【作者】 李小川；

【导师】 胡亚非；

【作者基本信息】 中国矿业大学 ， 矿物加工工程， 2013， 博士

【摘要】 皮带输运在工业短距离散装物料输送过程中应用广泛，但转运点常伴随有扬尘现象，特别在矿物加工与冶炼、水泥生产等初级产品生产过程更为严重。工业常用的“分散捕获、集中净化”抑尘模式存在通风管路复杂、易堵塞、堵塞后维护难度大、除尘能耗高等缺点，极不适合高产尘环节的粉尘抑制与净化。本文提出了“分散捕获、就地净化”的抑尘模式，依托徐州市兴达烧结厂转运点粉尘治理项目，对烧结矿粉尘理化特性和基本流动行为、转运点诱导气流大小、吸尘罩对粉尘捕获特性、湿式除尘器主要结构参数、阻力特性和除尘效率等进行了研究，并在烧结厂转运点进行了创新实践与推广应用。研究了烧结矿粉尘物理化学特性。烧结矿粉尘真密度约为3.854⁴.195g/cm³，球形度约为0.51⁰.93，浸润速度约为0.306⁰.483cm/min，皮带输运物料中粒度小于125μm的粉尘约占2.23%，粉尘中T.Fe含量约为44⁴6%，净化工艺过程需考虑回收利用。研究了气流场中粉尘颗粒的基本流动行为。烧结矿粉尘的自由沉降粒度分区主要落在Stockes区和Allen区，在Stockes区可用沉降末速度近似表示粉尘沉降速度，在Allen区需将加速沉降段和等速沉降分开考虑；呼吸性粉尘在静止气流场中的惯性运动和扩散作用都很弱，在水平湍流场中的跟随性较强；水平湍流场中粒度大于10μm的粉尘与气流的滑移速度较大，粉尘的运动轨迹受水平气流速度和粉尘沉降速度共同影响。研究了转运点物料下落产生诱导气流的大小，建立了诱导气流速度的经验模型。以量纲分析为着手点，推导出两个与诱导气流速度相关的无量纲准则数：Re和m_p/ρ_gg^1/2h^3/2D数，并建立了相似实验模型。相似实验研究认为对同一物料，诱导气流大小随物料质量流量和下落高度变化的趋势规律性很强；在实验粒度范围内，由于颗粒间相互作用的影响，诱导气流速度随粒度变化趋势规律性较差。研究了吸尘罩抽吸气流流速范围。随抽吸气流速度增大，诱导气流的扬尘作用逐渐被抽吸气流对粉尘的捕获作用取代，当抽吸气流增加到一定值后，抽吸气流对附着在料床上静止的粉尘起到扬尘作用。抽吸气流越大，吸尘罩捕获粉尘中大粒度粉尘百分比和粉尘总质量都增多，抽吸气流的上限风速应不能大量激扬附着在料床上的粉尘（约9.20m/s），下限风速应能完全抽吸诱导气流。通过模型实验对节流自激式除尘器主要结构参数进行了研究。结果显示，接触腔高度直接影响除尘效果，合适高度约为300mm；两级节流气液混合效果比单级好，较好的级间配合是：一级节流强度较大（α=250/300²35/300），用于激发液滴，二级节流强度较小（α=150/300²20/300），用于强化气液混合效果。发现了除尘器阻力的液相调节特性。液相通过改变节流液位差Δh调节节流口前后气液两相的受力平衡，进而改变除尘器总阻力系数，抑制气相阻力的增加。在液相调节作用的影响下，节流强度α随除尘器流速线性减小；除尘器总阻力系数ξ随气相流速增加而成倍降低，随节流强度增加而成倍增加，气相总阻力可间接用节流液位差Δh表达。除尘器经济合适的入口流速约为3.26⁵.37m/s。建立了节流自激式除尘器分级除尘效率模型。将捕尘分为液面捕尘和液滴捕尘两个阶段，理论模型显示，液面捕尘对大颗粒粉尘有较高的分级除尘效率；液滴捕尘对大颗粒粉尘和呼吸性粉尘都有较高的分级除尘效率，液滴捕尘效率主要与气粒速度系数ζ1和除尘器流量有关。实验结果显示，气粒相对速度系数约为ζ1=0.79，呼吸性粉尘除尘效率达98.26%；除尘效率随进气口粉尘浓度升高而升高，排气口粉尘浓度随进气口浓度增加而增加；除尘器初始液位b0和流量对除尘效率有很大影响，合适的b0值介于-15¹4mm，入口流速应不低于2.93m/s。验证了“分散捕获、就地净化”抑尘模式的可行性。现场应用显示，该抑尘模式降低了粉尘排放量和管路堵塞故障率，总除尘效率达98%以上，降低能耗约14.6%，目前已进行13个转运点的改造，具有较好的推广前景。论文共包含图54幅，表40张，参考文献168篇。更多还原

