工业物料自由下落过程产尘机理及高效控制策略

Free falling and transfer process of bulk material are common in the process of industrial production, during which the dust can be generated, one of the main pollution source of indoor environment. It accumulates continually in building enclosure , which can not only cause damage to equipment, but also impose threat on worker’s health both physically and psychologically. Under the background of metallurgy industry, this project aims at dust generation caused by free falling of industrial bulk material. Based on the theory of gas-solid two phase convective mass transfer, it expounds dispersive characteristics of dust source of free falling particles stream, and reveals the movement rule of airflow containing dust under coupled effect of falling particle, rebounding particle and entrainment airflow, in order to determine the environmental evaluation index of targeted control region in building enclosure. Then, on the base of dust movement driven by ventilation system, distribution characteristics such as velocity profile and concentration profile can be obtained. Next, mechanism of weakening mass transfer and velocity threshold for dust control are explored, so as to guide optimal configuration of ventilation system structure and determine ventilation system design. The whole study can provide theoretical reference for environmental control in working area with free falling of bulk material.

工业生产普遍存在散状物料自由下落及转运过程，这些过程产生的粉尘是造成工业建筑环境污染最重要的源项之一。在建筑围合空间中粉尘浓度会不断累积，严重影响安全生产及工人的身心健康。本项目以冶金行业为背景，以工业散状物料自由下落产尘过程为研究对象，基于气固两相对流传质理论，阐明下落颗粒流尘源散发特性，揭示下落颗粒、反弹颗粒与卷吸气流耦合作用下的含尘气流运动规律；明确建筑围合空间内目标控制区的环境控制评价指标；基于通风系统作用下的粉尘迁移规律，得到速度场、浓度场的分布特性；寻求弱化传质的机理和控制粉尘的速度限值，指导通风系统结构形式的优化配置，确定通风系统形式；为具有散装物料自由下落过程的工作区环境控制提供理论依据。

工业散状物料的转运环节普遍存在于工业生产过程中。此过程产生的粉尘是工业建筑环境最主要的污染物之一。在建筑围合空间中不断积累会加剧环境污染、影响生产并危及工人的身心健康。本研究针对冶金企业的生产现状进行了深入研究，揭示了自由下落颗粒流沿轴向依次出现稳定段、过渡段及扩散段三个流段，并对三个流段进行了定量化描述；揭示了颗粒流的扩散直径、边界层半宽度和无量纲核心直径随下落高度的变化规律，揭示了颗粒流冲击下垫面后三个运动过程，揭示了颗粒流携带卷吸气流冲击下垫面后卷吸气流成涡形式沿水平方向向外扩散规律；发现了颗粒流下落处于不同流段产尘特性及数学规律，提出当颗粒流与下垫面的碰撞发生在过渡段时应重点减少碰撞产尘，当碰撞发生在扩散段时应重点减少扩散产尘的控制策略；揭示了斜面出流颗粒流下落过程的产尘规律，获得产尘率最小的出流角度为45°；发现了在转运廊道围合空间中，粉尘浓度、相对湿度、温度均超出工作场所浓度限值；揭示了廊道内的污染物主要来自铁渣本身；揭示了冬夏季廊道内环境的异同性，为更好的控制廊道内工作环境提供良好的实验基础；提出一种新型的控尘模式，该控尘方法利用“真空”区域诱导含尘气流进而在有限空间中更有效地捕集含尘气流，从而降低除尘设备的能耗。