【作者】 彭小兰；

【导师】 吴超；

【作者基本信息】 中南大学 ， 安全技术及工程， 2014， 博士

【摘要】 摘要：从国家质量监督检验检疫总局近五年的特种设备事故情况通报可知,尽管每年的万台设备事故率有所下降,但是在锅炉台数有所减少的情况下锅炉事故例数仍高居不下。对事故通报原因进一步分析得知：中小工业锅炉中有机热载体炉的火灾事故一直高发。为解决有机热载体炉积碳和火灾事故,本论文依托质检公益性行业科研专项(201210080)“有机热载体炉安全评定及积碳在线检测关键技术研究”和质检总局科技计划类项目(2013QK212)“导热油炉基于FLUENT的流场数学建模和仿真研究”这两个国家质检总局项目,在系统而全面地检索及深入分析以前的学者已经取得系列研究成果的基础上,采取理论分析、试验模拟仿真与实际检测应用三者相结合的研究方法,针对有机热载体炉积碳检测、介质FLUENT流场分布和安全评价三方面进行了深入研究,取得的主要创新性成果如下：1.统计分析了国内近十年有机热载体炉火灾事故以及有机热载体炉积碳检测控制技术的相关论文,阐述了有机热载体炉火灾事故的主要形成原因,并指出有机热载体炉积碳层是导致有机热载体炉火灾的关键因素。2.根据有机热载体介质的物理化学性质和有机热载体炉系统的特殊性,分析了有机热载体积碳形成机理和有机热载体炉运行机理,并提出一种基于超声导波的积碳层厚度检测方法。3.设计组装了一套有机热载体炉积碳检测系统,试验研究了超声导波的截止频率、跃迁频率和群速度这3个表征参数与积碳层厚度变化的关系。结果表明：可用超声导波的群速度与积碳层厚度变化的单调性规律来检测积碳层的厚度,并通过空管中的群速度频散曲线的拟合试验进一步论证该检测方法的可行性。4.为识别积碳检测中超声导波的模态类别,故利用时频分析对炉管中多个模态进行比较分析,并结合时频分析的主要能量分布图与数值模拟的频散曲线中L(0,2)模态走势的拟合,推断出的主要波形模态为L(0,2)模态,通过时差法计算群速度和实验群速度的的相对误差仅为1.88%-3.48%。5.通过模拟附着物超声导波积碳检测试验得到：信号为5周期,频率为500kHz,峰峰值为200mV,激励出的L(0,2)模态波的群速度检测盲区为探头布置间距小于350mm,有机热载体炉管中积碳层超声导波检测探头布置最佳检测距离为40cm。从信号的信噪比、时域和频域特征验证了检测的最佳周期为5周期；可用环氧树脂添加碳氢化合物和模拟积碳层,并成功激励出了L(0,2)模态。当探头间距40cm,检测周期取5周期时,用试验论证了L(0,2)模态在积碳管中的群速度较空管中的群速度减小7.65%,进一步论证了可用空管和积碳管群速度的变化关系来检测有机热载体炉管道中的积碳层。6.将人机工程学原理运用到有机热载体炉运行风险评价中,得出运行中人机环境指标的权重分别为：1.830、1.293、1.749,比较得出入和环境这两个指标比有机热载体炉设备本体的权重大0.5左右。这表明有机热载体炉运行风险需要更多关注人员素质和环境管理。然后通过国内外有机热载体炉火灾事故统计调查,运用鱼刺因果分析法定性地分析了事故原因,再结合事故树分析和事件树分析方法,找到引发火灾事故的基本因素、关键因素(如：有机热载体泄漏)及其重要度和关键概率度。7.运用FLUENT对盘管式有机热载体炉的盘管不同流速和不同积碳层厚度情况下进行模拟研究并发现：当无积碳层时,盘管内有机热载体流速分布靠管壁两侧的有机热载体流速较慢,尤其是辐射管壁侧更为明显；有机热载体管内流速从管壁往管子中心逐渐增大,辐射段因为有辐射热侧的紊流层比保温侧的紊流层区域更大；靠近辐射管壁,层流与紊流交界处,有机热载体介质流速接近最大。当入口流速为1.0m/s时,随着导热油流速的降低,有机热载体处于劣化变质状态局部流动随着管径和流速的变化而呈现一定规律的变化,碳层越薄越有利于流场的均匀和液膜温度不超温。最后,在基于有机热载体炉积碳检测、安全评价和FLUENT流场模拟这三者综合构建的基础上,提出了有机热载体炉风险控制的管理模式和有机热载体炉安全立法的建议。更多还原

