和XCX型单管长锥体旋风除尘器)在相同工况下壁面磨损的情况。计算结果表明,由于旋风除尘器顶端存在顶灰环,磨损区域一部分集中在顶面以下20 mm范围内,另一部分在筒体,呈螺旋状分布。其中,扩散式除尘器磨损速率最大,标准比例式除尘器次之,单管长锥体除尘器最小。通过研究三种除尘器的壁面磨损,为加强此类除尘器壁面防磨提供数值模拟方法和依据。

风力干法选煤除尘新工艺设计与应用

随着国家生态环保要求的提高,对干法选煤过程中产生的粉尘治理力度也越来越大。为提高风力干法选煤的除尘效果,基于几种传统干法选煤除尘工艺的优缺点,在原有技术的基础上,通过加入惯性除尘器、优化布袋除尘器结构,设计了一种新型三级除尘工艺并将之应用在巴西坎迪奥塔二期C火电厂干法选煤项目中。应用效果显示:外排空气中的粉尘含量仅为19.8 mg/m^(3),远小于国家标准规定指标,除尘效果显著,且该除尘系统运行稳定、可靠,无堵塞现象。

露天矿用潜孔钻机旋风除尘器的研究

露天矿用小型潜孔钻机的除尘系统分为2级除尘,旋风除尘器作为第1级过滤,发挥的作用至关重要,影响除尘效率、设备阻力、脉冲滤筒除尘器的寿命。介绍了旋风除尘器的组成、工作原理,设计计算以及运行参数对除尘效率、阻力的影响,结果表明:该套旋风除尘器的结构设计合理,运行状况稳定,收尘效果良好。

新一代切流直流式低阻高效旋风除尘器的研制

切流直流式旋风除尘器是一种新型低阻高效除尘器，由于取消了内旋涡流，使阻力损失降低了５０％以上，对于０～５０μｍ的锅炉烟道飞灰，其总除尘效率达９９％。本文介绍了该型除尘器研制的理论依据、技术关键、结构特点、工作原理、试验台系统的设计以及主要性能的测试结果。

新型超微细粉末干法分级设备的研究与应用

本文基于旋风分级收尘器设计研究了新型超细粉末干法分级设备，主要用于无机粉体材料微细粉的分级，该分级器可同时获得粗、细、微三种不同粒度的产品。该设备在旋风分级器下部引入一定量的二次风，淘洗夹带在粗颗粒中的微粉，从而提高微粉的提取率。试验结果表明：一、二次风量对微粉的提取率有较大影响，提高二次风量可显著提高其提取率。对于中位径ｄ５０为 ２．１５ｕｍ，粒度组成为 ０～１０ｕｍ的Ａｌ（ＯＨ）３，以及 ｄ５０为 ３．６２ｕｍ和１５．９ｕｍ，粒度组成为 ０～４０ｕｍ和０～５５ｕｍ的二种重质碳酸钙，其分级后微粉产品中位径ｄ５０分别为０．７１ｕｍ、０．６６ｕｍ和０．９２ｕｍ，微粉粒度可控制在小于５ｕｍ范围。设备简单、易于操作。

静电旋风除尘器性能的研究

在分析离心和静电分离综合作用的基础上,建立了修正的平衡轨道摸型。利用该半经验模型,可较好地说明静电分离和离心分离作用两者对静电旋风除尘器除尘性能的影响。利用所建立的除尘实验装置,系统地进行了静电旋风除尘器性能实验研究,着重分析了除尘器进口风速、工作电压、电晕极型式和布置方式等因素对除尘器性能的影响。

ZDS型静电－旋风除尘器特性研究

静电旋风除尘器综合了静电、旋风两种除尘器的机理和优点，具有结构简单、运行费用低、除尘效率高等优点。本文分析静电旋风除尘器的除尘机理，并介绍ＺＤＳ型静电旋风除尘器的特性。试验研究表明，该除尘器除尘效率为９６％～９９％，阻力为２００～４００Ｐａ，在劳保及环境领域具有广阔的应用前景。

四角旋流布置喷嘴负压集尘器的降尘效率优化

为了提高负压集尘器的降尘效率、进一步改善采掘工作面环境和安全状况,根据喷雾降尘过程中雾粒与粉尘相对运动特点,提出四角旋流布置喷嘴的新型负压集尘器结构,以集尘器喷嘴喷雾压力、喷雾有效作用区长度、喷嘴直径、喷嘴轴向偏转角及纵向偏转角为设计变量,建立目标函数（最大降尘效率）。采用改进的遗传算法和蚁群算法的混合算法（改进的GAAA）对2～8μm不同粒径粉尘的降尘效率进行参数优化,并对降尘效果进行分析和模拟验证。研究结果表明,随粉尘粒径增加,平均降尘效率先增大后减小,耗水量逐渐增大;最优降尘参数组使平均降尘效率达90.7%,提高了6.6%。

利用高压静电技术改进旋风除尘器性能的研究

常规的旋风除尘器结构紧凑简单、投资省,适用于捕集锅炉排烟中粒径为5～10hm以上的灰粒. 在旋风除尘器结构基础上附加高压静电场的作用,可进一步提高除尘效率,特别是提高微米和亚微米灰粒的捕集效率. 通过建立实验系统和模型,进行了利用高压静电技术改进旋风除尘器性能的实验研究,并对影响除尘性能的参数,如除尘器进口风速、工作电压等进行了系统的探讨与分析,初步掌握了实验模型的最佳运行工况.

矿用湿式旋流除尘风机除尘过程的数值模拟

为研究并提高矿用湿式旋流除尘风机的除尘效果,对其工作状态下的三相耦合流场进行了数值模拟,使用Fluent14.0求解了风机的除尘过程。结果表明,将风机从动轮的转速增大到初次模拟的3倍,除尘率由86%提高到96%;从动轮附近是除尘腔风流速度和全压最大的区域,其附近的筒壁是煤尘沉降的主要位置。

旋风除尘器的压力损失及减阻措施

通过探讨引起旋风除尘器阻力损失的原因 。