局部通风作用下阵发性污染物浓度分布规律研究

发布时间：2018-02-14 02:58

本文关键词： 局部通风阵发性污染源非稳态过程浓度分布因素分析　出处：《西安建筑科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：在转炉添加钢水、渣车倒料和焦炉作业等工业生产过程中,往往存在不连续释放污染物的污染源,也即阵发性污染源。由于污染源的间歇性释放,其所产生污染物浓度分布是非稳态的,且污染物的产生量也是不稳定的,因此在实践中不好控制。本文在数值模拟计算方法验证的基础上,以一氧化二氮(N2O)为示踪气体,利用Fluent软件研究了在局部排风系统作用下该类污染源所产生非稳态污染物浓度场的变化规律。首先,根据课题组实验,通过对温度场实验与模拟数据的误差分析完成了稳态模拟计算方法的验证,在此基础上,通过对排风系统(局部与全面通风)污染物浓度的误差分析实现了非稳态模拟计算方法的验证。其次,分析了非稳态过程(该过程主要包括散发稳定与衰减阶段)初始流场、排风系统与典型空间点(人员静坐、站立时口鼻高度以及高空作业高度)浓度变化规律,以及散发稳定阶段局部排风系统瞬时捕集效率,且对衰减阶段排风系统浓度变化进行了公式拟合。最后,分析了污染源强度(污染物浓度和气流速度)与局部排风量对非稳态过程排风系统与典型空间点浓度变化的影响。本文工作得到如下主要结论:(1)在散发稳定阶段,排风系统污染物浓度随着时间的变化先增加后趋于稳定,且全面通风系统浓度曲线达到稳定的时间滞后于局部排风系统浓度曲线;在衰减阶段,排风系统污染物浓度呈负指数规律衰减。(2)在非稳态过程中,污染源污染物浓度和气流速度与局部排风量单因素变化时,排风系统污染物浓度曲线变化规律一致。分析结果表明采用一氧化二氮(N2O)为示踪气体研究排风罩捕集特性时,示踪气体的浓度不宜过大;污染源气流速度越大,散发稳定阶段浓度曲线变化越迅速,衰减阶段初期变化越明显,同一时刻浓度值越大,相较而言,污染源气流速度对全面排风系统浓度变化规律的影响较小;在某一时刻,排风系统浓度随着排风量的增大而减小,且局部排风量越大,浓度曲线达到稳定状态的时刻越早,衰减阶段曲线变化越平缓。(3)在散发稳定阶段,污染源气流速度越大,某一时刻空间点污染物浓度越大;随着局部排风量的增加,某一时刻空间点污染物浓度降低。在衰减阶段,随着时间的增加空间点浓度先稳定后降低。
[Abstract]:In the process of industrial production, such as adding molten steel to converter, slag car feeding and coke oven operation, there is often a discontinuous pollutant source, that is, a paroxysmal pollution source. The concentration distribution of pollutants produced is unstable and the amount of pollutants produced is unstable, so it is difficult to control in practice. In this paper, based on the verification of numerical simulation method, nitrous oxide (N2O) is used as tracer gas. The variation of unsteady pollutant concentration field produced by this kind of pollution source under the action of local exhaust system is studied by using Fluent software. Based on the error analysis of temperature field experiment and simulation data, the steady-state simulation method is verified. Based on the error analysis of pollutant concentration in exhaust system (local and total ventilation), the unsteady simulation method is verified. Secondly, the initial flow field of the unsteady process (which mainly includes the stage of emission stability and attenuation) is analyzed. The variation law of concentration between exhaust system and typical space points (person sit-in, mouth and nose height and altitude when standing), as well as instantaneous capture efficiency of local exhaust system in the stage of distribution and stabilization, The variation of exhaust system concentration in attenuation stage is fitted by formula. Finally, The influence of pollution source intensity (pollutant concentration and airflow velocity) and local exhaust air volume on the concentration variation of unsteady process exhaust air system and typical space points is analyzed. The main conclusions in this paper are as follows: 1) at the stage of distribution and stabilization. The concentration of pollutants in exhaust system increases first with time and then becomes stable, and the time of concentration curve of overall ventilation system lags behind that of local ventilation system. The concentration of pollutants in exhaust air system attenuates in a negative exponential law. (2) in the process of unsteady state, the concentration of pollutants, the velocity of air flow and the amount of local exhaust air are changed by single factor. The analysis results show that the concentration of tracer gas should not be too large when using nitrous oxide N _ 2O) as tracer gas to study the capture characteristics of exhaust hood, and the air velocity of pollution source is higher. The faster the concentration curve changes in the stable phase of emission, the more obvious the change in the initial stage of attenuation is, and the greater the concentration at the same time. Compared with the change of concentration in the overall exhaust system, the air velocity of the pollution source has less influence on the variation of the concentration of the total exhaust system at a certain time. The concentration of exhaust system decreases with the increase of exhaust air volume, and the larger the local exhaust volume is, the earlier the concentration curve reaches the stable state, and the more gentle the decay phase curve is, the more the air velocity of pollution source increases at the stage of emission stabilization. The higher the concentration of pollutants is at a certain time, the lower the concentration of pollutants is at a certain time with the increase of local exhaust volume. At the attenuation stage, the concentration of space point first stabilizes and then decreases with the increase of time.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X51;TU834

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