【作者】 杨爱民；

【导师】 张玉柱；

【作者基本信息】 燕山大学 ， 机械设计及理论， 2015， 博士

【摘要】 钢铁工业生产节能和矿物资源的高质高效利用是目前研究的热点,作为炼铁过程的主要副产品,高炉熔渣成纤是资源深度利用的一个重要途径,调质是成纤前的必备环节,传热直接影响调质剂的加入量和熔渣的成纤性能,传统的作法全凭经典理论和经验,特别是利用二阶偏微分方程研究黏弹性的熔渣传热问题时难以精确的刻画和模拟,本文创造性的引入分数阶微分算子理论研究熔渣成纤过程的微观传热机理,达到“一叶以知秋”的目的,以对实践或生产提供有意义的支撑。针对调质剂在渣液中的传热问题,首先分五个阶段对从接触液面到完全浸入的传热规律进行了探讨,然后以调质剂在高炉熔渣熔化过程中显示的扩散性质为基础,结合传导传热和辐射传热两种方式,首次引入局部分数阶微分算子,建立了调质剂浸入熔渣过程的瞬态分数阶传热模型,用构建的局部分数阶杨-拉普拉斯变换和傅里叶变换两种算法进行了求解,通过与实际实验数据的比较,得到了满足要求的最佳分层维数和熔化时间。为设计调质炉熔池尺寸和确定调质剂颗粒的范围提供了依据。针对调质剂在渣液中的均热问题,从外部加热和化学反应两个方面进行了分析。考虑外部加热时,以能量守恒定律为基础,建立了调质剂熔化前固体内部的局部分数阶均热模型,并用设计的局部分数阶杨-傅里叶变换算法进行了求解,计算得到了不同半径下的调质剂颗粒的物理均热时间,并通过与实验数据进行比较,得到了最佳分层维数。考虑化学反应时,通过对熔渣中的反应进行综合评判,给出了主要的反应方程,并利用未反应模型和均质过程中的扩散模型,求解出了均热过程中时间与温度的直接关系。为调质剂的加入速度、设备的选型和功率的设置提供了理论参考。针对动态液渣在倾倒后的流股形式的传热问题,分别从液芯到流股边界、流股边界到外界空气两个方面进行了分析。建立模型求解了对流换热量、辐射散热量、层流状态下渣液半径对传热的影响规律和流柱热量的总散失比例,得到了最优流股半径、最大流股高度和过余温度。针对动态渣液在渣槽中运动时的传热问题,从辐射和传导传热角度考虑,建立模型并得出了槽中熔渣与空气间的辐射散热流量、渣槽与熔渣之间的导热量,给出了熔渣在渣槽中热剩余量的计算方程,并得到热剩余量与熔渣在渣槽中的深度成正比关系的结论。计算结果与实验测试数据进行了对比,证明了方法的可靠性。为确定最佳成纤的出渣温度、渣流的大小等方面奠定了基础。针对渣液喷吹纤维化时的传热问题,基于流动及喷吹过程的渣液破碎机理的基础,通过改变雷诺数和卡门涡漩的流动状态,建立了散热模型,分别给出了渣液细线、渣液成形线上的散热规律。基于对流传热理论,基于局部分数阶微分算子,建立了渣液液滴的局部分数阶散热模型,并建立局部分数阶Adomian算法进行了求解。为确定喷吹口半径、分析成纤机理等方面提供了前期准备。总之,通过上述对高炉熔渣直接纤维化的调质、均质、倾倒、渣槽流动、喷吹五个过程的传热规律的研究,将为其工业化过程中的热量补偿和潜热利用提供支撑,具有一定的理论意义和实际价值。更多还原

