干熄炉内传热和流体流动的数学模型

干熄焦工艺具有节能和环保双重效益，其基本原理是利用循环惰性气体冷却焦炭。根据多孔介质理论，采用非达西流和非局域热平衡方法，建立了干熄炉内流体流动和传热的数学模型，并采用基于非正交同位网格的SIMPLE方法求解对流扩散方程，通过数值求值，得到了干熄炉内气体速度，压降以及气体和焦炭的温度分布规律，计算结果表明熄焦过程解决焦炭温度偏析的关键是改善布料时焦炭粒度分布的均匀性。     

元胞自动机方法模拟干熄炉内焦炭颗粒的下降运动

干熄焦工艺中干熄炉内焦炭下降运动对熄焦质量起着至关重要的作用.利用元胞自动机方法(CA)的基本理论,采用能较好模拟各向同性现象的正三角形网格划分研究区域,邻居处理为Moore方式,模拟实验干熄炉内焦炭颗粒的运动,得到了下降料面曲线,并与实验结果进行了对比分析.研究表明,计算值和实验数据趋势一致,元胞自动机方法基本上能够准确地反映炉型变化和风帽对焦炭下降运动的影响,若能进一步考虑颗粒之间、颗粒与壁面之间的相互作用力,将有利于提高模拟的精度.     

燃烧反应干熄炉内传热模拟的浅析

建立了干熄炉内焦炭层床循环气体的传热模型,并耦合燃烧反应计算,分析了干熄炉冷却室内的温度变化,计算结果与实测数据基本一致。本文还进一步分析了化学反应活化能、风料比和燃烧反应对干熄炉内传热的影响,以期为干熄炉的优化设计提供一定参考。     

干熄炉料钟布料焦炭粒度分布的研究

对于干熄焦工艺,为了改善焦炭在干熄炉径向方向上的粒度偏析,采用料钟进行布料。采用实验和理论模拟相结合的分析方法,对布料焦炭在干熄炉预存段粒度偏析机理进行了研究。实验制作了冷态三维半圆料钟布料模型,考察了不同形状的料钟和不同的料线深度对焦炭粒度在干熄炉半径方向上分布的影响。所采用的理论模拟数学模型针对多尺度焦炭颗粒情况,用极少的参数来模拟半径平均尺度分布和每一种颗粒的半径堆积分布。研究结果表明,实验数据和数值分析结果吻合较好,相互验证了实验和理论模拟的正确性与可靠性。     

干熄炉内环形集气道压降及阻力系数的研究

借助CFD商业软件CFX数值模拟了干熄炉环形集气道内气体的湍流流动,并计算了各斜道区的压力分布。计算结果与现场实测数据吻合较好,验证了数值模拟的准确性。借鉴管路计算中局部阻力系数的概念,进一步计算了斜道区不同压砖情况下的压力损失系数。三种几何尺寸模型的计算结果表明,所得到的压力损失系数具有一定的通用性,可为干熄炉大型化环形集气道的设计提供参考。     

干熄炉风帽供风压力损失的数值研究

干法熄焦的核心技术是干熄炉内焦炭的冷却过程,而此过程是否能够顺利进行的关键之一是布风的好坏.干熄炉内的布风受很多因素的影响,如风帽的几何形状和安装的位置,环形烟道的几何形状等等.对实验干熄炉内的风帽供风采用CFX计算流体力学商业软件进行数值模拟,重点研究了三种风帽供风条件下的压力损失,并计算出了每种风帽的阻力系数;针对每一种风帽,考察了横向压砖和纵向压砖对供风的影响.研究结果表明:对各种风帽,压砖情况下的阻力系数大于不压砖的情况;椭圆风帽的阻力系数远远大于高风帽和低风帽的阻力系数;风帽出口局部地方存在负压倒吸现象.     

非正交曲线系下数值模拟及PDA测量模化炉内湍流流场

构造强守恒形式N－S离散方程组，耦合求解速度和压力修正方程，κ-ε双方程模型模拟湍流粘性。在方程离散中，采用以加权平均方法计算胞元界面上不连续的几何因子，以保持坐标转换的光滑性；以迭代方式考虑交错压力梯度项，并对常规形式压力方程结果进行二次修正。计算结果表明，针对局部非光滑且远离正交性的炉内网格体系，上述特殊数值方法对保证求解精度和收敛性具有关键作用。采用3D－PDA（三维激光多谱勒固粒运动分析仪）对670t/h四角切圆炉的1：20模型内冷态流场进行了测量。数值模拟结果与实验结果基本吻合。     

干熄炉内流动和传热过程数学模型的研究现状及其发展趋势

全面系统地综述了国内外有关干熄炉内流动和传热过程数学模型的研究现状及其发展趋势。其中，利用多孔介质理论建立的干熄炉内流动与传热过程数学模型能够比较真实地揭示干熄炉内气体流动和气固之间的换热规律，已成为干熄炉的优化设计及其最优控制的理论基础。     