【Abstract】 Abstract:According to special equipment accident circumstance bulletin made by AQSIQ (Administration of Quality Supervision, Inspection and Quarantine) in recent five years, the number of boiler accidents still stay high in the case of less boilers than before even though the rate of annual accident in per million devices was declined. From the further analysis of reason of accidents, we can learn that:In small and medium industrial boilers, fire accidents of organic heat transfer heater occurred frequently. To solve the problem of carbon deposition in organic heat transfer heater and fire accidents, this paper relies on two projects:special fund for quality supervision research in the public interest(201210080)-Organic heat transfer heater safety assessment and research on the key technology of carbon content on-line detection, and Quality inspection administration of science and technology plan project (2013QK212)-Organic heat transfer heater based on Modeling and Simulation of flow field of FLUENT, on basis of Systematic retrieval and in-depth analysis of previous research achievements, writer adopts research measure that combines theoretical analyses with practical application, and has a deep discussion which aims at carbon deposition in organic heat transfer heater, flow field distribution of medium FLUENT and safety assessment. The study includes following mainly innovative achievements:1. Based on the statistics and analysis of fire accidents of organic heat transfer heater in the past ten years in China and the relevant papers about detecting and controlling technology of carbon deposition in organic heat transfer heater, paper expounds main cause of fire accidents of organic heat transfer heater and points out that the key factor is carbon deposition in organic heat transfer heater.2. According to physicochemical property of the medium of organic heat transfer and the particularity of organic heat transfer heater, paper analyses formation mechanism of carbon deposition in organic heat transfer heater as well as operation mechanism of organic heat transfer heater, and proposes a detection method to measure the thickness of carbon deposition layer which based on ultrasonic guided waves.3. The writer designed and assembled a detecting system of carbon deposition in organic heat transfer heater. It tested cutoff frequency, transition frequency and group velocity of ultrasonic guided waves and the relationship between these three characterization parameters and variation of thickness of carbon deposition layer. Result indicates that:It is feasible to use group velocity of ultrasonic guided waves and monotonicity law of the variation in thickness of carbon deposition layer to detect thickness of carbon deposition layer, and feasibility of this detecting way can be further demonstrated by fitting test of frequency dispersion curve of group velocity through blank pipe.4. In order to identify the modal type of ultrasonic guided waves in detecting system of carbon deposition, paper used time-frequency analysis method to do the comparative analysis of multiple modals in tube, and combined with fitting of the main energy scatter gram by the time-frequency analysis and the trend of Modal L (0,2) in frequency dispersion curve of numerical simulation to deduce modal of main wave mode is Modal L (0,2). The relative error between group velocity and testing group velocity by time-difference method is only from1.88%to3.48%.5.According to the detecting test of the simulate attachment of the carbon deposition of ultrasonic guided wave, paper finds out that:the detecting blindness of group velocity of Modal L (0,2), which is drove by the situation that the signal is5period, the frequency rate is500kHz and the peak is200mV, is that the arrangement distance of probe should be less than350mm, and the best detecting arrangement distance of the detecting probe of the ultrasonic guided waves of carbon deposition layer in organic heat transfer heater’s furnace tube is40cm. The SNR (Signal to Noise Ratio), time domain and the characteristics in frequency domain of the signal prove that the best period of detection is5periods; it can use epoxy resin to add hydrocarbon and to simulate carbon deposition layer, and it successfully drive the Modal L (0,2). When the distance of probe is 40cm and the detecting period takes5periods, paper use test to prove that group velocity of the Modal L (0,2) in carbon deposition pipe is less about7.65%than group velocity in the blank pipe, and this conclusion proves further that we could use changing relationship of group velocity in blank pipe and in carbon deposition pipe to detect carbon deposition layer in tube.6. The paper utilized the theory of ergonomics to the risk assessment of operation of organic heat transfer heater, and the paper got the conclusion that the weight of index of man-machine environment during the operation are:1.830,1.293and1.749, and by the comparison, paper finds out that the index of man and environment is0.5bigger than the weight of organic heat transfer heater itself. This result shows that the risk operation of organic heat transfer heater should put more attention to the people ware and environment management. Besides, from the statistics and the survey of fire accidents of organic heat transfer heater at home and abroad, the writer uses fishbone causal method analysis reason of accidents qualitatively, and finds out essential factor, the key factor (for example:the leak of organic heat transfer) with its importance and the key probabilistic by using the method of accident tree analysis and event tree analysis.7.The writer used FLUENT to do the simulate study of the coiled tube type of organic heat transfer heater with different flow velocities and different thickness of carbon deposition layer and finds out that:when there is no carbon deposition layer, the distribution of the flow velocity of organic heat transfer heater in the two side of tube wall is slower, particularly, the tube wall of radiant tube is more obvious; the flow velocity of organic heat transfer heater gradually increase from the tube wall to the center of the tube; in the radiant part, because the area of the turbulence level which has radiant heat is bigger than the level which has heat preservation, the flow velocity of the medium of organic heat transfer heater becomes the biggest when it comes close to the radiant tube wall and the junction of the laminar flow and the turbulence flow. When the inlet flow velocity comes to1.0m/s, with the lower flow velocity of conduction oil, organic heat transfer is in a degraded and deteriorated condition, and the local flow will have a disciplinary change with the change of pipe diameter and the flow velocity, the thinner of the carbon deposition layer, the better for the uniformity of flow field and the temperature of liquid membrane.The last but not the least, based on basement which built by the detection of carbon deposition in organic heat transfer heater, safety evaluation and the simulation of FLUENT flow velocity, the paper points out the management mode of the risk controlment of organic heat transfer heater and the advice of safety lawmaking.更多还原