【Abstract】 Belt conveyor is actively used in short conveying process of industrial for bulk materials.But the transfer station of belt conveyor often has the dust phenomenon, especially in theprimary products process of the mineral processing and smelting, cement production, etc. Dustsuppression model known as “Scattered capture, Centralized purification”is a common methodin the industry. It is not extremely suitable for the dust suppression and purification of high dustlink with the disadvantage of complex ventilation piping, easy choking, and difficultmaintenance after blockages, high energy consumption of removing dust, etc. In this paper, anew dust suppression model denoted as “Scattered capture, Local purification”（SCLP） isproposed. It based on the conveyor transfer station dust control program of Xingda sinteringplant in XuZhou city. The physical and chemistry properties of sintering ore and the basic flowbehavior, the induced air flow of conveyor transfer station, the dust-capture feature of dustexhaust hood, the main structural parameters of wet dust separator, the resistance characteristicsand the collection efficiency are studied and those are applying in the conveyor transfer stationof sintering plant.The physical and chemistry property of sintering ore dust is studied. The dust true density isabout3.854⁴.195g/cm³, and the sphericity is about0.51⁰.93, and the wetting velocity is about0.306⁰.483cm/min. The material on the belt conveying has a large amount of dust below125μm which about accounts for2.23%. There are the high level of minerals with about44⁴6%content of T.Fe in the dust. The minerals should be considered effective recycling in thepurification process.The basic flow behavior of dust particles in air flow field is studied. The free setting sizepartition of sintering ore dust is mainly at Stockes region and Allen region. The terminalvelocities can be expressed approximately as the settling velocity of dust at Stockes region, butthe accelerated settlement and uniform settlement must be considered individually at Allenregion. The respiratory dust has the weaker inertia movement and diffusion effect in a stationaryair field, but it has a stronger following performance in a horizontal turbulent flow field. The dustabove10μm in horizontal turbulent flow field has a larger slip velocity with the air flow and thetrajectories of dust need to be decided by horizontal airflow velocity and dust settling velocity.Induced airflow velocity which is produced by the dropping of conveyor transfer stationmaterial is studied and the empirical model of induced air velocity is built up. With thedimensional analysis as the starting point, two dimensionless criteria named Re andm_p/ρ_gg^1/2h^3/2D number related to the induced airflow are set up. The similar experiment showsthat the induced air velocity has a strong regularity trend with the material mass flow velocity and drop height to the same material. Because of the interaction influence on particles, theinduced airflow velocity has a poor trend with the particle diameter when the drop height is inthe experimental particle diameter range.The suction airflow velocity range of dust exhaust hood is studied. The raising dust effect ofinduced airflow is gradually replaced by catching dust effect of suction airflow with the increaseof suction airflow velocity. When suction airflow increases to a certain value, the suction airflowhas an effect on raising motionless dust which attached to the materials bed. The percentage oflarge granularity dust and total dust mass, which are caught by dust exhaust hood, increase alongwith the increase of suction airflow. The upper limit wind velocity of suction airflow should notblow a large number of dusts which attached to the materials bed （about9.20m/s）. Theminimum wind velocity should be able to completely absorb induced air flow.The main structural parameters of throttling self-excited dust separator are studied by modelexperiment. The results show that the contact cavity height directly affects the dedusting effectand its suitable height is about300mm. Two-stage throttling effect of gas-liquid mixing is betterthan single-stage. The better interstage matching is that the primary throttling intensity is bigger（α=250/300²35/300） to stimulate droplets and the secondary throttling intensity is smaller（α=150/300²20/300） to strengthen the effect of gas-liquid mixing.The liquid phase adjustment characteristic for dust separator resistance is found out. Theforce balance of gas-liquid two phase before and after of the throttle is regulated by the changingof throttle liquid-level difference Δh. Then the total resistance coefficient of dust separator ischanged for restraining the increase of gas phase resistance. Due to the influence of liquid phaseadjustment, the throttling intensity α is linearly propotional decreased to the airflow velocity ofdust separator. The total resistance coefficient ξ relatively reduces along with the increase of gasphase velocity and relatively increases along with the increase of throttling intensity. The gasphase total resistance can be indirectly express by the throttling liquid-level difference Δh. Theeconomic and suitable inlet velocity of dust separator is about3.62⁵.37m/s.Fractional collection efficiency model of throttling self-excited dust separator is established.The dust removal process is divided into catching dust on the liquid surface and catching dustwith the liquid droplet. The theoretical models show that catching dust on the liquid surface hashigher fractional collection efficiency for the large-granule dust, and catching dust with theliquid droplet has higher fractional collection efficiency for the large-granule dust and respirabledust. Collection efficiency of catching dust with the liquid droplets mainly depends on thegas-phase velocity coefficient ζ1and the dust separator airflow. The experiment results show thatthe gas-phase velocity coefficient ζ1is0.79and the collection efficiency for respirable dustreaches to98.26%. The collection efficiency raise along with the increase of air inlet dust concentration and the air outlet dust concentration increases along with the increase of air inletconcentration. When the entrance dust concentration is within the range of695.45³667.34mg/m3, the outlet dust concentration meets discharge standards. The initial liquid level b0and thedust separator airflow have a great effect on the collection efficiency. The suitable b0is-15¹4mm. And the inlet air velocity of dust separator is not lower than2.93m/s.The feasibility of “Scattered capture, Local purification”-dust suppression model is verified.The industry field application shows that the model can reduce the dust emission and greatlyreduce the jam failure rate. The total dust removal efficiency is more than98%, and the energyconsumption reduces about14.6%. The13conveyor transfer stations have currently transformed,and the transformation has a good popularization prospect, high economic and social value.更多还原