【Abstract】 More attentions are currently paid to researches on how to achieve energy-saving production activities in iron & steel industry and utilize mineral resources in a high-quality and efficient manner. One of critical utilizing approaches is how to fully fiberize blast furnace slag, the main by-product of blooming process. Quenching & tempering is an essential part before fibering, and heat transfer directly affects addition of quenching & tempering agent and fibering performance of blast furnace slag. Traditional approach fully depends on classical theory and experience, especially it is difficult to accurately describe and simulate heat transfer of viscoelastic slag with second order partial differential equations. This paper creatively introduces fractional differential operator theory into research on micro heat transfer mechanism of slag fiber-forming process, further concludes general rules with a specific case, in order to provide meaningful support for practices or production.In order to investigate heat transfer rule of quenching & tempering agent in slag solution, the paper establishes invasive fractional differential heat transfer model for invasion of quenching & tempering agent into slag, according to diffusion properties during blast furnace slag melting process, by combining two heat transfer approaches: conduction heat transfer and radiation heat transfer, and introducing local fractional differential operator; it further concludes functional relations between slag temperature, height from quenching & tempering agent center to liquid surface, and melting time, with Young-Laplace transform. In order to analyze the melting process of quenching & tempering agent more effectively, from five stages herein the paper discusses heat transfer law of quenching & tempering agent during the process from contact with liquid surface to full immersion, and the calculated results are basically consistent with observational data from laboratory, thereby verifying the rationality of the heat transfer rule.For the purpose of studying the soaking rule of quenching & tempering agent in liquid slag, the paper makes analysis from the views of external heating only or chemical reactions only. Under the conditions where external heating is considered only, fractional soaking models for the temperature field of continuum is proposed, on basis of the energy conservation law, and then soaking time is calculated with Yang-Fourier successive approximation method. Under the conditions where chemical reaction is considered only, the paper comprehensively evaluates slag reaction, proposes main reaction equation, and establishes soaking physical model with unreacted model and diffusion model of homogeneous process, also further solves the direct relations between time and temperature during the soaking process. The calculated soaking time is basically consistent with repeated experimental data from laboratory, thus verifying the rationality of the soaking rule.The paper analyzes from the two processes: from liquid core to stream boundary, and from stream boundary to external air, respectively, in order to investigate the heat radiating rule of dumped liquid slag during free falling process. A model is established to solve convection heat exchange, radiation heat loss, influence of liquid slag radius on heat transfer under laminar flow conditions, as well as total loss ratio of stream column, thereby to conclude the optimal stream radius in laboratory experiments. The calculated total loss ratio is basically consistent with the data measured in laboratory, thus verifying the rationality of the heat radiating rule. For the purpose of investigating the heat radiating rule of liquid slag during its movement in slag tank, from the view of radiation heat transfer and conduction heat transfer, the paper establishes models to solve radiation heat transfer heat flux between slag and air, heat conduction flux between slag and tank, concludes the calculation equation of remaining heat of slag in tank, and concludes that the remaining heat is directly proportional to the depth of slag in tank. The calculated remaining heat of tank is basically consistent with the data observed in laboratory, thus verifying the rationality of the heat radiating rule.In order to analyze the heat transfer and radiating rules of slag during injection and fibering process, a heat radiating model is established, according to research on liquid slag crushing mechanism during injection and flowing process, by modifying the flow conditions of Reynolds number and Karman Vortex Street, thus to propose radiating rules of liquid slag thin line and liquid slag forming line. On basis of the convective heat transfer theory, the paper establishes a partial fractional radiating model of liquid slag pellets. Regarding liquid fiber’s cooling, it proposes liquid cooling law under gas- liquid heat exchange control; as well as solid phase cooling law under gas- solid heat exchange control; also the temperature field of cooling process is simulated. The data errors, between fiber coagulation time, heat loss after injection and fibering, and those results from experimental observation, are within the acceptable range, thereby verifying the rationality of the heat transfer and radiating rules.In short, the paper provides support for heat compensation and waste heat recovery in industrialization process, by research on heat transfer law during quenching & tempering, soaking, dumping, tank flowing, and injection for direct fibering of blast furnace slag, with a certain theoretical significance and practical value.更多还原