炉内煤粉燃烧一维数学模型及其仿真

为了准确计算炉内煤粉的燃尽率,从研究煤粉粒子的燃烧机理入手,以炉膛内最复杂的燃烧器区域的煤粉燃烧过程为研究对象,通过合理简化煤粉中挥发分和焦炭的燃烧过程,建立了炉内煤粉燃烧沿高度方向上的一维宏观模型,在模型中考虑了煤粉燃烧过程中氧含量的变化,以单个煤粉颗粒燃烧的等密度模型为基础,通过多种煤粉粒径的燃烧过程反映煤粉燃烧的整体过程,推导出计算炉内煤粉燃尽率的显示公式,满足了实时仿真计算的要求。计算结果与实测数据和现有的文献相符,并对结果进行了分析。     

某型两级涡轮流场数值模拟

应用三维粘性流计算程序对某型两级涡轮进行了数值模拟,该程序采用具有TVD性质的三阶精度Godunov格式,湍流模型为B-L代数模型。计算中考虑了变比热的影响。结果分析表明,由于该涡轮是采用考虑损失的S2流面及单列粘性流计算设计的,没能很好地反映气流角的匹配问题,因此在第二级静叶中存在较大的正攻角,这使得第二级静叶采用后部加载叶型的作用不大,没有达到减少二次流损失的目的,因此,在气动设计中进行多级粘性流的匹配计算是必要的。     

Experimental and numerical investigations of coke descending behavior in a coke dry quenching cooling shaft

A viscous flow model based on the Navier–Stokes equation is developed to describe coke descending behavior in the 1/7-scaled-down experimental setup of an actual 75 t/h cooling shaft. It is found that the internal friction due to cokes viscosity significantly influences the descending behavior of cokes in the lower part of the shaft, while the external wall friction dominates the sluggish flow of the cokes in the shaft. An asymptotic friction coefficient expression is proposed for granular mixtures flowing along the shaft wall modified from normal wall tress, and the concept of bulk solid viscosity is introduced to describe the internal friction between coke particles. The results simulated by the present model are compared with those by the potential flow and the kinematic model without friction. The viscous flow model is quite good to simulate the bulk coke flow as the physically important frictions are engaged.     

Mathematical Model for Fluid Flow and Heat Transfer in the Cooling Shaft of Coke Dry Quenching Unit

IntroductionCoke Dry Quenching (CDQ) unit is a regenerativesystem whose thermal fUnchon is to cool off the red hotcoke with the circulahng gas and at the same time tOtransfer energy from the incandescent coke to watervapor fOr electricity generation. In comParison toconventional Coke Wet Quenching (CWQ) system, CDQenables not only energy savings, but also environmentalprotection. Further advantage is the imProved quality ofcoke. TherefOre, CDQ technology is becoming theconunon practi…     

Experimental study on the effects of blast‐cap configurations and charge patterns on coke descending in CDQ cooling shaft

The coke descending behavior in a CDQ cooling shaft is studied experimentally by means of a tracing method with a digital camera. For three different blast‐caps, the law of coke flow is studied under five conditions of coke charge. The experimental results show that, for the sake of the uniformity of the coke burden descending, a blast‐cap with elliptical cross‐section is a better choice than that with circular cross‐section regardless of high or low placement. A coke charge pattern with a flat top burden surface is preferable to that with peak‐valley surface, a double‐peak superior to a one‐peak. Trajectory and average velocity distribution of coke behavior are depend weakly on whether the coke is continuously fed or not as the discharging began. The blast‐caps have local effects on the descending coke and hardly affect whether the cokes flow smoothly or not in the case of coke burden with enough depth. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(6): 352– 358, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20212     

Numerical study on pressure drop factor in the vent-cap of CDQ shaft

In CDQ （Coke Dry Quenching） shaft, the vent-cap with complex structure is installed in the cone-shaped funnel under the cooling chamber. It acts to introduce cooling gas and support the descending coke in the chamber. The designing and installation of vent-cap aim to get relatively uniform gas distribution, to reduce the temperature fluctuation of cokes at outlet and realize stable operation of CDQ apparatus. In this paper, the turbulent flow of gas in vent-cap of 1：7 scale CDQ experimental shaft is numerically simulated by using CFD （Computational Fluid Dynamics） software, CFX. The velocity field, the outlet flux distribution and the pressure drop factor of each outlet under three kinds of vent-cap （called high vent-cap, low vent-cap and elliptic vent-cap） are analysed and compared. The results turn out that the pressure drop factor of elliptic vent-cap is larger than the other two vent-caps, and that the pressure drop factors of high vent-cap and low vent-cap almost have the same value. While for a specified vent-cap, the pressure drop factor with pressing brick is larger than that without pressing brick. The work in this paper is valuable for the designing of vent-cap for large-scale CDQ shaft.     

