基于振荡天平法的烟尘浓度在线监测装置

发布时间：2018-07-05 04:33

本文选题：振荡天平法 + 烟尘浓度　；参考：《太原理工大学》2017年硕士论文

【摘要】：随着我国各行各业的飞速发展,空气质量越来越差,严重威胁着大家的身体健康,因而引起了广泛的关注和重视。固定污染源排放是大气污染的主要因素之一,它是我国环保部门重点监测的一项指标。为满足国家对固定污染源超低浓度排放监测的要求,本文提出一种基于振荡天平法的烟尘浓度在线监测装置,其核心思想是利用物体固有频率与其自身的质量间有某种固定的函数关系,确定了物体的固有频率就可以间接得到物体的重量。用高精度频率测量电路对烟尘采样前后振荡管的固有频率进行测量,通过计算得到采样烟气中含有的烟尘颗粒物的质量。本文的主要工作如下:(1)基于振荡天平法烟尘浓度在线监测系统的设计。其烟尘采样部分利用模糊PID算法,实现了对烟道烟气的等流速采样。其烟尘连续称重部分采用振荡天平法的原理,实现了对烟尘颗粒物的精确连续称量。其烟尘样气检测部分实现了对采样烟气体积的温压补偿和氧含量折算。其数据显示部分实现了对烟尘浓度等关键数据的实时监测,并且提供历史曲线和数据报表等。该系统实现了对超低浓度排放下烟尘浓度的实时监测。(2)利用有限元分析软件ANSYS对振荡天平法质量传感器的核心元件振荡管进行了动力学建模和仿真。对不同参数下振荡管的振荡特性进行了细致仿真,得到了各种参数与振荡特性之间的关系,确定了振荡管结构的最优设计方案,该方案下的振荡管测量灵敏度很高,满足对超低浓度检测的要求。(3)设计了振荡天平法质量传感器的硬件电路。利用DDS芯片AD9832来生成频率可调节的激励信号。用相位差检测的方法来实现对振荡管固有频率的捕捉测量,频率测量电路的精度影响着质量传感器称量的精确度。根据等精度测频法的原理,利用具有100MHz晶振的FPGA,来实现对检测信号频率的测量,其测量精度可以达到0.001Hz。通过将振荡天平法质量传感器与分析天平进行比对,测量数据相对误差较低,能够精确称量0.1mg的烟尘颗粒物。将该质量传感器模块加入到烟尘浓度在线监测装置中,测量结果与离线式的滤膜称重采样法的测量结果具有较高的一致性。说明本文的基于振荡天平法的烟尘浓度在线监测装置具有使用价值,相信经过不断探索和改进,该产品应用前景十分广泛,能应用在工业、农业以及社会生活的有关环境质量检测的领域中去。
[Abstract]:With the rapid development of various industries in China, the air quality is getting worse and worse. The emission of fixed pollution source is one of the main factors of air pollution, and it is a key monitoring index of environmental protection department in China. In order to meet the requirements of the national monitoring of ultra-low concentration emissions from stationary pollution sources, an on-line monitoring device for smoke and dust concentration based on oscillatory balance method is proposed in this paper. Its core idea is to make use of the fixed function relationship between the natural frequency and the mass of the object, and determine the inherent frequency of the object can indirectly get the weight of the object. High precision frequency measurement circuit is used to measure the natural frequency of the oscillating pipe before and after the smoke sampling, and the quality of the smoke particles contained in the sampled flue gas is obtained by calculation. The main work of this paper is as follows: (1) the design of on-line monitoring system of smoke concentration based on oscillatory balance method. In the part of smoke sampling, fuzzy pid algorithm is used to realize the equal velocity sampling of flue gas. The principle of oscillatory balance method is used in the continuous weighing of smoke and dust, and the accurate and continuous weighing of smoke particles is realized. The temperature and pressure compensation and the conversion of oxygen content to the sample smoke volume are realized in the smoke sample gas detection part. The data display part realizes the real-time monitoring of the key data, such as smoke and dust concentration, and provides historical curves and data reports. The system realizes the real-time monitoring of smoke concentration under ultra-low concentration emission. (2) the dynamic modeling and simulation of the oscillation tube, the core component of the mass sensor of the oscillating balance method, are carried out by using the finite element analysis software ANSYS. The oscillation characteristics of the oscillating tube under different parameters are simulated in detail, the relationship between the parameters and the oscillation characteristics is obtained, and the optimal design scheme of the oscillating tube structure is determined. The measurement sensitivity of the oscillating tube under this scheme is very high. It meets the requirements of ultra-low concentration detection. (3) the hardware circuit of the mass sensor with oscillating balance method is designed. DDS chip AD9832 is used to generate frequency adjustable excitation signal. The method of phase difference detection is used to capture and measure the natural frequency of oscillating tube. The precision of frequency measuring circuit affects the accuracy of weighing of mass sensor. According to the principle of equal precision frequency measurement, FPGA with 100MHz crystal oscillator is used to measure the frequency of detection signal. The measuring accuracy can reach 0.001Hz. By comparing the oscillatory balance mass sensor with the analytical balance, the relative error of the measured data is relatively low, and the smoke particles of 0.1mg can be accurately weighed. When the mass sensor module is added to the on-line monitoring device of smoke concentration, the measured results are in good agreement with those obtained by the off-line filter weighing resampling method. The results show that the on-line monitoring device of smoke and dust concentration based on oscillatory balance method has practical value. It is believed that the product has a wide application prospect and can be used in industry after continuous exploration and improvement. Agriculture and social life in the field of environmental quality testing.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP274

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