Co-Carbonization of Two Anthracites with a Fat Coal or Two Pitches

The blends of two anthracite powders (YQ and JC) with a fat coal (C4) or a petroleum pitch (PP) or a coal tar pitch (CTP) in different proportions were co-carbonized at 3°C/min up to 1000°C in an experimental 1 Kg coke oven. Coke yield, coke particulate size, coke micro-strength and coke cracking strength were measured respectively. Coke optical textures were watched under a microscope. The results show that as anthracite proportion increases, coke yields of all blends improve; > 0.8 mm lump coke yields of blends with CTP or PP decline slightly, blends with C4 drop heavily; coke micro-strengths do not change sharply, and coke cracking strength of blends with C4 or PP decrease more than blends with CTP. C4 produces fine-grained mosaics, and two anthracites are mainly fusinite and fragments, PP is coarse-grained mosaics, and CTP is chiefly flow or domain textures. Independent optical textures were observed in cokes. There exist evident borders between the two contact optical textures which were produced by different components, and a few phenomena that domain or flow textures penetrating into fusinite appeared in the blends. It seems that CTP is the best adhesives for blending with anthracites for producing high quality cokes.     

Minerals and iron-making reactions in blast furnaces

Coke is central to blast furnace operation, but because it is the most expensive raw material used, there is continuing pressure to minimize its use. Consequently, it has become increasingly pertinent to measure and predict the factors affecting coke performance more accurately. Coke performance is affected both by its properties and blast furnace operation. Recently, the importance of the minerals in coke in determining its performance in the blast furnace has been recognized. Minerals in coke influence its reaction with gas, metal and slag phases. This paper reviews coke behavior in an operating blast furnace with the main emphasis being on the role of its inherent mineral matter. Various techniques including advanced approaches such as scanning electron microscopy (SEM) and quantitative X-ray diffraction (XRD) have been used to identify and quantify coke minerals. Fundamental studies based on bench-scale reactors have highlighted the role of various mineral phases on the kinetics of gasification, hot-metal carburization and slag reactions. Because coke reaction rates are influenced by the constituent mineral phases differently, conventional ash analysis is not sufficient to determine the true impact of coke minerals on coke reactivity. The dominant catalytic phases of coke minerals can be identified and related to coke gasification with CO₂ at low temperatures. The kinetics of hot-metal carburization by coke and its temperature dependence is influenced by the melting behavior of minerals. Coke–slag reaction rates are largely influenced by total mineral matter content as well as composition. Coke changes its properties during descent through an experimental blast furnace (EBF) and some of these changes are presented. The increase in the ordering of the carbon in the coke as it descends the EBF can be related to increases in coke ordering in a bench-scale reactor, indicating that order in a particular coke may serve as a thermometer of its maximum exposure temperature. Moreover, coke fines emissions are influenced by the extent of graphitization in industrial blast furnaces. In contrast, coke reactivity in an operating blast furnace is influenced by recirculating alkalis as well as inherent mineral matter. Mineral phases of industrial cokes were found to be changed after CO₂ gasification with increasing reaction temperatures. Coke quality needs in current and emerging blast furnace process innovations are discussed to highlight that existing tests are not sufficient. A comprehensive coke quality index is required, particularly one that incorporates the heterogeneity of coke minerals, in order to make a reliable assessment of the impact of cokes on iron-making reactions.     

凝汽器水侧流动的三维数值模拟

运用计算流体力学的方法,采用多孔介质模型对凝汽器水侧流场进行了数值模拟.从计算所得三维流场可清楚地掌握影响凝汽器工作的重要因素：该凝汽器进口水室漩涡的存在使流动阻力增加,流动恶化;高速流体集中于水室中心区域,会影响换热器的换热性能.其整体阻力特性与试验数据吻合较好,表明该模型和计算方法正确.解决了凝汽器水侧数值计算建模的困难和网格数量问题,为动力装置冷却水系统整体的数值模拟提供基础.图6参5     

Structures and electrochemical performances of pyrolized carbons from graphite oxides for electric double-layer capacitor

The structural features and the electrochemical performances of pyrolized needle cokes from oxidized cokes are examined and compared with those of KOH-activated needle coke. The structure of needle coke is changed to a single phase of graphite oxide after oxidation treatment with an acidic solution having an NaClO₃/needle coke composition ratio of above 7.5, and the inter-layer distance of the oxidized needle coke is expanded to 6.9 Å with increasing oxygen content. After heating at 200 °C, the oxidized needle coke is reduced to a graphite structure with an inter-layer distance of 3.6 Å. By contrast, a change in the inter-layer distance in KOH-activated needle coke is not observed.